Brain correlates of adaptation to multifocal contact lenses.

One common option to correct presbyopia is providing simultaneous images with multifocal contact lenses (MCLs). However, patient satisfaction with MCLs is not uniform and fully predictable and it might be modulated by neuroadaptation mechanisms. Using another technique to correct presbyopia with CLs called monovision, the visual evoked potential (VEP) evidenced, after a short period of adaptation to monovision, a compensatory activity in anterior cortical areas used to counteract the degraded V1 signal induced by this kind of correction. This compensatory activity was considered cognitive rather than sensorial. The purpose of the present study was to explore, with the use of VEP with a high-density electrode array, whether this kind of compensation in anterior cortical areas of the brain is present in presbyopes corrected with MCLs too. Multifocal presbyopia corrections produced a loss of feedforward activity in the primary visual cortex but no mod-ulation over anterior cortical areas as the one recorded in monovision. This result suggests that the possible nature of neural compensation for MCLs is not cognitive as in monovision.