Optical Evaluation of Intracorneal Ring Segment Surgery in Keratoconus.

Purpose: The purpose of this study was to assess the impact of different intracorneal ring segments (ICRS) combinations on corneal morphology and visual performance on patients with keratoconus. Methods: A total of 124 eyes from 96 patients who underwent ICRS surgery were analyzed and classified into 7 groups based on ICRS disposition and the diameter of the surgical zone (5- and 6-mm). Pre- and postoperative complete ophthalmological examinations were conducted. Corneal geometry, volume, and symmetry were studied. Zernike polynomials were used to build a virtual ray-tracing model to evaluate optical aberrations and the Visual Strehl (VS). Results: ICRS induced significant flattening across the cornea, being more pronounced on the anterior (+0.38 mm, P < 0.001) than on the posterior (+0.15 mm, P < 0.001) corneal radius. Asphericity experienced a larger change for a 6-mm surgical zone diameter (from -1.23 ± 1.1 to -1.86 ± 1.2, P < 0.001) than for a 5-mm zone (from -1.99 ± 1.1 to -2.10 ± 1.5, P = 0.536). Mean astigmatism was reduced by 2.05 D (P < 0.001). Combination four was the most effective in reducing astigmatism. Coma decreased by 30% on average and combination one produced an average reduction by 51% (P < 0.05). Patients experienced significant improvement in visual performance, best corrected visual acuity increased from 0.57 ± 0.21 to 0.69 ± 0.21 and VS changed from 0.049 ± 0.02 to 0.065 ± 0.041. Conclusions: ICRS combinations implanted within 5 mm diameter zone are more effective in flattening the cornea, whereas those implanted on 6 mm diameter are as effective in reducing astigmatism and are a good choice if the asymmetry and the intended flattening are smaller. Combinations with asymmetrical implants are the best option to regularize corneal surface. Translational Relevance: This study uses methods and metrics of optical research applied to daily clinical practice.

Correction: Assesment of the QuickSee wavefront autorefractor for characterizing refractive errors in school-age children.

[This corrects the article DOI: 10.1371/journal.pone.0240933.].

Assesment of the QuickSee wavefront autorefractor for characterizing refractive errors in school-age children.

PURPOSE: To assess the performance of an open-view binocular handheld aberrometer (QuickSee) for diagnosing refractive errors in children. METHODS: 123 school-age children (9.9 ± 3.3 years) with moderate refractive error underwent autorefraction (AR) with a standard desktop device and subjective refraction (SR), with or without cycloplegia to determine their eyeglass prescription. Measurements with QuickSee (QS) were taken in 62 of these patients without cycloplegia (NC), and in 61 under cycloplegia (C). Differences in refraction values (AR vs SR vs QS) as well as the visual acuity (VA) achieved by the patients with each method (QS vs SR) were used to evaluate the performance of the device in measuring refractive error. RESULTS: The spherical equivalent refraction obtained by QS agreed within 0.5 D of the SR in 71% (NC) and 70% (C) of the cases. Agreement between the desktop autorefractor and SR for the same threshold was of 61% (NC) and 77% (C). VA resulting from QS refractions was equal to or better than that achieved by SR procedure in 77% (NC) and 74% (C) of the patients. Average improvement in VA with the QS refractions was of 8.6 and 13.4 optotypes for the NC and C groups respectively, while the SR procedure provided average improvements of 8.9 (NC) and 14.8 (C) optotypes. CONCLUSIONS: The high level of agreement between QuickSee and subjective refraction together with the VA improvement achieved in both study groups using QuickSee refractions suggest that the device is a useful autorefraction tool for school-age children.