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Sourabh Sharma, Baskaran Mani, Rukmini A. V, Hla Myint Htoon, Tin Aung, Joshua Gooley, Dan Milea; Ocular determinants of pupillary light responses to red and blue light: a population-based study . Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):581. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
The pupillary light reflex is assumed to be primarily governed by neural responses to light. The aim of this study was to explore the potential influence of ocular anatomical factors on pupillary responses to light at different wavelengths and intensities, using a novel pupillometer.
In this cross-sectional, population-based study, we included 177 normal subjects (94.4% ethnic-Chinese, 65.5% female), recruited from a general Polyclinic population. Direct pupillary responses to continuously increasing irradiances (6.8 to 13.8 log photons cm-2 s-1) of red (631nm) and blue (469nm) light were measured, using an infra-red pupillometer. Swept source Optical Coherence Tomography performed in mesopic light allowed measurement of lens vault (LV), anterior chamber width (ACW), iris thickness (IT), iris volume and iris curvature (IC). Axial length (AL), Anterior chamber depth (ACD) and lens thickness (LT) were measured by noncontact partial coherence laser interferometry. Univariate and multivariate regression analyses were performed to determine ocular and systemic factors correlated associations with pupillometry measurements.
Pupil diameter measured in darkness was negatively correlated with age (β = -0.334, p < 0.001). The amplitude (β = -0.233, p = 0.006) and latency (β = 0.205, p = 0.014) of pupillary constriction to blue light were associated with age. The iris thickness was correlated with the amplitude of constriction to both blue (β = -0.321, p < 0.001) and red light stimuli (β = -0.336, p < 0.001). Other ocular parameters (LV, ACW, Iris volume, IC, AL, ACD, LT and refractive errors) were not significantly associated with pupillometric outcomes. The pupil responses to blue light were more invariable, as compared to the red light, in terms of latency (p<0.001), amplitude (p<0.001) and velocity (p<0.001) of constriction.
Pupillary responses to chromatic stimuli may be affected by anterior segment parameters. Iris thickness seem to affect pupillary responses to both blue and red light. Additional colour pupillometric studies coupled with simultaneous anterior segment video OCT recordings are needed in order to confirm these preliminary results.
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