Autosomal Dominant Retinitis Pigmentosa Secondary to TOPORS Mutations: A Report of a Novel Mutation and Clinical Findings

Purpose: Mutations in Topoisomerase I-binding RS protein (TOPORS) have been previously documented and have been described to result in pathological autosomal dominant retinitis pigmentosa (adRP). In our study, we describe the various genotypes and clinical/phenotypic manifestations of TOPORS-related mutations of our unique patient population in Rural Appalachia. Methods: The medical records of 416 patients with inherited retinal disease at the West Virginia University Eye Institute who had undergone genetic testing between the years of 2015-2022 were reviewed. Patients found to have pathologic RP and mutations related to TOPORS were then analyzed. Results: In total, 7 patients (ages 12-70) were identified amongst three unique families. All patients were female in our study. The average follow-up period was 7.7 years. A mother (70 yr) and daughter (51 yr) had a novel heterozygous nonsense point mutation in TOPORS c.2431C > T, p.Gln811X (Exon 3) that led to premature termination of the desired protein resulting in early onset vision loss, cataract formation, and visual field restriction. The mother developed a full-thickness macular hole which was successfully repaired. Five other patients were found to have previously described TOPORS mutations. Visual field loss was progressive with age in both cohorts. Conclusions: Seven patients at our institution were identified to have mutations in TOPORS resulting in autosomal dominant retinitis pigmentosa. Two patients were found to have novel truncating mutations in the TOPORS gene resulting in profound night blindness and visual field loss, recurrent macular edema, and in one individual, epiretinal membrane formation leading to a macular hole which was able to be successfully repaired.

Case Series on Autosomal Recessive Non-Syndromic Retinitis Pigmentosa Caused by POMGNT1 Mutations with a Report of a New Variant

Recessive Protein O-linked-mannose beta-1,2-N-acetylglucosaminyltransferase 1 (POMGNT1) mutations can cause early onset muscle-eye-brain disease but have also more recently been associated with non-syndromic Retinitis Pigmentosa. In this case series, we describe three sisters affected by non-syndromic autosomal recessive POMGNT1 retinopathy with a report of a new variant. The three patients received care at West Virginia University Eye Institute, including full ophthalmic examination with additional fundus imaging, optical coherence tomography (OCT), electroretinogram (ERG), and visual field testing. Diagnostic panel testing of 330 genes was also obtained. The proband was seen for cataract evaluation at age 42, and her fundus examination was suggestive of retinitis pigmentosa. Her oldest sister had been treated for acute anterior uveitis with retinal vasculitis. Another sister was diagnosed with multiple sclerosis (MS) and peripheral retinal degeneration. Posterior subcapsular cataracts were diagnosed between age 42 and 55 in all three sisters, each with constricted fields with preserved central vision. We identified one pathogenic POMGNT1 variant (c.751 + 1G > A) and one likely pathogenic variant (c.1010T > C p.Ile337Thr) in all three sisters. A thorough family history and examination of the siblings with genotyping might have led to an earlier diagnosis of retinal inherited disease and avoidance of immunomodulatory treatment in the oldest sibling.

Visual evoked potential importance in the complex mechanism of amblyopia

To compare the visual evoked potential (VEP) responses of amblyopic eyes with VEP responses of sound eyes in amblyopic children. A study of 65 amblyopic children with pattern-reversal VEPs elicited by checkerboard stimuli with large, medium and small checks. The children were classified into three groups: Group A, 22 children with anisometropic amblyopia; Group B, 16 children with exotropic strabismic amblyopia; and Group C, 27 children with esotropic strabismic amblyopia. Visual acuity (VA) was significantly worse in the amblyopic eye as compared to the sound eye. However, no statistically significant difference was found between the amblyopic and sound eye of amblyopic children in the three groups for VEP P1 amplitude and latencies for any check sizes. VEP is a very important tool in understanding the complex amblyopic mechanism. Although the sound eye has superior VA, the absence of differences in VEP P1 amplitudes and latencies demonstrate the functional abnormality of the eye considered ‘good’. More studies are necessary to explain why the sound eye in amblyopic children cannot be considered completely normal. Special attention should therefore be paid to amblyopic treatment, as patching can have a negative effect on the sound eye.

Vision rehabilitation: recipients' perceived efficacy of rehabilitation

OBJECTIVE/PURPOSE

This survey was conducted to determine the effect on activities of daily living of persons who report that they have received vision rehabilitation.

DESIGN/METHODOLOGY

This study used a clinical sample to gather information from 417 patients. Of the 417, 105 reported receiving vision rehabilitation. The efficacy of rehabilitation was assessed by asking 20 questions about their activities of daily living prior to and after their rehabilitation. A retrospective pretest (post-then-pre) design was used. Paired t tests were conducted to evaluate the effect of rehabilitation.

