Glaucoma affects steady state VEP contrast thresholds before psychophysics.

PURPOSE: Frequency doubling technology (FDT) is a recent psychophysical test for glaucoma. It measures the contrast threshold to low spatial frequency, high temporal frequency sinusoidal luminance profile bars. We wanted to confirm, with stricter controls, Vaegan and Hollow's report that contrast thresholds of steady state visual evoked potentials (ssVEPs) to a stimulus resembling the central field of the FDT test was more sensitive to glaucoma than the subjective threshold to the same stimulus and to start to optimize the technique. METHODS: A double masked trial using 57 eyes of 42 subjects. Both thresholds were estimated by modified binary search. In psychophysical testing, subjects were given a two alternative forced choice task. In ssVEP testing a significant signal in any one of eight channels was deemed to be a detection. In some subjects electrode positions were compared, both eyes were tested, tests were repeated to estimate reliability, stimulus frequencies were varied or full contrast functions were obtained. RESULTS: Thresholds and percent abnormal increased as a function of glaucoma severity for ssVEPs but not for psychophysics. Both threshold measures were reliable. Interocular correlations were low. SsVEP amplitude against contrast functions had similar thresholds to those found by modified binary search. The data was too irregular for individual thresholds to be estimated from a fitted exponential. Amplitudes were greatest at 7 to 10 Hz, < or =6 cm above inion and least laterally. Noise was similar across electrodes. CONCLUSIONS: SsVEP contrast thresholds to a stimulus like the central field of the FDT test detected glaucoma better than corresponding psychophysical thresholds at 18.29 Hz, when formal controls were used, as they had in a less controlled previous study at 7.14 Hz.

Choroidal melanoma with extrascleral extension in an Australian Aboriginal man.

Choroidal melanoma is a rare occurrence in pigmented races. Low clinical suspicion of choroidal melanoma may result in diagnostic delay. We present a rare case of choroidal melanoma with extrascleral orbital extension in an Australian Aboriginal man. We are unaware of previous reports of uveal melanoma in Aboriginal Australians and could find no reference to it in a computerized search utilizing Medline.

Early paracentral visual field loss in patients taking hydroxychloroquine.

OBJECTIVE: To review the natural history and ocular and systemic adverse effects of patients taking hydroxychloroquine sulfate who attended an ophthalmic screening program. DESIGN: Retrospective study. RESULTS: Records of 262 patients who were taking hydroxychloroquine and screened in the Department of Ophthalmology were reviewed. Of the 262 patients, 14 (18%) of 76 who had stopped treatment at the time of the study experienced documented adverse effects. Systemic adverse effects occurred in 8 patients (10.5%) and ocular adverse effects, in 5 (6.5%). Thirty-five patients (13.4%) had visual field abnormalities, which were attributed to hydroxychloroquine treatment in 4 patients (1.5%). Three of the 4 patients were taking less than 6.5 mg/kg per day and all patients had normal renal and liver function test results. CONCLUSIONS: The current study used a protocol of visual acuity and color vision assessment, funduscopy, and Humphrey 10-2 visual field testing and shows that visual field defects appeared before any corresponding changes in any other tested clinical parameters; the defects were reproducible and the test parameters were reliable. Patients taking hydroxychloroquine can demonstrate a toxic reaction in the retina despite the absence of known risk factors. Screening, including Humphrey 10-2 visual field assessment, is recommended 2 years after the initial baseline and yearly thereafter.