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A. Bell, A. C. James, M. Kolic, T. Maddess; Perimetry From Pupillography: Dichoptic Multifocal Stimuli Can Distinguish Subjects With Early-Stage Type 2 Diabetes. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1332.
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We sought to derive perimetric measures from the responses of pupils to novel spatial and temporal patterns of dichoptic multifocal visual stimuli; we then investigated whether the measures could distinguish 23 subjects in the early stages of type 2 diabetes from 23 normal subjects.
We used a prototype of the TrueField Analyzer to deliver a multifocal sequence of flashed stimuli to both eyes at the same time. This device uses a stereoscopic pair of LCD displays to deliver pseudorandomly modulated arrays of light stimuli to multiple regions of each retina while pupil responses are recorded with infrared cameras. The multifocal stimuli covered 44 regions per eye and induced variations in pupil diameter which were measured across 8 segments of 30 s. The method was largely immune to the effects of blinks and fixation losses. Applying receiver operator analysis, we then examined whether the pupil responses of the diabetic patients could be reliably discriminated from those of normal subjects. We examined the n-worst constriction amplitudes, time to peak, and linear combinations of those.
Dichoptic multifocal pupillometry provided robust plots of pupil contraction versus post-stimulus time for each stimulus region. These region-by-region constrictions were reliable, giving median z-scores of 2 to 3. Responses of the normal and diabetic subjects were statistically different when region-by-region effects were considered (p<0.0005), but not when aggregated (p=0.07). The diagnostic performance (expressed as areas under ROC plots) for the 8 subjects who had been diagnosed with type 2 diabetes for at least 10 years was 0.89 ± 0.06 (mean ± SE), rising to 0.97 ± 0.03 when between-eye asymmetry was considered.
In a pilot study of 23 patients diagnosed with type 2 diabetes, dichoptic multifocal pupillography produced perimetric measures that were statistically different to those seen in 23 matched controls, especially for those who had had the disease for more than 10 years. This result, if confirmed in a wider group, suggests that the method may be clinically useful.
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