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The various procedures and tests, and the order in which
they are conducted, vary from practitioner to practitioner. Optometrists may perform tests that
ophthalmologists may not, and the reverse is also true. Within both disciplines, the doctor may
specialize in certain specific areas of vision care and provide additional testing. The scope of
practice of the two eye doctors varies somewhat from state to state and may be different in other
countries as well. Some of the tests, such as the automated/computerized procedures indicated below,
may be delegated to an assistant.
The information below is a compilation of most of the routine tests and findings that comprise a comprehensive eye examination. You should also keep in mind that not all eye examinations need be comprehensive, and your doctor may be responding to your request for the evaluation, diagnosis and treatment of specific complaints. Generally, a comprehensive examination may take from one half hour to over an hour, depending upon the number and type of tests required.
Why are you here? Is this visit for a routine eye evaluation or is there a specific problem? These might well be the opening remarks from your doctor. Be specific about your concerns. You will be asked "When does it happen", "How often does it occur", "Is this a new problem", "Does it happen when you use vision correction " (if applicable), and other appropriate questions to probe the extent and symptomology of your complaint.
The History: Ocular
A query as to previous injuries, infections, surgery,
vision correction, etc.
The History: General
A query regarding your general medical history,
current health and medications. Certain systemic (whole body) diseases and medications may effect
the eye and vision system. You may also be asked about cigarette smoking, caffeine and alcohol
consumption. These drugs all have effects on the functioning of the human vision system.
The History: Family
Certain eye conditions may be hereditary. Health
issues such as hypertension ("high blood pressure"), diabetes, thyroid dysfunction,
coronary artery disease, hyperlipidemia (elevated cholesterol) and others can be inherited and may
show early signs in the eye.
Visual Acuity
The External Examination
The Internal Examination
The
Refractive Visual Analysis
Visual-motor and Binocular Vision
Assessment
Visual Acuity
Near VA is generally tested at 16" (40cm) and is measured as above (adjusted for the relative distance but still expressed as 20-foot, or 6-meter fractions or in Jaeger notation). Some doctors use typesetters point size.
External
This includes the examination of the external parts of the eye and surrounding associated tissues. Structures examined include the eyelids and lashes and general observation of the conjunctiva and iris. There may also be microscopic evaluation of those structures as well as the cornea, crystalline lens and anterior chamber structures, using a slit-lamp/biomicroscope. Gonioscopy, a detailed examination of the drainage system in the anterior chamber, may be included for people who may have glaucoma. This specialized test is generally not part of a routine examination.
Peripheral Visual Fields
These may be tested by confrontation (use of a hand-held, usually white target to test the limits of peripheral vision) or by automated instrumentation. The auto-perimeter test is often not part of a routine examination, but is often included for people at risk for glaucoma or for routine "baseline" screening. The automated test may be performed by a technician.
Why might this be necessary? Defects in the peripheral visual field may be an indication of internal eye conditions, including retina detachment and glaucoma. Additionally, field loss may be a result of lesions or tumors in the brain or vascular disease such as stroke.
The Pupil Reflex Tests
In this neurological integrity test, a light is
shone onto the eye and the iris is observed for constriction (reduction in size) and dilation
(increase in size). An object is presented at a point in front and close to the eyes to stimulate
focusing as the iris pupil is evaluated for constriction reflex.
Why: Abnormal pupil reflexes
may indicate faulty neurological development. It can also be a sign of internal eye infection, eye or
head trauma or neurological disease in the eye or the pathways to the brain, including some serious
diseases.
Ocular Motor Tests
Rotations and Versions: Eye muscle facility and tracking are evaluated by having you observe an object moving in the field of vision, usually horizontally, vertically and at various angles. The eyes are tested individually and when working together.
Divergence/Convergence Cover Test: The eyes are observed for alignment. Alternately, one eye then the other is covered and uncovered. This tests the resting position of the eyes and their response to focusing and targeting the observed object. Alignment is usually tested at distance and near. Mis-alignment may indicate strabismus (cross- or wall-eyed), uncorrected optical error, or neurological disease.
Fixation and Saccades: More often performed on children, these tests evaluate the ability of the eyes to maintain attention on one point in space and then to move from point to point accurately without over- or under- shooting the fixation point, thereby requiring an adjustment movement.
