Visual impairment and low vision

Power point presentation on visual impairment and low vision and their education

1. Visual impairment and low vision BSEd Nusrat Zerin

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3. Visual Acuity: Ability to see "detail" Measured using testing distance / letter size Normal is 20/20 It is a number that indicates the sharpness or clarity of vision. A visual acuity measurement of 20/70 means – a person with 20/70 vision who is 20 feet from an eye chart sees what a person with unimpaired (or 20/20) vision can see from 70 feet away. (after all possible solution and treatment)

4. Visual Acuity: According to WHO- 6/18 = Meter (Distance)/ Size of E (Font size that can be seen from 6 meter distance) 3/60 = Meter (Distance)/ Size of E (Font size that can be seen from 3 meter distance) Normal sight 6/6 to 6/18

5. Visual Field: Visual field is the total area an individual can see without moving the eyes from side to side (in between 180 degree or 170 degree (on average)

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7. ¶ xb`„wói e¨envwiK msÁv t Dchy³ wPwKrmv Ges Pkgvi mvnv‡h ¨ cÖwZmiYRwbZ mgm¨v mgvavb Kivi ciI A‡c¶vK …Z fvj † Pv‡L † Kvb e¨w³i `„ wó kw³i Zx²Zv 6/18 Gi Kg n‡Z Av‡jvi Abyf~wZ ch©šÍ _ vK‡j Ges `„ wó ‡¶Î 10 Gi Kg n‡j - Zv‡K ¶ xY `„ wó ev † jv wfkb ejv n‡e , Z‡e `„ wó kw³i e¨envi K‡i † Kvb KvR Kivi mvg _©¨ Zvi _ vK‡Z n‡e | ( Management of Low Vision in Children, WHO/PBL/93.37 )| m¤ú~Y © `„ wónxbZvi e¨envwiK msÁv t ‡ Pv‡L Kvh©Ki Av‡jvi Abyf‚wZ bv _ vK‡j Zv‡K m¤ú~Y © `„ wónxbZv e‡j |

8. "Legal blindness" - definition developed by the US govt. to determine eligibility for vocational training, rehab., schooling, disability benefits, low vision devices & tax exemption programs. It's not a functional low vision definition  and doesn't tell us about what a person can and cannot see . A visual acuity of 20/200 or less in the better-seeing eye with best conventional correction visual field of 20 degrees or less (also called tunnel vision) in the better-seeing eye . Low vision   is a condition caused by eye disease, in which visual acuity is 20/70 or poorer in the better-seeing eye and cannot be corrected or improved with regular eyeglasses. 

9. দৃষ্টিপ্রতিবন্ধিতা ( visual impairment ): ( cÖwZeÜx e¨w³‡`i AwaKvi I myiÿv AvBb 2013) নিম্নবর্ণিত দফাসমূহে উ‡লjøখিত বৈশিষ্ট্যসমূহের মধ্যে এক বা একাধিক বৈশিষ্ট্যের অধিকারী ব্যক্তি , দৃষ্টিপ্রতিবন্ধী ব্যক্তি বলিয়া বিবেচিত হইবেন , যথা : ( ক) সম্পূর্ণ দৃষ্টিহীনতা ( blindness ): (অ) উভয় চোখে একেবারেই দেখিতে না পারা ; বা (আ) যথাযথ লেন্স ব্যবহারের পরও দৃষ্টি তীক্ষ্ণতা ( visual acuity ) ৬/৬০ বা ২০/২০০ এর কম ; বা (ই) দৃষ্টি ক্ষেত্র ( visual field ) ২০ ডিগ্রী বা উহার চাইতে কম ; ( খ) আংশিক দৃষ্টিহীনতা ( partial blindness), যথা : − এক চোখে একেবারেই দেখিতে না পারা ; ( গ) ক্ষ্ণীনদৃষ্টি ( low vision ): (অ) উভয় চোখে আংশিক বা কম দেখিতে পারা ; বা (আ) যথাযথ লেন্স ব্যবহারের পরও দৃষ্টি তীক্ষ্ণতা ( visual acuity ) ৬/১৮ বা ২০/৬০ এবং ৬/৬০ বা ২০/২০০ এর মধ্যে ; বা (ই) দৃষ্টি ক্ষেত্র ( visual field ) ২০ ডিগ্রী হইতে ৪০ ডিগ্রীর মধ্যে ।

