Self-Testing of Vision in Age-Related Macula Degeneration: A Longitudinal Pilot Study Using a Smartphone-Based Rarebit Test.

Purpose. There is a need for efficient self-tests of vision in patients with neovascular age-related macula degeneration. A new tablet/smartphone application aiming to meet this need is described and its performance is assessed in a longitudinal pilot study. Materials and Methods. The new MultiBit Test (MBT) employs segmented digits defined by rarebits, that is, receptive field-size bright dots briefly presented against a dark background. The number of rarebits per digit segment was varied in a cyclic fashion, in preset steps. There were no fixation demands. Twenty-eight patients with neovascular AMD of varying severity were monitored for an average of 30 weeks. Test scores were evaluated on an individual basis, by contrasting observed trends with the clinical status recorded at independently scheduled clinical examinations. Results. Serial plots of MBT results revealed gradual improvement after successful antineovascular treatment. Recurrences were signalled by gradual deteriorations of results. Test results remained stable during clinically stable time intervals. MBT results agreed well with clinical assessments whereas an acuity test performed at chance level. The MBT was well accepted by all subjects. Conclusions. The MBT appears to have a good potential for effective self-testing of vision in AMD and merits large-scale studies. Exploration of MBT performance with other forms of macula conditions may be worthwhile.

New rarebit vision test captures macular deficits hidden to acuity tests.

PURPOSE: Evaluation of a new personal-computer-based vision test aimed for rapid and accurate assessment of macular conditions such as age-related macular degeneration (AMD). METHODS: The new test depends on segmented digits defined by rarebits, that is, receptive field-size bright dots briefly presented against a dark background. Digit size was fixed at 40 × 50 min of arc. Digit positions were varied at random within a 4.6 × 3.5-degree test field. There were no fixation demands. The number of rarebits per digit segment could be varied between 3 (the minimum needed for veridical perception) and 128, in 11 preset steps. The test task was to find the smallest rarebit number required to recognize the test digits. Thirty-seven patients with various stages of AMD and 25 control subjects participated in the evaluation, which also included a standard acuity test. RESULTS: Analysis of receiver operating characteristics indicated significantly better discrimination by the rarebit test. Rarebit numbers >16 appeared to reliably indicate the presence of oedema. CONCLUSION: The rarebit test appeared well suited for fine grading of vision in AMD. The simple set-up and the lack of fixation demands made for practicable examinations of short durations. The test is available for free on the Internet.

Identification of functional visual field loss by automated static perimetry.

PURPOSE: Diagnosis of functional visual field loss, that is, field loss lacking objective corollaries, has long relied on kinetic visual field examinations using tangent screens or manual perimeters. The modern dominance of automated static perimeters requires the formulation of new diagnostic criteria. METHODS: Retrospective review of automated perimetry records from 36 subjects meeting clinical and tangent screen criteria for functional visual field loss. Thirty-three normal eyes and 57 eyes with true lesions, including optic nerve compression, glaucoma, anterior ischaemic optic neuropathy and vigabatrin toxicity, served as controls. RESULTS: Standard automated perimetry statistics were unable to reliably discriminate organic versus non-organic visual field loss. Subjective evaluation of perimetric maps indicated that functional fields generally could be identified by the presence of severe and irregular contractions and depressions that did not conform to the visual system's neuro-architecture. Further, functional fields generally presented one or more isolated threshold 'spikes', that is, isolated locations showing much better than average sensitivity. On repeated examinations, threshold spikes always changed locations. Visual evaluation for spikes proved superior to an objective computational algorithm. Fairly reliable objective discrimination of functional fields could be achieved by point-wise correlations of repeated examinations: median intertest correlation coefficients equalled 0.47 compared with 0.81 for true lesions. CONCLUSION: Functional visual loss can be identified by automated static perimetry. Useful criteria include severe and irregular contractions and depressions, the presence of isolated threshold spikes and poor intertest correlations.

Rapid assessment of neurovisual integrity using multiple rarebits.

OBJECTIVE: Rapid assessments of vision commonly rely on visual acuity testing alone. Although well suited for uncovering optical defects, visual acuity tests may fail to detect dysfunction of the neural substrate. There is a need for a rapid companion test sensitive to neural damage. DESIGN: Evaluation of diagnostic tests. PARTICIPANTS AND CONTROLS: Forty-seven patients with optic nerve or visual pathway lesions of low to moderate severities and 30 normal subjects. METHODS: A new computer-based quick test of neurovisual integrity was developed using segmented digits defined by rarebits, that is, receptive field-size bright dots briefly presented on a dark background. MAIN OUTCOME MEASURES: The test variable was the number of rarebits per segment; digit size was fixed. The test task was to call out verbally all digits that were seen during an 8-second presentation sequence. Test outcomes were contrasted with the results of an optotype acuity test and automated perimetry. RESULTS: All subjects easily grasped the test task. The normal subjects read, on average, 5.6 (± 0.5 standard deviation) of the 6 digits contained in the test sequence, whereas the patients averaged 3.3 ± 1.8 digits. The numbers of digits read correlated modestly with the acuity and perimetry results. Analysis of receiver operating characteristic curves indicated that the multiple rarebit test provided the best discrimination. CONCLUSIONS: The multiple rarebit test seemed to be highly capable of detecting neurovisual dysfunction. Its simplicity and uniquely short duration indicate a useful role in screening settings. The test is available free on the Internet. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found after the references.

