Outcomes of Descemet stripping automated endothelial keratoplasty (DSAEK) for corneal endothelial disorders

(1)

OUTCOMES OF DESCEMET'S STRIPPING AUTOMATED ENDOTHELIAL KERATOPLASTY

(DSAEK) FOR CORNEAL ENDOTHELIAL DISORDERS

Dissertation submitted to The Tamil Nadu Dr. M.G.R. Medical University in partial fulfilment of the requirements for the degree of

MS Ophthalmology BRANCH - III OPHTHALMOLOGY

THE TAMIL NADU

DR. M.G.R. MEDICAL UNIVERSITY CHENNAI –600032

MAY 2018

CERTIFICATE

(2)

This is to certify that this dissertation entitled "OUTCOMES OF DESCEMET'S STRIPPING AUTOMATED ENDOTHELIAL KERATOPLASTY (DSAEK) FOR CORNEAL ENDOTHELIAL DISORDERS" is a bonafide work done by Dr.PRIYANKAR under our guidance and supervision in the cornea department of Aravind Eye Hospital and Post Graduate Institute of Ophthalmology, Madurai during the period of her post graduate training in Ophthalmology for June 2015 -May 2018.

DECLARATION

Dr.N.VenkateshPrajna DO, DNB, FRCOphth., Prof. & Head of the Department,

Aravind Eye Hospital &

PG Institute of Ophthalmology, Madurai.

Guide

Dr.N.VenkateshPrajna DO, DNB, FRCOphth., Prof. & Head of the Department,

Cornea services

Dr.R.Rathinam, DO, DNB, Ph.D., Principal,

(3)

I, Dr.PRIYANKAR hereby declarethat this dissertation entitled,

"OUTCOMES OF DESCEMET'S STRIPPING AUTOMATED ENDOTHELIAL KERATOPLASTY (DSAEK) FOR CORNEAL ENDOTHELIAL DISORDERS" is being submitted in partial fulfilment for the award of M.S. Ophthalmology (Branch III) Degree by The Tamilnadu Dr. MGR Medical university in the examination to be held in May 2018.I declare that this dissertation is my original work and has not formed the basis for the award of any other degree or diploma awarded to me previously.

Dr.PRIYANKA R, Aravind eye hospital &

PG Institute of Ophthalmology, Madurai, Tamilnadu.

(4)

ACKNOWLEDGEMENT

First and foremost, I would like to thank God. Without Him, I can do nothing.

I take this opportunity to pay my respect and homage to Dr.G.Venkatasamy, our founder and visionary, whose dynamism had led Aravind against all odd to its high scale of achievement.

I would like to thank Dr. N. VenkateshPrajna for allowing me to work on this study, guiding me at every step and for being a constant source of motivation and encouragement, which ultimately structured my thesis.

I am very grateful to Dr.R.Ravindran, chairman of Aravind Eye Care System for having created the environment enriched with all the facilities for learning and gaining knowledge. I am privileged to have on my side Dr.P.Namperumalamy,chairman emeritus director of research, Dr.G.Natchiar, Director emeritus (human resource department), Dr.M.Srinivasan, director emeritus and other scholars of ophthalmology at Aravind Eye Care System.

My special thanks to Dr. NilamGohil, Dr. KishanPrajapathi and Dr.R.Naveen for helping me with the methodology and encouraging me

(5)

to progress further. I am grateful to the entire Cornea department for their help and support.

I thank Mrs. Iswarya, biostatistician for her invaluable help in the statistical analysis of the study. I thank all the faculties of the library who rendered their help during the study.

I would fail in my duty if I did not thank the countless patients who have been the learning ground for my study and my residency.

And finally I would like to thank my family and friends for their constant support and unfailing love towards me.

Dr.Priyanka R.

(6)

PART I

(8)

1.1 INTRODUCTION

The goal of vision 2020 “Right to Sight” is to eliminate avoidable blindness by the year 2020. Despite increase in global population, the numbers who are blind remained at similar level, suggesting a reduction in the prevalence of blindness and so indicating progress towards the goal of vision 2020.

However, blindness continues to be one of the major public health problems in developing countries. According to World health organization (WHO), corneal diseases are the major cause of vision loss and blindness in the world after cataract and glaucoma.¹

In India it is estimated that there are approximately 6.8 million people who have vision <6/60 in one eye due to corneal disease, of these about one million have bilateral involvement.^2,3 It is expected that the number of individuals with unilateral corneal blindness in India will increase to 10.6 million by 2020.⁴ According to National program for control of blindness (NPCB) there are currently 120,000 corneal blind people in India. According to this estimate there is addition of 25,000 – 30,000 corneal blindness cases in the country. 90% of the global causes of ocular trauma and corneal ulceration leading to corneal blindness occur in developing countries.⁵

While clearly the solution to corneal blindness lies on preventive strategies, there are still a million of people who are currently blind

(9)

from a wide variety of degenerative, dystrophic and inflammatory corneal disorders and cornea remains the most commonly transplanted tissue worldwide, with an estimated 100,000 corneal transplant performed annually. It is inevitable that eye bank worldwide cannot match the demand, thus resulting in long waiting list for corneal transplantation in majority of developing countries, especially in Asia.

Figure1: Global causes of blindness as percentage of global blindness in 2010. AMD, age-related macular degeneration; co, corneal opacity; DR, diabetic retinopathy; RE, Uncorrected refractive errors⁶

Corneal diseases can be divided into two major categories depending on anatomical extent of involvement of the cornea by the disease process.

(10)

1. Those affecting the anterior layers of the cornea (epithelium and the stroma)

2. Those affecting the posterior layers of the cornea (endothelium)

First category includes diseases like anterior stromal dystrophy, spheroidal degeneration, keratoconus, anterior stromal scars and the tumors such as dermoids. In the second category endothelial dystrophy have major contribution besides endothelial decompensation following intraocular surgery mainly cataract surgery.

Corneal transplantation remains the main method for visual rehabilitation once the disease has affected corneal clarity, but it is dependent on the availability of the corneal donor tissue, which is the major limiting factor in developing countries. Till recently penetrating keratoplasty was the only modality of corneal transplantation followed all over the world.

The concept of lamellar keratoplasty is that of targeted replacement of diseased corneal tissue while retaining normal cornea. Replacing either anterior stroma (anterior lamellar keratoplasty) or replacement of deep stromal and endothelial layers (posterior lamellar keratoplasty or endothelial keratoplasty). Despite the distinct advantage of lamellar keratoplasty surgery in reducing the risks of graft rejection and intraocular complications, penetrating keratoplasty remain the most common procedure, largely because this has been the traditional form of

(11)

transplantation surgery taught and performed in recent decades and also partially because lamellar surgery is more technically demanding and time consuming and interface irregularity arising from manual lamellar dissection often results in suboptimal visual outcomes unable to match penetrating keratoplasty visual quality.

