Chapter 19 – Automated and Manual Lamellar Surgical Procedures and Epikeratoplasty
DIMITRI T. AZAR
• Lamellar refractive surgery comprises various surgical procedures that entail lamellar dissection of the cornea and reshaping the corneal stroma to correct refractive errors of the eye.
• Usually employed to correct high myopia or hyperopia.
• The lamellar dissection is usually performed using a microkeratome with an oscillating blade.
• A lamellar lenticule is lifted and reshaped, replaced, or flapped to allow refractive correction.
Several procedures are encompassed in this category:
• Keratomileusis with freezing.
• Planar lamellar refractive keratoplasty.
• Keratomileusis in situ.
• Automated lamellar keratoplasty.
• Laser in situ keratomileusis.
• Synthetic epikeratoplasty.
• Deep lamellar keratoplasty.
Lamellar refractive surgery has undergone a long evolutionary process. Lamellar refractive surgery for the correction of hyperopia and myopia ( Fig. 19-1 ), also known as keratomileusis, was pioneered by Barraquer in the early 1960s. Another lamellar procedure to correct aphakia, termed keratophakia, was introduced by Barraquer  as well. In 1977, Troutman and Swinger  introduced hyperopic lamellar procedures in the United States, and Swinger performed the first myopic procedure in 1980. Swinger and Villasenor contributed substantially to the surgical knowledge of keratomileusis in the United States, and Nordan and Maxwell standardized it for consistent and systematic teaching.
Kaufman introduced the onlay lamellar refractive procedure in 1979, initially termed epikeratomileusis and later epikeratoplasty (now the accepted term). Nonfreeze planar keratomileusis, which permitted operations without freezing, was described by Krumeich and Swinger in 1983. In an effort to avoid the drawbacks of these techniques, keratomileusis in situ (see Fig. 19-2 ) has been developed and carried out. Combining this approach with excimer laser surgery led to laser in situ keratomileusis (LASIK), which is currently the method of choice to correct wide ranges of refractive errors (discussed in greater detail in Chapters 20 and 27 ). Lamellar refractive surgery has undergone a long evolutionary process. However, for lamellar techniques to be the first choice for the correction of extreme refractive errors, the accuracy and optical performance must approach those of intraocular lens surgery.   
PREOPERATIVE EVALUATION AND DIAGNOSTIC APPROACH
Patient Selection for Lamellar Refractive Surgery
Generally, patients must be over 18 years of age and serial examination must reveal stable refraction and topography prior to surgery. Patients are screened for corneal disease—epithelial basement membrane disease, forme fruste keratoconus and/or corneal warpage detectable by routine corneal topography, and history of recurrent erosions or keratitis are considered relative contraindications. The patient must also be screened for retinal disease, which may have to be treated before surgery. Contact lens wear is discontinued for at least 1 week for soft lenses and for 3–4 weeks for hard lenses.
The patient must have adequate globe exposure and be cooperative enough for local anesthetic. All patients are informed thoroughly as to the nature of the procedure and must know what to expect intraoperatively and postoperatively.
No matter which corneal surgical procedure is performed, proper centration is critical to avoid postoperative complications such as irregular astigmatism and glare that may interfere with visual function. Different approaches to the precise site at which the procedure is centered are used. Although some investigators argue that the “visual axis” is the optimal site of centration, the preponderance of evidence indicates that the center of the entrance pupil is the optimal site on which to center keratorefractive procedures. 
Various techniques have been described for corneal centration. Steinberg and Waring utilized the light reflex as a reference point. This technique has been abandoned because most surgeons currently center treatment on the pupil and not on the corneal light reflex.
The Osher centration device is best used to center the treatment on the pupil (the corneal light reflex is ignored), which is valuable if the surgeon has no ocular dominance while the cornea is viewed binocularly. The fixation light in the Zeiss and Weck centration devices and the nonluminous fixation point in Thornton’s methods are other examples of such devices.
