Neuro-Enhancement: A New Treatment for Optic Neuropathy
(Reprinted from Visibility, Vol. 6 Iss. 3 pp. 15-18)
Neuro-enhancement is produced by the use of custom prismatic spectacles, designed and prescribed by looking at visual evoked potentials (VEPs). Improved functional vision results from a decreased latency in signals traveling through the brain and not from simply finding the locus of maximum retinal sensitivity. In a study of 100 patients, the new treatment significantly improved the sight of people with a range of optic neuropathies, including primary and hereditary optic atrophy, stroke, tumor, glaucoma, head injury, optic neuropathy with and without MS, optic nerve hypoplasia, and ischemic optic neuropathy.
It is commonly believed by professionals and lay people that if you damage a sensory neuron to the point that it atrophies, the resulting loss of conduction and function are irreversible. This belief stems from the conceptual model that a sensory neuron behaves like a single strand of copper wire, and that the sensory organ behaves like a telegraph keypad, with the brain having a receiver to decode the message. A break in the wire prevents the interpretation of the message. But what if sensory neurons behave like fiber optic bundles? They would be able to transmit much more information than the copper strand and they would be tunable. The ability to tune would mean that changing the angle of the beam of light would allow many signals to travel through the fiber optic bundle at the same time. Damage to some of the fibers in the bundle would not degrade the signal.
The purpose of this study is to demonstrate that the transmission and function of the human visual system with optic atrophy can be improved by changing the angle of the light entering the eye.
Walter Stanley Stiles and Brian Hewson Crawford first described the directional sensitivity of cone receptors in the human eye in 1933.1 They were looking at a retinal explanation for the phenomenon they observed: light entering the center of the pupil appears brighter than light entering from the periphery of the pupil. The knowledge of neural processing occurring throughout the entire visual system would not occur until much later.
David Hunter Hubel and Torsten Nils Wiesel greatly expanded our knowledge of sensory processing in their historic experiments of 1959.2 Their work established the foundation for neurophysiology. Orientation-sensitive fields were described in their study. They demonstrated that vision is a brain function and not an eye function.
Their work relied on electrodes inserted into the striate visual cortex. Our study relies on visually evoked potential (VEP), which uses electrodes applied to the scalp with electrode paste.3 The VEP measures the strength of the signals (amplitude), as well as the time spent traveling through the eye and the brain (latency). The VEP uses a computer to select signals from the brain (EEG) and separate the signals that are produced by the entire visual system (VEP).
Sam Sokol, in 1976, suggested using the VEP to measure the sight of newborns, and also to measure contrast sensitivity and color vision.4 Our study demonstrates a new and unique use for the VEP, not just to establish the presence of sight, but also, with the use of our assessment technique and measurements, to actually improve sight and overall visual function. The improvement in sight is not the result of a change in retinal function, but rather from a change in brain function, which is activated by decreasing the time it takes for signals to arrive at the primary visual cortex.
This study looked at 100 patients, 196 eyes, with optic nerve disease. Four patients had one eye enucleated; 46 patients were female and 54 were male. Their ages ranged from 5 years old to 97 years old, with a mean age of 60.7 years old.* See Figure 1.
Distance vision was tested on each patient with The Original Distance Chart for the Partially Sighted, arranged by William Feinbloom, OD, PhD. Near acuity was measured with The Lighthouse Near Acuity Test (Second Edition) Modified ETDRS with
Sloan letters. Snellen distance and near acuities were converted to a decimal form to facilitate statistical analysis.
Visual acuity varied from 20/20 to no light perception (NLP). Two people had one eye with 20/20. Two people had one eye with NLP. Two people had light perception (LP) in one eye. One person had LP in both eyes. Two people had one eye with hand motion (HM). For the purposes of statistical analysis, NLP, LP and HM were recorded as 0.00. Visual acuity of 20/20 was recorded as 1.00. More conventional forms of presenting acuities, e.g., log transforms, could not be used because of the inclusions of patients with acuities of 0.
