Defective Color Vision

What is Defective Color Vision?

Normal perception of color is something most of us take for granted. Color labels we attach to objects such as "red lobster" and "green grass" have specific meaning only to people with normal color vision. "Colorblind" is an exaggerated term handed down over time, referring to individuals who have abnormal color vision. About eight percent of males and less than one percent of females have faulty color perception from birth. The degree to which a person may possess abnormal color vision ranges from slight difficulty in recognizing shades of color to complete loss of color vision. If one is reasonably correct in identifying colors, this slight difference may not be detectable. It is when a person incorrectly identifies a color that these differences become apparent to others.

What Causes Defective Color Vision?

While the perception of color involves complex activities of the eye and brain, the causes of congenital (from birth) defects of color vision are more simply explained. The retina at the back of the eye contains types of seeing elements called as rods and cones. The rods are responsible for night vision and operate under conditions of dim light. The cones are responsible for color vision and operate in daylight conditions. There are three types of cones: blue, green, and red, which act together to allow us to perceive a magnificent range of color, from deep indigo to blazing red. The formation of each cone pigment is controlled by heredity. An abnormal gene may subtly alter or completely eliminate a specific pigment. An individual who has inherited an abnormal gene can have difficulty distinguishing certain shades, such as reds and greens.

Are there any Other Form of Color Vision Abnormalities?

Many people have color vision deficiencies that are not hereditary. For example, aging changes may produce color vision abnormalities. By far the most common color defect accompanies the normal aging of the lens, as in cataracts. In a child, the lens inside the eye is crystal clear, but thereafter the lens gradually darkens, making it difficult for some older people to distinguish dark blues from dark greens, or dark grays. Some medications may affect color vision. Changes in color vision may also accompany retinal or optic nerve disease. Therefore, if you suspect a color vision problem, especially if it appears suddenly, you should consult your ophthalmologist.

How is Color Vision Tested?

There are several ways to test color vision. A common method requires recognition of colored numbers or symbols against a confusing background. If a color test is taken using a colored filter in front of the eye (usually in the form of a red contact lens) it is possible to "fool" the test by making the figures in the colored plates stand out more boldly and achieve a higher score. However, color-sense outside the test situation is not normal. The results of color testing are not valid when the test is performed using a colored contact lens or filter in front of one or both eyes.

Can Anything Be Done About Defective Color Vision?

Hereditary color vision abnormalities cannot be cured. It is impossible to restore to the eye those elements in the retina which nature did not provide at birth. Some acquired color

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Optic Atrophy

What Is Optic Atrophy?

The optic nerve is the nerve of vision. It carries images of what we see coded as electrical impulses, from our eye to our brain. The optic nerve is like a cable of electrical wires, and consists of about 1,200,000 separate tiny wires, or nerve fibers. Each of these carries a part of the information. If some of these nerve fibers are damaged through disease, the brain doesn't get all the vision information, and our sight becomes blurred. Optic atrophy is the medical term used to describe the loss of some or all of the nerve fibers in the optic nerve. If most of the nerve fibers are damaged, severe loss of vision is the result, while loss of only a few nerve fibers may produce little change in vision. In either case, the term optic atrophy is used.

What Causes Optic Atrophy?

Many diseases and conditions may lead to optic atrophy, or a damaged optic nerve. The nerve from only one eye may be involved, or both optic nerves may be damaged. For example, some people are born with optic atrophy because the optic nerves did not develop properly. Other people inherit the problem from parents or others in their family. Optic atrophy may also result from inflammations of the optic nerve, from failure of circulation to the optic nerve, and from glaucoma (eye pressure too high). In unusual cases, poisons, vitamin deficiencies, or tumors may be responsible. Most commonly, optic atrophy just happens, without a cause that can be proven.

What Are The Signs Of Optic Atrophy?

The optic nerve enters the back of the eye where it appears as a small disc, which your ophthalmologist can examine by looking through the pupil with a special instrument called an indirect ophthalmoscope. If optic atrophy is present, this small disc appears white (pallor), indicating loss of nerve tissue. Other signs of optic atrophy include poor vision, abnormal side or color vision, and poor constriction of the pupil in light. These may be tested by your ophthalmologist to help decide if optic atrophy is present, and if so, what caused it. Other tests including CT scans, ultrasound, or brain wave recordings with visual stimuli may be ordered.

How Is Optic Atrophy Treated?

Unfortunately, there is no effective treatment for optic atrophy. The best we can do is to find out what has caused it, if we can, to prevent further damage from occurring. Once the nerve fibers in the optic nerve are lost, they never grow back or heal. Because the nerves cannot heal, eye or optic nerve transplants are not possible. Since optic atrophy cannot be treated, the best defense is an early diagnosis. If the cause can be found and corrected, further damage may be prevented.

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Optic Neuritis

What Is Optic Neuritis?

The optic nerve is the nerve of vision. It carries images of what we see coded as electrical impulses, from our eye to our brain. The optic nerve is like a network of electrical wires bundled into a thick wire, and consists of about 1,200,000 separate tiny wires, or nerve fibers. Each of these carries a part of the information. If some or all of the nerve fibers do not do their job, our vision becomes blurred.

Optic neuritis a term used to describe an inflammation of the optic nerve, The nerve tissue becomes swollen and red, and the nerve fibers do not work properly. If many of the nerve fibers are involved, the vision may be very poor, but if the optic neuritis is mild, vision is nearly normal.

What Causes Optic Neuritis?