When lamellar refractive surgery, such as automated lamellar keratoplasty and laser-assisted in situ keratomileusis, is carried out, the center is sometimes marked using two concentric circles, one internal (3?mm in diameter) and one external (10.5?mm in diameter), attached by a line that touches the smaller circle tangentially to give a pararadial line. Alternatively, multiple pararadial lines may be used.
Figure 19-1 Keratomileusis. In myopic keratomileusis, a corneal button is raised using a microkeratome, and it is reshaped using a cryolathe (upper part). When the button is replaced, the central cornea is flattened (lower part). In hyperopic keratomileusis a cryolathe is used to reshape the stromal lenticule and increase central corneal curvature.
Figure 19-2 In situ automatic corneal reshaping of the keratomileusis bed. A corneal button is raised using a microkeratome. A second pass modifies the stromal bed to allow corneal flattening after replacing the cap.
KERATOMILEUSIS WITH FREEZING
Indications and Contraindications
Keratomileusis with freezing was used to correct myopia surgically by as much as 16D with low predictability. Major disadvantages of keratomileusis with freezing include the following:
• Complexity of the technique
• Sophistication of the technical equipment itself—a microkeratome and a cryolathe
• Time required to attain sufficient expertise in using the two instruments
• Long recovery period because of the changes in the corneal tissue structure after freezing of the lenticule
Surgical instruments necessary for keratomileusis with freezing include a microkeratome to perform the lamellar keratectomy, a set of suction rings with which to fix the eye and guide the microkeratome, a microcomputer or calculator for the cryolathe procedure, the cryolathe itself, and the means to prepare the refractive lenticule.
The Barraquer cryolathe consists of a Levin contact lens lathe modified with freezing circuits, digital micrometers, and other necessary alterations. After the microkeratome resection, the host cornea is turned on the cryolathe. During lathing, the corneal tissue, the head stock of the lathe on which the cornea is mounted, and the lathing tool are all brought to approximately -20°C. After the cornea has been reshaped, it is thawed and placed back in the host bed.
The Barraquer cryolathe is accurate but technically complex and expensive. Although the process of freezing enables the resected disc to be shaped precisely, it nonetheless results in death of the keratocytes and considerable postoperative corneal edema. Both of these factors contribute to a prolonged postoperative recovery period and to delayed epithelialization and epithelial ingrowth.
In autoplastic refractive procedures, the lenticule is prepared while the patient is on the operation table, whereas in homoplastic procedures, the lenticule is
usually prepared and stored before surgery. The tissue is dehydrated in a corneal press to bring it to normal dimensions. If a cornea that has a scleral rim is used, it is placed in an artificial anterior chamber and a keratectomy is performed using the microkeratome. The disc obtained by keratectomy, whether from the donor or the patient eye, is frozen on the cryolathe for up to 2 minutes and machined to the necessary dimensions. The keratophakia lenticule, which is a positive-meniscus lens, consists of stroma only and measures approximately 0.2?mm in thickness and 6?mm in width. The keratomileusis lenticule has an anterior membrane complex (without epithelium, if homoplastic) as well as the stroma. Homoplastic lenticules may be used immediately, stored in the refrigerator for a few days, kept frozen, or lyophilized. They may also be ordered from a lens laboratory.
Refractive procedures are carried out most commonly on an ambulatory basis under peribulbar or topical anesthetic. Reference marks are made on the epithelium over the visual axis to center the keratectomy and in a pararadial line to realign the anterior cap. A perilimbal suction ring is placed, and the intraocular pressure (IOP) and proposed diameter of resection are verified. The ring is changed as necessary until the correct diameter is applanated. The circular lamellar disc, resected from the patient by a microkeratome, is replaced, aligned with the reference mark, and attached with a running, eight-bite, antitorque suture begun at the 12 o’clock position. The interface must be cleaned meticulously. The previously prepared keratophakic lenticule is placed into the interface using a spatula and centered over the visual axis. The suture is tied and the tension adjusted under keratometric control such that it is not too tight and a small gap is present for 360°.