RESULTS

A significant difference was found for 13 of 20 questions. Difficulty reading ordinary prints in newspapers showed a large effect size (p=0.0005). Difficulty reading the small print in a telephone book showed a large effect size (p=0.0005). Difficulty doing work or hobbies that require one to see up close showed a moderate effect size (p=0.0005). Difficulty finding something on a crowded shelf showed a moderate effect size (p=0.0005). Difficulty figuring out whether bills received are accurate showed a moderate effect size (p=0.0005). Difficulty shaving, styling one's hair, or putting on makeup showed a small effect size (p=0.016). Difficulties seeing and enjoying programs on television showed a moderate effect size (p=0.0005).

CONCLUSION

Patients with low vision who report having received vision rehabilitation show significant improvements in activities of daily living or specific types of functioning after rehabilitation. Improvement in both near and distance vision activities and in social activities indicates daily functioning was improved and that barriers to activities of daily living were removed.

Relating Binocular and Monocular Vision in Strabismic and Anisometropic Amblyopia

OBJECTIVES

To examine deficits in monocular and binocular vision in adults with amblyopia and to test the following 2 hypotheses: (1) Regardless of clinical subtype, the degree of impairment in binocular integration predicts the pattern of monocular acuity deficits. (2) Subjects who lack binocular integration exhibit the most severe interocular suppression.

METHODS

Seven subjects with anisometropia, 6 subjects with strabismus, and 7 control subjects were tested. Monocular tests included Snellen acuity, grating acuity, Vernier acuity, and contrast sensitivity. Binocular tests included Titmus stereo test, binocular motion integration, and dichoptic contrast masking.

RESULTS

As expected, both groups showed deficits in monocular acuity, with subjects with strabismus showing greater deficits in Vernier acuity. Both amblyopic groups were then characterized according to the degree of residual stereoacuity and binocular motion integration ability, and 67% of subjects with strabismus compared with 29% of subjects with anisometropia were classified as having "nonbinocular" vision according to our criterion. For this nonbinocular group, Vernier acuity is most impaired. In addition, the nonbinocular group showed the most dichoptic contrast masking of the amblyopic eye and the least dichoptic contrast masking of the fellow eye.

CONCLUSION

The degree of residual binocularity and interocular suppression predicts monocular acuity and may be a significant etiological mechanism of vision loss.

Vision, visual needs, and quality of life of older people in rural environments: a report and synthesis of a meeting

Vision as an aspect of rural aging was a major portion of the First International Conference on Rural Aging. Various perspectives on the relationship of vision to rural aging were presented in two symposia, two paper sessions, one workshop and the poster session (a total of 28 presentations). In summarizing this rich and varied material, the author emphasizes that: (a) vision is important to maintaining a healthy, active life as one ages; (b) impaired vision is generally preventable or treatable; (c) well-designed community programs can assist in prevention and treatment; and (d) assessing the effects of these programs requires evaluation of patients' quality of life. More research is needed to refine strategies for creating, maintaining and evaluating community-based eye care programs and integrating them with existing public health or other community programs.

Parallel pathways, noise masking and glaucoma detection: behavioral and electrophysiological measures

PURPOSE

We tested the hypothesis that because of their reduced neural efficiency, glaucoma patients should have increasingly impaired thresholds as external noise is added to a stimulus.

METHOD

We compared the performance of 20 normals (mean age = 39 years) with that of 15 patients with early glaucoma or at very high risk for glaucoma (mean age 45 years). All patients had normal visual acuity. Contrast thresholds were measured on two sets of tasks: (1) behavioral and (2) sweep visually evoked potentials (VEPs). Two stimuli were used (a) 7.5 Hz reversing gratings of 0.69 cpd, and (b) 5.5 cpd gratings. Noise was binary and contrast varied from 0 to 80%. Psychophysical thresholds were determined using a staircase which employed a spatial four alternative forced choice procedure (4AFC) and converged on 50% correct. Sweep VEP thresholds were determined by extrapolation to zero volts as a function of log contrast.

RESULTS

Differences between normal subjects and patients with early glaucoma were not significant without noise. Both the absolute size of the difference and its significance increased as noise level increased. For the behavioral thresholds these trends were clearer with the 5.5 cpd grating, while for the sweep VEPs they were more clear for the 0.69 cpd grating.

CONCLUSION

The performance deficit of glaucoma patients which may be minimal under normal testing conditions is magnified when external noise is added to the stimulus. VEPs and psychophysical thresholds show interesting differences in their sensitivity to this effect. Implications for the early detection of glaucoma are discussed.

Visually evoked potentials evoked by moving unidimensional noise stimuli: effects of contrast, spatial frequency, active electrode location, reference electrode location, and stimulus type

We determined the relative importance of electrode derivation, stimulus type, spatial frequency and contrast in determining the relative size of the late negative and early positive responses of motion elicited VEPs. Seven subjects aged 22-48 years with normal vision were tested binocularly. Motion onset and motion reversal were employed as modes of stimulus presentation. For both, pseudo-random one-dimensional noise patterns whose peak power was at 5.2, 2.6, 1.3, 0.325 and 0.1625 cycles per degree (cpd) were stimuli. Contrasts were 70% and 5%. Active electrodes were placed at Oz, 5 cm to the left of Oz, 5 cm to the right of Oz and a frontal midline position (Fpz) and referenced to linked mastoids. Transient motion reversal elicited a prominent positive response present in all subjects and at low contrasts. Motion onset VEPs have a complex waveform which may be either predominantly positive or negative. The most important variables in determining whether a prominent positivity or negativity is present in the motion onset VEP are the contrast and the spatial frequencies. Data such as these are first efforts in developing recommendations for the motion VEP.

