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An accurate trial frame refraction is the key to managing low vision patients
“At Issue” asked a panel: A 79-year-old in an assisted living environment complains of an inability to read and do puzzles. Her BCVA is OD 20/100 and OS 20/80 due to dry AMD. How do you manage her from a primary care low vision standpoint?
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Refract with trial frame, not phoropter
Lynne Noon, OD, FAAO: This patient should have a refraction to ensure the best distance correction. Because of the decreased central acuity, the refraction is best done in a trial frame so the patient will be able to use eccentric vision. The phoropter forces macular degeneration patients to look through their central scotoma and may not yield reliable results.
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For reading small newspaper type print, this patient may need a reading add of approximately +4 D to +6 D. The power of the add depends on the amount and position of the macular distortion.
The patient should be counseled on the correct use of task lighting and the working distance of the near add. Quite often the difference between success and failure when reading depends on the patient understanding the correct use of task lighting and understanding where to place reading material. The patient should have no problem working crossword puzzles when correctly using the glasses and lighting. Large print versions of many types of puzzles are available in book stores.
If making jigsaw puzzles is a goal, this patient should again be counseled on the correct use of task lighting. Because many puzzles have high gloss surfaces that can cause glare, the lighting must be positioned correctly to achieve the needed illumination while eliminating glare.
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A lamp with a movable arm containing a magnifying lens will help the patient see the small details of the puzzle pieces at all working distances. An illuminated 2X hand magnifier will also help with this task. A good choice for the patient would be puzzles that have pictures with a great deal of contrast.
All doctors should be aware of the many services that are available for the visually impaired in their state. A primary care optometrist may not have the staff needed for in-home follow-up care. However, there are often low vision rehabilitation professionals who can visit the patient in the assisted living facility to ensure that the patient is properly using the prescribed glasses, lighting and magnification devices.
For more information:
- Lynne Noon, OD, FAAO, can be reached at ViewFinder, Low Vision Resource Centers, Sun City, Yuma and Mesa, Ariz.; (866) 924-8755; e-mail: LPNoon@cox.net.
Determine etiology, provide functional vision
Katie Gilbert Spear, OD, MPH: This patient places two distinctly different responsibilities on me as the primary care/low vision specialist. My first responsibility is to accurately determine the etiology of the decreased visual acuity and ensure that we prevent further reduction. In this case, where the reduction is a result of dry AMD, my primary concern is to closely monitor this patient to detect the slightest change that indicates conversion to the wet form of the disease.
I would see this patient at a minimum of once a quarter for functional and anatomical evaluation of macular status. Much is written on using optical coherence tomography to monitor conversion. I have found that the use of preferential hyperacuity perimetry is a useful adjunct in detecting early changes that can indicate wet AMD.
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My second responsibility is in providing the most functional vision possible to allow the patient to maintain independence and allow her to do specific tasks important to her lifestyle. This requires the patient to complete a lifestyle and visual needs questionnaire to determine her visual goals, in this case reading and doing puzzles. This, along with a comprehensive examination, trial frame refraction and mapping of any scotomas will help me determine what glasses or devices would be most beneficial to the patient.
From a device standpoint, my first option would be a pair of high plus or microscopic glasses. This may be adequate to assist with reading; however, she would have a short working distance.
If this is not acceptable, I would introduce a stand magnifier (usually lighted) or a telemicroscope to lengthen her working distance. Other more sophisticated devices that could be beneficial for this patient include portable video magnifiers and CCTVs. Also remember that providing resources for large print books and puzzles is extremely helpful.
No matter what device or aids are used, follow-up with home or onsite visits and training by the optometrist or a vision rehabilitation specialist is critical to a successful outcome. Without proper training and follow-up no device will allow the patient to achieve his or her full visual potential.
For more information:
- Katie Gilbert Spear, OD, MPH, is director of Low Vision Services for Panhandle Vision Institute. She can be reached at Baptist Medical Towers, 1717 North “E” Street, Tower 3, Suite 334, Pensacola, FL 32501; (850) 438-1277; fax: (850) 438-1278; e-mail: kgilbert77@yahoo.com.
