Why does my ophthalmologist insist that I occasionally need to have my pupils dilated, what is it good for?

Anyone who has undergone a comprehensive eye examination most likely remembers the discomfort associated with dilation of the pupils. Pupil dilations is achieved by placing 1-2 types of eye drops that slowly slowly begin dilating the pupils, which are the central round black portion of the eye, which is actually a hole in the iris. This discomfort of having one’s pupils dilated includes a waiting time of at least 20-30 minutes during the course of the eye examination. This is the amount of time that is necessary for the pupils to dilate sufficiently.

Please note that this wait period is also a “significant bother” to the ophthalmologist because the continuity of the exam is broken, and the patient needs to enter and exit the doctor’s office twice, instead of once. However, the main discomfort is of course patient-centered, since pupil dilation lasts for an extended period of time, usually a few hours (between two to four or more hours after the exam is finished), which is the time it takes until lasts until the pupils return to their original size.

During this time period, vision is blurry (particularly for reading) and there is also generally a great discomfort when exposed to bright lights. If so, why does the doctor insist on dilating the pupils? The answer is that dilating the pupils allows the doctor to examine the inner part of the eye, often referred to as the ‘back of the eye’, including the lens, retina, and optic nerve. These parts of the eye are found behind the iris (the part of the eye which gives the eye its color), and only after dilating the pupils can the ophthalmologist comfortably and thoroughly examine these inner components of the eye. In my clinic, it is my practice to dilate pupils during the initial examination of a new patient, when necessary. In subsequent examinations it is usually not necessary to dilate the pupils at each follow-up visit, but rather only once in a number of visits, when the clinical findings indicate a need for a dilated examination.

Click here to learn: Which tests are performed before cataract surgery.

Click here to learn: What tests will your eye doctor perform to diagnose glaucoma.


Normal pupil- prior to dilation
Normal sized pupil
mid-dilated pupil in a green-brown eye
Pupil starting to dilate
Mid-dilated pupil
Half Dilated Pupil
Widely dilated pupil
A Very Dilated Pupil



Glaucoma & Cataract:



This website was written by Prof. Eytan Blumenthal, to better understand glaucoma & cataract. This information should not replace medical consultation.

Related Posts

Early cataract seen as yellowing of the lens
I've been told that I have mild cataract, what should I do?
It is quite common that during a routine eye exam performed by an ophthalmologist, a patient over the age of 60 is notified that they have mild cataract, which does not justify surgery, but does explain...
Prof. Blumenthal examining a patient
Tests Performed to Diagnose Glaucoma
How will my eye doctor decide if I actually have glaucoma, or maybe not? Glaucoma, in the vast majority of cases goes unnoticed, and hence, undiagnosed. Those suffering from this disease typically do not...
A tonometer used to measure eye pressure (intraocular pressure)
Intra-Ocular Pressure: What, Why and How
What is Intraocular pressure? Why is it so important in diagnosing and following glaucoma patients?  How do we accurately measure it in the clinic? Intra-ocular pressure is the most important parameter...
The button which is pressed while performing a visual field test
What is a Visual Field Test
A visual field test is preformed by a specially trained technician. The results of each individual eye are registered in print and the patient is requested to give the test results to the ophthalmologist...
What is a Cataract
Within each healthy eye is a lens that we are born with. This lens, which is crystal clear, is important in focusing the light onto the retina, and enabling us clear vision. The definition of the word...