Maturation of binocular luminance interaction in normal young and adult rhesus monkeys

PURPOSE

Our aim was to answer three questions 1) Do adult rhesus monkeys have binocular luminance interactions (BLIs) similar to those found in adult humans? 2) Is BLI in very young rhesus monkeys functionally mature? 3) If not, how does it change with age?

METHODS

We recorded visually evoked potentials (VEPs) in response to sinusoidally modulated uniform fields. The fields were presented dichoptically by varying the relative temporal phase between the two eyes. Monkeys varied in age from 5.6 weeks to 5.25 years.

RESULTS

VEPs were Fourier analyzed and the relative second harmonic amplitudes were taken as the response measure. The second harmonic amplitudes in adult monkeys had an asymmetrical 'V-shaped' function as interocular phase difference (IPD) varied from 0 degrees to 180 degrees, as had been observed previously in adult humans [1]. The youngest monkeys exhibited a symmetrical pattern which became more asymmetrical at older ages and was adult like by about 19 weeks. Asymmetry magnitude and log age correlated 0.97 (p < 0.05) in the monkeys younger than 19 weeks.

CONCLUSIONS

The adult rhesus data are consistent with a model derived from humans which involves two types binocular luminance processing. One combines monocular responses nonlinearly (MNL) and a second combines monocular responses linearly followed by a binocular nonlinearity (MLBNL). These two processes have been associated with the parvocellular (P-) and magnocellular (M-) streams. Within this framework, the data from the youngest monkeys indicate that BLI in the P-stream is relatively less mature at birth than that in the M-stream and develops reaching functional maturity on these measures by around 19 weeks.

Acetazolamide affects performance on the Nagel II anomaloscope

BACKGROUND

Recent reports have indicated that acetazolamide alters human electroretinograms. We wished to determine the effects of administering acetazolamide on performance on the Nagel II anomaloscope.

METHODS

We tested 15 subjects matches of blue-green light to a mixture of blue and green lights (luminance match) on a Nagel type II anomaloscope 2.5 h after ingesting 500 mg of acetazolamide or a placebo.

RESULTS

The mean of the luminance settings for the subjects was 54.4 for the placebo condition and 58.5 for the acetazolamide condition. The mean difference of 4.1 was statistically significant, indicating that following ingestion of acetazolamide subjects were less sensitive to a blue-green light. In two supplementary experiments we tested (1) a second group of four normal subjects using the Nagel type II anomaloscope and (2) the previously untreated eyes of four patients with primary open-angle glaucoma before and after placing them on acetazolamide therapy. In both groups, more blue-green light was needed to make the match after ingestion of acetazolamide.

CONCLUSIONS

Acetazolamide alters the sensitivity of one or more cone populations, probably the carbonic anhydrase-containing cones. The sensitivity loss is reversible and does not appear to be clinically significant. However, the results suggest that patients administered acetazolamide should be excluded from studies which compare the color vision of glaucomatous patients to that of normals.

Normal electro-oculograms in two patients with malignant melanoma of the choroid

The electro-oculogram has been applied in the diagnostic evaluation of eyes with malignant uveal melanoma. Typically, a marked reduction in the light peak to dark trough ratio has been reported. We studied two patients with histologically confirmed uveal malignant melanomas in whom the preenucleation electro-oculograms were normal. The electro-oculogram should be evaluated within the framework of the clinical examination and other ancillary tests in the diagnostic evaluation of a suspected uveal malignant melanoma.

Models of binocular luminance interaction evaluated using visually evoked potential and psychophysical measures: a tribute to M. Russell Harter

We determined subjects' responses to sine-wave modulated lights employing visually evoked potentials (VEPs) and psychophysical thresholds in a series of experiments. The stimuli had the same temporal frequency and mean luminance in each eye but the phase difference between the two eyes was varied so that phase was either the same (dioptic) or different (dichoptic) in the two eyes. The data were fit by a model which had two binocular pathways, one which summed monocular nonlinear elements and a second which had a nonlinearity following the combination of monocular linear elements. In the second channel the outputs of the monocular linear elements were summed at low luminance while at higher luminance levels they were subtracted. Based on variations in the threshold data with temporal frequency, the pathway which summed nonlinear monocular elements was identified with the magnocellular (M) pathway, and the pathway which combined monocular linear elements prior to a binocular nonlinear element was identified with the parvocellular (P) pathway.