Lamellar keratoplasty has however, reemerged in the last decade as a principle alternative to conventional penetrating keratoplasty surgery for several reasons. Recent improvement in the surgical technique and advances in instrumentation have contributed to improved visual quality with lamellar keratoplasty surgery and studies now confirm that visual outcomes of lamellar keratoplasty are able to match those of penetrating keratoplasty surgery.^7-9 The advent of microkeratome assisted lamellar keratoplasty surgery is one such technology that has allowed this to occur. More recently, the development of new posterior lamellar keratoplasty procedure like DLEK, DSAEK and DMEK has fuelled even greater interest with the advent of procedures such as deep lamellar endothelial keratoplasty (DLEK) and Descemet's-stripping automated endothelial keratoplasty(DSAEK).

(12)

Different types of keratoplasties (A) The cornea consist of five main layers:

the superficial multilayered epithelial cell layer, Bowman’s layer, the corneal stromal layer, Descemet’s Membrane, and most posteriorly endothelial cell monolayer. (B) Penetrating keratoplasty (C)Anterior lamellar keratoplasty(D) Deep anterior lamellar keratoplasty (E)Descemet’s stripping automated endothelial keratoplasty (F) Descemet’s membrane endothelial keratoplasty

(13)

1.2 CHALLENGES WITH CORNEAL TRANSPLANTATION

Many of the corneal diseases can be corrected by corneal transplantation, but the success of corneal grafting in restoring vision depends on a complex set of factors in a developing country like India.

Hospital based data on survival of corneal graft done at a reputed eye institute in India showed that the 5 year survival rate for corneal transplant performed for the first time was 46.5% for all pathologies causing corneal blindness considered together.¹⁰ In addition, the patient belonging to a lower socio economic status had 28% higher risk of graft failure. The other major issue is availability of adequate number of good quality of donor cornea for corneal grafting from reliable eye banking facilities. The surgical costs of treating corneal blindness are generally higher than majority of population in a developing country can afford, because of issues like therapeutic costs, the longer duration of treatment involving frequent follow up, time lost from work and various other indirect cost.

Although these difficulties do exists even today, the establishment of many new eye banks and more trained cornea surgeons available in different parts of the country the scenario is certainly looking up. The concept of lamellar keratoplasty has helped us to tackle the crisis of shortage of donor tissue up to certain extent in the following ways

(14)

1. A single cornea tissue can be used for two recipients (anterior stromal part for DALK and endothelial part for DSAEK).

2. Cornea that might otherwise have been discarded may be used after photorefractive keratectomy.

3. Lamellar keratoplasty procedure requires lesser duration and frequency of follow up, the loss from work can be reduced.

4. Early visual rehabilitation following lamellar keratoplasty has decreased the number of days of absence from work which indirectly affects socio economic status.

(15)

1.3 EVOLUTION OF POSTERIOR LAMELLAR KERATOPLASTY

Endothelial keratoplasty has transformed the field of corneal transplantation over the past decade. Surgeons have moved away from penetrating keratoplasty as the standard therapy for corneal edema to the selective replacement of defective endothelium through evolving endothelial keratoplasty techniques.

The concept of selective tissue replacement of posterior cornea has been around for many decades. The first successful lamellar keratoplasty reported was that of Charles Tillet in 1956. Tillet’s procedure, performed without the benefit of surgical microscope, involved a large stromal pocket, partial anterior stromal flap and manual excision of the host posterior cornea. The donor replacement tissue of the posterior stroma and healthy endothelium was then sutured to the overlying flap of recipient tissue and the partial flap was sutured as well. Although Tillet’s endothelial keratoplasty was successful, no further cases were reported for decades.¹¹

In 1990 endothelial keratoplasty was again reinvestigated, revised and reintroduced by Melles whose experiments with eye bank, cadaver eyes and then with animal eyes brought endothelial keratoplasty into modern era. Melles breakthrough idea was that an 8.0mm donor tissue could be introduced through a 8mm limbal incision and then self- adherence without sutures to the overlying host tissue. This was

(16)

facilitated by the placement of an air bubble into the anterior chamber to support the tissue. With the limbal incision and no surface sutures, the PLK of Melles allowed fast recovery of vision with normal topography and greater tectonic strength than penetrating keratoplasty.^12,13

In 1999, Terry simplified the posterior lamellar keretoplasty technique with the introduction of an artificial anterior chamber that allowed the use of donor corneo-sceleral tissue rather than whole globe for donor lenticule creation and the safe use of cohesive viscoelastic for ease of host tissue resection and greater donor endothelial protection.

Terry named the modified procedure deep lamellar endothelial keratoplasty (DLEK). Despite these improvements neither PLK nor DLEK became popular because both required extensive manual lamellar dissection for both posterior host tissue resection and for the creation of the donor lenticule.^14-16

In 2004, Melles introduced a modification which made PLK easier and faster. His “descemetorrhexis” allowed simple stripping of descemet’s membrane from the host bed followed by insertion of donor tissue.¹⁷ Further work and modification of the updated Melles endothelial keratoplasty surgery was done by Price and he named the procedure descemet’s stripping endothelial keratoplasty (DSEK).¹⁸ The remaining obstacle to general acceptance of DSEK as a preferred alternative to penetrating keratoplasty was the manual preparation of the donor tissue.

(17)

Gorovoy popularized the use of the microkeratome for automated deep resection of the donor tissue and again the name was changed to descemet’s stripping automated endothelial keratoplasty (DSAEK). With elimination of all manual lamellar dissections, the DSAEK procedure quickly gained acceptance as a legitimate alternative to penetrating keratoplasty.¹⁹

(18)

1.4 DESCEMET’S STRIPPING AUTOMATED ENDOTHELIAL KERATOPLASTY (DSAEK)

Descemet’s stripping automated endothelial keratoplasty (DSAEK) is the procedure of choice for corneal endothelial dysfunction. DSAEK has many advantages over penetrating keratoplasty including less ocular surface complications and structural weakness, minimizing wound dehiscence and induced astigmatism. Additionally, DSAEK provides faster visual rehabilitation and avoids suture related complications. Although many advantages of DSAEK exists, a learning curve remains due to the challenges of atraumatic donor preparation, graft insertion, air bubble manipulation and prevention of donor dislocation.

