Miles H Friedlander

Epikeratophakia—The Surgical Correction of Aphakia: Update 1981

Epikeratophakia grafts used to rehabilitate vision in adult monocular aphakic patients intolerate of contact lens correction or not candidates for IOLs were studied prospectively. Thirty-two patients who entered this study between its inception in February 1980 through February 1981 were followed for at least eight months. Patients with normal visual potential before surgery had average visual acuities with spectacle overcorrection of 20/50 at four months, 20/40 at eight months, and 20/30 at one year. Few long-term complications were seen. Empirical modification of the lathing process has decreased the undercorrection from the 5.5 diopters seen in the early patients to the 1.0 diopter seen in the more recent patients. Problems with predictability are related to the behavior of preserved corneal tissue during the lathing and the healing of these lamellar grafts. This procedure is intended for aphakic patients of whom IOL and contact lens correction is not possible.

Epikeratophakia for Myopia Correction

Epikeratophakia is based on the principles of the Barraquer refractive procedures, with modifications that simplify the surgical technique and eliminate the use of the microkeratome by placing the donor corneal tissue lens on the anterior surface of the cornea. Procedures developed to permit freeze-drying the preshaped lens for storage enable these lenses to be obtained from a central source, freeing the surgeon from the complexities of the computer and the cryolathe. The correction of theoretically unlimited amounts of myopia is possible with these lenses. In 12 eyes that underwent the final epikeratophakia procedure, the average desired correction achieved was 98%.

The use of epikeratophakia grafts in pediatric monocular aphakia.

Epikeratophakia is a form of refractive surgery in which the recipients epithelium is removed and a pre-shaped donor lenticule is sutured to the patients cornea. Seventeen patients ranging in age from two months to 6.6 years received 19 epikeratophakia grafts for the correction of aphakic vision. The correction provided by the graft in combination with vigorous amblyopia therapy has yielded some improvement in vision in the 12 patients with successful grafts. This procedure may be particularly suitable for pediatric aphakic patients because it is extraocular and reversible and may be employed as a secondary procedure or in conjunction with cataract extraction. Only with longer follow-up of these and additional patients can these preliminary results be validated and the risk/benefit ratio of this procedure be assessed.

Keratophakia Using Preserved Lenticules

Using cats as an experimental model, we compared the clarity of fresh, glycerine-preserved and nitrogen-preserved lenticules (corneal stromal implants) in keratophakia. No difference in final clarity was observed and the change in corneal curvature was maintained. In six patients freshly cut lenticules were used; in nine patients liquid nitrogen-preserved lenticules were used. Again, no difference in final clarity or correction was noted. The use of preserved, precut tissue in keratophakia will make this technique available to the general ophthalmic surgeon.

MILD FORM OF MAROTEAUX-LAMY SYNDROME : CORNEAL HISTOPATHOLOGY AND ULTRASTRUCTURE

PURPOSE Maroteaux-Lamy syndrome is one of the mucopolysaccharidoses (MPSs) that is caused by the incomplete degradation and storage of dermatan sulfate. METHODS We describe a 49-year-old female patient with the mild form of the disease (MPS VI-B) who developed bilateral increasing corneal opacification and increased intraocular pressure after cervical-fusion surgery. After treatment of the increased intraocular pressure, she underwent a penetrating keratoplasty of her right eye. RESULTS The histopathologic and ultrastructural features of the corneal button were the accumulation of membrane-bound vacuoles containing fibrillogranular and lamellated material in keratocytes and endothelial cells and thinning of Descemets membrane with excrescences. CONCLUSION Our review of the literature reveals only two prior histologic studies of corneas affected by MPS VI B.

The Ultrastructure of Well-healed Lenticules in Keratomileusis

Two well-healed hyperopic keratomileusis homoplastica lenticules, one 4 years old, the other 5 months old, were removed from the same patient following postoperative complications of triplopia and aniseikonia. The lenticules were examined by light and electron microscopy. Both lenticules were repopulated with keratocytes throughout the lamellae. Degenerated keratocytes were observed in the 5-month-old lenticule and recipient stroma, and in the 4-year-old lenticule; no degenerated keratocytes were seen in the recipient stroma of the 4-year-old lenticule. These findings may have resulted from toxic constituents of the solutions used to preserve the donor cornea. The basement membrane was thickened in both lenticules. The epithelial cell layer was irregular in the periphery of the lenticule where Bowmans membrane was disrupted. These findings suggest that careful surgical technique that minimizes damage to Bowmans layer and basement membrane may promote more rapid epithelial healing. The histologic results suggest that the cause of this patients triplopia was irregular astigmatism.

Update on keratophakia.

Visual results are reported for 23 cases of keratophakia for the correction of surgical aphakia followed from 12 to 48 months. Seventeen of the 23 patients had final visual acuities of 20/40 or better. The average residual visual overrefraction was 1.87 +/- 1.79 diopters (mean +/- SE), with an increase of postoperative astigmatism of 1.70 +/- 1.33 diopters. Complications included interface deposits and peripheral epithelial deposits that did not interfere with vision. One patient had an anterior chamber penetration and subsequent penetrating keratoplasty, and two patients had lenticules removed because of corneal edema secondary to increased intraocular pressure. The major disadvantages of keratophakia are the complexity of the procedure and the time required (4 to 6 months) to achieve best-corrected spectacle visual acuity. However, because this procedure is extraocular, it is a better choice than secondary intraocular lens implantation for patients who are unilaterally aphakic and for the young patient.

Corneal Steepening in Human Eye Bank Eyes By Combined Hexagonal and Transverse Keratotomy

An interrupted 5 mm diameter hexagonal keratotomy was modified to include six paracentral transverse incisions to augment the central corneal steepening. This combined modified-hexagonal and transverse (or hexagonal-transverse) keratotomy was performed on human eye bank eyes to an estimated 85% corneal depth yielding a mean of 7.50 +/- 1.69 diopter increase in central keratometric power (P less than .001); this finding was confirmed by keratography. These results encourage further studies of this procedure and its potential to surgically correct mild amounts of hyperopia.

Intracorneal hemorrhage secondary to aphakic contact lens wear.

Two cases of intracorneal hemorrhage developing as a complication of aphakic contact lens use are reported. Patient 1 had a penetrating keratoplasty to restore vision and therefore the histologic examination could be performed on the corneal button. In patient 2 the contact lens use was discontinued with partial resolution of the intracorneal hemorrhage and the patient then underwent a secondary intraocular lens implantation with good visual results.

Corneal flattening by shallow circular trephination in human eye bank eyes.

Recent reports documenting central keratometric changes after removal of failed epikeratoplasty lenticules, compared to preoperative keratometry measurements, suggest that the annular corneal wound alters corneal curvature. Central corneal steepening has also been reported following circular and hexagonal keratotomy. We performed standard epikeratoplasty trephination with a Hessburg-Barron suction trephine followed by a peripheral lamellar spreading keratotomy on seven human eye bank eyes to determine the effect of these incisions on corneal topography. In seven human eye bank eyes, the mean acute central keratometric flattening from the shallow trephine incision was 2.81 D (SD 2.28, P = .017), with no significant change in keratometry due to peripheral lamellar spreading (P = .916). Computerized numeric and three-dimensional graphic analysis of the keratographs demonstrated this central topographic flattening. Further studies are needed to investigate the reversibility of host corneal changes induced by epikeratoplasty procedures.