10. Anatomy of Eye Outer eye: Eyelid, eyelashes Inner eye: Eye ball, optic nerve

11. Three different layers of eye: The external layer - Sclera (white & gives eye it’s shape) The intermediate layer – Choroid (contains blood vessel) 3. The internal layer - Retina the sensory part of the eye

12. The eye has a number of components Sclera choroid Retina Conjunctiva Cornea Iris Pupil Lens Macula optic nerve Vitreous body Aqueous body Optic nerve

13. Three chambers of fluid :  Anterior chamber  (between cornea and iris) Posterior chamber  (between iris and lens) Vitreous chamber  (between the lens and the retina). The first two chambers are filled with aqueous humor the vitreous chamber is filled with a more sticky fluid, the vitreous humor.

14. Cornea : clear front window of the eye that transmits and main function is refraction & transfer light into the eye, . Conjunctiva: transparent layer covers cornea and sclera, contribute to tear production & protect eye from infection Iris: colored cell of the eye that helps regulate the amount of light that enters Pupil: dark aperture/hole in the iris that determines how much light is let into the eye (adjust light entry) Ciliary body: joins Iris with Choroid & makes aqueous humour Lens: transparent structure inside the eye that focuses light rays onto the retina Retina: nerve layer that lines the back of the eye, senses light, and creates electrical impulses that travel through the optic nerve to the brain Macula: small  central  area in the retina that contains special light-sensitive cells and allows us to see fine details clearly Optic nerve: connects the eye to the brain and carries the electrical impulses formed by the retina to the visual  cortex  of the brain Vitreous: clear, jelly-like substance that fills the middle of the eye

15. my¯’¨ † Pv‡Li 6wU wPý ev jÿY   † PvL mwVKfv‡e Lyj‡Z I eÜ Ki‡Z cvi‡e ; KbRvswUfv ¯^”Q/ cwi ¯‹vi n‡Z n‡e ; KwY©qv ¯^”Q n‡Z n‡e ; wcDwcj Kv‡jv , † MvjvKvi Ges ` yB † Pv‡L GKB AvKv‡ii n‡Z n‡e ; † Pv‡Li bovPov ¯^ vfvweK n‡Z n‡e Ges `„ wó fvj n‡Z n‡e |

16. How we see-

17. Vision problems: Myopia: Myopia  (nearsightedness) is a refractive error, which means the eye does not bend or refract light properly.   2. Hyperopia: Hyperopia  (farsightedness), is a refractive error, which means that the eye does not bend or refract light properly to a single focus to see images. It occurs when the eye is shorter than normal or has a cornea (clear front window of the eye) that is too flat . 3. Astigmatism: Astigmatism is an imperfection in the curvature of your cornea — the clear, round dome covering the eye's iris and pupil — or in the shape of the eye's lens. 

18. Causes of vision loss - Congenital - Disease (Cataract, vit A deficiency, myopia, hyperopia, astigmatism, lazy eye, albinism, Glaucoma, Trachoma, dry eye, diabetic retinopathy, Retinitis pigmentosa ) - Accidents / trauma

19. Types of vision loss Total blind Low vision

20. Low vision devices: Tools that help those with vision loss maximize their remaining vision and these devices are: Optical Non Optical Electronic devices

21. Check that each person has been examined to see if spectacles are needed to correct /improve vision before recommending low vision devices . Before selecting a low vision device consider: size of objects to be viewed possible viewing distance from the object length of time needed for activity Whether one / both hands are needed for activity

22. Optical devices are – Near: These are designed for magnifying close objects & print. Spectacles Magnifiers – Hand held & Stand magnifiers, illuminated magnifiers 2. Distance: These are for magnifying things in the distance (from 3 metres to far away ). Monocular Binocular Telescope 3. Electronic devices: CCTV or video magnifier

