Low vision

1. Low Vision Management of Patient with
Age Related Macular Degeneration
Moderator: Presenters :
Niraj Dev Joshi Ashi Lakher
Chyavan Acharya

2. Layout
• Introduction of Low vision and AMD
• Visual deformities of patient with AMD
• Management of patient with AMD - Optical low vision aids
-Non Optical low vision aids
• Visual rehabilitation and support.
• Summary
• References

3. Introduction to Low vision :
• " A person with low vision is one who has impairment of
visual functioning even after treatment or standard refractive correction,
and has a visual acuity of less than 6/18 to light perception, or a visual
field less than 10 degrees from the point of fixation, but who uses, or is
potentially able to use, vision for the planning and execution of a task."-
Bangkok Definition of Low Vision
• Low vision affects more than 246 million people worldwide.
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4. • Visual impairment is a reduction in the ability of the eye or visual system
to perform.
• Categories of visual impairment :
category 0: mild VI with visual acuity better than 6/18
categories 3 and 4: profound VI with visual acuity worse than 3/60 to
perception of light, and
category 5: blindness with no perception of light.
category 1: moderate VI with visual acuity worse than 6/18–6/60
category 2: severe VI with visual acuity worse than 6/60–3/60
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LOW VISION

5. • WHO’s Tenth Revision of the International statistical classification of
diseases and related health problems( ICD-10) has included low vision as
category 1 and 2 of visual impairment.
• The purpose of low vision is to utilize or enhance the patient’s residual vision
in order that he or she may continue to perform daily living tasks and retain
the best quality of life.
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6. Age Related macular degeneration (AMD) :
• AMD is bilateral degenerative disorder of central retina , with age of onset
after fifth decade.
• It causes progressive , irreversible loss of central vision from fibrous
scarring of macular area .
• It is one of the leading causes of visual impairment in elderly people.
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7. Two type of AMD :
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8. Epidemiology:
• The various population based studies have shown that the prevalence
of AMD was 9.1% -20.9% among the whites and 3.1%-10.6% in Asian
peoples.
• In previous population based study in Nepal, AMD was found to
contribute 8.7% of total blindness.
-Age-Related Macular Degeneration in Nepal Kathmandu University Medical Journal 9(35):165-9july 2011
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9. Visual deformities of Patient with AMD :
1.Decreased Visual acuity:
Visual acuity with dry AMD ranges from 20/20 to 20/400 and with
wet AMD worse than 20/400 . There's no improvement in visual acuity
even with pinhole .
2.Visual field:
Visual field demonstrate central and para central scotoma with
normal peripheral findings.
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10. 3.Decreased contrast sensitivity
4.Metamorphopsia and micropsia.
5.Colour vision defect maybe seen.
6. Glare and photophobia
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11. Consequences:
• The visual symptoms of AMD manifest in a variety of ways, leading to
difficulties in areas such as reading, computer use, driving, and recognizing
faces.
• Severe AMD can make reading a single word almost impossible
without vision enhancement.
• Impaired abilities to perceive faces and recognize emotions are linked to
reduced quality of life and social engagement.
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12. Things to ponder before prescribing Low vision
aids:
• Patient’s goal must be explored and defined
• Determine the patient’s functional vision
• Determination of magnification required to perform certain task
• Determine the appropriate magnification devices or system
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13. Management of patient with AMD :
Note that in AMD , no form of treatment can prevent vision loss
however early treatment in the form of low vision aids and modified lifestyle
are helpful.
• Careful and complete refraction
• Optical Low vision aids
• Non optical Low vision aids
• Eccentric viewing and steady eye training.
• Visual rehabilitation and support
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14. Refraction :
• It is important that calculation of magnification takes place only after
patients optimum refractive correction.
• Off-axis retinoscopy maybe done in patient with eccentric fixation.
• Radical retinoscopy can be done to visualise the reflex.
• Trial lens to be used than phoropters because -
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15. -Larger lens aperture enables the patient to assume habitual eccentric fixation.
-Can include tinted trial lens, high powered microscopes in the trial frame.
• In patient with low to moderate vision loss ,near acuity can be improved by
increasing bifocal alone.
• Prism can also be incorporated to prescription glass to produce image
relocation at preferred retinal locus.
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16. • Distance low vision aids:
- Handheld telescope
-Spectacle mounted telescope
Optical Low vision aids:
• Near low vision aids:
- Spectacle reading glass
- Handheld magnifier
-Stand magnifier
- projection magnification
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17. Near low vision Aids:
Near devices are designed for magnifying close objects and prints.
1.Spectacle mounted reading glass :
• In this reading glass high plus lens are given in spectacle form.
• Microscope does not produce the increased retinal image, rather it acts as a
converging system to neutralize the diverging rays created by close proximity of
reading material.
• Based on the principle of Relative distance magnification.
