Low Vision Midterm Review Notes PDF

LOW VISION: DEFINITIONS: ◦VISUAL IMPAIRMENT: ‣ Functional limitation of the eye or visual system - may include reduced VA, CS, VF, photophobia, diplopia, distortion, visual perceptual Ex) 20/20 pt who is not happy with their vision Ex) 20/70 patient who is a bus driver and is having problems passing...

LOW VISION: DEFINITIONS: ◦VISUAL IMPAIRMENT: ‣ Functional limitation of the eye or visual system - may include reduced VA, CS, VF, photophobia, diplopia, distortion, visual perceptual Ex) 20/20 pt who is not happy with their vision Ex) 20/70 patient who is a bus driver and is having problems passing driving exam Functional complaints that affect their daily activities Any acuity level that affects the individuals ability to ex) read mail, watch TV, driving, using computer, work tasks ◦VISUAL DISABILITY: ‣ Limitation of the abilities of the individual to perform specific tasks that results from an impairment ◦VISUAL HANDICAP: ‣ Loss of personal independence resulting from vision loss; person’s disadvantages position in society, resulting from impairment and disability ◦LOW VISION: ‣ Significant reduction of visual function that cannot be fully corrected by ordinary gls, CL, TX or SX ‣ 2 categories —> for every 1 legally blind there are 3 more who are visually impaired Visual impairment Legal blindness ‣ implies a functional loss of vision ‣ Low vision is NOT the same as legal blindness When vision loss is not correctable with traditional gls or CL that affects a patient’s visual function ◦LEGAL BLINDNESS: ‣ Determined by SSA - enables those who qualify to receive disability pay 0 ‣ 20/200 or worse in the BETTER seeing eye ‣ VF defect where the WIDEST diameter of the field is no greater than 20 degrees in the BETTER seeing eye better TYPES OF PATIENTS - demographic tends to be elderly Caucasian {females} (currently Baby Boomers): seeing Baby Boomers: ◦Decreased VA ◦Working longer ◦Decreased VF ◦Living longer ◦More overweight ◦Decreased CS ◦Women living alone ◦MOST COMMON CAUSE OF IMPAIRMENT = AMD, DR, CATARACTS, GLAUCOMA ‣ Disease Process w/ Stroke and TBI Leading cause of disability and leading PREVENTABLE cause of disability #5 killer in the US ◦DIABETES: ‣ 30 million in USA ‣ 39 million in USA w/ low vision ODs ARE THE BEST SUITED TO TREAT LV PATIENTS —> D/T KNOWLEDGE OF OPTICS ◦Introduction at diagnosis w/ pt education ◦Give resources/referral ◦Levels of low vision service: ‣ Basic = 20/40 to 20/70 Initiate low vision Consider FILTERS and HIGH ADDS ‣ Intermediate = 20/70 to 20/200 Hand held magnifies Low powered molecular Eccentric viewing Refer to certified low vision therapists ‣ Advanced > 20/200 High powered monoculars / telescopes Electronic magnifying systems Certified orientation and mobility training LOW VISION EVAL: STEP 1: welcome and comfort (lift step on ◦Prior to exam —> SIGHTED GUIDE to escort visually impaired pt to the exam room/destination chair, lighting, help w/ mobility cane —> never ‣ Orientation and Mobility techniques needed for PERIPHERAL VF LOSS move their items) ◦Observation STEP 2: introduce others in the room STEP 3: ask if LV exam before and how it ‣ Clues of grooming needs/self care —> dressed neatly vs. soiled clothing differs ‣ Clues of emotional status STEP 4: ask if they have records with them ‣ Patient movement into and about the exam room —> mobility issues 2’ to VF loss vs. STEP 5: assess if family member is helpful or hurtful neurological issues STEP 6: put patient at ease ◦Detailed case history ‣ Emphasis on patient’s life performance ‣ Determine goals to help patients do the things they now cannot do b/c of vision loss ‣ Medical info Tremors (neuro), psychological, cognition Medications and physical limitations (wheelchair) ‣ Rehab/Psychological side —> exam becomes a counseling appointment ‣ Ask further questions from primary care exam: ie Ysf eye Living situation (spouse, family, care giver) Previous device used Goals ◦@ distance, intermediate and near ◦functional goals ◦AVOID VAGUE GOALS Current use of vision w/ Visual functioning questionnaire ‣ Intake analysis: Present level of utilization of residual vision (how well have they adapted, gradual vs. sudden vision loss, trying to use vision or having others help them) ‣ PEARLS: Explanation of exam procedure Communication Managing expectations Reassurance is key Typically there is a device that will help ◦80% of patients with vision loss have some form of useable vision ◦Functional assessment ◦Goal determination ◦Patient education ◦VA ‣ Distance (never use counting fingers) —> Move chart to them or walk up to chart TEST DISTANCE / LETTER SIZE ◦Quantify vision loss to aid them in receiving services, benefits and independence ◦Easy functional vision = pt response is confident and quick ◦Hard functional vision = pt slows and struggles VA centrally Illumination VF status Functional assessment: ◦VA measures vision based on high contrast and determines if vision is changing ◦Low vision charts test patients in eccentric viewing position and closer to patient b/c movable Types of charts (projector, printed acuity, back illuminated charts) ◦SNELLEN: ‣ Most