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LM Periman, R Ambrosio, SE Wilson, DA Harrison; Estimating Scotopic Pupil Size using the Humphrey Topography Unit . Invest. Ophthalmol. Vis. Sci. 2002;43(13):148.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Accurate assessment of the scotopic pupil size of a patient is an important aspect of determining patient candidacy for refractive surgical procedures in order to minimize the risk of visual aberrations. The purpose of this study is to determine if the pupil measurements obtained by Humphrey Videokeratography can be used as an accurate estimate of pupil size under scotopic conditions as measured with Colvard Pupillometry. Methods: One observer obtained pupil measurements using the Colvard Pupillometer under standardized lighting conditions: scotopic (0.78 lux candles), mid light (38 lux candles) and high light conditions (146 lux candles). The same observer also recorded the pupil size measurement obtained automatically with Humphrey Videokeratography (233 lux candles). All 4 measurements were recorded for each of the 60 total patients. Results: As expected, the Colvard Pupillometry low light group was statistically different (p<0.0001) from the Humphrey Videokeratography automatic pupil measurement group. The difference in pupil values was calculated under these two conditions, the average of which was 1.8mm (confidence interval of +/-0.2mm and S.E.M. of 0.1mm). This value of 1.8 mm was then added to the Humphrey Videokeratography unit value to arrive at an Adjusted Auto value. The Colvard low light and Adjusted Auto data groups were then compared. The average (5.8 and 5.8mm), median (6.0 and 5.8mm) and mode (6.0 and 6.2mm) were found to be very similar between the Colvard low light and Adjusted Auto groups, respectively. The standard deviation (1.0 vs 0.6) and variance (1.0 vs 0.4) were higher for the Colvard low light group than the Adjusted Auto group respectively. Conclusion: The Humphrey Videokeratography unit can be effectively used as a rapid, simple, reasonable method of estimating pupil size under scotopic conditions in the pre-operative evaluation of potential refractive surgery patients and provides a permanent record of pupil size.
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