Tools for patients with minimal, moderate, and maximum vision loss.
The visual outcomes and prognosis of patients with central vision loss related to vascular problems has changed significantly over the past several years. With the advent of new anti-vascular endothelial growth factor (VEGF) drugs and the ability to resolve greater detail of retinal structures, patients are enjoying much better outcomes.
Topaz PHD allows
for reading comfort with a
reasonable field of view.
|High-powered electronic magnifiers
like the MagniLink Zip 17 from
Eschenbach can provide assistance for
those with maximum vision loss.
|Hilco’s Coil LED Illuminated
Rechargeable Pocket Magnifier
is a good choice for patients
with minimal vision loss.
ADVANCES IN TREATMENT
Medical treatment protocols for the wet form of age-related macular degeneration (AMD) have shifted from attempts to cauterize leaking blood vessels with laser photocoagulation to a family of drugs that are injected into the vitreous cavity. These drugs prevent the growth of new abnormal blood vessels and return the permeability of leaking vessels to a more normal state.
The doctor can begin treatment to reverse the damage to the retina and improve function at the first sign of blood or serum outside of the capillary network, as measured by optical coherence tomography (OCT). This strategy, however, requires repetitive treatments to suppress the endothelial growth factor. Although patients maintain reasonable acuities, there is some loss of function from repeated exposure to small amounts of fluid and the drying out of the retina areas around the macula.
Aggressive treatment with anti-VEGF agents has eliminated the dense absolute central scotoma that was associated with the dramatic loss of visual acuity in AMD. In the past, patients would come to a low vision specialist with dramatic acuity loss, but would respond almost immediately to magnification.
Patients undergoing anti-VEGF treatment may have reasonable visual acuity but still struggle with certain daily tasks. This often prompts the retinal specialist to refer the patient for low vision care at later stages of the disease.
These patients may continue to receive treatments, sometimes for years, to stabilize the retina anatomy. Although acuity can remain at acceptable levels, there is a loss in function of the paracentral region. Reasonable acuity levels can mislead the retina specialist and delay referral for low vision management.
When testing the visual function of these patients, acuity is not always the best measure. These patients will have a mix of responses, some often skip only the fourth letter on each line of five letters, or scramble letters of only larger words. Reading single letters at near may indicate a high level of function, but when asked to read continuous text print, the patient will often fail. Paradoxically, larger print or magnification can further decrease the reading function leading to poor patient outcomes. These are the patients that have good acuity but who sadly put down their books with frustration. Low vision management must include strategies other than magnification to help these people. ECPs must look specifically for these small errors on the distance acuity test and pursue testing with continuous text print to pinpoint these problems.
CAUSES OF LOW VISION
The first step in management is a careful trial frame refraction. Even small amounts of uncorrected refractive error can compound the functional problem. The next step is to add high levels of direct light. The light source should be directed on the print and placed between the patient and the reading material. Handheld LED flashlights or a low power illumined magnifier can have a dramatic effect on reading function. There may be the need for some magnification but the provider needs to carefully observe the reading function as magnification often pushes part of the image into the ring scotoma.
Wet AMD is not the only problem that is encountered in low vision. Dry AMD, diabetic retinopathy, and other retina problems continue to cause loss of visual function, with or without treatment. Optic nerve disease can cause central vision loss and other issues.
LOW VISION AIDS
Generally speaking, patients with good acuity in the 20/25 to 20/40 range may be mildly symptomatic. Traditional magnification devices, such Hilco’s illuminated handheld magnifiers, provide an excellent and rewarding option. It is important to titrate magnification addressing the current needs of the patient and leaving room to adjust magnification in the future.
Moderate vision loss arises when patients note a decrease in their ability to perform daily tasks. Often in central vision loss, patients find that reading text becomes increasingly difficult while identifying single letters even though sorting through bills and mail may still be achievable. These patients will often benefit from learning effective eye movement strategies to avoid the blind spots and stay focused on the areas of good vision. The field of useful vision can be expanded with the use of high magnification in the better eye with a device known as a monocular microscope. Due to close working distances, some cases call for portable devices, such as Freedom Scientific’s Topaz’ PHD, which can allow for reading comfort with a reasonable field of view.
Spectacles with the better eye focused at a close distance with powers such as +12.00D, +16.00D, +20.00D, and higher will create a large image that spreads over the macula and paracentral zone. During viewing, the fellow eye is occluded. Utilizing single letters followed by a series of two-, three-, and four-letter words in repetition can be used to allow the brain to easily pick the best area of focus and ignore the blind spots. This is reinforced by repetition until reading speed, accuracy, and comprehension improves. Then other low vision aids such as handheld magnifiers and telescopic lenses can be prescribed for specific tasks.
Severe vision loss is returning to the forefront of low vision management as patients are living longer. In particular, is the slow expansion of giant areas of geographic atrophy. This disorder has been long associated with the dreaded “ring scotoma” that has an inverse response to magnification. As time passes, the central island of vision that was holding on by a few remaining macular photoreceptors becomes too small to achieve useful function. For these patients, all of the traditional tools of low vision””glasses, microscopes, handheld magnifiers, and telescopes””lose their effectiveness. These patients feel a devastating loss of independence. Optometrists will need to provide counseling and a positive outlook to manage these patients and their family members.
High-powered electronic magnifiers (like Eschenbach Optik of America, Inc.’s MagniLink Zip 17) can provide some assistance for limited tasks, such as reading menus and looking over bills. While they are impractical for extended reading and other desired visual goals, they can provide a little more independence to some.
Targeting treatments for today’s low vision patients requires an evolving skill set to improve outcomes. ECPs must adapt testing and treatment programs to account for the needs of their low vision patient utilizing the latest optical and electronic aids.
Ryan P. Edmonds is in private practice in Philadelphia, PA.
WHERE TO FIND IT:
Hilco •800-955-6544 •hilco.com
Eschenbach Optik of America, Inc. •800-487-5389 •eschenbach.com
Freedom Scientific •800-444-4443 •freedomscientific.com