2. Introduction to
low vision

3. Standard Definition (WHO 1992)
Impairment of visual functioning in better eye
even after treatment and/or standard refractive
correction
and VA of <6/18 to light perception
or
a VF loss of <100 from point of fixation
but who uses, or is potentially able to use, vision for
the planning/execution of task

5. category Corrected
VA- better
eye
WHO
definition
working Indian
definition
0 6/6 – 6/18 Normal Normal Normal
1 <6/18 –
6/60
Visual
impairment
Low vision Low vision
2 <6/60 –
3/60
Severe
visual
impairment
Low vision Blind
3 <3/60 –
1/60
Blind Low vision Blind
4 <1/60 - PL Blind Low vision Blind
5 No PL Blind Total
blindness
Total blindness

6. DISORDER
IMPAIRMENT
DISABILITY
HANDICAPED

7.  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

8. Denial
Anger
Bargaining
Depression
Acceptance

9. Global burden of visual impairment
World wide (WHO 2001)
- Low vision : 124 million
- Blind : 37 million
World wide (children)
- Low vision : 7 million
- Blind : 1.5 million
Low vision : Blindness = 3.4:1

10. • Irreversible damage to ocular media or visual
pathway.
CHILDREN
 Albinism
 ROP
 Congenital malformation
 Optic neuropathy

11.  Keratoconus
 Ocular injuries
 Aniridia
OLD AGE
 ARMD
 Cataract
 Macular degeneration
 Retinal degeneration

12. COMMON CONDITIONS:
 ARMD
DIABETIC RETINOPATHY
ALBINISM
RETINITIS PIGMENTOSA
HISTOPLASMOSIS
STARGARDT’S DISEASES
ANIRIDIA

13. GLAUCOMA
NYSTAGMUS
OPTIC ATROPHY
COLOBOMA
CATARACT
RETINAL DETACHMENT
KERATOCONUS

14. Macular Degeneration

15.  Macula in the retina degenerates.
 Area effected – macula
VISUALAFFECT LOW VISION AIDS
•Fuzzy & Decreased vision •Good Lighting
•Metamorphopsia •Use of Strong color contrast
•Poor Central Vision •Magnifiers
•Photophobia •Non optical device
•Poor Color Perception •Vision Reabilitation
•Better vision at night

17.  Breakage of retinal blood vessels and leaks.
 People with long standing diabetics.
 Area affected – Retina.
VISUALAFFECTS LOW VISION AIDS
•Decreased visual acuity •Various illuminators
•Fluctuating Vision •Work under direct light
•Loss of color vision, visual
field
•Visual rehabilitation
•Inability to accommodate,
floaters

18. Retinopathy

19.  Retinal pigmentary degeneration.
 Rods of retina are slowly destroyed.
 Area affected – Retina.
VISUAL EFFECTS LOW VISION AIDS
•Decresed visual acuity •Optical aids – telescopes
•Difficulty in night vision •Nightscopes
•Loss of peripheral field vision •Fresnel prism, visual field
expanders
•Photophobia •Use of filters
•Poor contrast sensitivity •High contrast letters
•Difficulty to adapt in changing
illumination
•Rehabilitation

20. Retinitis Pigmentosa

21.  Aqueous humor does not drain normally &
excessive pressure is built within the eye,
resulting in damage of optic nerve.
 Area affected – Optic Nerve.
VISUAL AFFECT LOW VISION AID
•Gradual blurred vision •Magnifiers depending upon
extent of v.f
•Haloes around light •CCTV
•Reduced peripheral vision •CPF lens to reduce glare
•photophobia •Prism

22. Glaucoma

23.  Opacification of lens causing less amount of
light to the retina, vision becomes hazy &
inconsistent.
 Area affected – Crystalline Lens.
VISUALAFFECTS LOW VISION AID
•Blurred vision •Close work use direct light
•Glare, difficulty in bright light •Use sunglass to avoid glare
•Diplopia •Stand magnifiers for near work
•V.F normal. Sometimes Reduction
in side vision
•Filters - amber, red brown filters
•Squinting and amblyopia

24.  Retina is separated from its supporting
structures & receives no nourishment.
 Blind area develops in area of detachment
 Area Affected – Retina.
VISUALAFFECTS LOW VISION AIDS
•Flashers & Floaters •High illumination
•Visual acuity is decreased •Filters, CPF lens
•Micropsia •Magnification for both near &
distance
•Color vision is impaired •Non optical aids
•Loss of visual field
•Photophobia & glare

