The document discusses low vision rehabilitation, including definitions of low vision, epidemiology of visual impairment, approaches to assessing patients with low vision, types of low vision aids, and recent advances in the field. It provides details on the history and assessments involved in low vision rehabilitation, as well as optical and non-optical devices that can help patients with low vision maximize their remaining vision.

1. VISUAL REHABILITATION IN LOW VISION
27TH JANUARY 2020
SPEAKER DR. SIDDHARTH DUGGAL
CHAIRPERSON DR. PARUL ICHHPUJANI

2. CONTENTS
 Definitions
 Epidemiology
 Approach to patient with low vision
 Low vision aids
 Recent Advances
 Summary

3. HISTORY OF LOW VISION REHABILITATION (LVR)
 Marco Polo during his 14th century travels to China discovered, that elderly
people used magnifying glasses for reading, was quickly adopted in Europe,
becoming a fad among educated and rich
 In United Kingdom, the Royal National Institute for Blind was established as
early as 1868, with Queen Victoria as patron.
 National Institute for Empowerment of Persons with Visual Disabilities
(Divyangjan), Dehradun, established in 1967 under Ministry of Social Justice
and Empowerment, is training centre for blind, engages in production of
Braille literature, aids and appliances for visually handicapped.
State-of-the-art: low vision rehabilitation. Markowitz SN 2016 Can J Ophthalmol.

4. WHAT IS LOW VISION?
 WHO Definition BCVA better eye of <6/18 to light perception or a VF loss of
<100 from point offixation in better eye, but who uses, or is potentially able to
use, vision for planning/execution of task
 Visual disorder Anatomical changes in the visual organ caused by the disease
of the eye
 Visual impairment Functional loss that results from the visual disorder
 Visual disability Refers to vision related changes in the skill and abilities of the
patient
 Visual handicap Psychosocial and economic consequences of visual loss
Denial Anger Bargaining Depression Acceptance
Source : www.nhp.gov.in

5. Distance vision impairment
Mild Best corrected visual acuity worse than 6/12
Moderat Best corrected visual acuity worse than 6/18
Severe Best corrected visual acuity worse than 6/60 (or) visual field diameter of
20⁰ or less.
Near vision impairment
Presenting near visual acuity N8 or M.08 or worse with existing correction
WHAT IS LOW VISION?
LVR indeed is a multidisciplinary professional service that provides methods
and means for optimal use of residual visual functions, training of residual
vision-related skills, and reintegration in society
Source : www.nhp.gov.in

6. DEFINTIONS
 Blindness Presenting distance visual acuity less than 3/60 (20/400) in the better
eye or limitation of field of vision to less than 10 degrees from centre of fixation
 Economic blindness Inability of a person to count fingers from a distance of 6
meters or 20 feet (6/60) in the better eye
 Social blindness Presenting distance vision less than 3/60 or diminution of field of
vision to less than 10° from center of fixation in the better eye
 Manifest blindness Vision 1/60 to just perception of light in the better eye
 Absolute blindness No perception of light in the better eye
Source : www.nhp.gov.in

7. EPIDEMIOLOGY
 39 million people worldwide are blind of which 8 million in India, 217 million
people with moderate or severe distance vision impairment worldwide
 Of these, 124 million people have uncorrected refractive errors and 65 million
have cataract—more than 75% of all blindness is avoidable
 1.3 billion people with vision impairment, 50 million in India
 The prevalence of blindness and vision impairment combined has
dropped from 4.58% in 1990 to 3.37% in 2015.
 89% of vision impaired people live in low and middle-income countries
Flaxman SR, Bourne RRA, Resnikoff S, Ackland P, Braithwaite T, Cicinelli MV, et al. Global causes of blindness and
distance vision impairment 1990-2020: a systematic review and meta-analysis. Lancet Glob Health.

