User:Aewb/Neural vision therapy

History of Neural Vision Therapy
Computer based neural vision therapy (NVT) is a non-invasive treatment modality that enhances eyesight neurologically. NVT has been used to improve the vision outcomes for post-cataract, post-refractive(LASIK), presbyopia, night vision, adult low near sighted (myopic), sports vision patients and amblyopic patients.

The NVT technology was originally developed in Israel in 1999. The U.S. Food and Drug Administration (FDA) monitored a prospective masked controlled study of this technology and (FDA 510(K)) approval was given in August 2001. The technology has successfully conducted U.S. clinical trials that replicate the international results. The company’s studies have been published in multiple peer reviewed scientific publications. The awareness and recognition of the company and the technology is consistently increasing in the U.S. and worldwide.

Scientific Background
The human visual system consists of a highly sophisticated optical processing system. Optical images from the retina travel through a hierarchy of progressive levels of visual processing, including photoreceptors and several stages of spatial integration, each forming receptive fields of increasing complexity. Contrast is one of the most important parameters triggering the neural activity in the visual cortex.1  Neural interactions determine contrast sensitivity at each spatial frequency. The combination of neural interactions at various spatial frequencies derives individual CSF.2 Experiments have shown that the response of individual neurons to repeated stimulus is highly variable (noise), this high noise level imposes a fundamental limitation on the reliable detection and discrimination of visual signals by individual cortical neurons.1,3-4 The brain pools response across many neurons to average out noise activity of single cells. This creates a signal to noise ratio (S/N ration) that determines detection and limits the CSF. Thus improvement of the signal-to-noise ratio, leads to substantially improved visual performance.5

Several studies have shown that the noise of individual cortical neurons can be modulated by appropriate choice of stimulus conditions and that contrast sensitivity at low levels can be increased through control of stimulus parameters. 8-11 The typical building block of the visual stimulus in the field of visual neuroscience is a Gabor patch which efficiently activates and matches the shape of receptive fields in the visual cortex. Polat and colleagues had demonstrated that contrast sensitivity at low levels can be increased dramatically through a “lateral masking” technique, where collinearly oriented flanking Gabors are displayed in addition to the target Gabor image.11 This lateral masking technique to is tailored to a individual computerized training regimen using various parameters of the stimulus (Gabors) such as spatial frequencies, spatial arrangement of the Gabor patches, contrast level, orientation (local and global), tasks order, context, exposure duration.1 Lateral masking improves neuronal efficiency and improvement of contrast sensitivity function (CSF) by reducing the noise to signal ratio of neural activity in the primary visual cortex.11

This precise control of stimulus conditions leading to increased neuronal efficiency is fundamental in initiating the neural modifications that are the basis for brain plasticity. Brain plasticity relates to the ability of the nervous system to adapt to changed conditions, sometimes after injury or strokes, but more commonly in acquiring new skills. Brain plasticity has been demonstrated in many basic tasks, with evidence pointing to physical modifications in the adult cortex during repetitive performance. 12-18 The term perceptual learning describes a process whereby practicing certain visual tasks leads to an improvement in visual performance. Brain plasticity in visual functions of adults has been shown in various studies, and it has been demonstrated that visual performance improves with repetitive practice on specific controlled visual tasks. 12-18 Through these precise controlled conditions, repetitive practice initiates neural modifications that lead to improvement in neuronal efficiency. These neural modifications indicate the presence of brain plasticity.12-18

Currently, the only commercially available computer based NVT is RevitalVision (Lawrence, Kan). This technology is a non-invasive, patient-specific, perceptual learning program based on visual stimulation. It facilitates neural connections at the cortical level through a computerized visual training regime using Gabor patches to improve contrast sensitivity and visual acuity. As visual perception depends on both the optical input received from the eye and the neural processing of that input in the visual cortex, RevitalVision technology improves quality of vision (contrast sensitivity and visual acuity) by enhancing neural processing in the primary visual cortex. The RevitalVision technology probes specific neuronal interactions, using a set of patient-specific stimuli that improve neuronal efficiency and induce improvement of CSF due to a reduction of noise and increase in signal strength. The improved lower level processing (contrast sensitivity and lateral interactions) produces an improvement in higher level processing such as letter recognition and visual acuity.

The technology has been clinically proven in the treatment of adult amblyopia which until now has been considered untreatable.19,22-23 In recent years the technology has been used in Asia and Europe where clinical studies showed efficacy in the treatment of amblyopia, low myopia and early presbyopia.19-21

Variability in efficacy has been found and may be a reflection of different individuals’ “final cortical potential” that could be achieved through the perceptual learning process, in turn dependent on the state of inherent neural plasticity. Follow up studies may be designed to address these issues and find optimal “exposure dosing”. However, individual effort invested and motivation will be expected to be different with resultant impact on variability of final result. Further studies may be designed to explore the role of this novel computerized visual cortex training program in the area of rehabilitation for the low vision with various ocular conditions, and its prospective role in the enhancement of visual potential for the better quality of vision.

Description of Computer Based Neural Vision Therapy Training
NVT training programs, such as RevitalVision, are interactive web-based computer software that provides a series of individualized visual stimuli designed to enhance the neural interactions in the visual cortex. Each training session lasts for approximately 20 minutes, during which the patient responds to visual perception tasks (VPTs) displayed on the computer screen. During the session the patient sits five feet from a computer monitor in a darkened room and a mouse is used to respond to the tasks. Because the program is web-based, the training is designed to be conducted at home.

