Conventional Visual Testing Research Articles

The contribution of optical coherence tomography in neurodegenerative diseases

This review investigates the contribution of optical coherence tomography (OCT) to monitoring of neurodegeneration in the anterior visual pathway of patients with neuromyelitis optica, Alzheimer's disease, and Parkinson's disease. Despite a 'normal' regular ophthalmologic examination, some patients present visual complaints, and OCT might better explain the mechanism associated to neuronal and axonal losses that contribute to this clinical condition. The eye can be considered a 'window' to the central nervous system that can be directly accessed through OCT. Prior studies have suggested that pathologic processes in the brain are very similar to what happens in the eye in neurodegenerative diseases, and OCT has confirmed these abnormalities regarding the anterior visual pathway. It is supposed that transsynaptic neurodegeneration in lesions of the posterior visual pathway may play a role in the neurodegeneration process of the anterior visual pathway. Retinal nerve fiber layer, retinal ganglion cells, and inner retinal layers are considered surrogate biomarkers in the progression of neurodegenerative diseases. Because OCT is able to accurately measure neuropathological ocular features, its application has increased both in neuroprotection studies and in treatment. In fact, it may prove to be a unique evaluation tool in comparison with conventional visual tests. (Supplementary Digital content 1, http://links.lww.com/COOP/A10).

Sex-specific differences in retinal nerve fiber layer thinning after acute optic neuritis

The primary objective of this study was to explore the potential influence of gender on recovery from optic neuritis (ON) by determining whether differences in retinal nerve fiber layer (RNFL) thickness can be detected between men and women 6 months after an ON event. In this prospective cohort study, 39 men and 105 women with acute ON underwent repeat visual and optical coherence tomography (OCT) testing. The main outcome measures were change in RNFL measurements for male and female patients 6 months after ON. Men were older (mean age = 39 years) than women (35 years) (p = 0.05) in this study, and more men (62%) than women (41%) had a diagnosis of relapsing-remitting multiple sclerosis (MS) (p = 0.02). Because age and MS subtype were 2 significant covariates, both variables were controlled for in multiple regression analyses. Other covariates controlled for in the multivariate regression included disease duration (years), use of disease-modifying therapy (yes/no), and use of high-dose corticosteroids for acute ON (yes/no). After 6 months, mean RNFL values were lower in men (74 μm) than women (91 μm) (p < 0.001). Men showed more apparent change in RNFL thickness in their ON eyes from baseline to 6 months after ON than women (p = 0.003). There may be differences in recovery between men and women after ON, which can be difficult to detect with conventional visual testing. Our findings raise interesting questions about the potential influence of gender in MS, which may be explored in future studies.

Detection of low level cryoglobulins by flow cytometry

Several patients with cryoglobulin (CG) associated symptoms are seronegative for CG and other potentially causative biomarkers. We analyzed whether it is possible to detect cryoprecipitates by flow cytometry and whether the sensitivity of their demonstration can be increased as compared to visual inspection. Sera from 91 patients with suspected CG associated symptoms and 33 healthy controls were examined for the presence of CG by conventional visual testing and by flow cytometry for small diffracting particles. For calibration purposes we tested lipid micelle dilutions (positive controls) by both methods. The minimum concentrations of lipid micelles to be detected by visual inspection and flow cytometry were 128.5 and 2.0 pg ml(-1), respectively. Among the 91 patients and 33 controls, only 1 patient serum was positive for CG by conventional testing. This sample was also positive on flow cytometry. In the serum of a patient known to be positive for CG, laser diffracting particles were quantified by flow cytometry after keeping serum at 4°C for 3 days. Of the 91 patients, 14 additional samples displayed cold precipitates which redissolved after rewarming during flow cytometry. All 15 (1 + 14) patients positive for CG on flow cytometry suffered from symptoms usually associated with CG. Some precipitates were labeled with anti IgG and IgM antibodies confirming that the particles detected by flow cytometry contained immunoglobulins. No small diffracting particles were detected in the sera of the 33 healthy controls. Flow cytometry is equally specific but much more sensitive in the detection of CG than visual inspection.

Perception of very small visual stimuli in the fovea: normative data for the Rarebit Foveal Test

Background: Conventional visual tests are not sensitive enough to detect low degree neural damage, as 6/6 (1.0) visual acuity can be upheld with less than two‐thirds of the normal number of optic nerve axons. The aim of the current study was to evaluate the physiologic properties of a new computerised test, the Rarebit Fovea Test (RFT), using very small stimuli, by quantifying the effect of age and binocular summation in relation to stimulus luminance.Methods: The RFT relies on the perception of very small (less than 0.5 minutes of arc) bright stimuli. Two different experiments were performed.1 Thirty‐five subjects (age 19 to 63 years) were tested with five different stimulus luminances, 158, 64, 53, 41 and 33-cd/m2.2 Nineteen subjects (age 19 to 63 years) were tested using binocular stimulation to define the binocular summation.Results: Significantly reduced median hit rates were observed at luminances of 53-cd/m2 or below. Age and mean hit rate correlated negatively at all luminance levels below 158-cd/m2. The mean hit rate from binocular stimulation, compared to the highest value from monocular stimulation in the same subject, was increased by a factor of 1.54 ± 0.45 (SD). No age effect was found regarding binocular summation.Conclusions: The results in the current study indicate that RFT can identify some of the well‐known features of the visual system, that is, the effects of age and binocular summation, provided that the stimulus luminance is adequately selected.