PLANAR LAMELLAR REFRACTIVE KERATOPLASTY
Indications and Contraindications
Because freezing corneal tissue results in severe damage to the keratocytes and the lamellar architecture of the cornea, planar lamellar refractive keratoplasty has two advantages: shorter recovery period of the visual function and stability of the correction because of the absence of cryotrauma to the corneal disc. However, this technique is much more unpredictable than keratomileusis with freezing and also may predispose to corneal ectasia if the desired correction is very high.
The nonfrozen planar keratomileusis technique is essentially the same as that used by Barraquer for keratomileusis, with changes to some steps. When a myopic keratomileusis is carried out, the diameter of the resected disc is 9.00?mm (depending on the equipment used), and the disc is cut by a single pass using the microkeratome. The technique employs a newly developed instrument that obviates the need for freezing and requires a button as large as possible to ensure good fixation in the device. For this reason, a newly designed microkeratome, which allows a larger resection diameter than the classical Barraquer microkeratome, has been developed.
In nonfrozen planar keratomileusis the lenticule may be prepared without the need for chemical solutions and the disc modified without freezing.
KERATOMILEUSIS IN SITU
Indications and Contraindications
In keratomileusis with freezing or planar lamellar refractive keratoplasty, the predictability of the surgery relies mostly on the accuracy of the cryolathe or keratoplasty equipment used, whereas the precision of keratomileusis in situ depends on the accuracy of the microkeratome performance.
The microkeratome has a high-speed oscillating blade; the principle of the carpenter plane is used to resect corneal discs of different diameters and thicknesses from either the patient or the donor cornea. Keratomes are microprecise machines that can produce parallel-faced lamellar discs to an accuracy of 5–10?µm. The accuracy of the keratectomy is extremely important to obtain the ideal outcome after keratomileusis. Designs of the microkeratome for lamellar refractive surgery have changed significantly in recent years—main characteristics of currently available microkeratome systems are given in Table 19-1 . The quality of keratectomy is assessed by the disc’s smoothness, roundness, and uniformity of depth and diameter, parameters that depend mostly on the variables of the keratome such as IOP, speed of the pass, rate of blade oscillation, sharpness of the blade, angle of the blade, gap between the blade and the plate, and downward force upon the keratome.
TABLE 19-1 — MAIN CHARACTERISTICS OF MICROKERATOME SYSTEMS
Manual or automatic
Manual and automatic
Advance rate (mm/s)
• Stainless steel blade
• Circular stainless steel blade
• Natural diamond blade
• Diamond blade
• Sapphire blade
Stainless steel blade
• Laser beam
• “Point ablation” laser beam
Oscillations per minute
Flap diameter (mm)
Creates intrastromal bubbles and flaps; otherwise unknown
Single, double, four or multiple suction rings/grip fingers
Single suction ring
Single suction ring/none
Computerized eye-tracking system/suction rings
1–500 (fixed or variable)
Adjustable at factory or fixed
Infinitely adjustable or variable
Dependent on the machine type used
Electric, nitrogen gas pneumatic turbine
Stainless steel, titanium
Titanium, various alloys
AUTOMATED LAMELLAR KERATOPLASTY
Indications and Contraindications
Keratomileusis in situ is a highly effective surgical technique. However, as mentioned previously, microkeratome speed and pressure are factors that result in lenticule properties different from the desired ones. In the search for a technique that excluded these effects, the Automated Corneal Shaper was developed. It is used in automated lamellar keratoplasty (ALK) and ensures accurate, regular, and predictable resections as it renders the procedure independent of human factors. Success depends on close attention to detail in the assembly, operation, and maintenance of the instrument. The device is designed to cut corneal lenticules of preselected thickness and diameter, which allows an increase in the accuracy and predictability of ALK. However, ALK is now replaced by LASIK for the most part.
