Natural Vision Improvement

[4.1] What is an optometrist?

A doctor of optometry (O.D.) educated to provide routine eye health care and refraction measurement for the prescription of lenses. A growing number of optometrists, who call themselves Visual Training specialists or Behavioral Optometrists (see below), also incorporate non-surgical therapies for visual problems such as exercises, training lenses, and nutritional counseling.

[4.2] What is an behavioral optometrist?

An optometrist trained in vision therapy, which involves a wide variety of procedures for neuromuscular, neurophysiological or neurosensory visual dysfunction.

[4.3] What is an ophthalmologist?

A doctor of medicine (M.D.) trained in disease of the eye and surgery. In addition, many ophthalmologists prescribe glasses and contact lenses as well.

[4.4] What is an optician?

A technician who produces and/or dispenses the optical lenses, glasses or other equipment presribed by optometrists and ophthalmologist.

[4.5] What is the difference between sight and vision?

Sight is the process of the eyes to focus an image on the retina, vision is the ability of the brain to give this image meaning.

[4.6] What are vision problems?

Behavioral optometry regrds most vision problems as imbalance between the various systems of the bodies, most occur as adaptive responses to enviromental stresses and are present in the brain at an unconscious level. Errors of refraction are seen as symptoms which disapear when the causes are attended to.

Classical optometry regards vision problems as errors of refraction, to be treated with corrective lenses.

[4.7] What are errors of refraction?

A situation where a clear image is not formed on the retina. Myopia, astigmatism, hypermetropia all types of errors of refraction. Most of errors of refraction are very small changes in the eye, often in the order of fraction of millimeters. You only have to look at the difference in thickness in the center of a contact lens and the periphery to begin to appreciate how small the physical problems really are.

[4.8] What is accommodation?

Accommodation is the process whereby the eye adapts to bring near objects into focus and relaxes to bring distant objects into focus on the retina. Different ways of altering the eye for accommodation have been observed in different animals. For example in birds, the cornea changes shape, and in fish the entire eye elongates and flattens. In humans, accommodation is generally held to occur by the lens becoming more or less convex, under the control of the ciliary muscle. However, the precise mechanism for human accommodation is still under debate.

[4.9] What is the far point?

The furthest point at which the eye can see clearly.

[4.10] What is the near point?

The nearest point at which the eye can see clearly.

[4.11] What is excessive accommodation?

The state where the tensing of the cilliary muscle is sustained, and both the far and near point are brought closer to the eye. Diagnosis by a trained optometrist or opthamologist is easily performed under the effect of cyclopegics (drugs that paralyze the cilliary) and once diagnosed recovery is quick. Standard treatment includes temporarily minimizing near work, and rest to allow the over excited cilliary to recover from its condition of over use.

Should corrective lenses be unwittingly prescribed the condition is usually aggravated.

The causes range from improper or ill fitting spectacles, excessive amount of near work, general ill health, physical or mental. No one is really sure.

[4.12] What is spasm of accommodation?

Textbooks say a rare condition of spasm in the cilliary muscle which has become out of control. Objects are seen as larger than they normally are.

[4.13] What is insufficient accommodation?

The condition where the power of the cilliary is below that required for normal vision. Near work is blurred or becomes difficult.

A program of active and passive vision can improve this condition.

If the cause is hardening of the lens than the cilliary may have difficulty overcoming this condition.

[4.14] What is ill-sustained accommodation?

This is a milder form of insufficient accommodation, usually during period of ill health or tired eyes. Often found in people who wish to read in the evening or in bed when tired.

Treatment is the same as for insufficient accommodation.

[4.15] What is inertia of accommodation?

A condition where there is difficulty in changing the range of accommodation. Focusing seems to stick at certain points and difficulty or delay is experienced, when changing depth of focus.

A program of accommodative exercises will relieve this condition.

[4.16] What is paralysis of accommodation?

A variety of causes where the cilliary is paralyzed, either from medication or trauma. Sometimes a result of diabetes or alcohol toxicity.

Treatment of this condition resolves itself into a treatment of the cause. A medical opinion should be sought.

[4.17] What is vergence (convergence & divergence)?

Vergence is the process of muscular coordination which points each eye at the same point in space to produce binocular vision. To see at the near point, the eyes must cross or “converge”, while to see at the far point, the eyes must pull out or “diverge”.

Vergence works strongly in coordination with accommodation and pupil dilation. Vergence is principally governed by the medial recti and the pupilary contractions by the sphincter pupillae. The strong synkinetic association between these three is seen by the supply of all these muscles by one nerve called the third cranial.

It is common to find in most vision problems that the three systems are not acting in coherence.

[4.18] What is insufficiency of convergence?

Convergence insufficiency is the difficulty in focusing when the near point is less than 11cm from the intra-occular base line. The insuficiency may be in both or one eye and the causes are not well understood. Insufficiency is a common cause of reading difficulties, one eye will be looking at a point in space and the other will be looking past it.

Convergence is easily brought under conscious control, and a program of convergence exercises can correct this problem.

[4.19] What is excess of convergence?

Similar to insufficiency, but one eye is converging too far, gives the appearance of cross-eyed. Commonly found in hypermetropes, or myopes freshly behind glasses.

Treatment involves learning to obtain a double image and the use of prisms or the use of an amblyoscope.

[4.20] What is a diopter?

A diopter a measurement of the power to bend light. One diopter means the ability to converge or bring to focus parallel rays in a distance of one meter. Negative diopters diverge light.

[4.21] What is the cornea?

The cornea is the outer “lens” of the eye, in front of the pupil. It has a power +43d. Its shape is supposedly fixed.

[4.22] What is the crystaline lens?

The inner lens, behind the pupil. Is has a power of +20d at rest. Note the total power of the eyes is about +59d

The crystaline lens is thought to be solely responsible for accommodation or the change in focus from near and far objects. The added power of the lens to accommodate varies supposedly declining with age. An “average” 10 year old as around 13d of accommodative power. ie can bring to focus a point 8cm from one eye. An “average” 30 year old as around 9d of accommodative power, and so can bring to to focus a point 11cm from one eye.

Note that 1mm in change to the axial length (front to back distance) of the eye is roughly equal to 3 diopters in power. This gives you an idea of how small any problems actually are.

[4.23] What is the pupil?

The pupil is the colored part of the eye which can contract to change the field of vision and reduce the amount of light entering the eye.

[4.24] What is the retina?

The retina is the inside of the rear wall of the eye, which is photoreceptive. Light is focused here from the cornea and crystaline lens.