Daniel M. Taylor

A Refractive and Histopathologic Study of Excimer Laser Keratectomy in Primates

Using a 193-nm excimer laser, we produced wide-area, refractive keratectomies on 18 cynomolgus monkey corneas and followed them up for up to 18 months. All corneas developed some subepithelial haze by one month. Electron microscopy disclosed epithelial thickening, absence of Bowmans layer, and subepithelial activated fibroblasts surrounded by disorganized collagen. By six months, the haze faded to a variable degree, the epithelium regained normal thickness, and the collagen was more organized. Persistent corneal haze at 12 months in some corneas correlated with electronlucent spaces in the subepithelial zone. Corneas were 90 microns thinner centrally two weeks after myopic ablation, but returned to preoperative thickness by six months. Myopic flattening and hyperopic steepening of 6 diopters were targeted, and over 7 diopters of each were achieved initially. Regression of induced curvature stabilized over several months. At 18 months, 4.4 diopters of myopic flattening and 5.2 diopters of hyperopic steepening remained.

Human Excimer Laser Lamellar Keratectomy: A Clinical Study+++

The first ten blind human eyes in the United States to receive excimer laser (ArFl 193 nm) lamellar keratectomy (reprofiling) are presented. Seven of these patients were followed 6 to 12 months after ablation. All eyes are grossly clear in the region of ablation. Results of slit-lamp examination of all flattened ablated areas show mild superficial haze at the epithelial/stromal interface. This haze might not interfere significantly with vision in patients 7 to 10. Serial pachymetry and keratometry measurements, refraction, and digital keratoscopy show a progressive filling in of the excavated area by approximately two thirds but a loss of initial diopteric correction of only one third. Histopathologic analysis was obtained for four eyes. Transmission electron microscopy of three eyes enucleated 3 to 12 days after ablation shows 40-microns ablation depths through Bowmans layer and superficial stroma with minimal adjacent tissue damage and no inflammatory cells. The epithelium is increased in thickness by 50%, and firmly attached to the underlying stroma. A 4-month postablation specimen shows keratocyte activation with increased protein synthesis (presumed collagen and ground substance).

Pseudophakic Bullous Keratopathy

Pseudophakic bullous keratopathy (PBK) is a relatively new disease that is rapidly becoming the prime indication for penetrating keratoplasty. From 1977 thru 1981 we performed 81 corneal transplants on 66 eyes for this condition. In our experience, the incidence of PBK, with iris-supported lenses, is five times greater than aphakic bullous keratopathy (ABK). A series of 800 intracapsular cataract extractions (ICCE) with implantation of iris-supported lenses (1975-1979) were reviewed. Thirty-four patients (4.3%) developed PBK (average two years after surgery). In a series of 3,000 simple ICCEs (1955-1980), 24 patients (0.8%) developed ABK. Etiologic factors, methods of prevention, and the results of penetrating keratoplasty are considered. PBK following ICCE is a serious disease entity, usually of multifactorial origin. Though 88% of the patients have clear grafts, a high incidence of associated posterior segment disease tends to nullify the visual result. Planned extracapsular cataract extraction and posterior chamber lens insertion (1979-1982) has reduced our incidence of PBK to 0.3% (1/300). These results are promising but premature.

Pseudophakic Cystoid Maculopathy: A Study of 50 Cases

The incidence of clinical cystoid macular edema (CME) in routine cataract surgery is about 2%. Clinically significant pseudophakic maculopathy has a higher incidence and is more severe. Fifty cases of CME following intracapsular cataract extraction and intraocular lens implantation in a series of 821 consecutive cases were reviewed. The overall incidence of pseudophakic cystoid macular edema (PCME) was 6.1%. Several clinical observations were made: (1) Young patients, or those under 65, had a much higher incidence of PCME, approaching 20%; (2) chronic inflammation is responsible for pseudophakic cystoid maculopathy; (3) systemic steroid therapy of CME in the pseudophakic patient was beneficial in 80% of the cases, with a response within ten days; and (4) pseudophakic cystoid maculopathy is almost always recurrent and frequently requires maintenance suppression with daily steroid drops after recovery. Forty-four percent of these patients did not recover better than 20/40 visual acuity, suggesting that CME in the pseudophakic patient is not a benign, self-limited disease.

