Functional magnetic resonance imaging as an innovative tool to assess neuroadaptation after cataract surgery

Session Details

Session Title: Quality of Vision and Dry Eye

Session Date/Time: Sunday 08/10/2017 | 08:00-09:30

Paper Time: 08:48

Venue: Room 3.4

First Author: : A.Rosa PORTUGAL

Co Author(s): :    A. Miranda   A. Martins   M. Patricio   M. Castelo-Branco   J. Murta        

Abstract Details

Purpose:

Symptoms collectively referred to as dysphotopsia (halos, glare and starburst) are important causes of dissatisfaction with multifocal intraocular lens (IOLs). Dysphotopsia tends to improve over time due to neuroadaptation. The purpose of this study was to assess changes in the human cortex during a 6-month follow up after multifocal IOL implantation. To that end, functional Magnetic Resonance Imaging (fMRI), a non-invasive method in which there is an increase in blood oxygenation level dependent (BOLD) signal with brain activity, was used.

Setting:

Department of Ophthalmology, Centro Hospitalar e Universitário de Coimbra, Portugal. IBILI, Faculty of Medicine, University of Coimbra, Portugal. ICNAS, Faculty of Medicine, University of Coimbra, Portugal

Methods:

Prospective cohort study including 30 patients with sequential bilateral implantation of a diffractive multifocal IOL (ReSTOR SN6AD1, Alcon). A nonintervention control group (n=15) was also included as proof of concept. Structural and functional MRI scans were performed at the 3rd postoperative week and 6th postoperative month. Subjects underwent structural and retinotopy scans. The functional stimuli consisted in sinusoidal gratings with a spatial frequency of 10cdp and threshold contrast. Half of the runs included a light source around the sinusoidal grating to induce disability glare. A quality of vision questionnaire and a wavefront assessment with iTrace were also performed.

Results:

Glare decreased the BOLD signal obtained for the sinusoidal grating at the first visit (p=0.040), but not 6 months later. This was confirmed by an improvement in contrast detection under glare between the first and last visit (p=0.002). Patients showed increased activity of cortical areas dedicated to attention (frontoparietal circuits), learning, cognitive control and task goals (cingulate, caudate) in the early post-operative period, which normalized at 6 months. No improvement occurred in optical properties (aberrations, Strehl ratio, modulation transfer function), despite a significant decrease of questionnaire scores at the second visit. The control group had similar values at both visits.

Conclusions:

Glare disability was objectively measured at the cortical level in patients with multifocal lenses. Under glare, patients had a decrease in the visual cortex BOLD signal in the early post-op period and activation of effort, learning and goal-oriented cortical areas. However, at 6 months there was a significant improvement in BOLD signal under glare, in contrast detection, questionnaire scores and effort network activation. This suggests an important role for cortical mechanisms in the improvement observed in multifocal patients, thus confirming, for the first time, the clinically accepted notion of neuroadaptation

Financial Disclosure:

NONE