Phototherapeutic keratectomy for recurrent erosion syndrome in anterior basement membrane dystrophy.

PURPOSE: To determine the outcome of patients who received phototherapeutic keratectomy (PTK) for recurrent erosion syndrome due to anterior basement membrane dystrophy (ABMD). DESIGN: A retrospective, noncomparative case series. PARTICIPANTS: Forty-eight eyes of 43 consecutive patients who underwent PTK for recurrent erosions occurring in ABMD at the Hunkeler Eye Center from 1991 to April 1995. All patients had previously failed at least one method of medical or surgical treatment for recurrent erosions and had slit-lamp findings of ABMD on initial evaluation. INTERVENTION: The eyes each underwent manual superficial keratectomy and PTK with the Summit Omnimed excimer laser. MAIN OUTCOME MEASURES: Data were analyzed by a retrospective chart review for 1, 3, 6, and 12 months for the 36 eyes with at least 12 months of follow-up data available. They were analyzed for preoperative and postoperative visual acuity, change in spherical equivalent, recurrence rate, and patient satisfaction. RESULTS: The preoperative mean visual acuity was not statistically significantly different at 1 month after PTK. Statistically significant improvement in mean visual acuity was present at 3, 6, and 12 months. Recurrence of symptoms of recurrent erosion was present in 5 (13.8%) of 36 eyes during the 12-month follow-up period, which was managed with repeat PTK over the area of the cornea initially treated with PTK; 1 of 5 required a third PTK treatment. All recurrences presented within 6 months of PTK or repeat PTK. The mean dioptric change in spherical equivalent was not statistically significant. Patient satisfaction levels after PTK for recurrent erosions in ABMD were assessed in 21 (58%) of 36 patients on a scale of 0 to 5 (5 = most satisfied); the mean response was 4.14 of 5. CONCLUSIONS: Phototherapeutic keratectomy is an effective treatment for recurrent erosions occurring in the setting of ABMD, is well tolerated, and may improve visual acuity. The rate of recurrence of erosions in ABMD treated with PTK is low during a 12-month follow-up period.

Classification of variable clinical response after photorefractive keratectomy for myopia.

BACKGROUND: Variation in healing response has been noted after excimer laser photorefractive keratectomy (PRK). METHODS: A retrospective analysis of 116 eyes that underwent PRK for myopia was performed. Standard surgical protocol and postoperative corticosteroid treatment were followed for all eyes. Scattergrams of achieved correction versus attempted correction at 6 months after surgery were analyzed. Subepithelial corneal haze was compared with refractive outcome. RESULTS: Three healing responses were observed. Normal responders (84.5%) showed a hyperopic overcorrection at 1 month with a gradual regression toward plano and good refractive outcome. Inadequate responders (11.2%) showed a pronounced early hyperopic overcorrection (greater than 1.50 diopters [D]) with minimal regression at 6 months. Aggressive responders (4.3%) displayed an early overcorrection with rapid regression toward myopia. Clear to trace subepithelial corneal haze was present at 6 months in 96% of normal and inadequate responders. Aggressive responders had more pronounced subepithelial haze at 6 months. CONCLUSION: Variation in the amount of subepithelial healing response occurs after excimer laser PRK. Abnormal healing responses may be detected early in the postoperative period by correlation of refractive error with the amount of subepithelial haze.

Relation of visual symptoms to topographic ablation zone decentration after excimer laser photorefractive keratectomy.

BACKGROUND: The authors used computer-assisted videokeratoscopy to analyze the relation of photorefractive keratectomy ablation zone decentration to subjective patient assessments of disturbing visual symptoms. METHODS: Ablation zone decentration was measured 1 month postoperatively. The study population was divided into two groups: group 1, patients whose ablation zone decentrations were less than 0.50 mm; group 2, patients whose ablation zone decentrations were greater than 0.50 mm. Visual symptoms including glare, rings or halos around lights and problems with night driving were scored preoperatively and 6 months postoperatively. The Hotelling T-square and chi-square tests were used. RESULTS: The mean decentration from the center of the ablation zone to the pupillary center was 0.30 mm and 190 degrees for group 1 compared with 0.66 mm and 198 degrees for group 2. The Hotelling T-square test showed a significant statistical preoperative/postoperative difference in group 1 (P < 0.03) for the halo symptom category. No other symptom category showed a significant statistical difference in either group for the mean scores. The Hotelling T-square test did not show a statistically significant difference between the two groups preoperatively to postoperatively regarding the mean scores of the individual patient differences for the three symptoms. The only significant statistical difference for the individual patient ratings preoperatively to postoperatively was for the halo symptom category (chi-square = 7.756; P < 0.03). CONCLUSIONS: Multivariate analysis did not show a significant statistical difference preoperatively between the two groups or postoperatively except for group 1 with regard to the halo symptom category. It appears from this study that ablation zone decentrations less than 0.89 mm from the pupillary center do not necessarily produce unwanted visual symptoms 6 months postoperatively.

Photorefractive keratectomy for residual myopia after previous refractive keratotomy.

Photorefractive keratectomy (PRK) was performed on 91 eyes of 71 patients who had previous radial keratotomy, radial combined with astigmatic keratotomy or astigmatic keratotomy alone (refractive keratotomy). Residual myopia, prior to photorefractive keratectomy, ranged from -1.50 to -8.00 D (mean -3.62) and cylinder from 0 to 2.25 D (mean 0.78). Uncorrected visual acuity was 20/40 or better in 89.7% at one year. At the 12 month follow-up 75.9% of patients were within +/- 1.00 D of intended correction.

