Robert N. Shaffer

Bio: Robert N. Shaffer is an academic researcher from University of California, San Francisco. The author has contributed to research in topics: Glaucoma & Glaucoma surgery. The author has an hindex of 21, co-authored 47 publications receiving 2455 citations.

Biostatistical Analysis of the Collaborative Glaucoma Study: I. Summary Report of the Risk Factors for Glaucomatous Visual-Field Defects

Abstract: • A prospective collaborative study was conducted in five centers during a 13-year period to identify factors that influence the development of visual-field defects (GVFDs) of open angle glaucoma. In 5,000 subjects, GVFDs developed in only 1.7% of eyes. Statistical analysis of 26 factors at first examination identified five that were significantly related to the development of GVFDs—outflow facility, age, applanation pressure, cup-disc ratio, and pressure change after water drinking. Their absolute initial value, and not its change with time, was the important predictor. Multivariate analysis showed their collective predictive power to be undesirably poor, indicating that other factors must play an important role in the development of GVFDs. Mortality-table analysis indicated that during a period of five years, 98.54% of eyes with initial pressure less than 20 mm Hg continued to be free from GVFDs as compared with 93.34% of those with pressure 20 mm Hg or greater.

Anatomical classification of the developmental glaucomas.

Abstract: • With the use of observations in 250 cases of childhood glaucoma, defects were classified anatomically according to the three major anterior chamber structures affected: the trabecular meshwork, the iris, and the cornea. The classification should do much to facilitate communication in the area of the developmental glaucomas and provide standardization of terminology to allow collaborative study of these rare diseases.

The Ocular Hypertension Treatment Study: A Randomized Trial Determines That Topical Ocular Hypotensive Medication Delays or Prevents the Onset of Primary Open-Angle Glaucoma

Abstract: Background Primary open-angle glaucoma (POAG) is one of the leading causes of blindness in the United States and worldwide. Three to 6 million people in the United States are at increased risk for developing POAG because of elevated intraocular pressure (IOP), or ocular hypertension. There is no consensus on the efficacy of medical treatment in delaying or preventing the onset of POAG in individuals with elevated IOP. Therefore, we designed a randomized clinical trial, the Ocular Hypertension Treatment Study. Objective To determine the safety and efficacy of topical ocular hypotensive medication in delaying or preventing the onset of POAG. Methods A total of 1636 participants with no evidence of glaucomatous damage, aged 40 to 80 years, and with an IOP between 24 mm Hg and 32 mm Hg in one eye and between 21 mm Hg and 32 mm Hg in the other eye were randomized to either observation or treatment with commercially available topical ocular hypotensive medication. The goal in the medication group was to reduce the IOP by 20% or more and to reach an IOP of 24 mm Hg or less. Main Outcome Measures The primary outcome was the development of reproducible visual field abnormality or reproducible optic disc deterioration attributed to POAG. Abnormalities were determined by masked certified readers at the reading centers, and attribution to POAG was decided by the masked Endpoint Committee. Results During the course of the study, the mean ± SD reduction in IOP in the medication group was 22.5% ± 9.9%. The IOP declined by 4.0%± 11.6% in the observation group. At 60 months, the cumulative probability of developing POAG was 4.4% in the medication group and 9.5% in the observation group (hazard ratio, 0.40; 95% confidence interval, 0.27-0.59; P Conclusions Topical ocular hypotensive medication was effective in delaying or preventing the onset of POAG in individuals with elevated IOP. Although this does not imply that all patients with borderline or elevated IOP should receive medication, clinicians should consider initiating treatment for individuals with ocular hypertension who are at moderate or high risk for developing POAG.

Reduction of intraocular pressure and glaucoma progression: results from the Early Manifest Glaucoma Trial.

Abstract: Objective To provide the results of the Early Manifest Glaucoma Trial, which compared the effect of immediately lowering the intraocular pressure (IOP), vs no treatment or later treatment, on the progression of newly detected open-angle glaucoma. Design Randomized clinical trial. Participants Two hundred fifty-five patients aged 50 to 80 years (median, 68 years) with early glaucoma, visual field defects (median mean deviation, −4 dB), and a median IOP of 20 mm Hg, mainly identified through a population screening. Patients with an IOP greater than 30 mm Hg or advanced visual field loss were ineligible. Interventions Patients were randomized to either laser trabeculoplasty plus topical betaxolol hydrochloride (n = 129) or no initial treatment (n = 126). Study visits included Humphrey Full Threshold 30-2 visual field tests and tonometry every 3 months, and optic disc photography every 6 months. Decisions regarding treatment were made jointly with the patient when progression occurred and thereafter. Main Outcome Measures Glaucoma progression was defined by specific visual field and optic disc outcomes. Criteria for perimetric progression were computer based and defined as the same 3 or more test point locations showing significant deterioration from baseline in glaucoma change probability maps from 3 consecutive tests. Optic disc progression was determined by masked graders using flicker chronoscopy plus side-by-side photogradings. Results After a median follow-up period of 6 years (range, 51-102 months), retention was excellent, with only 6 patients lost to follow-up for reasons other than death. On average, treatment reduced the IOP by 5.1 mm Hg or 25%, a reduction maintained throughout follow-up. Progression was less frequent in the treatment group (58/129; 45%) than in controls (78/126; 62%) ( P =.007) and occurred significantly later in treated patients. Treatment effects were also evident when stratifying patients by median IOP, mean deviation, and age as well as exfoliation status. Although patients reported few systemic or ocular conditions, increases in clinical nuclear lens opacity gradings were associated with treatment ( P = .002). Conclusions The Early Manifest Glaucoma Trial is the first adequately powered randomized trial with an untreated control arm to evaluate the effects of IOP reduction in patients with open-angle glaucoma who have elevated and normal IOP. Its intent-to-treat analysis showed considerable beneficial effects of treatment that significantly delayed progression. Whereas progression varied across patient categories, treatment effects were present in both older and younger patients, high- and normal-tension glaucoma, and eyes with less and greater visual field loss.

The Ocular Hypertension Treatment Study: baseline factors that predict the onset of primary open-angle glaucoma.

Abstract: Background The Ocular Hypertension Treatment Study (OHTS) has shown that topical ocular hypotensive medication is effective in delaying or preventing the onset of primary open-angle glaucoma (POAG) in individuals with elevated intraocular pressure (ocular hypertension) and no evidence of glaucomatous damage. Objective To describe baseline demographic and clinical factors that predict which participants in the OHTS developed POAG. Methods Baseline demographic and clinical data were collected prior to randomization except for corneal thickness measurements, which were performed during follow-up. Proportional hazards models were used to identify factors that predicted which participants in the OHTS developed POAG. Results In univariate analyses, baseline factors that predicted the development of POAG included older age, race (African American), sex (male), larger vertical cup-disc ratio, larger horizontal cup-disc ratio, higher intraocular pressure, greater Humphrey visual field pattern standard deviation, heart disease, and thinner central corneal measurement. In multivariate analyses, baseline factors that predicted the development of POAG included older age, larger vertical or horizontal cup-disc ratio, higher intraocular pressure, greater pattern standard deviation, and thinner central corneal measurement. Conclusions Baseline age, vertical and horizontal cup-disc ratio, pattern standard deviation, and intraocular pressure were good predictors for the onset of POAG in the OHTS. Central corneal thickness was found to be a powerful predictor for the development of POAG.