Results were obtained from 84 subjects with suspected glaucoma (GS, mean age 56.6 ± 13.8 years, 27% of African-American descent), and 34 patients with early manifest glaucoma (EMG, mean age 65.9 ± 10.7 years, 23% of African-American descent). Eligibility was determined by a comprehensive eye examination and medical–ocular history. Eye examination included IOP evaluation with Goldmann applanation tonometry, gonioscopy, dilated fundus examination, and stereophotographs of the optic disc, from which vertical cup-to-disc (C/D) ratios were evaluated. GS patients had small refractive errors (−0.68 ± 2.3 spherical diopters), normal corrected visual acuity (≥20/25), normal SAP (Humphrey Visual Field Analyzer II; Carl Zeiss Meditec, 24-2 SITA Standard: mean deviation [MD] −0.58 ±1.34 dB), but optic disc abnormalities (vertical cup-to-disc [C/D] ratio > 0.5, C/D asymmetry ≥ 0.2, localized thinning of the disc, splinter hemorrhages), and one or more risk factors for glaucoma (family history positive for glaucoma, old age, African descent, increased IOP (>21 mm Hg). EMG patients also had small refractive errors (−0.82 ± 2.3 spherical diopters), normal corrected visual acuity (≥20/25) and optic disc abnormalities, but in addition had repeatable defects of SAP (glaucoma hemifield test outside normal limits, pattern SD of P < 5%, or a cluster of ≥3 points in the pattern deviation plot in the superior or inferior hemifield with P < 5%, one of which reached P < 1%) and/or progressive glaucomatous changes of the optic disc. The average SAP MD was −2.7 ± 4.5 dB.
Exclusion criteria were the presence of ocular disease other than glaucoma, and presence of systemic disease that may cause nonspecific PERG abnormality such as diabetes, Parkinson’s disease, and multiple sclerosis. Patients with previous intraocular surgery, except for uncomplicated cataract extraction, were excluded. Patients with high myopia (>5 D) were also excluded, because the ERG may be nonspecifically reduced in high myopia.
53 Eight (10%) of 84 GS patients and 24 (71%) of 34 EMG patients were on various topical medications to reduce IOP.