Many diseases and conditions may cause optic neuritis, which may affect the optic nerve of one or both eyes. Some people, especially children, develop optic neuritis following a viral illness such as mumps, measles, or a cold, In others, optic neuritis may occur as a sign of a neurologic disease affecting nerves in various parts of the body. In a rare condition called Leber's optic neuropathy, which often runs in families, a special kind of optic neuritis may appear in both eyes within a short span of time. Most of the time, however, we cannot discover a cause for optic neuritis. In those cases, we call the neuritis idiopathic, meaning that no particular cause can be found.

What Are The Symptoms And Signs Of Optic Neuritis?

Optic neuritis usually comes on suddenly, and the patient notices vision is blurred in one or both eyes. The vision is dim, like somebody turned down the lights, and colors appear to be washed out. There may be pain in the area of the eye socket, especially when moving the eyes. The vision may continue to get worse over a week or two, and may seem worse after exercising or a hot bath. A careful description of these symptoms is important to your medical doctor in the diagnosis of optic neuritis. Your ophthalmologist will also perform a complete medical eye examination. Since the optic nerve enters the back of the eye where it appears as a small disc, your ophthalmologist can examine it by looking in your eye with a special instrument called an indirect ophthalmoscope. Swelling of the optic nerve may or may not be visible depending on whether the optic neuritis is affecting the optic nerve near the eyeball. Since optic neuritis can be confused with many other causes of poor vision, an accurate medical diagnosis is important. If a cause can be found and treated, further damage may be prevented. Ultrasound, CT scans, or visual brain wave recordings might be ordered. Other tests which may be performed by your ophthalmologist include color vision, side vision, and pupil, reactions to light.

How Is Optic Neuritis Treated?

Unfortunately, there is no good treatment for optic neuritis. Cortisone- like medications (steroids) can be prescribed, the earlier the treatment better are the chances of recovery. Fortunately, most patients with optic neuritis improve without treatment. In some cases, the vision may return to normal. In other cases, good but incomplete improvement occurs. A few patients fail to recover normal vision, especially those with special conditions.

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Nystagmus

What Is Nystagmus?

Nystagmus is an unintentional jittery movement of the eyes. Nystagmus usually involves both eyes and is often exaggerated by looking in a particular direction.

What Causes Nystagmus?

Many conditions are associated with nystagmus. Sometimes, the brain's control of eye movements is poor, resulting in an inability to look steadily at an object. Some forms of nystagmus are associated with reduced vision, such as occurs in albinos, extreme near or farsighted people, or in those with scars in the retina or optic nerve. Rarely, nystagmus can occur as a result of brain tumors or in serious neurologic disorders. Nystagmus can be found in families as an isolated problem, not associated with other conditions.

What Should Be Done?

A thorough evaluation by an ophthalmologist and perhaps other medical specialists is very important. The cause can usually be determined. Important clues relate to age of onset, family history, general health of the patient, or the use of certain medications. Your ophthalmologist may examine the pattern of the nystagmus, its speed and direction and look for other eye problems such as a droopy lid, cataract, or an abnormality of the retina or optic nerves. Blood tests or special x-rays may be useful in determining the cause.

Can Nystagmus Be Cured?

Sometimes, removal of the cause may cure nystagmus. Often, however, nystagmus is permanent. The reduced vision may be improved with glasses and low vision aids. If the eyes are more stable looking in a certain direction, glasses with prisms or eye muscle surgery may improve the head position and allow better vision. Medications, biofeedback, and eye exercises have rarely helped control nystagmus.

What Are The Most Common Forms Of Nystagmus?

Motor nystagmus tends to begin between six weeks and three months of age. Other family members may have similar unusual eye movements. The motion is usually horizontal. Often focusing up close or looking in an odd direction reduces the nystagmus intensity and improves the vision. Fortunately, patients do not see the world moving as their eyes move. Vision may be reduced at distance, but is almost normal up close. There are usually no limits to the educational potential of one who has motor nystagmus.Sensory nystagmus is associated with reduced vision of any cause. Sensory nystagmus usually begins at 6 to 8 weeks of age. The eyes appear to rove, sometimes slowly and sometimes quickly. Very often the eyes will also rotate upward, and the eyelids may flicker as well. As a baby becomes older, he may poke at his eyes or wave his hand in front of them. Sometimes the cause for the reduced vision is treatable, as in babies who are born with cataracts. Other conditions which lead to "sensory nystagmus" may not be treatable. Nevertheless, understanding the underlying cause is of great importance to predicting how the baby will do in the future.

What Are Other Causes Of Nystagmus?

Medications or drugs can cause nystagmus. Rarely, this nystagmus can be associated with double vision and is often worse looking to the side. Causes include excessive drinking of alcohol or use of medications such as those given for seizure control. Often, the nystagmus will improve if the medication is stopped. Voluntary nystagmus can be created by some people, much in the same way as ear wiggling. Fine, rapid, horizontal movements can be produced and sustained for a short period of time. Often, this kind of nystagmus is used to gain attention. Disease-induced nystagmus is less common. It is often associated with neurological signs and symptoms which indicate the seriousness of the problem.

Summary

If nystagmus is present, a full eye examination by an ophthalmologist is needed. Underlying causes which determine the effect on the patient's life and vision vary greatly and we have a tailor made approach at Manna Clinic & Maternity Home & Eye Care for every person who has nystagmus to improve quality of life by providing low visual aids, glasses, and also perform nystagmus surgery in order to improve the head posture and shaking of the eyes.