The other day a friend of mine came in for an eye exam. The exam went smooth, a new prescription for glasses was issued but when we dispensed them to her a few days later, things just seemed off. Although things looked clear, her eyes felt strained, something wasn’t quite right. We checked the prescription of the lenses using our lensometer and found they were correctly made. I took her back into the exam room to double check the prescription and found this time during testing, I was getting inconsistent results. The patient could see 20/20 through a wide range of prescriptions. She was far-sighted and had an incredible ability to accommodate, or auto-focus, her eyes through many different lens powers. But if the eyes over-accommodate during the eye exam, it can lead to a false, inaccurate prescription for glasses.
When this happens, I have to stop the eyes’ ability to auto-focus or accommodate in order to determine a person’s true prescription for glasses. To do this, I use a cycloplegic eye drop. The drop temporarily paralyzes the ciliary muscle inside the eye, this muscle is attached to the crystalline lens of the eye and it contracts or relaxes to make the lens change its shape. When the lens can no longer change its shape, there is no opportunity for the person to auto-focus and what you are left with is the best measurement of a person’s refractive error, in other words, their true, most accurate, glasses prescription.
A cycloplegic refraction is often performed on children, people who have an great ability to vary their accommodation and also for people that are undergoing laser eye surgery in the near future. In these patients, it is important to obtain an accurate prescription for glasses without the eye’s auto-focus interfering with the results or masking the person’s true prescription.
Using cycloplegic drops during an exam does have temporary side effects on the patient. Besides taking away their accommodation and therefore leaving things blurry for a few hours, it dilates the pupil, making you more sensitive to light. They also may make the eyes redden, tear, and may cause an increase in eye pressure in patients who have narrow angle glaucoma. There are different types of cycloplegic drops, some are stronger and their effects last longer. Your eye doctor will determine if there is a need for you to have a cycloplegic refraction, it is not something that is routinely performed on every patient during the eye exam but when indicated, it certainly helps your eye doctor determine the clearest and most comfortable prescription for you!
Whenever you pick up your glasses, if you feel something is just ‘not quite right,’ tell your eye doctor. They are there to help you see clearly and comfortably and will do what it takes to make sure that you are happy with your new glasses. Feel free to ask questions, your vision is not only important to you, it is important to us too!