9. CAUSES OF BLINDNESS
62%
20%
6%
5%
1%
1% 1%
4%
Cataract
Refractive errors
Glaucoma
Posterior segment
disorders
Surgical complications
Source of data: http://npcb.nic.in

10. CAUSES OF LOW VISION
Children Adults Elderly
Retinopathy of Prematurity Ocular Trauma Age Related Macular
Degeneration
Congenital Cataract Retinitis Pigmentosa Diabetic Retinopathy
Albinism Pathological Myopia Advanced Glaucoma
Nystagmus Macular Dystrophies
Microphthalmos Retinochoroidal Coloboma
Lebers Optic Atrophy
Source of data: http://npcb.nic.in

11. Central
field loss
Overall blur
Peripheral
field loss
Macular Degeneration
Wet ARMD, Macular
Dystrophies, DR,
Toxoplasma scar
Retinitis Pigmentosa,
Advanced Glaucoma
Corneal scar ,
VH
PROBLEMS OF LOW VISION

12. WHAT ARE LOW VISION AIDS?
 Devices which help the people to use their sight to better advantage
 Can be optical devices like magnifiers or telescopes, or non optical
devices like stands, lamps and large prints.
 Alter the environment perception through
1. BBB – bigger brighter and blacker
2. CCC – closer color and contrast

13. HISTORY
 Ocular history
 To know cause of low vision
 To know the progression of disease
 Systemic diseases that may pose difficulty in using certain devices eg.
arthritis, tremors
 Task analysis

14. GENERAL OBSERVATION OF THE PATIENT
 Does the patient appear to be bothered by bright lights?
 Can the patient navigate themselves to your consulting room?
 General mobility? Guidance
 Physical infirmities – e.g. hand tremor
 Eccentric viewing

15. DISTANCE VISUAL ACUITY:
 ETDRS distance visual acuity test chart is preferred
over the standard snellen’s chart as it has :
 Equal line difficulty
 geometric progression of optotype size from line to line
 5 letters on each line
 More lines at lower level of visual acuity
 Test distance of 2 meters can be used to cover visual
acuity upto 20/400

16. NEAR VISUAL ACUITY:
 Text samples are better than single letter acuity
charts
 Metric notations are used
 1M symbol or N8 or 0.6 logmar subtends an angle of
5 minutes of arc at 1 meter and is
 roughly equal to the size of the newsprint
 Visual acuity is recorded as distance of reading
material (in meters) over the letter size (in M units)
 Snellens equivalent can be calculated from the
metric notations

17. PREDICTING THE MAGNIFICATION REQUIRED
USING DISTANT VISUAL ACUITY
 Magnification required = required VA
present VA
 In Snellen notation to improve from 6/60 to 6/6
 Magnification required = 6 x 60
6 x 6 = 10 x (Kastenbaum’s rule)
 If VA is measured in a LogMAR notation: Magnification = (1.25)n Where n =
number of steps
 If the present acuity = 0.5 and the required acuity = 0.1 Then Magnification =
(1.25)4 = 2.44x

18. PREDICTING THE MAGNIFICATION REQUIRED
USING NEAR VISION
 N print uses New Times Roman font and is the standard UK test.
 It has a linear scale:
 N10 is 2x the size of N5
 Magnification required = present VA N48 M = 8x
required VA N6
 A measurement of near VA should always be accompanied by the working
distance at which it is taken.

19. CONTRAST SENSITIVITY
 Purpose: To measure the ability to detect
differences in luminance
 Charts used:
 a) Variable contrast fixed symbol size e.g. Pelli
Robson
b) Fixed contrast with variable symbol size
e.g. Bailey Lovie
 Generally checked binocularly in patients with
low vision
 If contrast sensitivity is impaired, then advice
and recommend the ways to enhance contrast in
the living environment such as bright light

20. VISUAL FIELD ASSESSMENT
 Amsler grid: Assess central VF
 Absolute scotoma
 Relative scotoma
 Metamorphopsia
 Confrontation test: Assess peripheral VF
 Checked in all 4 quadrants
 Quick and basic.
 HVF or Octopus if vision >6/60

