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D. K. Roberts, Y. Yang, A. Lukic, J. T. Wilensky, M. N. Wernick; Pupil Irregularity Quantification in Pigment Dispersion Syndrome Using Near Infrared Iris Photography. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5660.
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© ARVO (1962-2015); The Authors (2016-present)
Near infrared (NIR) imaging appears to be the most sensitive means available to detect and record iris transillumination defects (ITDs) in various disorders. During study of the technique and development of prototype instrumentation, we observed that the method might be easily adapted to quantify pupil size, shape, and displacement in addition to iris transillumination. We subsequently developed and tested a method to quantify pupil shape irregularity.
After observing subtle pupillary irregularity in several pigment dispersion syndrome (PDS) subjects in an existing NIR database, we analyzed iris images from 29 classic PDS subjects (15 White, 12 African-American, 2 Hispanic; 16 females, 13 males) and 29 randomly-selected age, race, gender, and eye color matched control subjects. In attempt to quantify pupil irregularity, two measures were calculated based on pupil contours that were generated via an automated computer algorithm. These included a pupil roundness measure (PR=Dice similarity coefficient between the outlined pupil region and a reference perfect circle co-centric with the pupil region; range=0-1; perfect circle=1) and a pupil smoothness measure (PS=Dice similarity coefficient between the outlined pupil region and a reference perfect ellipse co-centric with the pupil region; range=0-1; perfectly smooth pupil=1) was calculated.
Mean age of subjects was PDS=45.3 yrs and controls=44.7 yrs. A scatter plot display incorporating the PR and PS measures indicated a clear separation of certain PDS eyes from most other eyes. Overall, the mean PR and PS values were lower for PDS eyes (PR=0.9897, PS=0.9955) than normal eyes (PR=0.9917 PS=0.9981). Statistical significance was reached for the PS measure (P=0.007) but not for the PR measure (P>0.05), which may show usefulness of a dual measure and also provide insight into the type of dyscoria present in this subject group.
NIR photography may provide a very sensitive means to quantify pupil characteristics using the method we describe. Subtle dyscoria may sometimes be a feature of the classic PDS phenotype.
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