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18. • Lens options:
1. Full field microscope
2. Half eye microscope
3. Bifocal microscope
4.Loupes
5.Contact lens microscope
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19. • Advantages :
- Reading can be done for prolong time.
-Cosmetically appealing and patient most familiar.
-Largest field of view among other devices.
-Both hand are free
• Disadvantages:
- Fixed close reading distance causes fatigue or unacceptable
posture to read.
-Illumination is obstructed
-Patients with eccentric fixation are unable to fix through
these glasses at times
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20. 2.Hand magnifiers:
• It is a convex lens mounted in a frame with the handle.
• The patients hold by means of handle at various distances from the spectacle
plane .
• It uses the principle of relative distance magnification and angular
magnification.
• The object should be placed at the focal distance of the magnifying lens.
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21. • Retinal image size is constant, regardless of the distance between the
hand magnifier and the eye.
• FOV is greater for close eye to lens distance.
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22. • Three common types of convex lens design are used,
1. Spherical lens
2. Aspheric lenses
3. Aplantic lenses
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23. • Advantages-
-Familiarity, inexpensive
-Work well in patients with eccentric viewing
-Illumination available
-More socially accepted
-most convenient for short term tasks
• Disadvantages-
-One hand tied up
-Difficult to hold steady in proper position at all times
-Limited FOV, depends on eye to lens distance
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24. 3.Stand magnifiers:
• A convex lens that is mounted at a fixed distance from the reading material.
• Not required to be hold by the person. It is supported by legs or a housing
that stand on the reading material.
• Principle -Relative distance magnification and angular magnification.
• Types of design:
1. Spherical lenses
2. Aspheric lenses
3. Aplantic lenses
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25. Light rays diverge as they leave an object (A). The lens of a stand
magnifier provides enough converging power to counteract some of
the divergence, but the rays continue to diverge a bit after they pass
through the lens (B). A plus power (convergent) spectacle lens is
then required to counteract the remaining divergence. After the rays
leave the spectacle lens (C), they emerge parallel for viewing by the
eye.
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26. • Advantages:
-Has a fixed focus, ease for Patient
-Good for patient with tremors/arthritis and constricted fields
-Self-illuminated
-Inexpensive, good for detailed tasks and short term task.
-Some design can be used for writing
• Disadvantages:
-Accommodation or add is needed
-Decrease field of view
-Too close to reading posture is sometimes painful for long hours.
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27. 4.Electronic Devices- CCTV:
• It provides projection magnification along with RDM.
• Provides magnified image projected onto a monitor screen.
•Head mounted video display systems provide:
-Autofocus magnification
-Variable brightness
-Contrast enhancement
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28. Distance Optical devices :
Telescopes:
• An optical instrument used to magnify the apparent size of distance
objects.
• In its simple form telescope contain two elements i.e.
1. Objective lens : Always positive or convergent lens that is placed
towards the object and is larger in diameter.
2. Ocular lens/eyepiece : Either convergent (positive lens in Keplerian
telescope) or divergent (negative lens in Galilean telescope) that is placed
closest to the eye.
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29. OPTICAL PRINCIPLE OF TELESCOPE:
Afocal (normal adjustment):
• The separation between Obj. & Oc. Lens is by their absolute value of
focal length.
• Produce only angular magnification.
• Parallel rays of light is incident and emerges out. Both object and image
located at infinity.
• Equivalent power of telescope = Zero.
MTS= - Doc / DOBJ
Where
Doc = power of ocular lens
DOBJ = power of objective lens
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30. Two types of telescopes:
The ocular lenses is positioned in such a way that its primary focal point
located coincident with the image formed by the objective lenses
Galilean telescope Keplerian telescope
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31. Galilean telescope Keplerian telescope
Objective lens positive positive
Eyepiece negative positive
Image Virtual and erect Real and inverted
Quality Poor Good
Magnification positive Negative
Tube length Shorter longer
Exit pupil Inside the telescope Outside the telescope
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32. Types:
1.Hand-held for quick spotting:
-Lightweight
-Inexpensive
-Quick and easy for spotting
2. Bioptic telescopes
-mounted in spectacles
-Quick and easy access by tipping head
-Monocular vs binocular depends on purpose
3. Telemicroscopes for intermediate distance
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33. Focal telescope:
• Telescope designed for distance vision can be adapted for intermediate
or near use by 3 different techniques,
-Increase power of objective lens
-Decrease power of ocular lens
-Increase separation of objective and ocular lens.
• Made focal due to relative distance magnification. Also referred
as Telemicroscope, Reading telescope, Surgical telescope ,Telescopic
loupe, Near point telescope.
