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LOW VISION REHABILITATION
IN PATIENTS WITH RETINAL
DYSTROPHY
Amrit Pokharel
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Dystrophy??
A hereditary, symmetrical, congenital or later appearing, slowly progressive affection, presenting slight intrafamilial variation, and of unknown etiology.
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Dystrophy??
It was suggested that conditions secondary to systemic factors should not be considered dystrophies, but the authors find it somewhat artificial to exclude entities with systemic manifestations from the definition.
Retinitis Pigmentosa has been found to be associated with systemic conditions that are inherited and is called one of the retinal dystrophies
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Retinal Dystrophies
Generalised photoreceptor dystrophies Typical retinitis pigmentosa Atypical retinitis pigmentosa Progressive cone atrophy Leber Congenital Amaurosis Stargardts disease and Fundus
flavimaculatus Bietti corneoretinal crystalline dystrophy Alport syndrome
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Retinal Dystrophies
Generalised photoreceptor dystrophies Familial benign fleck retina Pigmentary paravenous chorioretinal
atrophy Congenital stationary night blindness Congenital monochromatism
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Retinal Dystrophies
Macular Dystrophies Juvenile Best macular dystrophy Multifocal Vitelliform lesions without Best
disease Pattern dystrophy North Carolina macular dystrophy Familial dominant drusen Sorsby pseudoinflammatory dystrophy
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Retinal Dystrophies
Macular Dystrophies Benign concentric annular macular
dystrophy Central areolar choroidal dystrophy Dominant cystoid macular oedema Sjogrens-Larsson syndrome Familial internal limiting membrane
dystrophy
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Goals
Identify patients with visual impairment(s) who might benefit from low vision care and rehabilitation
Evaluate visual functioning of a compromised visual system effectively
Emphasize the need for comprehensive assessment of patients with impaired vision and referral to, and interaction with, other appropriate professionals
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Goals
Maintain and improve the quality of eye and vision care rendered to visually impaired patients
Inform and educate other health care practitioners and the lay public regarding the availability of vision rehabilitation services
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Goals
Increase access for the evaluation and rehabilitative care of individuals with visual impairment(s), thereby improving their quality of life.
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Vision rehabilitation As defined by the American Optometric
Association
the process of treatment and education that helps
individuals who are visually disabled attain maximum function, a sense of well being, a personally satisfying level of independence, and optimum quality of life. Function is maximized by evaluation, diagnosis
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and treatment including, but not limited to, the prescription of optical,
non-optical, electronic and/or other treatments.
The rehabilitation process includes the development of an individual rehabilitation plan
specifying clinical therapy and/or instruction in compensatory approaches.
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Quantifiers of Visual Impairment The ICD 10-ICIDH has employed the
following quantifiers: Visual Acuity
Visual Field
Contrast Sensitivity
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Quantifiers of Visual Impairment The approach is to use functional terms
to classify the type of Visual Field defect.
