Visual training may ease neuroadaptation to presbyopia-correcting IOLs

Neuroadaptation is the process by which the brain learns to interpret and adjust to new visual information. When vision changes or difficulties arise in processing certain stimuli—as happens after cataract surgery with implantation of presbyopia-correcting intraocular lenses (IOLs)—the brain needs time to reorganize and optimize how it processes those images. During the first few weeks after surgery, this process demands greater cerebral effort related to attention, visual interpretation and learning new processing strategies. Over time, thanks to brain plasticity, vision becomes more natural and automatic, reducing the effort needed for everyday tasks such as reading, focusing or perceiving details and contrasts.

The process of neuroadaptation is initiated with increased activity in the top-down attentional network, cingulate cortex and caudate nucleus in the first three weeks after surgery, which evolves to a cortical regularization of activity towards a non-effort pattern.^1,2 However, in some cases this adaptation does not complete properly, which can lead to visual fatigue, discomfort or reduced quality of vision.

Research indicates that patients with presbyopia-correcting IOLs can experience enhanced visual function through targeted visual training programmes, pointing to the value of this strategy in supporting or speeding neuroadaptation.^3-6 Kaymak and colleagues⁵ published findings on computer-based visual training in multifocal IOL patients (both diffractive bifocal and apodized diffractive lenses), training only one eye while leaving the other untrained as a comparison. Despite shortcomings in their rehabilitation protocol—it lacked gamification and relied on sinusoidal gratings without properly smoothed edges—they still observed gains across several visual measures.⁵ In recent years, new developments have emerged that help facilitate neuroadaptation through gamified applications built around the use of Gabor patches.

Training the eye—and the brain—to adapt

A novel visual training technology (OPTIcTRAIN; Proconsi S.L.) is built around a serious game framed as a driving simulation, in which users steer left or right to avoid colliding with vehicles and obstacles along the road. Periodically during the drive, a Gabor stimulus appears on the roadway, prompting the user to indicate its orientation; the stimulus then disappears once a response is given or after five seconds elapse without one (Figure 1). The contrast levels of these stimuli are adjusted according to a psychophysical algorithm.

The platform offers interactive, game-based exercises compatible with both tablets and smartphones, blending stimuli related to contrast sensitivity, visual discrimination and attentional focus within dynamic settings designed to keep users motivated. It also includes built-in evaluation and monitoring features that track visual progress over the course of training, encompassing contrast sensitivity assessments and, when desired, optional eye-tracking capabilities.

The visual training consists of home-based active visual training, playing the serious game during 20 sessions of 30 minutes per day (600 minutes in total).

Putting the technology to the test

A blinded, randomized, placebo-controlled, multicentre clinical trial (NCT04985097) was carried out to assess the effect of this visual training technology. Eligible participants were those who had undergone uncomplicated bilateral cataract surgery with trifocal diffractive IOL implantation and who agreed to complete a visual training programme shortly after surgery. Participants were randomly allocated to either the visual training programme (study group) or a placebo programme following surgery (placebo group). The examiner remained unaware of which type of training each participant received—the game-based training using Gaussian-windowed sine-wave gratings, or the placebo software.

Sixty subjects were enrolled consecutively: 29 in the placebo group (12 men, 17 women) and 31 in the study group (10 men, 21 women). Average age was 65.73 ± 5.74 years in the placebo group versus 63.45 ± 5.78 years in the study group, a difference that did not reach statistical significance (P = .13). Every participant completed the programme and attended all scheduled visits, though adherence to training was not universally perfect. Average time spent training was 477.67 ± 208.92 minutes (range, 30–720) in the placebo group and 518.16 ± 63.92 minutes (range, 390–600) in the study group, a difference that was not statistically significant (P = .70).

Visual acuity outcomes—distance, intermediate and near—did not differ significantly between groups either before (P ≥ .11 for all comparisons) or after training (P ≥ .31 for all comparisons). However, the OPTIcTRAIN group showed a gain in uncorrected intermediate visual acuity not observed in the placebo group (P = .10). For contrast sensitivity, the study group demonstrated significantly superior binocular scores at spatial frequencies of 6 cycles/° (P = .01) and 12 cycles/° (P = .03) (Figure 2).

Quality of vision was also evaluated using the validated McAlinden et al questionnaire. Patients trained with the application reported a significant reduction in bothersomeness across a larger number of visual symptoms compared with the placebo group.

