Visual Acuity Test

Visual acuity (VA) indicates the clarity of vision dependent on the sharpness of retinal focus along with interpretation by the brain. Visual Acuity Test involves a test where a person has to read letters on a standardized Snellen chart held about 20 feet away. This test is done individually for both eyes. Visual acuity test is part of the routine eye tests to check for vision. Visual acuity is expressed as a fraction where the numerator is the distance of the chart, usually 20 feet. The denominator is the distance where a person with normal eyesight can read the same line correctly. 20/20 is normal vision. Abnormal results on the visual acuity test indicate the need for corrective glasses.

Optic atrophy

Optic atrophy is the result of the fibres of optic nerve failing to transmit the visual information to the brain due to the damaged optic nerve which may result in problems with vision. Optic atrophy refers to the loss or damage of the fibres of the optic nerve. Optic nerve is responsible for carrying images from the eye to the brain. Optic atrophy presents itself with pale appearance of the optic nerve head at the back of the eye; hence this condition is also referred to as optic nerve head pallor. Although optic atrophy affects one eye, bilateral optic atrophy can also occur when the illness damages the nerves of the both eyes.

What causes optic atrophy ?

Optic atrophy is a serious eye disorder that is caused by a underlying disease or condition. Few of the diseases originating in the eye and the nervous system that lead to optic Atrophy are given below.

• Compression of the optic nerve.
  
• Glaucoma or high pressure within the eye.
  
• Infection
  
• Multiple sclerosis
  
• Inflammation of the optic nerve called optic neuritis.
  
• Interruption in blood circulation to the optic nerve in the form of decreased blood supply (ischemia) or oxygen supply (hypoxia).
  
• Tumors on the visual pathway
  
• Trauma
  
• Optic atrophy can even be inherited from parents.
  
• Nutritional deficiencies (especially B12), certain medications and exposure to certain toxins also lead to optic atrophy.
  

Symptoms of optic atrophy

If you face any of these symptoms seek medical attention immediately as any progression of optic atrophy leads to vision loss. Though the occurrence of these symptoms does not necessarily mean optic atrophy, it is always better to rule out this severe eye condition. Ophthalmologist will examine the eyes with an ophthalmoscope and the doctor may recommend few more tests, if he suspects optic atrophy. Tests such as tonometry, pupil light reflex, color vision and visual acuity are conducted.

• Blurred vision
  
• Poor visual function such as low clarity of vision or visual acuity.
  
• Distorted peripheral vision.
  
• Problems in color vision
  
• Decreased brightness in the affected eye. Diminished reaction of the pupil to the light.
  
• Change in the optic disc

Treatment of optic atrophy

Currently there is no sure shot and effective treatment or therapy available for optic atrophy. However ophthalmologist diagnose the underlying condition or disorder that is causing optic atrophy and treat them. This will avoid the further damage of the optic nerve and preserve the existing vision.

Presbyopia

Presbyopia is a vision problem where there is difficulty in seeing close objects. With age, the capacity of the lens to change its length or shape to focus on nearer objects becomes difficult. This loss of elasticity usually happens with persons in their 40s. You can identify presbyopia when a person finds it difficult to focus on near objects and suffers headache and eye strain. Visual acuity, refraction test and retinal examination aid in diagnosing the extent of correction needed. Reading glasses can be worn to rectify this vision problem. Those who also suffer nearsightedness can go in for bifocal lens to also correct both vision problems.