This approach is a useful way to think of problems the patient may encounter:
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Quantifiers of Visual Impairment …the patient may encounter:
No visual field defect, but a loss of resolution or contrast throughout the entire visual field; general haze or glare
Central visual field defect
Peripheral visual field defect
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For rehabilitation work, must know thing: Visual field defect loss of contrast and
resolution
Central VF defect
Peripheral VF defect
√×√
√
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For the Guideline here on how to rehabilitate the patients with retinal dystrophy,
Low vision instruction, low vision training, low vision therapy, vision rehabilitation theapy and vision rehabiliatation training are synonymous
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CARE PROCESS
Diagnosis of Low Vision Patient History Ocular Examination
Visual Acuity Monitor stability or progression of disease Assess eccentric viewing postures and skills Assess scanning ability( for patients with restricted
field) Assess patient motivation Teach basic concepts and skills( ie to eccentrically
view) relevant to rehabilitation process
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CARE PROCESS
Diagnosis of Low Vision Patient History Ocular Examination
Refraction Use of JND technique
Radical retinoscopy
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CARE PROCESS
Diagnosis of Low Vision Patient History Ocular Examination
Ocular motility and Binocular Vision Assessment
Evaluate for the presence of nystagmus, ocular motility dysfunction( eg poor saccades and pursuits)
Look for strabismus, substandard binocularity, or diplopia
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CARE PROCESS
Diagnosis of Low Vision Patient History Ocular Examination
Ocular motility and Binocular Vision Assessment
Gross assessment of ocular alignment( eg Hirschberg estimation)
Sensorimotor testing( Worth four dot test, red lens test)
Amsler grid test, monocularly versus binocularly to determine eye dominance and the possible need for occlusion
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CARE PROCESS
Diagnosis of Low Vision Patient History Ocular Examination
Ocular motility and Binocular Vision Assessment
Contrast sensitivity , monocularly versus binocularly to determine eye dominance and the possible need for occlusion
Effect of lenses, prisms, or occlusion on visual functioning
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CARE PROCESS
Diagnosis of Low Vision Patient History Ocular Examination
Visual Field Assessment Central vs Peripheral VF defects Confrontation VF testing Amsler or threshold Amsler grid assessment Automated static perimetry Tangent screening Goldmann Bowl perimetry or equivalent kinetic
testing
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CARE PROCESS
Diagnosis of Low Vision Patient History Ocular Examination
Ocular Health Assessment External examination( adnexa, lids, conjunctiva,
iris, lens, and pupillary response) Biomicroscopy( lids, lashes, conjunctiva, tear film,
cornea, anterior chamber, iris, and lenses) Tonometry Central and peripheral fundus examination with
dilation unless containdicatedDilation not to be carried out prior to working with
lenses
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CARE PROCESS
Diagnosis of Low Vision Patient History Ocular Examination Supplemental Testing
Contrast sensitivity testing Glare testing Visually Evoked Potentials (VEP) Electroretinogram( ERG) Electrooculogram( EOG) Colour Vision testing
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CARE PROCESS
Management (Low vision rehabilitation)
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Rehabilitation
The goals discussed earlier are met by; Improving distance, intermediate, or near
vision
Improving print reading ability
Reducing photophobia and/or light-to-dark or dark-to-light adaptation time
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Rehabilitation
The goals discussed earlier are met by; Improving the ability to travel
independently
Improving the ability to perform activities of daily living
Maintaining independence
Understanding the diagnosed vision condition, prognosis,and implications for visual functions
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How to start??
An optometrist should individualize the management plan for each patient while planning a course of therapy.
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How to start??
An optometrist should CONSIDER the following: Degree of VI
Underlying cause( here retinal dystrophy)
Patient’s age and developmental level
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How to start??
An optometrist should CONSIDER the following: Overall health status of the patient
Patient’s adjustment to visual loss
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How to start??
An optometrist should CONSIDER the following: Patient’s expectations and
motivations
Patient’s (cognitive) ability to participate in the rehab
Lens systems and technology available
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Rehabilitation process
Use of devices:
Optical Devices Non-Optical Devices
RGPHOMeS
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Looking at the statistics…
Retin
itis Pigm
ento
sa
Usher
Syn
drom
e
Cone-
rod
dyst
roph
y
Inhe
rited
mac
ular
deg
ener
atio
n
Chorio
retin
al d
egen
erat
ion
. Leb
er con
geni
tal a
mau
rosis
Conge
nita
l sta
tiona
ry n
ight
blin
dnes
s
Retin
osch
esis
Choro
ider
emia
Other
inhe
rited
retin
opat
hies
0
10
20
30
40
40
10 10 10 5 5 5 3 210
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`Presenting complaint Possible rehabilitation options
Difficulty in reading Refraction, lighting, high reading add spectacles, hand held magnifiers, CCTV, large prints/talking books
Difficulty in recognizing faces Refraction, fixation advice/training, lightning
Difficulty in watching TV Refraction, Changing Viewing distance, Fixation advice /training telescopic magnifiers
Difficulty in navigation/mobility
Orientation and mobility training, Refraction, Telescopic magnifiers (for street signs)
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`Presenting complaint Possible rehabilitation options
Difficulty in using computer screens Text enlargement software, Screen reading software, Refraction
Difficulty in kitchen/household tasks Lighting, Contrast advice, Hand magnifiers
Difficulty in shopping Hand magnifiers, Portable lightning, Handheld CCTVs
Difficulty in hobbies(reading, music, gardening, painting)
Refraction, Galilean Telescopes, Text enlargement
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Eccentric viewing
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Eccentric Viewing Eccentric viewing refers to the
technique of observing a scene with the
peripheral retina, by moving the damaged fovea away from the object of interest
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Eccentric Viewing Due to the lower density of
photoreceptors and greater number of photoreceptors per ganglion cell in the peripheral retina, visual acuity will be far worse as that in the
fovea.
