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

Session Details

Session Title: Imaging I

Session Date/Time: Monday 12/09/2016 | 14:30-16:30

Paper Time: 16:12

Venue: Hall C2

First Author: : A.Rosa PORTUGAL

Co Author(s): :    A. Miranda   E. Almeida   M. Patricio   F. Silva   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 visual cortex during a 6 month follow up after multifocal IOL implantation. This was done using functional Magnetic Resonance Imaging (fMRI), a non-invasive method for studying brain activity in vivo.

Setting:

Department of Ophthalmology, Centro Hospitalar e Universitário de Coimbra, Portugal. IBILI, Faculdade de Medicina de Coimbra, Portugal. ICNAS, Faculdade de Medicina de Coimbra, Portugal.

Methods:

Prospective cohort study including 10 patients with sequential bilateral implantation of a diffractive multifocal IOL (ReSTOR SN6AD1, Alcon). A nonintervention control group (n=10) was also included as proof of concept. Structural and functional MRI scans were performed at the 3rd postoperative week and at the 6th postoperative month. Subjects underwent structural acquisition sessions 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. The anatomic and functional images were processed with BrainVoyager QX software.

Results:

Glare induced a delay and a decrease in the blood oxygenation level dependent (BOLD) signal obtained for the sinusoidal grating (βmax 0.12±0.05 and 0.09±0.04, without and with glare, respectively). The control group had no significant changes. There was an increase in the βmax (corresponding to the peak hemodynamic response after a stimulus is presented) in the primary visual cortex of multifocal patients and of the total BOLD signal at visit 2 comparing with visit 1 (βmax increased from 0.09 to 0.16, and area under the curve from 0.17 to 0.31, p<0.05). The same improvement was noticed in extraestriate visual areas.

Conclusions:

Glare disability was objectively measured at the cortical level in patients with multifocal lenses. Patients had a decrease and a delay in BOLD signal in the early post-op period. However, at 6 months there was a significant increase in BOLD signal in cortical areas V1, V2 and V3, suggesting 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