Purchase this article with an account.
Frank Spors, Jason Shen, Dorcas Tsang, Lance McNaughton, Donald J Egan, Pinakin Gunvant Davey; Agreement of Three Topographers in Assessing the Shapes of Normal Corneas. Invest. Ophthalmol. Vis. Sci. 2019;60(9):2149.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
This study compares measurements of human corneal shape descriptors, Sim-K and e-values, obtained with three different corneal topographers.
We measured corneal topographies of the right eyes of 41 study participants (28 females, 13 males), age range 23 to 45 (Mean 28, SD 4), refractive error range sph -14.75 to +3.25 (Mean -2.55, SD 3.16), cyl -2.50 to 0.00 (Mean -0.52, SD 0.67) with three different corneal topographers: Medmont E-300, Oculus Keratograph 4, and Zeiss Atlas 9000. Exclusion criteria were: active eye disease, irregular astigmatism, s/p refractive surgery.We repeated each measurement three times per cornea and instrument and used average values. Sim-K values were converted into vectors M, J0, J45 using Fourier analysis. E-values were not converted. For statistical analysis, we performed repeated measures one-way ANOVA with Tukey’s multiple comparisons test. A statistically significant difference was confirmed when P values < 0.05
We found: Measurements of M, J0 and J45 were not statistically significant different for all three topographers (p = 0.2384, p = 0.6862 and p = 0.5142, respectively). Measurements of e-value were statistically significantly different (P = 0.0001). When evaluating these differences, using Tukey’s multiple comparison tests, we found that the Oculus Keratograph 4 and Medmont E-300 topographers were in agreement (P = 0.974). The Zeiss Atlas 9000 topographer, however, was not in agreement with either one of the other topographers. It produced mean differences of 0.042 compared to the Oculus Keratograph 4 data (P < 0.0001) and 0.045 compared to the Medmont E-300 data (P = 0.0009).
When assessing Sim-K values at healthy, normal corneas, the Medmont E-300, Oculus Keratograph 4, and Zeiss Atlas 9000 corneal topographers produced statistically similar results, which indicates that the instruments are comparable in conducting Sim-K measurements. When assessing peripheral corneal shape changes, using e-values, data obtained by the Medmont E-300 and Oculus Keratograph 4 were statistically similar, while data obtained by the Zeiss Atlas 9000 were significantly higher. Therefore, when assessing corneal e-values, the Medmont E-300 and Oculus Keratograph 4 produced comparable results, the Zeiss Atlas 9000 did not. This requires consideration in clinical practice, especially when rigid contact lens parameters are determined based on these measurements.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
This PDF is available to Subscribers Only