Aphakic cystoid macular edema. Longterm clinical observations

The incidence of clinically significant cystoid macular edema (CME) following cataract surgery has risen sharply with the widespread utilization of intraocular lenses. To evaluate the factors contributing to the incidence of CME, the senior author has divided 1808 of his own cataract cases into three groups according to procedures used: 1) intracapsular cataract extraction (ICCE) with no lens implantation; 2) ICCE with implantation of an iris-supported lens; and 3) extracapsular cataract extraction (ECCE) with implantation of a posterior chamber lens. The incidence of CME in these three groups was 2%, 9.9%, and 1.2%, respectively. Contributing factors and visual outcome in all three groups are reviewed. It is concluded that many of the problems associated with ICCE and iris-supported lens implantation seem to be eliminated with the ECCE-posterior chamber IOL procedure. However, it is emphasized that careful longterm follow-up is required to determine safety.

Keratoplasty and Intraocular Lenses: Current Status

Present methods of treating combined corneal disease and cataracts in elderly patients are unsatisfactory, and multiple operative procedures may be required. From 1975 through 1978, 60 attempts were made to restore relatively normal optics and achieve rapid visual recovery with a single operative procedure consisting of keratoplasty, cataract extraction, and intraocular lens insertion in various combinations. As of this writing, there have been few complications, and 82% of the grafts are clear.

Reconstructive Keratoplasty in the Management of Conditions Leading to Corneal Destruction

Progressive corneal destruction of varying causes can result in pathologic changes that are incompatible with globe survival. Reconstructive keratoplasty and scleroplasty, in combination with other procedures, can be attempted as an alternative to enucleation, evisceration or spontaneous phthisis bulbi. The results of 50 reconstructive keratoplasties in 36 patients with severe corneal destruction are presented with one- to twenty-two year follow-up. Ninety-nine percent of the eyes were salvaged, 69% have clear grafts, 86% are visually improved and 51% achieved acuity of 20/100 or better.

Keratoplasty and Intraocular Lenses: Follow-Up Study

In an effort of explore new approaches with the possibility of improving on existing methods of managing problem cases with combined corneal disease and cataracts, 35 patients were treated by keratoplasty, cataract extraction, and intraocular lens implantation in various combinations or by cataract extraction and lens implantation without keratoplasty over the past two years. Twenty-four of twenty-six grafts have remained clear over a 3- to 21-month period of observation. The two failures have been successfully regrafted. Eleven patients received a penetrating keratoplasty, cataract extraction and intraocular lens with ten remaining clear. Eight patients with corneal disease and aphakia received a penetrating graft and intraocular lens with all grafts remaining clear. Seven patients with a clear graft received a subsequent cataract extraction and lens implantation with six remaining clear. Nine patients with endothelial dystrophy and cataracts were not affected by cataract extraction and lens implantation. The relatively high success rate, rapid visual rehabilitation, and reduction in the incidence of vitreous loss, vitrectomy, and delayed vitreous complications via the methods employed have, to date, proven encouraging. Caution is advised until data from a larger case series and long-term follow-up become available. Short-term success is directly related to technique. To achieve immediate success, the need for considerable experience in keratoplasty and lens implantation can not be overemphasized.

Experimental corneal studies with the excimer laser

ABSTRACT The excimer laser is potentially capable of achieving wide area central corneal reprofiling because of its extreme precision and limited penetration into adjacent tissues. A beam modifying system designed for this application is described. Initial clinical studies in monkeys and in ten human patients with blind eyes were performed. Long‐term clinical data and interim histologic analyses are available from these studies. The results indicate that following ablation with an ultraviolet laser in both humans and primates, the ablated tissue shows a normal healing reaction resulting in a mild to moderate stromal interface haze. The effects of this healing on best corrected vision must be elucidated through additional research. Some loss of refractive effect was seen early in the healing process with apparent stabilization.

Keratophakia: Clinical Evaluation

The keratophakia and keratomileusis procedures of Barraquer for the correction of aphakia have not gained acceptance in the United States because of thier inherent complexity and degree of difficulty. To determine the practicality, feasibility, and visual rehabilitation potential of these procedures, 13 secondary keratophakia operations were performed at a 500-bed community hospital between March 1980 and April 1981. The first ten cases are reported to allow 6- to 12-month follow-up. All patients in the series were resistant to contact lenses or were poor candidates for secondary intraocular lens implantation. The anatomic results were excellent. Complications were minimal consisting of surface drying problems in three patients related to the sudden steepening of the cornea or pseudo keratoconus effect. Seven patients achieved 20/30 to 20/40 vision with minimal spectacle correction. The keratophakia procedure of Barraquer shows promise and can be duplicated by experienced corneal surgeons, but is not yet a viable alternative to the use of primary intraocular lenses and continuous wear lenses for the general ophthalmologist.