RevitalVision Clinical Review
Vision is limited by two main factors: (a) the quality of the image that is transferred from the eye, and (b) the neural processing in the brain, which needs to integrate information between different neurons located at neighboring brain locations (space). Cortical cells (neurons) are highly specialized and optimized as image analyzers. Thus, to characterize an image, visual processing involves the cooperative activity of many neurons—those neuronal interactions contributing to both excitation and inhibition. The integration of image parts should be performed very quickly, since the time-window in which the first percept is formed is very short. Thus, visual information processing may be limited if the first percept representation is inefficient either due to slow neural processing or to the lack of effective interactions between the neurons.
1.1. Contrast sensitivity
Contrast sensitivity (CS), i.e., the ability to discriminate between shades of gray, is one of the main determinants of how well people see. It is assumed that the contrast sensitivity function (CSF) describes the combined response of the classical receptive fields of simple cells that have been selectively tuned for location, orientation, and spatial frequency and constitute the fundamental units of analysis. (Wilson, 1991; Wilson & Wilkinson, 1997). Thus, CSF describes the output of an early stage that provides the building blocks for the succeeding steps of visual processing.
During the last two decades, it was demonstrated that contrast response is also
determined by lateral interactions in the visual cortex of humans (Bonneh & Sagi, 1999;
Cass & Alais, 2006; Cass & Spehar, 2005; Ellenbogen, Polat, & Spitzer, 2006; Polat &
Norcia, 1996; Polat & Sagi, 1993, 1994a, 1994b, 2006; Shani & Sagi, 2006; Solomon &
Morgan, 2000; Tanaka & Sagi, 1998; Woods, Nugent, & Peli, 2002) and of animals (Crook, Engelmann, & Lowel, 2002; Kapadia, Ito, Gilbert, & Westheimer, 1995; Mizobe, Polat,) Visual acuity (VA) is the most common clinical measurement of visual function and is considered as the gold standard measure of visual functions. VA measures the ability to identify black symbols on a white background at a standardized distance as the size of the symbols is varied. A person with standard (normal) VA can recognize a letter that is specified as 6/6 (20/20).
1.2. Neural plasticity and perceptual learning
Visual plasticity is the ability of the visual system to change its responses in order to adapt to changes in the visual input. Evidence for plasticity in the adult visual system has been reported in human studies that have demonstrated that training in specific visual tasks leads to improvement in performance or sensitivity (for a review, see (Fahle & Poggio, 2002)). Perceptual learning has a major influence on our understanding of the development and plasticity of the visual system. Improvement after perceptual learning was demonstrated using a variety of visual tasks showing that the adult visual system can change according to behavioral demands (Fahle, 2005; Fiorentini & Berardi, 1980; Polat & Sagi, 1994b; Sagi & Tanne, 1994). (For a review, see Fahle (2002), Fahle and Poggio (2002), Gilbert, Sigman, and Crist (2001), Sagi and Tanne (1994).
1.3. Plasticity in amblyopia
Amblyopia is a reduction of visual functions that cannot be directly attributed to the effect of any structural abnormality of the eye or the posterior visual pathway. It is caused by abnormal binocular visual experience early in life, during the ‘critical period’ that prevents normal development of the visual system. A generally practiced principle of treatment is that therapy can only be effective during the critical period, usually considered to end around the age of 8–9 (Greenwald & Parks, 1999; Prieto-Diaz, 2000; von Noorden, 1981), when the visual system is considered sufficiently plastic for cortical modifications to occur. The standard amblyopia therapy is thus traditionally directed toward children and consists of penalizing the preferred eye by using an eye patch or atropine, thus forcing the brain to use the visual input from the amblyopic eye. However, in adults, the visual deficiencies are thought to be irreparable after the first decade of life, once the developmental maturation window has been terminated; thus the standard treatment is usually not offered. However, recovery of visual functions in adults with amblyopia after occlusion therapy (Birnbaum, Koslowe, & Sanet, 1977; Simmers, Gray, McGraw, & Winn, 1999; Wick, Wingard, Cotter, & Scheiman, 1992) or after loss of vision in the good eye (El Mallah, Chakravarthy, & Hart, 2000) was reported. The first step in a series of controlled studies that provided evidence for plasticity, after perceptual learning, in adults with amblyopia used training for the vernier acuity task (Levi & Polat, 1996; Levi, Polat, & Hu, 1997b). Repetitive practice led to a substantial improvement in vernier acuity in the amblyopic eyes of adults with amblyopia. In two observers, the improvement in vernier acuity was accompanied by a commensurate improvement in VA reaching up to normal vision. These studies provided an optimistic possibility for future treatment of amblyopia based on perceptual learning. Recent studies have provided additional evidence for plasticity in adults with amblyopia (Chung, Li, & Levi, 2006; Fronius, Cirina, Cordey, & Ohrloff, 2005; Fronius, Cirina, Kuhli, Cordey, & Ohrloff, 2006; Levi, 2005; Li & Levi, 2004; Polat et al., 2004; Zhou et al., 2006).
