Rehabilitative techniques

Fractal Phototherapy in Maximizing Retina and Brain Plasticity

The neuroplasticity potential is reduced with aging and impairs during neurodegenerative diseases and brain and visual system injuries. This limits the brain's capacity to repair the structure and dynamics of its activity after lesions. Maximization of neuroplasticity is necessary to provide the maximal CNS response to therapeutic intervention and adaptive reorganization of neuronal networks in patients with degenerative pathology and traumatic injury to restore the functional activity of the brain and retina.Considering the fractal geometry and dynamics of the healthy brain and the loss of fractality in neurodegenerative pathology, we suggest that the application of self-similar visual signals with a fractal temporal structure in the stimulation therapy can reactivate the adaptive neuroplasticity and enhance the effectiveness of neurorehabilitation. This proposition was tested in the recent studies. Patients with glaucoma had a statistically significant positive effect of fractal photic therapy on light sensitivity and the perimetric MD index, which shows that methods of fractal stimulation can be a novel nonpharmacological approach to neuroprotective therapy and neurorehabilitation. In healthy rabbits, it was demonstrated that a long-term course of photostimulation with fractal signals does not harm the electroretinogram (ERG) and retina structure. Rabbits with modeled retinal atrophy showed better dynamics of the ERG restoration during daily stimulation therapy for a week in comparison with the controls. Positive changes in the retinal function can indirectly suggest the activation of its adaptive plasticity and the high potential of stimulation therapy with fractal visual stimuli in a nonpharmacological neurorehabilitation, which requires further study.

An Overview of Preferred Retinal Locus and Its Application in Biofeedback Training for Low-Vision Rehabilitation

Central vision loss (CVL) caused by macular damage generally disables common daily tasks, which cannot be reversed by present treatments. Fortunately, it has been found that biofeedback training by inducing or reinforcing preferred retinal locus (PRL) as an eccentric fixation reference contributes to the improvement of visual performance in patients with CVL. However, the clinical application is still under controversy due to poor knowledge of its fundamental and inconsistent practical standards. This article aims to summarize the possible rationale for the development, location, re-location and evaluating indicators of PRL, and the general apparatus, protocol, and outcome of biofeedback PRL training.

Characteristics of Preferred Retinal Locus in Eyes with Central Vision Loss Secondary to Different Macular Lesions

OBJECTIVE

Preferred retinal locus (PRL) training has been applied to low-vision rehabilitation for patients with central vision loss (CVL). This study aimed to explore the characteristics of a natural PRL in eyes with different macular lesions. The data may be useful in customizing training programs.

METHODS

A total of 72 eyes with CVL were included and assigned into two groups. In group A, 29 eyes diagnosed with macular holes featured relatively sharp borders and small areas of lesions. In group B, 44 eyes showed lesions characterized by irregular borders and large areas. The PRL location relative to a scotoma in the retina, fixation stability, and the average threshold surrounding the PRL were determined and compared between the two groups.

RESULTS

In group A, the PRL was located above in 48.28%, below in 27.59%, left in 62.07%, right in 31.03%, and inside in 3.45% of the eyes. In group B, the PRL was located above in 39.53%, below in 4.65%, left in 44.19%, right in 6.98%, and inside in 27.91% of eyes. The amount of retinal displacement occurring within 1° from an initial reference point (P< .05) and the 95% bivariate contour ellipse area (P< .05) in group A were respectively higher and lower than those in group B. However, the average thresholds around the PRLs in the two groups showed no significant difference (P > .05).

CONCLUSIONS

A PRL to the left of or above a scotoma tends to develop to avoid the right and inferior field defect, regardless of the scale and boundary of lesions. Although light sensitivity around a PRL shows no relation to lesion features, fixation stability is worse in irregular and large lesions.