21. ASSESSMENT (CONTINUED)
 Glare: Measuring visual acuity both with and without illumination
in the chart, loss of sensitivity for low contrast targets may occur
in the presence of high ambient illumination due to light scatter
producing - disability glare may occur
 Color Vision: Usually done with Farnsworth Munsell d-15 Color
discrimination
 Performed in ambient illumination with appropriate correction
 Can emphasis on using vibrant Colors in the environment if
required.
Available at www. Munsell.com

22. Low vision aids
Optical Devices
Distant Vision Near Vision
1. Handheld telescopes
2. Mounted telescopes
3. Electronic systems
1. Spectacles: Prismatic ½ eyes or Full-field microscopes
2. Magnifiers: Handheld or Stand held Illuminated or non-illuminated
3. Telemicroscopes
4. Electronic Devices
Non Optical Devices 1. Glare reduction devices
2. Contrast enhancement devices
3. Computer software
4. Accessory devices Talking watches, Writing guides, Tactile markers

23. DISTANCE LOW VISION OPTICAL DEVICES
TELESCOPES
 Work on the principle of angular magnification
 Telescopes with magnification power from 2x to 10x are prescribed
 They can be prescribed for near, intermediate and distant tasks
 Field of view decreases with magnification
Types:
 Handheld monocular
 Clip on design
 Bioptic design: mounted on a pair of eyeglasses

24. TELESCOPES
Galilean telescope Keplerian telescope
The eye piece is a negative lens and the objective is a
positive lens
Both eye piece and objective are positive lens
Resultant image is virtual and erect Resultant image is real and inverted. Prisms are
incorporated to erect the image
Loss of light reduces brightness of the image Loss of light is more in this system
Field quality is poor Field quality is relatively good
• Principal Telescopes consist of two lenses (in practice two optical systems)
mounted such that the focal point of the objective coincides with the focal point
of the ocular.
• Objective lens is a converging lens

25. a
Objective
Eye piece
β fo
fe
GALILEAN TELESCOPE

26. fo fe
α
Objective
Eyepiece
β
KEPLERIAN TELESCOPE

27. TELESCOPES
 Magnification of a telescope is given by the formula M =fo/fe
 Telescopes can be used to focus near objects by changing the distance
between objective and ocular lens
 Increasing the power of the objective lens

28. NEAR VISION LVA
MAGNIFIERS
 Spectacle magnifier is a spectacle mounted convex lens
 This uses the principle of relative distance magnification
 Full fields or Half eyes
Advantages Disadvantages
Psychologically acceptable Short working distance
Useful for prolonged reading Reduced illumination
Large field of view Inconvenient for spot reading
Binocularity is possible with lower
magnification
Limited range of magnification
Useful for other near tasks such
as writing
Not effective in constricted fields

29. STAND MAGNIFIERS
 A stand magnifier is a convex lens mounted at a fixed
distance from reading material
 Both angular magnification and relative distance
magnification are used
 Can be Self illuminated or Non-illuminated
Advantages Disadvantages
Predictable focus Poor posture unless reading stand is used
Device of choice for tremors, arthritis, constricted fields Reduced illumination in case of non illuminated
Portable Requires flat surface to keep reading material
Variable eye to lens distance Reduced field of view

30. HANDHELD MAGNIFIERS
 A hand-held magnifier is a convex lens that holds
by means of handle at various distances from
reading plane
 Suitable in patients with eccentric viewing
 May be self illuminated Portable

31. CLOSED CIRCUIT TELEVISION SYSTEM (CCTV)
 It consists of a monitor, a camera and a platform to
place the reading text
 It has control for brightness, contrast and change of
polarity
 Magnification varies from 3X to 60X

32. NON OPTICAL DEVICES
There are 7 categories of the same:
1. Relative size and larger assistive device
2. Glare, Contrast and lighting control device
3. Posture and comfort maintenance device
4. Hand writing and written communication device
5. Orientation and mobility techniques and devices
6. Sensory substitution device
7. Medical management and life skill device