1.4. Improving normal visual functions
Some insight into the mechanism underlying neural plasticity, which may improve the contrast sensitivity, comes from lateral masking experiments (Polat & Sagi, 1994b, 1995; Polat et al., U. Polat / Vision Research 49 (2009) 2566–2573 2567 2004). These studies suggest that practice on lateral interactions increases the efficacy of the collinear interactions between neighboring neurons, an effect that enables connectivity with remote neurons via a cascade of local interactions. Thus, the results suggest a possible tool for the use of lateral interactions for improving CS in people with normal vision and in people with impaired lateral interactions such as amblyopia. Polat has developed a perceptual learning procedure that was designed to improve the abnormal lateral interactions in amblyopia by stimulating the deficient neuronal populations and effectively promoting their collinear interactions (Polat, 2006, 2008; Polat et al., 2004). Since the amblyopic deficit is not identical among subjects (Bonneh, Sagi, & Polat, 2004; Bonneh et al., 2007; Polat, 2008; Polat et al., 2005), the treatment was tailored and specifically designed for each individual’s deficiencies.
1.5. Improvement of lateral interactions in amblyopia
Amblyopes exhibit abnormal lateral interactions (Bonneh et al., 2004, 2007; Ellemberg et al., 2002; Levi et al., 2002; Polat, 2006, 2008; Polat et al., 2004). The lateral interaction function of the amblyopes at the beginning of the treatment showed no facilitation and in fact, increased the amount of suppression. However, after the treatment, the amount of suppression was significantly reduced to a normal level (Polat, 2008; Polat et al., 2004).
1.6. Improvement of CSF in amblyopia
In the study of Polat et al. (2004), the amblyopic eyes exhibit the typical lower CS before treatment, as compared with normal sighted eyes, with the low spatial frequencies near the normal values and the high spatial frequencies showing a worse deficit. The treatment produced a significant improvement in sensitivity, by about a factor of two, in all spatial frequencies including the high spatial frequency range, raising the function to within the normal (lower) range. Most interesting is the result that after 12 months, CSF was not only retained, but it also increased toward an average range at the high spatial frequencies. This result suggests that the high spatial frequencies are used after the treatment in daily tasks and thus are naturally practiced.
1.7. Improvement of CSF in non-amblyopic groups
The procedure of Polat et al. (2004), when applied to people with normal vision or corrected to normal vision, improved their visual acuity to better than 66. It has been recently applied to improve the vision of people with low myopia (Tan & Fong, 2008). The vision of myopic (short sighted) subjects is blurred without optical correction. Therefore, the CSF is reduced, especially at the higher spatial frequencies, when compared with people with corrected vision. This reduction in CS is reminiscent of the CS of amblyopic subjects. This study used a protocol similar to the one used for the amblyopia (Polat et al., 2004); it showed that when subjects practiced with uncorrected moderate myopia it improved their CS. Thus, even in cases when the lateral interactions are normal (low myopia), training improves CS.
1.8. Improvement of VA
The VA was found to improve after training on contrast detection of amblyopes (Polat et al., 2004), anisometropic amblyopes (Huang et al., 2008; Zhou et al., 2006), and after training on verneir acuity (Levi & Polat, 1996; Levi, Polat, & Hu, 1997a). The training of low myopia on lateral interactions also shows improvement of VA (Tan & Fong, 2008). Thus, the training can be generalized to the letter recognition task (VA), an effect that supports the relationships between these perceptual tasks and letter recognition.
