Low vision rehabilitation in patients with retinal dystrophy

LOW VISION REHABILITATION

IN PATIENTS WITH RETINAL

DYSTROPHY

Amrit Pokharel

Dystrophy??

A hereditary, symmetrical, congenital or later appearing, slowly progressive affection, presenting slight intrafamilial variation, and of unknown etiology.

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

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

Retinal Dystrophies

Generalised photoreceptor dystrophies Familial benign fleck retina Pigmentary paravenous chorioretinal

atrophy Congenital stationary night blindness Congenital monochromatism

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

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

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

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

Goals

Increase access for the evaluation and rehabilitative care of individuals with visual impairment(s), thereby improving their quality of life.

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

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.

Quantifiers of Visual Impairment The ICD 10-ICIDH has employed the

following quantifiers: Visual Acuity

Visual Field

Contrast Sensitivity

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:

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

For rehabilitation work, must know thing: Visual field defect loss of contrast and

resolution

Central VF defect

Peripheral VF defect

√×√

√

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

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

CARE PROCESS

Diagnosis of Low Vision Patient History Ocular Examination

Refraction Use of JND technique

Radical retinoscopy

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

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

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

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

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

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

CARE PROCESS

Management (Low vision rehabilitation)

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

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

How to start??

An optometrist should individualize the management plan for each patient while planning a course of therapy.

How to start??

An optometrist should CONSIDER the following: Degree of VI

Underlying cause( here retinal dystrophy)

Patient’s age and developmental level

How to start??

An optometrist should CONSIDER the following: Overall health status of the patient

Patient’s adjustment to visual loss

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

Rehabilitation process

Use of devices:

Optical Devices Non-Optical Devices

RGPHOMeS

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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)

`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

Eccentric viewing

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

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

Retinitis Pigmentosa Usher Syndrome Hallgren’s Syndrome Refsum’s syndrome

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

ERG in RP Decreased in fERG Early pERG may be normal,

Later gets abnormal Amplitude reduction in the periphery that corresponds to VF defect

CHARACTERISTICS OF DISEASES

Dark Line in RetinaDecreased Night VisionLoss of Peripheral/Central VisionDecrease in Visual Acuity

Functional Implications

Peripheral vision lost

Limited visual field

Limited mobility Debilitating glare Extreme

sensitivity of light Eventual

Blindness

Rehabilitation

Wearing glasses Low vision

devices Magnification and

illumination of objects

Rehabilitation

Field enhancers are employed since visual field is markedly constricted.

Rehabilitation

So how is peripheral VF defect management launched?

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

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

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

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

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)

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.

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…

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…

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

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

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

Glare and Contrast

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

Rehabilitation

Consider the goals as given by the AOO and work under the following five areas: Glare and photophobia control

IlluminationIncandescent lamps( 75-100)

Rehabilitation

Adequate light ( natural / lamp) for

daily tasks

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

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.

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

Stand magnifiers

Hand Held Magnifiers

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

Cone shaped VF in RP

Rehabilitation

Consider the goals as given by the AOO and work under the following five areas: Visual Field

EnhancersPrismMinus lensMirrorReverse TelescopeConvex Mirrors

Prism

E.g.. Fresnel prism

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

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.

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.

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.

Mirrors

Minus lens

Reverse Telescope system

Amorphic lens

Also contrast sensitivity…

Also contrast sensitivity…

Contrast in Kitchen

Environmental modification

Painted edges of Staircase

O and M management

O and M management

Sensory- substitution devices

Other Non-optical Devices

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

dfnjks

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

Characteristics…

Characteristics…

Poor Colour Vision

Tests to be carried out…

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

Management

Refraction Magnification Non-optical devices Lighting and glare control Eccentric Viewing Prism therapy Text Enhancement

Management

Eccentric Viewing To extrafoveate an object of regard

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

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

Management

Prism Therapy

Management

Text Enhancement…

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.

Psychological/Psychosocial problems in Retinal Dystrophy Fear of growing blind Fear of ostracism Impaired social life Susceptibility to harassment

VI Child

EducationEye Care

Detect

Treat

Refer

Educate

Train

Low Vision Service

Identification

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

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

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

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.

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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