The primary complication after DSAEK is donor detachment and dislocation. Dislocation rates vary by surgeons experience and technique with rates ranging from 4% – 50%.^21-23 Techniques such as prolonged full chamber air bubble, stab incision, surface sweeping to reduce interface fluid, peripheral scraping and longer postoperative supine positioning have been suggested to decrease dislocation rates.^22,23

INDICATIONS OF DSAEK 1. Endothelial Dystrophies

a. Fuch’s

b. CHED

(19)

2. Bullous Keratopathy

a. Pseudophakic

b. Aphakic

c. Phakic

3. Endothelial Failure:

Post trauma, Post surgery, Glaucoma

4. Failed PKP

5. ICE Syndrome

CONTRAINDICATIONS OF DSAEK

1. Stromal opacity or scarring that limits visual outcome

2. Keratoconus, ectasia

3. Hypotony / Pre-phthisical eye

Added care to be taken in eyes with:

• Shallow Anterior chamber

• Anterior chamber IOL

• Glaucoma tubes

• Iris abnormalities

(20)

SURGICAL TECHNIQUES OF DSAEK DONOR TISSUE PREPARATION

Good quality donor tissue with endothelial cell count of at least 2000 cell / mm² is required. The donor tissue can be prepared intra- operatively or before the surgery. When prepared before the surgery it is termed as “precut” tissue. The preparation of precut tissue can be accomplished in the operating theater or in the eye bank. In many parts of the world the eye banks are supplying the precut tissue for the DSAEK. After preparation of the tissue with a microkeratome at the eye bank, the donor cornea is transferred in the transport medium and sent to the surgeon.^24-27

Donor tissue is prepared using the Moria automated lamellar therapeutic keratoplasty (ALTK) system using a 300µ head. Donor corneo-scleral tissue is placed in the artificial anterior chamber (AAC).

Microkeratome is then used to remove the anterior corneal disc of 300µ thickness. The excised anterior stromal disc is assessed for completeness.

The posterior corneal button removed from the AAC and positioned centrally within a teflon block. The donor button is trephined using 7.75 to 8.5 mm diameter trephine (depending on the diameter of the recipient cornea).

(21)

The Terry Unfolding Technique

The Terry technique involves the creation of a 5-mm scleral tunnel. Descemet’s membrane is stripped using a reverse Terry-Sinskey hook under Healon. A Terry scraper is used to roughen the stromal fibers in the peripheral 1 to 2mm of the stripped bed. The Healon is then evacuated. The precut donor epithelium is marked centrally and along the microkeratome surface cut. The tissue is trephinated epithelial- side down while using the markings for centration under a microscope. A thin line of Healon is applied over the endothelium. The tissue is folded in a 40/60 underfolded ‘‘taco.’’(28,29) Charlie II noncoapting insertion forceps are used to insert the graft into the AC, with the 60% side facing anteriorly. Balanced salt solution is injected to partially unfold the graft by deepening the chamber, followed by slow air injection beneath the endothelium to complete unfolding.

The Cindy Sweeper externally compresses the cornea with the AC full of air to center the graft and milk fluid out of the interface. The graft sits over a large AC air fill for 10 minutes while the wound is sutured and 1% cyclopentolate and 2.5% phenylephrine drops are applied.

The air is exchanged for balanced salt solution to remove any air from under the iris to prevent pupillary block. Air is reinjected to obtain a 5 to 9 mm diameter bubble that moves freely beneath the donor. The patient maintains supine positioning that day.

(22)

Insertion Techniques

There has been much debate over the best way to insert a DSAEK graft. Techniques include a forceps delivery, a suture ‘‘pull- through’’ delivery, or the use of an insertion device. The Terry unfolding technique described above uses noncoapting forceps to avoid endothelial cell loss (ECL) through crush-related injury. Other techniques have been described such as pulling folded tissue across the AC via suture attached to the graft edge.^30,31 The Busin glide involves introducing a DSAEK graft from a rolled configuration either adjacent to or into the incision and pulling it across the AC.

The Tan Endoglide is similar to a closed-end Busin Glide and also contains a posterior lip preventing iris prolapse during cross-chamber pull- through insertion. Yet another method involves sliding the graft over a Sheets glide covered with viscoelastic and then pushing it into the AC with a needle³² or Sinskey hook,³³ or pulling it across the AC with forceps.³⁴ The Neusidl Corneal Inserter (NCI) is an insertion device designed to inject a DSAEK graft while avoiding tissue overlap and viscoelastic usage. The NCI contains a platform where tissue is loaded, which then retracts, rolling the tissue into a tube. The tube incorporates an irrigation system to maintain the AC during tissue insertion through a 5.25-mm wound. The EndoSerter is another platform injector system. It rolls the graft with overlap to deliver it through a 4-mm wound.

(23)

Factors Promoting DSAEK Graft Adherence

Price and Price ³⁵ introduced the concept of removing interface fluid with external compression and venting incisions to promote graft adherence. Terry incorporated external compression and introduced peripheral stromal scraping to further promote adherence. The authors consider venting incisions extraneous as they do not evacuate interface fluid any better than compression, and disadvantageous as these induce anterior stromal scars that can be associated with visual distortion, glare, and epithelial ingrowth.³⁶ Bhogal and colleagues confirmed in laboratory experiments that both the complete removal of interface fluid and stromal roughening improved graft adhesion. They also concluded that the duration of air bubble tamponade and venting incisions (when sufficiently opened) all independently decreased interface fluid, whereas the AC tamponade pressure did not affect interface fluid or adhesion.³⁷

Lens Extraction

Cataract surgery should be attempted alone if endothelial compromise and corneal guttata are minimal in the setting of Fuchs dystrophy, as it is possible that this alone can significantly improve vision. In the presence of endothelial dysfunction and cataract, lens extraction is indicated in addition to DSAEK. Cataract surgery may be performed either before, concurrently, or after DSAEK.³⁸ Combined cataract and DSAEK surgery can be performed (the ‘‘DSAEK triple

(24)

procedure’’) and has been shown as effective as post-DSAEK cataract surgery, without increased risk of complications.³⁹ Triple procedures tend to be patient preferred, more cost effective, and avoid the added risks associated with two trips to the operating room. Cataract surgery may be performed after DSAEK when there is poor visualization of the anterior segment. This carries a risk of damage to the graft, but can result in more precise refractive outcomes. In the absence of cataract, ‘‘phakic DSAEK’’ may be performed. One study shows that patients younger than 50 run a 7% risk of cataract surgery 3 years after phakic DSAEK, whereas those older than 50 have a much higher surgical risk In the same time period (55%).^38,41 Another factor to consider is that patients with shallow ACs are at higher risk of postoperative cataract after phakic DSAEK.^38,42

COMPLICATIONS OF DSAEK

INTRA-OPERATIVE COMPLICATIONS 1. Going full thickness while dissection

2. Damage to endothelium

3. Eccentric trephination

4. Retained descemet’s membrane in the host

(25)

POST-OPERATIVE COMPLICATIONS Posterior graft dislocation

A dislocation represents lack of adherence of the donor posterior lenticule to the recipient stroma, and it is typically evident within the initial week, although it can occur later.^42,43 Dislocations may represent either fluid in the interface of an otherwise well-positioned graft or complete dislocation into the anterior chamber. This requires intracameral air injection and repositioning known as “Rebubbling.” Risk factors for graft dislocation are prior glaucoma surgery and Hypotony. Other factors contributing to dislocation are postoperative eye rubbing and poor positioning.