1.9. Transfer to improvement of binocular vision
In the studies of Polat and colleagues, during the treatment, the fellow eye was covered; thus the treatment was monocular, targeting the abnormal lateral interactions of the amblyopic eye. Very surprisingly, after treatment, the binocular functions improved, indicating that both the binocular fusion and the stereo acuity improved (Polat, 2006, 2008). A significant improvement in stereoacuity was also found in a retrospective study (Lichter, 2007).
1.10. Additional indications for function improvement.
In addition to Amblyopia and Myopia, several other conditions that cause reduced VA
were studied. Presbyopic patients showed an increase of 1.5 to 2 lines and an increase of close to 100% in CS following treatment (Polat 2009; Tan 2005; Stahl & Durrie 2008; Durrie & McMinn, 2007). Patients who have undergone refractive surgery have shown similar results (Tan 2005, Waring IV et al., unpublished data). Patients who have undergone intra-ocular-lens (IOL) implant surgery following cataract extraction showed high CS improvement and an increase of 1 to 1.5 lines of VA in a variety of monofocal and multifocal or accommodating IOLs (Waring IV et al. 2010). A possible positive treatment outcome in myopia control is suggested by seminal work done on school children (Chua et al. 2007), and although this is yet to be determined by a randomized double blind controlled study, over several years, the current findings suggest optimistic outcomes.
Due to the promising findings in the above studies and in light of the fact that the treatment is safe and non-invasive, several practitioners have used this treatment in managing several types of ocular pathologies. Among others these include: congenital nystagmus (CN) (Morad 2012), age related macular degeneration, retinitis pigmentosa (Lyra, 2009) pathological myopia and congenital stationary night blindness. A retrospective multicenter study which is being carried out during this year has already showing positive results in cases of CN.
1.11. Persistence of the improved functions
Different studies measured the persistence of the results over a retention period. While amblyopia showed a surprising increase in CS function over time (Polat et al 2004), others showed a mild regression of about 15% of the treatment effect over the first six months post treatment. However, in the following eighteen months of retention no further regression was noted (Siow & Tan, 2008). Studies aimed at presbyopia and post refractive correction procedures have shown no regression over twelve months retention (Tan et al. 2005, Ng et al. 2007)
Albrecht, D. G. (1995). Visual cortex neurons in monkey and cat: Effect of contrast on
the spatial and temporal phase transfer functions. Visual Neuroscience, 12(6), 1191– 1210.
Birnbaum, M. H., Koslowe, K., & Sanet, R. (1977). Success in amblyopia therapy as a
function of age: A literature survey. American Journal of Optometry and Physiological
Optics, 54(5), 269–275.
Bonneh, Y., & Sagi, D. (1999). Configuration saliency revealed in short duration
binocular rivalry. Vision Research, 39(2), 271–281.
Bonneh, Y. S., Sagi, D., & Polat, U. (2004). Local and non-local deficits in amblyopia:
Acuity and spatial interactions. Vision Research, 44(27), 3099–3110.
Bonneh, Y. S., Sagi, D., & Polat, U. (2007). Spatial and temporal crowding in amblyopia.
Vision Research, 47(14), 1950–1962.
Breitmeyer, B. G. (1984). Visual masking: an integrative approach. Oxford Psychology
series (vol. 4). New York: Oxford University Press.
Breitmeyer, B. G., & Ogmen, H. (2000). Recent models and findings in visual backward
masking: A comparison, review, and update. Perception and Psychophysics, 62(8), 1572– 1595.
Carrasco, M., Penpeci-Talgar, C., & Eckstein, M. (2000). Spatial covert attention
increases contrast sensitivity across the CSF: Support for signal enhancement. Vision Research, 40(10–12), 1203–1215.
Carrasco, M., Williams, P. E., & Yeshurun, Y. (2002). Covert attention increases spatial
resolution with or without masks: Support for signal enhancement. Journal of Vision, 2(6), 467–479.
Cass, J., & Alais, D. (2006). The mechanisms of collinear integration. Journal of Vision,
Cass, J. R., & Spehar, B. (2005). Dynamics of collinear contrast facilitation are consistent
with long-range horizontal striate transmission. Vision Research, 45(21), 2728–2739.