The effects of acetazolamide in albino rabbits, pigmented rabbits, and humans

In three separate experiments albino rabbits, pigmented rabbits, and humans were tested following administration of acetazolamide and without acetazolamide. In all three experiments, we recorded electroretinograms (ERGs) under dark adapted and light adapted conditions and measured the b-wave amplitudes. Dark adapted ERG b-wave amplitudes were increased following administration of acetazolamide as compared to control conditions, in albino rabbits, pigmented rabbits and humans. Light adapted b-wave amplitudes showed no statistically significant changes as a function of acetazolamide administration although in all three experiments there was a trend toward light adapted b-wave amplitude reduction following administration of acetazolamide. In the human experiments, ERG a-wave amplitudes were also measured. Light adapted a-wave amplitudes were reduced following administration of acetazolamide. In the human experiments, several behavioral tests were performed, including L'Anthony desaturated D-15, Farnsworth-Munsell 100 hue, Cogan-Gunkel chromatograph, Nagel anomaloscope, Goldmann-Weekers dark adaptometry. There were no consistent changes in the human dark adaptation thresholds or color discrimination, although several measures approached significance.

Tetanus prophylaxis following ocular injuries

The administration of prophylaxis against tetanus following a corneal abrasion is routinely performed in many acute care facilities, despite a lack of support in the literature for its necessity. The risk of developing clinical tetanus from three different types of injuries to the eye was evaluated in an animal model. Clinical tetanus was induced in unimmunized mice by injecting Clostridium tetani organisms or toxin into the anterior chamber. Immunized mice injected intracamerally did not develop signs of tetanus. Tetanus was not induced by topical inoculation of either live organisms or toxin following corneal epithelial debridement or stromal scarification of unimmunized and immunized mice. The results of this study support the administration of prophylaxis against tetanus following perforating ocular injuries. However, our results do not support its routine use following uncomplicated corneal abrasions or other types of nonperforating ocular injuries.

Flicker electroretinograms: a systems analytic approach

We observed multiple maxima and minima in the electroretinogram (ERG) first harmonics which varied as a function of adaptation level, mean illuminance, and modulation depth. Based on differences in response characteristics we identified a minimum of 3 parallel mechanisms operating at 3 frequency regions within the ERG: a low frequency region (less than 10 Hz), a midfrequency region (centered near 20 Hz), and a high frequency region (centered near 40 Hz). The low frequency region was observed both in dark- and light-adapted conditions, was basically linear, and showed nonlinear behavior only at high contrasts in either light or dark adaptation. It may be modeled as a low pass filter. The midfrequency region was clearly observed only above cone threshold, was nonlinear at low contrasts, and may be modeled as a linear filter followed by an essential nonlinearity. The high frequency region was observed under high levels of light adaptation and also was nonlinear at low contrast. It may be modeled also as a linear filter followed by an essential nonlinearity.

Use of 10-Hz flash visual evoked potentials in prediction of final visual acuity in diabetic eyes with vitreous hemorrhage

In 44 diabetic eyes with vitreous hemorrhage, monocular steady-state visual evoked potentials were elicited through closed eyes by a 10-Hz flash. Visual evoked potentials were rated as normal or abnormal on the basis of amplitude and waveform. Abnormal visual evoked potentials were subdivided into mildly abnormal, markedly abnormal and nonrecordable categories. Patients with normal potentials were predicted to have visual acuities of 6/15 (20/50) or better. Patients with abnormal potentials were predicted to have visual acuities of 6/18 (20/60) or worse. Final visual acuities were the best visual acuities recorded in the 6 months after vitreous surgery (vitrectomy) or spontaneous clearing of the vitreous hemorrhage. The visual evoked potential categories and final acuities were compared with a 2 x 2 contingency table. The accuracy was 86%. The visual evoked potential categories and final acuities were associated at a statistically significant level.

Comparison of preoperative 10-Hz visual evoked potentials to contrast sensitivity and visual acuity after cataract extraction

Cataract patients whose surgical outcomes were in question were referred for testing by visual evoked potentials, elicited through closed eyelids by a luminance stimulus (flash) that appeared 10 times per second. Visual evoked potentials were rated as normal (predicted acuity of 20/50 or better) or abnormal (predicted acuity of 20/60 or worse). Postoperative Arden and Optronix contrast sensitivities and visual acuities were determined in 37 patients who had no intraoperative or early postoperative complications. Arden grating scores of less than 100 were rated as normal. The optimal and cutoff spatial frequency values were determined for the Optronix scores. Optimal and cutoff values of greater or equal to 1 c/deg and 12 c/deg, respectively, were rated as normal. Visual acuities were considered normal at 20/50 or better. Preoperative visual evoked potentials were quantitatively compared to the postoperative contrast sensitivities and visual acuities by 2 x 2 contingency tables. The accuracy of prediction was 79% for the visual acuities, 62% for the Optronix optimal values, 70% for the Optronix cutoff values and 62% for the Arden gratings.

