Retinoscopy

What is retinoscopy?

Retinoscopy is an eye test that lets an eye care specialist find and measure refractive errors using special handheld tools and light that reflects off the retinas inside your eyes. While advances in technology mean eye specialists have other ways to measure refractive errors, this technique remains extremely common and it’s frequently a part of routine eye exams.

Retinoscopy is especially useful for eye tests on people who can’t communicate with their eye specialists. Have you ever wondered how infants or people with language difficulties and barriers can get prescription vision correction? The answer is retinoscopy.

In addition to very young children and people who can’t speak the same language as their eye specialists, retinoscopy is also vital for people with intellectual difficulties or age-related brain diseases. There’s also a subtype of retinoscopy that lets your specialist diagnose trouble focusing your eyes at different distances.

How does retinoscopy work?

Retinoscopy relies on how light travels through the corneas and lenses of your eyes and reflects off your retinas. If the light entering your eyes is bright and direct enough, the reflection causes a glow in your pupils that’s visible to others. Experts call that “fundus reflex” or “ “red reflex.”

When you have an eye exam, a key part of that exam is testing your visual acuity to see if you have normal 20/20 vision. When you have 20/20 vision, light rays bouncing off your retinas should line up so they’re parallel when they leave your eyes. But if you have a refractive error, the error bends those rays differently, causing some of them to misalign. Retinoscopy lets an eye care specialist find which vision corrections make the light rays align correctly. Those corrections become your prescription.

Retinoscopy can also help with diagnosing refractive errors when you have eye conditions like:

• Amblyopia (lazy eye)
• Presbyopia (age-related loss of up-close focusing ability)
• Strabismus (eye misalignment)

What should I expect before retinoscopy?

In most cases, you won’t need to prepare for retinoscopy (either on its own or if it’s part of a broader eye exam). There are a few exceptions, but these are usually very specific. Your eye specialist will tell you if this is the case before your exam. They’ll also let you know how long before your exam you’ll need to stop wearing your contacts.

To do standard retinoscopy, an eye care specialist first has to use eyedrops that contain cycloplegic medications. Those medications keep your eyes from trying to automatically focus during this test, which makes it harder for your eye specialist to determine your prescription.

If your provider is going to do dynamic retinoscopy, they won’t use cycloplegic medications before doing it. That test relies on your eyes’ natural focusing reflex.

What should I expect during retinoscopy?

During retinoscopy, your eye specialist will have you seated in an exam room with the lights dimmed. You’ll sit in front of them, and you’ll be facing each other. One of the tools they’ll use is a retinoscope. This is a handheld tool that looks like someone combined a heavy-duty flashlight and a magnifying glass. The magnifying window and light on the top of the retinoscope are set up so your eye specialist can shine the light into your eye and look closely at your eye at the same time.

The other key part of retinoscopy is a way to test different lens strengths and how they affect the reflected light in your pupils. There are two main ways they can do this:

• A phoropter. This device looks like a butterfly-shaped mask with two holes in it that you can see through. Phoropters have adjustable lenses and settings that let your eye specialist test many different prescriptions relatively quickly.
• Handheld lenses. These can come in the form of a “lens card,” which is a flat sheet with several labeled lenses of different strengths embedded in it. They can also be individual “loose” lenses. The lens card lets your provider try several different lens strengths quickly, while using the loose lenses is a meticulous, step-by-step process of trying one lens at a time.

When your eye specialist shines their light through each lens into your eye, they’re watching your pupils for specific changes in the reflected glow. Those changes include:

• Movement of the glow. Your provider uses the way the glow moves to know if the lens they’re trying is too strong or not strong enough.
• Angle of the glow. The glow’s angle tells your provider if you have an astigmatism.
• Appearance of the glow. The way the glow looks is part of how your provider knows if they’ve found the right prescription for you.

When your eye specialist shines their light through a lens and into your eye, they’ll move the light up and down, left and right, and diagonally several times. They’ll also change out the lenses they use while they do this. Your provider will probably repeat these actions several times and will stop at different points to adjust the light on the retinoscope or take notes.

Dynamic retinoscopy

One specific approach to retinoscopy tests your eyes’ ability to focus up close. When your eyes focus up close, that’s called “accommodation.” An eye specialist can test this ability using a technique called dynamic retinoscopy.

If your specialist is using dynamic retinoscopy to test your eyes’ focusing ability, the procedure is similar but may not involve magnifying lenses. Instead, your specialist will have you look at objects at different distances. Some of those objects will be between you and your specialist, while others will be behind your specialist (but still visible just to their side or over their shoulder).

While you look at these objects, your provider watches the glow in your pupils from their retinoscope’s light. The way the glow moves lets your provider judge if your eyes’ accommodation ability works as it should.

What should I expect after retinoscopy?

If your provider used cycloplegic medication to dilate your pupils or block your eyes’ accommodation reflexes, your eyes will stay dilated for a while after your exam. The time it takes for these medications to wear off varies. Your eye specialist can tell you about how long you should expect that to take.

Your eye specialist may also give you temporary sunshades or a shading cover to wear over your glasses. Cycloplegic medications also paralyze your pupils, which means they can’t narrow in bright conditions to reduce how much light enters your eyes.

What are the risks of this test?

Retinoscopy has almost no risks or side effects. There are some side effects that cycloplegic mediations can cause, but these are usually minor. And some people who are sensitive to bright light may find parts of retinoscopy less pleasant, so if you have light sensitivity (photophobia), be sure to tell your eye specialist at the start of your exam. Your eye specialist can also answer any questions or concerns about cycloplegic medication side effects.

What type of results will I get?

After your eye care specialist finishes the retinoscopy test, they’ll calculate your vision prescription (or the prescription of your loved one who was undergoing this test). The prescription works the same way as a prescription from a subjective refraction exam. Your specialist can tell you about your prescription, including what it means for you.

If the results don’t show normal 20/20 vision, what happens next?

If you or your loved one doesn’t have normal 20/20 vision, your (or their) eye specialist will talk to you about prescription vision correction. The most common forms of correction are eyeglasses or contact lenses, but vision correction surgeries like LASIK are also available for some people.