Chandna, A., Pennefather, P. M., Kovacs, I., & Norcia, A. M. (2001). Contour integration
deficits in anisometropic amblyopia. Investigative Ophthalmology & Visual Science,
Chua WH Tan D Fong A (2007) Enhancement of Under Corrected Visual Acuity and
Contrast Sensitivity in Myopic Children Using NeuroVision’s Neural Vision Correction
(NVC) Technology ARVO 2007
Chung, S. T., Legge, G. E., & Tjan, B. S. (2002). Spatial-frequency characteristics of
letter identification in central and peripheral vision. Vision Research, 42(18), 2137–2152.
Chung, S. T., Levi, D. M., & Legge, G. E. (2001). Spatial-frequency and contrast
properties of crowding. Vision Research, 41(14), 1833–1850.
Chung, S. T., Li, R. W., & Levi, D. M. (2006). Identification of contrast-defined letters
benefits from perceptual learning in adults with amblyopia. Vision Research, 46(22), 3853–3861.
Chung, S. T., Mansfield, J. S., & Legge, G. E. (1998). Psychophysics of reading. XVIII.
The effect of print size on reading speed in normal peripheral vision. Vision
Research, 38(19), 2949–2962.
Crook, J. M., Engelmann, R., & Lowel, S. (2002). GABA-inactivation attenuates colinear
facilitation in cat primary visual cortex. Experimental Brain Research, 143(3), 295–302.
Durrie D, McMinn PS. (2007) Computer-based primary visual cortex training for
treatment of low myopia and early presbyopia. Trans Am Ophthalmol Soc. 2007;105:132-8; discussion 138-40.
El Mallah, M. K., Chakravarthy, U., & Hart, P. M. (2000). Amblyopia: Is visual loss
permanent? British Journal of Ophthalmology, 84(9), 952–956.
Ellemberg, D., Hess, R. F., & Arsenault, A. S. (2002). Lateral interactions in amblyopia.
Vision Research, 42(21), 2471–2478.
Ellenbogen, T., Polat, U., & Spitzer, H. (2006). Chromatic collinear facilitation, further
evidence for chromatic form perception. Spatial Vision, 19(6), 547–568.
Fahle, M. (2002). Perceptual learning: Gain without pain? Nature Neuroscience, 5(10),
Fahle, M. (2005). Perceptual learning: Specificity versus generalization. Current Opinion
in Neurobiology, 15(2), 154–160.
Fahle, M., & Poggio, T. (2002). Perceptual learning. Cambridge, MA: MIT Press.
Fahle, M., & Skrandies, W. (1994). An electrophysiological correlate of learning in
motion perception. German Journal of Ophthalmology, 3(6), 427–432.
Fiorentini, A., & Berardi, N. (1980). Perceptual learning specific for orientation and spatial frequency. Nature, 287(5777), 43–44.
Flom, M. C., Weymouth, F. W., & Kahneman, D. (1963). Visual resolution and contour
interaction. Journal of the Optical Society of America, 53(9), 1026–1032.
Fronius, M., Cirina, L., Cordey, A., & Ohrloff, C. (2005). Visual improvement during
psychophysical training in an adult amblyopic eye following visual loss in the
contralateral eye. Graefe’s Archive for Clinical and Experimental Ophthalmology,
Fronius, M., Cirina, L., Kuhli, C., Cordey, A., & Ohrloff, C. (2006). Training the adult
amblyopic eye with ‘‘perceptual learning” after vision loss in the non-amblyopic eye.
Strabismus, 14(2), 75–79.
Gilbert, C. D., Sigman, M., & Crist, R. E. (2001). The neural basis of perceptual learning.
Neuron, 31(5), 681–697.
Greenwald, M. J., & Parks, M. M. (1999). Treatment of amblyopia. In T. Duane (Ed.).
Clinical ophthalmology (Vol. 1). Hagerstown: Harper and Row.
Hariharan, S., Levi, D. M., & Kelin, S. A. (2005). ‘‘Crowding” in normal and amblyopic
vision assessed with Gaussian and Gabor C’s. Vision Research, 45(5), 617–633.
Harwerth, R. S., & Levi, D. M. (1978). Reaction time as a measure of suprathreshold grating detection. Vision Research, 18(11), 1579–1586.
Hess, R. F., McIlhagga, W., & Field, D. J. (1997). Contour integration in strabismic
amblyopia: The sufficiency of an explanation based on positional uncertainty. Vision Research, 37(22), 3145–3161.
