Correlation of spatial contrast sensitivity and visual fields in glaucoma

Association between contrast sensitivity function and structural damage in primary open-angle glaucoma

AIMS

To evaluate the association between contrast sensitivity function (CSF) and glaucomatous structural damage in primary open-angle glaucoma (POAG).

METHODS

A cross-sectional study was performed with 103 patients (103 eyes) aged 25-50 years who had POAG without any other ocular disease. CSF measurements were obtained by the quick CSF method, a novel active learning algorithm that covers 19 spatial frequencies and 128 contrast levels. The peripapillary retinal nerve fibre layer (pRNFL), macular ganglion cell complex (mGCC), radial peripapillary capillary (RPC) and macular vasculature were measured by optical coherence tomography and angiography. Correlation and regression analyses were used to assess the association of area under log CSF (AULCSF), CSF acuity and contrast sensitivities at multiple spatial frequencies with structural parameters.

RESULTS

AULCSF and CSF acuity were positively associated with pRNFL thickness, RPC density, mGCC thickness and superficial macular vessel density (p<0.05). Those parameters were also significantly associated with contrast sensitivity at 1, 1.5, 3, 6, 12, 18 cycles per degree spatial frequencies (p<0.05) and, the lower the spatial frequency, the higher the correlation coefficient. RPC density (p=0.035, p=0.023) and mGCC thickness (p=0.002, p=0.011) had significant predictive value for contrast sensitivity at 1 and 1.5 cycles per degree, with adjusted R 2 of 0.346 and 0.343, respectively.

CONCLUSIONS

Full spatial frequency contrast sensitivity impairment, most notably at low spatial frequencies, is a characteristic change in POAG. Contrast sensitivity is a potential functional endpoint for the measurement of glaucoma severity.

Visual function tests for glaucoma practice - What is relevant?

Glaucoma represents one of the most important ocular diseases causing irreversible ganglion cell death. It is one of the most common causes of visual impairment and morbidity in the elderly population. There are various tests for measuring visual function in glaucoma. While visual field remains the undisputed method for screening, diagnosis, and monitoring disease progression, other tests have been studied for their utility in glaucoma practice. This review discusses some of the commonly used tests of visual function that can be routinely used in clinics for glaucoma management. Among the various modalities of testing visual function in glaucoma, this review highlights the tests that are most clinically relevant.

Association of Structural and Functional Measures With Contrast Sensitivity in Glaucoma

PURPOSE

To test the hypothesis that structural and functional measures predict contrast sensitivity (CS) outcomes in glaucomatous eyes.

DESIGN

Cross-sectional prospective study.

METHODS

One hundred five eyes of 65 patients who underwent macular spectral-domain optical coherence tomography imaging, 24-2 standard achromatic visual fields (VF), and CS measurement on the same day were enrolled. Association of CS at 4 spatial frequencies (3, 6, 12, and 18 cycles per degree, cpd) with structural and functional outcomes was explored with correlation and regression analyses.

RESULTS

The median (IQR) 24-2 visual field mean deviation was -7.6 (-11.1 to -3.0). Significant correlations were found between CS at 6 cpd and ganglion cell/inner plexiform layer thickness at inferotemporal and inferonasal macular sectors (ρ = 0.222, P = .023 and ρ = 0.209, P = .032, respectively). CS at 6 cpd demonstrated higher correlations with full macular thickness measurements, the strongest of which was with the central macular thickness in the superior 6 × 3-degree region (ρ = 0.311, P = .001). Contrast sensitivity at 6 cpd also had the strongest correlation with mean deviation of the 4 central VF points (ρ = -0.420; P < .001). There was a significant correlation between logMAR visual acuity and contrast sensitivity at 6, 12, and 18 cpd (ρ = -0.306, ρ = -0.348 and ρ = -0.241, P < .013, respectively).

CONCLUSIONS

Structural and functional measures showed a fair relationship with contrast sensitivity. This association was most prominent between full-thickness macular measures or central VF parameters and CS at 6 cpd. Contrast sensitivity was not a reliable surrogate for glaucoma severity in this cross-sectional study.