Primary graft failure

Primary graft failure deserves special mention because as a term, it is used by corneal surgeons and the eye banking community to characterize the clinical situation in which a corneal graft does not clear as expected after surgery. Corneal grafts that have not cleared after 2 months are classified as primary graft failures. Primary graft failures do not represent a rejection, but rather a lack of endothelial function from unhealthy tissue, unhealthy recipient circumstances (blood, interface foreign bodies, infection, flat chamber), or surgical technique. Primary graft failure in DSAEK also can occur because of primary donor endothelial failure, but it more often is considered because of excessive

(26)

endothelial cell trauma and subsequent damage during the surgical procedure. Poor surgical technique has been linked to primary graft failure in DSAEK, with surgeon inexperience and related excessive iatrogenic intraoperative donor endothelial trauma as a main factor. In fact, some studies refer this as iatrogenic primary graft failure.

Endothelial rejection

Endothelial rejection develops in grafts that were previously clear after DSAEK surgery, unlike primary graft failure. They represent the host’s immunologic reaction directed against the foreign antigen of the donor corneal tissue. This can be reversed with topical or oral immunosuppression. Thus long term continuation of low dose steroid can prevent rejection.

Iatrogenic glaucoma

Glaucoma after DSAEK occurred by two mechanisms. The first mechanism involved a pupil block induced from the air bubble in the immediate postoperative period. The air bubble prevented flow of aqueous into the anterior chamber and created obstruction of the trabecular meshwork similar to acute angle-closure glaucoma. The second mechanism was delayed glaucoma induced by topical corticosteroids.

Management of the glaucomatous cases involved topical or oral intraocular pressure lowering medications, release of air from a paracentesis site, or both, without reported sight threatening complications.

(27)

Other complications

Other complications after DSAEK include infectious keratitis, endophthalmitis, epithelial ingrowth into the interface between recipient and donor stroma. Dislocation of DSAEK lenticule into the posterior segment is another rare adverse outcome.

Endothelial cell loss

Endothelial cell loss is a marker of corneal graft health that predicts the long term graft survival. Although endothelial cell loss is not a complication, acceleration of cell loss can lead to earlier onset of late endothelial failure and ultimate graft decompensation

Endothelial cell loss at 6 months ranged from 25% to 54%, with an average of 37% cell loss. Endothelial cell loss at 1 year ranged from 24% to 61%, with an average of 41% cell loss. Price and Price described cell loss in a longitudinal analysis of a subset of 34 patients that showed 34% cell loss at 6 months, 36% at 12 months, and 41% at 24 months.

Visual Outcomes

Benefits of DSAEK

The central benefit of DSAEK surgery over PK for patients with endothelial failure is faster visual recovery. Generally, patients’ vision improves dramatically 4 to 6 weeks after DSAEK, as compared with

(28)

months to years after PK. This difference is mostly due to the preservation of the anterior corneal curvature with DSAEK, allowing for markedly less postoperative astigmatism. Moreover, the tectonic strength of the globe is far superior in DSAEK, as a 360-degree fullthickness corneal wound is avoided.

Visual Acuity

Li et al have recently shown that vision continues to improve steadily after DSAEK up to 4 years postoperatively.⁴⁵ In this study, patients’ mean best spectacle-corrected visual acuity (BSCVA) improved from 20/30 at 6 months and 1 year postoperatively, to 20/26 at 2 years, and 20/25 at 3 years postoperatively. In addition, the percentage of patients obtaining 20/25 or better increased from 36% at 6 months to 70% at 3 years; the percentage obtaining 20/20 increased from 11% at 6 months to 47% at 3 years postoperatively. This is thought to be due to long-term corneal stromal fiber remodeling, improving the optical performance of the donor-recipient interface.

Although visual outcomes after the advent of DSAEK have improved dramatically, not all patients achieve 20/20. This is typically explained by interface optical problems between the recipient and donor stromal faces.

(29)

Hyperopic Shift and Astigmatic Change

A well-recognized hyperopic shift occurs after DSAEK in the order of +0.76 to +1.5 D, with a mean of +1.1D. Theories explaining this include the fact that the donor lenticule is like a diverging lens, with peripheral donor stroma thicker than the central stroma. Astigmatic change after DSAEK varies with the size and site of incision used. A 5-mm scleral tunnel incision induces minimal change in refractive astigmatism and was reported to induce a mean change of 0.06D.⁴⁶ It also provides a tectonically strong, self-sealing wound.

(30)

1.5 SPECULAR MICROSCOPY

The specular microscope (SPM) is a specializes microscope which is used to visualize and record the corneal endothelium. And using in-built computer programs we can various parameters of the endothelial structure.

Vogt in 1918 first visualized the endothelial layer in slit lamp using the method of specular reflection and described it as "a graceful honeycomb".

Later in 1968 David Maurice made the first specular microscope. Over the years i has evolved from contact, wide field type to non contact, narrow field and high resolution type.

Principle of specular microscopy

In normal microscopy we look at the light transmitted through the specimen but in specular we are more interested in the light that is reflected.

When light strikes the surface. it can be reflected, transmitted or absorbed.

Specular reflection or mirror like reflection happens when the angle of incidence is equal to angle of reflection. This image is captured by the SPM.

Light striking the normal cornea is mostly transmitted but a small fraction is reflected at interface of different optical density(or refractive index) eg tear-epithelial interface, endothelium- aqueous interface. At the endothelium- aqueous interface about 0.002% of the light is reflected back.

The greater the difference between the refractive indices, the more is the amount of reflected rays. The area of the specular reflex also depends upon the radius of curvature of the reflecting surface. Also it is important to know if the

(31)

area being imaged is representative of the entire cornea. For example, one can image an area of focal injury in an otherwise normal cornea and the abnormal counts will get extrapolated to the whole area.