Performance of a rapid rarebit central-vision test with optic neuropathies.

PURPOSE: Rarebit vision tests probe for gaps in the neuro-retinal receptive field matrix, using bright micro dots on a dark background. Previous reports have found central-vision rarebit tests useful for macular lesions. Their performance with lesions of the anterior visual pathways has not been explored. METHODS: Twenty-two subjects with optic nerve lesions of light to moderate severities were examined with a novel, self-contained rarebit test. Outcomes were contrasted with results of high-pass resolution perimetry and a threshold letter acuity test. RESULTS: The results of the three tests differed significantly from those of normal control subjects. There were no meaningful inter-test correlations. Analysis of receiver-operating characteristic curves revealed closely similar powers of discrimination. Mean test time for the rarebit test was 1:42 min, and for the other tests, it was approximately 5 min each. CONCLUSIONS: The rarebit test appeared highly capable of detecting optic neuropathies and chiasmal lesions. Its simplicity and short test duration indicate a useful role in screening settings.

Postural function and subjective eye level in patients with idiopathic normal pressure hydrocephalus.

Disturbance of posture is a frequent indication of idiopathic normal pressure hydrocephalus (iNPH) and is characterised by an increased sway in the frontal and sagittal planes. Further, iNPH patients with increased backward sway are known to have a defective perception of the subjective visual vertical (SVV), with the upper portion of an articulated rod tilted towards themselves. The objective of the present study was to compare subjective eye level (SEL) with actual eye level (EL) and compare this data with SVV and postural function. Twenty iNPH patients and ten normal controls estimated SEL by placing an adjustable horizontal line at EL. Sway pattern and SVV were also examined as previously described. The patients presented larger errors on downward as compared to upward line adjustments; all patients also presented a SVV tilted towards them. The patients swayed more in the sagittal than in the frontal plane at a higher speed than the normal controls, and they were relatively less helped by their vision. This is in accordance with the tendency to fall backwards seen in many iNPH patients. iNPH patients have a tendency to place SEL higher than EL and this, together with examination of SVV and sway pattern, suggests defective internal processing of gravicentric information.

Deviations of the visual upright in three dimensions in disorders of the brainstem: a clinical exploration.

Deviations of the subjective visual vertical in the roll or fronto-parallel plane occur commonly in disorders of the brainstem and have been extensively explored. In contrast, little is known about deviations in other directions. The present retrospective study focused on deviations in the pitch (sagittal) direction in 176 patients with a wide variety of disorders. The test task was to set a self-illuminated rod in the apparent upright position, in total darkness. Abnormal results (outside ± 4°) were recorded in 58% of the subjects. Negative (top backward) deviations were the most common, particularly with mass lesions in the pineal region, obstructive hydrocephalus, cerebellar lesions and crowding at the craniocervical junction. Positive and negative deviations were about equally common with focal intra-axial lesions. Negative deviations appeared related to dorsal locations of lesions and vice versa. Normal pressure hydrocephalus, Parkinson's disease and progressive supranuclear palsy were associated with smaller deviations, without a clear directional preponderance, and a larger individual variability. Most subjects lacked overt clinical corollaries. The most common ocular signs were aqueduct syndromes (n = 17) and ocular tilt reactions (n = 12), which were associated with deviations in 47 and 92% of instances, respectively. Subjective corollaries of deviation were never reported, not even by those subjects who showed a dramatic improvement upon resolution of the underlying condition. Deviations were also assessed in roll in a subgroup of 40 patients with focal lesions. Thirty subjects returned abnormal results: 13% in roll, 47% in pitch and 40% in pitch and roll. The direction of roll deviation appeared primarily related to laterality, with clockwise deviations with right-sided lesions and vice versa. All subjects with ocular tilt reactions had combined pitch and roll deviations, implying a common neural substrate. Correlation analyses, geometrical modelling and experimental self-observations indicated that deviations in pitch were attributable to cyclotorsional asymmetries between the eyes. The frequent co-existence of abnormal pitch and roll results implies that the true axis of deviation in focal brainstem disorders commonly falls outside traditional reference planes. The term 'visual upright in three dimensions' is suggested to identify unrestricted measurements, preserving the established term 'visual vertical' for measurements confined to the roll plane. Assessment of the visual upright in three dimensions provides a new, quantitative angle on brainstem disorders. The test appears useful for identifying a ubiquitous yet clinically silent feature of brainstem disease and also for monitoring the evolution of underlying conditions. More detailed explorations appear well motivated.

