Anja Strenger

Internal anterior chamber diameter using optical coherence tomography compared with white-to-white distances using automated measurements

PURPOSE: To compare internal horizontal anterior chamber (AC) diameter determined by optical coherence tomography (OCT) and horizontal corneal diameter (white‐to‐white [WTW]) using automated measurements. SETTING: Department of Ophthalmology, Johann Wolfgang Goethe‐University, Frankfurt am Main, Germany. METHODS: Internal AC diameter and WTW distance was measured in 52 eyes of 26 patients using the Visante OCT (Carl Zeiss Meditec), IOLMaster (Carl Zeiss Meditec), and Orbscan IIz topography system (Bausch & Lomb). Statistical evaluation was performed using the Bland‐Altman method and regression analysis for comparison of measurement techniques. The Kruskal‐Wallis test was used to measure the repeatability of each device. RESULTS: The mean internal AC diameter was 12.45 mm ± 0.53 (SD) with OCT; the mean WTW distance was 12.17 ± 0.45 mm with the IOLMaster and 11.84 ± 0.41 mm with the Orbscan IIz. A positive regression was determined for AC diameter and both WTW measurements. Measurement values varied little between both WTW measurement systems (R2 = 0.9384). CONCLUSIONS: Anterior chamber measurement using optical coherence tomography (Visante OCT) was easy to handle and showed good repeatability. The internal horizontal diameter of the AC was larger than the horizontal corneal diameter determined by automated WTW measurements (IOLMaster, Orbscan IIz). Optical coherence tomography with the Visante OCT allows direct measurement of the AC width.

Comparison of optical quality metrics to predict subjective quality of vision after laser in situ keratomileusis.

PURPOSE: To compare wavefront‐derived metrics to predict subjective quality of vision after laser in situ keratomileusis (LASIK) for myopia. SETTING: Department of Ophthalmology, Goethe University, Frankfurt am Main, Germany. METHODS: One month postoperatively, wavefront sensing was performed and overall subjective quality of vision assessed under 3 lighting conditions (photopic, high mesopic, low mesopic) with a questionnaire. Four wavefront‐error representations were computed for a pupil diameter of 6.0 mm and individual physiological pupil diameters at 0.4 lux: (1) the visual Strehl ratio based on optical transfer function (VSOTF), (2) the root‐mean‐square (RMS) value of Zernike orders 2 to 5 (total RMS), (3) higher‐order aberration (HOA) RMS, and (4) a wavefront‐error breakdown into the RMS of lower‐order aberrations, coma, spherical aberration, and remaining HOA. The impact of the postoperative wavefront error on subjective quality of vision was calculated using linear regression analysis. RESULTS: Fifty‐six eyes (29 patients) were included. The ability of wavefront error–derived metrics to predict subjective quality of vision was limited. The VSOTF, calculated for the best‐corrected eye, showed the highest predictability. Calculation of wavefront error for individual physiological pupil diameters did not improve predictive ability of the metrics. Eyes with a high theoretical retinal‐image quality had a high subjective quality of vision, and eyes with a low subjective quality of vision had a low theoretical image quality. CONCLUSIONS: Postoperative wavefront error had limited influence on the subjective quality of vision. Postoperative retinal image quality should be kept as high as possible to provide good subjective quality of vision.

Basic Knowledge of Refractive Surgery: Correction of Refractive Errors Using Modern Surgical Procedures

INTRODUCTION Refractive ophthalmic surgery allows refractive errors to be corrected permanently in a safe, effective, and reliable way with few complications. METHODS Selective literature review with special reference to the guidelines of the German Commission for Refractive Surgery. RESULTS With a total of almost 18 million treatments performed to date, laser in-situ keratomileusis (LASIK) is the most commonly used refractive surgical procedure worldwide. Alternatives to LASIK include surface ablation procedures (PRK, LASEK, Epi-LASIK) and phakic intraocular lens implantation. If ocular accommodation is lost, removal of the crystalline lens and implantation of modern multifocal intraocular lenses (refractive lens exchange) provide an alternative means of correcting myopia, hyperopia and presbyopia. DISCUSSION The treatment effect is maximized and complications kept to a minimum if strict inclusion criteria are applied and a high technical standard maintained during the procedure.