Hirsch, J. A., & Gilbert, C. D. (1991). Synaptic physiology of horizontal connections in
the cat’s visual cortex. Journal of Neuroscience, 11(6), 1800–1809.
Huang, C. B., Zhou, Y., & Lu, Z. L. (2008). Broad bandwidth of perceptual learning in
the visual system of adults with anisometropic amblyopia. Proceedings of the National Academy of Sciences USA, 105(10), 4068–4073.
Kapadia, M. K., Ito, M., Gilbert, C. D., & Westheimer, G. (1995). Improvement in visual
sensitivity by changes in local context: Parallel studies in human observers and in V1 of alert monkeys. Neuron, 15(4), 843–856. 2572 U. Polat / Vision Research 49 (2009) 2566–2573 Kovacs, I., Polat, U., Pennefather,
P. M., Chandna, A., & Norcia, A. M. (2000). A new test of contour integration deficits in
patients with a history of disrupted binocular experience during visual development. Vision Research, 40(13), 1775–1783.
Legge, G. E., Mansfield, J. S., & Chung, S. T. (2001). Psychophysics of reading.XX.
Linking letter recognition to reading speed in central and peripheral vision. Vision Research, 41(6), 725–743.
Legge, G. E., Pelli, D. G., Rubin, G. S., & Schleske, M. M. (1985). Psychophysics of
reading – I. Normal vision. Vision Research, 25(2), 239–252.
Levi, D. M. (2005). Perceptual learning in adults with amblyopia: A reevaluation of critical periods in human vision. Developmental Psychobiology, 46(3), 222–232.
Levi, D. M., Hariharan, S., & Klein, S. A. (2002). Suppressive and facilitatory spatial interactions in amblyopic vision. Vision Research, 42(11), 1379–1394.
Levi, D. M., & Li, R. W. (2009). Perceptual learning as potential treatment for
amblyopia: A mini-review. Vision Research., 49(21), 2535–2549.
Levi, D. M., & Polat, U. (1996). Neural plasticity in adults with amblyopia. Proceedings
of the National Academy of Sciences USA, 93(13), 6830–6834.
Levi, D. M., Polat, U., & Hu, Y. S. (1997a). Improvement in vernier acuity in adults with
amblyopia. Investigative Ophthalmology & Visual Science, 38(8), 1493–1510.
Levi, D. M., Polat, U., & Hu, Y. S. (1997b). Improvement in Vernier acuity in adults with amblyopia. Practice makes better. Investigative Ophthalmology & Visual Science, 38(8), 1493–1510.
Levi, D. M., Song, S., & Pelli, D. G. (2007). Amblyopic reading is crowded. Journal of
Vision, 7(2), 21. 21–17.
Levitt, H. (1971). Transformed up-down methods in psychoacoustics. Journal of the Acoustical Society of America, 49(Suppl. 2), 467+.
Li, R. W., & Levi, D. M. (2004). Characterizing the mechanisms of improvement for position discrimination in adult amblyopia. Journal of Vision, 4(6), 476–487.
Liu, L., Wang, K., Liao, B., Xu, L., & Han, S. (2004). Perceptual salience of global
structures and the crowding effect in amblyopia. Graefe’s Archive Clinical Experimental Ophthalmology, 242(7), 566–570.
Livne, T., & Sagi, D., (2007) Configuration influence on crowding. Journal of Vision, 7(2): 4, 1–12.
LyraJ.M. (2009), Neuroplasticity, key to vision recovery. AAO 2008. ESCRS 2009
Majaj, N. J., Pelli, D. G., Kurshan, P., & Palomares, M. (2002). The role of spatial
frequency channels in letter identification. Vision Research, 42(9), 1165–1184.
Mizobe, K., Polat, U., Pettet, M. W., & Kasamatsu, T. (2001). Facilitation and
suppression of single striate-cell activity by spatially discrete pattern stimuli presented beyond the receptive field. Visual Neuroscience, 18(3), 377–391.
Nazarul M, Fong A., Tan D., A Randomised Controlled Trial Evaluating the Efficacy of
Neurovision's Neural Vision Correction Technology in Enhancing Unaided Visual Acuity
in Adults with Low Myopia ARVO 2008
O’Regan, J. K. (1990). Eye movements and reading. Reviews of Oculomotor Research,
Parkes, L., Lund, J., Angelucci, A., Solomon, J. A., & Morgan, M. (2001). Compulsory
averaging of crowded orientation signals in human vision. Nature Neuroscience, 4(7), 739–744.