The shaper head has two parts, upper and lower, joined by a hinge that facilitates its assembly. After a blade has been placed between the two parts, the head is closed and fastened by a nut. A motor is connected to the upper body of the shaper head. The plates are essential to define the thickness of the tissues to be resected. Variation in the thickness of the plates results in various distances between the plate itself and the sharp edge of the blade, which allows prior adjustment of the resection thickness within a variation range as small as 5?mm.
The fixation ring, which is of adjustable height, consists of two parts—one fixates the patient’s eye and the other raises or lowers the level of corneal passage and thus varies the diameter of the resection. Three basic functions are fulfilled by the fixation ring:
• Fixes the ocular globe
• Increases the IOP up to >65?mmHg (>8.6?kPa) for the resection to be uniform and regular
• Serves as a guide for the passage of the shaper head
The technique described here is used for myopic, hyperopic, and homoplastic ALK. The setup and procedure until the corneal disc is removed are virtually identical for these situations. The pneumatic fixation ring is placed on the globe so that the eyeball is well exposed. When adequate IOP has been obtained, the resection diameter is graded using the applanation lens. The lens is lowered slowly until it rests horizontally (the cornea must be perfectly dry before the applanation lens is placed to avoid false applanation). The applanation lens used for the first resection is 7.2?mm in diameter. As soon as the applanation lens is placed on the ring, its height has to be adjusted to make the applanation coincide with the inner circle marked on the surface of the lens. This is carried out using the regulating wrench of the ring. Once a given height of the ring has produced the applanation needed for the operation, the resection diameter equals the applanation diameter. The applanation lens and the adjustment wrench are removed.
The shaper is lowered to the horizontal position and inserted in the notch seen on the side of the handle. The shaper is pushed forward gently until a tooth of the largest pinion engages the first tooth of the dented rack. From this position the shaper may be moved readily and the resection carried out. When the pedal is pressed, the shaper slides and cuts the disc. It stops automatically when the large pinion reaches the end of the rack. The shaper then is removed back along the plane of its insertion. The ring is removed. The corneal bed is inspected after the corneal flap has been folded.
Myopic Automated Lamellar Keratoplasty.
If the fixation ring had been removed, it has to be replaced to carry out the second resection; if not, only the applanation lens needs to be placed. The latter is selected, according to the calculation table used, before surgery and placed on a dry corneal bed. The height-regulating wrench is gyrated until the applanation ring touches the inner margin of the circle marked on the lens. Afterwards, the wrench is removed and the shaper is positioned as already described. When the resection is completed, both the shaper and the ring are removed and the accuracy of the lenticule dimensions is checked. The interface and the disc are washed using a brush and saline solution, which prevents proliferation of cells on the interface and results in a much clearer cornea postoperatively. All excess fluid is removed by aspiration and the corneal bed is air dried. As soon as the disc is placed back, the anterior curvature of the cornea shows an applanation equivalent to the said correction.
Hyperopic Automated Lamellar Keratoplasty.
No refractive resection is necessary for the correction of hyperopia. Once the corneal disc has been checked, the surgeon proceeds to wash the corneal bed, air-dry it, and replace the disc in the bed.
To replace the disc accurately, the surgeon must identify and check the epithelial and stromal sides. These must be identified throughout the surgery, from the moment the disc is removed from the microkeratome to when it is measured, cleaned, and stored.