There are certain criteria to obtain the ideal specular image . The endothelium must be at the accurate distance for the focus os the objective lens.

The part of the endothelium being imaged must be perpendicular to the optic axis of the objective lens.

The quality of the image depends on the numerical aperture of the objective lens, how clean the lens are. Another important factor is the presence of glass or plastic and storage media between the lens and tissue. Although transparent, these can lead to considerable distortions . A viewing chamber can reduce this problem to some extent.

Types of specular microscopes

1. Contact and non contact depending on the nature of the objective lens.

The image resolution depends on the numerical aperture of the objective lens. This is bit higher with contact objective lens thus giving a sharper image. They also reduce the ocular movement so the image has less motion artifacts. Contact SPMs can be used to image the epithelium and atroma too and give accurate pachymetric values. But being more practical and easy to use, the non contact ones are being used more commonly.

2. Clinical and eye bank specular microscopes.

(32)

Specular analysis

Specular microscope image can be interpret in two ways:

1. Qualitative

2. Quantitative

Qualitative analysis : Here we look at the appearence of the cell borders, cell shape, intra-endothelial and inter- endothelial abnormalities.

A normal specular image will show endothelial cells as bright hexagons with dark cell borders. Cells are of uniform size and shape with no abnormal bright or dark areas. The cell density is between 2000-3000 cells/mm²with more than 60-70% hexagoonal cells.

The light falling on the cell borders are reflected in such a way that they are not received by the SPM and are seen as dark, thin lines whereas rays

(33)

falling on the surface of the cell undergo orderly reflection forming a bright area. Normally the borders form a hexagon with three lines meeting at 120°. In pathological conditions there may be rounding of the borders secondary t oedema, trauma or aging.

Cell shape variation is a part of normal aging. With decreasing numbers the cells increase in size and associated shape alteration take place. Abnormal cells can appear as stretched, scalloped, rounded, square or triangular. Injured endothelium can show signs of healing like enlargement of cells to fill up the damaged areas or cells coalescence where the cell border between the two cells disappears slowly as they merge together.

Guttae are excrescences of the descemet's menbrane. They appear as dark with central bright spot with abnormally shaped surrounding cells. These excrescences and coalesce can hinder visualization of the endothelium. Hassal- Henle warts are also excrescences seen in the peripheral cornea. These are usually dome shaped with normal endothelial cells. Bacteria and inflammatory cells appear as small bright twinkling objects with changing shape and position.

Quantitative analysis: Here we use in-built computer programs to automaically or semi- automatically calculate various endothelial cell features.

The various parameters which are looked at are:

1. Endothelial cell density (ECD) - number of cells/ mm²

2. Mean or Average cell area - measures as µm²

(34)

3. Coefficient of Variation (CV) - Variation in the areas of different cells

4. Percentage of Hexaganolity (6A) - Percentage of cells that are perfectly hexagonal.

1. Endothelial cell density: This can be counted in a number of ways.

a. Fixed frame analysis - A box of known area is overlayed on the specular image and number of cells inside are counted as half. The total is then multiplied by the number depending on area selected. This method is very error-prone because of the 'border cells' or cut off cells and is rarely used nowadays.

b. Variable frame analysis - A variable shape of contiguous cells is first outlined, then cells in this defined area are counted. The selected area is determined by computer planimetry. Once the area is known, the ECD is calculated. This is superior to fixed frame method as only complete cells are counted and there is no confusion regarding partially included cells. This is the most accurate and reliable semi accurate method of counting. However, this method does not provide very accurate data about cell size distribution as doing it for a large number of cells is very tedious.

c. Center method - A newer method where only the center of the cells are marked. The computer identifies the adjacent cells and performs the calculation. It is important to mark at least a hundred cells because cells without adjacent cells may be discarded while comuting.

(35)

Center- flex method is a hybrid of variable frame analysis and center method where the user outlines the borders of cells and ,marks their centers.

d. Corner method - Each cell is marked by identifying the six corners. The software connectss those dots and determines the area and ECD. This method was used initially.

e. Comparison to fixed pattern - The image is compared to various specular images of known ECD values and closest match is considered as the count. It gives a very rough estimate.

2. Coefficient of variation: CV is a numerical representation of polymegathism. polymegathism refers to the variations in cell size.

CV = SD cell area/ Mean cell area in µm²

3. Percentage Hexagonality (6A) : Pleomorphism or polymorphism refers to the variation is cell shapes. 6A is a numerical way to represent that.

Polymorphic cells have less or more than 6 sides and are therefore less hexagonal. Also, CV and 6A are inversely related. Change in cell size is almost always associated with change in shape. So more CV would mean less hexagonality.

In quantitative analysis, the ECD is not the only parameter to look at.

Polymorphism and polymegathism are believed to be sensitive indicators of endothelium under stress. A high CV and low 6A indicates unusable

(36)

relationship between neighboring cells which can lead to loss of pump and barrier function.

Modern SPMs have completely automated counters which outline and count cells automatically in a given area and generate the morphometric reports. The intelligent programs is able to identify and exclude areas of poor or unfocussed image quality. The amount of cells counted is much more than manual method thus giving better statistical results. It is also able to give additional data like a cell density histogram, gives overlay showing abnormal cell sizes in different colours. And all that is done in less than a minute.

Accuracy of the quantitative analysis depends on - image quality, how well the sampled area represents the whole cornea , technicians ability to identify cells and borders and mark accurately. Common errors are missing cells, double counting and not being able to identify the borders correctly.

Automated counters should always be supervised by a trained personnel with knowledge of cornea so that the above errors can be minimized.

The age of the cornea is less important than the appearence of the cell in determining the health and functional reserve of the tissue.

Applications of specular microscopy

1. Donor cornea evaluation in eye bank and selecting tissue for optical and endothelial surgeries.

2. Endothelial keratoplasty - Initially high loss of cells at 6-12 months

(37)

3. Fuch's corneal endothelial dystrophy - documenting progression

4. Cataract surgery - pre and post op images to study the cell loss during various surgical procedure

5. ICE (irido corneal endothelial) syndrome shows a reversal appearence with black border and white central area.

6. Differentiating posterior polymorphous corneal dystrophy from ICE

7. Documenting corneal guttae

8. Physiological ECD losswith aging at about 0.5 - 1% per year

9. Keratoconus - shows elongated cells with long axis towards direction of apex of cone

10. Documenting endothelial damage following intraocular inflammation, trauma, vitreous touch, in contact lens users, in diabetics, etc.

