Low vision is an uncorrectable loss of vision that interferes with daily activities. The World Health Organization 's (WHO 2010) criteria for low vision: Low vision is a best-corrected visual acuity lower than 0.5 logMAR (Snellen 6/18) but equal to or more than 1.3 logMAR (3/60) in the better eye, or visual field corresponding to less than 20 degrees in the better eye.
Blindness is defined as a best-corrected visual acuity lower than 1.3 logMAR or a visual field no more than10 degrees in the better eye with best correction.
Age-related macular degeneration (AMD) is the most common cause of blindness in white people, while glaucoma and diabetic retinopathy are the leading causes in coloured people. (Congdon et al, 2004)
Low Vision Assessment: …show more content…
In a LogMAR (logarithm of the minimum angle of resolution) test the distance between different sizes is the same throughout the test, to test good and poor vision. The directional E, Landolt rings can be used when letters cannot be read. Matching tests such as the LH symbols are mainly used to test vision of young children. (Keeffe, 2004)
LogMAR chart LH cards in testingvision for children
Distance visual acuity should be measured with a multiple pinhole for people with low vision.
Near vision is tested using the LogMAR format. If not possible, letters or symbols can be used. The smallest print read and the distance should be recorded. Magnification is needed to improve the reading distance.
-Contrast sensitivity(CS) refers to the differentiation between an object and its background and represents the lowest contrast level that can be detected for a given size target against a certain background. The commonly used tests are the Vision Contrast Test System (VCTS) and Pelli-Robson charts. The VCTS charts are better in that they measure CS at multiple spatial frequencies; thus, they are used routinely in clinics and research. (Ginsburg,
Blindness is defined as a best-corrected visual acuity lower than 1.3 logMAR or a visual field no more than10 degrees in the better eye with best correction.
Age-related macular degeneration (AMD) is the most common cause of blindness in white people, while glaucoma and diabetic retinopathy are the leading causes in coloured people. (Congdon et al, 2004)
Low Vision Assessment: …show more content…
In a LogMAR (logarithm of the minimum angle of resolution) test the distance between different sizes is the same throughout the test, to test good and poor vision. The directional E, Landolt rings can be used when letters cannot be read. Matching tests such as the LH symbols are mainly used to test vision of young children. (Keeffe, 2004)
LogMAR chart LH cards in testingvision for children
Distance visual acuity should be measured with a multiple pinhole for people with low vision.
Near vision is tested using the LogMAR format. If not possible, letters or symbols can be used. The smallest print read and the distance should be recorded. Magnification is needed to improve the reading distance.
-Contrast sensitivity(CS) refers to the differentiation between an object and its background and represents the lowest contrast level that can be detected for a given size target against a certain background. The commonly used tests are the Vision Contrast Test System (VCTS) and Pelli-Robson charts. The VCTS charts are better in that they measure CS at multiple spatial frequencies; thus, they are used routinely in clinics and research. (Ginsburg,