Holmium:YAG laser thermokeratoplasty for hyperopia.

Holmium:YAG laser thermokeratoplasty (LTK), a procedure using a solid-state infrared laser to treat hyperopia, was performed on 10 patients in phase I and 16 patients in phase II--in a total of 29 eyes at the Hunkeler Eye Clinic. Phase II was redesigned after phase I results showed undercorrection and regression. The follow-up period ranged from 1 to 24 months (mean 10.9 months). A total of 79% of phase II patients were within +/- 1.00 D of intended correction at the 6-month visit. Looking at both phases together, no patients had J2 or better near vision preoperatively, but 75% had J2 or better at the 6-month visit. A total of 43% of eyes in phase II lost 1 line and 7% lost two lines of best spectacle corrected visual acuity due to induction of irregular astigmatism. The surgical challenges are to insure appropriate centration of the procedure about the optical axis. Concerns about regression and stability will be defined as these patients are followed through their 2-year visits.

Holmium:YAG laser thermokeratoplasty for hyperopia and astigmatism: an overview.

The holmium:YAG laser can be used to perform corneal collagen shrinkage and treat refractive errors. Studies are underway for the treatment of hyperopia by shrinking collagen in the peripheral cornea, which produces central and paracentral steepening. There is initial overcorrection followed by a regression of effect postoperatively, which appears to stabilize 4 to 6 months postoperatively. Refinement of current nomograms and definition of the amount of expected regression will enhance its accuracy. The holmium:YAG laser may be superior to radial thermokeratoplasty with a hot needle. Nearly 100 years ago, Lans was the first to report that heating of the cornea could induce collagen shrinkage with resultant corneal curvature changes. Various collagen shrinkage procedures have evolved since then. To date, the most well-known form of collagen shrinkage involves the hot needle and a technique developed by Fyodorov to do radial thermokeratoplasty for hyperopia. This article will review the current state of holmium:YAG laser technology and the advantages it may provide over radial thermokeratoplasty.

Philosophy and technique for excimer laser phototherapeutic keratectomy.

Phototherapeutic keratectomy (PTK) with the excimer laser has been shown to be effective in removing anterior corneal pathology and smoothing surface irregularities. Blocking agents are important in PTK. The techniques we present seek to balance therapeutic effect and refractive error change. Successful PTK depends on thorough preoperative assessment and attention to intraoperative detail. Clinical research has demonstrated that the excimer laser is an effective tool, not only for correcting myopic refractive errors, but also for treating various types of anterior corneal pathology. We present our PTK techniques that reflect recent refinements.

Topographical analysis of the centration of excimer laser photorefractive keratectomy.

A major advantage of myopic photorefractive keratectomy (PRK) is the precision with which the excimer laser ablates corneal tissue. But like other refractive surgery procedures, PRK must solve the problem of accurately centering the treatment zone. We present our technique for PRK centration with postoperative corneal topographic data on 110 patients from Phase IIB and III of the clinical trials. The distance between the center of the post-PRK flat zone and the corneal vertex was determined by topography in millimeters and meridian degrees. On average, treatment zones were decentered down and right 0.52 mm at 196.74 degrees; 92.73% were centered within 1.00 mm, while 57.27% were within 0.50 mm. The centration data were correlated to postoperative visual acuity as well as treatment zone diameter. Mean uncorrected visual acuity was 20/20 for decentrations up to 1.00 mm but fell to 20/30 for deviations greater than 1.00 mm. Best corrected acuity was also preserved below 1.00 mm but compromised above this level. No difference in decentration was found between 4.5 mm and 5.0 mm ablation zones. Our findings indicate that PRK centration is accurate within 1.0 mm in over 92% of cases and that visual acuity is relatively preserved despite deviations from perfect centration. Further technical improvements will enhance the accuracy of PRK.

Centration of excimer laser photorefractive keratectomy relative to the pupil.

The centration of excimer laser photorefractive keratectomy (PRK) is critical to the procedure's success. We evaluated PRK centration in 49 patients using the EyeSys topography system. Ablation zone centration was measured from the corneal vertex and from the pupillary center using the pupil-finding software. Centration was measured more accurately from the pupillary center (0.40 mm) than from the corneal vertex (0.44 mm). Right eyes were decentered less than left eyes. There was an unpredictable correlation between amount of decentration and postoperative visual acuities. The ability to measure centration of keratorefractive procedures precisely from the pupil is an important advance in topography technology.

Infectious keratitis and cyanoacrylate adhesive.

We studied three patients with infectious keratitis that occurred after cyanoacrylate gluing despite prophylactic antibiotic therapy. Two patients developed culture-positive bacterial ulcers, one caused by a methicillin-resistant Staphylococcus aureus and the other by Haemophilus influenzae. The third patient developed a fungal keratitis. Two patients required penetrating keratoplasty. Each infection and perforation was concealed by the opaqueness of the glue. The pain of the infectious ulcers may have been obscured by the ocular surface irritation and drying induced by glue. Tissue toxicity, microbial colonization, use of bandage lenses, and long-term broad-spectrum antibiotics may precipitate glue-related corneal infections. Masking of underlying infection and the development of resistant organisms should be considered when using this mode of therapy.