33. WRITING GUIDE
 The patient can feel the empty cut out spaces and
write
 Black cards with rectangular cut outs horizontally
along the card

34. CORNING PHOTOCHROMIC FILTERS (CPF) GLASSES
 Attenuate 100% of UVB wavelengths, block 99% of UVA
wavelengths.
 The blue light portion of the visible spectrum is most
likely to scatter in the eye, causing discomfort and hazy
illusion.
 Attenuate 98% of high-energy blue light, with exception
of CPF 450, which is 96% of high-energy blue light.
 The number of the CPF glasses correspond to
wavelength in nanometers above which light is
transmitted

35. CORNING PHOTOCHROMIC FILTERS (CPF) GLASSES
Type Mechanism Role
CPF® 550 (red) Lens colour varies from
orange-red when lightened
to brown when darkened.
retinitis pigmentosa
albinism
CPF® 527 (orange) Orange amber lens darkens
to brown in sunlight, giving
individuals better visual
function and reduced glare
retinitis
pigmentosa
diabetic retinopathy
CPF® 450 (yellow) enhances contrast and helps
control glare indoors
optic atrophy albinism
pseudophakia
CPF® 511 (yellow orange) Medium range filter
provides moderate blue light
filtering
macular degeneration
glaucoma
aphakia
pseudophakia
optic atrophy
developing cataracts

36. NOIR FILTERS
 Absorbs the short wavelengths of the visible spectrum that
can scatter within the ocular media,
 Also absorbs ultraviolet light (to 4000 nm) and infrared light
 Manages overall visible light transmission (VLT) to allow the
proper amount of light energy to reach the eyes

37. REHABILITATION IN CHILDREN
 Vision assessment by various different methods including fixation
patterns and preferential looking tests like teller acuity cards
 Teaching children with low vision learn using books written in braille
help in social integration
Age Testing distance (Teller acuity
cards)
Infants up to 6months 38 cm
7 months to 3 years 55cm
>3 years 84 cm or using picture charts
ASSESSMENT OF VISION IN INFANTS AND CHILDREN. National Academies Press

38. REHABILITATION IN CHILDREN
 Besides vocational training Indian Association for the Blind
coaches visually challenged students to confidently take up
competitive exams for public and private sector jobs
 They are encouraged to join various training programs
including courses in computer education under IT program
started in 2005
 Comprehensive skill training is imparted to train students in
areas of their interest and to enable them to access
mainstream employment opportunities.

39. APPLICATIONS AND WEBSITES
1. Visual Attention Therapy: It helps people with visual neglect and visual filed
loss improve awareness of the neglected side of space.
 Practicing scanning from left to right across a page helps retrain the brain to
move the eyes correctly and strengthening this essential skill improves
reading, concentration, memory, attention to detail, and speed of processing.
2. Constant Therapy: It is a similar app to above and offers tasks to improve
memory, language, speech and cognition.
3. Eye Exerciser 3.0: It uses targets on the screen to help patients improve the
accuracy of their eye movements

40. APPLICATIONS AND WEBSITES
4. Durham Reading and Exploration training (DREX): Through
regular training and assessment teaches how to compensate for
visual field loss
5. Games: Like Stroke Monster, Eyesight, The Eagle Eye, Impossible
Eye Test, Word Run, Word Search etc help in scanning ability
7. Read Right: www.readright.ucl.ac.uk improves reading
speed in patients with homonymous hemianopia alexia
8. Eye Search: www.eyesearch.ucl.ac.uk for patients with
hemianopia or vision neglect

42. RECENT ADVANCES IN LVR
1. Gene Therapy LUXTURNA® Voretigene
neparvovec-rzyl: First FDA-approved
gene therapy for a genetic disease namely
Leber’s congenital amaurosis, has
patients with DNA RPE65 gene segments
attached to a vector are injected into the
sub retinally in eyeball and help restore
production of RPE65 proteins required for
normal vision function.
Leber congenital amaurosis/early-onset severe retinal dystrophy: clinical features, molecular genetics and
therapeutic interventions Br J Ophthalmol 2019

