Vision screening vs. comprehensive eye exam: What’s the difference?
It’s possible to get both of these tests for the eyes. Might one be better than the other for a particular person’s eyes? Find out.
Eye exams may be vital for a person’s vision, as well as their overall health. But millions of people don’t get them annually.
According to the Centers for Disease Control and Prevention, 4 in 10 adults in the United States are in danger of vision loss, yet 40% of those individuals have not received an eye exam over the last year.1
Some people may think that meeting with an eye care provider is only necessary for those who wear prescription glasses or contact lenses. But getting an annual eye exam may also help find early signs of certain eye diseases. It may even check for health conditions that are not related to the eyes.
Some people may have heard that there’s a comprehensive eye exam and a vision screening. Might they be the same appointment? Or might someone need to get one or the other (or both) to help their vision?
Learn the differences between the 2 types of eye assessments and what to expect from each one.
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What might happen during a vision screening?
“A vision screening is a very brief assessment of one’s vision,” says Jen Wademan, O.D., an optometrist at Bidwell Optometry in Folsom, California.
Vision screenings may be conducted for a range of ages. Babies may get a vision screening where a professional checks how well the baby’s eyes follow a moving object. They may also check how their pupils respond to bright light.2
Also, vision screenings may be conducted by an adult’s doctor or a child’s pediatrician during their annual physical exam. They might test someone’s ability to see near or far. The screenings may involve reading letters of different sizes on an eye chart. This might measure the sharpness of the sight in each eye, known as visual acuity.
“In most cases, vision screenings are aimed at kids and are usually performed at school to detect if a child is not seeing well,” Dr. Wademan adds. If the provider sees a potential issue, they may recommend that the person makes an appointment with an eye care provider for a comprehensive eye exam.
What might happen during a comprehensive eye exam?
An annual comprehensive (or complete) eye exam may last up to 30 minutes and may be divided into 3 distinct parts, notes Dr. Wademan.
Part 1: “When a patient comes for their yearly comprehensive eye exam, the first part involves gathering information about their overall eye health, their medical health, their family’s health history and any symptoms they may be experiencing,” she says.
Part 2: This focuses on vision exams. These include reading the eye chart up close and at a distance. The eye care provider may be looking to see if a patient might be:
- Nearsighted (objects at a distance appear blurry)
- Farsighted (objects nearby appear blurry)
- Have an astigmatism (objects may appear blurry at a distance or nearby)
“[It’s] where we’d be figuring out and finalizing a prescription for glasses or contact lenses,” says Dr. Wademan. A special device called a phoropter may be used to determine the right prescription.
The eye care provider may test how well the pupils respond to light by shining a bright light into the eyes. Peripheral (side) vision and eye muscle movements may also be examined.
Numbing eye drops may also be put in the eyes before the doctor tests the pressure inside the eyes. There are 3 different methods that can be used to test eye pressure, or tonometry.
Each may involve slightly flattening an area of the cornea.3 The purpose of this eye pressure test may be to screen for glaucoma, an eye disease that may damage the optic nerve and may lead to vision loss or even blindness. Approximately 3 million Americans may be living with glaucoma, and it’s the second leading cause of blindness worldwide.4
“Glaucoma is often referred to as ‘the silent thief of sight’ because the patient doesn’t really have many visual symptoms until they have lost some visual function,” notes Dr. Wademan. “So, while someone may have 20/20 vision, they may also have genetic factors or higher eye pressure putting them at a greater risk of glaucoma. An optometrist wants to monitor the situation in order to prevent visual loss.”
Part 3: Lastly, eye drops may be used to dilate or widen the pupil. “The dilation is to allow for a more extensive view inside the eye,” says Dr. Wademan. “Think of the pupil like a window and once the dilation drops are put in, it’s like the window is opening.”
As the patient looks into a bright light on a slit-lamp microscope with dilated eyes, the eye care provider may be able to look at the cornea and lens in front of the eye. They may also be able to see the retina and optic nerve located at the back of the eye.
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What conditions might a dilated eye exam screen for?
This simple test may be screening for numerous eye conditions. These might include:
- Cataracts, an age-related eye disease that affects more than half of U.S adults ages 80 and over5
- Age-related macular degeneration, an eye disease that may blur central vision6
Other illnesses may lead to vision loss, too, explains Dr. Wademan. For example:
- People who are living with type 1 or type 2 diabetes may need to be screened for diabetic retinopathy, an eye condition that affects blood vessels in the retina and may cause vision loss or blindness.7 “Sometimes we can see changes in the eye before the patient even knows that they have blood sugar issues,” she adds. High blood pressure may also cause blurry vision or vision loss.8
- Certain autoimmune conditions may have an impact on the eyes. These include Graves’ disease, which could be the most common cause of an overactive thyroid (hyperthyroidism).9 Another might be Sjögren’s disease, a disorder where the immune system attacks the glands that make moisture in the eyes, mouth and other parts of the body.10
“In general, dilation primarily impacts a patient’s reading vision for a couple of hours, but distance vision is usually minimally affected,” explains Dr. Wademan. “However, a certain population, including those on some medications, will not be able to drive after having their eyes dilated, but their eye care provider will tell them before the appointment.”
Overall, Dr. Wademan believes patients who undergo a yearly comprehensive eye exam have every reason to feel empowered. “Similar to going to the dentist every 6 months for a cleaning, meeting with an optometrist once a year is a good healthy habit,” she says. “It’s about being proactive about your eye health.”
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Sources:
- Fast facts: 4 in 10 adults at high risk for vision loss Centers for Disease Control and Prevention, last reviewed May 2024.
- Vision screening National Library of Medicine: MedlinePlus, last reviewed December 2022.
- Tonometry National Library of Medicine: MedlinePlus, last reviewed August 2022.
- Vision and eye health: about glaucoma Centers for Disease Control and Prevention, last reviewed May 2024.
- Cataracts National Eye Institute, last reviewed November 2023.
- Age-related macular degeneration National Library of Medicine: MedlinePlus, last reviewed August 2023.
- Diabetic retinopathy National Eye Institute, last reviewed June 2024.
- How high blood pressure can lead to vision loss American Heart Association, last reviewed May 2024.
- Graves’ disease American Thyroid Association, last reviewed 2024.
- Sjögren’s disease National Institute of Arthritis and Musculoskeletal and Skin Diseases, last reviewed June 2024.
