Cataract Symptoms, Signs, Diagnosis, Tests
In the United States alone, over 20 million adults over the age of 40 have cataracts. Cataracts occur when protein builds up on the crystalline lens of the eye, causing blurred vision that worsens with time. Because most cataracts progress slowly, it may be years or months before individuals notice symptoms.
Fortunately, cataract surgery is considered one of the safest, most commonly performed medical procedures in the U.S., with approximately 98% of patients reporting positive results. When cataract symptoms do occur, be sure to notify a qualified ophthalmologist who will guide you in pursuing treatment.
Signs of Cataracts
The following cataract symptoms may indicate the presence of this common eye disease:
- Blurred vision: As the eye's natural lens becomes progressively more clouded, light is refracted, so a clear image doesn't reach the retina. Individuals with cataracts may feel as though they constantly need to rub their eyes to clear them, or may be frustrated that even stronger glasses and contact lens prescriptions aren't able to restore visual acuity.
- Changed color perception: As cataracts obscure more of a person's lens, they may experience decreased ability to see colors on the "blue" end of the spectrum. As a result, colors may seem dull or washed out, or may take on a yellowish appearance. Many patients who receive cataract surgery are surprised at how vivid colors appear following the procedure.
- Frequent increases in eyeglass or contact lens prescriptions: If cataracts have not yet been diagnosed by an ophthalmologist, patients may be given increasingly higher glasses or contact lens prescriptions in an effort to counteract the progressive decrease in visual acuity. However, because cataracts involve the physical clouding of the lens, a more powerful prescription will be unable to restore clear vision.
- Poor night vision: Because cataracts cause less light to reach the retina, vision is especially impaired in dim lighting. Driving at night may become especially difficult, especially when combined with glare from the headlights of other cars.
- Halos or glare around lights: The light distortion resulting from a clouded lens often results in halos or glares around light sources, such as lamps, headlights, or traffic lights. Individuals may also notice increased light sensitivity.
- A white or "milky" spot over the pupil of the eye: In some cases, especially at certain angles or under good lighting, a white spot can be detected on the pupil of the eye.
To achieve an accurate cataract diagnosis, your ophthalmologist will use a series of tests to evaluate the health of your eyes and the quality of your vision. Many of these tests are performed as part of a routine eye exam.
Slit Lamp Exams
To examine the health of your eyes, your ophthalmologist will first dilate your pupils with eye drops. Then, using an instrument known as an ophthalmoscope, he or she will project a high intensity light beam on the front parts of the eye, including the cornea, lens and iris. The close examination allows your ophthalmologist to see any protein build-up on the lenses, which is what causes cataracts. This direct physical examination of the eye can reveal lens opacity even before cataracts begin to affect your vision, achieving the earliest possible cataract diagnosis.
Because it is important to examine the eye for additional or alternative diseases that may be compromising vision, your ophthalmologist will also place a special lens between the slit lamp and the cornea in order to magnify the retina and optic nerve. Damage to the optic nerve may indicate increased intraocular pressure (IOP), which can indicate cataracts or glaucoma.
To determine whether the cataracts forming on your lens are affecting your vision, your ophthalmologist will test your eyesight using a Snellen eye chart. By asking you to read letters of varying sizes from a chart 20 feet away, your doctor can determine your visual acuity and track any vision loss resulting from your cataracts. If you have received a cataract diagnosis, and your visual acuity has decreased to the degree of 20/40, your ophthalmologist will likely recommend cataract surgery.
During a Snellen eye test, patients are asked to read black letters off of a white background, which creates a high level of contrast that differs significantly from real-world conditions. In fact, patients may score highly on a Snellen eye test, but still complain that they are experiencing extremely blurry vision, difficulty driving at night, and other frustrating symptoms. In order to get a more realistic view of how patients' eyes are performing on a daily basis, your ophthalmologist may present you with additional eye charts designed to measure color perception, contrast sensitivity, and reaction to glare.
Ishihara Color Test
Patients read colored numbers off of a similarly pigmented background in order to determine their contrast sensitivity. Because advanced cataracts may diminish your ability to see colors on the "blue" end of the spectrum, poor performance on an Ishihara color test may indicate that it is time to consider surgery.
Contrast Sensitivity Test
By asking a patient to identify low contrast letters or sine-wave gratings, ophthalmologists can determine how dramatically cataracts are affecting the patient's quality of vision. In certain cases, contrast sensitivity can be dramatically affected by cataracts even when a Snellen test indicates that visual acuity remains normal.
Glare Sensitivity Test
Because cataracts can cause light sensitivity, patients are asked to read the same chart twice, once in bright light, to determine eye function under varying light situations. Decreased acuity in the presence of bright light may be indicative of posterior subcapsular cataracts.
Also known as a "puff test," a tonometry test measures the fluid pressure inside the eyes. Using a blunt instrument or, more commonly, a puff of air directed at the pupil, an ophthalmologist is able to determine a patient's intraocular pressure (IOP). An elevated IOP may indicate the presence of cataracts or glaucoma, and over time may cause damage to the optic nerve. For this reason, patients with high intraocular pressure must be monitored with frequent eye exams whether or not they receive a cataract diagnosis.
Monitoring Cataract Progression
Once you have received a cataract diagnosis, your ophthalmologist will track your cataract progression with a series of eye exams. Once your visual acuity begins to diminish, your ophthalmologist will likely recommend cataract surgery. However, your daily experiences are just as important as any diagnostic test. Only you are aware how drastically cataracts are affecting your vision, and only you can determine the best time to pursue treatment.
Contact an Ophthalmologist
If you are experiencing cataract symptoms, it is important to have the health of your eyes evaluated by a medical professional. DocShop can help you locate an experienced ophthalmologist in your area today, so you can receive an accurate diagnosis and begin treatment.