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Analysis of location and relative displacement of pupillary centroid in photopic, mesopic and scoptic conditions using a new digital pupillographer

Poster Details

First Author: G.Prakash UNITED ARAB EMIRATES

Co Author(s):    M. Suhail   D. Srivastava   V. Jhanji   R. Bacero     

Abstract Details



Purpose:

To analyse the location of pupillary centroid in different illumination conditions and to analyse the pattern of centroid shift between these conditions.

Setting:

Cornea and refractive surgery services of a tertiary care hospital.

Methods:

In this cross sectional clinical study, 50 consecutive , dark adapted eyes of 25 normal candidates with emmetropia/mild to moderate myopia underwent pupillography with a new anterior segment analysis system with a digital pupillographer (Sirius, CSO, Italy). The measurements made were scotpic , photopic and mesopic pupil sizes and the x,y coordinates of the pupil centroid.

Results:

The mean scotopic(S),mesopic(M) ,photopic(P) pupil sizes were 6.07±0.7mm, 4.13±0.7mm, and 4.06±0.6mm(p<0.001,ANOVA).The mean centroid position in (x,y) coordinates were scotpic(-0.19±0.1mm,0.02±0.1mm),mesopic(-0.18±0.1mm,0.01±0.1mm) & photopic(-0.15±0.2mm,0.02±0.1mm).The centroid shift in horizontal axis(x-coordinate) was signficant for photopic compared to mesopic(p=0.02) and scotopic(p<0.001),paired t-test.There was no significant difference in vertical (y-coordinate) centroid shift in all three light conditions or in horizontal shift between photopic and mesopic.The mean distance of centroid from actual reference center were scoptic 0.12±0.01mm,mesopic 0.13±0.01mm and photopic 0.13±0.02mm.All three centroids' location were signficantly different from the center(zero), confirming a difference between the actual reference center and pupil centroid (one sample t-test,p<0.001). The photopic centroid was located signifcantly further than that of photopic (p= 0.016) but not mesopic (p=0.3) .The vectoral distances between centroids (mm,angle) were S to M (0.08±0.05mm,70.5± 53°), M to P (0.09±0.08mm,66.3± 51°) and S to P (0.10±0.09mm, 55.7± 44°).All the three comparisons (M & P, S & P and S&M) between linear and angular (radians) distances of centroids were significantly different from zero, confirming an actual occourence of centroid shift when switching between different lightening conditions (one-sample t-test,p<0.001).However, all the three were comparable suggesting similar amount of centroid shifts happening between the three lightening conditions (p>0.05 ,paired t-test).

Conclusions:

The pupillary centroid is different from the actual refrence center,and shifts angularly and linearly between photopic, mesopic and scoptic illumination to statistically similar amounts. Futher, significant shift was found to occour in horizontal axis in our study between photopic and other lightening conditions. Photopic centroid was found to be signifcantly further from actual reference center compared to scoptic centroid. These findings have important clinical implication in multifocal intraocular lens implantation and laser vision correction where illumination setting can affect visual performance. FINANCIAL INTEREST: NONE

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