Eye Exam

Vision problems can occur in anyone at any time. While some vision problems are hereditary, many are not. While not start in youth, others develop with age. This is why regular eye exams are important. They can help you detect and correct vision problems before they become too severe. A typical eye exam will include all of the following:

External examination

When you have an eye exam, the eye care practitioner will take a minute to check out the outside of your eye. This means they will inspect the eyelid and the surrounding tissue. If you go in with a problem they will likely check the orbital rim, and palperbral fissure as well. They will also inspect the conjunctiva and sclera by having you look up, and shining a light while retracting the upper or lower eyelid. The cornea and iris may be similarly inspected to ensure they are functioning the way they should be.

Visual acuity

One of the tests you will have when getting an eye exam is that of visual acuity, or in other words, the eye's ability to detect fine details, and see in-focus images at specific distances. Normal visual acuity is 20/20, which means standard sized objects can be seen by a person with normal vision at a given distance. If you have worse visual activity than the normal person you will be given a lower score, such as 20/40. This means that are 20 ft you can see what a person with normal vision can see at 40 ft. In other words, at 40 ft you can't see it, but at 20 ft. you can. In Europe and Australia vision is measured in meters rather than feet, so you might also see visual acuity marked as 6/6, which is equivalent to 20/20 vision. Vision that is 20/10 is when you have better visual acuity than is typical.

Pupil function

During this part of an eye examination, your eye care practitioner is look at the pupilary function, which includes inspecting the pupils for equal size, a normal shape, that they are reactive to light, and reactive to direct and consensual accommodation.

If your eye care professional suspects neurological damage, they may do a swinging-flashlight test to assess optic nerve anomalies. This test detects the afferent pupil defect, also referred to as the Marcus Gunn pupil. Basically the way it works, is your reaction is tested; in a normal reaction to the swinging-flashlight test, both pupils constrict when one is exposed to light, as the light moves away from the eye, both eyes begin to dilate, but constrict again when light has reached the other eye. Basically, if there is an efferent defect the results will be different. For example, if the defect is in the left eye, the left pupil will remain dilated regardless of where the light is shining, and the right pupil will respond normally. If there is an afferent defect in the left eye, both pupils will dilate when the light is shining on the left eye, but both will constrict when it is shining on the right eye.

This test is also used to help detect Horner's syndrome, and Argyll Robertson pupil.

Ocular motility

This is a test that is performed during almost every eye exam, in fact, ocular motility should always be tested, but most especially when patients complain of double vision or if physicians suspect neurologic disease. When this test is performed the eye is first visually assessed for deviations that could result from strabismus, extraocular muscle dysfunction, or palsy of the cranial nerves innervating the extraocular muscles. Then the eye care practitioner will test for saccades, by having the patient move his or her eye quickly to a target at the far right, left, top and bottom, which reveals if the eye has the ability to jump from one place to another, and how well.

The most common test for ocular motility is that of slow tracking, also referred to as "pursuits" where the examiner will have you follow their finger with your eye as they draw an imaginary double H, which is meant to test the inferior, superior, lateral and medial rectus muscles of the eye, as well as the superior and inferior oblique muscles.

Visual field testing

If your eye care professional does not do a visual field test, find a new examiner, as an evaluation of the visual fields should never be left out of the basic eye examination. This test is done on each eye separately, and is done to assess the extent of the peripheral field of vision. To perform the test, the individual generally closes one eye, and looks at the examiner's eye with the other eye. The examiner will then hold up fingers in the four different quadrants of vision and ask you how many they held up. If you can give the correct answer for all four fields, you probably do not suffer from peripheral vision problems. However, if you can't, they will then test to see what visual problem you may have.

Common problems of the visual field include scotoma, which means you have an area of reduced vision, or in other words a quadrant of vision you do not see as well in; hemianopia, which means that you have two quadrants of vision you do not see as well in, or in other words, half of visual field lost; homonymous quadrantanopia which means both eyes are missing areas of vision or at least not seeing as well, or bitemporal hemianopia, both eyes are suffering from half of their vision loss.

Intraocular pressure

This is not a common test during an eye exam unless you complain of a problem. Basically this is measured by any of a series of devices designed to measure the outflow, as well as the resistance to outflow, of the aqueous humour from the eye.

Ophthalmoscopy

This is again not common during a basic eye exam, but should you be having vision problems, it may be done. This is an exam where the eye care practitioner does a visual inspection of the internal eye structures. This is magnified, but they use it to assess the quality of the eye's red reflex, and to see if the retina and other tissue at the back of the eye are performing appropriately. This is best done, or has the best results if done after the pupil has been dilated with eye drops. If the pupil is not dilated, the view is limited.

During ophthalmoscopy exams the eye care practitioner is most concerned with the appearance of the optic disc and retinal vasculature. Anomalies in the appearance of these internal ocular structures may indicate eye disease or condition and could lead to serious visual problems later.

The red reflex assessment is usually done from a distance of about 50 cm and is usually symmetrical between the two eyes. If there is an opacity, it may indicate a cataract and then further testing is done to determine the severity and treatment plan.

Slit-lamp

This is a test that inspects the anterior eye structures and ocular adnexa. Basically a beam of light is passed over the eye, and the examiner will view the illuminated ocular structures through a system that magnifies the image of the eye. This allows the eye care practitioner to inspect the ocular media, and surrounding areas to ensure they are fine. The light beam can be varied in width, height, incident angle, orientation and color, for better, more accurate results.

Often before this exam is performed, a fluorescein staining is done and shows if there are problems such as corneal abrasions, herpes, or other anatomical problems with the eye. This is a common procedure to eliminate or determine if you have a specific eye condition based on symptoms present because it offers a very detailed view of the eye structures.

A typical eye exam should not take you more than a half an hour, even if it does seem complicated or long. Generally your eye care practitioner would only perform the longer more extensive tests if the original tests indicated potential problems, or if you come in complaining of common symptoms of these problems. In most cases you get light flashed in your eyes to assess the pupil function, you will read numbers in a pyramid to asses visual acuity, and your doctor will hold fingers up to test your visual fields. An eye exam is pain free, and can a very safe habit to get into, because, should the worst happen, your eye care practitioner would be able to catch any eye problems early, and help you find the appropriate treatment or corrective lens to help with it before it becomes a major nuisance.