Last updated: 02/17/2009

Diagnosis

The diagnosis of cataract is usually made when the patient begins to notice changes in his or her vision and consults an eye specialist. In contrast to certain types of glaucoma, there is no pain associated with the development...

of cataracts. The specific changes in the patient's vision depend on the type and location of the cataract. Nuclear cataracts typically produce symptoms known as myopic shift (in nearsighted patients) and second sight (in farsighted patients). What these terms mean is that the nearsighted person becomes more nearsighted while the farsighted person's near vision improves to the point that there is less need for reading glasses. Cortical and posterior subcapsular cataracts typically reduce visual acuity; in addition, the patient may also complain of increased glare in bright daylight or glare from the headlights of oncoming cars at night.

Because visual disturbances may indicate glaucoma as well as cataracts, particularly in older adults, the examiner will first check the intraocular pressure (IOP) and the anterior chamber of the patient's eye. The examiner will also look closely at the patient's medical history and general present physical condition for indications of diabetes or other systemic disorders that affect cataract development. The next step in the diagnostic examination is a test of the patient's visual acuity for both near and far distances, commonly known as the Snellen test. If the patient has mentioned glare, the Snellen test will be conducted in a brightly lit room.

The examiner will then check the patient's eyes with a slit lamp in order to evaluate the location and size of the cataract. After the patient's eyes have been dilated with eye drops, the slit lamp can also be used to check the other structures of the eye for any indications of metabolic disorders or previous eye injury. Lastly, the examiner will use an ophthalmoscope to evaluate the condition of the optic nerve and retina at the back of the eye. The ophthalmoscope can also be used to detect the presence of very small cataracts.

Imaging studies of the eye (ultrasound, MRI, or CT scan) may be ordered if the doctor cannot see the back of the eye because of the size and density of the cataract.

Preparation

ECCE is almost always elective surgery—emergency removal of a cataract is performed only when the cataract is causing glaucoma or the eye is severely injured or infected. After the surgery has been scheduled, the patient will need to have special testing known as keratometry if an IOL is to be implanted. The testing, which is painless, is done to determine the strength of the IOL needed. The ophthalmologist measures the length of the patient's eyeball with ultrasound and the curvature of the cornea with a device called a keratometer. The measurements obtained by the keratometer are entered into a computer that calculates the correct power for the IOL.

The IOL is a substitute for the lens in the patient's eye, not for corrective lenses. If the patient was wearing eyeglasses or contact lenses before the cataract developed, he or she will continue to need them after the IOL is implanted. The lens prescription should be checked after surgery, however, as it is likely to need adjustment.