Effect of collagenase inhibitors on corneal haze after PRK.

The aim of the study was to determine whether collagenase inhibitors reduce corneal haze after photorefractive keratectomy (PRK). Inhibition of the initial removal phase of healing may limit the subsequent repair and replacement phases responsible for haze and regression. Thirty rabbits received -6.00D 5 mm right PRK. They were randomized to five treatment groups: G. cysteine, G. ethylene diamine tetra-acetic acid (EDTA), G. ascorbate, Oc. tetracycline or no drops. Dichlorotriazinyl aminofluorescein (DTAF) was applied to the wound immediately after surgery in two rabbits of each group, to delineate newly-synthesized from original tissue. Corneal haze was assessed by a video-linked frame grabber with computerized grey scale analysis. Corneas were taken for histology at 1 or 3 months post-operatively. Corneal haze was not significantly different between the treatment groups and controls. The severity of the histological changes varied between individuals. Within the ablation zone the epithelium was on average 10% thicker (3--4 micro m) than outside, and in some rabbits there were irregularities of the epithelial--stromal junction. The new subepithelial tissue had a mean depth of 7.8 micro m, and the superficial stroma was disorganized to a mean depth of 49 micro m. No particular treatment demonstrated significant benefits over controls; but of the treatments used, cysteine tended to produce the best results. Eyes treated with EDTA fared worst in most respects. The collagenase inhibitors used did not improve the outcome of PRK in rabbits. It remains to be determined whether firstly, the new more potent agents would have an effect, and secondly, whether collagenase inhibitors are of benefit in humans.

Treatment of band keratopathy by excimer laser phototherapeutic keratectomy: surgical techniques and long term follow up.

A series of 122 eyes with band keratopathy was treated by excimer laser phototherapeutic keratectomy (PTK), with a mean follow up of over 12.3 months (range 3 to 60 months). A single photoablation zone was used to remove the opacity over the visual axis in smooth surfaced band deposition. In eyes with reduced vision, an improvement was reported in 88% and in a series of 66 eyes mean Snellen visual acuity increased significantly (p < 0.05, t = 2.27). A reduction in glare was reported in 88% and in a series of 17 patients, visual contrast sensitivity (p < 0.01) and measurements of disability glare (p < 0.01) improved postoperatively. The mean hyperopic shift in 32 eyes at 6 months was 1.4 D (range 0-4.25 D). Multiple overlapping ablation zones, with mechanical debulking of large calcium plaques, were used to smooth the irregular corneal surface in eyes with rough bands. Ocular discomfort was improved in 95%. Band keratopathy recurred in nine eyes (8%) within 2 to 30 months (mean 12 months) of surgery, with silicone oil responsible in five eyes. Reablation was necessary in three eyes and performed successfully in all cases. Excimer laser PTK is a safe and effective outpatient treatment for band keratopathy.