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

Abstract

Purpose : Controversy exists regarding the influence of neuroadaptation after cataract surgery with multifocal intraocular lens implantation, especially where dysphotopsia are concerned (halos, glare and starburst).
We performed a prospective observational clinical study to learn about changes in the visual cortex at the first postoperative month compared with the 6^th month in a cohort of patients with multifocal lenses.

Methods : Prospective cohort study, including 30 patients who underwent sequential bilateral implantation of a diffractive multifocal intraocular lens (ReSTOR SN6AD1, Alcon). A nonintervention control group (n=11) was also included as a proof of concept. Structural and functional MRI was performed at the 4th postoperative week and at the 6^th 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 10 cdp and 3 different 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 then processed with the BrainVoyager QX software.

Results : High-resolution retinotopic maps were successfully acquired in the two groups.
In the presence of glare, there was a decrease in the BOLD signal obtained for the sinusoidal grating comparing to viewing the same grating without glare. There was also a delay in the time to achieve the maximum BOLD signal in the presence of the glare source. The control group had no decrease in the BOLD signal and no delay in the maximum BOLD signal under glare.
At 6 months post-op there was an increase in the BOLD signal obtained under glare conditions for the multifocal group, comparing to the early post-operative month.

Conclusions : Glare disability was objectively measured at the cortical level in patients with multifocal lens. 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 20-40% of the BOLD signal, suggesting an important role for neuroadaptation/neuroplasticity in this setting.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.