This strategy can, however, provide an unobstructed view of the scene
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Retinitis Pigmentosa Usher Syndrome Hallgren’s Syndrome Refsum’s syndrome
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Prognosis: XL- worst prognosis severe Vision loss by 4th
decade
AR or sporadic cases-favourable with retention of CF until 5th decade
AD best prognosis and CF present beyond 5th decade
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ERG in RP Decreased in fERG Early pERG may be normal,
Later gets abnormal Amplitude reduction in the periphery that corresponds to VF defect
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CHARACTERISTICS OF DISEASES
Dark Line in RetinaDecreased Night VisionLoss of Peripheral/Central VisionDecrease in Visual Acuity
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Functional Implications
Peripheral vision lost
Limited visual field
Limited mobility Debilitating glare Extreme
sensitivity of light Eventual
Blindness
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Rehabilitation
Wearing glasses Low vision
devices Magnification and
illumination of objects
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Rehabilitation
Field enhancers are employed since visual field is markedly constricted.
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Rehabilitation
So how is peripheral VF defect management launched?
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Rehabilitation
Consider the goals as given by the AOA and work under the following five areas: Maximized VA Glare and photophobia control Magnification Field enhancement techniques Referrals for additional services
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Rehabilitation
Consider the goals as given by the AOO and work under the following five areas: Maximized VA
Visual AcuityVA testing at appropriate distance so
as not to overwhelm the field with the letter size
RP patients have difficulty seeing a larger object at near
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Rehabilitation
Consider the goals as given by the AOO and work under the following five areas: Maximized VA
Visual AcuityProper illumination( towards a brighter side) depending on other ocular associations, Cataracts, for example
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Rehabilitation
Consider the goals as given by the AOO and work under the following five areas: Maximized VA
RefractionAllow for eccentric viewing(EV)Encourage the EV if the px achieves better VA
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Rehabilitation
Consider the goals as given by the AOO and work under the following five areas: Maximized VA
BinocularityThe asymmetric nature of RP makes it difficult for pxs to maintain healthy fusion because of differences in the acuity( > 2 lines)
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Rehabilitation
Consider the goals as given by the AOO and work under the following five areas: Maximized VA
BinocularityAlso the frequent association of nystagmus supports the binocularity, for monocularity seems to worsen nystagmus.
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Rehabilitation
Consider the goals as given by the AOO and work under the following five areas: Glare and photophobia control
Glare and photophobic sensitivities ???
Reduced contrast sensitivity, slower responses to dark adaptation and secondary media defects…
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Rehabilitation
Consider the goals as given by the AOO and work under the following five areas: Glare and photophobia control
Glare and photophobic sensitivities ???
The RPE tends to absorb less light hence supports light scattering.
Glare interferes with the middle and low spatial frequencies of patient’s CS so…
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Rehabilitation
Consider the goals as given by the AOO and work under the following five areas: Glare and photophobia control
Use of various lenses like Corning, NoIR.