Determination of Normal Values Using an Automated Coagulation Timer for Activated Coagulation Time and its Application in Dogs with Hemophilia

The present study was performed to determine normal values for the Medtronic HemoTec automated activated coagulation time (ACT) analyzer (Medtronic HemoTec Inc, Parker, CO, distributed in Switzerland by Convergenza AG, Vaduz, Liechtenstein), and to evaluate its ability to detect dogs with hemophilia. ACT was measured in 43 healthy dogs presented to the Companion Animal Hospital, University of Bern, Bern, Switzerland, with the Medtronic HemoTec ACT analyzer to determine normal values. The mean ± 2 standard deviations (SDs) of the values obtained was defined as the normal range. ACT was measured 8–10 times on the same day in 6 dogs to determine repeatability. ACT also was measured in 11 dogs with hemophilia and compared with a conventional visual ACT measurement test and with the activated partial thromboplastin time (APTT). ACT values of the 43 dogs used to determine normal values ranged from 66.5 to 97.0 seconds (mean, 79.3 seconds; SD, 7.35 seconds; median, 78.5 seconds). A range of 64–95 seconds (mean ± 2 SDs) was defined as the normal range for the tested device. Repeatability was poor (r= 0.256). ACT values measured with the automated device did not correlate with ACT values measured with a conventional visual test or with APTT. Sensitivity of the test was 90.9%, specificity was 98.0%, and accuracy was 96.7%. Variability in the test results was large and may lead to incorrect results. The automated measurement device was not superior to the conventional visual method in evaluating dogs with hemophilia.

Determination of normal values using an automated coagulation timer for activated coagulation time and its application in dogs with hemophilia.

The present study was performed to determine normal values for the Medtronic HemoTec automated activated coagulation time (ACT) analyzer (Medtronic HemoTec Inc, Parker, CO, distributed in Switzerland by Convergenza AG, Vaduz, Liechtenstein), and to evaluate its ability to detect dogs with hemophilia. ACT was measured in 43 healthy dogs presented to the Companion Animal Hospital, University of Bern, Bern, Switzerland, with the Medtronic HemoTec ACT analyzer to determine normal values. The mean +/- 2 standard deviations (SDs) of the values obtained was defined as the normal range. ACT was measured 8-10 times on the same day in 6 dogs to determine repeatability. ACT also was measured in 11 dogs with hemophilia and compared with a conventional visual ACT measurement test and with the activated partial thromboplastin time (APTT). ACT values of the 43 dogs used to determine normal values ranged from 66.5 to 97.0 seconds (mean, 79.3 seconds; SD, 7.35 seconds; median, 78.5 seconds). A range of 64-95 seconds (mean +/- 2 SDs) was defined as the normal range for the tested device. Repeatability was poor (r = 0.256). ACT values measured with the automated device did not correlate with ACT values measured with a conventional visual test or with APTT Sensitivity of the test was 90.9%, specificity was 98.0%, and accuracy was 96.7%. Variability in the test results was large and may lead to incorrect results. The automated measurement device was not superior to the conventional visual method in evaluating dogs with hemophilia.

Checkerboard visual evoked response in evaluation and management of pituitary tumors

As a routine part of the evaluation of patients with pituitary tumor, visual evoked responses (VERs) to checkerboard pattern reversal were recorded from 83 patients with tomographically documented pituitary tumor. VER tests were correlated with examinations of visual acuity, color perception, and visual fields and with computerized tomographic scan evidence of suprasellar extension of the tumor. The purpose of the VER recording was to determine the presence of visual system compression by the tumor and thus contribute to the decision of whether surgery was necessary. Each of the patients who had suprasellar extension of the tumor sufficient to produce a visual field abnormality also had an abnormal VER. In addition, some patients with suprasellar extension had normal visual fields but abnormal visual evoked responses. Thus, the VER provided earlier evidence of suprasellar extension causing visual system compromise than did conventional visual tests. (Neurosurgery, 5: 553-558, 1979)

Checkerboard visual evoked response in evaluation and management of pituitary tumors.

As a routine part of the evaluation of patients with pituitary tumor, visual evoked responses (VERs) to checkerboard pattern reversal were recorded from 83 patients with tomographically documented pituitary tumor. VER tests were correlated with examinations of visual acuity, color perception, and visual fields and with computerized tomographic scan evidence of suprasellar extension of the tumor. The purpose of the VER recording was to determine the presence of visual system compression by the tumor and thus contribute to the decision of whether surgery was necessary. Each of the patients who had suprasellar extension of the tumor sufficient to produce a visual field abnormality also had an abnormal VER. In addition, some patients with suprasellar extension had normal visual fields but abnormal visual evoked responses. Thus, the VER provided earlier evidence of suprasellar extension causing visual system compromise than did conventional visual tests.