To prevent the disc from folding, it is advisable to place it on a fenestrated spatula. Rotate the spatula and lower the disc toward the eye. With a Weck sponge in each hand, quickly rotate the disc to align it with the pararadial reference line. When placed back in the eye, the disc must have its original position. If instead of forming a straight line, the segments form an angulation, it is likely that the epithelial side is against the stroma. If this occurs, the disc must be removed, both the disc and the corneal surface washed again, and the disc repositioned. Air dry the edge of the disc and check for centration. Any air trapped under the disc must be pushed out gently using forceps. Once alignment and centration are verified, further manipulation of the disc is not required. Air may be used to enhance the cohesion of the disc to the corneal-stromal surface. Do not overdry the cornea with the air as this may cause corneal irregularities. After careful removal of the eyelid speculum, allow the lids to close and make sure that the disc is not displaced by the lid margins.
Homoplastic Automated Lamellar Keratoplasty.
After the corneal disc has been obtained by the method described previously, it is discarded and a new one created from donor tissue. The primary procedure must be repeated using either a whole donor eye or an artificial anterior chamber for anterior donor sections. It is necessary to suture the donor disc to the recipient cornea because the alignment of the donor tissue cannot be duplicated precisely.
Suturing the Corneal Disc.
Sutures may be placed once the corneal disc is positioned correctly. Usually, the material used is 10-0 nylon. An eight-bite, antitorque, running suture is placed—the needle takes 0.75?mm from the disc and 1.0?mm from the periphery, and the knot is buried peripherally. However, it has been established that sutures are not necessary. Various theories of why the cap stays in position have been proposed, which include surface tension, the inherent stickiness of glycoproteins, and the partial relative vacuum of the endothelial cell pump. Without sutures, induced astigmatism is less and the recovery time improves.
Postoperatively, the patient is given mild pain medication and asked to return to the clinic the next day. On this first visit, vision is tested and a slit-lamp examination is performed. The patient is started on a combination corticosteroid antibiotic four times a day for 5 days. The patient is allowed to resume normal activities but is instructed to avoid hits or trauma to the operated eye.
Intraoperative complications include corneal perforation, irregular keratectomy, errors in thickness or diameter, decentered keratectomy, incomplete keratectomy, destruction of the cap, and decentered refractive treatment. Postoperative complications include epithelial growth on the interface, irregular astigmatism, epithelial defect, deposits in the interface, infection, over- and undercorrection, glare, and haze.
Surgical procedures and postoperative care for keratomileusis using manual microkeratomes rather than automated ones are similar except for the setup for particular microkeratomes.
LASER IN SITU KERATOMILEUSIS
Experience with planar keratomileusis and the use of the excimer laser in the treatment of mild and moderate myopia resulted in the combination of these two techniques to take advantage of the high corrective capacity of keratomileusis and the excimer laser’s precision in tissue removal. The aim was to overcome the technical difficulties associated with the refractive incision of both the cryolathe and the nonfrozen keratomileusis technique and thus to achieve an accurate, reproducible, and predictable surgical result.     
The excimer laser may be used to ablate corneal tissue from the resected corneal cap or on the corneal bed. The latter is termed laser-assisted in situ keratomileusis (LASIK), details of which are given in Chapter 20 . The refractive results indicate that this technique may be valuable in the treatment of moderate and mild myopia. As laser software improves, the operation may be of benefit for higher degrees of myopia.
Epikeratoplasty, or onlay lamellar keratoplasty, for aphakia and myopia is a surgical procedure in which a lens made of human corneal tissue is sutured onto the anterior surface of the cornea to change the anterior curvature, and hence refractive properties, of the cornea ( Fig. 19-3 ). Technically, it demands less and is easier to learn than keratomileusis. Suitable methods of tissue preservation allowed manufacture of the graft lenticule, based on reproducible quality standards, by an off-site commercial firm, which improved the uniformity and quality of the lenticules. In addition, this eliminated the need to lathe at the time of surgery. Epikeratoplasty does not violate the optical zone, so it is partially reversible. Because the lenticule is attached to the host cornea peripherally and superficially, it may be removed easily.