Patching, G. R., & Jordan, T. R. (2005). Spatial frequency sensitivity differences between
adults of good and poor reading ability. Investigative Ophthalmology & Visual Science,
Pelli, D. G., Palomares, M., & Majaj, N. J. (2004). Crowding is unlike ordinary masking:
Distinguishing feature integration from detection. Journal of Vision, 4(12), 1136–1169.
Peli, E., Arend, L. E., Young, G. M., & Goldstein, R. B. (1993). Contrast sensitivity to
patch stimuli: Effects of spatial bandwidth and temporal presentation. Spatial Vision, 7(1), 1–14.
Petrov, Y., & McKee, S. P. (2006). The effect of spatial configuration on surround
suppression of contrast sensitivity. Journal of Vision, 6(3), 224–238.
Plainis, S., & Murray, I. J. (2005). Magnocellular channel subserves the human contrastsensitivity function. Perception, 34(8), 933–940.
Polat, U. (1999). Functional architecture of long-range perceptual interactions. Spatial Vision, 12(2), 143–162.
Polat, U. (2006). Improving abnormal spatial vision in adults with amblyopia. In M. R.
M. Jenkin & L. R. Harris (Eds.), Seeing spatial form (pp. 371–380). New York: Oxford
Polat, U. (2008). Restoration of underdeveloped cortical functions: Evidence from
treatment of adult amblyopia. Restorative Neurology and Neuroscience, 26, 1–12.
Polat, U., Bonneh, Y., Ma-Naim, T., Belkin, M., & Sagi, D. (2005). Spatial interactions
in amblyopia: Effects of stimulus parameters and amblyopia type. Vision Research, 45(11), 1471–1479.
Polat, U., Ma-Naim, T., Belkin, M., & Sagi, D. (2004). Improving vision in adult
amblyopia by perceptual learning. Proceedings of the National Academy of Sciences USA, 101(17), 6692–6697.
Polat, U., Mizobe, K., Pettet, M. W., Kasamatsu, T., & Norcia, A. M. (1998). Collinear
stimuli regulate visual responses depending on cell’s contrast threshold. Nature,
Polat, U., & Norcia, A. M. (1996). Neurophysiological evidence for contrast dependent
long-range facilitation and suppression in the human visual cortex. Vision Research, 36(14), 2099–2109.
Polat, U., & Sagi, D. (1993). Lateral interactions between spatial channels: Suppression
and facilitation revealed by lateral masking experiments. Vision Research, 33(7), 993– 999.
Polat, U., & Sagi, D. (1994a). The architecture of perceptual spatial interactions. Vision
Research, 34(1), 73–78.
Polat, U., & Sagi, D. (1994b). Spatial interactions in human vision: From near to far via
experience-dependent cascades of connections. Proceedings of the National Academy of Sciences USA, 91(4), 1206–1209.
Polat, U., & Sagi, D. (1995). Plasticity of spatial interactions in early vision. In B. Julesz
& I. Kovacs (Eds.). Maturational windows and adult cortical plasticity (Vol.
24, pp. 1–15). Addison-Wesley.
Polat, U., & Sagi, D. (2006). Temporal asymmetry of collinear lateral interactions.
Vision Research, 46(6–7), 953–960.
Polat, U., Sagi, D., & Norcia, A. M. (1997). Abnormal long-range spatial interactions in
amblyopia. Vision Research, 37(6), 737–744.
Polat, U., Sterkin, A., & Yehezkel, O. (2007). Spatio-temporal low-level neural networks
account for visual masking. Advances in Cognitive Psychology(3), 153–165.
Popple, A. V., & Levi, D. M. (2000). Amblyopes see true alignment where normal
observers see illusory tilt. Proceedings of the National Academy of Sciences USA,
Prieto-Diaz, J. S.-D. C. (2000). Strabismus. Boston: Butterworth–Heinemann.
Sagi, D., & Tanne, D. (1994). Perceptual learning: Learning to see. Current pinion in Neurobiology, 4(2), 195–199.