(38)

1.6 REVIEW OF LITERATURE

1) Descemet Stripping Automated Endothelial Keratoplasty Mark S. Gorovoy, MD

The speed of visual recovery in 16 consecutive patients with corneal endothelial dysfunction who received Descemet stripping automated endothelial keratoplasty (DSAEK) is evaluated. This is a retrospective study of a small incision endothelial transplantation (DSAEK). Endothelial replacement was accomplished with Descemet stripping of the recipient and insertion of a posterior donor tissue that had been prepared with a microkeratome. Best spectacle-corrected visual acuity (BSCVA) by manifest refraction, endothelial counts, and dislocation rates were measured up to 12 months after DSAEK. Results were Sixteen consecutive patients underwent uncomplicated DSAEK. Three patients had known optic nerve or macular disease precluding vision better than 20/200. Of the remaining 14 patients,11 had BSCVA of 20/40 by postoperative week 12 (7 by week 6). The remaining 2 were 20/50 by weeks 6 and 12. All 14 patients were 20/40 or better at 1 year. One patient had a primary graft failure, and surgery was repeated with 20/40 BSCVA at 1 year. The dislocation rate was 25%. The average cell count between 7 and 10 months was 1714. The average pachymetry was 682. Thus it was Concluded that DSAEK surgery allows rapid, excellent BSCVA visual recovery. The rate of visual recovery is more rapid than usually found with penetrating keratoplasty

(39)

2) Descemet’s Stripping Endothelial Keratoplasty: Safety and Outcomes W. Barry Lee, Deborah S. Jacobs et al

The most common complications from DSEK among reviewed reports included posterior graft dislocations (mean, 14%; range, 0%–82%), followed by endothelial graft rejection (mean, 10%; range, 0%–45%), primary graft failure (mean, 5%; range, 0%–29%), and iatrogenic glaucoma (mean, 3%;

range, 0%–15%). Average endothelial cell loss as measured by specular microscopy ranged from 25% to 54%, with an average cell loss of 37% at 6 months, and from 24% to 61%, with an average cell loss of 42% at 12 months.

The average best-corrected Snellen visual acuity (mean, 9 months; range, 3–21 months) ranged from 20/34 to 20/66. A review of postoperative refractive results found induced hyperopia ranging from 0.7 to 1.5 diopters (D; mean, 1.1 D), with minimal induced astigmatism ranging from _0.4 to 0.6 D and a mean refractive shift of 0.11 D. A review of graft survival found that clear grafts at 1 year ranged from 55% to 100% (mean, 94%). The evidence reviewed is supportive of DSEK being a safe and effective treatment for endothelial diseases of the cornea. In terms of surgical risks, complication rates, graft survival (clarity), visual acuity, and endothelial cell loss, DSEK appears similar to penetrating keratoplasty (PK). It seems to be superior to PK in terms of earlier visual recovery, refractive stability, postoperative refractive outcomes, wound and suture-related complications, and intraoperative and late suprachoroidal hemorrhage risk. The most common complications of DSEK do not appear to be detrimental to the ultimate vision recovery in most cases.

(40)

Long-term endothelial cell survival and the risk of late endothelial rejection are beyond the scope of this assessment

3)Early Results of Small-Incision Descemet’s Stripping and Automated Endothelial Keratoplasty

Steven B. Koenig, Douglas J. Covert,

Prospective, noncomparative, surgical case series. Twenty-six eyes of 26 patients who had corneal edema from Fuchs’ endothelial dystrophy, pseudophakic bullous keratopathy, or aphakic bullous Keratopathy were the participants. The donor corneal lenticule was prepared using a microkeratome and an artificial anterior chamber maintainer. Stripping of the diseased host endothelium was performed under viscoelastic using a 2.75-mm clear corneal temporal incision. The incision was enlarged to approximately 4.2 mm to allow placement of a folded 8.5-mm-diameter donor corneal lenticule. The donor graft was positioned using a temporary air bubble that was partially evacuated after 7 minutes. The corneal wound was closed with a single 10-0 nylon suture.

Three months postoperatively, all donor grafts remained clear. The average 3- month postoperative BSCVA was 20/45 (range, 20/20–20/150). The average change in refractive astigmatism was 0.12-1.15 diopters (D) (range, 1.50 to 3.25). In patients who underwent simple DSAEK (i.e., no intraocular lens implantation), the average postoperative shift in spherical equivalent refractive error was 1.15-1.35 D (range, 0.25 to - 4.25). Nine of 26 initial grafts dislocated postoperatively had to be repositioned. Three of the repositioned

(41)

grafts dislocated again and were replaced with new donor corneal lenticules, all of which remained clear.Descemet’s stripping and automated endothelial keratoplasty uses a mechanical microkeratome to harvest the donor corneal lenticule and mechanical stripping of the diseased host endothelium and Descemet’s membrane. Despite a smooth graft– host interface, only 2 patients in the series achieved 20/25 vision. The average visual results were comparable to vision after deep lamellar endothelial keratoplasty. Although patients had excellent postoperative acuity with minimally induced surgical astigmatism, about one third of the donor lenticules needed to be either repositioned or replaced.

4) Descemet’s stripping endothelial keratoplasty Marianne O. Price and Francis W. Price

Descemet’s stripping endothelial keratoplasty (DSEK) is rapidly becoming the preferred treatment for corneal endothelial dysfunction.

Familiarity with recent advances in techniques and instrumentation can help reduce the initially steep learning curve and incidence of complications.DSEK produces excellent visual outcomes with minimal change in corneal surface topography or refraction. It can successfully treat corneal dysfunction associated with Fuchs’ endothelial dystrophy, bullous keratopathy, iridocorneal endothelial syndrome or a failed penetrating graft. Donor dissection has become automated, and new techniques have been devised to facilitate graft insertion and unfolding. Graft detachment is the most frequent early

(42)

postoperative complication . The incidence of graft-rejection episodes is lower after DSEK compared with standard penetrating keratoplasty, possibly because wound healing is a lesser concern, and many DSEK patients are maintained on low-dose topical steroids.DSEK provides quicker visual rehabilitation and an improved safety profile compared with standard penetrating keratoplasty

5) Descemet’s stripping automated endothelial keratoplasty:

innovations in surgical technique Neelofar Ghaznawi , Edwin S. Chen

Endothelial keratoplasty offers several advantages over conventional penetrating keratoplasty due to its superior tectonic, topographic and refractive stability. Recent advances in endothelial keratoplasty include expansion of indications, modification in host preparation, and newer insertion techniques.

DSAEK has been successfully used in post penetrating keratoplasty, ICE syndrome, aniridia, aphakia, complex anterior chambers with anterior chamber lenses, and pediatric patients.. Newer techniques in endothelial keratoplasty have broadened its use, improved intraoperative ease, and reduced postoperative complication. As we make this surgical procedure faster and easier, surgeons must critically evaluate the impact of these modifications on long-term patient outcomes.