In addition to these clinical outcomes, resting-state functional magnetic resonance imaging (rs-fMRI) was conducted in a subset of 5 patients using a Philips Achieva 3.0T X-Series scanner. The imaging revealed changes consistent with a shift toward reduced neural effort, along with increased functional connectivity following training with the serious game. Before the intervention, stronger connectivity was seen between the right lateral occipital gyrus and right pars opercularis. After training, connectivity increased significantly in pathways involving the left parahippocampal gyrus, left isthmus of the cingulate gyrus, right insula and right pars triangularis (Figure 3).

In summary, this 3-week visual training programme based on Gabor patches, administered shortly after bilateral implantation of trifocal diffractive IOLs, improved contrast sensitivity and intermediate visual function, and helped alleviate symptom-related complaints. These functional gains were accompanied by underlying neural changes, suggesting a possible speeding-up of the neuroadaptation process.

A second chance for dissatisfied patients

The visual training technology’s clinical value has also been examined in a group of patients who received presbyopia-correcting IOLs and reported severe dissatisfaction with their visual quality. At the Department of Ophthalmology, Vithas Medimar International Hospital (Alicante, Spain), 7 eyes from 5 patients aged 29 to 64 years were enrolled, all of whom had undergone uncomplicated cataract surgery with various presbyopia-correcting IOL models but experienced a marked decline in visual quality and troublesome photic phenomena at least six months post-surgery. Every patient completed training with the application.

Mean corrected distance visual acuity rose from 0.20 ± 0.09 logMAR before training to 0.13 ± 0.08 afterward (P = .008). Distance-corrected near visual acuity similarly improved, from 0.34 ± 0.21 logMAR to 0.22 ± 0.21 (P < .001). Distance contrast sensitivity also showed significant gains at high spatial frequencies (P < .001, CSV1000 test), as did near contrast sensitivity at spatial frequencies of 1.5, 3, and 4.5 cycles/° (OPTIcTRAIN-CSF test) (P < .001). Bothersomeness from halos, glare and starbursts decreased across all patients following training (per the McAlinden quality-of-vision questionnaire), and hazy vision also lessened among those who had reported it.

These findings suggest that gamified visual training technology of this kind may offer a promising rehabilitation option for patients severely affected by vision-quality loss after presbyopia-correcting IOL surgery. Larger studies involving more symptomatic post-surgical patients would help confirm these results. Incorporating neurological assessments such as functional MRI in future work would also be valuable for verifying the neural changes underlying neuroadaptation.

David P. Piñero, PhD

E: [email protected]

David P. Piñero, PhD, is with the Group of Optics and Visual Perception in the Department of Optics, Pharmacology and Anatomy at the University of Alicante, and is affiliated with the Department of Ophthalmology at Vithas Medimar International Hospital, both in Alicante, Spain. He is also the founder and a shareholder of Visitrain S.L., based at the Science Park of the University of Alicante, which distributes the OPTIcTRAIN software.

References

1. Rosa AM, Miranda ÂC, Patrício M, et al. Functional magnetic resonance imaging to assess the neurobehavioral impact of dysphotopsia with multifocal intraocular lenses. Ophthalmology. 2017;124(9):1280-1289. doi:10.1016/j.ophtha.2017.03.033

2. Rosa AM, Miranda ÂC, Patrício MM, et al. Functional magnetic resonance imaging to assess neuroadaptation to multifocal intraocular lenses. J Cataract Refract Surg. 2017;43(10):1287-1296. doi:10.1016/j.jcrs.2017.07.031

3. Piñero DP, Maldonado-López MJ, Molina-Martin A, et al. Randomised placebo-controlled clinical trial evaluating the impact of a new visual rehabilitation program on neuroadaptation in patients implanted with trifocal intraocular lenses. Int Ophthalmol. 2023;43(11):4035-4053. doi:10.1007/s10792-023-02809-9

4. Piñero DP, Molina-Martin A, Ramón ML, et al. Preliminary evaluation of the clinical benefit of a novel visual rehabilitation program in patients implanted with trifocal diffractive intraocular lenses: a blinded randomized placebo-controlled clinical trial. Brain Sci. 2021;11(9):1181. doi:10.3390/brainsci11091181

5. Kaymak H, Fahle M, Ott G, Mester U. Intraindividual comparison of the effect of training on visual performance with ReSTOR and Tecnis diffractive multifocal IOLs. J Refract Surg. 2008;24(3):287-293. doi:10.3928/1081597X-20080301-11

6. Mester U, Fahle M, Ott G, Kaymak H. Funktionstraining nach MIOL-Implantation [Functional vision training after MIOL implantation]. Ophthalmologe. 2008;105(6):533-537. doi:10.1007/s00347-008-1746-7