Detection of hidden visual loss in multiple sclerosis. A comparison of pattern-reversal visual evoked potentials and contrast sensitivity

The detection of hidden visual loss is important in establishing the diagnosis of multiple sclerosis, especially in patients who have neurologic symptoms of the disease. Both visual evoked potentials and contrast sensitivity have been used for this purpose. We compared the sensitivities of pattern-reversal visual evoked potentials and contrast sensitivity, measured with the Vistech VCTS 6500 chart, in detecting hidden visual loss in 18 patients with multiple sclerosis whose visual acuity was correctable to 20/20 (6/6) or better in the examined eye. Thirteen patients had delayed visual evoked potential latencies. An additional four patients had reduced P100 amplitudes without prolonged latencies. Nine patients had abnormal contrast sensitivity. The visual evoked potential was more sensitive than contrast sensitivity at detecting hidden visual loss in patients with multiple sclerosis (p less than 0.01).

Effect of short-term intraocular pressure elevation on the rabbit electroretinogram

Pattern electroretinograms (PERGs), with a presumed ganglion cell origin, and oscillatory potentials (OPs), with a presumed inner retinal origin, are reduced in glaucoma. Flash ERGs are reduced at intraocular pressures (IOPs) greater than 60 mm Hg. A study was designed to investigate the time-course of change in PERGs, OPs, and flash ERGs after increasing the IOP of ten rabbit eyes to 35-45 mm Hg by using a suction-cup apparatus. Although flash ERG b-wave amplitude was unchanged (P = 0.32), PERGs were reduced (P less than 0.001) immediately after IOP elevation, as were OPs (P = 0.03). Both PERG and OP amplitudes returned to normal immediately after normal IOP was restored. This study showed that the rabbit is a suitable model for studying PERGs. It also suggested that moderate IOP elevation for 10 min reversibly impaired ganglion cell and inner retinal function in the rabbit, although more external function was unchanged.

Static flicker perimetry in glaucoma and ocular hypertension

The visual threshold for standard and flickering targets was determined and compared in 8 glaucoma patients, 8 glaucoma suspects and 13 normal controls. Using a Goldmann size III standard white light target, 25 points in the central 30 degrees of the visual field were tested. The location of these points was designed to reflect areas of the visual field commonly affected by glaucomatous damage. The same determinations were then repeated with the test target flickering at 25 Hz. All glaucoma patients had elevation of the visual threshold compared to normal controls for both standard and flickering targets. The absolute value of threshold elevation was not significantly different between standard and flickering lights. However, when larger targets were used, flicker thresholds were an average 8 dB higher (p less than 0.05) in the glaucoma patients compared to the normals, suggesting improved identification of glaucomatous damage with the use of larger flickering targets.

Comparison of nonabsorbable and absorbable sutures for use in oculoplastic surgery

Nonabsorbable sutures are often recommended for use in oculoplastic surgery. This study compares the in vivo performance of nonabsorbable and absorbable sutures in an animal model and attempts to determine if one suture type is clearly superior for subcutaneous wound closure. The performance of each suture was evaluated using three surgical techniques. Comparison of results revealed that different techniques produce profoundly different results, independent of suture choice. Clinically, all suture types behaved similarly when used with the same surgical technique. Thus, absorbable and nonabsorbable sutures are equally effective under the conditions of these experiments.

Visually evoked potentials and electroretinography in neurologic evaluation

Electrophysiologic testing of the visual system requires primarily the ERG and the VEP. The flash electroretinogram provides information about the outer retina only. The pattern electroretinogram is derived from both the outer retina and the innermost retinal layers including the ganglion cell layer. The VEP is based on electrical information recorded from the visual cortex in response to stimulation of the retina. Thus, the integrity of the entire visual pathway can be tested. Localizing ability of the VEP is limited. Since the visual cortex is heavily weighted by representation of the central retina, peripheral lesions, including those producing peripheral visual field abnormalities that do not impinge upon central fixation, may produce relatively little disturbance of the VEP. As with most tests, electrophysiologic studies of the visual system must be placed in context of the entire examination, including the patient's history and neurologic and especially neuro-ophthalmologic evaluation. Electrophysiologic testing has three main uses in neurology. Pattern-reversal VEPs may be useful in detecting hidden visual loss in multiple sclerosis; VEPs and ERGs can distinguish function from organic visual loss; and VEPs and ERGs can be useful in the diagnosis of visual loss in nonverbal patients, especially in children.

Distribution of carbonic anhydrase among human photoreceptors

The distribution of carbonic anhydrase (CA) among human photoreceptors has been a topic of dispute. In our experiments, by modifying an established enzyme histochemical technique, reproducible staining was observed. Of the cones in the peripheral retina, 91% were positive for CA. The CA-negative (CA-) cones were absent within approximately 8 arc min of the foveal center and their density peaked at 2 arc deg. No CA activity was found in the rods. Morphologic differences were noted between the CA-positive (CA+) and CA- cones. Compared to the CA+ cones, the CA- cones had longer and more nearly columnar inner segments, more nearly spherical nuclei, and more generous amounts of perikaryal cytoplasm. In the peripheral retina, the distance between CA+ to CA+ nearest neighbors were larger compared to CA- to CA+ nearest neighbors (P less than 0.0001). The frequency distribution and morphology of the CA- cones suggest that they are the blue-sensitive cones. As such, this study demonstrates a biochemical similarity between blue cones and rods that may provide insight into the function and phylogeny of the blue cones.