Diagnosis and grading of papilledema in patients with raised intracranial pressure using optical coherence tomography vs clinical expert assessment using a clinical staging scale.

OBJECTIVES: To compare and contrast 2 methods of quantitating papilledema, namely, optical coherence tomography (OCT) and Modified Frisén Scale (MFS). METHODS: Digital optic disc photographs and OCT fast retinal nerve fiber layer (RNFL) thickness, fast RNFL map, total retinal thickness, and fast disc images were obtained in 36 patients with papilledema. Digital optic disc photographs were randomized and graded by 4 masked expert reviewers using the MFS. We performed Spearman rank correlations of OCT RNFL thickness, OCT total retinal thickness, and MFS grade from photographs. RESULTS: OCT RNFL thickness and MFS grade from photographs correlated well (R = 0.85). OCT total retinal thickness and MFS grade from photographs had a similar correlation of 0.87. Comparing OCT RNFL thickness with OCT total retinal thickness, a slope of 1.64 suggests a greater degree of papilledema thickness change when using the latter. CONCLUSIONS: For lower-grade abnormalities, OCT compares favorably with clinical staging of optic nerve photographs. With higher grades, OCT RNFL thickness processing algorithms often fail, with OCT total retinal thickness performing more favorably.

A compact rarebit test for macular diseases.

BACKGROUND: Rarebit testing implies probing for gaps in the neuro-retinal receptive field matrix, using bright microdots on a dark background. Previous reports have found rarebit testing useful for the detection of macular lesions. In its original implementation, the test requires darkroom facilities and a long test distance (2 m). METHODS: A self-contained rarebit test device was realised using a modified miniature data projector driven by a laptop computer. Its performance was assessed in normal subjects and in patients with advanced age-related macular degeneration. RESULTS: Normal subjects (N=49) produced test results very similar to those reported for the original rarebit fovea test. The patient group (N=12) performed significantly worse. The reproducibility was good, and the mean test time was 142 s. CONCLUSION: The new test allows portable rarebit testing for neuro-macular damage, without the need for a darkroom. It may prove useful for screening for early age-related macular degeneration.

The lazy shadow: a monocular counterpart to the Pulfrich stereo phenomenon.

BACKGROUND: The Pulfrich phenomenon is a dynamic stereo dysmetropsia attributed to an asymmetry of neural conduction between the eyes. The phenomenon may arise spontaneously with ocular and neurological disease and may be induced in normal subjects by placing a light-attenuating filter before one eye. By analogy, it is predicted that a localised variation of retinal illumination within one and the same eye should affect the perception of moving targets. METHODS: A rotating, nesting square display was generated by computer graphics. The inner square was painted bright white, the outer dim grey. Luminances, rates of rotation and angular sizes were varied. RESULTS: On rotation, the outer, dimmer square appeared to lag behind the inner, brighter one, as a "lazy shadow". The lag was measured quantitatively in normal observers by applying a compensatory lead to the lagging square. The magnitude of lag was found to depend on luminance, spin rate and visual angle. Lags exceeding 10 degrees were observed under optimum conditions. CONCLUSIONS: The experimental results confirm the existence of a monocular counterpart to the binocular Pulfrich phenomenon. Distortions of moving images are likely to occur spontaneously with monocular, localised visual field defects.

Influence of ageing on visual field defects due to stable lesions.

BACKGROUND: Knowledge about the effects of ageing on visual field defects is very sparse. METHODS: Long-term follow-up records were examined from 28 patients with light-to-moderate visual field defects remaining after surgery for pituitary tumours. All were proven free from tumour recurrences and complicating disorders. Hence, all had isolated, stable lesions of the chiasm. Follow-up periods ranged over 4-18 years (median 9). Using high-pass resolution perimetry, results were analysed from the central-most test locations in the upper temporal and upper nasal quadrants. The former typically bear the brunt of damage whereas the latter are least affected. Each patient contributed results from one eye only. Fixation stability and reproducibility were uniformly good. RESULTS: Measuring values from the nasal quadrants remained essentially constant throughout the follow-up periods. Results from the temporal (T) quadrants were contrasted with those from the nasal (N) quadrants by calculating the T/N ratios, which were then individually regressed over follow-up periods. Hence, each patient was his or her own control. The absolute majority of regression coefficients (25 out of 28) did not significantly differ from 0. CONCLUSION: The rate of age-related loss of neural channels appears to be identical in normal and abnormal visual field areas in subjects with stable mid-chiasmal lesions.

