Cataract Exam Overview


If you think you might have a cataract, the only way to know for sure is to have an eye examination. Should your eye care professional find a cataract, he or she can monitor it and advise you about any future treatment you may need. In order to make a cataract diagnosis, however, your doctor will ask you a number of questions about your medical history and will perform an eye exam.


A Comprehensive Eye Exam Includes

Visual Acuity Testing

The “big E” chart measures how well you see at various distances. From a specified distance — usually 20 feet — your eye care professional will ask you to read aloud progressively smaller rows of high-contrast capital letters and numbers. However, your score on the visual acuity test may not reflect functional impairments such as glare sensitivity and reduced contrast sensitivity.

Ophthalmoscope and Slit-Lamp Examination

Cataracts can be seen with an ophthalmoscope, a hand-held, microscope-like viewing instrument. After using special drops to dilate your pupils, your eye care professional will examine the internal structures of the eye to check for other eye diseases.


A tonometer is a hand-held instrument that measures intraocular pressure (the pressure of fluids inside the eye) after anesthetic drops are used. This test is performed to rule out glaucoma.

Keratometry and A-Testing

To fit you with the intraocular lens (IOL) of the proper size and magnification, your eye care professional will use a keratometer to measure the curvature of your cornea. Then the length (optical axis) of your eye will be measured using an A-scan — painless ultrasound waves — to determine the correct power of the IOL lens.


Your eye care professional may do other tests to learn more about the structure and health of your eye.