Transcript Document

Pilot Study To Evaluate The Efficacy of Neural Vision Correction™ (NVC™) Technology For Vision Improvement in Low Myopia
Donald Tan 1,2,3, Bill Chan 1, Frederick Tey 4, Lionel Lee 4
Singapore Eye Research Institute Singapore National Eye Centre
5
Defence Medical & Environmental Research Institute , Singapore.
-----------------Introduction-----------------NeuroVision’s NVC vision correction technology is a non-invasive, patient-specific
treatment based on visual stimulation and facilitation of neural connections
responsible for vision. The technology involves the use of an internet-based
computer generated visual training exercise regime using sets of patient specific
stimuli based on Gabor patches, to sharpen contrast sensitivity and visual acuity.
2;
Department of Ophthalmology, Faculty of Medicine, National University of Singapore
The results shown in Figures 3,4 are derived from subjects (adults), who were exposed to
psychophysical tasks using the “Lateral Masking” technique.
Figure 3:
When subjects are
practicing contrast
modulation under a
very precise and
subject-specific stimuli
regimen, a dramatic
improvement in contrast
sensitivity is achieved
We evaluated the efficacy of NVC treatment in the enhancement of unaided visual
acuity (UAVA) and contrast sensitivity function (CSF) in low myopes.
-----------------Scientific Background-----------------Cortical neurons in the visual cortex function as highly specialized image analyzers or filters,
responding only to specific parameters of a visual image, such as orientation and spatial
frequency, and visual processing involves the integrated activity of many neurons, with interneural
interactions effecting both excitation and inhibition1. Visual contrast activates neurons involved in
vision processing, and neural interactions determine the sensitivity for visual contrast at each
spatial frequency, and the combination of neural activities set Contrast Sensitivity Function
(CSF)1,2. The relationship between neuronal responses and perception are mainly determined by
the signal-to-noise ratio (S/N ratio) of neuronal activity, and the brain pools responses across many
neurons to average out noisy activity of single cells, thus improving S/N ratio, leading to improved
visual performance and acuity3.
Studies have shown that the noise of individual neurons can be brought under experimental
control by appropriate choice of stimulus conditions, and contrast sensitivity at low levels can be
increased dramatically through control of stimulus parameters4-8. This precise control of stimulus
conditions leading to increased neuronal efficiency is fundamental in initiating the neural
modifications that are the basis for brain plasticity9,10. Brain plasticity (the ability to adapt to
changed conditions in acquiring new skills) has been demonstrated in many basic tasks, with
evidence pointing to physical modifications in the adult cortex during repetitive performance11-12.
NeuroVision’s technology probes specific neuronal interactions, using a set of patientspecific stimuli that improve neuronal efficiency6,13 and induce improvement of CSF due to
a reduction of noise and increase in signal strength. As visual perception quality depends
both on the input received through the eye and the processing in the visual cortex,
NeuroVision’s technology compensates for blurred (myopic) inputs, coming from the retina,
by enhancing neural processing.
------------------Technology Implementation ------------------The building block of these
visual stimulations is the
Gabor patch (Figure 1), which
efficiently
activates
and
matches
the
shape
of
receptive field in the Visual
Cortex.
The fundamental stimulation-control technique is called
“Lateral Masking”, where collinearly oriented flanking
Gabors are displayed in addition to the target Gabor image.
The patient is exposed to two short displays in succession,
in a random order; the patient identifies which display
contains the target Gabor image (Figure 2). The system
provides the patient with audio feedback when provided
with an incorrect response. The task is repeated and a
staircase is applied until the patient reaches their visual
threshold level.
First Display
Q u ic k T im e ™ a n d a
G r a p h ic s d e c o m p r e s s o r
a r e n e e d e d t o s e e t h is p ic t u r e .
Figure 2:
Lateral
Masking
images
Figure 1: The Gabor Patch
Second Display
•
Mean UAVA improvement was 2.1 lines (from 0.315 to 0.105) (Fig. 6)
•
Maximum UAVA improvement was 5 lines of logMAR (n=2)
-
Figure 4:
Effect of Lateral
Masking
-----------------NeuroVision Treatment System-----------------The NeuroVision Treatment System is a software-based, interactive system tailored and
continuously adaptive to the individual visual abilities. In the first stage, the subject is
exposed to a set of visual perception tasks, aimed to analyze and identify each subject’s
neural inefficiencies or deficiencies. Based on this analysis, a treatment plan is initialized,
and subject specificity is achieved by administering patient-specific stimuli in a controlled
environment.
3;
-------------------- Pilot Study Results Cont’d--------------------
-------------Technology Implementation Cont’d-----------------
34 eyes who had baseline of 20/25 or worse improved in average 2.3 lines from a mean of 0.36 (20/45) to 0.13(20/25)
26 eyes who had baseline of 20/30 or worse improved in average 2.6 lines from a mean of 0.42 (20/50) to 0.16 (20/25)
22 eyes who had baseline of 20/40 or worse improved in average 2.8 lines from a mean of 0.46 (20/60) to 0.18 (20/30)
•
Mean CSF improved at all spatial frequencies to within the normal range (Fig 8).
•
Vision improvement appears to be retained for at least 6 months (Fig. 9)
•
No side-effects were encountered during treatment
Figure 8:
Figure 6:
Mean
Improvement
in logMAR
lines
0.4
Normalisation of
Contrast Sensitivity
Function at
Treatment End
Q u ic k T im e ™ a n d a
G r a p h ic s d e c o m p r e s s o r
a r e n e e d e d t o s e e t h is p ic t u r e .
