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Phillip J. Buckhurst, James S. Wolffsohn, Sunil Shah, Shehzad Naroo, Leon N. Davies; Evaluation of Dysphotopsia with Multifocal Intraocular Lenses. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6185.
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To validate a new design of Halometer to examine the photopic scotoma resulting from multifocal IOL implantation.
The custom designed Halometer consisted of a bright LED mounted in the centre of an LCD screen with software to test the eccentricity at which randomized threshold visual acuity letters of different contrasts could be detected along 45 degree spokes. Light scatter was assessed in 20 healthy phakic subjects with Bangerter foils to simulate media opacities using the Halometer compared to the C-Quant (Oculus) repeated on three occasions by two examiners. Halometry and Straylight were also assessed on two occasions on 45 patients binocularly implanted with three types of IOLs: 15 bilateral Monofocal, 15 concentric fully diffractive and 15 sectorial refractive. The subjective perception of glare was assessed on a 1-10 Likert scale and by the patients indicating which illustration of dysphotopsia best depicted their experience of glare.
In the phakic subjects intraobserver variability (ICC=0.876) and inter-observer variability (ICC=0.776) was high using the new Halometer. There was an increase in Straylight (f1.551=80.655, p<0.001) and photopic scotoma (f1.799=29.564, p<0.001) with an increasing depth of Bangerter occlusion. The Intra-observer variability was also good in the pseudophakic groups (ICC=0.890). No differences in Straylight values were found between the IOL groups (f2=0.414, p=0.664). In the concentric diffractive IOL group the dysphotopsia was greater in all 8 meridians (p<0.05) and in the sectorial refractive IOL group it was greater only in the inferior 270 and 225 degree positions (p<0.05) in comparison with the monofocal IOL group. The subjective results demonstrated a higher level of dysphotopsia with the concentric diffractive group in comparison with the sectorial refractive (p<0.001)
The Halometer is a valid and repeatable instrument for the assessment of dysphotopsia. It provides an assessment of halo size and uniformity which relate to subjective descriptions of dysphotopsia. Concentric diffractive multifocal IOLs result in a uniform photopic scotoma, whereas sectorial refractive multifocal IOLs create a photopic scotoma in the position matching the orientation of the reading segment of the IOL.
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