Low Vision Conditions
Also referred as ARMD or AMD, macular degeneration is the leading cause of central vision loss in the US. Typically associated with aging, it can be exacerbated by smoking, Diabetes, increased sun exposure and preservatives. Early in the disease, one can experience wavy appearance of straight lines, subtle distortions and difficulty reading. As the disease advances, loss of detail vision can occur making it difficult to drive, watch television, recognize faces, cook, see the food on one’s plate, read or write. However, peripheral vision is always retained, so the individual does not become completely blind due to macular degeneration. Even in the advanced stages, the brain selects an area just outside the center to be used as the new fovea (also known as the “sweet spot”). Training in the use of this area can help you maximize the use of your residual vision. Magnification of varying levels may be required for different tasks along with training and strategies to make you as independent as possible. Your doctor may also talk to you about driving options, increasing lighting, and controlling glare with special blue blocking filters and nutrition/ vitamins.
Stroke and vision loss
Stroke is an interruption of blood supply to the brain either due to a hemorrhage or a block. If blood supply to the visual pathway or the centers that process vision get interrupted, bilateral visual field loss can occur. Typically referred to as just hemianopia or homonymous hemianopia, it usually affects one half of the visual field in each eye, due to the way the nerve fibers travel in the brain. A right hemisphere stroke will cause a vision loss on the left side of both eyes and vice versa. Depending on the area of the brain affected, varying degrees of hemianopia can occur. Difficulty reading across the page or coming back to the next line, skipping words, missing half the food on the plate, walking into doors, difficulty with mobility in crowded places, driving and loss of independence can occur. While traditional magnification is usually not helpful in these cases, peripheral field enhancing systems may be helpful. Training in scanning and compensatory strategies can help with safe mobility and improving independence. Training in reading writing strategies may be recommended along with training in activities of daily living. Driving requirements may be discussed and road readiness may be assessed.
Low Vision and Diabetic Eye Disease
Visually impaired diabetics have specific needs to be addresses in the low vision examination. Diabetics must see to fill insulin syringes or take oral medications. Diabetics need to see to test their blood sugar. Diabetics need to read labels on food containers to control their intake of carbohydrates. Diabetics may have neuropathies affecting their feet. If the patient is unable to see his or her feet, other care by their physician, podiatrist or family may be needed to monitor the health of their feet. Glare and loss of contrast sensitivity need to be addressed.
Diabetics often experience fluctuations in their vision related to changes in nearsightedness or farsightedness caused by ups and downs in their blood sugar. As the blood sugar fluctuates, the shape of the human crystalline lens changes. Before prescribing eyeglasses for a diabetic patient, doctors frequently retest the patient on another day to test for these fluctuations.
Loss of Central Detail Vision
Macular edema is a swelling of the delicate macular tissue in the center of the retina. It does not cause total vision loss but causes a loss of visual acuity. Macular edema can be treated if identified in the early stages. Your optometrist or ophthalmologist can detect this swelling through a dilated retinal examination using a microscope and special lenses. Magnification and increased lighting and contrast can usually help with this condition.
Profound Loss of Vision
Proliferative Diabetic retinopathy is the more dangerous condition. It has the potential to cause profound vision loss by damaging the small blood vessels of the retina. Chemicals are released from the retina that can cause abnormal blood vessels to grow. These blood vessels break and bleed creating scar tissue within the eye. As the scar tissue contracts, it may pull on the retina leading to a retinal detachment. Regular visits with your eye doctor are extremely important to ensure timely treatment which can prevent further vision loss. High powered magnifiers and electronic reading machines (CCTVs) may be required to help you read if you are in this stage of the disease. Laser treatment to the periphery can cause difficulty with mobility, particularly in low light and nighttime. You may be prescribed Occupational therapy training and mobility training by your doctor along with a home assessment to ensure your safety and reduce risk for falls.
Color Vision Impairment
Color vision may be mildly affected along the yellow-blue axis. This allows them to accept the yellow and amber lenses often required to improve contrast after laser, without being bothered by the degree of the yellow color.
Reduced Side Vision After Laser
Laser treatment is crucial in saving the sight of many diabetics. Laser, however, causes other visual problems that should be addressed by the low vision specialist. Pan-retinal laser treatments require hundreds of laser burns across the peripheral retina. By lasering these peripheral areas, more oxygen is available to the supply the crucial center of the retina, where our sharpest vision exists. Unfortunately, some side vision may be sacrificed to save the central vision. This can cause difficulty with driving, walking, depth perception, stepping off curbs and stairs etc. Some of these issues can be addressed with appropriate lighting and contrast enhancement. Your doctor may also talk to you about driving cessation, based on the level of peripheral vision loss.
Loss of Contrast Sensitivity and Glare Problems
Patients often describe a “hazy-glare” after laser surgery. Contrast sensitivity, the ability to judge subtle differences in images like seeing a gray object on a dark gray background decreases. Our world is one of subtle contrasts. We use contrast sensitivity to see faces or find a dark object on a darker background. Amber filters like the Corning CPF series reduce the glare and may aid contrast.
Night Blindness After Laser
The peripheral retina contains more of rod cells that we use to see at night. In lasering the peripheral retina we lose more rod cells that we need to see with at night. Night driving may become more difficult due to loss of rod cells. At night, clear eyeglass lenses may be required. If extensive laser has been performed, night driving may become dangerous.
Your optic nerve is susceptible to increase in the pressure within your eye causing you to lose your peripheral vision without even being aware of it. If left untreated, it may lead to profound vision loss and eventually total blindness. Depending on the severity of the condition, individuals with glaucoma may experience loss of peripheral vision, inability to drive at night or day, increased glare, loss of depth perception and overall sensation of being in a fog. Minimal magnification along with training, increased lighting and contrast, glare control filters etc may be recommended by your low vision doctor.
While most cataracts develop later in life, diabetics develop cataracts at an earlier age in adults and cataract may even occur in children. Cataracts may cause a foggy clouding of vision and can make driving unsafe due to exaggerated glare.
Diplopia or double vision due to oculomotor paralysis can be precipitated by a variety of reasons including diabetes, trauma, tumor or stroke. At the first sign of double vision, see your eye practitioner immediately. Double vision that does not require surgical correction is usually treated with prisms or partial patching and muscle retraining.
Also referred to as RP, it causes gradual bilateral loss of peripheral vision, ultimately leading to tunnel vision. Early signs may appear as difficulty with night vision, progressing to difficulties with driving, walking, bumping, stepping off curbs and stairs, increased glare, pouring, finding things when dropped etc. Risk for falls is higher due to visual field deficits. Central detail vision is retained in most cases. Occupational therapy training and Orientation mobility training along with use of flash lights may be recommended by your low vision doctor. Community resources, public/ alternative transportation may be explored. Minification or field expanding devices may be beneficial.