The tissue lens, or lenticule, consists of Bowman’s layer and anterior stroma of a donor cornea that has been frozen and lathed. Once the host cornea has been deepithelialized, a small peripheral keratotomy or keratectomy is made to fix the lenticule, held “tongue in groove,” into the circumferential keratectomy, the host epithelium gradually covers the surface, and keratocytes slowly repopulate the donor tissue.       Although a simpler technique than keratomileusis with freezing, epikeratoplasty demands the surface of the cornea to be normal for its maintenance. The technique is less predictable than keratomileusis with freezing and requires a long time before total visual rehabilitation occurs. A donor cornea is used instead of the host cornea to achieve the correction of a refractive error.
Figure 19-3 Epikeratoplasty. A preshaped donor lenticule is sutured to the recipient stromal bed to correct myopia and hyperopia.
Indications and Contraindications
Epikeratoplasty was performed initially in aphakic patients who were not good candidates for secondary intraocular lens (IOL) implantation.     Epikeratoplasty was used later in aphakic pediatric patients.    Compliance with optical and occlusive therapy is a major problem for the ophthalmologist and family of a unilaterally aphakic child. For such children, epikeratoplasty and secondary IOL implantation are the only alternatives to the abandonment of therapy. Generally, epikeratoplasty is recommended for children over the age of 1 year and is useful for cases of unilateral aphakia for which contact lenses are not possible because of intolerance or socioeconomic conditions that discourage successful contact lens use. Also, it is particularly useful for unilateral traumatic aphakia and may be used if corneal scars are present as long as the visual axis is not involved. In cases of bilateral aphakia for which spectacle therapy has been unsuccessful, epikeratoplasty may be used bilaterally to minimize the risk of amblyopia from optical noncompliance.
Epikeratoplasty for keratoconus was designed to reinforce the cornea and flatten the cone in keratoconus patients intolerant of contact lens wear and who do not have central or paracentral scarring within 1?mm of the visual axis.    Exception may be made for those who have Down syndrome, for whom the advantages of an extraocular procedure may outweigh the disadvantages of a “less than perfect” visual result. Although correction can be attempted for any corneal steepness, some observers found that patients who had cones <60D seemed to benefit more from epikeratoplasty than those who had steeper cones. Vajpayee and Sharma reported a postoperative spectacle-corrected visual acuity of 6/12 or better in 80% of patients using fresh or McCarey-Kaufman preserved, manually dissected donor lenticules. Epikeratoplasty was successfully expanded for other ectatic corneal disorders, such as keratoglobus  and pellucid marginal degeneration.
Epikeratoplasty for myopia was developed for patients intolerant of spectacles and contact lenses who had severe myopia of up to 30D.  Its use has declined sharply because of associated problems, such as extended recovery period, unpredictability, instability of correction, and epithelial changes that often mandate removal of the lenticule.
All epikeratoplasty lenticules used in the original studies were commercially prepared. The corneal tissues were supplied by eye banks and stored in McCarey-Kaufman medium for 4–14 days prior to processing. The donor tissue (Bowman's layer and anterior stroma) is stained with a temporary
dye to enhance visibility, lyophilized, lathed to a specified power (based upon the patient's spherical equivalent corrected to the corneal plane—with the exception of keratoconus, which was lathed to planopower), placed in a vacuum-sealed container, and shipped to the surgeon within 2 months of the date of manufacture ( Fig. 19-4 ). Several modifications were explored in an attempt to improve epikeratoplasty. Erlich and Nordan developed a nonkeratectomy version of the procedure in which a knife-edged lenticule was slipped into an angled slit made in the peripheral cornea and then sutured. Rostron et al. worked with corneal tissue glues in an attempt to eliminate sutures from the procedure. Goosey et al. reported 20 cases of myopic epikeratoplasty without a keratectomy in an attempt to avoid the astigmatism and scarring associated with the standard techniques. The most recent designs use an 8.5?mm donor lenticule for aphakia and myopia and a 9.0?mm lenticule for keratoconus.
