Pupil Dilation: How Long for Accurate Eye Exams?

Q: Pupil Dilation: How Long for Accurate Eye Exams?

Hello Mr. <br>Chen： Pupil dilation is actually intended to prevent the ciliary muscle from contracting. <br>The effects can vary from person to person, and the duration may also differ. <br>Each refractor may have slight variations as well. <br>Based on your vision and prescripti

Pupil Dilation Issues

Hello! I have a question regarding dilation.
My son went to the ophthalmology clinic today for an eye examination.
His original prescription was -3.25 and -3.50 (astigmatism +0.50 and +1.00).
Before dilation, he wore his glasses and his vision was 20/20.
After administering three types of eye drops for dilation, the nurse waited only 15 minutes before checking his vision again, which resulted in -3.50 and -4.00 (astigmatism +0.50 and +1.00).
About an hour and a half later, we went to the optical shop to get glasses, and the staff checked his vision again, resulting in -3.25 and -3.50 (astigmatism +0.50 and +1.25), which matched his original prescription, with just a slight increase in astigmatism.
How long does dilation need to accurately assess vision? How long does the effect of dilation last? Does my son need new glasses based on his situation?

Mr. Chen, 40~49 year old female. Ask Date: 2017/02/25

Dr. Gao Pilin reply Ophthalmology

Hello Mr.
Chen: Pupil dilation is actually intended to prevent the ciliary muscle from contracting.
The effects can vary from person to person, and the duration may also differ.
Each refractor may have slight variations as well.
Based on your vision and prescription, it seems that a new prescription may not be necessary.
The ophthalmology department at E-Hospital in Puzi, Taiwan, is open Monday to Friday from 8:00 AM to 12:00 PM and Wednesday afternoons from 1:00 PM to 4:30 PM.
Please note that online responses should only be used as a reference; it is essential to seek medical attention at a healthcare facility if needed.
I hope to have the opportunity to serve you.
Best regards, Gao Pilin.

Reply Date: 2017/02/25

More Info

Pupil dilation, or mydriasis, is a crucial step in the eye examination process, particularly for assessing refractive errors and the health of the retina and optic nerve. When your son underwent an eye exam, the use of dilating drops was intended to relax the ciliary muscle, allowing for a more accurate measurement of his refractive error. However, the timing and effectiveness of dilation can vary significantly among individuals.

Typically, the effects of dilating drops can take anywhere from 15 minutes to an hour to fully manifest, depending on the type of drops used and the individual's response. In your son's case, it seems that the nurse waited only 15 minutes before conducting the examination, which may not have been sufficient time for the drops to take full effect. This could explain the discrepancies in the measurements obtained during the initial exam and the subsequent check at the eyewear store.

The duration of the dilation effect can also vary. Most dilating drops can keep the pupils dilated for 4 to 6 hours, but some individuals may experience effects lasting longer, especially if they are particularly sensitive to the medication. This prolonged dilation can affect vision, particularly near vision, as the ciliary muscle remains relaxed and unable to accommodate for close objects.

Regarding whether your son needs new glasses, the decision should be based on a few factors. If the measurements taken after dilation indicate a significant change in his prescription, particularly if he is experiencing difficulty seeing clearly at certain distances, it may be advisable to update his glasses. However, if the measurements are similar to his previous prescription, and he is comfortable with his current vision, it may not be necessary to change his lenses.

In summary, for accurate eye exams following dilation, it is generally recommended to wait at least 30 minutes to an hour after administering the drops before conducting refractive measurements. This allows enough time for the medication to take full effect and provides a more accurate assessment of the eye's refractive status. If there are discrepancies in measurements, it may be beneficial to consult with an eye care professional for further evaluation and to determine the best course of action regarding new eyewear. Regular eye exams are essential, especially for children, to ensure their vision is developing properly and to address any potential issues early on.

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