While there are some basic eye vision tests common to most eye exams, children and young adults have different vision testing needs than say, a healthy middle-aged adult or an adult with a history of eye problems. In other words, certain tests check your vision and determine whether you require glasses or contacts, whereas other tests evaluate your eye health and check for eye diseases and overall health.
Vision testing equipment ranges from simple tools like the “Big E” eye chart (Snellen Chart), a hand-held penlight and eye cover, to more complex devices that swap lenses in front of your eyes or use special lamps to view the eye’s structure. A comprehensive eye exam includes vision testing equipment that is common to almost all eye exams but is often tailored to your age, your specific need, or your individual symptoms. The following are some common tests you may be given during a routine eye exam.
Autorefractors determine a person’s refractive error and prescription for glasses or contact lenses by measuring how light changes as it enters the eye.
While seated with your chin in a stabilizing chinrest, you’ll be asked to focus on an image or point of light. The autorefractor automatically determines the correction needed to place your focus point on top of the retina, the light-sensitive area at the back of the eye responsible for correctly processing images.
Autorefractors are particularly useful when dealing with non-communicative people or patients who have trouble sitting calmly during an extended exam, such as young children or those with special needs
Eye dilation is a critical component of a comprehensive eye exam, and vital to the detection of symptoms of serious eye diseases and overall physical health. The eye drops used for dilation cause your pupils to widen, enabling more light to enter your eye and giving your doctor a better view of the back of your eye. Doing so helps your doctor diagnose common diseases and conditions at their earliest stages, such as diabetes, macular degeneration, glaucoma, high blood pressure and retinal detachment.
Glaucoma refers to a group of eye diseases that damage the optic nerve of the eye, preventing the eye from sending accurate visual information to the brain.
Glaucoma testing involves measuring internal eye pressure and a detailed scan of the retina for signs of disease.
How Does Glaucoma Testing Work?
One glaucoma test, called a Puff Test, measures what happens when a puff of air is blown across the surface of the eye. Another test uses a special device (in conjunction with eye-numbing drops) to touch the surface of the eye to measure eye pressure.
While increased eye pressure is a key indicator of the disease, it does not necessarily mean you have glaucoma. In fact, the only way to detect glaucoma is to have a detailed, comprehensive eye exam that often includes dilation of the pupils in order to examine the retina and optic nerve at the back of the eye for signs of the disease.
Ophthalmoscopy examines the back part of the eye, called the fundus, which includes the retina, optic disc, choroid, and blood vessels. It can easily help your eye doctor see symptoms or indicators of eye diseases.
There exist two types of ophthalmoscopy.
Direct ophthalmoscopy: Your eye doctor shines a beam of light through the pupil using an instrument called an ophthalmoscope. It’s about the size of a small flashlight that can magnify up to about 15 times.
Indirect ophthalmoscopy: Your eye doctor holds your eye open while shining a very bright light into the eye using an instrument worn on the head. Doing so gives the doctor a wider view of the inside of the eye, or fundus, even when the lens is clouded by cataracts.
An optomap retinal exam allows your eye doctor to provide you with the most comprehensive eye exam possible, by capturing more than 80% of your retina in one panoramic image. This ultra-widefield (200°), high-resolution image, enables eye doctors to detect underlying eye diseases and monitor treatment for existing ocular diseases.
There are many benefits of the optomap retinal exam, especially for patients who are reluctant or unable to have their pupils dilated, as the optomap can usually be performed without dilation.
Peripheral Vision Test
Eye doctors almost always include a peripheral vision test as part of a comprehensive eye exam to evaluate the range of your “out-of-the-corner-of-your-eye” vision.
Since peripheral vision loss can be a sign of a number of eye diseases, including glaucoma and other optic nerve disorders, side vision must be tested regularly.
The most common type of peripheral vision testing is confrontational peripheral vision testing, where your eye doctor asks you to focus on a target directly in front of you (the doctor’s eye, or an upraised finger, for example). With one eye covered, and your focus trained on the target, you’ll be asked to describe things you see in the side of your vision.
If during an eye examination, your doctor has discovered a vision problem like nearsightedness, farsightedness, or astigmatism, it’s likely that one of the next steps you’ll take will involve a phoropter. A phoropter is a special machine used to switch multiple lenses in front of your eyes to correct your vision.
Phoropters look imposing—like space-age visors—but are really an ingenious way to quickly determine the exact vision correction needed for each of your eyes.
Most people who’ve had a comprehensive eye exam are familiar with the puffer test. A puffer test is exactly as it sounds: with your head resting in the chinrest of a diagnostic machine called a slit lamp, your eye doctor prompts a puff of air to jet across the surface of the eye to measure the intraocular pressure, or inner pressure, of the eye.
This enables the doctor to determine whether or not you have glaucoma, as elevated pressure levels are a key indicator of glaucoma, a series of eye diseases that attacks the optic nerve.
A retinoscope is a handheld device used by eye care professionals to determine your visual acuity. The test is quick, easy, accurate, and requires minimal cooperation from the patient.
During a retinoscopy, the eye doctor uses a retinoscope to shine light into the patient’s eye and observes the reflection (reflex) off the patient’s retina. Depending on the person’s refractive error, as the practitioner moves the retinoscope, the reflex will move in a certain way within the pupil.
A retinoscopy can be especially good for young children or people with special needs who might have problems accurately describing any issues with their vision.
Slit Lamp Exam
If you’ve ever had a comprehensive eye examination, chances are you’ve had a slit lamp exam. Slit lamp tests are designed to help your eye doctor magnify and examine the eye from front to back.
With your head resting in a machine called a slit lamp, your eye doctor can use a combination of bright light and different magnifying lenses to view your eye’s structure.
This type of test can be used to spot indicators of a wide variety of diseases and conditions including cataracts, glaucoma, diabetic eye disease, age-related macular degeneration, even blood disorders, and certain cancers.
Hopefully, by now you’ve seen one. The projected or wall-mounted Snellen eye chart, usually topped by the big letter “E”, is a common test used to measure your visual acuity at multiple distances.
Arranged as a pyramid of sorts, the letters in the Snellen chart are specifically chosen and arranged to test your sharpness and clarity of vision at a baseline distance of 20 feet.
Handheld versions of Snellen charts are used for testing near vision as well.
By viewing or reading each line from top to bottom (with one eye covered at a time), your eye doctor can determine the quality of your visual acuity or sharpness. Where a line of characters begins to become difficult to see is the approximate measurement of your vision.
The Snellen chart serves as a beginning—not an end—to a comprehensive eye examination.
A vision screening is no substitute for a comprehensive eye exam performed by an eye doctor. But it can play an important role in helping numerous groups get the vision testing they need.
You may have received a vision screening at work or at school many years ago, or perhaps you had a vision screening when you renewed your driver’s license. Vision screenings are last a few minutes and are typically performed by volunteers, school nurses, or DMV employees.
During a vision screening, you will be tested for major problems as quickly as possible, such as your distance vision. This is generally done by reading the letters on an eye chart.
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