Chapter 45
Epikeratoplasty: A Historical Perspective
MARK P. LESHER and DANIEL S. DURRIE
Main Menu   Table Of Contents

Search

HISTORY
SURGICAL TECHNIQUE
INDICATIONS
CONCLUSION
REFERENCES

The concept of using a surgical procedure to change the refractive power of the anterior corneal surface was developed by Barraquer in the 1960s and 1970s.1 The precursors of epikeratoplasty, keratomileusis and keratophakia, proved to be technically challenging and demanding of the surgeon because they required expertise in manufacturing a donor lenticule using the cryolathe. In the hands of experienced surgeons, the results were quite good. However, for these procedures to be performed by many surgeons, they needed to be simplified.
Back to Top
HISTORY
Kaufman2 and Werblin3 proposed epikeratoplasty as a simple procedure for the correction of aphakia in 1980. In epikeratoplasty, a donor corneal lenticule is frozen, shaped with a cryolathe, and sutured to the anterior corneal surface to provide the appropriate optical correction (myopic, plano, or hyperopic). Alternatively, the button may be lyophilized and stored in a vacuum container for later use. The advantage of epikeratoplasty over earlier procedures was that the lenticules could be prepared in a centralized location by a company (e.g., Allergan Medical Optics [AMO], Cryo-Optics) dedicated to lenticule production. This meant that the surgeon needed to master only the surgical procedure and not the use of the cryolathe.

During the 1980s, several multicenter national studies were sponsored by AMO to assess the efficacy of epikeratoplasty for several conditions: pediatric aphakia, adult aphakia, myopia, and keratoconus.4–7 The procedure was promoted as a fairly simple surgery that could be performed by most general ophthalmologists as an alternative to aphakic spectacles in the adult or for pediatric aphakia, or in lieu of penetrating keratoplasty for keratoconus. It was also promoted as a good technique for performing lamellar corneal patch grafts in cases of corneal thinning or perforation. Because the lenticules are not an economically viable product, they are no longer commercially available from AMO.

Back to Top
SURGICAL TECHNIQUE
The surgeon provided two pieces of information to the central tissue processing center to facilitate preparation of the donor lenticule: the patient's spherical equivalent of refraction at the corneal plane and the average central keratometry readings. The tissue was custom lathed for each patient and delivered to the operating surgeon. The tissue lens was removed from the vacuum container and rehydrated in balanced salt solution with antibiotic (gentamicin). The patient's optical center was located and marked with a needle or Sinsky hook. Centration was extremely important, especially in the cases of myopic epikeratoplasty. A donut of central corneal epithelium was then removed by a combination of mechanical and chemical debridement. The central 2 to 3 mm of corneal epithelium containing the centering mark were left intact temporarily. A Hessburg-Barron vacuum trephine was centered on the optical axis, and a 0.25-mm partial-thickness trephination was performed (Fig. 1) . An annular keratectomy was performed, in cases of keratoconus, to improve adherence of the epigraft to the host corneal stroma. The vertical trephination was undermined approximately 1 mm peripherally with a Suarez spreader or comparable instrument to allow the edge of the graft to seat nicely in the keratectomy. The residual central host epithelium was then removed mechanically and the graft bed was sometimes treated with absolute alcohol or 4% cocaine to remove any residual epithelial cells. The cornea was irrigated copiously with balanced salt solution, and the rehydrated epikeratoplasty lenticule was sutured into position with 16 to 24 interrupted 10-0 nylon sutures. Careful attention was paid to making equal bites on the donor and recipient sides. The ideal suture tension should be equal in every direction. The knots were trimmed and buried just beneath the surface of the recipient to make suture removal easier. The graft edges were then tucked into the peripheral keratectomy, and subconjunctival antibiotic and/or steroids were administered.

Fig. 1. Annular keratectomy techniques: steps for adult aphakia. A. Trephine keratotomy, 0.3 mm deep. B. Annular keratectomy, 0.3 mm deep and 0.5 mm wide. C. Spreading technique, 1 mm undermined. D. Lens edges designed to fit keratectomy. (Durrie DS, Brightbill (eds): Corneal Surgery, 2nd ed. St. Louis, CV Mosby, 1993)

Back to Top
INDICATIONS

PEDIATRIC APHAKIA

Epikeratoplasty was indicated for aphakia in children young enough to realize benefits from occlusion therapy (i.e., younger than 9 years of age). In most cases it was used as an alternative to an aphakic contact lens in a child with a traumatic or congenital cataract. Results in the pediatric population were reasonable, with the majority of patients in several studies achieving “useful” vision.8–10 The main difficulties with the procedure included mild graft haze, which increased the difficulty of amblyopia therapy, difficulties with centration, and inaccuracy in selecting lenticule powers in younger children. Advantages of the procedure included the ability to remove and replace the lenticules if the refractive error changed with age. The early success of intraocular lens (IOL) implants in children has resulted in a shift toward using IOLs rather than epikeratoplasty lenticules in contact lens-intolerant aphakic children.

ADULT APHAKIA

Posterior chamber IOL implantation is the preferred method of aphakia correction in the adult population. This is normally done in conjunction with cataract extraction at the time of lens removal. Certain situations exist in which lens implantation is not possible or advisable. Such conditions include lack of posterior capsule support, a disorganized anterior chamber that will not support an IOL, and compromised endothelial function secondary to aging or dystrophic processes. Aphakic contact lens wear is another alternative to IOL implantation. However, contact lens wear is frequently less successful in the typical cataract population because of tear film deficiency and patient difficulties with lens insertion and removal. Epikeratoplasty was proposed as a way to avoid an intraocular procedure in situations where lens implantation was difficult or where aphakic contact lens wear was not well tolerated.3,11,12 The development and improvement in secondary lens implant techniques (e.g., iris-fixated posterior chamber intraocular lenses, scleral-fixated intraocular lenses) have made these the preferred surgical techniques for correcting adult aphakia, and epikeratoplasty is rarely indicated.