These absorb wavelengths towards blue that are responsible for more scattering
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Rehabilitation
Consider the goals as given by the AOO and work under the following five areas: Glare and photophobia control
Corning LensesCPF 550(Amber) esp for RP
NoIR filters4% Dark Plum2% Medium Plum
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Rehabilitation
Consider the goals as given by the AOO and work under the following five areas: Glare and photophobia control
Corning LensesCPF 550(Amber) esp for RP
NoIR filters65% Yellow 49% Red
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Glare and Contrast
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Rehabilitation
Consider the goals as given by the AOO and work under the following five areas: Glare and photophobia control
Peaked capsTinted screen CCTVsAlso use of typoscopes
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Rehabilitation
Consider the goals as given by the AOO and work under the following five areas: Glare and photophobia control
IlluminationIncandescent lamps( 75-100)
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Rehabilitation
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Adequate light ( natural / lamp) for
daily tasks
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Rehabilitation
Consider the goals as given by the AOO and work under the following five areas: Glare and photophobia control
Place the lighting source behind the px
So as to do away with the possible unwanted glare
Place it to the side of the dominant eye
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Rehabilitation
Consider the goals as given by the AOO and work under the following five areas: Magnification
In peripheral field defects like in RP, the minimal magnification to be provided coz the stimulation of the peripheral retinal may be of little or no value.
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Rehabilitation
Consider the goals as given by the AOO and work under the following five areas: Magnification
Use of microscopes in later stages
Also handheld magnifiers, stand magnifiers
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Stand magnifiers
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Hand Held Magnifiers
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Rehabilitation
Consider the goals as given by the AOO and work under the following five areas: Visual Field
RP shows a cone shaped visual field.
Cone shaped??The patient will show a geometrically expanded field with increased testing distances
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Cone shaped VF in RP
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Rehabilitation
Consider the goals as given by the AOO and work under the following five areas: Visual Field
EnhancersPrismMinus lensMirrorReverse TelescopeConvex Mirrors
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Prism
E.g.. Fresnel prism
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Interpretation
When peripheral vision loss is severe (leaving central visual fields of less than 20°), mobility can be reduced.
Clinical rehabilitation options in dealing with tunnel vision using nonprismatic methods are limited and have had variable success
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Interpretation
Fresnel prisms may not cause the same central visual field degradation and have added advantages of cosmetic appeal, relative availability, and ease of fitting
The rationale for using prisms for field expansion involves increasing scanning effectiveness for patients, resulting in improved peripheral awareness.
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Interpretation
We constantly scan our environment using low spatial-frequency visual channels as we also intermittently spot and view points of interest in visual fields scanned, using various high spatial-frequency visual channels.
Cortical temporal multiplexing processes create visual perception as we know it by using the information obtained from scanning and spotting.
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Interpretation
In the presence of tunnel vision, prisms project peripheral fields information otherwise unavailable, thereby enhancing the scanning abilities of the eye.
Enhanced scanning ability will produce new spotting eye movements and together both visual skills in fact expand peripheral field awareness.
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Mirrors
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Minus lens
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Reverse Telescope system
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Amorphic lens
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Also contrast sensitivity…
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Also contrast sensitivity…
Contrast in Kitchen
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Environmental modification
Painted edges of Staircase
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O and M management
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O and M management
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Sensory- substitution devices
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Other Non-optical Devices
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Inheritance Sporadic, AD or XL
Presentation 2nd -4th decade with central Vf , CV impairment
Signs …
ERG Photopic response-abnormal
DA Cone segment abnormal
CV Deuteran-tritan defect
Prognosis Poor with eventual loss of CV to the level of 6/60 0r CF
Progressive Cone dystrophy
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dfnjks
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Stargardt macular dystrophy
Inheritance Sporadic, AR
Presentation 1st -2nd decade with central VF , malingering??
