Functional magnetic resonance imaging to assess neuroadaptation to multifocal intraocular lenses.

PURPOSE

To evaluate the use of functional magnetic resonance imaging (MRI) to assess neuroadaptation to multifocal intraocular lenses (IOLs).

SETTING

Faculty of Medicine, University of Coimbra, Coimbra, Portugal.

DESIGN

Prospective case study.

METHODS

Patients with bilateral diffractive IOL implantation after cataract surgery had functional MRI at postoperative intervals of 3 weeks and 6 months. A nonintervention control group was included as proof of concept. Functional stimuli consisted of sinusoidal gratings with threshold contrast and a light source to induce disability glare. Subjective quality of vision and reading performance were assessed and wavefront analyses were performed.

RESULTS

The study comprised 30 patients in the study group and 15 in the control group. Glare decreased the functional MRI signal measured for sinusoidal gratings initially (3 weeks) but not at 6 months (P = .04), which was confirmed by contrast detection under glare improvement (P = .002). Patients showed increased activity of cortical areas involved in visual attention, procedural learning, effortful cognitive control, and goal-oriented behavior in the early postoperative period, which normalized at 6 months. There were no differences in aberrations, Strehl ratio, or modulation transfer function despite significant decreases in questionnaire symptom scores and visual acuity and reading performance improvements. The control group remained unchanged.

CONCLUSIONS

Neuroadaptation to multifocal IOLs took place initially through recruitment of visual attentional and procedural learning networks. Thereafter, a form of long-term adaptation/functional plasticity occurred, leading to brain activity regularization toward a non-effort pattern. These findings, which reinforce the crucial role of higher-level brain regions in the perceptual construction of vision, were consistent with functional and questionnaire outcomes and were unrelated to optical properties.