What To Expect From an Eye Examination

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GREETINGS --

The following is a somewhat lengthy discussion of the components of s

detailed eye examination. Such an exam would be necessary to

establish a set of baseline conditions for a diabetic's eyes. The

author is both an optomotrist and a Type I diabetic who specilizes in

Diabetic patients. The article is from the Diabetes In Control

website and although the author is not an opthalmologist he is

extremely knowledgeable regarding the subject matter. Generally,

however, an opthalmologist or retinopathist would be best suited for

the exam.

wambo

What To Expect From an Eye Examination

Chous, M.A., O.D. Doctor of Optometry

Type 1 diabetic since 1968

Now that we have considered the various kinds of diabetic eye

disease, the treatments available for each, the results of clinical

research, and some recommendations for avoiding or minimizing eye

complications, let's discuss the elements of a thorough diabetic eye

examination.

It is unlikely that any two eye doctors (or any kind of doctors) will

conduct an examination in exactly the same way; Procedures,

techniques and explanations that work well for one health care

provider may not work for another, and vice versa. Here, it is simply

my aim to describe and explain the fundamentals of an eye exam that

will allow you to ask the right questions and assess the thoroughness

of your examination experience.

All eye examinations should start with a detailed `case history.'

Patients often ask why so much general health information is required

for an eye examination, and the answer is really quite simple:

Because the eyes are connected (via the blood stream and nervous

system) to every part of the body, and because the eyes and vision

are affected by many general health conditions, medications, and

genetic influences which are shared by or inherited from your family

members.

Diabetics, in particular, should be asked about how long they have

had diabetes, the specific medications they are using for diabetes

treatment, the previous diagnosis of any diabetes complications (eye,

kidney, nerve or vascular), the frequency and range of home blood

glucose readings, the most recent home reading, and the results of

their last glycosylated hemoglobin test.

As we have seen in previous chapters, the answers to these questions

will give the eye doctor a good sense of overall diabetes control and

the likelihood of finding eye complications. The patient's

responsibility is to know the answers to these very important

questions.

After conducting a case history, the patient is typically asked to

read the eye chart wearing any corrective lenses previously

prescribed.

This is not a test, nor anything to be embarrassed about if the

letters are unclear. Guessing is absolutely allowed, as the true

definition of " visual acuity " is the smallest letters that can, just

barely, be identified correctly.

The results allow the doctor to gauge just how far off the

prescription might be, or the effects of any eye diseases (cataracts,

diabetic retinopathy, keratopathy, to name just 3 of many

possibilities) that will be uncovered in subsequent parts of the eye

exam.

A test of `stereopsis' (stereo vision, or the ability to see three-

dimensionally) may be given, which precisely measures depth

perception and helps evaluate how well the two eyes work together.

Color vision testing also may be performed. In my experience, this is

an important test, as academic research (including a study in which I

participated while in optometry school) shows that diabetic

retinopathy can cause short wave length ( " tritan " aka " blue/yellow " )

color vision defects. In fact, some researchers believe that subtle,

acquired color vision deficiencies may precede the earliest stages of

diabetic retinopathy by months to years.

I have consistently uncovered blue/yellow color vision deficits in

longstanding diabetic patients without ophthalmoscopically detectable

retinopathy, primarily through use of " short wave length automated

perimetry " (SWAP), a sophisticated visual field test that isolates

function of the retina's blue/yellow cones (S-cones).

The patient's pupil reactions should be evaluated by shining a bright

light into each eye. This checks the neurological integrity of the

connections between the optic nerve and the brain, and many optic

nerve diseases (including advanced glaucoma and ischemic optic

neuropathy) may be first detected this way. Many diabetics are found

to have `sluggish' pupil responses, and this suggests some degree of

autonomic neuropathy affecting Cranial Nerve III.

The patient also is asked to follow a moving target with her eyes

only, which allows the doctor to evaluate the function of the six

extra-ocular muscles and assess any possible paresis or double vision

from diabetic nerve palsy.

A test of peripheral vision may be given, which may be as simple as

detecting the number of fingers the examiner is holding up, or as

sophisticated as a computerized 'visual field' test that more

precisely determines the extent and sensitivity of a patient's

peripheral vision in relationship to thousands of other patients (a

normative database). All patients, diabetics included, should have

their visual field checked by professional examination regularly, as

visual field loss can be very subtle until severe damage has occurred

(as in glaucoma). Such testing also represents the least expensive

and invasive technique for assessing the integrity of the entire

visual pathway (from eye to brain) and uncovering much serious

neurological disease.

At some point, the patient will be " refracted, " the process through

which a new eyeglass prescription is determined (`tell me which lens

choice is better, choice #1 or choice #2'). No part of an eye

examination is probably more frustrating to patients than this test:

Oftentimes, neither of the two choices is clear, or both choices look

identical. Take heart - this is entirely normal; the test

intentionally forces the patient to pick between `crummy choices' or

choices that look virtually the same. Also, no one answer counts very

much at all. The examiner is looking for consistency and will show

the same choices repeatedly (even though you may not be aware of it!)

When the test is completed, the prescription almost always is

correct, and vision will be as clear as the patient is capable of

seeing. If the doctor is a sub-specialist, such as a retina or

glaucoma sub-specialist to whom your regular eye doctor has referred

you, refraction may or may not be done.

