Ophthalmology, September 2017
Dysphotopsia manifestations are a source of patient dissatisfaction with multifocal intraocular lenses (IOLs), leading to explantation in some cases. Studies of optical parameters have shed little light on the pathophysiology of these effects. However, Rosa et al. observed an association between subjective visual symptoms and functional magnetic resonance imaging (fMRI) findings, indicating that neuroadaptive mechanisms play a role.
Their cross-sectional study involved 30 patients (mean age, 61 years; 16 women) who had undergone bilateral cataract surgery and implantation of diffractive IOLs 3 to 4 weeks earlier (patient group) and a control group of 15 age- and sex-matched subjects with no previous intraocular surgery. All participants underwent fMRI while viewing low-contrast grating stimuli, which, in half the runs, were surrounded by a light source to induce glare. The main outcome measure was activity in the primary visual cortex and higher-level brain areas, including the attention network. The researchers also evaluated psychophysical factors, visual acuity, wavefront, and scores on the Quality of Vision (QoV) questionnaire.
When patients viewed low-contrast stimuli with glare, substantial activation of the frontal, middle frontal, parietal frontal, and postcentral gyrus was observed. Under the same conditions, control subjects demonstrated deactivation only of visual areas in the occipital lobe and middle occipital gyrus. Relative to controls, patients exhibited stronger recruitment of the cortical areas involved in learning, task planning, and problem solving. Patients who were “more bothered” by the dysphotic symptoms from stimuli with glare showed significant recruitment of the frontal and parietal lobes, cingulate gyrus, and caudate nucleus. No correlation was found, in either group, between QoV scores and optical properties such as total and higher-order aberrations, modulation transfer function, and Strehl ratio.
The authors concluded that an association exists between patient-reported difficulties and fMRI findings, independent of optical parameters and psychophysical performance. The increased activity in the cortical areas devoted to attention, learning, cognitive control, and task planning may suggest that neuroadaptation to the IOL is under way.
The original article can be found here.