Association of Vision-related Quality of Life with Visual Function in Age-Related Macular Degeneration

The purpose of this study was to assess which visual function measures are most strongly associated with vision-related quality of life (VRQoL) in age-related macular degeneration (AMD). A cross-sectional study of subjects with early AMD (n = 10), intermediate AMD (n = 42) and late AMD (n = 38) was conducted. Subjects were interviewed with the Impact of Vision Impairment (IVI) questionnaire. Functional tests performed included best-corrected visual acuity (BCVA), low luminance visual acuity (LLVA), visual acuity measured with the Moorfields Acuity Charts (MAC), contrast sensitivity, reading speed, mesopic and dark-adapted microperimetry. The relationship between VRQoL and visual function was assessed with multiple regressions controlling for confounders. Rasch analysis demonstrated the validity of the IVI to assess VRQoL through three subscales: reading and accessing information, mobility and independence, and emotional well-being. Subjects with late AMD had significant lower IVI scores on all subscales compared with intermediate and early AMD (p < 0.011). In the overall cohort, IVI subscales were associated with BCVA, LLVA, MAC-VA and contrast sensitivity (all p < 0.001). Among the subgroup of early and intermediate AMD subjects, reading and mobility subscales were significantly associated with MAC-VA (p < 0.013). These results suggest that MAC-VA is a useful, patient-relevant measure of visual impairment in AMD.

Postural control in blind individuals: A systematic review

Postural control (PC) requires the interaction of the three sensory systems for a good maintenance of the balance, and in blind people, lack of visual input can harm your PC. Thus the objective is to perform a literature review concerning role of sight in the maintenance of PC and the adaptation of brain structures when vision is absent. Studies were searched from Pubmed, and EMBASE that included individuals with congenital blindness. Articles studying person with acquired blindness or low vision was excluded from this review. 26 out of 322 articles were selected for review, and we found that 1) blind individuals exhibit PC deficits and that is compensated by the intensification of the remaining systems; 2) Neuroplastic adaptation occurs throughout the entire cerebral cortex; and 3) Sensorimotor stimulation and transcranial direct current stimulation seem to be a rehabilitation strategy. According to this review, the findings suggest that improved remaining sensations in the presence of adaptations and neuroplasticity, does not translate into better postural control performance. Regarding rehabilitation strategies, more studies are needed to show which therapeutic modality best contributes to postural control.

Vision Rehabilitation in Patients with Age-related Macular Degeneration

Background

The aim of this study was to investigate the rehabilitative process and visual rehabilitation outcomes in patients with central vision loss due to age-related macular degeneration (AMD).

Methods

Ninety-five subjects with AMD selected from the attendees of the National Centre of Services and Research for the Prevention of Blindness and Rehabilitation of Low Vision Patients—International Agency for Prevention of Blindness—IAPB Italia Onlus, were evaluated for this retrospective study. Low vision examination included psychological counseling, best corrected visual acuity (BCVA), near visual acuity, Pelli-Robson contrast sensitivity, and fixation stability analysis. Once the clinical assessment was completed, patients attended a low-vision rehabilitative pathway based on visual stimulation, devices training and, if needed, psychological support. Required magnification and reading speed were also evaluated.

Results

For the whole sample, the mean BCVA of the better eye was 0.7 (±0.2) LogMAR and of the worse eye was 1 (±0.2) LogMAR. Restoring reading ability was the most important focus for the patients examined as it was requested by 85% of the whole sample. Mean power of optical magnifying aids for near activities was 10.6 (±9.1) positive spherical diopters. Mean reading speed for the whole sample was 33.1 (±18.2) words per minute (wpm) before visual rehabilitation sessions and increased to 55.2 (±33.1) wpm after visual rehabilitation path. To cope with distance difficulties, 78 distance refractive correction, 10 Galilean telescopes, and 7 Keplerian telescopes were prescribed. For intermediate distance activities, 22 compensation lenses and 10 Galilean telescopes were suggested. Moreover, PC magnifier softwares were prescribed to nine patients. Sixty-five polarized medical filters were prescribed to reduce glare of sunlight. Because of unstable fixation in their better eye (32.3% (±19.7) within 2° circle and 54.8% (±22.9) within 4° circle) and visual acuity < 1.2 LogMAR in the fellow eye, 38 subjects, before starting the devices training sessions, attended a bio-feedback rehabilitation session with flickering pattern stimulus. In these subjects, fixation stability increased significantly to 75.6 (±14.9) within 2° and 89.4 (±19.5) within 4° ( P < 0.05), respectively.

