Refractive Surgery

The desire for good unaided vision or sheer hatred for any visual aids (glasses or contact lenses) was the original motivation for refractive surgery. However, surgery is surgery with risks and a degree of unpredictability. The Authors conducted a study on a small series of 80 patients who had Photorefractive keratectomy (PRK) in the early 90s. Their 4-5mm ablation was done with a first generation iris-diaphragm Excimer laser machine. RESULTS: Although 19% were dissatisfied with the visual result, only about 12% initially had RGP contact lens for residual myopia, or irregular astigmatism. The other 7% rejected lenses. The minimum post-operative period for lens fitting was 6 months. Majority were fitted after 12 months which ensured corneal and refractive stability. Pre-PRK refraction ranged was -1.50 to -7.50 and post-PRK was -1.00 to -6.00. Best lens base curve was 1.25D steeper than flattest K or 0.50D steeper than mean K. Overall size was 9.20 to 10.00mm. However 50% were later re-fitted with soft lenses to promote comfort. There was one case of Central corneal steepening; two cases of flattening; three lens failures and four retreatments. The group would have had pre-PRK keratoconus screening. 80% of those fitted had 20/20 vision with 14 hours of wear, and 20% suffered a loss of Snellen’s BCVA due to haze. Keratoscopy, Pachymetry, refraction and slit-lamp microscopy yielded no interesting results. CONCLUSION: No unique fitting parameters was required by these modified corneas and no significant adverse effect observed not even the once dreaded ‘epitheliopathy’. The relative ease of fitting may continue to reduce RK preference over PRK. Several patients abandoned lenses or had more surgery. The argument of vaulting the ablated area with RGP lenses could not convince half of the study population to endure RGP instead of switching to soft lenses. A larger and longer series with wider ablation, newer machine and techniques is needed.

Chris O Imafidon PhD, FRSH
Cambridge, England.

Refractive Surgery

Purpose:

Previous reports demonstrate morning-to-evening changes in ophthalmic measurements at 3 months, 1 year, and 4 years after radial keratotomy. The authors determine whether diurnal change in refractive error persists 11 years after radial keratotomy surgery in the Prospective Evaluation of Radial Keratotomy (PERK) study.

Methods:

Seventy-one patients were examined in the morning and evening a mean of 11.1 +/- 0.6 years (range, 10-12.7 years) after undergoing radial keratotomy under a standardized protocol using a diamond blade.

Results:

Between the morning and evening examinations, the mean change in the spherical equivalent of refraction was a 0.31 +/- 0,58-diopter (D) increase in minus power in first eyes. Thirty-six (51%) eyes had an increase in minus power of the manifest refraction of 0.50 to 1.62 D; 22 (31%) had a change in refractive cylinder power of 0.50 to 1.25 D; 9 (13%) had a decrease in uncorrected visual acuity of two to seven Snellen lines; and 25 (35%) showed central corneal steepening measured by keratometry of 0.50 to 1.94 D. Two (3%) eyes lost two lines of spectacle-corrected visual acuity, whereas one (1%) eye gained two lines. In patients whose both eyes underwent surgery, a high degree of symmetry was observed in morning-to-evening refractive change.

Conclusion:

In some patients after radial keratotomy, morning-to-evening change of refraction and visual acuity persists for at least 11 years, although in most patients the magnitude of this change is small. Thus, diurnal fluctuation may be a permanent sequela of radial keratotomy in some individuals.

Authors' Abstract, Ophthalmology
Los Angeles, CA

Refractive Surgery

The authors performed corneal specular microscopy on 106 patients 12-55 months post PRK. There were two groups of patients. Group I included 35 eyes (32 patients) who had measurements taken preop and postop. The average endothelial cell counts were 2950 preop and 2907 postop. Group II participants had unilateral PRK (100 patients). In this group, postop measurements were performed with the count in the treated eye being 2912 and the untreated eye with 2922. The only significant finding was found in group II: the untreated eye had more polymegathism than the PRK eye. The authors suggest this is secondary to continued contact lens wear in the unoperated eye. Of note, one patient in group I had a 54% worsening of the mean coefficient of cell area (polymegathism) while one had a 35% increase.

The conclusion drawn is that PRK does not cause endothelial damage. This may be true for the population as a whole but longer follow-up is needed to ensure there is not a large subset of patients who do develop changes. I highly recommend you read this article with its discussion by Perry Binder, MD and form your own opinions.

Raymond G. Magauran III, MD
Buffalo, New York

Refractive Surgery

Discussion:

Newer RK techniques that have larger optical zones and incisions not extending to the limbus have been reported in cadaver studies to have similar tensile strength as an unoperated eye. PRK may indeed be more advisable in persons at higher risk for trauma but the degree of myopia, planned surgical technique and surgeon skill also play significant roles when evaluating a patient for a refractive procedure.

Raymond G. Magauran, M.D.
Buffalo, New York

Refractive Surgery

This article attempts to compare corneal abrasion treatment modalities: pressure patching versus treating with a bandage contact lens with and without the concomitant use of the non-steroidal anti-inflammatory drug (NSAID) ketorolac tromethamine (Allergan's Acular). 47 consecutive patients with small traumatic corneal abrasions were prospectively randomized in a single-masked, controlled clinical trial. The patients were divided into three groups: (1) pressure patching, (2) a bandage contact lens (CTL) with placebo (Tears Plus) QID, and (3) a bandage CTL with Acular QID. The patients in the two CTL groups also used Polytrim drops QID.

Results showed that there was no significant difference in the healing time, photophobia, redness, ocular irritation, headache or tearing of the three groups. However, there was significantly less pain in the group that received a bandage CTL and Acular. Also, the ability to return to normal activities in both contact lens groups was significantly quicker compared with the pressure-patch group.

The authors make a point of comparing the expenses of treating a corneal abrasion with a patch versus with a bandage CTL and NSAID drops. While the latter may seem more expensive, they note that patients of both CTL groups were able to return to work an average of 0.5 days sooner than those in the patch group did. They go on to calculate an increased wage earning potential of $51.88 daily per patient treated by a bandage CTL (based on $11.58 average hourly wage in the US) thereby offsetting the $17.00 cost of the bandage CTL plus NSAID drops.

Although the article demonstrates that the use of bandage CTLs with NSAID drops seems to be an effective form of treatment for corneal abrasions, the authors admit that the number of patients in each group was relatively small. They suggest that if more patients were included, the results for pain reduction and ability to return to normal activities may have been more markedly significant between the three groups.

I use bandage CTLs in my practice for treating large abrasions and recurrent corneal erosions. I usually have the patient use a drop of TobraDex once or twice daily while wearing the contact lens. This has worked quite well for me. The authors of this paper point out that some unpublished data presented at the 1994 ARVO Annual Meeting suggest topical NSAIDs have an antibacterial effect as well as an ability to decrease the adherence of bacteria to contact lenses. I would like to see more research to substantiate these claims, because the use of two different drops (the NSAID and an antibiotic) with the bandage CTL as done in this study seems to be a disadvantage. It would be nice if we could leave off the antibiotic and just use the NSAID. Also, this study was supported in part by a grant from Allergan Pharmaceutical Company. A similar study comparing the results of various other NSAIDs would be welcomed.

Jeff Brant, M.D.
Buffalo, New York