common ‣ NOT recommended for low vision —> only use if VA is 20/40 or better ‣ Chart illumination is fixed ‣ Poor contrast as it varies ‣ Large gradations/jumps in Optotypes —> small VA is over represented Sometimes using Snellen alone can cause someone to lose driving privileges prematurely Cause overprescribing of power —> overestimate mag = decrease FOV —> pt to become dependent on the higher mag even if they do not need it ‣ Calibrated that letter subtends 5’ of arc ◦FEINBLOOM CHART: ‣ Typically tested at 10 ft ‣ Available to 1) eccentric view 2) move closer 3) go smaller (if VF peripheral loss) ‣ Has more steps in optotype but unable to measure lower VA’s ◦MODIFIED ETDRS (Bailey-Lovie) CHART: ‣ Distance Log MAR chart (2 or 4 meters) Minimum angle of resolution (MAR) Geometric progression of letter size by a factor of 1.26x Each row is equally difficult (5 letters / row = 0.1logMAR) Each letter is scored in 0.02 logMAR —> correct = SUBTRACT 0.02 LOWER logMAR = better VA —> logMAR = 1.0 = 20/20 Letter spacing is proportional PEARLS: ◦Watch patient, no the chart ◦Encourage eccentric viewing ◦Letter isolation ◦Illumination ◦Take disease into consideration ‣ Near Types of near charts/cards (SINGLE LETTER: reduced Snellen, Meter (M) lighthouse, reduced ETDRS chart) vs. (WORD TEXT: Jäegar chart, lighthouse game, MNRead cart) —> TEST BOTH! singleutter wordtext ◦REDUCED SNELLEN: ‣ Angular measure of acuity based on a SET DISTANCE of 40cm ‣ NOT recommended for low vision —> rarely tests at 40cm ‣ Serif vs. Sloan letter ‣ Inconsistent spacing of letters and lines —> crowding effect = bad for those with central loss ‣ Need a notation method that is independent of testing distance O A O 0 ◦M NOTATION: ‣ 1M size letter subtends an angle of 5 minutes of art at 1 meter STEP 1: test near VA w/ current RX and any low vision aids Linear size is 1.45mm STEP 2: add light over bettter seeing eye ‣ 1m/1M = 20/20 Snellen equivalent STEP 3: measure working distance ‣ TEST DISTANCE / LETTER SIZE STEP 4: eccentric viewing position STEP 5: record functionality ‣ LogMAR spacing of letters and lines —> results in the visual angle on the chart have doubling every three lines = DOUBLING EFFECT ‣ M is INdependent of working distance ◦REDUCED ETDRS CHART: ‣ Maintainers 5 letters in each rose, can be used at any distance ‣ Get smaller spacing at higher acuities = CROWDING EFFECT NOT to be used with central scotoma ‣ LogMAR spacing of letters and lines —> results in the visual angle on the chart doubling every three lines = DOUBLING EFFECT ◦CONTINUOUS WORD/TEXT: ‣ Assess reading speeds —> good for baseline before eccentric viewing training ‣ Determine literacy ‣ Tests real life function ‣ Average person = 200-400 words/min ‣ Checks for crowding issues w/ tracking, scanning or single letter localization Scotomas can cause problems here ‣ Test OU first, then monocular to see if reading speed improves/changes ‣ MNRead card is considered GOLD STANDARD readingspeed Printed in high contrast or negative polarity (good for contrast/glare issue patients) = (glaucoma, reading keratoconus, albinism) Measures 1) Max reading speed 2) critical print size 3) threshold VA ◦The reading speed they start off with is their maximum reading speed while maintaining ◦As patient gets closer to threshold their reading speed drops vending speed ◦Smallest print size patient can react that their maximum reading speed = critical print size SMALLEST TRESHOLD ◦Smallest print read at the slowest speed = threshold VA Common letter size equivalents: SLOWEST ◦Bible = 0.5M SPEED Acuity conversations: ◦Newsprint = 0.8-1M 20150 MAR to logMAR ◦Large print = 2-3M LogMAR to Snellen M to point notation 8 Things Needed for Near acuity: RECORDING ◦1M = 8 points ◦Eye tested Snellen to Decimal acuity ◦Device name (cc or sc) ◦Snellen fraction in decimal form ◦Test distance measured ◦Size of the letters/words ◦Type of target/chart ◦Description of reading (accurate, slow, missed words) ◦EV position ◦Illumination level PEARLS: ◦Pt to hold card where comfortable (make sure to measure WD) ◦Test worse eye first ◦If reading speed improved w/ monocular viewing of good eye = rivalry ‣ WHAT CHART DO YOU CHOOSE? Central field loss ◦Better with single letter —> depends on scotoma size Peripheral/constricted field loss ◦Lighthouse or ETDRS is best Hemianopic field loss ◦Usually omit the side they have lost ‣ WHAT ILLUMINATION? AMD and RP perform best under glare free BRIGHT light Rod/cone monochromatic or cone abnormalities need LESS/DIM LIGHT Place lamp behind patient over better eye reading material and vary the intensity until patient is comfortable ‣ EXTRA TOOLS? Typoscope = black square with reading window to ISOLATE letters and minimize noise Yellow filter = enhances contrast and reduces glare ◦VF ◦CS ◦TRIAL FRAME REFRACTION ‣ Importance: Many patients have not been refracted for awhile —> children w/ congenital disorders may need extra careful refraction because they have received a shorter primary care exam Done to ensure patient has best acuity with traditional correction Not uncommon to have very high RE c Don th BUFFET Max initial WALpintsize print mm