Posters

Effect of residual astigmatism in light distortion after cataract surgery with monofocal aspheric IOL

Poster Details

First Author: J.Salgado-Borges PORTUGAL

Co Author(s):    C. Borges   L. Dias   H. Ferreira-Neves   A. Queiros   M. Monteiro   J. González-Méijome

Abstract Details

Purpose:

To measures the size of the light distortion surrounding a bright source of light as observed by pseudophakic patients implanted with monofocal aspheric intra-ocular lens (IOL) with and without residual astigmatism.

Setting:

Ophthalmology, CHEDV, Sta. Maria da Feira, Portugal

Methods:

Sixty-five cataractous 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 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. A sample of 25 presbyopic patients aged 45-60 years of age without media opacities were also measured as reference or control population

Results:

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. Light distortion value was 24±16% for the whole sample and was negatively correlated with the power of the IOL such that more myopic eyes presented a trend towards higher values of light distortion. In patients with residual astigmatism of 0.75 or higher the average halo size was 27±15% while in patients with residual astigmatism below 0.75 or no astigmatism present the average distortion was significantly lower at 18±10% (p<0.001), Kruskall-Wallis). For the reference population of presbyopes without (mean age 51±4 [range: 45-60 years], the size of the light distortion was 14+/-14% being significantly lower compared to those pseudophakic patients with astigmatism but not different from those with low or no residual astigmatism.

Conclusions:

Even lower values of residual astigmatism after cataract surgery might affect visual quality under certain test conditions. Pseudophakic patients implanted with monofocal aspheric IOLs after cataract extraction present a significantly higher halo size when residual astigmatism between 0.75 and -1.50 D is left uncorrected. The methodology used in this study allowed us to quantify visual complains under low light conditions, in otherwise successfully operated pseudophakic patients. FINANCIAL INTEREST: NONE