Comprehensive Evaluation of Anterior Corneal Change in Asphericity Calculated by the Tangential Radius of Curvature after LASIK.
J Ophthalmol 2017;
2017:3874371. [PMID:
28265465 PMCID:
PMC5317105 DOI:
10.1155/2017/3874371]
[Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 11/25/2016] [Accepted: 12/19/2016] [Indexed: 11/17/2022] Open
Abstract
To evaluate the change in the anterior corneal asphericity (ΔQ) comprehensively calculated using the tangential radius (rt) after LASIK. Forty-two right eyes were evaluated using the Orbscan II corneal topographer. The pre- and postoperative Q-values of the flat principal semimeridians calculated by the sagittal radius were compared to those by the tangential radius. The Q-value of each semimeridian in the horizontal region was calculated by rt. Fourier fitting was used to model the 360-semimeridional variation of Q-values and to fit the Q-values in the vertical region before and after surgery. There were significant differences in Q-values between the two methods before (P < 0.001) and after surgery (P = 0.003). A significant increase in postoperative Q-value was detected compared to preoperative Q-value (P < 0.001) calculated by rt. The 360-semimeridional variation of the Q-values was well fitted with a third- and fourth-degree Fourier function before and after surgery. The ΔQ-value distribution presented double valley variation, with the amount of ΔQ being lowest in the near-vertical regions and highest in the near-horizontal regions. Calculating the Q-value with rt combined with Fourier fitting, we evaluated 360 ΔQ-values' variation of semimeridians of the entire anterior corneal surface and then displayed true and complete anterior corneal shape after LASIK.
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