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Effect of ocular residual astigmatisms on the correction of low refractive astigmatism using Q-value-guided LASIK

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Session Details

Session Title: LASIK Outcomes and Refinements

Session Date/Time: Monday 09/10/2017 | 14:30-15:50

Paper Time: 15:25

Venue: Room 4.4

First Author: : J.Costa PORTUGAL

Co Author(s): :    F. Neves   L. Figueiredo   C. Santos   T. Pacheco   C. Arede        

Abstract Details


To evaluate the influence of the ocular residual astigmatism (ORA) on the refractive and the higher order aberrations (HOA) outcomes in patients with high myopia and low astigmatism treated with Q-value guided laser in situ keratomileusis (LASIK).


Department of Ophthalmology of Centro Hospitalar Vila Nova de Gaia/Espinho, Portugal.


This retrospective study included 46 patients (81 eyes) with high myopia (>2.50D) and low astigmatism (<2.25D) submitted to LASIK (Zyoptix® aspheric algorithm, Technolas217z100® system-Bausch&Lomb). The ORA was determined by vector analysis using refractive cylinder and topographic astigmatism. Patients were divided into two groups based on the ORA (ORA > mean - high ORA group; ORA ≤ mean - low ORA group). The patients were also divided into two groups based on the value of the ratio ORA/anterior corneal astigmatism (ACA). Efficacy was determined by comparing the index of success (IS) and the HOA between the groups, 3 months after surgery.


The mean preoperative cylinder, the mean residual refractive cylinder postoperatively, the mean ORA and ORA/ACA were -0.63±0.57D, -0.34±0.48D, 0.69±0.31D and 0.85±0.62D, respectively. Mean IS in the high and low ORA groups were 0.97 and 0.68, respectively (P=0.25); in the high and low ORA/ACA groups were 1.65 and 0.54, respectively (P<0.01). A correlation between ORA/ACA and the IS was found (ρ=0.48,p<0.05). We also found a correlation between the ORA/ACA and the difference between the topographic and the refractive astigmatism axes (ρ=0.42,p<0.01). No correlation was found between ORA, ORA/ACA and the HOA outcomes.


The efficacy of astigmatic correction by LASIK (Zyoptix® aspheric algorithm) in patients with low astigmatism was significantly lower in eyes in which the preoperative refractive astigmatism is at a great extent located posterior to the anterior corneal surface (high ORA/ACA). However, the ORA and the ORA/ACA had no influence on the HOA outcomes. The ORA/ACA ratio, rather than the ORA, seems to influence the refractive outcomes of LASIK, and so it should be taken in consideration before performing refractive surgery.

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