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Neuroadaptation to glare in patients with multifocal IOLs: functional imaging results

Poster Details

First Author: J.Costa PORTUGAL

Co Author(s):    A. Rosa   A. Miranda   E. Almeida   F. Silva   C. Miguel   J. Murta     

Abstract Details


Controversy exists regarding the influence of neuroadaptation after cataract surgery with multifocal intraocular lens (IOLs) implantation, particularly regarding dysphotopsia. Multifocal IOLs are thought to induce changes in patient�â�€�™s capability of processing visual stimuli, yet the structure and function of the visual cortex in these patients has never been studied before. We performed a clinical study, using magnetic resonance imaging (MRI), with the purpose of learning about the impact of glare in the visual cortex at the first postoperative month in comparison with the 6th month, in a cohort of patients with multifocal lenses.


Department of Ophthalmology, Centro Hospitalar e Universit�Ã�¡rio de Coimbra (CHUC), Coimbra, Portugal; Institute of Nuclear Sciences Applied to Health (ICNAS), University of Coimbra, Coimbra Portugal


Prospective cohort study including 30 patients who underwent sequential bilateral implantation of a multifocal IOL (ReSTOR SN6AD1, Alcon), along with a nonintervention control group (n=15). Structural and functional MRI were performed at the 3rd postoperative week and at the 6th postoperative month. All patients underwent 2 structural acquisition sessions to obtain high-resolution tridimensional anatomical images, followed by 3 functional sessions. The functional stimulus consisted in a sinusoidal grating with spatial frequency of 10 cycles per degree (cdp) and 3 different contrast levels. In half of the runs a light source was present around the sinusoidal grating to induce disability glare.


Glare decreased the blood-oxygen-level dependent (BOLD) signal response to the functional stimulus in the primary visual cortex in the IOL group. The magnitude of the differences in peak BOLD (�Î�²max) values between glare and no-glare conditions was significantly greater for patients than for controls (effect sizes 0.49 and 0.10, respectively). Both �Î�²max and AUC (area under the curve) for threshold contrast events under glare showed a significant decrease in the IOL group. At 6 months post-op, the impact of glare in the BOLD signal was significantly attenuated (�Î�²max 0.140 vs. 0.115 without glare). No significant changes were observed in controls.


Glare disability was objectively measured at the cortical level in patients with multifocal lenses. Patients had a decrease and a delay in BOLD signal, whereas this was not found for controls, confirming the subjective difficulties in the early post-op period reported by most patients. However, at 6 months, there was a recovery of the BOLD signal, confirmed by psychophysical tests, suggesting an important role for neuroadaptation in this setting.

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