Posters

Cortical response to glare source in patients implanted with multifocal IOLs

Poster Details

First Author: A. Martins PORTUGAL

Co Author(s):    A. Rosa   E. Almeida   J. Costa   Ã. Miranda   J. Murta   M. Castelo-Branco     

Abstract Details

Purpose:

Important causes of dissatisfaction with multifocal intraocular lens (IOLs) are symptoms collectively referred to as dysphotopsia (halos, glare and starburst). Dysphotopsia are difficult to evaluate clinically, as there is often no correlation between subjective symptoms and objective measurements. Functional magnetic resonance imaging is a non-invasive method for studying brain activity in vivo. The purpose of this study was to evaluate the visual cortex and the cortical effort networks of patients implanted with multifocal IOLs at the early post-operative period.

Setting:

Centro Hospitalar e Universitário de Coimbra

Methods:

Prospective cohort study, including 10 patients who underwent sequential bilateral implantation of a diffractive multifocal IOL (ReSTOR SN6AD1, Alcon). Structural and functional MRI was 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 retinotopy scans. The functional stimuli consisted in a sinusoidal grating with spatial frequency of 10cdp and threshold contrast levels. In half of the runs a light source was present around the sinusoidal grating to induce disability glare. The anatomic and functional images were processed with the BrainVoyagerQX software.

Results:

High-resolution retinotopic maps were successfully acquired in both groups. In the presence of glare, there was a decrease in the BOLD (blood oxygenation level dependent) signal obtained for the sinusoidal grating comparing to viewing the same grating without glare (Beta max 0.12±0.05 and 0.09±0.04, without and with glare, respectively). There was also a delay in the time to achieve the maximum BOLD signal in the presence of the glare source. There was also activation of frontal operculum, basal ganglia and putamen, only when the light source was on. These areas are activated in difficult tasks and in non-automated tasks.

Conclusions:

The impact of glare was objectively demonstrated in the early postoperative period after cataract surgery with multifocal IOLs. Patients had a decrease and a delay in BOLD signal in the visual cortex. Effort related networks, i.e, cortical areas that are activated when a subject performs a difficult task were also activated, together with adaptation circuits involved in goal oriented tasks, reflecting that basic adaptation circuits are triggered early in the postoperative period after multifocal IOL implantation.

Financial Disclosure:

NONE