Visual changes with aging
Pablo Artal in Handbook of Visual Optics, 2017
Contrast sensitivity is typically determined by measuring the minimum contrast required to detect sinusoidally modulated gratings presented at a range of spatial frequencies to generate the contrast sensitivity function (CSF). The form of the CSF involves both optical and neural factors. Optically, retinal image quality is determined by the form of the modulation-transfer function, which shows an age-dependent reduction at high spatial frequencies (Artal et al. 1993), while at a neural level, the CSF is believed to reflect the sensitivity of multiple visual channels, which are selective to different bands of spatial frequencies (Campbell and Robson 1968). Alternative methods of assessing contrast sensitivity include chart-based techniques, which provide a measure of contrast thresholds at specific spatial frequencies across the CSF. For example, the Pelli–Robson chart includes large letters that decrease in contrast rather than size down the chart and measures contrast sensitivity at low spatial frequencies (Mantyjarvi and Laitinen 2001), while the Melbourne Edge Test assesses sensitivity closer to the peak of the CSF (Verbaken and Johnston 1986). An assessment with these chart-based contrast sensitivity charts in combination with a measure of visual acuity is believed to provide a good clinical compromise for describing the form of an individual’s CSF (Woods and Wood 1995).
Psychophysical and Electrophysiological Testing in Glaucoma
Neil T. Choplin, Carlo E. Traverso in Atlas of Glaucoma, 2014
A variety of different contrast sensitivity tests have also been reported to show sensitivity losses in glaucomatous eyes.35 Although this procedure seems promising and can be easily incorporated into a standard clinical examination, the types of contrast sensitivity loss that have been found for glaucoma can also be found for a number of other methodological variations (pupil size changes, blur, refractive error, media opacities, lighting conditions, etc.) and ocular and neurologic disease states (retinal, optic nerve, chiasmal, and post-chiasmal deficits). As a consequence, contrast sensitivity testing is not a particularly useful clinical tool for detection, differential diagnosis, or monitoring of glaucoma or for evaluation of treatment efficacy.
Clinical Examination in Neuro-Ophthalmology
Vivek Lal in A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
Diseases of the optic nerve affect the contrast sensitivity and hence its measurement will help to access the visual dysfunction and quality of vision in such patients. During routine eye examination, the ability to recognize low contrast objects may be missed as Snellen acuity charts are of high contrast optotypes. Specially designed charts including Pelli-Robson chart consist of rows of optotypes of fixed size with decreasing contrast (Figure 1.16). The patient reads in a manner similar to visual acuity testing and the maximum contrast at which the letters can be detected is measured. Another method is using the Vistech chart, which has rows of circular targets with different special frequency and sinusoidal gratings.2,6
Intravitreous delivery of melatonin affects the retinal neuron survival and visual signal transmission: in vivo and ex vivo study
Published in Drug Delivery, 2020
Ye Tao, Bang Hu, Zhao Ma, Haijun Li, Enming Du, Gang Wang, Biao Xing, Jie Ma, Zongming Song
Three weeks after intravitreal delivery, the optokinetic behavioral tests were performed to analyze the visual function of animals. A two-alternative forced-choice paradigm was used to analyze the optomotor responses to moving sine wave gratings (McGill et al., 2012). Mouse was placed on a pedestal situated in the center of a square array (OptoMotry CerebralMechanics, Lethbridge, AB, Canada). Stimulus gratings were projected on the wall of the machine and they turned randomly in clockwise or counter-clockwise direction. Mice reflexively track the rotating virtual cylinders by moving their head in the direction of rotating gratings. An infrared television camera located at the top of the testing machine allowed the examiner to decide the direction of animal’s optomotor response. The initial stimulus was set as 0.200 cyc/deg sinusoidal pattern at a fixed 100% contrast. The contrast sensitivity was measured at spatial frequencies ranging between 0.014 and 0.511 cyc/deg.
Effect of Vitamin D Deficiency on Contrast Sensitivity Function
Published in Current Eye Research, 2020
Retinal diseases are one of the significant causes of contrast sensitivity dysfunction. Alahmadi et al. showed that CS decreases at all frequencies in patients with retinal dystrophy, more prominent at high spatial frequencies.18 Similarly, there was a decrease in all spatial frequencies in our study; however, it was statistically significant at 6, 12, 18 cpd. Puell et al. compared macular inner retinal layer thickness and photopic and mesopic CS in healthy subjects. They found that there was a negative correlation between MT and photopic CS in young people, and that there was a positive correlation between MT and photopic CS in the elderly.19 In our study, patients with vit D deficiency had higher MT and lower CS compared to the control group.
Clinical procedures in primary eye care, 5th edition
Published in Clinical and Experimental Optometry, 2021
The following chapter of assessment of visual function examines in detail the theory and method of measuring distance and near visual acuity across a series of visual acuity charts for adults and children. Contrast sensitivity function is described, and the procedure outlined for clinical testing. A brief genetic description of colour vision anomalies is discussed followed by procedures for routine colour vision testing in clinic for both congenital and acquired colour vision deficiencies. The chapter ends with a detailed description of visual pathways and the fundamentals of perimetry. The common perimetric testing strategies for screening and threshold measures in a clinical setting are discussed with a guide to interpretation.
Related Knowledge Centers
- Color
- Glaucoma
- Lateral Inhibition
- Photoreceptor Cell
- Retina
- Visual Acuity
- Retinal Ganglion Cell
- Receptive Field
- Weber–Fechner Law
- Image