Low vision


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  • Low vision

    1. 1. Introduction to low vision
    2. 2. 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
    3. 3. 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
    5. 5.  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
    6. 6. Denial Anger Bargaining Depression Acceptance
    7. 7. 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
    8. 8. • Irreversible damage to ocular media or visual pathway. CHILDREN  Albinism  ROP  Congenital malformation  Optic neuropathy
    9. 9.  Keratoconus  Ocular injuries  Aniridia OLD AGE  ARMD  Cataract  Macular degeneration  Retinal degeneration
    12. 12. Macular Degeneration
    13. 13.  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
    14. 14.  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
    15. 15. Retinopathy
    16. 16.  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
    17. 17. Retinitis Pigmentosa
    18. 18.  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
    19. 19. Glaucoma
    20. 20.  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
    21. 21.  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
    22. 22.  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
    23. 23. Albinism
    24. 24. Central field loss Overall blur Peripheral field loss Functional Effects of Low Vision:
    25. 25.  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
    26. 26. Evaluation  External observation  Detailed history taking  Functional vision assessment  Defining goals of the patient
    27. 27. Management  Trial & selection of LVD  Low vision device training  Counseling
    28. 28. In the waiting area On entering the examination room Mannerisms of the patient Physical appearance Communication skill
    29. 29. Patient details a. Occupation b. Living situation c. General health d. Other limitations e. Family history f. Previous low vision care
    30. 30. Difficulty in visual tasks a. Distance visual tasks b. Near visual tasks c. Computer usage d. Light sensitivity e. Mobility issues f. ADL
    31. 31. Visual acuity Refraction Contrast sensitivity Color vision testing Visual field assessment
    32. 32. 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
    33. 33.  Distance:  Snellen (projection)  Feinbloom/ SOSH  ETDRS  Lea Symbols  Bailey & lovie charts  Near:  MN read acuity chart  Light house near test chart.
    34. 34. Perform retinoscopy instead of auto refractors Calculate just noticeable difference Aim to improve the quality of vision
    35. 35. 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
    36. 36. 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.
    37. 37. Amsler grid: • Assess central VF • Absolute scotoma • Relative scotoma • Metamorphopsia
    38. 38. Confrontation • Assess peripheral VF • Checked in all 4 quadrants • Quick and basic.
    39. 39. 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
    40. 40. 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.
    41. 41. 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)
    42. 42. 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.
    43. 43. Near spectacles Bifocals PAL upto +3. High Asperical lenses +6.00 - +20.00D High Plus Prismatic lens +4.00- +14.00D
    44. 44. Enable copying from the black board Identifying street signs Seeing traffic signals Seeing bus numbers Spot viewing Watching movies in theatre Enjoying sporting events
    45. 45.  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
    46. 46. a β Objective Eye piece fo fe
    47. 47. fo fe α Objective Eyepiec e β
    48. 48.  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
    49. 49.  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
    51. 51.  Spectacles Prismatic ½ eyes Bifocals  Magnifiers Hand held vs. stand Illuminated vs. non-illuminated  Electronic Devices
    52. 52. 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
    53. 53. 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
    54. 54. 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
    55. 55. 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
    56. 56. 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
    57. 57.  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
    58. 58.  Glare reduction devices  Contrast enhancement devices  Computer software  Accessory devices  Talking watches, clocks, etc  Writing guides  Tactile markers
    59. 59. 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
    60. 60.  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…
    61. 61.  Black cards with rectangular cut outs horizontally along the card  The patient can feel the empty cut out spaces and write
    62. 62.  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.
    63. 63.  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
    64. 64. 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
    65. 65. 5/20/2014APPROACH & ASSESMENT OF LVC-CME 79
    66. 66. 5/20/2014APPROACH & ASSESMENT OF LVC-CME 80
    67. 67. Closed circuit television [CCTV] Monitor CCTV Portable CCTV Mouse model CCTV
    70. 70.  Mostly used chart for assessing near acuity of a low vision patient.  It was developed at Minnesota laboratory for low vision research.
    71. 71.  TYPES: 1. Black letters on white background. 2. White letters on black background.  USES: 1. Reading Acuity 2. Critical Print Size 3. Maximum Speed
    72. 72. Chart Design Measurement Of Reading Acuity Measuring Reading Speed
    73. 73. 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.
    74. 74. 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.
    75. 75. Chart Illumination – Luminance at least 80cd/m. Viewing Distance - 40cm Testing Procedure… Calculation formulae: Acuity = 1.4 – (sentences*0.1)+(errors*0.01)
    76. 76.  “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