FAQ
The refraction is that part of the exam where the eyes are tested for glasses. Many people see poorly because their eyes are out of focus. The refraction determines what lenses are needed to best focus the eyes for the sharpest possible visual acuity. Typically, the refraction is done by having the patient view an eye chart through an instrument called a phoropter. The phoropter holds corrective lenses that are custom adjusted by the technician or doctor to match the patient’s eyes, determining best vision, and providing the doctor with the information needed to prescribe proper glasses.
Why must my eyes be dilated for an exam?
When your eyes are dilated, the doctor can get a much better view of the inside of your eye, especially the retina, macula, optic nerve, and vessels. Also, your best refraction can often be obtained only after dilation, especially in children or those with opacities such as cataract. The dilating drops relax the iris muscle that closes the pupil, and stimulate the muscle that opens the pupil. The dilation wears off on its own, usually in just a few hours. It is true that dilation increases light sensitivity, so that dark glasses are offered as a courtesy, and caution is recommended in driving, especially on bright days.
Pupillary dilation is required for many eye surgeries, and may also be required in the treatment of certain eye diseases, especially inflammatory disease such as iritis.
What does 20/20 mean?
The vision test is one of the simplest yet most important components of the eye exam. In order for eye doctors to compare results, it’s always done at a standardized distance of twenty feet. Each line of the eye chart is assigned a notation that represents the distance an eye with “normal” vision can read. For example, if you read 20/40, you’re able to see at 20 feet what a normal eye could see at 40.
What is a visual field test and why do I need one?
The visual field is used to test and monitor peripheral vision. It gives the doctor very important information about the function of the retina, optic nerve, and brain. This test monitors certain eye diseases, such as glaucoma, and also screening before certain surgeries.
When do I need a glare test?
Glare occurs when a bright window, headlight or sunshine interferes with seeing objects in the foreground. The person may be forced to rely more frequently on dark glasses or avoid driving. Glare occurs when light enters the eye and bounces off an opacity such as a cataract. Glare is often the first symptom of cataract, and can be underestimated unless it is specifically tested for.
While the patient looks at an eye chart, a light is shined from the side in such a way as to simulate the effect of bright sunlight or headlights at night. The results are then compared with acuity tested in a dark room. The results of the test are important when considering whether cataract surgery may be indicated.
What is an IOP check?
Simply stated, the intraocular pressure (IOP) is the hardness of the eyeball. The IOP is measured with a device called a tonometer. The technician or doctor numbs the eye with a drop, and gently touches the front of the eye with the tonometer to determine its hardness. The hardness of the eye is primarily a function of its internal water pressure (IOP), a balance between production and drainage of the clear fluid inside the eye. If the IOP is elevated, it can cause damage to the optic nerve through a disease called glaucoma. Since elevated eye pressure usually causes no symptoms, it must be specifically tested for as part of the eye exam. Elevated IOP can be treated, but periodic IOP checks must be performed to be certain it is safely controlled.
What are flashes and floaters?
Flashes or flickers of light in one or both eyes, or floating spots or strings in the vision can be normal, or can be symptoms of serious eye disease. Generally these symptoms are a harmless nuisance caused by aging changes in the gel part of the eye called the vitreous. However, they can also be a symptom of a serious retinal condition, and should be promptly evaluated by the ophthalmologist.
