Peter S. Hersh

Corneal Topography of Phase III Excimer Laser Photorefractive Keratectomy: Characterization and Clinical Effects

PURPOSE To define qualitative patterns of corneal topography after excimer laser photorefractive keratectomy (PRK), assess changes in patterns, associations with clinical outcomes, and the accuracy of videokeratography in predicting results, and define quantitatively the optical zone contour. METHODS Computer-assisted videokeratography data obtained from 181 patients after PRK was analyzed. Topography patterns at two time points were characterized, and associations with clinical outcomes were tested. Power change predicted by topography was compared with refractive change, and cross-sectional power contours were analyzed. RESULTS Seven topography patterns were defined. At 1 year, 58.6% of corneas showed a homogeneous topography, 17.7% showed a toric-with-axis configuration, 2.8% showed a toric-against-axis configuration, 13.8% showed an irregularly irregular topography, 2.8% showed a keyhole/semicircular pattern, and 4.4% showed focal topographic variants. No central island patterns were found. Of the maps, 41% changed over time. Uncorrected vision, predictability, and patient satisfaction were best in the homogeneous group. Astigmatism increased in the irregular and toric-against-axis groups and decreased in the toric-with-axis group. There was no relation of topography pattern to best-corrected vision or subjective glare/halo. Cross-sectional power profiles showed a homogeneous power change for the central 3 mm with a diminution in correction toward the periphery. The topography unit tended to overestimate refractive change for corrections of 5 diopters or less and underestimate the change for corrections greater than 5 diopters. CONCLUSIONS Topography patterns after PRK are identifiable, time dependent, and may affect clinical outcomes. Understanding the actual corneal optical contour resulting from PRK may aid in improving both laser techniques and optical results in the future.

Corneal Topography of Phase III Excimer Laser Photorefractive Keratectomy: Optical Zone Centration Analysis

PURPOSE To determine the amount of optical zone decentration in patients who have undergone excimer laser photorefractive keratectomy (PRK) and assess associations of both decentration and optical zone size with clinical outcomes. METHODS Optical zone centration in 185 patients after PRK was analyzed using computer-assisted videokeratography. A comparison of decentration among the five study centers was performed. Associations of clinical outcomes with procedure decentration and optical zone size were assessed. RESULTS Decentration from the pupil center ranged from 0.00 to 1.44 mm (mean, 0.46 mm): 21.8% were decentered 0.25 mm or less, 42.5% > 0.25 mm and < or = 0.50 mm, and 97.1% < or = 1.00 mm. In both eyes, the average decentration from the pupil center was located inferonasally. Decentrations among the five study centers were significantly different. Decentration was associated with attempted refractive correction, change in keratometric cylinder, and patient satisfaction. There was a trend toward worse postoperative uncorrected visual acuity with greater decentration but no association with best-corrected vision, predictability, or refractive astigmatism. No significant relation was found between decentration and glare/halo ranking; however, three of six patients with 1.00 mm or greater of decentration demonstrated a high glare/halo grade. Although optical zone size was not associated with glare or halo, subjective patient satisfaction was greater with a 5.0-mm optical zone than with a 4.5-mm optical zone. CONCLUSIONS Centration is an important surgeon-controlled variable in excimer laser PRK. Decentration of excimer laser refractive procedures was found to be nonrandom and may be influenced by preoperative pupil management. Moreover, the amount of decentration may influence clinical outcomes. Improved techniques and centering procedures on nonmiotic pupils may improve future results.

Urban Eye Trauma: A One-year Prospective Study

PURPOSE The authors conducted a 1-year prospective study investigating the demographics, causation, and treatment of eye trauma in an urban population at one medical center. METHODS All patients sustaining eye injuries who were evaluated by the ophthalmology service over a 1-year interval were included. A formal questionnaire was completed with demographic data and details of the injury being obtained. An ophthalmologic examination was performed on each patient, and examination findings, diagnostic tests obtained, diagnosis, and treatment were recorded and analyzed. RESULTS This study included 584 eye injuries. Three hundred seventy-one injuries (70%) occurred in males and 159 (30%) in females. The average age was 30.5 years; 110 (21%) patients were pediatric. Sixty-two percent of all patients presented within 24 hours of their injury. Thirty-seven percent of all injuries occurred in the street, 31% at home, and only 13% at the workplace. For those older than 65 years of age, 48% of injuries were the result of a fall. Sixty percent of all eye injuries were caused by blunt trauma. Only 42 (8%) patients wore eye wear at the time of their injury. Diagnoses and management were recorded. CONCLUSIONS The inner city population is more likely to sustain eye trauma as the result of an assault and is less likely to be involved in a work- or sports-related injury. Given poor compliance with outpatient management and follow-up, aggressive primary management may be indicated to optimize visual outcome.

Corneal complications associated with the use of crack cocaine

BACKGROUND A case series of patients with corneal complications associated with crack cocaine use is presented. Patients had infectious keratitis or sterile epithelial defects. METHODS Entry criteria into this series included the presence of an infectious corneal ulcer or sterile epithelial defect after the patient used crack cocaine routinely. Patients were prospectively identified from July 1, 1989 to June 30, 1991. RESULTS Fourteen patients with crack-related corneal problems were identified. In 10 patients with infectious corneal ulcers, both bacterial and fungal organisms were isolated, and patients were treated with appropriate antimicrobial therapy. The group of patients with sterile corneal epithelial defects were seen after they had rubbed their eyes vigorously after crack cocaine use. The epithelial defects were treated and healed without complication. CONCLUSION Crack cocaine users appear to represent a unique subset of young patients predisposed to infectious keratitis and corneal epithelial defects. A number of hypotheses are offered to explain this effect. Both ophthalmologists and the general public should be aware of these severe corneal problems associated with the use of crack cocaine.