Definition and Overview

In general, vision loss refers to the inability of seeing objects. The degree of vision loss can significantly vary depending on the cause. It can also be gradual or sudden.

The eyes are able to see objects based on the light that reflects from them. The rays of the light enter the eyes via the cornea, which serves as the outer covering. The cornea is responsible for refracting or bending the light rays so they are narrow enough to enter the pupil. The pupil is actually a hole, but it can expand and contract, with the help of the iris (which is the colored part of the eye), according to the amount of light that comes in.

Further refraction takes place when the light rays enter through the lens. The lens can modify its shape to accommodate the rays and bend them the best possible way until they reach the retina. Although found at the back of the eye, the retina is incredibly important since it contains rods and cones. The cones are responsible for central vision and seeing colors and other specific details of an object such as the edges. Meanwhile, the rods are necessary for peripheral vision and for seeing under low light conditions. They also help “see” movement.

The light rays then pass through the optic nerves, where they are converted into electrical signals that can be interpreted by the brain. The neurons in the brain that are related to vision then try to “piece” all the information together to create the shape of the object. The brain then sends the image signals to the nerves, allowing the eyes to “see.”

A person with vision loss may suffer from a damage of any part of the eye, especially in the retina and the optic nerves.

Causes of Condition

Vision loss can develop in a myriad of ways, but here are some of the most common ones:

  • Glaucoma – This occurs when there’s an increased fluid pressure in the eyes causing damage to the optic nerves. When the optic nerves are destroyed, a person can gradually lose vision, starting with the peripheral vision. This condition is progressive, but it does very slowly. In fact, it can take at least 5 years before the symptoms appear. The damaged optic nerves can never be restored, but the pressure of the fluid in the eyes can be reduced to avoid destroying the remaining healthy optic nerves.

  • Macular degeneration – Macular degeneration involves the loss of central vision as the macula of the retina becomes damaged. It is one of the leading causes of age-related vision loss since it’s more common among men and women who are 65 years old and older.

  • Diabetic retinopathy – This is a common complication of diabetes. The main cause is a major change in the blood vessels found in the retina. It’s either new blood vessels are formed or the existing ones become weak that they cannot hold fluid any longer.

  • Ischemia – This is a broad term characterized by insufficient supply of blood to a part or organ of the body such as the eyes. The blood is a rich source of nutrients and oxygen that help cells and tissues function effectively. When there’s not enough blood supply to the eyes, sudden vision loss may occur.

  • Cataract – Cataract affects the lenses of the eyes, causing a misty or blurry effect. Some people sometimes complain of double vision. Cataracts are common among people with diabetes.

  • Refractive errors – Refractive errors such as astigmatism, hyperopia (farsightedness), myopia (nearsightedness), and presbyopia (age-related) refer to the inaccurate refracting or bending of light that not all the details are captured by the retina. There are a number of possible causes of these errors, including the shape of the cornea or the length of the eyeball. Refractive errors can result in vision loss when they remain uncorrected or become severe.

Key Symptoms

  • Blurry vision
  • Seeing spots in the middle of the eyes
  • Inability to see from the corner of the eye
  • Seeing “black”
  • Frequent headaches
  • Tunnel vision
  • Double vision
  • Gradual limitation of movement (e.g., difficulty going up the stairs or seeing faces)
  • Increased need for additional light
  • Frequent change or upgrade of corrective glasses and lenses

Who to See and Treatments Available

An ophthalmologist is the best health care provider to approach if a person experiences vision loss. Different tests have to be conducted to diagnose the problem including visual acuity, fluorescein angiogram, dilated pupillary exam, and retinal topography.

The treatment depends on the condition.

  • For refractive errors, these may be dealt with corrective glasses and contact lenses. If the problem has become severe and if the patient is a potential candidate, it can also be resolved by refractive surgeries such as LASIK.

  • For diabetic retinopathy, one of the best steps is to monitor the progress of the disease. This condition is composed of many stages, and during the first few stages, no treatment is necessary. It only becomes important when there is already macular edema or swelling of the macula in the retina, which can result to blurry vision. However, it’s essential that diabetes itself is under control.

  • For cataracts, surgery is essential. This involves removing the affected lens of the eyes and placing an intraocular lens. The patient should be able to regain good vision after the surgery. However, if the problem is caused by diabetes, keeping the disease under control is important to avoid experiencing cataracts again.

  • For glaucoma, medications are usually the first form of treatment. Usually in the form of eye drops, these can reduce the fluid pressure on the eyes. If the medications don’t work, the other option is a surgery called laser trabeculoplasty to drain the fluid.

  • There’s no known treatment for macular degeneration, but certain measures can be taken to reduce the risk. These include a healthy diet composed of green leafy vegetables, exercise, and supplements rich in vitamin C, copper, and zinc.

    References:

  • Kraut JA. Vision rehabilitation. In: Tasman W, Jaeger EA, eds. Duane's Ophthalmology. 2013 ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2013:chap 46.

  • Olitsky SE, Hug D, Smith LP. Disorders of Vision. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 613.

  • Yanoff M, Cameron D. Diseases of the visual system. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 431.

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