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Session Title: Quality of vision evaluation techniques
Session Date/Time: Tuesday 08/10/2013 | 14:00-16:00
Paper Time: 14:32
Venue: Elicium 2 (First Floor)
First Author: : S.Peixoto-De-Matos PORTUGAL
Co Author(s): : J. Salgado-Borges L. Dias J. Costa H. Neves A. Queirós J.
To correlate the index of light distortion surrounding an intense source of light measured with an experimental device with the ocular scattering index measured with a commercially available device in a population of pseudophakic patients implanted with monofocal intraocular lens (IOL).
Setting/venue: CEORLab - Center of Physics - University of Minho Braga - Portugal Clinica Oftalmológica Salgado-Borges - Porto - Portugal
Sixty-five patients (age 69±7 years, range: 53 to 86 years; 65% females) undergone facoemulsification followed by pseudophakic IOL implantation with monofocal IOL by the same experienced surgeon. Examinations were performance between 5 to 8 months after surgery and an ophthalmological and optometric examination confirmed good ocular health status and media transparency while an optometric examination showed that all patients achieved at least 0.8 decimal unaided monocular VA and at least 1.0 for best corrected visual acuity. Patients worn their distance prescription while the exam was performed. The testing screen is formed by small light emitting diodes (LED) surrounding a central intense source of light. The patient was asked to identify the peripheral LEDs from a distance of 2.5 meters in a totally darkened room except for the sources of light used for testing. Evaluations were conducted with the natural pupil of the patients, without pharmacological dilation. Overall Ocular Scattering Index for a 4mm pupil (overall OSI) and tear film ocular scattering index for a 7 mm aperture (tear film OSI) as well as other parameters relate to the quality of vision through the ocular-IOL optical system were evaluated with the Optical Quality Analizer System OQAS (Visiometrics, Spain) under non-dilated conditions.
Average power of the lenses was 21.4±2.4diopters (14 to 26 diopters) with a post-operative spherical equivalent refractive error of M=0.11±0.53D and cylinder components of astigmatism J0=-0.08±0.28 diopters and J45=0.029±0.16 diopters. Scattering index OSI was 2.1±2.0 (range 0.3 to 9.5). Light distortion index was 25.2%±16.7 % (range 7.24 to 90.8 %). Intra-ocular light distortion measured with the OQAS was significantly correlated with Light Distortion measured with our experimental device (Coefficient of correlation r=0.511; p>0.001). Irregularity index was also positively correlated but in a weaker manner with OSI (r=0.324; p=0.009). There was not correlation between best corrected visual acuity with OSI or Light Distortion what might be expected based on the inclusion criteria considered
A significant part of the perception of light distortion can be explained by the Ocular Scattering Index measured with OQAS. However, both devices seem to represent different aspects of image quality perception by pseudophakic patients as more sources might be involved in the global perception of Light Distortion surrounding lights. Combination of the evaluation of scattering using the OQAS which is an objective method and light distortion index with the new device which is able to quantify the subjective perception of the patient, might help to explain and interpret some photic phenomena occurring after cataract and other ophthalmic surgical procedures.
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