The discovery of the Flammer syndrome: a historical and personal perspective

This review describes the clinical and basic research that led to the description of Flammer syndrome. It is narrated from a personal perspective. This research was initiated by the observation of an increased long-term fluctuation of visual fields in a subgroup of glaucoma patients. As these patients had strikingly cold hands, peripheral blood flow was tested with a capillary microscopy, and vasospastic syndrome (VS) was diagnosed. Further studies on these patients revealed frequently weakened autoregulation of ocular blood flow and increased flow resistivity in retroocular vessels. Their retinal vessels were more rigid and irregular and responded less to flickering light. Holistic investigation demonstrated low blood pressure, silent myocardial ischaemia, altered beat-to-beat variation, altered gene expression in the lymphocytes, slightly increased plasma endothelin level and increased systemic oxidative stress. This combination of signs and symptoms was better described by the term primary vascular dysregulation (PVD) than by VS. Subsequent studies showed additional symptoms frequently related to PVD, such as low body mass index, cold extremities combined with slightly increased core temperature, prolonged sleep onset time, reduced feelings of thirst, increased sensitivity to smell and also for certain drugs and increased retinal venous pressure. To better characterise this entire syndrome, the term Flammer syndrome (FS) was introduced. Most subjects with FS were healthy. Nevertheless, FS seemed to increase the risk for certain eye diseases, particularly in younger patients. This included normal-tension glaucoma, anterior ischaemic optic neuropathy, retinal vein occlusions, Susac syndrome and central serous chorioretinopathy. Hereditary diseases, such as Leber’s optic neuropathy or retinitis pigmentosa, were also associated with FS, and FS symptoms and sings occurred more frequent in patients with multiple sclerosis or with acute hearing loss. Further research should lead to a more concise definition of FS, a precise diagnosis and tools for recognizing people at risk for associated diseases. This may ultimately lead to more efficient and more personalised treatment.

Evaluation of Contrast Sensitivity, Chromatic Vision, and Reading Ability in Patients with Primary Open Angle Glaucoma

Purpose. To compare contrast sensitivity, acquired color vision deficiency, and reading ability in patients with glaucoma at different stages of the disease and to establish correlations between visual field parameters and visual function scores. Methods. This prospective cross-sectional study included 121 glaucoma patients. Subjects with a diagnosis of chronic open angle glaucoma were recruited and classified according to Hodapp-Parrish-Anderson criteria. Patients with severe visual field defects were excluded because they were older, which could bias the interpretation of visual function tests. Contrast sensitivity was measured using the Pelli-Robson Chart and the CSV1000E test. Chromatic vision was evaluated using the Farnsworth-panel D15 and the L'Anthony D15 tests of Vision Color Recorder software. Reading ability was measured using Radner-Vissum test. Results. Contrast sensitivity (with photopic and mesopic luminance with glare) differed significantly between patients with early and moderate visual field defects (p < 0.05). Reading ability scores and results of the chromatic vision tests did not differ significantly between the two groups. Significant and moderate Spearman correlations between visual field indexes and contrast sensitivity tests were detected. Conclusions. Contrast sensitivity was significantly worse in patients with moderate glaucoma compared to those with early-stage glaucoma. Evaluation of visual function in clinical practice provides important information to address a glaucoma patient's vision complaints.

Retinal sensitivity in healthy Indians using microperimeter

Aims:

To establish the retinal sensitivity values in healthy Indians using microperimeter.

Materials and Methods:

In this prospective study, 144 healthy volunteers were included. All the participants underwent a comprehensive ophthalmic examination including contrast sensitivity. Microperimetry was performed in the central 20° of the macula using 76 stimulus points to assess the retinal sensitivity, and the fixation characteristics in the study population were assessed.

Results:

The mean age of the study sample was 43.08 ± 10.85 years (range: 25-69). Mean retinal sensitivity was 18.26 ± 0.99 dB. Males had significantly increased retinal sensitivity (18.34 vs. 18.17 dB, P = 0.03). The linear regression analysis revealed a 0.04 dB per year age-related decline in mean retinal sensitivity. Contrast sensitivity was significantly correlated with the mean retinal sensitivity (r = 0.432, P < 0.001). Fixation stability in the central 2° and 4° were 69% and 89%, respectively.

Conclusion:

Microperimeter is an ideal tool to assess the retinal sensitivity and the fixation behavior. These normative values could help in drawing a meaningful conclusion in various retinal pathologies.

Differential up-regulation of Vesl-1/Homer 1 protein isoforms associated with decline in visual performance in a preclinical glaucoma model

Glaucoma is a multifactorial progressive ocular pathology, clinically presenting with damage to the retina and optic nerve, ultimately leading to blindness. Retinal ganglion cell loss in glaucoma ultimately results in vision loss. Vesl/Homer proteins are scaffolding proteins that are critical for maintaining synaptic integrity by clustering, organizing and functionally regulating synaptic proteins. Current anti-glaucoma therapies target IOP as the sole modifiable clinical parameters. Long-term pharmacotherapy and surgical treatment do not prevent gradual visual field loss as the disease progresses, highlighting the need for new complementary, alternative and comprehensive treatment approaches. Vesl/Homer expression was measured in the retinae of DBA/2J mice, a preclinical genetic glaucoma model with spontaneous mutations resulting in a phenotype reminiscent of chronic human pigmentary glaucoma. Vesl/Homer proteins were differentially expressed in the aged, glaucomatous DBA/2J retina, both at the transcriptional and translational level. Immunoreactivity for the long Vesl-1L/Homer 1c isoform, but not of the immediate early gene product Vesl-1S/Homer 1a was increased in the synaptic layers of the retina. This increased protein level of Vesl-1L/Homer 1c was correlated with phenotypes of increased disease severity and a decrease in visual performance. The increased expression of Vesl-1L/Homer 1c in the glaucomatous retina likely results in increased intracellular Ca(2+) release through enhancement of synaptic coupling. The ensuing Ca(2+) toxicity may thus activate neurodegenerative pathways and lead to the progressive loss of synaptic function in glaucoma. Our data suggest that higher levels of Vesl-1L/Homer 1c generate a more severe disease phenotype and may represent a viable target for therapy development.