23. Optical devices are – Near: These are designed for magnifying close objects & print. Spectacles Magnifiers – Hand held & Stand magnifiers, illuminated magnifiers (Dome, Bar, Sheet magnifiers) 2. Distance: These are for magnifying things in the distance (from 3 metres to far away ). Monocular Binocular Telescope 3. Electronic devices

24. Optical devices for near tasks Magnifiers for near tasks can be used for: reading a book or a newspaper reading labels, signs or prices in shops using tools, for example measuring threading a needle identifying money inspecting objects such as plants or insects For reading, the magnifier has to be moved along each line of print, sometimes only showing a word or part of a word at a time. More words will be seen if the eye is held close to the magnifier. Reading is very slow at first. It is difficult to learn to use the magnifier properly - a lot of practice is needed.

25. 1. Uses: for reading any material writing looking at objects from close range 2 . Advantages: range of magnification both hands free readily available- e.g."cataract " glasses can be used as reading glasses once used efficiently, can be used for long periods 3. Disadvantages: exact reading distance important Short reading distance with high powered lenses more fragile than magnifiers (scratching, breaking) Bad lighting at close distance stress eye Without reading stand to bring material close to eye is difficult

26. Hand Magnifiers 1. Uses: reading signs, labels, prices, books identifying money inspecting objects such as plants or insects handwriting 2. Advantages: easy to carry available from low to high power Less expensive can be used in any position or angle Illuminated magnifiers allows light onto print or objects 3. Disadvantages: difficult to keep appropriate distance one hand occupied difficult to hold steady

27. Stand Magnifiers A stand magnifier is a strong lens which is mounted in a plastic stand. A stand magnifier is usually easier than a hand held magnifier for a child to use. 1. Uses Reading from a book or newspaper Looking at a picture or diagram 2. Advantages Has a fixed distance for ease of movement Easy to use Available from low to high power magnification Allows light onto print if legs thin and tapered or clear 3. Disadvantages Keeps one hand occupied Not useful for activities like writing Poor posture (bending above lens) Causes fatigue

28. Optical devices for Distance task Magnifiers for distance are like small telescopes. They improve the ability to see distant objects or people. Objects appear to be closer and it is hard to judge distances properly. It is best not to use telescopes while walking around. Telescopes Telescopes can be used for looking at distant objects and activities such as: signs finding and recognizing people/animals Reading in school from blackboard finding an entrance to a building watching games .

29. 1. Uses Reading from a blackboard from a distance >2 /3m Looking at objects you cannot get close to, e.g. top of a tree, animals 2. Advantages Makes distant objects appear closer Can be used in a classroom for blackboard reading or outdoors 3 . Disadvantages Requires very good contrast Takes time to: Find text on blackboard and read Write notes down, possibly using other low vision device Expensive to make Not easy to use, requires extensive training

30. Training to use optical devices Encouragement and training are needed for people to use low vision devices well. The field of view or amount through magnifier or telescope is small. It takes practice to be able to find objects and then follow them or scan to find other objects. For distance tasks it is best to look in the general direction of an object without the device and then point or place the device in that direction to locate objects. It is easier to scan along horizontal objects such as roads or fences and up and down vertical objects such as trees or walls . Do not just give out magnifying glasses, if there is no one to train the person in its use. A person will often reject the device, because they do not know how to see better with it. Training in the use of all magnifying devices is vital

31. Non Optical devices: Reading stand Felt tipped pen, markers Sun glasses/filter glasses Caps/Sun visors Table lamps

32. Education materials Total blind: Braille and stylus - Electronic Braille note taker Brailler /Braillewriters Braille Printers For math (Taylor board, abacus, Geometry set)

33. For low vision: Typo scope/Reading guide Writing guide Reading stand Signature guide Portable type electronic typoscope

34. For mobility White cane Sighted guide technique Independent movement technique Guide dog

35. Plus curriculum Orientation and mobility Sensory training (touch, smell, hear, taste) Assistive technology- Computer technology (screen reader software, magnification software, JAWS, dolphin, NVDIA etc.)