Visual function deficits in glaucoma. Electroretinogram pattern and luminance nonlinearities

The pattern electroretinogram is abnormal in glaucoma. Part of the pattern electroretinogram may be attributed to the summation of responses to luminance increases and decreases (nonlinear luminance responses). We conducted a study to investigate the effect of glaucoma on the pattern electroretinogram component waves and to determine if the flicker electroretinogram nonlinear components are abnormal in glaucoma. We tested 35 subjects in two replications of four conditions: 10- and 20-Hz flicker, and 4- and 10-Hz pattern reversal. Only the even harmonics were recorded. The patients with glaucoma had reduced electroretinogram amplitudes for all measures relative to the normal subjects. Electroretinogram amplitudes of those suspected of having glaucoma were intermediate. The greatest amplitude reductions were for the 10-Hz flicker electroretinogram and the 4-Hz pattern electroretinogram. These results confirm pattern electroretinogram abnormalities and reveal flicker electroretinogram abnormalities in glaucoma.

Visual acuity measurements by swept spatial frequency visual-evoked-cortical potentials (VECPs): clinical application in children with various visual disorders

Previous studies have indicated that visual acuities of normal infants can be estimated with good accuracy using swept spatial frequency visual-evoked-potentials (VECPs). In this report we describe acuity measurements obtained with this technique from 304 examinations performed on 135 children having various visual disorders. When possible, two or more different stimulation frequencies (8, 12, 15 or 24 contrast reversals/sec) were used in each patient, and three to eight sweep VECPs were obtained from each patient under each simulation and recording condition. High correlation coefficients (0.94 - 0.96) between the acuity estimated on each patient from either the single sweep giving the best visual acuity (BSS) or from vector averages (VeA) of the EEG data obtained from several sweeps confirmed previous findings in normal infants. We also found high correlation coefficients among BSS recorded at different temporal frequencies (0.79-0.97) and among comparisons of BSS or VeA acuity to optotype visual acuity (0.6-0.89). Children with clinically undetectable optokinetic responses showed lower visual acuity estimated by BSS than those who demonstrated optokinetic nystagmus. We conclude that the sweep VECP is a valid method, giving estimates of acuity which correlate well with optotype acuity and correspond well to other clinical findings, and that it can be useful in the clinical management of nonverbal patients.

Quantitating the superior visual field loss associated with ptosis

The effect of blepharoptosis on the superior visual field was assessed using a series of specially designed contact lenses to simulate ptosis in normal subjects. We found a progressive decrease in the superior visual field at the 90 degree vertical meridian, which was proportional to the degree of simulated ptosis. Our results were in close agreement with both a theoretical model and previous clinical observations. These results are important in evaluating patients contemplating ptosis surgery, as well as in visual field testing for neuro-ophthalmic disorders.

Adult vernier thresholds do not increase with age; vernier bias does

Vernier acuity and vernier bias were examined in persons aged 20 to 79 years using a method of adjustments. Vernier bias (mean error) showed a sharp increase between 35 and 45. Vernier acuity (standard deviation or precision of alignment) did not vary significantly with age. These different results indicate the importance of separate evaluation of acuity and bias. Vernier acuity is little affected by minor optical changes that occur with age. Therefore, normal vernier acuity in older persons suggests that the neural substrates which underlie fine-grain discrimination of object location are unaffected by aging over the range investigated.

Dynamic stereoacuity: a comparison of electrophysiological and psychophysical responses in normal and stereoblind observers

We compared stereoscopic thresholds determined psychophysically and by using visually evoked potentials in normal adult and stereoblind subjects. For normal observers there was a strong linear relationship between visual evoked potential amplitude and disparity (r = 0.86 on average). However, stereoblind observers' responses showed no relationship to disparity (r = 0.18 on average). For normal observers, log visual evoked potential stereo thresholds determined by an extrapolation procedure were on average within 0.17 octaves of the psychophysically determined log thresholds. They did not differ significantly from psychophysical thresholds, and they correlated significantly with behavioral thresholds (r = 0.86).

Preoperative prediction of postoperative visual acuity in patients with cataracts: a quantitative review

Many tests of visual function have been proposed as means of preoperatively evaluating cataract patients' surgical outcomes. It is impractical to compare all of these tests simultaneously on the same group of patients. Quantitative reviews apply quantitative methods to comparisons across studies. We compared the results of 52 reports in which cataract patients' postoperative acuity was predicted by means of visually evoked potential, laser interferometry, or projection tests (potential acuity meters-pinhole). The results of each study were summarized in a 2 x 2 contingency table. Summary statistics were compared by means of analysis of variance and post hoc tests. Despite difficulties in metaanalysis, we found the visually evoked potential a better predictor with dense opacities. We recommend standardization in a quest for more precise predictions of postoperative visual acuity.

