Presented at the 1996 annual meeting of the Association for Research and Vision in Ophthalmology

Purpose. This study was designed to determine whether Alamar blue could be used to evaluate corneal endothelial cell viability in vitro. Methods. Alamar blue incorporates a proprietary redox indicator that changes color in response to metabolic activity. Primary rabbit endothelial cells were subcultured on 96-well plates at densities ranging from 1,250 to 40,000 cells per well. After 12 hours' incubation, Alamar blue was added to each well and absorbance measured hourly from 1 to 9 hours. Sodium azide-killed cells were used as a control. Alamar blue conversion was also compared with Conclusions. Alamar blue reduction measures endothelial cell viability and can readily differentiate cell concentrations. It demonstrates several advantages over [ 3 H]-thymidine: It can assay nonproliferating endothelial cell metabolism, it allows rapid assessment of large numbers of samples, it can differentiate endothelial cell concentrations, it is nontoxic, it is nonradioactive and allows for simple disposal, it is less cosdy, and it allows for continuous monitoring of endothelial cell metabolism and viability. Invest Ophthalmol Vis Sci. 1997; 38:1929-1933 L he ability to measure corneal endothelial cell viability in vitro accurately is important for applications that include measuring the toxicologic effects of intraocular drugs and irrigating solutions and basic physiologic studies of endothelial cell metabolism. Corneal endothelial cell viability has special importance in eye banks, for which assessment of cell viability is crucial to the development of storage media for donor corneas. The ideal method of measuring corneal endothelial cell viability would not be toxic to the endothelial cell, allowing continuous or repeated measurements; would have a range of sensitivity that allows measurement of degrees of viability; would not be de

Results of the Prospective Evaluation of Radial Keratotomy (PERK) Study 4 Years After Surgery for Myopia

The Prospective Evaluation of Radial Keratotomy Study is a nine-center clinical trial of a surgical technique to reduce simple myopia by making incisions in the cornea. There were 435 patients (one eye per patient is reported) enrolled in the study with a 91% follow-up rate at 4 years after surgery. After surgery, uncorrected visual acuity was 20/40 or better in 76% of eyes. Fifty-five percent of the eyes had a refractive error within ± 1.00 diopter; 28% were undercorrected, and 17% were overcorrected by more than 1.00 D. The width of the prediction 90% interval for the refractive change was 4.42 D, indicating a lack of predictability. The refractive error was not stable in some eyes; between 6 months and 4 years after surgery, 23% of eyes had a continued effect of the surgery of more than 1.00 D. For 323 patients with both eyes operated on, 64% stated they wore no optical correction. There were few serious complications. Eleven eyes (3%) lost two or three lines of best corrected visual acuity. Two eyes developed delayed bacterial keratitis without significant loss in best corrected visual acuity.(JAMA. 1990;263:1083-1091

Three-year Results of the Prospective Evaluation of Radial Keratotomy (PERK) Study

The Prospective Evaluation of Radial Keratotomy (PERK) study is a nine-center clinical trial of a standardized technique of radial keratotomy in 435 patients who had simple myopia with a preoperative refractive error between −2.00 and −8.00 diopters (D). The authors report results for one eye of each patient. The surgical technique consisted of eight incisions using a diamond micrometer knife with the blade length determined by intraoperative ultrasonic pachymetry and the diameter of the central clear zone determined by the preoperative refractive error. At 3 years after surgery, 58% of eyes had refractive error within 1.00 D of emmetropia; 26% were undercorrected and 16% were overcorrected by more than 1.00 D. Uncorrected visual acuity was 20/40 or better in 76% of eyes. The operation was more effective in eyes with a preoperative refractive error between −2.00 and −4.37 D. Between 1 and 3 years after surgery, the refractive error changed by 1.00 D or more in 12% of eyes, indicating a lack of stability in some eyes. In the 435 eyes, there was a small number of complications including six eyes that lost two or three lines of best-corrected acuity, 16 that experienced vascularization of the incisions, 2 that had delayed bacterial keratitis, and 4 that had recurrent epithelial erosions

Results of the Prospective Evaluation of Radial Keratotomy (PERK) Study One Year After Surgery

The Prospective Evaluation of Radial Keratotomy (PERK) study is a nine-center, self-controlled clinical trial of a standardized technique of radial keratotomy in 435 patients who had physiologic myopia with a preoperative refraction between −2.00 and −8.00 diopters. The surgical technique consisted of eight incisions using a diamond micrometer knife with blade length determined by intraoperative ultrasonic pachymetry and the diameter of central clear zone determined by preoperative refraction. At one year after surgery, myopia was reduced in all eyes; 60% were within ±1.00 diopter of emmetropia; 30% were undercorrected and 10% were overcorrected by more than 1.00 diopter (range of refraction, −4.25 to +3.38 D). Uncorrected visual acuity was 20/40 or better in 78% of eyes. The operation was most effective in eyes with a refraction between −2.00 and −4.25 diopters. Thirteen percent of patients lost one or two Snellen lines of best corrected visual acuity. However, all but three eyes could be corrected to 20/20. Ten percent of patients increased astigmatism more than 1.00 diopter. Disabling glare was not detected with a clinical glare tester, but three patients reduced their driving at night because of glare. Between six months and one year, the refraction changed by >0.50 diopters in 19% of eyes