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Keiichiro Minami, Tadatoshi Tokunaga, Keiichiro Okamoto, Kazunori Miyata; Evaluation of pterygium advancement using anterior corneal aberration: pilot study. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3544.
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© ARVO (1962-2015); The Authors (2016-present)
Evaluating advancement of pterygium based on corneal irregularity is objective and rational in term of corneal optics, and an anterior-segment optical coherence tomography (AS-OCT) enables accurate measurement of the anterior corneal surface elevation. The purpose of the prospective observation study was to evaluate pterygium advancement based on Zernike aberration analysis of AS-OCT anterior corneal evaluation data.
Corneal topography of 79 primary pterygium eyes from 70 patients were measured using an AS-OCT (SS-1000, Tomey). With the anterior corneal elevation data, Zernike polynomial coefficients were calculated for diameters of 1.0, 3.0, and 5.0 mm. The coma-like (S3) and higher-order (HOA) aberrations were obtained for analysis. Pterygium size was defined as a ratio of positions of the pterygium end with respect to the corneal diameter. Changes in the S3 and HOA with the pterygium sizes of less than 15%, 15-20%, 20-25%, 25-30%, 30-35%, 35-40%, 40-45%, and over 45%, were evaluated for the 3 diameters. Differences from the values for the size less than 15% were examined using the Steel multiple comparison after Kruskal-Wallis test.
Mean age was 69.1 (SD: 10.8) years. There were 77 pterygia originated from nasal region, and the size ranged from 8 to 55 % with a mean of 27.8%. The S3 in 1.0-diameter area showed no change in the size up to 30%, and significant increases in 30-35% or larger (P<0.04). In the 3.0-mm diameter S3, there was no change up to 25% while significant changes were found in 25-30% or larger (P<0.016). Significant changes were found in 20-25% or larger in the 5.0-mm diameter S3 (P<0.016). The HOAs in 1.0-, 3.0-, and 5.0-mm diameters significantly increased when the pterygium sizes were over 35-40%, 25-30%, and 20-25%, respectively (P<0.026, 0.016, and 0.017).
In this pilot study, pterygium sizes in which the S3 or HOA significantly increased altered with the diameter of the Zernike analysis. These preliminary results demonstrated that corneal irregularity due to advanced pterygium could be evaluated with multiple-diameter Zernike analysis of the anterior cornea.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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