Vision Loss and V1

91 Low Vision

Learning Objectives

Know the definition of low vision and legal blindness.

Know the prevalence of low vision.

Being able to explain why we are still expecting more low vision people in our society given that we have better and more treatments for many eye diseases.

Low vision is defined as the visual acuity in one’s best eye being worse than 20/60 even with correction. Low vision occurs in 2% of the worldwide population (around 124 million people). The World Health Organization states that at least 2.2 billion people globally experience some form of near or distance vision impairment. Half of these cases, amounting to approximately 1 billion, could have been prevented or remain unaddressed.


This graph shows an exponential trend between blindness and age.
Figure 9.1.1. The global prevalence of blindness and low vision (moderate to severe visual impairment) in women. (PubMed Central, Figure 2, CC BY-NC, No Modifications.)


For one to be constituted as legally blind, the visual acuity of their best eye must be worse than 20/200 (or only 20 deg. visual field). 0.6% of the worldwide population is blind.

With the youngest of the baby boomers hitting 65 by 2029, the number of people with visual impairment or blindness in the United States is expected to double to more than 8 million by 2050, according to projections based on the most recent census data and from studies funded by the National Eye Institute (part of the National Institutes of Health).

Despite significant advancements in treatments and interventions for vision impairment, the World Health Organization (WHO) states that the prevalence of low vision and blindness is expected to rise due to a combination of demographic changes and health trends. The global increase in population, the aging demographic, and the rising prevalence of chronic conditions such as diabetes, which significantly contribute to vision problems, are attributed to this expected growth. The aging demographic is especially concerning as vision impairment and blindness predominantly affect those over the age of 50 years. With life expectancy on the rise, the segment of the population at risk for age-related eye conditions, including cataracts, glaucoma, and macular degeneration, is expanding.

The data tells us that we should prepare for the surge in visual impairment by implementing further nationwide screening in order to identify people with correctable vision problems and early signs of eye disease. Early detection and intervention could be one of the best options in our attempt to avoid a significant proportion of avoidable vision loss (Fig.9.1.1). Once low vision or blindness occur, they are usually permanent, making early detection and intervention one of the top priorities in our attempt to avoid a significant proportion of avoidable vision loss.


Fig.9.1.1. The Snellen Chart. The typical Snellen chart, originally developed by Dutch ophthalmologist Herman Snellen in 1862, used in most optometry offices to measure visual acuity. The leftmost image displays how the Snellen Chart appears to a typically sighted person. The three images to the right correspond roughly to the visual experiences of those with various levels of low vision or blindness. (Provided by: Wikipedia. License: CC-BY-SA 4.0. )



Cheryl Olman PSY 3031 Detailed Outline
Provided by: University of Minnesota
Download for free at
License of original source: CC Attribution 4.0
Adapted by: Mckenzie RobertsCONTENT SHARED PREVIOUSLY
National Eye Institute, “Visual impairment, blindness cases in U.S. expected to double by 2050”
License: PDM
Adapted by: Mckenzie Roberts and Connor Schreck


Varma, R et al, “Visual impairment and blindness in adults in the United States: Demographic and Geographic Variations from 2015 to 2050,” JAMA Ophthalmology, DOI:10.1001/jamaophthalmol.2016.1284 Pubmed


Icon for the Creative Commons Attribution 4.0 International License

Introduction to Sensation and Perception Copyright © 2022 by Students of PSY 3031 and Edited by Dr. Cheryl Olman is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

Share This Book