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Binocular summation with diffractive bifocal intraocular lenses: preliminary results

Poster Details

First Author: S.Peixoto de Matos PORTUGAL

Co Author(s):    C. Borges   H. Ferreira-Neves   A. Queiros   J. González-Méijome,   J. Salgado-Borges  

Abstract Details


To measure the size of the light distortion surrounding a bright source of light as observed by pseudophakic patients implanted with a diffractive bifocal intra-ocular lens (IOL) in pseudophakic patients.


Clínica Professor Salgado Borges, Porto, Portugal


Nine patients with cataract (age 65±6 years, range: 58 to 69 years; 65% females) undergone facoemulsification followed by binocular pseudophakic IOL implantation with a diffractive IOL (AcrySof Restor, Alcon) by the same experienced surgeon (JS-B). 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 LED's 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. Three measures of light distortion were conducted in the tested eye (always monocularly) and then the result was automatically averaged by the software system attached to the hardware displaying the LED's.


Monocular light distortion value for the right eye was 60.9±22.5% (range: 21.75 to 93.9%). The binocular light distortion value was 39.6±17.8% (range: 16.4 to 80.1%). Differences between monocular and binocular values were statistically significant (p<0.05, Wilcoxon Signed Ranks Test). There was a significant correlation between the binocular summation (reduction in light distortion between monocular and binocular conditions) and the intraocular difference in the light distortion between right and left eye (Spearman Rho coefficient=0,801; p<0.001, Spearman correlation).


Pseudophakic patients implanted with diffractive bifocal IOLs present a significant degree of binocular summation and the binocular light distortion presented is about 30% lower than the monocular value. The binocular summation is higher when the inter-ocular difference in light distortion is lower. Symmetry in the level of light distortion improves the binocular attenuation of the light distortion. These preliminary results provide an explanation for the lower level of complains despite the high level of monocular light distortion presented after diffractive IOL implantation. FINANCIAL INTEREST: One of more of the authors... research is funded, fully or partially, by a company producing, developing or supplying the product or procedure presented

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