VA F p print Im I o ‣ BASELINE: Current Rx (not really current in low vision since RX can be outdated and may be wearing someone else’s gls) Keratometry w/ Topographer (Pentacam) ◦Measures amount and axis of corneal toxicity to estimate amount of astigmatism ‣ Useful in albinism, keratoconus, aniridia, congenital pendular nystagmus For nystagmus, position in null point and do not use occlusion if nystagmus increases monocularly Retinoscopy ◦Objective measure —> use with trial frames NOT phoropter ◦Gives info about 1) clarity of media (opacified, cataract) 2) type and level of RE 3) helpful if pt unable to give reliable responses (pediatrics, stroke/TBI) Radical Retinoscopy ◦Performed at a closer working distance ◦Can work off axis to get around opacities (might change your axis during refraction) ‣ If patient has extreme EV/PRL —> prescribe off-axis cylinder Over Retinoscopy ◦Used when patient has high RE ◦Will be starting point for refraction ◦Can ret over the glasses of go straight into your refraction ◦When finished, measure resultant back vertex power using phoropter ‣ AVOID PHOROPTER: Not useful for low vision patients Limits: ◦Patient head position ◦Field of view ◦Vertex distance hard to adjust when have larger prescriptions ◦Amount of change between lens choices +/- 0.25 steps: ◦Average person VA is 20/20 ◦Amount of change a person with 20/20 vision is +/- 0.25 —> JND designed for normal vision ‣ TRIAL FRAME IS THE TOOL OF CHOICE! Advantages: ◦Wider lens to view through ◦Dampen nystagmus w/ head position directing gaze to null point ◦Make large lens changes ◦Handheld JCC is high powers to accommodate larger JNDs ◦Check near acuities in more natural position ◦Can compare TF Rx with old RX ◦Can show patients how glasses can or can’t help ◦Can see visual expressions when dipping lenses ◦Can see eccentric viewing ◦Telescopes and other devices can later be incorporated ◦Creates a more real-life vertex distance Challenges: ◦ADVANCED refractions —> NOT 92015 code —> LV1/LV2 and a non-covered service ◦High rx ‣ High plus = APHAKIA ‣ High minus = MYOPIC DEGNERATION ◦No obvious endpoint ‣ Things are blurry and will never be crisp ‣ Good to listen to how quick they respond ◦Cannot predict RX based on acuity ◦Patient beliefs and misconceptions ◦Take working distance of the chart into account ‣ Ex. 10’ chart has how much divergent light coming off? 10’ = 3.3meters —> 1/3.3m = -0.33D Need to put in +0.33D to RX to neutralize light prior to refraction ‣ 5 KEY COMPONENTS: Color Contrast LARGE TEXT WITH HIGH CONTRAST IS BEST! Magnification Field of view Lighting ◦FULL room illumination = RP AMD ◦DIM room illumination = Anaridia ◦Make sure to select a chart with proper illumination and no hot spots/glare ‣ STEPS TO TRIAL FRAME: Pre-adjust w/ monocular PD, panto tilt, place eyes in center of the lens wells, orient lens wells to slide in and out easily, patient education w/ weight and expectations, place TF onto patient and make further adjustments Obtain starting point Occlude 1 eye/blur I É O Check VA JND = Snellen letter size Anatomy of JCC: Obtain threshold VA 100 Combo of 2 cyl of equal Determine JND —> ALWAYS ROUND UP strength but opposite signs Introduce JND lenses while looking 1 line above threshold *demonstrate by taking 1/2 of JND on either side placed with their axes 90 Ex. JND = 2.00D —> use +/-1.00D lenses degrees apart Place preferred sph into lens well Recheck acuity Repeat until no improvement in VA Use last threshold VA to determine JND and the JCC to use ◦Ex. VA = 20/100 —> JND = 1.00 —> use +/-0.50 cyl Binocular Balance: Demonstrate JCC + fish for cyl —> CHASE THE RED Many patients are presbyopia If accepted place preferred cyl lens into lens well Unequal acuities Recheck VA RARELY DO THIS IN LOW VISION ◦Ex. OD 20/40 OS 20/60 = do the BB Refine axis ◦Ex. OD 20/100 OS 20/30 = AVOID BB Refine cyl Continue until ‘no difference’ Could check ocular dominance Recheck sph Compare to current and document which one patients likes better ‣ PEARLS: MINUS lens first Show difference between trial frame and glasses Raasch dots ◦Device evaluation ◦Formulate plan and make appropriate referrals I D GLARE, LIGHTING, CONTRAST AND FILTERS ◦Visual acuity and function: ‣ Acuity measures quantity ‣ Contrast measures quality More complete measure of functional vision Important test to aid in devices ‣ We do not function in a high contrast world —> but test patients with high contrast charts to determine the BEST acuity for a patient ◦Lighting: ‣ Important but too much of a good thing can be bad ‣ Patient subjective Ex. 60yo retina receives 1/3 the light of a 20yo retina ‣ Good lighting can enhance contrast —> but TOO much light can cause you to lose contrast Ex. Too much light = glare, washed out, uncomfortable ‣ Needs to be focused (aka task lighting) ‣ Old theory says 60-100 watts vs. today’s theory that BRIGHTNESS (lumen) and COLOR (kelvin) matter Illumination: ◦Luminous flux = amount of light emitted by a light source ‣ Measured in lumen = BRIGHTNESS ◦Follows the inverse square law ‣ Light source emits luminous flux to illuminate a work space set to a certain distance ‣ Illuminance of that