Effect of Grouping on Lightness
Psychology 4036:
Perceptual Issues in Visual Impairment
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Week 1: Introduction
List of Book Chapters
Solomon, A. Far from the Tree: Parents, Children and the Search for Identity. Scribner, 2012.
I Son 1
II Deaf 49
III Dwarfs 115
IV Down Syndrome 169
V Autism 221
VI Schizophrenia 295
VII Disability 355
VIII Prodigies 405
IX Rape 477
X Crime 537
XI Transgender 599
XII Father 677
Three Approaches for Dealing with Low Vision
Medical Model
Rehabilitation
Social Justice and Civil Rights
DEI (Diversity, Equity and Inclusion)
IDEA (Inclusion, Diversity, Equity and Accessibility)
Relevance to Daily Life
Disability as a form of diversity.
Your personal experience with disability.
Think inclusively.
Vision Terms
3 Categories of Sight – Normal, Low Vision, Blind
Terminology:
• Visual Disorder: Any deviation from normal in the status of the eyes, including diseases or chronic conditions.
• Visual Impairment: Consequences of an eye disease or disorder on a measure of visual function such as acuity or contrast sensitivity.
• Visual Disability: Restrictions on normal activities of daily life resulting from visual impairment, such as reading or mobility.
• Visual Handicap: A cultural, economic, or social disadvantage for a person resulting from visual impairment.
Definitions of Low Vision
Any chronic visual impairment, not correctable by lenses, that affects everyday function.
Inability to read newsprint (e.g., Times Roman 10pt) at a typical reading distance (40 cm, 16 inches) with best refractive correction.
Visual acuity of less than 20/60 or a visual field of less than 20 degrees in the better eye with best possible correction (ICD-10).
Acuity boundary shifting to 20/40.
Global Estimates of Visual Impairment by Acuity (2015)
Of Visual Impairment # in Millions % of World Population
20/40 – 20/60 188.5 2.57
Moderate to Severe:
20/60 – 20/400 217 2.95
Worse than 20/400 36 0.48
Total 441.5 ~ 6
World population 7.33 billion
Based on Presenting visual acuities.
Percentage female: ~ 55%
Source: Bourne, R.R.A. et al. (2017). Magnitude, temporal trends, and projections of the global prevalence of blindness and distance and near vision impairment: a systematic review and meta-analysis. The Lancet Global Health, 5(9): e888-e897. doi:10.1016/S2214-109X(17)30293-0
U.S. Estimates of Visual Impairment
2017 and 2050
Category of
Visual Impairment Prevalence in
Millions (2017) Prevalence in Millions
Worse than
20/40 5.7 9.6
(legal blindness) 1.3 2.3
U.S. population in 2017 = 325 M; in 2050 = 438 M ( Center).
Categories based on Best-Corrected Visual Acuity.
Annual Incidence approx. 12.4% of the prevalence.
Source: Chan, T., Friedman, D. S., Bradley, C., & Massof, R. (2017). Estimates of incidence and prevalence of visual impairment, low vision, and blindness in the united states. JAMA Ophthalmology. doi:10.1001/jamaophthalmol.2017.4655
Percentage Prevalence of Causes of Severe Low Vision Worldwide and in the US
< 20/400 U.S.A.
Legally Blind
AMD 5.9 47.2
Cataract 35.1 12.6
Retinopathy 1.1 5.9
Glaucoma 8.5 9.4
Other 29.1 25.2
Refractive
Error 20.3 NA
Age Distribution
of Low Vision & Blindness
Low Vision
Percentage of U.S. Population by Age Category
Low Vision: the best-corrected visual acuity less than 6/12 (<20/40) in the better-seeing eye (excluding those who were categorized as being blind by the U.S. definition).
Blindness: the best-corrected visual acuity of 6/60 or worse (=20/200) in the better-seeing eye.
Low Vision is defined as the best-corrected visual acuity less than 6/12 (‹20/40) in the better-seeing eye (excluding those who were categorized as being blind by the U.S. definition.)
Blindness as defined by the U.S. definition is the best-corrected visual acuity of 6/60 or worse (=20/200) in the better-seeing eye. Blindness is defined by U.S. definition 20/200 best-corrected visual acuity in the better-seeing eye and the World Health Organization standard of < 20/400.
Mr. Magoo “Watching” TV
Time-Tradeoff Method for Estimating Quality of Life
Suppose your life expectancy is 50 more years.
Imagine losing all of your sight today and becoming totally blind for the remaining 50 years of your life.
How many years of life N would you be willing to trade away to retain your current normal, healthy vision?
Your estimate of Quality Of Life (QOL) with total blindness is (50-N)/50.
Example. If you are willing to trade away 20 years, QOL = 30/50 = .60; your estimate of QOL with blindness is 60% of QOL with healthy sight.
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