Vigabatrin-associated loss of vision: rarebit perimetry illuminates the dose-damage relationship.

PURPOSE: The utility of vigabatrin in the treatment of epilepsy is partially offset by its retinal toxicity. The relationship between dosage and damage is obscure. This may be due to perimetric shortcomings. The new technique of rarebit ('microdot') perimetry might be more informative. METHODS: Twelve patients who had been treated with vigabatrin for various durations were examined by manual, kinetic perimetry and by rarebit perimetry. RESULTS: Rarebit results differed significantly between patients and normal controls and rarebit deficits were directly proportional to cumulated vigabatrin doses (correlation coefficients were - 0.92 in the nasal field and - 0.82 in the temporal field). Manual perimetry results were less clearly related to dosage (r = - 0.54 and r = - 0.73, respectively). CONCLUSION: Rarebit perimetry indicates that each treated subject will develop visual loss and that visual loss will be proportional to the accumulated dose. Conventional perimetry is less well suited to detecting and quantifying vigabatrin-associated visual loss.

Visual field of high-pass resolution perimetry in normal subjects.

PURPOSE: To investigate the properties of the visual field of high-pass resolution perimetry in normal subjects. METHODS: Four centers collected normative data for high-pass resolution perimetry. In two of the centers the subjects were stratified by age. One eye was tested per subject using high-pass resolution perimetry (Ophthimus). We tested 640 normal subjects and describe their visual field results by test location. We also analyzed the data by concentric zone, age, and by testing center. RESULTS: The individual test location averages confirmed a reduction in resolution with eccentricity. Resolution thresholds increased with age by 0.025 dB per year (P < 0.001). The mean ring size increased by about 1 dB from age 20 to 70. Among centers there were significant differences in the means and the change in threshold with age (P = 0.009). CONCLUSION: The normal visual field of high-pass resolution perimetry is characterized by an increase in threshold with eccentricity. We found significant differences among the centers that were likely due to multiple factors including differences in subject selection criteria. Whether such differences occur with other perimetric techniques is unknown.

Characterization of vigabatrin-associated optic atrophy.

AIMS: To report the discovery of a previously unknown form of optic atrophy associated with use of the anti-epileptic drug vigabatrin. METHODS: We conducted a retrospective analysis of digitally enhanced ocular fundus photographs, kinetic visual field maps and treatment parameters for 25 patients, who were selected to represent a large spectrum of visual field defects. RESULTS: In all, 21 patients (84%) evidenced subtle, diffuse atrophy of the retinal nerve fibre layer, in a pattern accessible to scoring. Atrophy scores correlated with visual field remains and cumulative vigabatrin doses. A pathophysiological model is proposed that involves the lengths of intraocular (unmyelinated) retinal ganglion cell axons. CONCLUSION: Optic atrophy attests to the irreversible nature of vigabatrin's visual toxicity. Ocular fundus imaging should prove useful for objectively monitoring vigabatrin-treated subjects for visual toxicity.

Subjective visual vertical and Romberg's test correlations in hydrocephalus.

OBJECTIVE: Exploration of the subjective visual vertical in pitch and Romberg's test in patients with hydrocephalus. Patients Eleven patients with communicating normal pressure hydrocephalus and six with non-communicating hydrocephalus due to aqueductal stenosis were examined before and after surgical treatment. METHODS: The subjective visual vertical was examined with a simple, custom-made articulated rod. The rod was faintly illuminated from within so as to appear floating in space when presented in darkness. The test task was to manually adjust the rod's position in pitch so that it appeared perfectly vertical. Romberg's test was performed under standardized conditions. RESULTS: Patients with a backward movement on Romberg's test showed a deviation of the subjective visual vertical, tilting the upper end of the rod closer to their eyes. Patients moving in other directions tilted the rod in the opposite direction (p < 0.01). The time in which the patients managed Romberg's test with open eyes correlated with the intratest variability of rod placement (r = 0.86, p < 0.001). After surgery, improvements on Romberg's test correlated with a decreased intratest variability of the subjective visual vertical. There were no differences between the two patient groups. CONCLUSIONS: Quantitative measurements of the subjective visual vertical in pitch correlate strongly with results of Romberg's test in patients with hydrocephalus.

New, sensitive window on abnormal spatial vision: rarebit probing.

Clinical tests have a poor sensitivity to low to moderate degrees of neuro-visual damage, possibly because their test targets involve numerous receptive fields. A new test used briefly exposed microdots of high contrast. Multiple visual field areas were probed repeatedly, with ever-new microdot positions. Normal subjects responded to a median 96.0% of probes. Patients with different visual field defects missed larger numbers of probes within defects and the deeper the defects, the larger the number of misses. Patients with minor chiasmal lesions averaged 1.8 times larger defects in microdot perimetry than in high-pass resolution perimetry, indicating superior sensitivity to minor damage.