Have you ever had an eye exam? Or have you ever taken your little one to an eye specialist? At that time, you may have heard the term 'retinoscopy'. This is actually a very important step in an eye exam. Today, let's talk about what this retinoscopy is, what it does, and how important it is.
What is Retinoscopy?
Simply put, retinoscopy is a special test that an ophthalmologist uses to accurately measure your vision, or refractive errors, in your eyes. They use a special hand-held instrument and a light to do this. This light is sent into your eye, where it hits the retina at the back of your eye, and is then reflected back.
Although there are many new techniques for examining the eyes these days, this method called retinoscopy is still very popular. It is often done as part of a routine eye exam.
This method is especially important for examining the eyes of those who are unable to tell the doctor about their problems. Imagine, how can a small baby tell you about the way he sees?
Also:
- For very young children (even from birth)
- For those who do not understand the language spoken by the doctor and have language barriers
- For those with intellectual disabilities
- This test is essential when it comes to providing eyeglasses to people with age-related brain conditions (e.g. dementia) .
Another thing is that a special method called retinoscopy can also detect whether your eyes have problems focusing at different distances.
How does this work?
Okay, now let's see how this retinoscopy test works. When light enters your eye, it passes through the cornea and the lens inside the eye, and hits the retina at the back of the eye. Then the light is reflected back, just like light is reflected off a mirror.
This reflected light causes the pupil of your eye to appear red, or to glow. Doctors call this the `Fundus reflex` or `Red reflex` . You may have noticed that sometimes when you take a photo, your eyes look red, that's what happens.
Typically, an eye exam will measure your visual acuity, which is how well you have 20/20 vision . 20/20 vision is the level at which two healthy eyes can see clearly. In a person with this level of vision, light rays that are reflected from the retina should be parallel as they exit the eye.
But if you have a refractive error – nearsightedness, farsightedness, or astigmatism – these light rays are bent and do not come out in a straight line. That's when the ophthalmologist uses a retinoscopy to see what kind of lens will make these light rays come out parallel. That correction is what your prescription is. Got it?
What conditions can be diagnosed with a retinoscopy?
This retinoscopy test can also help diagnose some other eye conditions. For example:
- Amblyopia: This is also called "lazy eye." It is a condition in which one eye has less vision than the other. If detected early, it can be treated.
- Presbyopia: This is a condition that affects many people over the age of 40. It is a condition in which you cannot see things that are close to you clearly, such as looking at a book or newspaper, or threading a needle.
- Strabismus: This is what we call a cross-eye . It is when the eyes are turned to different sides instead of pointing in the same direction. It is also important to recognize this quickly.
What to expect before the test?
In most cases, you don't need to do anything special to prepare for a retinoscopy (or a complete eye exam that includes this). However, in some cases, there may be some minor things you can do. If there are any, your eye doctor will tell you about them before the exam. If you wear contact lenses, your doctor will also tell you how long before the exam you need to take them out.
Before a routine retinoscopy, your eye doctor will put special eye drops (cycloplegic medications) in your eyes. These medications stop your eyes from trying to auto-focus during the exam. If they do, it will be difficult for the doctor to accurately determine the number of your glasses.
However, if the doctor is going to perform a special procedure called dynamic retinoscopy , these drops will not be applied beforehand because the test depends on the way your eyes naturally focus.
What happens during the test?
During the exam, you will be seated in a chair in a darkened room. The ophthalmologist will sit in front of you. One of the instruments they will use is a retinoscope . This is a handheld device that looks like a powerful flashlight and a magnifying glass combined. It can shine a light into your eye and take a good look at it.
The next most important thing is to put on different sized lenses and look at the changes in the light that the pupil of your eye sees. There are two main ways to do this:
- A phoropter: This is a butterfly-shaped device that fits over your face with two holes for you to see through. It has different lenses, so the doctor can quickly fit each pair of glasses.