Why are ocular motor tests important? In children, faulty development of this facility often leads to delayed reading skills and other learning disabilities, as well as mal-coordination with other motor skills, such as walking or athletic abilities. In adults, if one is previously tested as normal and then suddenly not normal, this may indicate neurological disease, including multiple sclerosis, brain tumor, or result from stroke or other systemic diseases.
Binocular Vision Tests
Why: Poor or lacking binocular vision in children may indicate faulty vision system development
and lead to learning disabilities and "clumsiness".
Adults: See comments under
ocular motor facility tests, above.
Color Vision Tests
Ophthalmoscopy (in some places called Fundoscopy)
The observation of the internal structures of the eye employs an instrument called an ophthalmoscope. A direct ophthalmoscope contains a light source to illuminate the inside of the eye and lenses to focus the image for the observer. It provides a somewhat limited but magnified view of the inside of the eye. It is a hand-held instrument brought very close to the eye. An indirect ophthalmoscope is used to provide a significantly wider field of view in stereo (3-D) and usually requires drops to dilate the pupil. The indirect ophthalmoscope also contains a light source and is worn by the operator as a spectacle-mounted or head-band mounted apparatus. A large lens, held in the doctor's hand, is placed before the eye and the doctor, (wearing the apparatus) is positioned a couple of feet in front of the patient. The indirect instrument is considered to be the standard of care and is especially valuable for examining the retina and optic nerve and the peripheral structures in the back of the eye. Both instruments allow observation of not only those structures, but also the arteries and veins feeding them. (Often both ophthalmoscopes are used during examination). It is the only technique that, without surgery, allows direct observation of a living network of blood vessels and can help diagnose atherosclerosis (hardening of the arteries), hypertension (high blood pressure), diabetes mellitis, as well as other systemic (whole body) and eye-specific disorders.
Direct ophthalmoscopy may be done prior to the visual analysis (see below), but dilated pupil indirect ophthalmoscopy is often performed following vision testing, as the dilating drops may effect optical measurements.
Tonometry
This is the measurement of the fluid pressure of the eyeball. Elevated pressure is one of the signs of glaucoma. There are a number of instruments used to test eye pressure. Some require that an object be placed for a moment against the cornea in the front of the eye (often requiring a drop of anesthetic and sometimes a liquid to color the tears) and some use a burst of air to press against the eyeball. Tonometry is often performed at the end of an examination. The automated "air puff" instrument may be operated by a technician.
Keratometry
Retinaoscopy and Auto-refractometry
This test is especially valuable for non-communicative children or adults and some practitioners use the information gathered as a prescription power for eyeglass lenses. However, the human vision system is not so inflexible as the objective findings may indicate and subjective, patient-directed modifications are often indicated.
The Subjective Refraction
The doctor presents a series of lenses and asks for the viewer's opinions as to the effective qualitative changes that result. Sometimes patients feel they must "give the right answer". In reality, there are no correct answers and any information you give becomes important in the analysis of your vision system.
Phorometric (Phoria) Measurements
The lenses that provide you with clear vision are analyzed for their effects on your eye muscle balance and coordination. You are asked to align a presented object or letter horizontally and then vertically. Sometimes, the lens that provides the best vision is also the power that causes your eyes to strain to turn inwards or outwards and would not provide comfortable vision.
Accommodative Range and Near Vision Analysis
Infants and toddlers: by 6 months of age (neurological, motor, gross vision evaluation. knowledgeable pediatrician may be able to provide this service)
Pre-schoolers: at ages 3 and 5 (comprehensive vision exam)
School age to 19 years: annually (annual screening for distance and near vision. If normal, comprehensive exam at age 7 or 8, pre-puberty, ages 14, 16 or 17)
Adults: every 1 or 2 years (every 2 or 3 years if no lens correction. Glaucoma test and eye health screening every year after age 35 or if significant family history of eye problems.)
Author's notes:
For non-routine, symptom-prompted examinations: Emergency
Any
recent onset of blurred vision, double vision, distorted vision, loss of peripheral vision, increase
in number or size of floaters, flashing lights in peripheral vision, increase in light sensitivity,
pain upon movement of the eyes, any discharge or bleeding, halos around lights, pain upon closure
or opening of eyelids: requires immediate attention.
Non-Emergency:
Gradual loss of ability to focus on near objects, blurred distance vision after concentrated near vision activities or the reverse, change in quality of vision with existing eyeglasses or contact lenses, headaches or eyestrain, especially after near vision tasks: non-emergency examination.