Ophthalmologists

Home vision tests measure the ability to see fine detail.

Visual acuity test - home; Amsler grid test

There are three vision tests that can be done at home: Amsler grid, distance vision, and near vision testing.

AMSLER GRID TEST:

This test helps detect macular degeneration, a disease that may cause blurred vision, distortion, or blank spots. If you normally wear glasses for reading, wear them for this test. If you wear bifocals, look through the bottom reading portion. Do the test with each eye separately, first the right and then the left. Hold the test grid directly in front of you, 14 inches away from your eye, and look at the dot in the center of the grid, not at the grid pattern. While looking at the dot, you will see the rest of the grid in your peripheral vision. All the lines, both vertical and horizontal, should appear straight and unbroken, and meet at all the crossing points with no missing areas. If any lines appear distorted or broken you should note the location of these on the grid.

DISTANCE VISION:

This is the standard eye chart used by doctors adapted for use at home. The chart is attached to a wall at eye level. Stand 10 feet away from the chart. If you wear glasses or contact lenses for distance vision, wear them for the test. Each eye is checked separately, first the right and then the left. Keep both eyes open and cover one eye with the palm of the hand. Read the chart beginning with the top line and moving down the lines until it is too difficult read the letters. Record the number of the smallest line that was read correctly. Repeat with the other eye.

NEAR VISION:

This is similar to the distance vision test above, but for use at 14 inches. If you wear glasses for reading, wear them for the test. Hold the near vision test card about 14 inches from the eyes. Do not bring the card any closer. Read the chart using each eye separately as described above. Record the size of the smallest line which you were able to read accurately.

A well-lit area at least 10 feet long is needed for the distance vision test. You will need measuring tape or yardstick, eye charts, tape or tacks to hang the eye charts on the wall, pencil to record results, and -- if possible -- another person to help. The vision chart needs to be tacked to the wall at eye level. Mark the floor with a piece of tape exactly 10 feet from the wall where the chart is.

The tests cause no discomfort.

Vision may change gradually, and you adjust to the change without being aware of it. Home vision tests are useful in early detection of eye and vision problems. Perform home vision tests every year. Many people at risk for macular degeneration may be told by their ophthalmologist to perform the Amsler grid test more frequently.

• Amsler grid test: All lines appear straight and unbroken with no distorted or missing areas.
• Distance vision test: All letters on the 20/20 line read correctly.
• Near vision test: You are able to read line labeled 20/20 or J-1.

Abnormal results may mean there is a vision problem or eye disease and that you should have a professional eye examination.

Amsler grid test: If the grid appears distorted or broken, there may be a problem with the retina.

Distance vision test: If the 20/20 line is not correctly read, it may be a sign of nearsightedness (myopia), farsightedness(hyperopia), astigmatism, or other eye abnormality.

Near vision test: Not being able to read the small type may be a sign of aging vision (presbyopia).

The tests have no risks.

If there are any of the following symptoms, have a professional eye examination:

• Difficulty focusing on near objects
• Double vision
• Eye pain
• Feeling like there is a "skin" or "film" over the eye or eyes
• Frequent changing of glasses
• Light flashes, dark spots, or ghostlike images
• Objects or faces looking blurred or foggy
• Rainbow-colored rings around lights
• Straight lines look wavy
• Trouble seeing at night, trouble adjusting to darkened rooms

If children have any of the following symptoms, they should also have a professional eye examination.

• Crossed eyes
• Difficulty in school
• Excessive blinking
• Getting very close to an object (for example, television) in order to see it
• Head-tilting
• Squinting
• Watery eyes

According to the dictionary, a casuist is a resolver of questions of conscience. It involves the study of rules of right and wrong; application of such rules to particular cases; false reasoning, especially on moral matters.

You would look for occupations that involve those activities. Clergy, lawyers, judges, policemen, and others use these skills. In life, you would be a parent, a friend or a citizen of a community.

The Third Oculomotor Nerve.

Pupil constriction is also known as the pupillary reflex or miosis. It naturally occurs as the result of signals sent from the brain down the oculomotor nerve.

There are two main nervous systems in the body, the Central Nervous System and the Peripheral Nervous System. The Central Nervous System consists of the brain and the spinal cord. All other nerves, including the oculomotor nerve,which is made up of twelve paired cranial nerves, are part of the peripheral nervous system.

These twelve paired nerves are made of what are called efferent nerve fibers, the kind that move information away from the brain instead of towards it (afferent nerve fibers move signals toward the brain). All nerves in the peripheral system have a designation of either afferent (moving toward the brain with information) or efferent (taking signals from the brain to cause responses elsewhere in the body).

There are three different cranial nerves that affect eye movements: the third cranial nerve, the fourth and the sixth. It is the third oculomotor nervethat carries the signal from the brain to the muscle that contracts to constrict the pupil, hold the eyelid open, and also to signal most, but not all, of the movements of the eye.

There are two main triggers for the brain to send information down the oculomotor III nerve with a command to constrict the pupil:

* Bright light shining in the eye An eye is an organ that detects light. When bright light is shone on the eye, it will send a signal up to the brain by way of an afferent nerve. The brain will in turn send a signal down the third oculomotor nerve, an efferent nerve that carries signals from the brain, to the circular iris sphincter muscle (the ciliary muscle) to make it tighten. When the ciliary muscle tightens it closes the iris opening tight, like a purse string, automatically constricting the pupil to let less light in.

* Accommodation Reflex action

Those same ciliary muscles in each eye can be signaled to constrict the pupil when the brain is triggered by a specific reflex action. This reflex is called Accommodation. It occurs when the eye focuses on a near object, after a distant object and vise versa. The near object (for example, a computer screen) looks big in the field of vision, and the eye receives light from wide angles. When you focus on that near object, the pupil constricts in order to prevent bending light rays from hitting the edges of the retina which would result in a blurry image. As the pupil constricts, the lens becomes more round to allow for the diverging light rays.

Other triggers of pupil constriction are the direct action of miotic drugs and indirect action of opiates

* Actions of drugs

Certain drugs cause constriction of the pupils, such as heroin and other opiates (indirect drug action). Other drugs that also cause pupils to be "pinpoint" are called miotics (direct drug action).

Meibomianitis is an inflammation of the meibomian glands, a group of oil-secreting (sebaceous) glands in the eyelids. These glands have tiny openings to release oils onto the edges of the eyelids.

Any condition that increases the thickness of the oily secretions of the meibomian glands will allow excess oils to accumulate on the edges of the lids. This allows bacteria, which are normally present on the skin, to grow.

Excess and thickened oily secretions can be caused by allergy, adolescence, or general skin conditions such as rosacea. Meibomianitis is often associated with blepharitis, which can cause an accumulation of dandruff-like substance on the eyelids.

• Swelling of eyelid margins
• Slight blurring of vision due to excess oil in tears -- cleared by blinking
• Frequent styes

Meibomianitis can be diagnosed by eye examination. Special tests are not required.

Careful cleansing of the edges of the lids will usually minimize symptoms. Your health care provider may prescribe an antibiotic ointment to be applied to the lid edge.

Any general skin condition such as acne or rosacea may also require treatment.

Meibomianitis is not a vision-threatening condition. Most patients do well with treatment.

Call your health care provider if treatment does not lead to improvement or if styes develop.

Attention to lid hygiene will help prevent meibomianitis. Certain foods such as chocolate may aggravate the condition. Treatment of associated general skin conditions will help prevent meibomianitis.