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Influence of Corneal Topographic Parameters in the Decentration of Orthokeratology

Gu, Tianpu M.S.; Gong, Boteng M.M.; Lu, Daqian M.M.; Lin, Weiping M.S.; Li, Na M.S.; He, Qing M.M.; Wei, Ruihua M.D., Ph.D.

doi: 10.1097/ICL.0000000000000580
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Objective: To investigate the lens decentration (LD) of orthokeratology (ortho-k) and the association between pretreatment corneal topographic parameters and LD of the ortho-k.

Methods: Fifty right eyes of 50 myopes wearing ortho-k lenses were included in the prospective study. Corneal topography was conducted pretreatment to get topographic corneal parameters, including flat-K (K1); steep-K (K2); corneal astigmatism (CA), CA at 0 to 3 mm (3 mm-CA), 3 to 5 mm (5 mm-CA), 5 to 7 mm (7 mm-CA); surface asymmetry index (SAI); surface regularity index; the curvature of best-fit sphere; the diameter of cornea (DC); the distance from the corneal center to the corneal vertex (CCCV); flat eccentricity (E1), steep eccentricity (E2), and E1/E2 (E ratio); and the corneal curvature differences between the nasal and temporal quadrants at 0 to 3 mm (3 mm-Knt), and the corneal curvature differences between the superior and inferior quadrants at 0 to 3 mm (3 mm-Ksi), 5 mm-Knt (at 3–5 mm), 5 mm-Ksi (at 3–5 mm), 7 mm-Knt (at 5–7 mm), and 7 mm-Ksi (at 5–7 mm). The relationship between these cornea topographic parameters and LD of the ortho-k was tested using stepwise multiple linear regression models.

Results: The mean magnitude of LD was 0.51±0.23 mm (0.06–1.03 mm). According to the stepwise analysis, 4 factors were associated with the overall LD (P<0.01): SAI (β=0.252), CCCV (β=0.539), 5 mm-CA (β=−0.268), and 3 mm-Ksi (β=−0.374); 5 factors were associated with the horizontal LD (P<0.01): DC (β=0.205), CCCV (β=0.881), 3 mm-CA (β=−0.217), 5 mm-Knt (β=0.15), and 3 mm-Ksi (β=−0.18); and 3 factors were associated with the vertical LD (P<0.01): SAI (β=0.542), 5 mm-CA (β=−0.188), and 3 mm-Ksi (β=−0.213).

Conclusion: Lens decentration is most common, but in most cases, the amount of LD is moderate and acceptable. The magnitude of LD can be predetermined by topographic corneal parameters. Surface asymmetry index, CCCV, 5 mm-Knt, and 3 mm-Ksi may be more preferable parameters in terms of the assessment of LD of ortho-k.

Center of Optometry (T.G., B.G., D.L., W.L., N.L., Q.H., and R.W.), Tianjin Medical University Eye Hospital, Tianjin, China; Tianjin Medical University Eye Institute (T.G., B.G., D.L., Q.H., and R.W.), Tianjin, China; The School of Optometry & Ophthalmology (T.G., B.G., D.L., W.L., N.L., Q.H., and R.W.), Tianjin Medical University, Tianjin, China.

Address correspondence to Ruihua Wei, M.D., Ph.D., Tianjin Medical University Eye Hospital, Tianjin Medical University Eye Institute, School of Optometry and Ophthalmology, Tianjin Medical University, Tianjin 300384, China; e-mail: rwei@tmu.edu.cn

The authors have no funding or conflicts of interest to disclose.

Supported by (1) National Nature Science Foundation of China (No: 81770901); (2) National Nature Science Foundation of China (No: 81570834); (3) Science Committee Nature Science Foundation of Tianjin (No: 17ZXHLSY00070).

R. Wei conceived and supervised this study. T. Gu, B. Gong, D. Lu, W. Lin, Q. He, and N. Li performed the study. B. Gong collected the data, and T. Gu analyzed the data. T. Gu and B. Gong wrote the manuscript. T. Gu and B. Gong contributed equally to this work and both were considered first authors.

Accepted December 24, 2018

© 2019 Contact Lens Association of Ophthalmologists, Inc.