Shani, R., & Sagi, D. (2006). Psychometric curves of lateral facilitation. Spatial Vision,
Simmers, A. J., Gray, L. S., McGraw, P. V., & Winn, B. (1999). Functional visual loss in
amblyopia and the effect of occlusion therapy. Investigative Ophthalmology & Visual Science, 40(12), 2859–2871.
Simmers, A. J., Ledgeway, T., Hess, R. F., & McGraw, P. V. (2003). Deficits to global
motion processing in human amblyopia. Vision Research, 43(6), 729–738.
Siow K, Tan D, (2008) 2 Years Follow-Up Results of Visual Acuity and Contrast
Sensitivity Enhancement in Patients with Low Myopia using NeuroVision’s Neural
Vision Correction (NVC) Technology IMC 2008
Solomon, J. A., & Morgan, M. J. (2000). Facilitation from collinear flanks is cancelled by
non-collinear flanks. Vision Research, 40(3), 279–286.
Stuart, J. A., & Burian, H. M. (1962). A study of separation difficulty and its relationship
to visual acuity in normal and amblyopic eyes. American Journal of Ophthalmology, 53, 471–477.
Tan D. T. (2006), Improving VA and CSF in Subjects with Low Degrees of Myopia and
Early Presbyopia using Neural Vision Correction (NVC) Technology, APAO 2006
Tan D.T., Chan B., Tey F., Lee L (2004), Pilot Study To Evaluate The Efficacy of Neural
Vision Correction™ (NVC™) Technology For Vision Improvement in Low Myopia,
Tan, D. T., & Fong, A. (2008). Efficacy of neural vision therapy to enhance contrast sensitivity function and visual acuity in low myopia. Journal of Cataract and Refractive Surgery, 34(4), 570–577.
Tanaka, Y., & Sagi, D. (1998). Long-lasting, long-range detection facilitation. Vision
Research, 38(17), 2591–2599.
Tripathy, S. P., & Cavanagh, P. (2002). The extent of crowding in peripheral vision does
not scale with target size. Vision Research, 42(20), 2357–2369.
Von Noorden, G. K. (1981). New clinical aspects of stimulus deprivation amblyopia. American Journal of Ophthalmology, 92(3), 416–421.
Watson, A. B., Barlow, H. B., & Robson, J. G. (1983). What does the eye see best? Nature, 302(5907), 419–422.
Waring IV G.O., Durrie D.S., Slade G.S. Visual Cortex Training Combined With LASIK
for Treatment of Low Myopia, unpublished Data
Waring IV G.O., Hunkeler J., Lindstrom R., (2010) Evaluation of Computer Based
Primary Visual Cortex Training After Aspheric Monofocal, Multifocal, and
Accommodating IOL Implantation ARVO 2010
Wick, B., Wingard, M., Cotter, S., & Scheiman, M. (1992). Anisometropic amblyopia: Is
the patient ever too old to treat? Optometry and Vision Science, 69(11), 866–878.
Wilson, H. R. (1991). Psychophysical models of spatial vision and hyperacuity. In D.
Regan (Ed.). Vision and Visual Dysfunction (Vol. 10, pp. 64–86). CRC Press, Inc..
Wilson, H. R., & Wilkinson, F. (1997). Evolving concepts of spatial channels in vision:
From independence to nonlinear interactions. Perception, 26(8), 939–960.
Wong, E. H., & Levi, D. M. (2005). Second-order spatial summation in amblyopia.
Vision Research, 45(21), 2799–2809.
Wong, E. H., Levi, D. M., & McGraw, P. V. (2005). Spatial interactions reveal inhibitory
cortical networks in human amblyopia. Vision Research, 45(21), 2810–2819.
Woods, R. L., Nugent, A. K., & Peli, E. (2002). Lateral interactions: Size does matter.
Vision Research, 42(6), 733–745.
Yu, C., Klein, S. A., & Levi, D. M. (2004). Perceptual learning in contrast discrimination
and the (minimal) role of context. Journal of Vision, 4(3), 169–182.
Zhou, Y., Huang, C., Xu, P., Tao, L., Qiu, Z., Li, X., et al. (2006). Perceptual learning
improves contrast sensitivity and visual acuity in adults with anisometropic amblyopia.
Vision Research, 46(5), 739–750.
U. Polat / Vision Research 49 (2009) 2566–2573 2573