Conclusions

Attending a customized low-vision intervention based on a multidisciplinary approach seems to be effective for improving visual functions in AMD. Both optical/electronic magnifiers and specific visual stimulation program can enhance visual performances.

Visualizing the blind brain: brain imaging of visual field defects from early recovery to rehabilitation techniques

Visual field defects (VFDs) are one of the most common consequences observed after brain injury, especially after a stroke in the posterior cerebral artery territory. Less frequently, tumors, traumatic brain injury, brain surgery or demyelination can also determine various visual disabilities, from a decrease in visual acuity to cerebral blindness. Visual field defects is a factor of bad functional prognosis as it compromises many daily life activities (e.g., obstacle avoidance, driving, and reading) and therefore the patient's quality of life. Spontaneous recovery seems to be limited and restricted to the first 6 months, with the best chance of improvement at 1 month. The possible mechanisms at work could be partly due to cortical reorganization in the visual areas (plasticity) and/or partly to the use of intact alternative visual routes, first identified in animal studies and possibly underlying the phenomenon of blindsight. Despite processes of early recovery, which is rarely complete, and learning of compensatory strategies, the patient's autonomy may still be compromised at more chronic stages. Therefore, various rehabilitation therapies based on neuroanatomical knowledge have been developed to improve VFDs. These use eye-movement training techniques (e.g., visual search, saccadic eye movements), reading training, visual field restitution (the Vision Restoration Therapy, VRT), or perceptual learning. In this review, we will focus on studies of human adults with acquired VFDs, which have used different imaging techniques (Positron Emission Tomography, PET; Diffusion Tensor Imaging, DTI; functional Magnetic Resonance Imaging, fMRI; Magneto Encephalography, MEG) or neurostimulation techniques (Transcranial Magnetic Stimulation, TMS; transcranial Direct Current Stimulation, tDCS) to show brain activations in the course of spontaneous recovery or after specific rehabilitation techniques.

An FMRI investigation of the cortical network underlying detection and categorization abilities in hemianopic patients

The current study aims to investigate visual scene perception and its neuro-anatomical correlates for stimuli presented in the central visual field of patients with homonymous hemianopia, and thereby to assess the effect of a right or a left occipital lesion on brain reorganization. Fourteen healthy participants, three left brain damaged (LBD) patients with right homonymous hemianopia and five right brain damaged (RBD) patients with left homonymous hemianopia performed a visual detection task (i.e. "Is there an image on the screen?") and a categorization task (i.e. "Is it an image of a highway or a city?") during a block-designed functional magnetic resonance imaging recording session. Cerebral activity analyses of the posterior areas-the occipital lobe in particular-highlighted bi-hemispheric activation during the detection task but more lateralized, left occipital lobe activation during the categorization task in healthy participants. Conversely, in patients, the same network of activity was observed in both tasks. However, LBD patients showed a predominant activation in their right hemisphere (occipital lobe and posterior temporal areas) whereas RBD patients showed a more bilateral activation (in the occipital lobes). Overall, our preliminary findings suggest a specific pattern of cerebral activation depending on the task instruction in healthy participants and cerebral reorganization of the posterior areas following brain injury in hemianopic patients which could depend upon the side of the occipital lesion.

Treatment of homonymous visual field defects

OPINION STATEMENT

A clinical presentation of a retrochiasmal or homonymous visual field defect (HVFD) usually represents a permanent visual impairment. The visual and functional ramifications of HVFD will vary by patient. Comprehensive care-the clinical evaluation and consideration for treatment of HVFD-includes vision rehabilitation provided by optometrists, occupational therapists, or ophthalmologists. On the basis of individual patient needs, the eye care practitioner typically uses one or both of the following approaches to treat the HVFD: (1) field enhancement (also referred to in the literature as "field expansion"), in which optical systems incorporating prism are prescribed to optimize the use of the remaining vision, and (2) rehabilitative techniques including saccadic training ("compensation training") or vision restorative therapy ("restitution training"). Although lacking in strength, the evidence does support benefits from field enhancement and saccadic training for patients with HVFD, but vision restorative therapy has not been shown to be an effective option.