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The Unevenness and Non-orthogonal State of Distribution of Corneal Thickness and the Influence on Correction of Myopic Astigmatism by LASEK

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Abstract

To observe and calculate the unevenness and the non-orthogonal state of distribution of corneal thickness and the relationship between them using Pentacam and to investigate the influence of unevenness and the non-orthogonal state on correction of myopic astigmatism by laser subepithelial keratomileusis (LASEK). 230 eyes with myopic astigmatism treated with LASEK were divided into two groups: 114 eyes as the low astigmatism group (−0.25 to −0.75 DC) and 116 eyes as the midrange-high astigmatism group (−1.00 to −4.50 DC). With the help of the diagram of keratoconus evaluation program of the Pentacam, the D 3.0 and D 6.5 were calculated for the index of distribution of unevenness of the corneal thickness, and the absolute value of the angle between the maximum and minimum progression-index orientation (M 90) for the index of non-orthogonal states. The correction of myopic astigmatism by LASEK was based on standard vector analysis and power vector analysis. The follow-up period was for 3 months. The preoperative M 90 was 22.14° ± 20.87°, D 6.5 was 58.66 ± 21.32 μm, and D 3.0 was 16.11 ± 4.28 μm for the 230 eyes that were tested. The D 6.5 of low astigmatism group (55.62 ± 20.81) μm was significantly lower than that of midrange-high astigmatism group (61.65 ± 21.48) μm (P < 0.05). Of the 230 eyes, the M 90 was positively correlated with D 6.5 (r = 0.37, P < 0.001), and D 6.5 was positively correlated with D 3.0 (r = 0.56, P < 0.001). 3 months postoperatively, the absolute error vector (|EV|) of low astigmatism group (0.46 ± 0.34) was significantly lower than that of midrange-high astigmatism group (0.53 ± 0.29) (P < 0.01). The error of magnitude of low astigmatism group (−0.10 ± 0.31) was significantly lower than that of midrange-high astigmatism group (0.08 ± 0.41) (P < 0.001). The absolute error of angle (|EA|) of low astigmatism group (26.10 ± 27.24) was significantly higher than that of midrange-high astigmatism group (9.99 ± 17.32) (P < 0.001). The correction ratio of low astigmatism group (1.45 ± 1.21) was significantly higher than that of midrange-high astigmatism group (0.94 ± 0.33) (P < 0.01). The error ratio (ER) of low astigmatism group (1.34 ± 1.40) was significantly higher than that of midrange-high astigmatism group (0.42 ± 0.27) (P < 0.001). In low astigmatism group, M 90 was positively correlated with |EV| (r = 0.30, P < 0.001). In midrange-high astigmatism group, M 90 was positively correlated with ER (r = 0.31, P < 0.001) and D 6.5 was positively correlated with |EV| and B, respectively (r = 0.34, 0.33, P < 0.001). The relationship between unevenness and non-orthogonal state of distribution of corneal thickness could influence the correction of astigmatism by LASEK. Therefore, more attention should be paid to the correction of midrange-high astigmatism group by excimer surgery.

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Acknowledgment

This study was supported by Grant No. 11204277 from the National Natural Science Foundation of China.

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    Authors and Affiliations

    1. Shandong University, 44#, Wenhua Xi Road, Jinan, Shandong, China

      Shulin Wang

    2. Department of Ophthalmology, People’s Hospital of Zhengzhou, 33#, Huanghe Road, Zhengzhou, China

      Shulin Wang & Xin Wang

    3. Department of Ophthalmology, Shandong Eye Hospital, Shandong Eye Institute, Shandong Academy of Medical Sciences, 372#, Jingsi Road, Jinan, Shandong, China

      Mingna Liu, Haiying Wang, Jing Li & Weiyun Shi

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    1. Shulin Wang
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    2. Xin Wang
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    Correspondence to Weiyun Shi.

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    Shulin Wang and Xin Wang have contributed equally to this paper.

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    Wang, S., Wang, X., Liu, M. et al. The Unevenness and Non-orthogonal State of Distribution of Corneal Thickness and the Influence on Correction of Myopic Astigmatism by LASEK. Cell Biochem Biophys 73, 35–40 (2015). https://doi.org/10.1007/s12013-015-0571-2

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    • DOI: https://doi.org/10.1007/s12013-015-0571-2

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