The pattern electroretinogram (PERG) in ocular hypertension and glaucoma

Studies of normal subjects and of patients with optic nerve disorders suggest that one of the components of the pattern electroretinogram (PERG), the second negative wave, is related to optic nerve function and appears to be diminished even when the condition is relatively mild, with little alteration of visual acuity. It is known that significant loss of nerve fibers may occur prior to the development of visual field loss. We have investigated the PERGs of a group of subjects with early glaucoma and ocular hypertension, comparing them with normal subjects, and have found a selective reduction in the second negative wave in patients with evidence of optic nerve dysfunction. The PERG may prove helpful in discriminating those patients with ocular hypertension who are destined to develop visual field loss unless medical or surgical therapy were to be employed.

Prediction of post cataract extraction visual acuity: 10 Hz visually evoked potentials

Cataract patients suspected of having disease that might interfere with good postoperative visual function were evaluated by eliciting monocular steady-state luminance visual evoked potentials (VEPs) with closed eyes at a stimulus rate of 10 flashes/sec. VEPs were rated as either normal or abnormal. Patients with normal VEPs were predicted to have visual acuity of 6/15 (20/50) or better. Patients with abnormal VEPs were predicted to have acuities of 6/18 (20/60) or worse. Postoperative acuities were determined for all patients who underwent surgery and who had no intraoperative or early postoperative complications. The predicted and observed postoperative acuities were quantitatively compared for the 59 patients who met these criteria, using a 2 X 2 contingency table. The chi-square was significant (p less than .001). The overall accuracy of prediction was 80%. Accuracy of the predictions for patients with preoperative acuities of 6/60 (20/200) or better was compared with the accuracy of the predictions for those with preoperative acuities of 60/120 (20/400) or worse. There was no significant difference (p greater than 0.10).

10-Hz flash visual evoked potentials predict post-cataract extraction visual acuity

Cataract patients suspected of having disease which might interfere with good postoperative visual function were referred for evaluation. Monocular steady-state luminance visual evoked potentials (VEPs) were elicited with closed eyes at a stimulus rate of 10 flashes/sec. VEPs were rated as either normal or abnormal. Patients with normal VEPs were predicted to have an acuity of 6/15 (20/50) or better. Patients with abnormal VEPs were predicted to have acuities of 6/18 (20/60) or worse. Postoperative acuities were determined for all patients who underwent surgery and who had no intraoperative or early postoperative complications. The association of preoperative VEPs and observed postoperative acuities were quantitatively compared by a 2 x 2 contingency table for the 59 eyes which met these criteria. The chi-square was significant (p less than 0.001). The overall accuracy of prediction was 76%. Accuracy was 80% for patients with a preoperative acuity of 6/60 (20/200) or better and 75% for those whose postoperative acuity was 6/120 (20/400) or worse. This difference was not statistically significant.

Pattern electroretinogram: effects of reference electrode position

The pattern electroretinogram has assumed greater clinical and experimental significance because of its inner retinal origins. However, clinical tests may be confounded by an artifact. We tested subjects varying reference electrode position and eye stimulated while employing the Dawson-Trick-Litzkow (DTL) fiber electrode as the active electrode. The presence of a statistically significant artifactual response could not be confirmed. However, the variability of responses elicited with the outer canthus was less and the signal-to-noise ratio greater than with other reference positions.

Correspondence matching in apparent motion: evidence for three-dimensional spatial representation

The path of an object in apparent motion depends on correspondence matching, the decision that images seen at different places and at different times represent the same object. One determinant of correspondence is proximity. Still debated, however, is whether proximity is defined in a two- or three-dimensional spatial representation. Observers judged the motion path taken by an object with two neighbors of different apparent depth. Given similar two-dimensional distances, objects moved toward the neighbor of the same apparent depth. This is evidence that correspondence operates in a three-dimensional spatial representation.

The effects of behavioral vision training on multiple aspects of visual functioning in myopic adults

Twenty myopic adults were randomly assigned to either a behavioral visual acuity training program or to a no-treatment control group in order to assess changes in several aspects of visual behavior. Measures were obtained both pre- and posttraining for a number of variables. These included recognition and resolution visual acuity, contrast sensitivity, perceived clarity and confidence of responses, and stimulus duration. Results indicated that training subjects significantly improved on all three measures of visual acuity: recognition acuity, resolution acuity, and contrast sensitivity. Improvements in acuity were associated with significant improvements in the perceived clarity of the stimuli but not in the confidence of the subject's response. These data expand our knowledge concerning the effectiveness of behavioral training programs in improving visual acuity in myopia. The potential utility of such programs is discussed.

Acuity estimated by visually evoked potentials is affected by scaling

Seven subjects whose corrected Snellen acuities were normal had their monocular acuities (14 eyes) tested by visually evoked potentials (VEPs) elicited by eight checkerboard patterns which reversed 15 times per second. Check size ranged from 20 to 3.4 min. arc. Monocular VEP acuities were determined by least squares regression with linear or logarithmic scales of amplitude and pattern size. Pattern size was measured as arc minutes (horizontal size) or fundamental spatial frequency of the checkerboard. The extrapolated VEP acuities were obtained by analyses of variance and post hoc tests. The presence of statistically significant differences in VEP acuity which result from varying combinations of stimulus and response scales indicates a need for caution in selecting scales for VEP estimates of visual acuity.

