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Alisa Thavikulwat, Laryssa Huryn, Wadih M Zein, Brian Patrick Brooks, Brett G Jeffrey; Development of the Focal Electro-oculogram and its Application to Stargardt Disease. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1216.
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© ARVO (1962-2015); The Authors (2016-present)
The structure of the retina/retinal pigment epithelium (RPE) complex may be compromised in macular disease. The full-field electro-oculogram (EOG), a functional test of the retina/RPE complex, is insensitive to local macular changes. We developed a focal EOG to non-invasively quantify changes in central retinal function and applied this test to patients with Stargardt disease.
The parameters (stimulus size and luminance) for generating a focal EOG light rise (LR) without contributions from light scatter were derived from experiments with 19 healthy volunteers (HVs). The focal light stimulus applied to generate a focal LR was turned off for 10 seconds each minute to avoid smearing the light over the retina while making saccadic eye movements. Focal and full-field EOGs were recorded from 6 Stargardt patients (37-65 years old) with central vision loss, but foveal preservation that enabled steady fixation. Full-field and focal EOGs were recorded from 4 and 7 HVs, respectively.
A focal EOG LR was consistently produced in response to a 40° stimulus at 40 cd/m2 in all HVs. Scattered light from this stimulus was estimated and control experiments suggest that this scattered light is not sufficient to contribute to the LR in most HVs.Time to LP, when present, was significantly longer in Stargardt patients, at 32.6±1.3 min compared to 28.5±0.5 min in HVs for the focal EOG (P value <0.05) and 31.8±1.0 min compared to 28.8±0.3 min in HVs for the full-field EOG (P value <0.05). There was no statistically significant difference in LP:BL between Stargardt patients with a LR, and HVs (focal EOG: 1.4±0.08 vs. 1.3±0.04, full-field EOG: 1.7±0.15 vs. 1.3±0.04). There was variability in the EOG recordings from the Stargardt patients; 4 patients had both focal and full-field LRs, 1 patient had a full-field LR, but no focal LR, and 1 patient had no LR with either stimulus.
Patients with Stargardt disease have a delayed LR. The focal EOG was not selectively altered in the Stargardt patients, but this finding may be due to the relatively large size of the stimulus (40°) compared with the size of atrophy (<20°) as demonstrated by imaging in these patients. Further control studies in patients with larger defined areas of retina/RPE loss are required to validate whether scattered light contributes to the focal EOG.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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