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Pattern electroretinograms from hemifields in normal subjects and patients with glaucoma
S L Graham1, V A Wong, S M Drance
1Department of Ophthalmology, University of British Columbia, Vancouver, Canada.
Investigative Ophthalmology & Visual Science
|August 1, 1994
Summary
The pattern electroretinogram (PERG) hemifield ratio in normal subjects is stable. Glaucoma patients show abnormal PERG ratios correlating with visual field loss, aiding in diagnosis.
Area of Science:
- Ophthalmology
- Neuroscience
Background:
- Glaucomatous visual field loss typically affects one hemifield.
- Assessing hemifield function is crucial for glaucoma diagnosis.
Purpose of the Study:
- Determine a baseline pattern electroretinogram (PERG) hemifield amplitude ratio (upper:lower) in normal subjects.
- Examine the utility of this PERG ratio in diagnosing glaucoma patients.
Main Methods:
- Recorded hemifield PERGs in 26 normal subjects and 8 glaucoma patients.
- Utilized transient and steady-state PERG with checkerboard stimuli.
- Analyzed the ratio of upper to lower hemifield amplitudes.
Main Results:
- Normal subjects exhibited a stable upper:lower PERG amplitude ratio (transient: 0.95±0.13, steady-state: 0.93±0.10).
- This ratio showed less variability than individual amplitudes and was independent of age or check size.
- Seven of eight glaucoma patients displayed abnormal PERG hemifield ratios, correlating with visual field defects.
Conclusions:
- The upper:lower hemifield PERG ratio is a stable, age-independent parameter in normal individuals.
- Abnormal PERG hemifield ratios are indicative of glaucomatous visual field loss.
- This ratio can aid in diagnosing glaucoma, though peripheral or symmetrical defects may be missed.