While the focus of McConkey Eye Care is ocular disease, and I do not advertise that I see children, I have a lot of parents ask me to see their kids when they are having issues with their vision, and I feel it is very important to address something incredibly important: dilation in children.
Dilation of an adult patient is aimed to open the pupil so that we can get a view of the inside of the eye. The inside of the eye houses the optic nerve, blood vessels, and retina, which can clue us in to many conditions of the body including anemia, leukemia, cancer, diabetes, high blood pressure, high cholesterol, blocked carotids, heart disease, brain tumors, increased brain pressure, multiple sclerosis, HIV, syphilis, Lyme disease... need I list more? We are obviously also looking for conditions of the eyes including retinopathy, macular degeneration, glaucoma, retinal tears or detachments, and more. Please, please, never defer dilation or photos when offered by your eye doctor. It is incredibly important.
Have you ever been dilated, and noticed that you can no longer focus up close like you could before dilation? One of the side effects of dilation, is relaxing the natural focusing system in the eye, called the lens. When we are born, the lens has a significant amount of magnification power, which weakens in our early 40s, causing most people to reach for reading glasses or bifocals (or live in denial and just hold things really far away.) This focusing system is intended to help us focus up close (reading distance). It is very strong in children, and can cause an inaccurate glasses prescription if the prescription is not done while the lens is relaxed, and the patient is dilated.
When we are born, we are put into one of three buckets: near sighted, far sighted, and genetically perfect unicorns. In order to see clearly, light enters the eye, hits the front surface (cornea) and begins to focus to a point. The pupil acts like a camera aperture to change the amount of light that is allowed to enter the eye. It then passes through the focusing system (lens) and focuses on the retina, where it sends the signal back through the optic nerve, the cable that connects the eye to the brain, and it is processed in the visual cortex. In order to have a CLEAR image, the light that enters the eye must focus as ONE POINT on the retina. If light focuses in front of or behind the retina, the image sent to the brain will be blurry. (Side note, astigmatism is when light focuses as TWO points, we can discuss that later).
Near sighted individuals have long eyeballs (or steep corneas), and light focuses too far in front of the retina. They need glasses that MINIFY and move the light back to the retina. Without glasses, near sighted people can see up close, but not far away, and there is nothing their eyes can do about it, as we do not have a minifying system, and they will get glasses at a young age. Near sighted children complain about not being able to see far away, as it tends to worsen over time and they notice a change in their vision.
Far sighted individuals have short eyeballs (or flat corneas), and light focuses too far behind the retina. They need glasses that MAGNIFY and move light forward to the retina. Without glasses, far sighted people under the age of 40(ish) can use their natural focusing system to act like glasses, so they tend to see very well when they are young, and very poorly when they are older. I personally feel for far sighted people, as they have excellent vision, and then 40 hits like a brick wall and they cannot see up close clearly, and slowly their distance may become blurry as well.
Now what does this have to do with dilating kids? If a child is far sighted, they are going to use their natural focusing system to act like glasses. They generally do not complain about their vision, as it isn't always blurry, or they have at least one eye that focuses well. If it is blurry, they do not know to tell you, because they were born that way and don't know what clear vision is supposed to look like. When they arrive at the eye doctor, the first test performed has them focus up close, and children will tend to over focus, adding even more magnification. When the estimate of their prescription is read by the machine, it will show that they are near sighted, as it will think they need a minifying prescription to counteract the magnification the child's eyes are showing. When a doctor puts the minifying prescription in front of the child, they will continue to over focus, leading the doctor to believe the child is near sighted. If a far-sighted child is prescribed near sighted glasses, they will focus through, however, it can cause serious discomfort, headaches, and other problems.
By dilating a child, we can relax the focusing system and determine the TRUE prescription. This is both true for near and far sighted children, as near sighted children can also over focus causing them to get a stronger prescription than they need.
THE ONLY ACCURATE WAY TO DETERMINE A CHILD'S GLASSES PRESCRIPTION IS AFTER DILATION. Additional factors include the prescription being different between the eyes, and the focusing system will only focus until one eye is clear, leaving the other eye blurry. Without a clear image, the eye will never make the proper connections with the brain, and the eye will be left amblyopic (lazy eye). If a child over focuses enough, the eye believes it is reading, and the eyes will turn inward.
This topic can't fully be covered in one blog post, (we barely touched astigmatism) however, I hope this encourages all parents to elect for dilation on their child's eye exam, no matter how inconvenient it may seem, or how much your child resists eye drops. With proper explanation, most children understand why it is necessary.
Please allow your optometrist to dilate your children.
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