0.3
0.2
0.1
Each session is designed to train, directly and selectively, those functions in the visual
cortex, which were diagnosed to be further enhanced. At each session an algorithm
analyzes the patient's responses and accordingly adjusts the level of visual difficulty to the
range most effective for further improvement. Between sessions, the progress of the patient
is taken into account by the algorithm for the next session generation. Thus, for each subject
an individual training schedule is designed based on the initial state of visual performance,
severity of dysfunction and progress in course of treatment. The treatment is applied in
successive 30-minute sessions, administered 2-3 times a week, a total of approximately 30
sessions. Every 5 sessions, subject’s visual acuity is tested in order to continuously monitor
subject’s progress. The average entire treatment duration is around 3 months.
0
Figure 9:
0
2
4
6
8
10
Most
Current
Post-Treatment
Improved vision
retained at 6
months
Pre-Treatment
Figure 7:
Pre-Tx
UCVA change - EXIT Visit
Post-Tx
35
Change in
UAVA at
Treatment
End
Mean
Vision Improvement
Retention
10 Patients
10 Patients
that completed
6 of
Months
Examined 6 months Post Treatment
30
0.4
0.4
25
Percentage
1;
20
0.3
0.3
15
0.2
0.2
10
0.1
0.1
-----------Singapore Pilot Study on Low Myopia------------Twenty (20) adult patients with low myopia (mean cycloplegic spherical equivalent of –1.09D
(range –0.25 to –1.75)) were recruited in a prospective pilot study of NVC treatment.
Study subjects comprised 10 male and 10 female Asian volunteers with a mean age of 32
years (range 19 to 53 years). Patients underwent clinic-based (n=11) or home-based (n=9)
treatment sessions on an alternate day basis until no further improvement occurred (mean
treatment period = 3.2 months). Investigations included manifest and cycloplegic refraction,
LogMAR unaided acuity (UAVA), aided acuity (BCVA) and contrast sensitivity (CSF). All will
be followed up for 12 months after completion of treatment. Currently, all patients have
completed treatment and 10 patients have reached 6 months follow-up.
5
0.00
0
-0.1
• Improvement in UAVA of 1 logMAR line
or more occurred in 32 out of 40 eyes
(80%) at treatment end
• Improvement in UAVA of 2 logMAR lines
or more occurred in 21 out of 40 eyes
(53%) at treatment end
Figure 5:
Individual Eye
Improvement
at treatment end
1.0
0.8
0.6
0.4
0.2
0.1
0.2
0.3
0.4
0.5
0.6
0.7
UCVA (logMAR)
Treatment
1
Start
Treatment
End 2
3 Months Post
3
Treatment
Early results of this pilot study suggest that NVC treatment is able to improve visual
acuity and contrast sensitivity in adults with low myopia. This improvement appears
to be retained for at least 6 months after treatment. Patients will continue to be
followed up for another 6 months. A large-scale, placebo-controlled randomized
clinical trial is currently being planned.
-----------------References-----------------1.
Hubel, D. H. & Wiesel, T. N. Receptive fields, binocular interaction and functional architecture in the cat's visual cortex. J. Physiol. (Lond.) 160, 106-154 (1962).
2.
Polat, U. Functional architecture of long-range perceptual interactions. Spat Vis 12, 143-62 (1999).
3.
Geisler, W. S. & Albrecht, D. G. Visual cortex neurons in monkeys and cats: detection, discrimination, and identification. Vis Neurosci 14, 897-919 (1997).
4.
Kasamatsu, T., Polat, U., Pettet, M. W. & Norcia, A. M. Colinear facilitation promotes reliability of single-cell responses in cat striate cortex. Exp Brain Res 138, 163-72.
(2001).
5.
Polat, U., Mizobe, K., Pettet, M. W., Kasamatsu, T. & Norcia, A. M. Collinear stimuli regulate visual responses depending on cell's contrast threshold. Nature 391, 580-4
(1998).
6.
Polat, U. & Sagi, D. Spatial interactions in human vision: from near to far via experience- dependent cascades of connections. Proc Natl Acad Sci U S A 91, 1206-9
(1994).
7.
Polat, U. & Sagi, D. Lateral interactions between spatial channels: suppression and facilitation revealed by lateral masking experiments. Vision Res 33, 993-9 (1993).
8.
Polat, U. & Sagi, D. The architecture of perceptual spatial interactions. Vision Res 34, 73-8 (1994).
9.
Dosher, B. A. & Lu, Z. L. Perceptual learning reflects external noise filtering and internal noise reduction through channel reweighting. Proc Natl Acad Sci U S A 95,
13988-93. (1998).
10. Dosher, B. A. & Lu, Z. L. Mechanisms of perceptual learning. Vision Res 39, 3197-221. (1999).
0.0
11. Sagi, D. & Tanne, D. Perceptual learning: learning to see. Curr Opin Neurobiol 4, 195-9 (1994).
12. Gilbert, C. D. Adult Cortical Dynamics. Physiological Reviews 78, 467-485 (1998).
-0.2
6 Months Post
4
Treatment
-----------------Conclusions------------------
----------------------- Pilot Study Results---------------------Individual Vision Improvement
0
13. Polat, U. & Sagi, D. in Maturational Windows and Adult Cortical Plasticity (eds. Julesz, B. & Kovâcs, I.) 1-15 (Addison-Wesley, 1995).