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The inter observer and intra observer repeatability of horizontal white-to-white measurements by digital calipers and Orbscan II

Poster Details

First Author: S.Nagappa INDIA

Co Author(s):    A. Saxena   M. Kumellil           

Abstract Details



Purpose:

To demonstrate the difference in the white to white diameter values obtained from the phakic volunteers as measured by two different observers and its comparison from the values obtained from Orbscan II

Setting:

Naryana Nethralaya, tertiary eye care centre, Bangalore, India

Methods:

In this study, subjects underwent measurement of white to white diameters of both the eyes by two ophthalmologists wherein a set number of 3 readings and the average of the 3 readings were taken and then patient was subjected to Orbscan II (Bausch & Lomb) to find out the white to white diameter readings. Inter observer variability was determined by Bland Altman analysis.

Results:

The study evaluated the white to white diameters of 60 eyes of 30 patients. The data was collected and analyzed for inter observer and intra observer repeatability. The intraobserver coefficient of variance was 0.97 ±0.78 (95% Confidence Interval [CI], 2.51 to -0.56]. The mean difference between 2 sets of readings by first observer was -0.01(tested between the limits of agreement of 0.38 to -0.41). The mean difference between observers was 0.01(tested between the limits of agreement of 0.47to -0.44).The mean white to white diameter difference between digital calipers and Orbscan II was -0.31 (tested between the limits of agreement of 0.33 to -0.96).There was no statistical difference between the values obtained on the digital calipers by the two observers though these values did not agree with the Orbscan values. The digital calipers underestimated the Orbscan values for lower means and overestimated the values at higher means.

Conclusions:

When using a standardized measurement technique the digital calipers had good intra and interobserver repeatability. However the digital caliper measurements cannot be used interchangeably with the Orbscan values. FINANCIAL INTEREST: NONE

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