The therapy is typically conducted at a pace of 2 to 3 training sessions a week over a course of 2 to 3 months and is completed after 20 sessions. Before beginning the 20 training sessions, patients complete two computerized evaluation sessions with the system to setup the baseline of individualized neural inefficiencies for the training program. This baseline information is used by the RevitalVision algorithms, together with the baseline examination results, to set the starting point for the training sessions.

The VPTs are patient-specific stimuli using Gabor patches displayed in lateral masking techniques directed to enhance specific neuronal inefficiencies in the visual cortex. During each treatment session, the patient is exposed to visual images displayed on a computer monitor. In a typical task, the patient is exposed to two consecutive displays in random order. Each display has some arrangement of Gabor patches with subtle difference between the two displays. The patient interactively communicates with the computer using a mouse. During the session, some data that reflects patient’s performance is recorded. The patient is required to identify the correct display as determined by the instructions for the specific task. If the patient answers correctly, the target contrast will be reduced and the task will become more difficult. Incorrect answers will trigger the program in increase the contrast and the task becomes easier.

During each treatment session, the patient is exposed to visual images displayed on a computer monitor. The patient interactively communicates with the computer using a mouse. After each training session, the patient performance in each of the VPTs is recorded and sent via internet to the RevitalVision servers. Special algorithms then analyze the patient performance and accordingly create the VPT parameters for the next training session. In this manner patients receive training sessions that are individually tailored to their performance and neuronal inefficiencies. The RevitalVision treatment System is a software-based, interactive system tailored and continuously adaptive to the individual patient’s learning and improvement. RevitalVision uses the internet as a distribution media, which allows the company to provide this personalized interactive service to a practically unlimited number of treatment locations. Some patients are required by the software algorithms to use training glasses during the sessions. These were -0.5D or -1.0D in power and in the form of eyeglasses for low myopes and emmetropic presbyopes or clip-on glasses for ammetropic presbyopes.

Summary of Clinical Studies
Thousands of clinical trial participants and patients of computer based NVT have reported significant improvement in their vision performance by two rows on the visual acuity eye chart, and 100% increase in contrast sensitivity, on average.

•	Polat et al. studied 54 adult amblyopic patients who were randomized to amblyopic NVT treatment or a placebo vision-training program. Pretreatment visual acuity in both study arms was 0.42 logMAR, and this improved by 2.5 lines to 20/30 in the CRT treatment group, with no improvement in the control group. This increase in acuity was corroborated by a commensurate increase in CSF to within the normal range. These improvements in acuity and CSF were sustained after 12 months.19 •	Tan et al. reported mean improvement of 2.8 logMar lines in distance unaided visual acuity (UAVA) for 55 low myopes and mean improvement of 1.6 logMar lines in near UAVA for the 41 presbyopes (age 41-55 year old) after completion of the NVT training. The improvements were shown to be retained for at least 12 months.20 •	Tan et al. conducted a randomized controlled trial evaluating the efficacy of NVT in low myopia. The results confirmed that statistically significant difference in unaided visual acuity between the masked treatment groups and suggested on completion of the NVT was likely to provide the definitive evidence of efficacy and safety of NVT treatment in improving visual acuity and contrast sensitivity function in adult low myopes. The results of this study correlate well with NVT reported commercial results - mean improvement of 2.6 logMar lines of distance uncorrected visual acuity for low myopes, 2.0 logMar lines near unaided visual acuity for early presbyopes.21 •	Durrie et al. evaluated seventeen patients with low myopia (up to -1.75D) and 21 patients with early presbyopia (up to +2.50D Add) in 2 clinical sites who underwent NVT. Eleven myopic and 18 presbyopic patients underwent NVT while 9 patients performed visual examinations only serving as a control group. Researchers found the low myopia treatment group achieved a mean improvement of 2.2 logMAR lines in UAVA. CSF improved at all spatial frequencies. In this arm of the study the control patients did not shown any significant change in vision. The early presbyopia treatment group achieved a mean improvement of 2.2 logMAR lines in near UAVA. Near UCSF also improved at all spatial frequencies. The control patients in this arm have not shown any significant change in vision. Additionally, the mean refractive error in all groups remained unchanged after treatment.24 •	Lim et al. reported a single case of NVT for the treatment low myopic regression five years after myopic LASIK. The patient improved 2.8 lines in the right eye and 1.6 lines in the left eye following NVT.25 •	Durrie et al. conducted a prospective, randomized, multicenter placebo controlled study comparing CRT after LASIK (“NeuroLASIK”) to sham treatment (video game) following LASIK in 98 eyes. Researchers found 0.8 Snellen lines of UAVA and 79% improvement in contrast sensitivity in the treatment group relative to a 0.28 line improvement and 52% improvement in CSF in the control group. Patients who were worse than 20/20 after LASIK improved 1.56 Snellen lines of UAVA and 90% improvement in CSF with NVT relative to the 0.34 lines and 47% CSF improvement in the control group. The results suggested that patients who had worse vision improved more and that perhaps there is a cortical limit to how much a patient can improve.26