Determine necessary visual acuity
Michael R. Politzer, OD, FAAO, FCOVD: Elderly patients who remain relatively healthy and active present a unique challenge in providing appropriate solutions to their vision care needs.
The approximate add required to do the tasks this patient wishes to accomplish is determined by dividing the patient’s best-corrected visual acuity by the visual acuity needed to do the task.
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In this example, reading the newspaper will require a visual acuity of 20/30. The patient has 20/100, so 100/30 = 3.33 or +3.50 D. This amount is then added to her current add of +2.50 D, which results in a total add power of +6.00 D. A +6.00 D add will allow our patient to read and do puzzles at 6 to 7 inches; 40/6 = 6.66 inches or 16.6 cm (100/6 = 16.67 cm).
Once the add power is determined, the best way to manage the patient’s response and expectations is to demonstrate how the “new” +6.00 D add power will work. To do this, use a trial frame, set at the near PD with the patient’s combined distance prescription and +6.00 D add in the trial rings.
Place the ophthalmic stand’s light source over the patient’s left shoulder (left eye in this example is the BCVA eye), slightly behind the back well of the trial frame. Hand the patient appropriate reading material and ask her to close her eyes.
Position the reading material so it touches the patient’s nose. Ask the patient to open her eyes and push the material away from her nose until the type is clear. Discuss with the patient that this will be her new viewing distance. It will take some time to adjust, but she will be able to reach and accomplish her goals.
If the patient cannot read the material, increase the add power in +1.00-D increments. Be sure to instruct the patient that as the add power increases, the viewing distance decreases.
If the patient objects to the viewing distance, decrease the add power in -1.00-D increments. Be sure to instruct the patient that as the add power decreases, the size of the print must increase.
Key points to remember are:
- Prescribe single vision reading glasses only. Although you can special order a +6.00 D add, patients are at a higher risk for falls when using a bifocal with this type of prescription..
- Always instruct the patient to remove his or her reading glasses before standing or walking.
- Use a solid 50% yellow (450 nm) tint to improve contrast and reduce glare.
For more information:
- Michael R. Politzer, OD, FAAO, FCOVD, specializes in low vision, vision enhancement and rehabilitative optometry. He is an adjunct professor at the Illinois College of Optometry and Southern College of Optometry. He can be reached at 7003 Chadwick Drive, Bristol Building One, Suite 120, Brentwood, TN 37027; (615) 604-2949; e-mail: michael@drpolitzer.com.
Start with expanded functional history
Katherine White, OD: A low vision specialist will take an expanded functional history including questions about managing medications and finances, food preparation, communication skills, leisure activities, mobility issues and social/emotional status. The goals of reading and working puzzles may expand to include other activities of daily living.
In addition to medical examination and management, the visual status evaluation should include corrected distance and near acuities, peripheral and central visual field deficits and contrast sensitivity. Because decreased acuity with central scotomas is likely, trial frame refraction using a reduced test distance will provide an accurate refraction. Preferred lighting and filters may further enhance function and comfort.
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With a corrected acuity of 20/80 in the better eye, magnification will be required to read fine print. Depending on the print size desired, a +4 D to +5 D add will be appropriate. Options such as high add reading glasses, handheld aids, stand magnifiers on an arm, clip-on spectacle magnifiers or electronic devices will enable the patient to read fine print. If the right eye is dominant, it may need to be occluded for continuous text reading.
A magnifier is always practical for spot reading a telephone number or food package directions. The hands-free options of stronger reading glasses, clip-on spectacle magnifiers, magnifiers on an arm or a closed circuit television will be better suited for working puzzles. Cost, portability and appearance will all be important to the patient.
The patient will need training to use the prescribed aids with proper task lighting. Nonoptical devices such as a large print checkbook may further enhance independence. Psychosocial and mobility needs may be better met by other providers. Finally, education about the disease process and available resources will prepare the patient for future needs.
For more information:
- Katherine White, OD, is the managing director of Low Vision Services at ABVI-Goodwill. She can be reached at 422 S. Clinton Ave., Rochester, NY 14620; (585) 697-5733; e-mail: kwhite@abvi-goodwill.com .