The Visual Evoked Potential (VEP) was performed on each patient. Gold cup electrodes (Grass Model F-E56 H Astro-Med Inc., West Warwick, R.I.) were applied to the scalp with EEG paste. The electrodes were placed 4 cm above the inion on the midline and 4 cm above the brow on midline. The ground electrode was placed midway between the other electrodes. The impedance of the electrodes, measured prior to testing, was performed in compliance with the 2009 ISCEV Standard.
A Diopsys Enfant™ System (Diopsys Inc., Pine Brook, New Jersey, USA) was used with a checkerboard reversal pattern at 85% contrast viewed at one meter. First the check size with the biggest amplitude was selected. See Figure 2.
Contrast was set to Michelson 85%. Mean luminance was 66.25 cd/m2.The checkerboard reversed at 2/seconds.
Testing was performed monocularly with best correction. The amount of prism chosen was determined by the patient’s visual
acuity, as follows: See Figure 3.
Each patient received keratometry with a Haag Streit ophthalmometer and a trial frame refraction. The ensuing best spectacle correction in the trial frame was used for the VEP testing. The four checkerboard sizes were analyzed to determine what size produced the largest amplitude. The selected prism was put in the trial frame and the VEP was performed with the prism base up, base patient’s left, base down, and base patient’s right (clockwise). After the VEP data was collected, the landmarks were marked on the wave form.
The N50, N75 and P100 were identified. The orientation of the prism that produced the largest amplitude with the shortest latency was selected. If two orientations resulted in the largest amplitude, the prescribed orientation was placed between both original orientations. If three orientations resulted in large amplitudes, the orientation was 180 degrees away from the center of the three orientations. If there was no increase in the amplitude and no decrease in latency, no prism was prescribed.
Paired-samples t-tests were conducted on the mean score for VA DIST, VA NEAR, AMP and LAT, comparing each variable between the prism and without prism conditions.
There was a significant difference in the VA DIST scores for the without prism (M = 0.16, SD = 0.19) and with prism (M=0.35, SD = 0.29) conditions, t (194) = -11.95, p<.001, 95% confidence interval for the difference (-0.22, -0.15).
There was a significant difference in the VA NEAR scores for the without prism (M = 0.21, SD = 0.23) and with prism (M=0.49, SD = 0.32) conditions, t (194) = -15.05, p<.001, 95% confidence interval for the difference (-0.32, -0.25).
There was a significant difference in the AMP scores for the without prism (M = 5.08, SD = 2.94) and with prism (M=4.23, SD = 3.58) conditions, t (191) = 2.66, p=.008, 95% confidence interval for the difference (0.22, 1.47).
There was a significant difference in the LAT scores for the without prism (M = 106.41, SD = 17.70) and with prism (M=96.07, SD = 28.44) conditions, t (194) = 5.37, p<.001, 95% confidence interval for the difference (6.54, 14.14). See Table 1.
The mean distance vision without prism was 20/125 and 20/57 with prism. The mean near vision was 20/95 without prism and 20/41 with prism.
Distance vision improved 2.19 times and near vision improved 2.33 times. Of the seven people with profound visual loss, two eyes with no light perception did not improve, three of four eyes with light perception improved (two improved to hand motion and one to 5/300), two of two hand motion eyes improved to 5/400 and 1/600.
DISCUSSION AND SUMMARY
Initially, it was expected that using a prism in various directions would objectively map the locus of greatest retinal sensitivity by moving the image off a scotoma produced by optic nerve disease. We had previously described the use of prisms, called RIT therapy, when there was retinal disease, so we were looking for similar results. We expected to see an increase in the amplitude of the VEP.
A decrease in latency was a better predictor of improved vision than an increase in amplitude. One might assume that the latency
would decrease because of an improvement in visual acuity. An improvement in acuity should result in an increase in amplitude and a decrease in latency. This is not what we found. Latency did decrease, as predicted, but amplitude also decreased. This finding suggests that the improvement in vision resulted from a change in the brain and not in the retina. Additional studies are currently underway that are looking at the importance of coding visual information temporally.
The use of neuro-enhancement with prismatic spectacles measured by VEP in patients with optic nerve disease is an important adjunct therapy to be used in combination with traditional medical and surgical management. The improvement in sight results in clearer distance and near functional vision.
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