(43)

6) Endothelial Keratoplasty: A Revolution in Evolution

Arundhati Anshu, Marianne O. Price, Donald T.H. Tan and Francis W.

Price Jr.,

Endothelial keratoplasty (EK) is continually evolving both in surgical technique and clinical outcomes. Descemet’s stripping endothelial keratoplasty (DSEK) has replaced penetrating keratoplasty (PK) as the treatment of choice for corneal endothelial dysfunction. It is safe and predictable and offers early visual rehabilitation. Newer EK include Descemet’s membrane endothelial keratoplasty, Descemet’s membrane automated endothelial keratoplasty. Early data on these newer EK techniques suggests that they provide significantly better visual outcomes compared to DSEK. Initial 5-year survival data indicates that EK is at least comparable to PK, and more widespread survival data is anticipated. Further work is needed to simultaneously optimize visual outcomes, refractive predictability, and endothelial cell survival, as well as surgical techniques of donor preparation and insertion.

(44)

PART II

(45)

2.1 AIMS & OBJECTIVES AIM

To analyze the outcome of descemet’s stripping automated endothelial keratoplasty (DSAEK) for corneal endothelial disorders.

HYPOTHESIS

Descemet’s stripping automated endothelial keratoplasty (DSAEK) is a safe and effective method of corneal transplantation for corneal endothelial pathology without anterior stromal scarring.

OBJECTIVES

1. To evaluate the visual outcome and the endothelial count after descemet’s stripping automated endothelial keratoplasty (DSAEK).

2. To study the indications, intra-operative and post-operative complications associated with descemet’s stripping automated endothelial keratoplasty.

OUTCOME MEASURES :

PRIMARY OUTCOME MEASURES :

1. Mean BCVA at the final follow up after descemet’s stripping automated endothelial keratoplasty .

2. Mean endothelial cell count and endothelial cell loss at the final follow up after descemet’s stripping automated endothelial keratoplasty .

(46)

SECONDARY OUTCOME MEASURES :

1. Common indications of descemet’s stripping automated endothelial keratoplasty (DSAEK).

2. Rate of intra-operative and post-operative complications associated with descemet’s stripping automated endothelial keratoplasty (DSAEK).

(47)

2.2 MATERIALS AND METHODS DESIGN

This is a prospective, non-comparative study conducted at Tertiary eye care center.

DURATION

Patients were recruited from December 2015 to November 2016 and were followed up for a minimum of 6 months till May 2017.

SETTING

The study was conducted in the department of cornea and refractive surgery at Tertiary eye care center.

SAMPLE SIZE

During this period of one year from December 2015 to November 2016, 50 patients were recruited in the study who satisfied the inclusion criteria and didn't fall into the exclusion criteria underwent descemet's stripping automated endothelial keratoplasty.

INCLUSION CRITERIA

1. Bullous Keratopathy a. Pseudophakic b. Aphakic c. Phakic

(48)

2. Corneal Endothelial Dystrophies (Fuch’s dystrophy)

3. Endothelial Failure (Post surgery)

EXCLUSION CRITERIA 1. Corneal stromal scarring.

2. Coexistence of other ocular pathology that may preclude attainment of good visual acuity after DSAEK.

DIAGNOSIS

Diagnosis of the disease was made by careful history , slit lamp examination and specular microscopy.

INFORMED CONSENT

Outcome of surgery in detail including the possibility of the various complications in his or her own language. patients were informed about the follow - ups involved in the study.

STEPS OF SURGICAL PROCEDURE

Descemet's stripping automated endothelial keratoplasty was performed by surgeons having experience in lamellar and full thickness keratoplasty.

Procedure was performed under conventional peribulbar anaesthesia. Pupillary dilatation was required only in cases where it was combined with cataract extraction and intraocular lens implantation. In other cases, the pupil was

(49)

constricted by instillation of 2% of pilocarpine eye drops 30 minutes prior to surgery.

DONOR LAMELLAR DISSECTION :

Donor tissue is prepared using the Moria automated lamellar therapeutic keratoplasty (ALTK) system using a 300µ head.Before the surgery, donor corneo-scleral tissue is placed in the artificial anterior chamber (AAC) with saline. Microkeratome is then used to remove the anterior corneal disc of 300µ thickness. The excised anterior stromal disc is assessed for completeness.The posterior corneal button is marked for orientation and then is removed from the AAC and positioned centrally within a teflon block with endothelium facing up. The donor button is trephined using 7.0 to 8.5 mm diameter trephine (depending on the diameter of the recipient cornea).

(50)

Fig 2: Artificial anterior chamber

Fig 3 : Donor lenticule

(51)

Fig 4 :Lenticule positioned centrally within a teflon block with endothelium facing up

Fig 5 : The donor button is trephined using 7.0 to 8.5 mm diameter trephine (depending on the diameter of the recipient cornea)

(52)

RECEPIENT BED PREPARATION

1. A circular template mark (with a diameter of 7.0 to 8.5) with gentian violet was made on the corneal epithelial surface which served as a reference mark for Descemet stripping. In some cases, loose edematous and hypertrophied epithelium was removed before marking.

2. Temporal peritomy was done and applying wet field cautery, a 5 to 5.5- mm limbal tunnel was prepared with a cresent blade.

3. Two 1-mm stab incision side-ports were made on either side of the main incision at 10 and 2 o′clock positions. These were to manipulate and unfold the donor lenticule.

4. Cohesive viscoelastic agent, 1% Sodium hyaluronate was injected through the side port.No dispersive viscoelastic agent was used during any step of the procedure.

5. The AC was entered with a 2.8-mm angular keratome. It was enlarged on either side to the same length as the external incision.

6. In patients who underwent a combined procedure (DSAEK with PCIOL) the surgery was performed through a 6.0-mm tunnel. After cortical cleaning PCIOL was placed in the-bag. The IOL power was calculated from the biometry of the same or the other eye. The pupil was then constricted with intracameral pilocarpine (0.5%) injection.

(53)

7. Circular dissection of the Descemet membrane (or Descemet scoring) was carried out with a reverse Sinsky′s hook which corresponded to the 7 to 8.5 mm epithelial template mark. Descemet membrane was completely stripped off with the help of the hook, and the diseased tissue was removed. In some cases with severe corneal edema, trypan blue (0.06%) solution was used to stain the diseased endothelium and it was also useful to stain the anterior capsule in the combined procedure.

