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Benno L. Petrig, Matthew S. Muller, Ann E. Elsner, Joel A. Papay, Lisa M. Ensman, Elli J. Kollbaum, Glen Y. Ozawa, Taras Litvin, Jorge A. Cuadros; Fixation Stability of Diabetic Patients Assessed by Laser Scanning Digital Camera. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5736.
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© ARVO (1962-2015); The Authors (2016-present)
To study fixation stability in diabetic patients using an automatic method of aligning retinal images from the Laser Scanning Digital Camera (LSDC). To determine whether eccentric viewing elicits poorer fixation than straight ahead and whether patients likely to have more retinal disease or neuropathy differ in fixation stability.
Fixation stability was assessed in 154 patients presenting to the Eastmont Wellness Center, a diabetic retinopathy screening site within the EyePACS telemedicine network. Patients (age 54±10 yr) spanned a broad range of disease from no to proliferative diabetic retinopathy. All had been previously diagnosed with diabetes mellitus, with either known or suspected eye disease based on prior eye or primary care examinations. To acquire images, the LSDC scans a slit of light across the retina and detects the light return with a 2-dimensional CMOS detector array. Illumination is 2mW at 850 nm (comfortable for patient), and pupil size is <3 mm (no dilatation). Retinal images (36 deg field, 1 Mp) were acquired continuously at 11 Hz. Sequences of 20 images were captured. A region of interest for registration was found automatically by zero-lag cross-correlation of the first image with and without median filtering. Remaining images were registered by cross-correlation. Those not meeting the criteria for successful alignment were dropped. The standard deviation (SD) of the Euclidean distances between the positions of a retinal feature and the centroid was taken as the metric for fixation stability. We compared fixation data for a steady target either straight-ahead or 15 deg nasally, selecting one eye per subject and the sample with the median SD.
Fixation stability averaged over all patients was 106 microns. Straight-ahead fixation was not significantly better than nasal fixation. Patients with self-reported duration of diabetes >20 yr had on average worse fixation stability that those with durations of 1, 2, 3, 11-15, and 16-20 yr (p<.006, .019, .009, .006, .004), but there was considerable overlap among individual patients. Fixation stability worsened with age (SD=62+0.8*age; r^2=0.019), but age does not fully account for the worsening with increasing duration.
In diabetic patients with central vision, more peripheral viewing does not lead to worse fixation stability. Large individual differences exist that are related to duration of diabetes and to age.
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