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Amit Sangave, Vanessa Desmore, Christye SIsson, William Fischer, Rajeev S Ramchandran; Pupil Size and Quality of Retinal Photos in Tele-I-Care: A Diabetic Retinopathy Surveillance Project. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2288.
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To evaluate the effect of pupil size on the quality of digital fundus photos through undilated pupils in a primary care based diabetic retinopathy surveillance program.
As part of an IRB approved, ophthalmic tele-medicine initiative, fundus photos followed by external photos (Carl Zeiss Nonmydriatic Visucam) of 159 subjects from July through November 2013 were obtained. External photos were taken after flash-illuminated fundus photos. Fundus photos were graded by a single retina specialist (RR) at our institution and assigned a score of excellent, good, fair, adequate, or inadequate. Using external photos, pupillary and iris diameters were measured. To account for different subject to lens distances, the pupil-iris ratio was then used as a measure of pupil size. Simple (univariate) linear regression analysis was used to correlate pupil:iris ratio with fundus photo quality.
The eyes of 159 subjects (81 male, mean age 55.1 years) were reviewed. 43 eyes were ineligible, as pupil-iris ratio could not be calculated. Right and left eyes were analyzed separately (136 OD, 141 OS) for a total of 275 eyes. In right eyes, the quality of fundus photos was: 58.8% excellent (n=80), 28.6% good (n=39), 2.94% fair (n=4), 8.08% adequate (n=11), and 2.20% inadequate (n=3). In left eyes, the quality of fundus photos was: 43.9% excellent (n=62), 36.8% good (n=52), 2.83% fair (n=4), 13.4% adequate (n=19), and 2.83% inadequate (n=4). There was a moderately positive correlation between pupil-iris ratio and quality of retinal photograph OD (r=.707), but a much stronger correlation OS (r=.917).
Our study revealed a positive correlation between pupil size and quality of fundus photo. Correlation disparity between eyes (OS > OD) was likely secondary to greater flash exposure OS. Thus, pupil size is an important parameter for ensuring high quality fundus imaging in diabetic retinopathy surveillance programs. Small pupils may warrant further, more involved examination and may render non-mydriatic fundus photography less useful.
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