Low vision

1. LOW VISION

2. Introduction to low vision

3. What is Low Vision? 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 <10 from point of fixation but who uses, or is potentially able to use, vision for the planning/execution of task

4. CLASSIFICATION

5. category Corrected VA- better eye WHO definition working Indian definition 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. WHO Classification DISORDER IMPAIRMENT DISABILITY HANDICAPED

7. Impact of ocular disease on the patient 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. Psychological factors

9. PREVALENCE 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. ETIOLOGY Irreversible damage to ocular media or visual pathway. CHILDREN Albinism ROP Congenital malformation Optic neuropathy

11. young adult 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. ARMD (Age Related macular degeneration ) Macula in the retina degenerates. Area effected – macula VISUAL AFFECT 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

16. ARMD

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

18. Retinopathy

19. RETINITIS PIGMENTOSA 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. GLAUCOMA 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. CATARACT Opacification of lens causing less amount of light to the retina, vision becomes hazy & inconsistent. Area affected – Crystalline Lens. VISUAL AFFECTS 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. RETINAL DETACHMENT Retina is separated from its supporting structures & receives no nourishment. Blind area develops in area of detachment Area Affected – Retina. VISUAL AFFECTS 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. ALBINISM Total or partial loss of pigments in the eye. Characterized by light colored iris, eyebrows. Area affected – Retina, macula. VISUAL AFFECT 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. Functional Effects of Low Vision :

28. Behavioral implications 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. Clinical assessment 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. External observation In the waiting area On entering the examination room Mannerisms of the patient Physical appearance Communication skill

32. Detailed history 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. Low vision evaluation Visual acuity Refraction Contrast sensitivity Color vision testing Visual field assessment

35. Visual acuity 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. Types of Acuity Charts: Distance: Snellen (projection) Feinbloom/ SOSH ETDRS Lea Symbols Bailey & lovie charts Near: MN read acuity chart Light house near test chart.

37. Distance Charts

38. Near Charts

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

40. 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

41. Contrast Tests:

42. Color vision assessment 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.

43. Color Vision Tests:

44. Visual field assessment Amsler grid: Assess central VF Absolute scotoma Relative scotoma Metamorphopsia

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

46. Management options in low vision 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. OPTICAL AIDS 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. Types of Magnification 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. SPECTACLES TYPES :

50. DISTANT OPTICAL DEVICES

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

52. 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: Hand held monocular Clip on design Bioptic design: mounted on a pair of eyeglasses

53. a β Objective Eye piece f o f e Galilean telescope

54. Keplerian telescope f o f e α Objective Eyepiece β

55. 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

56. Magnification of a telescope is given by the formula M = f o / f e Telescopes can be used to focus near objects by changing the distance between objective and ocular lens Increasing the power of the objective lens

57. MONOCULARS MONOCULAR MONO AUTOFOCUS BINOCULARS SPECTACLE MOUNTED

58. See TV Spectacle model Binocular telescope For intermediate distance Wider field of view Cause spatial disorientation Not for mobility tasks

59. NEAR OPTICAL AIDS Spectacles Prismatic ½ eyes Bifocals Magnifiers Hand held vs. stand Illuminated vs. non-illuminated Electronic Devices

60. 5/20/2014 APPROACH & ASSESMENT OF LVC-CME 62 Spectacle magnifier Spectacle magnifier is a spectacle mounted convex lens This uses the principle of relative distance magnification Full fields Half eyes Useful for prolonged reading

61. Advantages & disadvantages of Spectacle magnifier 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

62. 5/20/2014 APPROACH & ASSESMENT OF LVC-CME 64 Stand magnifier 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

63. Stand Magnifiers

64. Advantages & disadvantages of Stand magnifier 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

65. 5/20/2014 APPROACH & ASSESMENT OF LVC-CME 67 Hand held magnifier 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

66. Hand Held Magnifiers

67. Closed circuit television system 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

68. Electronic Magnifiers

69. Non-optical Devices Glare reduction devices Contrast enhancement devices Computer software Accessory devices Talking watches, clocks, etc Writing guides Tactile markers

70. 5/20/2014 APPROACH & ASSESMENT OF LVC-CME 72 7 categories of non - optical devices 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

71. NON OPTICAL DEVICES : 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…

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

73. Signature guide

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

75. Relative size devices 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

76. CPF glasees 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

77. 5/20/2014 APPROACH & ASSESMENT OF LVC-CME 79 Non optical devices

78. 5/20/2014 APPROACH & ASSESMENT OF LVC-CME 80 Even more…

79. Assistive devices'

80. Assistive devices for near Closed circuit television [CCTV] Monitor CCTV Portable CCTV Mouse model CCTV

81. 5/20/2014 APPROACH & ASSESMENT OF LVC-CME 83 Assistive devices for distance ONYX JORDY

82. 5/20/2014 APPROACH & ASSESMENT OF LVC-CME 84 Portable CCTVs BUDDY PLAYER QUICK LOOK ZOOM CLASSMATE READER

83. MN READ ACUITY CHART Mostly used chart for assessing near acuity of a low vision patient. It was developed at Minnesota laboratory for low vision research.

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

85. TO the details…………… Chart Design Measurement Of Reading Acuity Measuring Reading Speed

86. Chart DESIGN: 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.

87. Measuring reading speed 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.

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

89. Remember! “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