object is inversely proportional to the square of the distance the light source is from the object Ex. If the distance doubles closer to object, what happens to the illuminated area? MORE illumination ‣ GOAL: most intense light source placed perpendicular and as close as possible to the task without creating a hot spot Color: ◦Measured in kelvin ◦Incandescent light: ‣ Most common household light ‣ Gives off WARM light of long wavelengths ‣ Gives off a lot of heat ‣ Luxocombo lamp ◦Halogen lamp: ‣ Need to change w/ tissue —> CANNOT touch it ◦Fluorescent lamp: ‣ Gives off COOL light of short wavelengths (more blue) ◦LED: ‣ Daylight lamp give off wavelengths similar to natural sunlight/full spectrum lights Increases contrast Increases clarity Reduces glare Most environmentally friendly Safest light for partially sighed people Most comfortable light for eyes ‣ Record in low vision exam chart: Reading material Location of light —> usually over dominant/better seeing eye LED Brightness of light Color of light Pt appreciation for certain light setting ‣ Lighting PROBLEMS: GLARE: ◦3 Types (assess IN ORDER) ‣ Discomfort glare Related to PERIPHERAL FIELDS and confusion in the visual system ◦Ex. Pt facing the sun but needs to see sidewalk that is shaded —> pupil constricts but also needs to dilate Need to have at least 10 degree radius of superior or temporal VF to experience problems Worse in late morning and early afternoon Pt may squint or use hand as visor TX: ◦Translucent side shields on frames ◦Visor/hat that can be positioned low to the brow w/ rim that extends 3 inches ◦AVOID sunglasses ‣ Disability glare (AKA veiling glare) Random, stray light Depends on the short visible wavelengths b/c these scatter the most Occurs in OCULAR MEDIA OPACITIES Looks like driving through fog with headlights Observe severity by the squint reflex TX: ◦Fix media opacity ◦Wear visor ◦Tilted lenses or polarized ◦MILD = Light yellow tint (blocks up to 475 / blue light) ◦MODERATE = light orange tint (blocks up to 525) bluegreen ◦SEVERE = light red tint (blocks up to 575) green ‣ Dazzling glare Pt has PHOTOPHOBIA Problem with iris or retina Occurs: ◦Retinal neurons form lateral pathways w/ horizontal and amacrine cells ◦They control the retinal info and modify the neural transmission intensity of light to the brain ◦Damage to these disables the eye’s ability to modify light intensity resulting in photophobia TX: ◦Address discomfort and disability/veining glare first ◦Assess for overcast and sunny days ◦Let pt adapt for 7 min to lighting condition ◦Opaque CL or tints —> goal to try and keep total light transmission (TLT) as high as pt can tolerate ◦MILD = use high range (90-95%) TLT lens ◦MODERATE = 49-20% TLT ◦SEVERE = 19-1% TLT ◦AR can also cut glare and increase light transmission ◦FILTER ASSESSMENT for GLARE: ‣ Have pt put lenses on BEFORE they go outside ‣ Looking for the patient to have very little to no adaptation time ‣ Yellow, orange, plum and amber usually ENHANCE CONTRAST ◦Contrast: ‣ Pelli Robson Chart (tested at luminance level of 85 cd/m) 16 triplets of Sloan letters ◦Each triplet has the same contrast —> decreases by 0.1log unit Each subtends 0.5 degrees at 3 meters —> LV tests at 1 meter —> account for working distance Healthy 20yo = 1.65 ◦Pt can read 6-8 lines = slightly reduced/normal ◦Pt can read 4-5 lines = moderately reduced ◦Pt can read 1-3 lines = profoundly reduced/severe ‣ MARS card: Handheld test @ 40-50cm distance 0.04 log unit decrease PER LETTER Test continues until 2 consecutive errors ◦Score = CS last letter - 0.04 each incorrect letter ‣ Ways to ENHANCE CONTRAST: Yellow, orange, plum and amber usually ENHANCE CONTRAST’ Create high contrasting spaces Black print on white or yellow papers CCTV in negative polarity Enhance lighting + cut glare a LOW VISION MAGNIFICATION: ◦MAGNIFICATION: ‣ Spreading the image over a larger portion of the retina ‣ 1. RELATIVE DISTANCE MAG: Moving an object closer ‣ 2. RELATIVE SIZE MAG: Physically increasing the print size ‣ 3. ANGULAR MAG: Increasing the angular subtends of an image entering the eye ‣ GOAL: match the patient’s visual threshold with their visual demand —> merge what the patient can see with what they need to see ‣ M-notation: 1M = print size subtends 5’ of arc at 1 meter 20/20 = optotype that subtends 5’ of arc ◦@ 20 feet —> a 20/20 sized letter must be 8.73mm tall to subtend 5’ of arc ◦VA = TEST DISTANCE (ft) / LETTER SIZE (ft) or VA = working distance (meters) / letter size (M) ‣ Do NOT mix feet w/ m-notation SNELLEN 1 E 15 20ft 1 20ft 6m tan 5 mnotation or 1 degree E y5 in 112th of ble 5 of E I 6m X X 873mm am E T 1.45mm É 6 Wtt 8 1.45mm my ArEblc1.456 ‣ Other ways to express NEAR acuities: Angular Equivalent Reduced Snellen ◦TD / LS = 20 / x Absolute Size Reduced Snellen (@ 40cm) ◦1M = 20/50 Font Size ◦1M = 8 pt Height ◦1M = 1.454mm ◦Back to MAG: ‣ M = Image / Object 0ÉIm 2 Y IM20150 Im opt 8.73mm 20soo x 500 5012.57 125 20ha 812.57 2opt IM1.45 14512.53.625mm Wh I Y.it 6.667 0m57 to May aims umm g 2x e zoom ‣ Effective Mag: Relative to a specific distance Object must be at the primary focal point of a PLUS lens Clinically