8. An inferior peripheral iridectomy is performed to prevent future pupillary block.

9. Viscoelastic agent is washed out thoroughly and carefully with balanced salt solution (BSS) using an irrigation/aspiration cannula and AC was then well formed with BSS.

Fig 6 : Descemet's scoring

(54)

TRANSPLANTATION OF DONOR LENTICULE

• A 5 mm Sheet's glide was inserted into the anterior chamber through the scleral wound

• Viscoelastic agent was placed on the surface of the glide

• The donor lenticule was transferred endothelial side down onto the viscoelastic coated sheet glide.

• During this maneuver the anterior chamber is formed with BSS

• The lenticule is then pushed into the anterior chamber with sinskey hook.

• The anterior chamber was filled up with BSS.

• Air was then injected carefully through a 30-gauze cannula from the left side-port to attach the donor lenticule.

• Centering of the donor lenticule was done by massaging over the cornea.

• Interface fluid was removed through venting incisions, by gentle massage and stroking the corneal epithelial surface with a flat cannula.

• Side ports were hydrated and the main wound was sutured with interrupted 10-0 nylon sutures

• At the end of the surgery, the anterior chamber was filled with air for 8- 10 minutes

• Approximately 50% of the air was left in the anterior chamber

• The conjunctiva was closed by wet field cautery

• Patient received a drop of homatropine at the end of the procedure

(55)

• A bandage contact lens is applied at the end of the surgery.

• The eye was patched and the patient was instructed to lie supine for one day.

Fig 7 : Showing donor lenticule transferred onto Sheet's glide

Fig 8 : Air bubble injected into AC using 30 gauze cannula

(56)

Fig 9 : Interface fluid removed using gentle massage

POST OPERATIVE MANAGEMENT AND FOLLOW UP Medication:

Corticosteroids:

Topical 1% prednisolone acetate four times a day was used in a routine lamellar keratoplasty. These can be tapered early and stopped compared to penetrating keratoplasty.

Antibiotics:

Topical broad spectrum antibiotics like gatifloxacin was used four times a day for three to six months.

Suture removal :

Sutures should be removed if it is infected or loosened or broken.

Otherwise sutures can be removed anytime after three months.

(57)

Follow up :

Patient was admitted for atleast five days after the procedure.Thereafter patient was reviewed after a month, again at 3rd month and then at 6 month and finally after a year. All the patients who had completed the first six months′

follow-up were included in this study.Uncorrected visual acuity (UCVA), best spectacle corrected visual acuity (BCVA), and specular microscopy for endothelial cell density (ECD), were performed at six month in each case.

Best corrected visual acuity was tested by trained optometrists. specular microscopy was performed by a trained technician and she was masked to the outcomes of the surgery. She did not know the preoperative endothelial count of the donor cornea which was transplanted in a particular patient.

EXAMINATION

The following examination was done before and after descemet's stripping automated endothelial keratoplasty

• Uncorrected visual acuity (UCVA)

• Best spectacle corrected visual acuity (BCVA)

• Slit lamp examination

• Tonometry by Noncontact tonometre and digital tension

• B scan

• Specular microscopy

(58)

The comprehensive ophthalmic examination was done for every patient at each visit and was recorded on a preset proforma along with the mention of the complication and the additional intervention if any.

BEST CORRECTED VISUAL ACUITY

• Visual acuity was tested by using snellen's chart at 6 metres

• Refraction was done at sixth month except in patients with acute pain and redness.

SLIT LAMP EXAMINATION

• Donor tissue and the recipient cornea were examined carefully for any abnormalities like graft edema, interface haze, interface debris, lenticule cleft, infiltrate etc.

• Conjunctiva, anterior chamber depth and inflammatory reaction, iris changes, pupil, lens status etc were noted at each visit.

TONOMETRY

The intra ocular pressure was measured using non contact tonometer in each case during 1month, 3rd month and 6th month follow up. In cases where non contact tonometer could not assess IOP, tension was assessed by digitial tension.

(59)

B SCAN

B scan was done for all the patients pre operatively to rule out pre existing posterior segment pathology.

SPECULAR MICROSCOPY

Preoperatively endothelial cell density was performed on the donor corneal tissue (n=50) by the eye bank and specular microscopy was performed postoperatively at 6 month follow up for 35 cases excluding those with complication and cases lost to follow up. Endothelial cell density of the donor cornea was analysed and compared with the preoperative donor corneal endothelial cell count. Mean endothelial cell loss at 6th month follow up was analysed.

POST OPERATIVE FOLLOW UP

Patients were discharged after 5 post operative days.

Patients were followed up for a minimum period of 6 months

1st follow up at 1 month

2nd follow up at 3 month

3rd follow up at 6 month

(60)

MAIN OUTCOME MEASURE

Post operative uncorrected visual acuity

Post operative best corrected visual acuity

Mean endothelial cell density

Mean endothelial cell loss

Common indications

Intra operative and Post operative complications

STATISTICAL METHODS

Descriptive statistics were employed to summarize demographics and outcome characteristics of the subjects. Continuous variables like IOP, age were expressed as mean, standard deviation and range. Categorical variables like visual acuity by snellen's chart, complication, gender distribution were expressed as frequency or percentage. Wilcoxan- signed rank sum test was used to assess the difference between continuous variables for non-parametric data. Friedman test was used to assess the difference between the variables over the consecutive time period. P-value less than 0.05 was considered as statistically significant. Microsoft excel sheet was used as database tool. All analysis was done by statistical software STATA version 11.0 (Texas, USA).

(61)

2.3 OBSERVATION AND RESULTS

A total of 50 eyes of 50 patients were included in the study as per the study protocol to analyse the outcome descemet's stripping automated endothelial keratoplasty in the corneal endothelial disorders. This is a prospective non comparative study done at the department of cornea, Aravind eye hospital, Madurai from December 2015 to November 2016. Demographic profile of the patients included in the study are summarized below.

AGE AND GENDER:

Mean age of the patient who underwent DSAEK in the study was 63.78

±9.12 years (Table 1, Chart 1). The range varied from 38 - 80 years. Out of the 50 patients 27 were male (54%) and 23 were female (46%)(Table2, chart 2).

All patients had clinically significant stromal edema, microcystic epithelial edema or frank bullous keratopathy.

(62)

Age distribution

Mean 63.78 ±9.12 years

Range 38 - 80 years

Age group 35 - 50 years 51 - 65 years 66 - 80 years > 80 years

Total 4 28 18 0

Table 1 : Age distribution

4

28

18

0

5 10 15 20 25 30

35-50 years

51-65 years

66-80 years

> 80 years Age distribution

Age distribution

Chart 1 : Age distribution