25.  Total or partial loss of pigments in the eye.
 Characterized by light colored iris, eyebrows.
 Area affected – Retina, macula.
VISUALAFFECT LOW VISION AIDS
•Decreased visual acuity •Dim illumination
•DV more effected than NV •Dense sunglasses
•Painful photophobia •Absorptive lenses
•V.F is normal •Telescope for DV
•Color vision is normal •Colored or pinhole type CL

26. Albinism

27. Central
field loss
Overall blur
Peripheral
field loss
Functional Effects of Low Vision:

28.  Loss of central vision (eg. macular degeneration, toxoplasma scar
etc.)
 Difficulty reading
 Problems writing/ completing paperwork
 Inability to recognize distance objects and faces
 Loss of peripheral vision (eg. Retinitis pigmentosa, glaucoma etc. )
 Difficulty in mobility and navigation
 Difficulty reading if there is constricted central visual field
 Visual acuity may not be affected until very advanced disease
 Cloudy media (eg. Corneal scar, vitreous hemorrhage etc.)
 Blurred vision
 Reduced contrast
 Problems with glare

29. Evaluation
 External observation
 Detailed history taking
 Functional vision assessment
 Defining goals of the patient

30. Management
 Trial & selection of LVD
 Low vision device training
 Counseling

31. In the waiting area
On entering the examination room
Mannerisms of the patient
Physical appearance
Communication skill

32. Patient details
a. Occupation
b. Living situation
c. General health
d. Other limitations
e. Family history
f. Previous low vision care

33. Difficulty in visual tasks
a. Distance visual tasks
b. Near visual tasks
c. Computer usage
d. Light sensitivity
e. Mobility issues
f. ADL

34. Visual acuity
Refraction
Contrast sensitivity
Color vision testing
Visual field assessment

35. Material required: Variable distance Log MAR
chart [ Bailey Lovie/ETDRS chart] for distance.
Continuous text or word reading chart for near
Setup: Normal room illumination
Start with better eye first
Allow change in head posture, eccentric viewing,
head movements etc.
Check monocular visual acuity followed by
binocular

36.  Distance:
 Snellen (projection)
 Feinbloom/ SOSH
 ETDRS
 Lea Symbols
 Bailey & lovie charts
 Near:
 MN read acuity chart
 Light house near test chart.

39. Perform retinoscopy instead of auto refractors
Calculate just noticeable difference
Aim to improve the quality of vision

40. 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

42. 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.

44. Amsler grid:
• Assess central VF
• Absolute scotoma
• Relative scotoma
• Metamorphopsia

45. Confrontation
• Assess peripheral VF
• Checked in all 4 quadrants
• Quick and basic.

46. Low vision device:
It is a device that enables the patient to
improve his/her residual visual performance & helps to
attain functional vision for the particular task of
concern.
Categories of LVD:
a] Optical
b] Non optical
c] Electronic
d] Assistive devices

47. BASIC PRINCIPLE : MAGNIFICATION.
 Enlarges image on retina to stimulate more
retinal cells
 Can be achieved in many ways
 Relative Distance
 Relative Size
 Optical / Angular
 Electronic.

48. Relative Size Magnification:
Any activity of daily living in which the object
being viewed can be made larger (E.g. Large print
Reader’s digest)
Relative Distance Magnification:
Any activity of daily living in which the distance
between the object and the viewer can be reduced
(E.g. moving closer to television)
Angular magnification:
Use of an optical system between the eye and the
object to make the object appear larger (E.g. Use of
a telescope to see a distant object)

49. DISTANT OPTICAL
AIDS
1. Telescopes
2.Projection
Devices
3.Pin- Hole
Spectacles
4.See TV
NEAR OPTICAL
AIDS
1.Spectacle
Magnifiers
2.Stand
Magnifiers
3.Dome
Magnifiers
4.Bar Readers
etc.

50. Near
spectacles
Bifocals
PAL upto
+3.
High
Asperical
lenses
+6.00 -
+20.00D
High Plus
Prismatic
lens
+4.00-
+14.00D

52. Enable copying from the black board
Identifying street signs
Seeing traffic signals
Seeing bus numbers
Spot viewing
Watching movies in theatre
Enjoying sporting events

53.  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:
 Hand held monocular
 Clip on design
 Bioptic design: mounted on a pair of eyeglasses

54. a
β
Objective
Eye piece
fo
fe

55. fo fe
α
Objective Eyepiec
e
β

56.  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
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