relevant Conventional Mag: ◦Typically how magnifiers are labeled ◦Reference point is ALWAYS 25cm ◦Mag = power / 4 ◦Ex. 20D IHHM (5x) ◦Manufacture Mag has +1x f Or my ‣ Equivalent Viewing Distance (EVD): The distance at which an individual must hold an object to get the required magnification Yo 4,7 ym z 1g 2xcloser 4m near VA Em 2m zoom ‣ Equivalent Viewing Power (EVP): Dioptric value required to produce a clear retinal image of desired magnification Inverse of EVD EVP = 1 / EVD ‣ Enlargement Ratio: Image to object size relationship Can also relate working distances ER = original test distance / EVD —> same as apparent mag ER FI ERE Evetyp Eup m Fun HOD ‣ Hand Magnifiers: PLUS lens Magnification is constant regardless of eye position —> will affect the field of view but will NOT affect the mag Object is placed at the primary focal point ADD is not required to view through HHM —> use distance RX ◦B/c rays leave parallel Conventional mag is unchanged ‣ Fields of View: May l Smallest a when z is rat t May APPARANT 15 40cm Ex 5am A trio rat when held IFe F ThroughDist Ig EyD 6.25am FeFm Fa I 41 5x magnifier gls I NEAR Fe Fm Fa FmFake Through Fm Fake Fe 16 2.50 1412.50 oops Fe 16D Fe 16 250 2.501 Fe 16 2.50 166.502.10 Fe 16 2.50 4 Fe 14.50D Ego127 2 0 Yo 4,1m Xm 2m Im 20150 1g Ifm 5D NEAR 2x closer É EUD zoom EUP ‣ Stand Magnifiers: Designed for object to rest within the focal point Requires ADD ◦Light leaving DIVERGENT ◦Compound magnifying system ◦Mag depends on z = eye to lens separation Mag Ifp 1 5cm l ADD Ie 0.2 I If ◦TELESCOPES: ‣ DISTANCE GOALS Driving, TV, seeing faces, reading signs Hand held Bioptic w/ spectacle mounted Telemicroscopes for INTERMEDIATE distance —> requires a reading cap + telescope ◦Increase working distance ◦Decreased FOV ‣ Allows for increased retinal image size without changing the working distance Advantages: ◦Light ◦Inexpensive ◦Quick spotting tasks Disadvantages: OBEY ◦Restricted FOV ◦Requires training ◦Typically not for MOBILITY ‣ ANATOMY: Objective lens = a ◦Entrance pupil = limiting aperture of system Eye Piece lens = b ◦Aka ocular Tube length = c Exit pupil = d ◦Image of objective lens formed by the eyepiece lens ‣ EP diameter = objective lens diameter / mag of telescope ‣ Labeling: Ex. 4x12 0 200 zoom ADD ADD may 4 z 3.33D ex OmarEerie Effin l insidetelescope TUBELENGTH ◦4x is the mag ◦12 is the objective lens diameter in mm ◦Exit pupil = 12 / 4 = 3mm ‣ TYPES: GALILEAN ◦(+) objective ◦(-) ocular / eye piece Afgood ◦EXIT PUPIL is INSIDE the telescope Hyperopes uncorrected ◦Shorter tube length ◦MYOPES: ‣ Neutralizes uncorrected eye —> reduces eyepiece —> reduces mag ◦HYPEROPES: ‣ Adds minus from uncorrected eye —> strengthens eyepiece —> increases mag KEPLERIAN (astronomical) ◦(+) objective ◦(+) ocular / eye piece ◦EXIT PUPIL is OUTSIDE the telescope good UncorrectedMYOPES ◦Longer tube length ◦Image is inverted —> requires erecting prism ◦MYOPES: ‣ Adds plus from uncorrected eye —> strengthens eyepiece —> increases mag ◦HYPEROPES; ‣ Neutralizes uncorrected eye —> reduces eyepiece —> reduces mag ‣ Effects of Ametropia: 3 ways of correcting: ◦1) adding the full refractive correction to the eyepiece = give gls ◦2) adding partial refractive correction to the objective ◦3) changing the telescope length = focal telescope ‣ VERGENCE AMPLIFICATION: Vergence is amplified passing through the telescope Users accommodation is insufficient to clear retinal image —> focusing is required L’ = L x mag^2 Acutual accommodation = mag^2 x expected accommodation Mag = - Feye Fobj Tube = 1 + 1 Fobj 0 far 8 for I OPPOSITE NEAR VISION AIDS: MICROSCOPES + LOUPES ◦Eccentric viewing (EV) = patients perspective ◦(PRL) = doctor’s perspective RESEARCH SHOWS BIGGEST FOV ◦HANDS FREE: AND READING EFFICIENCY IS ‣ Microscopes —> basically high power reading glasses WITH A PAIR OF GLASSES = Must use at a close working distance MICROSCOPE!!!! Binocular or monocular Trailered to patient or premade PLUS lenses that use relative distance mag ◦Object held at the focal length of the lens will have a clear, up magnified image on the retina ◦Closer to eye = larger retinal image = need an add to focus the divergent light Types: ◦Full field: ‣ Spherical Biconvex or Plano convex As the lens power increase, peripheral distortion increases Used up to +8D ‣ Aspheric Minimize peripheral aberrations by reducing the power progressively toward the edge of the lens Full diameter: Used +10 to +20D Lenticular / fried egg: used +10 to +48D ‣ Doublets best Two thin lenses separated by an air space limiting peripheraldistortion Allows for high mag w/ less peripheral distortion Available in mag for 2-20X but are especially useful in powers of 5X and above ◦Half eye ‣ Provide unobstructed, uncorrected distance viewing ‣ Good for mobility ‣ Used +4 to +12D ‣ Base IN prism incorporated to maintain binocularity by reducing convergence demand ◦Bifocals ‣ Allows for corrected distance and near viewing ‣ Good for mobility w/ short spotting tasks ‣ Smaller FOV ‣ Loupes Variation of microscope w/ extended working distance by mounting the lens further away from the spectacle plane A for Feye Smaller FOV than spectacle