Quantification of deficits in spatial visual function of mouse models for glaucoma

PURPOSE

DBA/2J mice are a standard preclinical glaucoma model, which spontaneously developed mutations resulting in chronic age-related pigmentary glaucoma. The goals of this study were to identify the degree of visual impairment in DBA/2J mice before and after disease onset by quantifying the optokinetic reflex responses and to compare them to the less-researched strain of DBA/2NHsd mice.

METHODS

Visual performance was measured in healthy, nonglaucomatous, and glaucomatous male DBA/2NHsd or DBA/2J mice using a visuospatial testing box. The optokinetic reflex resulting in optomotor head tracking was manually detected. Measured threshold levels equate to the maximum contrast or spatial frequency the mouse responds to. Intraocular pressure (IOP) was measured by applanation tonometry.

RESULTS

IOP increased with age in both DBA/2J and DBA/2NHsd mice and was not different between the two substrains. Both visual acuity and ability to detect contrast decreased significantly, and similarly with age in both substrains. However, DBA/2NHsd had poorer visual acuity even at a younger age compared to age-matched DBA/2J mice.

CONCLUSIONS

Both DBA/2J and DBA/2NHsd mice show a progressive glaucomatous phenotype of age-related increases in IOP and loss of visual acuity and contrast sensitivity when compared to other inbred or outbred strains. Given the similar increases in IOP and contrast sensitivity threshold and loss of visual acuity between these two DBA/2 substrains, we also conclude that DBA/2NHsd mice are a suitable alternative model for pigmentary glaucoma.

Relationship between visual field loss and contrast threshold elevation in glaucoma

BACKGROUND

There is a considerable body of literature which indicates that contrast thresholds for the detection of sinusoidal grating patterns are abnormally high in glaucoma, though just how these elevations are related to the location of visual field loss remains unknown. Our aim, therefore, has been to determine the relationship between contrast threshold elevation and visual field loss in corresponding regions of the peripheral visual field in glaucoma patients.

METHODS

Contrast thresholds were measured in arcuate regions of the superior, inferior, nasal and temporal visual field in response to laser interference fringes presented in the Maxwellian view. The display consisted of vertical green stationary laser interference fringes of spatial frequency 1.0 c deg(-1) which appeared in a rotatable viewing area in the form of a truncated quadrant extending from 10 to 20 degrees from fixation which was marked with a central fixation light. Results were obtained from 36 normal control subjects in order to provide a normal reference for 21 glaucoma patients and 5 OHT (ocular hypertensive) patients for whom full clinical data, including Friedmann visual fields, had been obtained.

RESULTS

Abnormally high contrast thresholds were identified in 20 out of 21 glaucoma patients and in 2 out of 5 OHT patients when compared with the 95% upper prediction limit for normal values from one eye of the 36 normal age-matched control subjects. Additionally, inter-ocular differences in contrast threshold were also abnormally high in 18 out of 20 glaucoma patients who had vision in both eyes compared with the 95% upper prediction limit. Correspondence between abnormally high contrast thresholds and visual field loss in the truncated quadrants was significant in 5 patients, borderline in 4 patients and absent in 9 patients.

CONCLUSION

While the glaucoma patients tested in our study invariably had abnormally high contrast thresholds in one or more of the truncated quadrants in at least one eye, reasonable correspondence with the location of the visual field loss only occurred in half the patients studied. Hence, while contrast threshold elevations are indicative of glaucomatous damage to vision, they are providing a different assessment of visual function from conventional visual field tests.

Beyond visual acuity: new and complementary tests of visual function

Visual acuity is an essential component of the routine ophthalmic examination and the most common measure of visual function. There is increasing recognition, however, of the need to evaluate visual function beyond the limited extent afforded by visual acuity. The primary objective of this article is to introduce a variety of new and lesser-used techniques for measuring visual function that complement visual acuity assessment, each of which has been shown to detect visual dysfunction in patients with normal visual acuity.