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I. Assessing children with low vision
A. Retinopathy of Prematurity (ROP)
1. Characteristics: birth weight, gestational age
2. Classification Schemes
a. Stages 1 – 5
b. Zones of retina involved (1-3)
c. Rush and Plus disease
3. National Eye Institute Clinical Trials
a. Current treatment and standards of care – laser vs. cryotherapy
b. Cryotherapy for Retinopathy of Prematurity (CRYO-ROP)
c. The effects of Light Reduction on Retinopathy of Prematurity (Light-ROP)
d. Supplemental Therapeutic Oxygen for Prethreshold Retinopathy of Prematurity
(STOP-ROP) Multi-center Trial
e. Early Treatment for Retinopathy of Prematurity Study (ETROP)
4. Early assessment of visual function
a. Goals are to access standard print and to extend visual reach
b. Specialized testing – visual acuity (Lea cards, Teller cards), contrast,
confrontation fields, trial frame refraction
5. Providing Access to the Visual Environment (PAVE - Corn et. al.)
a. Model program for children from ages 3 to 21 years of age
b. Pre-optical training techniques
c. Visual environmental awareness
d. Visual independence
6. Adaptive Technology
a. Electronic methods of magnification and image enhancement
b. Distance, near, intermediate options
c. Multi-purpose head-borne devices
d. Manipulation of text for reading: scrolling vs. rapid serial visual presentation
7. Partnerships
a. Patient, parents, teachers for the visually impaired, and rehabilitation team
b. Delivering Optimum Vision Education Services (DOVES – Jose et. al.)
c. SeMor (Inde K, Gustaffson J, et. al. – Sweden)
d. Advocacy
II. Assessing adolescents with low vision
A. Ocular albinism (OA) and Oculocutaneous albinism (OCA)
1. Inheritance pattern for OA
a. X-linked (OA1) affects only males
b. autosomal recessive
c. prevalence 1:50,000
2. OCA
a. Type 1 – tyrosinase positive; Type 2 – tryrosinase negative
b. Chediak-Higashi Syndrome – susceptibility to infection and lymphofollicular
malignancy
c. Hermansky-Pudlak Syndrome – bleeding diathesis secondary to platelet
dysfunction
3. Characteristics
a. Nystagmus
b. Iris Transillumination defect
c. Foveal hypoplasia
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d. Significant refractive error including astigmatism
e. Blonde fundus with visible choroidal vasculature
f. Variable hypopigmentation
g. abnormal decussation of optic nerve fiber bundle
National Eye Institute Research
a. “AAV-mediated gene correction in retina” (RO3, Feb, 2006)
b. Molecular genetics of mouse model exploring RPE
i. during embryogenesis RPE regulation controls the abundance of
melanasomes
ii. after birth RPE controls melanosome size
iii. goal is to correct error with gene transfer technology
Contrast sensitivity and glare - assessment of overall visual function beyond visual
acuity
a. Charts - Pelli-Robson, Mars, SKILL card, University of Waterloo
b. Deciding between glare complaint versus contrast sensitivity reduction
i. NOIR and wrap-around filters
ii. Wavelength cut-off filters
c. Opaque iris contact lenses for glare control
i. Performance improvement for VA, CSF, nystagmus?
ii. Subjective response
iii. Parameters and material availability
Estimation of magnification for reading
a. Distinction between short-term vs. prolonged tasks
b. Role of accommodation
c. logMAR and equivalent viewing distance methods
d. Doublet vs. diffractive optics
i. Binocularity – half-eyes vs. microscopes
e. Optical magnifier options
i. hand-held and stand
ii. illumination options – halogen, LED
Non-optical accessories to optimize performance
a. lighting
b. typoscope
III. Assessing Adults with Low Vision
A. Retinitis Pigmentosa
1. Characteristics
a. Prevalence about 1 in 3500 in the United States
b. Family of disorders linked to mutations in over 30 different genes
c. Age of onset in early adulthood but can vary from infancy to 30s or 50s
d. Role of RPE65 in rhodopsin formation and the visual cycle
2. Symptoms
a. Early onset nyctalopia (night blindness)
b. Mid-peripheral field loss initially
c. Gradual constriction of visual fields
d. May lead to complete loss of vision
e. Prognosis related to visual field diameter and VA (Madreperla et. al., 1990)
3. Signs
a. Bony spicules
b. Waxy pallor appearance to optic nerve head
c. Early onset posterior subcapsular cataract
d. Vessel attenuation
4. National Eye Institute Clinical Trials – treatment with Vitamin A
a. Clinical trial of docosahexaneioic acid (DHA) in patients with RP receiving
vitamin A treatment. (Berson EL et. al., 2004)
b. A randomized trial for vitamin A and vitamin E supplementation for RP (Berson
EL et. al., 1993)
5. Visual field enhancement
a. Assessment of visual fields: automated perimetry vs. Goldmann
b. Visual field enhancement devices
i. Minus lenses to create a reverse telescope
ii. Spectacle-mounted reverse telescopes
iii. Fresnel lenses – various designs and strategies
iv. Sector prisms
c. Orientation and mobility training
6 Patient counseling
a. Family planning
b. Vocational rehabilitation and ADA “reasonable accommodations”
c. Resources for advocacy
B. Stargardt’s Juvenile Macular Degeneration
1. Characteristics
a. Most common hereditary macular degeneration (autosomal recessive)
b. Caused by ABCR gene mutation originally discovered using a knockout mouse
model
c. Age of onset between 6 and 15 with gradual vision loss in 20s and 30s
2. Symptoms and signs
a. Decreased visual acuity, abnormal color vision, photophobia
b. Beaten bronze appearance to macula in early stages followed by atrophy
c. Pisciform yellow flecks as part of spectrum including fundus flavimaculatus
3. Research
a. Transgenic mouse model with a mutant form of ELOVL4 gene
b. Fixation patterns and reading rates in eyes with central scotomas from
advanced atrophic age-related macular degeneration and Stargardt disease
(Sunness et. al., 1996)
c. Validity and interpretation of Amsler grid reports (Schuchard et. al., 1993)
4. Central visual field assessment
a. Automated perimetry 10-2 vs. Amsler grid
b. Scanning laser ophthalmoscopy (SLO)
i. Microperimetry
ii. Preferred retinal locus identification
iii. Visual functions and eccentric viewing
5. Distance viewing devices
a. Setting visual goal and determining magnification
b. Balance between magnification and field of view
c. Hand-held telescopes
d. Bioptic telescopic spectacles (BTS)
6. Telescope training - gradual progression in complexity
a. Spotting – line up exit pupil with light source
b. Focusing – pre-focus first
c. Scanning – chalkboard activities
d. Integration and application
7. Bioptic Telescopic Spectacle – prognostic factors
a. Cognitive processing speed
b. Motor coordination
c. Reaction time
d. Visual perceptual skills
8. Driving
a. State regulations and guidelines
b. Training with occupational therapy and driving instructors
c. Certification by Department of Public Safety/Department of Motor
Vehicles
IV. Effectiveness of vision rehabilitation services
A. Meeting objectives – NEI visual function questionnaire
B. Reading performance
C. Role of training
D. Success rates in different clinical settings
V. Summary
A. Clinical research in low vision rehabilitation may lead to more effective treatment and
management of ocular disease.
B. Low vision rehabilitation is an ongoing and dynamic partnership that evolves as the
needs of the patient grows from childhood onwards.
C. Low vision rehabilitation incorporates the latest in diagnostic and therapeutic
technology to maximize quality of life for persons with visual impairment.
D. With increasing life spans, the demand for low vision rehabilitation services will
continue to increase.