Signs …
ERG Photopic response-abnormal
DA Cone segment abnormal
CV Red-green defect
Prognosis Poor with eventual loss of CV to the level of 6/60
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Characteristics…
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Characteristics…
Poor Colour Vision
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Tests to be carried out…
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Management
Few guidelines, When scotoma is located right to the
macula, reading becomes difficult as the previous word disappears—leading to difficulty in tracking
When scotoma is located left to the macula, reading becomes difficult as a new word is readily invisible owing to a scotoma. So one should use finger or marker to overcome problem
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Management
Refraction Magnification Non-optical devices Lighting and glare control Eccentric Viewing Prism therapy Text Enhancement
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Management
Eccentric Viewing To extrafoveate an object of regard
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Management …EV
Discussion: Besides reducing reading speed, the central
scotoma interferes with other visual functions including Space perception Contrast sensitivity, Stereopsis Fixation stability
Contraindicated when some form of foveal function exists
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Management …EV
Discussion: After EV training, reading speed doubled
with little to no improvement in Visual Acuity.
Reading speed is a better parameter than visual acuity when reporting results of visual rehabilitation because Reading is more demanding than identifying a
few optotypes on a visual acuity chart A practicable approach to rehabilitating
patients with CF loss
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Management
Prism Therapy
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Management
Text Enhancement…
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Management…Text Enhancement Conclusion
Boosting the contrast increases the perceptibility of letters and therefore words, then reading gets faster
Increasing the size of character overcomes the scotomatous region thus allowing the non-macular area to fixate extrafoveally
Increasing the luminance of the characters allows for a better recognition.
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Psychological/Psychosocial problems in Retinal Dystrophy Fear of growing blind Fear of ostracism Impaired social life Susceptibility to harassment
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VI Child
EducationEye Care
Detect
Treat
Refer
Educate
Train
Low Vision Service
Identification
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References:
Tasca Jennifer, Edward A. Deglin. Chapter SIX ‘Common Disorders Encountered in Low Vision’ in “ESSENTIALS of LOW VISION PRACTICE”, 1ST Edition, BUTTERWORTH HEIMAN,1999
Kathleen Fraser Freeman, Cole Roy Gordon, Eleanor E Faye, Paul B. Freeman, Gregory L. Goodrich, Joan A. Stelmack. Optometric Clinical Practice Guideline Care of the Patient with Visual Rehabilitation(Low Vision Rehabilitation), American Optometric Association, 2007
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References:
Ferraro, J. and Jose, R. T. (1983). Training programs for individuals with restricted fields. In R.T. Jose (Ed.), Understanding Low Vision, American Foundation for the Blind, NewYork. Vol. 14, 363-376.
Crossland, Michael D. Visual rehabilitation of patients with macular diseases, in Focus, The Royal College of Ophthalmologists
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References:
Ajit Kumar Thakur, Purushottam Joshi, Himal Kandel, Subash Bhatta.Profile of low vision clinics in eastern region of Nepal: A retrospective study.British Journal of Visual Impairment 2011 29:215
Elisabeth M. Fine, Eli Peli.Enhancement of text for the Visually impaired.J. Opt. Soc. Am. A 1995;12;1439-1447
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References:
Jae Hoon Jeong, Nam Ju Moon. A Study of Eccentric Viewing for Low Vision Rehabilitation. Korean J Ophthalmol 2011;25(6):409-416
Berson EL, Mehaffey L III, Rabin AR. A night vision device as an aid for patients with retinitis pigmentosa. Arch Ophthalmol 1973;90:112–6.
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References:
William H. Ridder III, John B. Slegfried.Chapter 16 ‘Clinical Electrophysiology’ in Borish’s Clinical Refraction, 2nd Edition, BUTTERWORTH HEIMAN Elsevier,2006
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AND YOU THINK YOU ARE HAVING A BAD DAY AT WORK !!
Although this looks like a picture taken from a Hollywood movie, it is in fact a real photo,
taken near the South African coast during a military exercise by the British Navy. It has been nominated by Geo as "THE photo of the year".
THANK YOU!!!