micro but larger than bifocal Lens creates erect, virtual image Good for mobility Consider when: ◦Need hands free system ◦Portable + flexible ◦Wider FOV ◦Long term reading ◦Faster reading speeds ◦Complete near tasks ◦Teach them they need good lighting ◦HAND HELD: ‣ Hand magnifiers ‣ Stand magnifiers ‣ Electronic aids ◦LIMITATIONS OF MICROSCOPES: ‣ More mag needed = closer working distance ‣ Fixed WD that is unforgiving ‣ Closer WD may make reading area go outside central field ‣ Requires training ‣ Lighting ‣ Arm, neck, shoulder pain with fatigue over extended periods ‣ Distortion of peripheral fields ‣ Nausea ‣ Pt limitation = elbow resistance ‣ CANNOT WALK AROUND WITH THESE DEVICES ◦Contact lenses: ‣ Great for patients w/ refractive error of 10D or higher ‣ Only partially correct distance with CL ◦Prescribing for Peds! ‣ Very adaptive É Acc 181131107 1 loom if NEAR VISION AIDS: HAND MAGNIFIERS, STAND MAGNIFIERS, MICROSCOPES ◦Reading ADD: ‣ Bifocal up to +3.00D EA ‣ Microscopes up to +6.00D ‣ Stand and HH magnifiers ‣ Telemicroscope ‣ Electronic magnification ◦Advantages of HAND and STAND magnifiers over microscopes: ‣ Allows print to be help further from eye ‣ Can provide illumination ‣ Smaller FOV than glasses/microscope StillBEST ◦HAND HELD: ‣ Overview: One of simplest types and large familiarity Can correct for slight uncorrected RE Illuminated or NON Range 8.00D to 50D ‣ When to consider: Pt needs a way to spot reading material Doesnt want to bring object close to eye Wants lighted option Wants portability Cheaper than stands Distance RX is best —> but can be combined ‣ Optics: Plus lens forFoy 14.6D usable lobneeded of accommodation reading efficacy 141 73D 10 7.3 2 750 ADD required When held at focal point —> light is PARALLEL = does NOT need accommodation or and ADD System will have the most power when held right up against each other Increases FOV when held closer ‣ Training: Have pt put the magnifier on the print then slowly lift up until print is large and crisp ◦Pt can use pinky finger as “grounding” Closer to eye = larger FOV Use distance RX ‣ Measurable w/ LENSO ◦STAND MAG: ‣ Overview: Plus lens mounted in housing so that the lens is kept at a fixed distance front he page The stand height is made such that the printed material will be within the focal point of the lens Combines relative distance mag and enlargement ratio of the print Illuminated or NON ‣ Preferred over hand held when: Physical limitations = tremor, poor muscle control, child) Problems maintaining WD When pt wants extended reading distance Read continuous text ‣ ADD / ACCOMMODATION NEEDED WHEN HELD FLAT ON PAPER —> USE NEAR ADD ‣ As pt moves CLOSER to STAND = larger FOV A I EVP (aka Fe) = (ER)(1 / WD) or EVP = ER (ADD) ‣ Meausurable w/ 1) plus lens method 2) vergence amp method w/ afocal telescope and plus lenses 3) bailey’s method w/ focal telescope and adjust tube length ANCILLARY TESTING FOR LOW VISION: ◦EXAM TESTS: ‣ Binocularity: Good to educate pt that they can use both eyes Offers summation Can have larger VF Depth Perception and stereo Done on patients with VAs that differ no more than 1.5x Testing: ◦W4D: ‣ Use @ any distance ‣ Use best correction ‣ Use standard room light or decreased light ‣ Pt wears R/G gls and views colored dots 4 = gross fusion ◦Red Filter/Maddox Rod: ‣ Use @ any distance if Va is very different Dont Do ‣ VF: ‣ Red lens over NON-DOMINANT or poorer VA eye ‣ View transilluminator with both eyes and tell if light is white, red or pink Pink streak = binocularity ◦Prism Test: ‣ Use @ any distance ‣ Use in standard room light ‣ 4 prism over 1 eye and rotated while viewing distant target Diplopia = binocularity Why? ◦Determine legal blindness ◦Eligibility for driving ◦Help patient with functional loss to be quantified ◦Baseline to monitor change ◦Recommend orientation and mobility training 3 categories: ◦Central 10 degrees ◦Central 25/30 degrees ◦Peripheral 180 degrees ‣ Kinetic perimetry ‣ Static perimetry ◦Peripheral = Humphrey, handheld arc ◦Central = Amsler, target screen, NIDEK MP-1 ‣ Amsler: Measure patient’s potential for using a near magnifier for reading or writing Test metamorphopsia and small scotomas Retinal rivalry involvedinreadingefficacy also ◦When amsler findings of poorer eye competes with better eye Amsler findings when viewed binocularly Each line is 0.5mm apart subtending 1 degree when held at 13 inches Can use grid with X if pt cannot see center dot Document if lines are wavy, missing, distorted or washed out Do OD, OS then OU Facial amsler: ◦Test done at 40cm ◦Pt to look at center of face ◦Describe to you if areas of face are washed out, missing, blurry, etc ◦If pt has a hard time with contrast, this might be tough ‣ Tangent Screen: Helpful to determine larger size scotomas Good to determine the habitual EV of person with a central scotoma Target sizes can vary Testing distance usually 1m ◦Monocularly Smallest dot pt can see Move target from NON-SEEING to seeing Can also measure EV position ◦Suprathreshold letter in center of screen Kinetic + MALINGERING Automated: ◦Preferred method ◦Use different target sizes w/ reduced acuity (20/40 or worse) ◦Poor