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34. Telemicroscope
• Combination microscope and telescope
• Usually spectacle mounted
• Generally a microscope cap is placed on a telescope lens
• Gives advantage of microscope magnification at a longer focal distance
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35. • ADVANTAGE OF TELESCOPE :
-One of the possible device to enhance distant vision
- It can be focused to give distance and near magnification
- Can be incorporate with the patient prescription or telescope focus can
adjust
• DISADVANTAGE OF TELESCOPE
- Ugly appearance
-Expensive and costly
-Reduced depth perception
- Binocularity difficult to achieve
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36. Non Optical methods of low vision workout for
AMD.
• Use of relative size magnification (RSM)
• Adjustment of illumination
• Glare control
• Contrast improvement filters and UV protective filters
• Environmental Modification and elimination of Hazards
• Use of technology and artificial intelligence
• Eccentric Viewing
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37. Use of Relative Size Magnification
Use of Calculators, calendars, telephones or keyboards having large printed digits.
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40. • Use of Computer magnifiers and closed circuit television magnifiers
(CCTV) for habitual readers.
Size 28: Computers have plenty of magnification options like increment
of font size, use of free installed magnifiers or some other special ones.
Size 40: Computers have plenty of magnification
options like increment of font size, use of free
installed magnifiers or some other special ones.
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42. Adjustment of Illumination
The requirement of level of illumination increases in people having
AMD. So,
• Use adjustable window coverings to customize natural light that
comes inside.
• Use lightbulbs of at least 60 watts in rooms.
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44. Mirror Coatings
Polaroid glasses
Photo chromatic glasses
Sunglasses
Typoscope
Pinholes and Stenopaic slits
Use of shades
Glare free LED lightening
GLARE CONTROL
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46. Use appropriate brightness in computer screens for comfort
+40% Brightness
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47. Filters
Filters provide UV protection and contrast improvement.
The requirement of UV protection is very crucial to retard the
advancement of AMD.
The requirement of contrast improvement is for easy localization of the
objects.
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48. UV Protective filters include
• Polycarbonate Glasses
• Sunglasses
• Polaroid glasses
• Photo chromatic glasses
• CPF filters
• NoIR filters
Contrast enhancement filters include
• Color filters
• NoIR filters
• CPF (Corning color protection filters)
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52. Yellow acetate filter papers are also
used to enhance prints for low vision
people.
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53. Environmental Modification
• Use of RSM at home by replacing calendars, telephone
sets, wall clocks etc. with those providing good contrast
and having larger size.
• Use of good lightening conditions at home.
• Adjustment of appropriate color and contrast around the working
environment.
• Arrange mirrors so lighting doesn’t reflect off them and create
glare at home.
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57. Environmental modification: Elimination of
Hazards
• Arrange furniture in close areas
• Put adequate lighting near furniture
• Use tactile clues but avoid patterns, that create confusion
• Make furniture easier to locate by placing brightly-colored
vases and lamps nearby
• Replace worn carpeting and floor coverings
• Tape down or remove rugs to prevent slips
• Place the electrical cords safely
Cont.
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61. Use of technology
Talking calculator, keyboards, sphygmomanometers, thermometers,
clocks, microwaves etc. can contribute in lots of daily works and
even in medical management.
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62. Use of artificial intelligence
• Color Detector
• Money readers
• Book readers
• Face readers
• Product identifiers
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65. Eccentric Viewing
• Eccentric viewing is basically learning to look around the blind spot
particularly when blind spot lies within or around center of fixation.
• The patient should be encouraged to find a ‘sweet spot’ for viewing
using healthy peripheral vision.
• The patient should learn and practice to identify letters and numbers
with that sweet spot.
• Finally, the person should learn to hold the eyes still and read without
bringing the image to the macula where blind spot lies.
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66. Goals of low vision workout
after AMD
To ambulate comfortably at home and
in the surrounding
particularly when the old man is strong.
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67. Prof. Naya Raj Pant (1913-2002)
To read comfortably:
Habitual (Newspaper/ Religious),
Professional (Author, Artist, Scientist),
Business.
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68. Visual Rehabilitation
Problems:
• There is less self-esteem and acceptance of almost all
discomforts.
• Negligence and adaptation with loneliness,
helplessness and senility.
• Lack of desire to experience new and lack of desire to
live young.
• Stone script in the mind: Detrimental visual damage
at
old age is unavoidable.
• Lack of awareness about low vision rehabilitation.
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69. Visual Rehabilitation
• Motivation towards low vision aids in irreversible visual loss must be
an important aspect of public health issue and social awareness.
• People must be aware of levels of illuminations in working area.
• Improvement of environment and infrastructures according to the
ease of low vision people.
• Simple aids like magnifiers should be freely available.
• We must always be able to provide other smart options.
• We must teach old people comfortably so that they trust us to believe
in themselves to use the devices comfortably.
• We should always motivate old people to live young and free.
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71. References:
• Essential of low vision practice
• The low vision handbook for eye care professionals
• Previous presentation
• Internet