Low Vision Flashcards
MaxDetail device is useful for what activity?
Computer work
* 2.2x spectacle mounted device that focuses at intermediate distance
* comes in a clip-on version to put over glasses
What are Hand Held Telescopes used for?
Spot viewing distance objects
Commonly used for viewing scoreboards at sports games.
What is the purpose of Center Fit Spectacle Mounted Telescopes?
Prolonged distance viewing
Used for activities like watching movies.
Where are Bioptic Telescopes mounted on?
Patient’s glasses
Used for spot viewing while driving and require thorough training.
What type of glasses are High Plus Readers?
Reading glasses with a high add power
Require BI prism due to high convergence demand.
How is BI Prism calculated for each eye?
Dioptric Power of the Lens + 2D
Example: Lens Power OD and OS is +8, Prism = 10BIA.
What is the main use of Hand Held Magnifiers?
Spot reading
Commonly used for reading food labels.
Do Hand Held Magnifiers require the patient to wear a near add?
No
Patients must learn to hold the device at the proper working distance.
What is a Collimating Magnifier?
A plus lens with an object at its focal point
Creates parallel light, eliminating the need for accommodation, or no add power required
How is magnification calculated for a Collimating Magnifier?
Dioptric Power of the Lens/4
Distance is assumed to be 25 cm.
What do Stand Magnifiers require from the patient?
Wear a near add
The object is placed within the focal length of the lens.
What type of reading do Stand Magnifiers provide?
Stable viewing for continuous reading
Typically used for reading books.
What is a drawback of Stand Magnifiers?
Reduced field of view
Objects are placed within the focal length of the lens.
What type of magnification do Stand Magnifiers use? And does it need an add?
Conventional Magnification, yes an add is required
Necessary due to the positioning of the object within the focal length.
Which low vision device is attached to pt glasses to allow for intermediate viewing? And does it require an add?
Tele-microscopes/spectacle mounted magnifiers, yes it needs an add
- poor cosmesis and heavy
- non-collimating magnifier, accommodation and/or add power required
Patients without accommodation will require _____ to use CCTV
An add
CCTV
Electronic magnifier
* camera, monitor and moveable table
* maintains contrast sensitivity and provides magnification without peripheral distortion
* utilizes relative size magnification
What type of low vision device is this?
Spectacle-mounted magnifiers = collimating lenses
Hand held magnifier
* object at focal point of magnifier, image at infinity
* collimating magnifier= no accommodation or add power required
What is this low vision device?
Stand magnifier
*iso-accommodative situation
Non-collimating magnifier, accommodation and/or add power required
Hand held telescopes are used for?
Spot viewing distance objects (scoreboard at a sports game)
Distance viewing device
Center fit spectacle mounted telescopes used for?
Prolonged distance viewing
* like watching a movie
* Attached to patient’s glasses
Bioptic telescopes are used for?
Mounted to pt’s glasses and are used for spot viewing while driving
* pt MUST be trained to use device
High plus readers used for?
Near viewing device
* reading glasses with high add power
* require BI prism due to high convergence demand
*BI prism for each eye = dioptric power of lens + 2 D
Example: OD and OS is +8
Prism 8+2= 10 BI PD, therefore each eye requires 10 BI PD
True or false, hand held magnifiers require near add
FALSE
* do NOT require near add
* patient needs to hold device at proper working distance
* used for spot reading food labels
* not ideal for patients with hand tremors
True or false stand magnifier is used for stable viewing, continuous reading of books
TRUE
* also have reduced field of view
Telemicroscopes/ spectacle mounted magnifiers used for?
Intermediate viewing
* poor cosmetics and are heavy
CCTV uses ______________ magnification
Relative size
What is this chart used for?
Vistech contrast sensitivity chart
*utilizes sign waves gratings
What chart is this?
Pelli-Robson contrast sensitivity chart
* for distance testing 1 meter and utilizes Sloan letters of the same size with contrast sensitivity reducing after each triplet
What is this chart? And is it for near or far?
Mars contrast sensitivity chart is for near testing at 40cm and utilizes Sloan letters if the same size
What is this chart?
Central California visual field test
* perform monocular or binocular
* pt fixates on chart while examiner shines laser through chart
* test more informative than Amsler
What is this chart?
Tangent screen
* used to measure magnified view of patient’s central visual field
* pt fixates on center target while examiner moved a target from periphery towards center, pt reports when they can first see target
*VF should be larger when measured at 2 vs 1 meter
*if same size or smaller= malingering
Keplerian telescope features
- Positive ocular lens
- Positive objective lens
- Power greater than 4X
- Inverted image
- Exit pupil outside telescope
- Longer and heavier
Galilean telescope features
- Negative ocular lens
- Positive objective lens
- Power only up to 4x
- Upright image
- Exit pupil inside telescope
- Short and light
BCVA 20/50
6 diopters
Steps to solve:
1. take denominator of BCVA and divide by goal acuity (50/20 = 2.5)
2. Take reciprocal of working distance (1/0.40 = 2.5)
3. Multiply (2.5 x 2.5 = 6.25 D)