- Handheld lenses: These can come in the form of a "lens card," which means that each size of lens is glued onto a flat sheet. Or they can come as individual "loose" lenses. Although lenses can be quickly changed from a lens card, when using individual lenses, you have to be very careful when inserting each lens one at a time.
When the doctor shines a light through this lens into your eye, called a retinoscope, they look for specific changes in the red reflex that appears in your pupil. These changes are:
- Movement of the lens: The doctor can tell if the lens is the right size, too small, or too large by looking at the way this lens moves back and forth.
- Angle of vision: This angle of vision is what helps the doctor determine if you have astigmatism (a condition in which vision is blurred due to a slight change in the shape of the eye).
- The appearance of the lens: Once you find the right pair of glasses for you, the way this lens looks will also change.
As the doctor shines light into your eye through a lens, they move the light up and down, left and right, and across several times. They also change the lenses they use. They do this several times, stopping halfway through to adjust the light on the retinoscope, or to take notes.
What is Dynamic Retinoscopy?
Retinoscopy is a special method of examining your eyes to see things that are close to you, which is to test their ability to focus. This ability to focus near is called accommodation . Dynamic Retinoscopy is a method that an ophthalmologist can use to test this ability.
If your doctor is using Dynamic Retinoscopy to check your eye's focusing ability, the test is much the same as before, but may not use magnifying lenses. Instead, your doctor will ask you to look at objects at different distances. Some objects will be between you and the doctor, while others will be behind the doctor (but visible from the doctor's side or over his shoulder).
When you look at these things, the doctor looks at the light in your pupil through the light of his retinoscope. The way that light moves is how the doctor determines whether your eyes' ability to focus (accommodate) is working properly.
What to expect after the test?
If your doctor used eye drops (cycloplegic medications) to dilate your pupil or stop your eyes from focusing, your eyes will remain dilated for a while after the test. The time it takes for these medications to wear off varies. It can usually take a few hours. Your eye specialist will tell you how long this will last.
Your vision may be a little blurry at this time, and you may feel sensitive to the outside. Therefore, your doctor may give you temporary sunglasses (`sunshades`) to wear. Because the eye drops prevent your irises from shrinking in bright light and reducing the amount of light that enters your eyes.
Are there any risks to this test?
In fact, there are no major risks or side effects of a retinoscopy. The cycloplegic medications mentioned earlier can cause minor side effects, but they are usually minor (e.g., slight redness of the eyes, itching). Some people who have a sensitivity to bright light (called photophobia ) may find some parts of the retinoscopy procedure a bit difficult. If you have such sensitivity, be sure to tell your eye doctor about it before the procedure. You can also talk to your doctor about any questions or concerns you have about the side effects of the eye drops.
How do you get the results?
After the ophthalmologist completes the retinoscopy, he or she will calculate your (or your loved one's if the test is being done) prescription for your glasses, or vision prescription. This prescription is exactly the same as the prescription you get from the subjective refraction exam. Your doctor will explain everything about this prescription and what it will do for you.
What if the results did not show normal (20/20) vision?
If the results show that you or your loved one does not have normal ``(20/20 vision)``, don't worry. Your eye specialist will talk to you about ways to correct your vision.
This is often used for:
- Eyeglasses
- Contact lenses
However, some people are able to undergo vision correction surgery such as `LASIK` upon medical advice.
In summary (Take-Home Message)
A good prescription is like a suit that is made to measure and fits you perfectly. An ophthalmologist who uses retinoscopy is like a skilled tailor, hand-sewing every stitch to create that perfect fit.
Although this technique, called retinoscopy, is over 150 years old, it is still a very common procedure used in routine eye exams. So, whether it is for you or a loved one, you can be sure that your eye care professional will use retinoscopy to provide you with the best prescription for your needs.
So there is nothing to be afraid of or suspicious about this. This is a very important test for the health of your eyes.
So the next time you go for an eye exam and ask about retinoscopy, you now know how important and useful it is!
` Retinoscopy, eye examination, vision, refractive errors, ophthalmologist, retina, eyeglasses
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