The Comprehensive Eye Examination

WHEN YOU DECIDE TO PROCEED with accelerated ortho-k to improve your vision, there will be several steps prior to beginning the actual procedure. The first will be a comprehensive vision examination and eye health evaluation.

The orthokeratologist will include computerized corneal topography as part of this evaluation. This is necessary to accurately analyze the curvature and elevations of your cornea. It becomes the baseline for all corneal re-shaping. After your comprehensive examination, the accelerated ortho-k procedure will be discussed with you along with lenses, conditions, finances and the orthokeratology case fee agreement. Your first lenses are then designed for you to begin wearing as you start the ortho-k program.

The basic eye examination requires about 30-60 minutes. This may vary depending on the number of tests deemed necessary. Generally, most doctors or their assistants will begin by taking your detailed case history. You will be asked about any current problems with your vision. You will be asked the duration and severity of any problems. There will be questions concerning the date of your last eye exam, any pre-existing eye problems, your occupation, hobbies, and general health status questions will be asked about your family’s eye health and medical history, any allergies to medications, and current medications you are currently taking. The purpose of this case history is to provide the doctor with an idea of what may be affecting your vision. It also highlights any potential problems that might arise because of your family’s eye health history, your work habits, and your occupational vision demands.

Visual Acuity Tests
The first test is usually a visual acuity test. This is performed using the Snellen Chart or other eye charts with letters, numbers, or symbols. You will be asked to read progressively smaller rows of letters or numbers until they become indistinguishable. Even if you have to guess, try to make out the smallest letters possible without squinting.

If the doctor reports that you have 20/20 vision, this indicates that you see at 20 feet what you should be seeing at 20 feet, that is you have normal visual acuity. If your test reveals 20/40 Visual acuity, this indicates that you can read at 20 feet what a person with normal vision reads at 40 feet unaided. Visual acuity is measured with the naked eye (without glasses or contact lenses). You will also be asked to read the eye chart with your glasses or contact lenses on. This is referred to as aided visual acuity. In addition to the distance vision, near-vision tests may also be conducted with or without lenses.

The Refraction
Next, an objective refraction may be performed with a computer (auto refraction) or a hand-held instrument called a retinoscope. It will provide an estimate of your refractive error (visual error). Refractive error is a measure of the magnitude of your nearsightedness, farsightedness, and astigmatism in diopters of correction.

Then comes subjective refraction. This test refines your prescription based on your subjective responses to a variety of lenses. The doctor performs these tests with a phoropter. These tests result in a determination of your spectacle correction and the basis for a correct contact lens prescription.

An example of a spectacle prescription is -2.00 -1.00 X 180. This means that you are 2.00 diopters myopic with 1.00 diopter of astigmatism oriented at an axis of 180 degrees.

Corneal curvature measurements are a key part of the comprehensive exam:

1. A computerized measurement of corneal curvature is performed first. This is called autokeratometry. OR . . .
2. The doctor measures the corneal curvature manually with a keratometer.
3. Computerized corneal topography is then used to map the corneal topography, elevations, contour and shape of the cornea. This is the most advanced, sophisticated method of analyzing the cornea.
   

Your functional vision skills will also be tested

You will be tested for focusing skills with lenses to stimulate and inhibit the focusing mechanism of your eye. Eye movement skills are tested to measure the smoothness of your eye movements, and accuracy of your fixations.

Convergence skills are then tested with special prisms to measure the convergence and divergence (aiming ability).

Your eye health is of primary importance in your initial eye exam. The doctor will use ophthalmoscopy and possibly photography to analyze the internal eye health. The external structures of the eye and lids are analyzed with a biomicroscope (slit lamp).

Visual fields testing may be performed to determine that your eyes and brain are capable of "seeing" in the periphery as well as in the more detailed central vision.

A color vision testing is performed for color deficiencies, and pseuedo-isochomatic plates are used to diagnose any color differences.

In summary, comprehensive eye exams are critical to all prescription lenses and treatment programs and eye health determinations. These tests are used to prescribe the far and near prescriptions lenses (glasses and/or contact lenses). The eye health exam determines whether medical treatment is necessary prior to beginning accelerated corneal molding or any other treatment plan. The functional vision skills control your aiming and focusing ability. At this point the accelerated ortho-k prognosis (the results) and program length can be estimated.