Several points about `refraction' should be of particular interest to

diabetic patients. Changes in blood sugar can have a dramatic impact

upon your prescription, so it is important that you and the doctor

know if your overall blood sugar control is good (as reflected by

recent HbA1c testing), and if your blood sugar level the day of the

eye exam is high, low or relatively normal (as reflected by home

blood glucose testing that day). Dramatic prescription changes may be

the result of poor glycemic control, which should be corrected before

getting a new eyeglass or contact lens prescription.

Diabetics sometimes have more difficulty than usual discriminating

between the various choices presented during refraction. This may be

due to loss of contrast sensitivity from keratopathy, cataract, or

retinopathy (I personally prefer to perform a specialized test of

contrast sensitivity on all diabetics.) Decreases in nearsightedness,

or increases in farsightedness, especially in one eye more than the

other, are often signs that the patient has diabetic macular edema

and should alert the patient and doctor to this possibility.

All patients should have their eyes examined by a `slit lamp,' a

specialized microscope that gives the examiner a highly magnified

view of the eyes. The patient places her chin on a chinrest, and a

bright (slit of) light is shined on various parts of the eye,

including the cornea and conjunctiva, the iris, the lens, the

anterior vitreous, the tear ducts and the eyelids. This allows the

doctor to detect any sign of diabetic cataract, keratopathy, abnormal

blood vessel growth on the iris (the cause of 'neovascular glaucoma')

or blood cells that might signal vitreous hemorrhage. A fluorescent

dye may be dabbed into the eyes, which is especially useful for

detecting keratopathy of the corneal epithelium. Measurement of

intraocular pressure (tonometry) also may be performed with this

instrument, a similar hand held device, or a machine that blows

a `puff' of air at the cornea. Examination of the eye's internal

drainage canal, with a specialized, mirrored contact lens, may also

be performed at the slit lamp microscope.

Eye drops should be placed into the eyes that dilate the pupils.

Drops typically take 15 to 30 minutes to work, cause blurred vision

and make patients more sensitive to light. Once the pupils are

dilated, the internal eye is examined once again with the slit lamp

microscope, very powerful hand held lenses or other instruments which

allow the doctor to visualize the posterior vitreous, optic nerve and

retina in considerable detail. A combination of techniques and

instruments is often used to ensure completeness. Use of the slit

lamp microscope to view the retina and optic nerve is very important,

because the doctor is able to use both of her eyes to examine the

patient in stereo (3-D), a feature which is critical for assessing

diabetic macular edema, as well as optic nerve cupping from glaucoma.

The eye doctor may recommend other tests depending upon the patient's

particular diagnosis, including retinal or optic nerve photographs to

document baseline findings and subsequent changes, more sophisticated

visual field testing, or a retinal dye test called " fluorescein

angiography " (a fluorescent dye is injected into the vein of a

patient's arm, and travels to the blood vessels of the retina which

are photographed, allowing the doctor to evaluate retinal

circulation.) After all tests have been completed, the eye doctor

should explain her findings and treatment recommendations to the

patient in understandable detail, and ensure the patient's questions

are answered. Sometimes, the patient may be referred to an ophthalmic

sub-specialist for further evaluation.

At the conclusion of the eye exam, every patient should know their

diagnosis, be informed of various available treatment options as well

as the doctor's recommended treatment plan, the prognosis for her

condition, and exactly when she should have an eye examination again.

For the diabetic patient, special emphasis is placed on those

findings pertaining to `diabetic eye disease.' The doctor should

discuss the need for prescription lenses, including any changes in

prescription, particularly as those changes relate to diabetic

cataract or retinopathy. The patient should be advised as to the

presence or absence of any eye muscle abnormalities due to diabetic

cranial neuropathy, as well as the presence or absence of diabetic

keratopathy, cataract, glaucoma or other optic neuropathy, and

retinopathy or other retinal abnormality.

If diabetic eye disease (or any eye disease) is detected, the

doctor's recommendations and treatment plan should be explained in

detail (written instructions are ideal), the next appointment date

should be established (always one year or less) and a letter

describing the patient's eye exam findings should be sent promptly to

each of his/her doctors. All of the patient's questions should be

encouraged and answered, and the doctor's availability to answer

future questions firmly established.

It is the eye doctor's professional and ethical responsibility to be

thorough, knowledgeable, and caring, and to know her limits if there

is some aspect of a given patient's care with which she is not

totally familiar and comfortable. Consulting with a diabetic

patient's other health care providers, or referring that patient to

another eye doctor who has more experience with a particularly

unusual or difficult problem, are not signs of inexperience, but of

excellent professional judgment.

I will close this discussion with some key questions that I believe

every patient with diabetes should ask her eye doctor:

Questions to Ask Your Eye Doctor

1. Do you have a lot of experience with diabetes and its various

effects on the eyes?

2. Do you (or do other doctors in your practice) have any special

interest in diabetic eye disease?

3. Do I have any signs of diabetic eye disease? Do I have any

cataract, glaucoma, corneal problems, retina problems or eye muscle

problems that are being caused by diabetes?

4. Has my eyeglass prescription changed significantly? If it has, is

it likely caused by poor blood sugar control?

5. If I don't have any diabetic eye disease, when do you want to see

me again?

6. If I do have diabetic eye disease, how do you recommend we manage

or treat it? When do you want to check my condition again? Are you

experienced with the surgical or laser treatment of diabetic eye

disease? If my condition worsens, will you refer me to a sub-

specialist?

7. Do you have any recommendations on how to avoid or reduce eye

complications from diabetes?

8. Will you send a report of your diagnosis and recommendations to my

other doctors? Would you like me to ask my diabetes doctor to send

you a report of her findings and recommendations?