43. RECENT ADVANCES IN LVR
3. Electronic magnification: provides magnification that is
not suitably provided with ground optical lenses.
Computer software can assist visual experience with audio
signals or convert video to speech output.
Close-circuit TV units are available in a variety of models
providing magnification for distant, intermediate, and near
targets, are also available as desktop, portable, and pocket-
size units
State-of-the-art: low vision rehabilitation. Markowitz SN Can J Ophthalmol.
Smartlux® CCTV
eSight® CCTV

44. RECENT ADVANCES IN LVR
 4. Smart glasses (Oxsight®): It increasing the
horizontal field of vision to up to 68 degrees, helps
people with peripheral loss of vision due to stroke, RP
and advanced glaucoma etc.
 OXSIGHT Prism™ glasses features an occluder that
blocks external light completely, focusing your vision on
the colour-rich OLED projection on the lenses.
 The OXSIGHT Crystal™ glasses, have removable
sunglass shades that allow eye contact while also
providing help for those less tolerant to bright lighting.

45. RECENT ADVANCES IN LVR
5. Argus II retinal prosthesis is an epiretinal implant
designed to stimulate residual ganglion cells in cases in
which photoreceptors are lost with residual native vision.
Currently FDA approved for use in cases of retinitis
pigmentosa; the first cases were implanted in Canada in
2014 and recent studies show a definite improvement in
visual functions in those using the device.
Humayun MS, Dorn JD, da Cruz L, et al. Interim results from the international trial of second sight’s visual
prosthesis. Ophthalmology. 2012;19:779-88.

46. RECENT ADVANCES IN LVR
5. Retinal pigment epithelium (RPE)
patch graft of human embryonic stem cell
(hESC)-derived RPE cultured on a plastic
polymer substrate that is transplanted
between the native, degenerated RPE and
photoreceptor outer segments for RP,
ARMD, Stargardts disease patients etc
Currently undergoing preclinical research to
phase I/II clinical trials not just regarding
efficacy but also to elucidate the levels of
immunosuppression required
Stem cells in retinal regeneration: past, present and future. Conor M. Ramsden Development. 2013
Jun 15;

47. 6. Orion cortical visual prosthesis (Bionic Eye) FDA approved for RP, AMD
patients or those with severe vision loss but can’t be used for people who were
born blind as it relies on patient having a healthy optic nerve and a developed
visual cortex
 The prosthesis consists of a digital camera built into a pair of glasses, a video
processing microchip built into a hand held unit, a radio transmitter on the
glasses, a receiver implanted above the ear, a retinal implant with electrodes
on a chip behind the retina
 Subjects have to learn to interpret the array of white and dark dots
Banarji A, Gurunadh V, Patyal S, Ahluwalia T, Vats D, Bhadauria M. Visual Prosthesis: Artificial Vision. Med J Armed Force
India. 2009 Oct;65(4):348–52.
RECENT ADVANCES IN LVR

48. Camera captures an image
Send image to microchip
Convert image to electrical impulse of light and dark pixels
Send image to radio transmitter
Transmits pulses wirelessly to the receiver
Sends impulses to the retinal implant by a hair thin implanted wire
The stimulated electrodes generate electrical signals that travel to the visual cortex
RECENT ADVANCES IN LVR

49. SUMMARY
 LVR had advanced a long way in the last hundred years
 Apart from traditional LVAs including magnifiers and telescopes and recent
LVAs including electronic magnifiers and visual field expanders
 However, more needs to be done because only a fraction of those in need of
LVR receive help and there are large inequalities worldwide.
 Recent advance in the 21st century, including artificial implants and gene
therapy it seems hold the key to the future

50. THANK YOU FOR YOUR KIND ATTENTION
“THE ONLY THING WORSE THAN BEING BLIND IS HAVING SIGHT BUT NO VISION”
HELLEN KELLER