MYOPIA

Prior to the acceptance of newer refractive procedures, such as radial keratotomy and the excimer laser, epikeratoplasty was promoted as an alternative to contact lenses or spectacles in patients with more than 6.0 diopters of myopia. The refractive results in myopic patients were variable and highly dependent on the expertise of the surgeon.6,13 Irregular astigmatism resulted in a loss of best-corrected visual acuity after surgery. The use of epikeratoplasty in the myopic population added to knowledge in the areas of graft centration, postoperative glare, and corneal topography. However, the development of the excimer laser and the increasing interest in radial keratotomy have resulted in epikeratoplasty being performed less and less frequently for myopia. Computer-controlled excimer laser ablation of the anterior corneal surface appears to offer a much more predictable way to flatten the central cornea than did epikeratoplasty.

KERATOCONUS

Epikeratoplasty was used as an intermediate step between contact lens wear and penetrating keratoplasty in the management of keratoconus. Indications included patients with mild to moderate keratoconus without apical scarring who were having difficulties with contact lens wear. A plano graft was sutured tightly over the central cornea to flatten the cone and reduce myopia.14,15 This procedure should theoretically have no risk of immune rejection because no donor antigens come into contact with the host's immune system. Most surgeons have abandoned epikeratoplasty for the treatment of keratoconus in favor of full-thickness keratoplasty. Improvements in keratoconus contact lens fitting have allowed surgical treatment to be delayed in most cases. Lamellar keratoplasty with use of non-commercially prepared tissue remains an intermediate option in the treatment of keratoconus.

PATCH GRAFT

The Keratopatch (AMO, Irvine, CA) was a lyophilized plano-corneal lenticule that could be used to perform a lamellar wound “reinforcement” in an area of corneal thinning or perforation. It offered a readily available tissue patch that did not require hand carving, was predictable in thickness, and was surgically easy to use. Other techniques for dealing with small corneal perforations, such as tissue adhesive, are only stop-gap measures. The lack of availability of freeze-dried prepared corneal tissue is certainly a loss for the ophthalmic surgeon. Hand-carved donor grafts can be used for this purpose, but such tissue is often in high demand for penetrating keratoplasty. The eye-banking system may want to address the needs of the corneal surgeon in this area by developing a suitable replacement for the Keratopatch.

Back to Top
CONCLUSION
Because of the lack of economic viability, epikeratoplasty lenticules are no longer commercially available from AMO in the United States. Epikeratoplasty was a relatively simple ophthalmic surgical procedure that was used for the correction of pediatric and adult aphakia, keratoconus, and myopia during the 1980s. The results varied and were frequently related to the surgeons' experience with the procedure. Improvements in intraocular lenses and secondary IOL fixation techniques have allowed secondary lens implantation to replace epikeratoplasty as the procedure of choice for correcting aphakia. The excimer laser now offers a technically simpler and more reliable method for correcting myopia. Lamellar keratoplasty remains a useful procedure in cases of corneal thinning or perforation and for selected keratoconus patients. The need for commercially prepared lyophilized corneal tissue still exists and may be addressed by the national eye-banking community in the future.
Back to Top
REFERENCES

1. Tucker DN, Barraquer JI: Refractive keratoplasty: Clinical results in 67 cases. Ann Ophthalmol 5:335, 1973

2. Kaufman HE: The correction of aphakia. Am J Ophthalmol 89:1, 1980

3. Werblin TP, Kaufman HE, Friedlander MH et al: A prospective study of the use of hyperopic epikeratophakia grafts for the correction of aphakia in adults. Ophthalmology 88:1137, 1981

4. Morgan KS, McDonald MB, Hiles DA et al: The Nationwide study of epikeratophakia for aphakia in children. Am J Ophthalmol 103:366, 1987

5. McDonald MB, Kaufman HE, Aquavella JV et al: The Nationwide study of epikeratophakia for aphakia in adults. Am J Ophthalmol 103:358, 1987

6. McDonald MB, Kaufman HE, Aquavella JV et al: The Nationwide study of epikeratophakia for myopia. Am J Ophthalmol 103:375, 1987

7. McDonald MB, Kaufman HE, Durrie DS et al: Epikeratophakia for keratoconus. Arch Ophthalmol 104:1254, 1986

8. Morgan KS, Stephenson GS, McDonald MB, Kaufman HE: Epikeratophakia in children. Ophthalmology 91:780, 1984

9. Morgan KS, Asbell PA, McDonald MB et al: Preliminary visual results of pediatric epikeratophakia. Arch Ophthalmol 101:1540, 1983

10. Arffa RC, Marrelli TL, Morgan KS: Keratometric and refractive results of pediatric epikeratophakia. Arch Ophthalmol 103:1656, 1985

11. Werblin TP, Kaufman HE, Friedlander MH et al: Epikeratophakia--The surgical correction of aphakia--Update 1981. Ophthalmology 89:916, 1982

12. McDonald MB, Koenig SB, Safir A et al: Epikeratophakia: The surgical correction of aphakia update: 1982. Ophthalmology 90:668, 1983

13. McDonald MB, Klyce SD, Suarez H et al: Epikeratophakia for myopia correction. Ophthalmology 92:1417, 1985

14. Kaufman HE, Werblin TP: Epikeratophakia for the treatment of keratoconus. Am J Ophthalmol 93:342, 1982

15. McDonald MB, Koenig SB, Safir A, Kaufman HE: Onlay lamellar keratoplasty for the treatment of keratoconus. Br J Ophthalmol 67:615, 1983

Back to Top