57.  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

58. MONOCULARS
MONOCULAR MONO
AUTOFOCUS
BINOCULARS
SPECTACLE
MOUNTED

59.  Spectacles
Prismatic ½ eyes
Bifocals
 Magnifiers
Hand held vs. stand
Illuminated vs. non-illuminated
 Electronic Devices

61. 5/20/2014APPROACH & ASSESMENT OF LVC-CME 62
Spectacle magnifier is a
spectacle mounted convex lens
This uses the principle of relative
distance magnification
Full fields
Half eyes
Useful for prolonged reading

62. 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

63. 5/20/2014APPROACH & ASSESMENT OF LVC-CME 64
A stand magnifier is a convex lens
mounted at a fixed distance from
reading material
Both angular magnification and
relative distance magnification are
used
Device of choice for tremors,
arthritis, constricted fields
Self illuminated
Non-illuminated

65. Predictable focus Poor posture unless reading
stand is used
Device of choice for
tremors, arthritis,
constricted fields
Reduced illumination in case
of non illuminated sand
magnifiers
Portable Requires flat surface to keep
reading material
Variable eye to lens
distance
Reduced field of view

66. 5/20/2014APPROACH & ASSESMENT OF LVC-CME 67
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

68.  Closed circuit television system (CCTV) 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

70.  Glare reduction devices
 Contrast enhancement devices
 Computer software
 Accessory devices
 Talking watches, clocks, etc
 Writing guides
 Tactile markers

71. 5/20/2014APPROACH & ASSESMENT OF LVC-CME 72
Relative size and larger assistive device
Glare, Contrast and lighting control device
Posture and comfort maintenance device
Hand writing and written communication device
Orientation and mobility techniques and devices
Sensory substitution device
Medical management and life skill device

72.  Reading lamp
 Reading stand
 Writing guide
 Reading guide
 Signature guide
 Bold line note books and papers
 Black ink bold tip pens
 Soft lead pencil – 2B,4B,6B
 Needle threader
 Notex etc…

73.  Black cards with rectangular cut outs horizontally along the card
 The patient can feel the empty cut out spaces and write

75.  It is a rectangular piece of cardboard with steps on top
right corner which helps in identifying the currency of the
note
 1st cut indicates Rs. 500, 2nd cut indicates Rs.100, 3rd cut
indicates Rs 50 and so on.

76.  Larger object subtends a larger visual angle at the eye and
is thus easier to resolve
 Large print material
 Large type playing cards, computer keyboards
 Enlarged clocks, telephones, calendars

77. o Attenuate 100% of UVB wavelengths.
o Block 99% of UVA wavelengths.
o The blue light portion of the visible spectrum is most likely
to scatter in the eye, causing discomfort and hazy illusion.
o Attenuate 98% of high-energy blue light, with exception of
CPF 450, which is 96% of high-energy blue light.
o The number of the CPF glasses correspond to wavelength
in nanometers above which light is transmitted

78. 5/20/2014APPROACH & ASSESMENT OF LVC-CME 79

79. 5/20/2014APPROACH & ASSESMENT OF LVC-CME 80

81. Closed circuit television
[CCTV]
Monitor CCTV Portable CCTV Mouse model
CCTV

82. 5/20/2014APPROACH & ASSESMENT OF LVC-CME 83
ONYX JORDY

83. 5/20/2014APPROACH & ASSESMENT OF LVC-CME 84
BUDDY PLAYER QUICK LOOK ZOOM CLASSMATE READER

84.  Mostly used chart for assessing near
acuity of a low vision patient.
 It was developed at Minnesota laboratory
for low vision research.

87.  TYPES:
1. Black letters on white background.
2. White letters on black background.
 USES:
1. Reading Acuity
2. Critical Print Size
3. Maximum Speed

88. Chart Design
Measurement Of Reading Acuity
Measuring Reading Speed

89. It’s a continuous-text reading acuity
chart.
Each sentence contain 60 characters
printed in three lines.
It contains 19 different print sizes.
Its print style is similar to that found in
many newspapers and books.
The text is printed with high contrast.

90. Formulae :
Reading speed = 60*(10-errors)/(time
in seconds).
 If more than 10 errors were made
then reading speed can be assumed
to be zero.

91. Chart Illumination – Luminance at
least 80cd/m.
Viewing Distance - 40cm
Testing Procedure…
Calculation formulae:
Acuity = 1.4 –
(sentences*0.1)+(errors*0.01)

92.  “Visually disabled are not fallen souls”
 “Positive attitude towards them will make them
socially amicable, psychologically adjustable and
educationally sound”
 The unlimited opportunities and experiences
extended to them will make them physically fit
mentally alert and totally independent in the
community