CS代写 PSY 4036 Week 5: Aging and Central-Vision Loss

PSY 4036 Week 5: Aging and Central-Vision Loss

Week 5: Aging Vision and Central-Vision Loss
Age-related changes in normal vision.

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Age-related macular degeneration (AMD)
Impact of central-vision loss.
What it’s like to lose your central vision.

People in the United States
Over 65 Years Old
Year Percentage of
Population Number of People
(millions)
2018 16% 52
(projected) 20% 73

Age-Related Changes
in Normal Vision
Presbyopia Reduced range of accommodation, results in reduced ability to focus and the need for bifocals.
Reduced Range of Pupil Size Harder to see in dim illumination with small pupils.
Sub-Clinical Cataract Increasing glare effects, especially at night.
Slower Light & Dark Adaptation Takes more time to adjust to changes in illumination.
Acuity, Contrast Sensitivity & Field To be discussed in class.
Reduced Stereoacuity Impact on 3D depth perception

Haegerstrom-Portnoy,Schneck & Brabyn (1999): “Seeing into Old age: Vision Function Beyond Acuity.”

Purpose: To provide a comprehensive description of vision function beyond acuity in older individuals.
Longitudinal study in , California
Sample of 900 individuals between the ages of 58 and 102 years (mean 75.5)
Battery of vision tests including acuity chart, Pelli-Robson chart, and SKILL card.

Bailey- Contrast Acuity Chart

Average Acuity Values Comparing Ages 55 and 95 Years
Test Type Luminance Contrast Age 55 Age 95
Eye Clinic High High 20/20 20/40
Low Contrast Acuity Chart High Low 20/30 20/130
SKILL Low Low 20/60 20/200

Summary Results from the Study

Conclusions
Healthy eyes show visual impairment in old age. Standard acuity and field measurements underestimate these impairments.
Deficits show up in low luminance, at low contrast, in glare, when there are concurrent attentional demands, and in stereo depth.
Impaired vision increases risk of falls and also fear of falling.
Coexisting health conditions compound these difficulties.

Human Retina

Treatment of AMD
Nutritional (vitamins)
Age-Related Eye Disease Study (AREDS)
High-dose supplements of some antioxidants slows progression of AMD.
Intravitreal anti-VEGF injections
VEGF = Vascular Endothelial Growth Factor
Drugs injected into the eye inhibit the growth of destructive blood vessels.
Study demonstrating acuity improvement:  Rosenfeld, P. J., et al. (2006). “Ranibizumab for neovascular age-related macular degeneration.” N Engl J Med 355(14): 1419-1431, Fig. 2A.
Regular physical activity vs. sedentary lifestyle is associated with  reduced odds of onset of AMD and also progression to advanced AMD
Stem Cells
Use of human embryonic stem cells to grow a thin layer of RPE cells
Da Cruz et al. (2018). Phase 1 clinical study of an embryonic stem cell–derived retinal pigment epithelium patch in age-related macular degeneration. Nature Biotechnology.

At least 50 genes involved in AMD
Retinal implants: restore light sensitivity in damaged central vision ( )

Lucentis Treatment for Wet AMD

Rosenfeld, P. J., et al. (2006). “Ranibizumab for neovascular age-related macular degeneration.” N Engl J Med 355(14): 1419-1431, Fig. 2A.

Amsler Grid

Vision with AMD

Fixation Stability
Normal retina
Impaired retina
Microperimetry – MP1

Some Perceptual Consequences of Central-Vision Loss
Formation of a Preferred Retinal Location (PRL) and its use in fixation
Lack of perceptual awareness of the central scotoma
Reduced acuity and the need for magnification
Impact on mobility?

(Smith-Kettlewell Institute
Low Luminance/Low Contrast)

No Slide Title

SKILL CARD
(Smith-Kettlewell Institute
Low Luminance/Low Contrast)

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