Eye Examinations, Glasses & Contact Lenses

A comprehensive medical eye exam is so much more than just checking for glasses! Read below about some of the procedures that are part of a complete medical eye examination at Callahan Eye.


Refraction and Visual Acuity Test

Visual acuity is the sharpness or clearness of vision. It is dependent on many factors within the eye as well as the brain. Visual acuity is measured by testing the ability of each eye to see letters of varying sizes at a fixed distance.

Refraction is a test that measures the eyes’ need for corrective lenses—i.e. the refractive error, often referred to as myopia (nearsightedness) or hyperopia (farsightedness). In addition to determining glasses and contact lens prescriptions, refraction is important to determine a person’s best-corrected visual acuity. This is important for assessing the overall health of the eyes as well as the severity of many eye diseases.

Slit Lamp Exam

The slit lamp is a specialized microscope used to examine the eye and its surrounding structures. With the slit lamp, Dr. Callahan will closely examine the eyelids, cornea, iris, lens and the space between the iris and cornea (the anterior chamber). She may also use the slit lamp to examine the optic nerve and parts of the retina, including the macula.


This test is done at the slit lamp and is the measurement of the pressure within your eye (intraocular eye pressure or IOP). Abnormal IOP may be a sign of glaucoma or other problems within the eye. The test is painless and does not involve a puff of air.

Dilated Retinal Exam

This is perhaps the most important part of the eye exam. When your eye is dilated, the pupils are wide open so inside of the eye may be examined. Using the slit lamp and/or an instrument called an ophthalmoscope, Dr. Callahan will evaluate the lens, optic nerve and retina. This is important for diagnosing cataracts, glaucoma, macular degeneration and other ocular diseases.

When and How Should Screening Be Done?

The American Academy of Ophthalmology now recommends that adults with no signs or risk factors for eye disease have a baseline comprehensive eye exam by an ophthalmologist at age 40. For more information, click here.

When Should My Child Have His or Her First Eye Exam?

Dr. Callahan recommends a comprehensive eye examination by an ophthalmologist for healthy children prior to starting kindergarten. For more information click here.