Michael P. Vrabec

A Multicenter Trial of Photorefracti*ve Keratectomy for Residual Myopia after Previous Ocular Surgery

Purpose: The Summit Therapeutic Refractive Clinical Trial is a nine-center prospective, nonrandomized, self-controlled trial to assess the efficacy, stability, and safety of using a standardized technique of excimer laser photorefractive keratectomy (PRK) to correct residual myopia in eyes with previous refractive surgery or cataract surgery. Patients and Methods: Eligible eyes with a mean residual myopia of -3.7 ± 1.8 diopters (D) (range, -0.63 to -11.00 D) underwent PRK with a 193-nm excimer laser for myopic corrections between -1.50 and -7.50 D. Standardized settings were used for the ablation zone, ablation rate, repetition rate, and fluence. One hundred seven of the first 114 treated eyes were examined 1 year after PRK, with 98% of eyes having had refractive keratotomy and 2% having had cataract surgery. Results: One year postoperatively, the mean manifest spherical equivalent refraction was -0.6 ± 1.4 D (range, -6.50 to 2.50 D); 63% of eyes were within ±1.00 D of the attempted correction; and uncorrected visual acuity was 20/40 or better in 74% of eyes. Twenty-nine percent of eyes lost two or more Snellen lines of best-corrected visual acuity, and central corneal haze was moderate or severe in 8% of eyes. Conclusion: Excimer laser PRK is effective in reducing residual myopia after previous refractive and cataract surgery. However, it is less accurate than PRK in eyes that did not undergo surgery and is more likely to cause a loss of best-corrected visual acuity 1 year after treatment.

The Pathology of Posterior Amorphous Corneal Dystrophy

The youngest affected member of a family with a five-generation history of posterior amorphous corneal dystrophy underwent penetrating keratoplasty. The corneal button was studied by light and electron microscopy, representing the first pathologic description of this condition. Light microscopy demonstrated fracturing of the most posterior collagen layers of the stroma and focal attenuation of endothelial cells. Electron microscopy showed the collagen fibers in the most posterior stromal lamellae to be disorganized. Descemets layer was interrupted by a band of collagen fibers resembling stroma, and there was loss of endothelial cells. These findings suggest a developmental abnormality in the formation of the posterior stroma and Descemets membrane in posterior amorphous corneal dystrophy.

Lamellar keratoplasty performed with a corneal scleral button

Tissue for lamellar corneal surgical procedures is usually harvested from whole eyes. We describe a surgical technique for the rehabilitation of corneoscleral defects with lamellar keratoplasty in which the donor tissue is obtained from a preserved corneoscleral button instead of a whole globe. This technique is illustrated with a case involving the treatment of a limbal dermoid in a 26-month-old boy.

A surgical technique for the treatment of central corneal perforations.

BACKGROUND Generally, corneal perforations of 2 mm in diameter or greater are treated using graft material for tectonic support. A surgical technique for the primary repair of such perforations without the use of any additional tissue is presented. METHODS This procedure is demonstrated by a case report. The technique involves creation of an elliptical defect out of a circular one, thus allowing for primary closure, with the addition of glue. A definitive penetrating keratoplasty was subsequently performed with several important modifications described herein. RESULTS A water-tight closure was obtained with this technique for 1 month while the inflammation subsided. Preoperative visual acuity was light perception. One year postoperatively, it was count fingers at 8 feet with mild irregular astigmatism. CONCLUSION This technique is useful for perforations which are central, larger than 2 mm in diameter, and when corneal or scleral material is not readily available for patch grafting.

Another Possible Cause of Forceps-Induced Scratching of a Foldable Acrylic Intraocular Lens-Reply

In reply We read with interest the letter by Dr Fry. It is quite possible that a.12 forceps could be another source of scratch marks on an acrylic intraocular lens. In these cases, one would expect to see 1 line and not 2, as was described in our case. The modifications in Dr Frys technique are important, namely, to enlarge the wound as well as to avoid contact between the intraocular lens implant and a device that could scratch it.

A New Scleral Suction Trephine for Retrieval of Corneoscleral Donor Tissue

BACKGROUND Removal of donor corneo-scleral shell from a cadaver, leaving the remainder of the eye in place, has become a popular technique. Manual removal can result in excessive trauma to the corneal endothelium or an uneven scleral rim. METHODS We describe a new technique for corneal retrieval using a sceral suction trephine. RESULTS The scleral suction trephine was cut evenly in our eyebank study. There was no additional trauma to the endothelium and the scleral rim was regular. CONCLUSION Suction trephination of the sclera in retrieval of corneal donor tissue appears to be safe and effective.

Iowa PK Press for donor corneas--a comparative study of donor corneal shape.

BACKGROUND A new cornea press for cutting donor corneal buttons from the endothelial side, the Iowa PK Press, is described. Major modifications of the Bourne Press include a spring-activated piston without lateral sway, a centering device for a Teflon cutting pad, and the ability to accommodate a wider range of trephine sizes (6.2 mm to 10.0 mm). METHODS The Iowa PK Press was compared with the Bourne Corneal Press and trephination by hand in a series of 15 donor cornea trephinations. Measurements taken from photographs of the buttons included endothelial diameter, epithelial diameter, and edge angles. RESULTS The Iowa PK press cut buttons that had a slightly larger epithelial and endothelial diameter when compared to hand trephination (p < .05, analysis of variance) with less undercutting of the endothelial surface. There was no statistically significant difference in epithelial and endothelial diameters, eccentricity, or edge angles between the two presses. CONCLUSIONS The Iowa PK Press is more versatile than the Bourne Press in terms of the potential range of diameter of corneal buttons that can be created.