Visually evoked potential (VEP) acuity: testability in a clinical pediatric population

The visually evoked potential (VEP) elicited by pattern response is used to assess the visual acuity of preverbal infants in research situations, but few reports indicate the percentage of patients successfully completing the tests (testability). Data are presented to illustrate the testability of acuity assessed by VEPs with clinical populations of preverbal and neurologically handicapped children. 166 referrals in a 9-month period to an electrodiagnostic clinic indicated that 75% of the referrals less than 3 years old, and 87% of the neurologically handicapped referrals were testable. The testability of VEP acuity is as great or greater than other procedures for examining the visual functions of non-verbal or unco-operative patients.

Developmental physiological optics and visual acuity: a brief review

The development of optical and neural factors affecting visual acuity is reviewed with the aim of determining the age at which the relationship between optical and neural factors become mature. Delayed development of extrastriate cortical and indirect visual pathways may account for differences in acuity assessed by preferential looking and pattern reversal VEPs.

Canine visual acuity: retinal and cortical field potentials evoked by pattern stimulation

The visual acuities (i.e., visual thresholds for pattern detection) of four dogs under neuromuscular block were measured using visually evoked cortical potentials (VECP) and/or pattern-evoked retinal potentials (PERR). Stimuli were phase-reversing square-wave gratings with a mean luminance of 86 cd/m2 and 70% contrast. The mean of the VECP thresholds of two dogs tested was 12.59 cycles per degree (cycles/deg). The mean of the PERR thresholds of four dogs tested was 11.61 cycles/deg. The difference between VECP and PERR thresholds was not statistically significant. VECP acuities appear to be determined at or before the last stage of retinal processing (PERR). Our estimates of canine acuity are 1.3-2 times those reported for cats and 0.2-0.4 times those reported for primates when tested under comparable luminance and contrast conditions.

Interocular suppression in adults and infants using anaglyphic stimuli: visually evoked potential measures

Interocular suppression, assessed by monocular VEP amplitude reduction, was investigated in 3 infants, average age of 3 months, and 8 adults. A dichoptic simultaneous masking paradigm was employed, the two eyes being disassociated by red and green filters which transmitted non-overlapping wave lengths of light (anaglyphic method). One eye was continuously presented with either darkness, a diffuse green light, or two green dot patterns, containing either 20' or 80' dots. The other eye was flashed with either red diffuse light, a red 20' dot pattern, or a red 80' dot pattern. In both adults and infants, monocular VEP amplitude was reduced as the size of the continuously presented dots increased (pattern suppression) and a smaller amplitude response occurred when dots of equal size were presented than when data of different size were presented (size-specific suppression). The relative and absolute magnitudes of interocular pattern suppression were similar for adults and infants. However, the relative and absolute magnitudes of size-specific suppression were larger for adults than for infants. Pattern interocular suppression was inferred to be relatively more mature in 3 month olds than size-specific suppression. The relative lack of size-specific suppression suggests a relative immaturity of binocular spatial frequency or size channels.

Effects of visual deprivation on monocular acuities of humans and animals

A selective review of the effects of visual deprivation on acuity in animals has been presented along with data on the effects of visual deprivation on monocular acuities in children. A comparison of the visually deprived children and animals indicated (1) that no one deprivation state is a satisfactory model of the effects of visual deprivation but (2) that comparable deprivation states have similar effects on visual acuity across species (at least in cat, monkey, and human). Possible mechanisms involved in the development of amblyopia were presented: (1) binocular competition, (2) form deprivation resulting from retinal defocus, and (3) abnormal oculomotor proprioception. The presence of binocular amblyopia suggests that binocular competition is not a necessary condition for the development of amblyopia. The effects of patching therapy and treatment of human monocular deprivation or visual acuity were found to be consistent with their appropriate animal models. While animal models have great potential for elucidating the mechanisms of amblyopia, the limitations of any one deprivation model are clear. The development of visual assessment technique for infants and young children seems essential for therapy of the effects of visual deprivation, especially monocular deprivation.

Retinal and cortical pattern responses: a comparison of infants and adults

Retinal and cortical responses to pattern reversal stimulation were recorded simultaneously in three human infants of average age 3.5 months and two adults of average age 28.5 years. The relative power of retinal signals as a function of spatial frequency for both adults and infants was very similar and extrapolated to a threshold of about 30 c/deg [6/6 (20/20)] as did the relative power of the adult cortical signal. The infant cortical signal was relatively more attenuated at higher spatial frequencies and extrapolated to a threshold of 8.5 c/deg [6/22.2 (20/74)]. A greater relative maturity of retinal as compared with cortical neural function in 3.5-month-olds is inferred.