Abstract
BackgroundThere 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.MethodsContrast 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° 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.ResultsAbnormally 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.ConclusionWhile 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.
Highlights
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
A total of 26 patients ages 37 to 83 yr were recruited from the Tennent Institute of Ophthalmology, Gartnavel General Hospital. They were diagnosed according to their intra-ocular pressure (IOP) determined by applanation tonometry, the appearance of the optic disc on ophthalmoscopic examination and the extent of visual field loss determined with the Friedmann Visual Field Analyzer Mark II (Clement Clarke International Ltd., London)
Twenty one patients were diagnosed as having glaucoma (Table 1): the most common condition was primary open angle glaucoma (POAG) in which IOP exceeded 22 mmHg on at least 2 occasions before treatment, there was cupping of the optic disc and visual field defects characteristic of glaucoma were present
Summary
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. The pattern of loss which alerts awareness of the disease, is often an arcuate scotoma occurring with approximately equal frequency in the superior or inferior hemifield within 20 degrees of the fovea and with or without a nasal step These losses are generally detected in the clinical environment by visual field tests involving presentation of spots of light within a hemi-spherical dome at various locations within the central visual field. There has been an impetus to develop alternative tests to visual field testing capable of detecting glaucoma at earlier stages One such test is the measurement of contrast sensitivity in response to sinusoidal grating patterns generated by a variety of methods-oscilloscope, TV or computer monitor, printed paper, laser interferometry, or Snellen letters. In the one case in which this was done on a limited scale [17], contrast sensitivity deficits were described as occurring in both the visual hemifield showing no visual loss and the hemifield which did show visual loss
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