In epikeratoplasty, first the visual axis is marked and the greater part of the corneal epithelium removed, except for a small central area that contains the visual axis mark and a small peripheral cuff. Next, a Hessburg-Barron trephine (7.0?mm for aphakia and 8.5?mm for keratoconus) is centered on the visual axis and a keratotomy performed to 0.20–0.30?mm in depth. After keratotomy, the central epithelium is removed, and an annular keratectomy approximately 0.5?mm in diameter is made using Vannas scissors central to and continuous with the keratotomy, which allows fixation of the lenticule and migration of the host keratocytes into the acellular lenticule. After the keratectomy, a spatula is passed peripherally at the level of the base of the keratectomy to create a 360° lamellar pocket approximately 1.0?mm peripheral to the initial keratotomy. The precarved lenticule, which has been hydrated in a balanced salt solution enhanced with an antibiotic such as gentamicin 100?mg/ml for 20 minutes, is placed on top of Bowman's membrane. For the treatment of aphakia or myopia, the lenticule is sutured into the lamellar pocket. A 0.5?mm oversize lenticule is used to flatten the host cornea in the management of keratoconus. However, a 1.5?mm oversize graft is optimal for other epikeratoplasty treatments, to eliminate a flattened host cornea and the induction of undesirable refractive changes.
The preferred suture technique is to use 16 uninterrupted 10-0 nylon sutures. Some surgeons have advocated “no-stitch” techniques to reduce some of the problems induced by lenticule suturing. Topical antibiotics (e.g., Polysporin ophthalmic ointment three times a day) are used until reepithelialization is complete.
Figure 19-4 Epikeratoplasty lens modifications. The design was modified extensively away from a keratectomy to allow a tapered edge to be inserted into a keratotomy.
Topical corticosteroids (e.g., prednisolone acetate 1% three times a day) are used to prevent premature suture vascularization and loosening, particularly important after epikeratoplasty for keratoconus, in which early loosening and removal of sutures may result in the development of irregular astigmatism.
In uncomplicated cases, all sutures are removed after 2–3 weeks for pediatric aphakia and after 8 weeks for adult aphakia and myopia.      For keratoconus, better results may be obtained if the sutures are retained for 4–6 months. However, vascularized sutures are removed promptly to avoid reduced prognosis or potential future penetrating keratoplasty.
Clinical Results and Complications
In addition to persistent epithelial defects, complications after epikeratoplasty include interface opacification, later interface scarring and opacification, infectious keratitis, sterile ulceration of the lenticule and recipient stroma, steepened recipient cornea, and endothelial changes (attenuation of cells, irregular shape, and decreased density with poor interdigitation). Other major complications of epikeratoplasty for keratoconus include persistent irregular astigmatism caused by premature removal or loosening of sutures and residual myopia. Although secondary refractive procedures such as radial keratotomy or relaxing incisions have produced improvement in some cases, it is often best to proceed to penetrating keratoplasty in situations in which the visual results are suboptimal. In developing countries, where there is a paucity of quality donor material, tissue unsuitable for penetrating keratoplasty because of poor epithelial quality, inadequate endothelial cell count, length of storage time, or other reasons can be used for epikeratoplasty. Vajpayee and Sharma reported a shorter recovering time in epikeratoplasty using fresh, manually dissected corneas instead of cryolathed and lyophilized corneas.
Most large series report an anatomical success of 95% in epikeratoplasties for aphakic adults, with persistent epithelial defects and loss of graft clarity being the major reasons for graft failure. The two major functional limitations are the rate of recovery of best-corrected visual acuity (BCVA) and the relatively poor contrast sensitivity. The anatomical and refractive results for pediatric aphakia are similar to those for adult aphakia.    Anatomical success may be as high as 95%, and refractive success (within 3D of emmetropia) is achieved in approximately 75% of eyes. Pediatric aphakia remains the lead indication for the use of epikeratoplasty.