fixations may require alternate tests ‣ 2 person visual field testing ‣ Important to document how pt was tested ‣ Helpful for TBI ◦Esterman VF: ‣ Can use patients RX instead of the trial frame in VF ‣ Under specialty tests ‣ Monocular or binocular ‣ Do NOT use an eye patch Arc Perimetry: ◦Quick, economical way to test kinetic perimetry ◦Field is mapped by moving a wand along curve of arc until the patient sees the wand ◦Continue to fixation point to determine if there are any scotomas ◦Can gauge patient’s peripheral fields and test in all meridians ◦Use smallest target patient can see Goldman Bowl: ◦Kinetic perimetry ◦Can test variety of points, intensities, sizes and speeds ◦Initial testing target can be smallest target they can see 15 degrees from fixation ◦III4e used for legal blindness ◦IV4e for driving ‣ Color Vision: Helpful in confirming an ocular diagnosis Help to monitor the progression of a disease Help determine how difficult a time patient will have with ADL’s School age children who may need to color discriminate in class work Farnsworth D-15: ◦Patient arranges 14 test chips according to hue ◦Done monocularly when color vision defect is suspected that is not due to classic debutant or proton defect, X-linked blue cone monochromat or rod monochromat ◦Good for differentiating macular pathologies: ‣ DM, HTN, AMD = blue-yellow defects ‣ Dystrophies (central areolar, vitelliform, stargardt’s) = red-green ‣ ‣ ERG, EOG, VEP TELESCOPES: ◦OVERVIEW: ‣ Only low vision aid that helps with DISTANCE goals ‣ Can be used to magnify images at any distance ‣ Monocular or binocular ‣ Hand help or mounted into glass ‣ Uses angular magnification —> increases retinal image without decreasing working distance from the object ◦DEFINITIONS: ‣ Afocal: unfocusable telescope cannot changetubelength ‣ Ocular/eyepiece: lens closest to the eye Exit pupil = image of the objective lens produced by the eyepiece ◦Galilean = inside ◦Keplerian = outside ‣ Objective lens: lens closest to object Entrance pupil = objective lens diameter ‣ Focal/Focusable: can change the focus of the telescope by changing the tube length ◦GOALS: ‣ Near w/ reading, computer, sheet music If telescope is afocal, a reading cap is needed = telemicroscope ‣ Distance w/ TV, reading street signs, blackboards, identifying faces, traffic lights ◦CHALLENGES: ‣ Movement of viewed objects are exaggerated ‣ Stronger TS = smaller FOV ‣ Disruption of spatial judgements ‣ Cant walk while looking through device ‣ Light reduction ‣ Cosmetically unappealing ‣ Requires training ◦OPTIONS: ‣ Hand Held Monocular use Enhance independent travel Watch TV for short periods Spotting tasks Occasional use Trial prior to investing ‣ Clip on Monocular Slipped over rim of glasses when needed to view Used for short term when specific hands free task ◦Hand tremor ‣ Full field Any distance activity that is done sittting Needs binocular vision for extended period of time ‣ Biopic Aka 2 lens system w/ carrier lens and telescope (above line of sight) Quick spotting tasks and hands free Depth perception ‣ Binoculars ◦DETERMINING MAG OF PT’S TELESCOPE: ‣ Comparison method ‣ Ratio method Ii Mag = objective lens diameter / exit pupil Keplerian will have floating exit pupil that is measurable ◦MINIFICATION: ‣ Use in reverse design ‣ Ideal pt = someone who has < 20 degrees of field and wants help with mobility ‣ RX for VF loss patients ◦TELESCOPES AND BRIGHTNESS: ‣ Point source: Amplifies the brightness of point source Becomes brighter NOT larger All of image will fit within the exit pupil and therefore within the patient’s pupil ‣ Extended source: Does NOT appear brighter Overall brightness of the extended source depends on whether the exit pupil of the telescope is smaller/bigger than the eye pupil ◦Exit pupil is equal or larger —> NO CHANGE in brightness ◦Exit pupil is smaller —> appears dimmer ◦TELESCOPES AND FOV: ‣ Exit pupil dependent Image of the objective as seen through the telescope The closer the exit pupil is to the eye the LARGER the FOV ‣ Galilean = VIRTUAL exit pupil that is INSIDE the telescope ‣ Keplerian = REAL floating exit pupil Will have a LARGER FOV than Galilean ◦VERGENCE AMPLIFICATION: ‣ Light comes into telescope DIVERGENT Amplified by TS Significant accommodation required —> READING CAP NEEDED for afocal TS being used at INTERMEDIATE or NEAR ◦PRESCRIBING THE TELESCOPE: ‣ 1) TF refraction ‣ 2) determine required mag for goal acuity ‣ 3) test appropriate TS power device ‣ 4) determine handheld vs. spectacle mounted ‣ 5) prescribe monocularly for the better seeing eye ‣ 6) refer for training w/ device/education on weight, adjustment period Teach stability and occluder techniques 1) localization ◦View object without TS —> introduce TS ‣ If biopic, spot object then tilt head down until object is in view ◦Use opposite hand as occluder or use a patch ◦Make sure patient is sitting 2) focusing ◦Tell them the range of focus ◦Teach how to take in and out of focus ◦Look at various objects and various distances 3) spotting ◦Find the target without the TS and then locate with TS 4) tracing ◦Follow stationary line and identify letters along it ◦Encourage smooth and slow head movements 5) tracking ◦Move the head and TS while following a moving target ◦Start the pt seated 6) scanning ◦Most difficult skill ◦uses an organizes search pattern to find a target ◦Find two objects to be a reference point ◦Use a scanning grid pattern to identify the object ‣ 7) disp and RTC 2 weeks for f/u ◦PEARLS: ‣ How many degrees should my pt see? Rule of 57 —> at 57 inches away, 1in = 1 degree ‣ Evaluation a lower power first —> wider FOV Closer to eye = larger FOV ‣ Educate on oscillopsia and motion discomfort A DRIVING IN TEXAS + BIOPTIC: ◦VISUALLY IMPAIRED = better than 20/200 or abnormal field but greater that 20 degree diameter VF ◦LEGAL BLINDNESS = worse than 20/200 in the better seeing eye or less than 20 degree diameter VF ‣ All legally blind patients have low vision, but not all low vision patients are legally blind ◦GOAL: provide patient with the greatest level of independence as possible ◦DRIVING: ‣ VA of 20/40 or better in the better seeing eye = NO restrictions ‣ VA of 20/70 or better in the better seeing eye = 45mph, daytime only ‣ VA of 20/80 or WORSE in the better seeing eye = consult LV specialist ‣ WITHOUT CORRECTION - UNRESTRICTED DRIVING: MONOCULAR pt SC w/ VA of 20/25 or better SC w/ VA of 20/40 or better OD, OS, OU SC w/ VA or 20/50 or better OD, OS, OU plus doctor’s statement saying that vision cannot be improves ‣ WITH CORRECTION - UNRESTRICTED DRIVING: CC w/ VA of 20/50 or better OD, OS, OU ‣ RESTRICTED - daytime only @ 45 mph CC w/ VA of 20/60-20/70 OD, OS , OU SC w/ VA of 20/60-20/70 OD, OS, OU plus doctor’s statement ‣ REFERRAL FOR EXAM: SC w/ VA of 20/40 OD, OS, OU Monocular w/ VA of 20/25 or worse ‣ NO DRIVING: CC or SC w/ VA of 20/80 or worse in the best eye or OU with no improve with glasses or bioptic ◦BIOPTIC: ‣ Small telescope attached above the center of the glasses ‣ Range 2.2 to 4x ‣ Slight downward tilt of the head and upward shift of the eyes can bring a distance road sign or traffic light into view 90% of the time patient still views the road through the lower part of the lens ‣ Approx 50% of the states allow bioptic driving ‣ Good candidate? Driving Hx in seasoned drivers and older adults Stable or slow progressing condition Prior telescope use ‣ Placed in the RESTRICTED driving CCTV / VMS TECHNOLOGY: ◦CCTV: ‣ Closed circuit television or video magnification system Magnification device using a camera with zoom lens, X-Y table, light and a TV screen It is the “Cadillac” of LV devices Can be desk mounted, portable or variation ‣ PROS: Large mag option Can enhance contrast Uses system mag to give the patient a longer working distance Can be hands free Binocularity is maintained Goes up to 82X ‣ CONS: Portable option has short battery COST Not always portable Extensive training ‣ When to consider a CCTV? Pt with contrast impairment Needs glare reduction Pt not able to adapt to eccentric viewing Pt wants a “quicker fix” Needs high amount of mg Reading endurance and efficiency may be increased Pt is not responding to magnification as you would expect them too Prolonged reading Writing Intermediate activities ‣ TYPES OF CCTV: Stand alone Handheld ◦Lightweight w/ large screen ◦Camera that can enlarge the images ◦Have light sources built in ◦Contrast enhancement and color options ◦Consider when pt needs spotting tasks and quick tasks Portable Wearable ◦Advantages: ‣ Camera w/ display screen —> virtual reality —> TECHNOLOGY SHIFTING THIS WAY! (E-sight, No-Eyes, ORCAM) ‣ Hands free ‣ Portable unlike traditional CCTVs ‣ Can be used for distance or near ‣ Good for very active pt with may visual needs —> all in one unit ◦Disadvantages: ‣ Bulky ‣ Not best option for patients w/ poor peripheral fields ‣ Pt cannot see real life —> completely behind the device ‣ Pt need to be able to use dials and have good eye hand coordination ‣ Requires training ◦Combo of head mountable and desktop ‣ JORDY CCTV capabilities w/ docking station Full color with autofocus mag No additional light required Up to 50x mag Downloadable software available on normal computers + mag with reading tablets to enlarge print ‣ MAG OF CCTV: Uses combo of relative distance and relative size mag A MicroscopeGus ER IIe relativeDistance may STANDMAG relativeDISTANCE t ER Telescopes relative ANGULAR MY may Distance relativeAnancar relative ‣ PRESCRIBING CCTV: Bigger is NOT always better ◦Reading speed and retention will be reduced if print is too large 1) Test reading acuity w/ current add 2) Calculate EVD and EVP using ratio of TD/LS = TD/LS 3) Bring pt to CCTV w/ current add and have them sit and this working distance 4) Determine ER and set screen print size 5) Confirm system mag 6) Evaluate use ◦Place reading material at top L of x-y table and have pt bring the X-Y table all the way towards them and over to the right ◦Demonstrate typewriter method of reading 7) RECORD: ◦WD ◦Gls used ◦EA used ◦ER ◦Contrast polarity ◦System mag ‣ Different than our numbers! ‣ X value used for mag is based on a 25cm reference ◦Reading speed + accuracy ‣ DETERMINE ANGULAR FOV FOR CCTV: Tan (x) = opposite / adjacent 17 0.4318m tune 4541 0 1 0 215am 28.350 x2 56 i for Fox