Overview of the dilated pupillary exam
A dilated pupillary exam is done to deliberately increase the size of the pupils during an eye exam so that the ophthalmologist can fully examine the health of the optic nerve and retina. The exam is essential to prevent and treat eye conditions that could potentially lead to vision loss. Pupil dilation occurs when the opening in the centre of your iris widens to let in more light.
Both dilated and non-dilated eye exams provide essential information to the doctor. Let’s explore the undilated exam first.
The undilated eye exam
One of the first parts of a comprehensive eye exam is a test of your vision, and perhaps a measurement to determine an eyeglass prescription, both of which require that your eyes remain undilated.
Also, ophthalmologists will examine your pupils’ responses to light, before dilation. This can be important in determining whether the visual pathways in each eye are working properly.
There is also an examination, called gonioscopy, which allows the doctor to examine your eye’s drainage angle with a special mirrored lens. The “angle” that is being referred to is the angle between the iris, which makes up the coloured part of your eye, and the cornea, which is the clear window front part of your eye. When the angle is open, your ophthalmologist can see most, if not all, of your eye’s drainage system. When the angle is narrow, only portions of the drainage angle are visible, and in acute angle-closure glaucoma, none of it is visible.
Part of a glaucoma exam is a formal visual field test, where your peripheral or side vision is assessed. Ideally, your eyes do not dilate during this test. Finally, there are other parts of the front of the eye, for example, the iris, that must be examined when the eyes are not dilated.
The dilated eye exam
The view of the back of the eye is limited when the pupil is not dilated. When your pupil is small, an eye doctor can see your optic nerve and macula, but the vision is limited. To see the whole retina, the pupil must be opened. This is accomplished through the use of eye drops.
How long does it take for the eyes to fully dilate
After the drops are given, it takes 15 to 30 minutes for the pupils to fully dilate, depending on the person’s response to the medicine.
What conditions are diagnosed with a dilated eye exam?
The optic nerve can be seen through a dilated pupil, but a dilated pupil is compulsory for optimal vision. This is significant for the diagnosis of glaucoma, as well as other diseases of the optic nerve.
Two very common retinal diseases, diabetic retinopathy and age-related macular degeneration (AMD), are diagnosed and controlled by examining the retina through a dilated pupil.
In addition to macular degeneration and glaucoma, many other conditions require pupil dilation, such as detection of a retinal tear or detachment, or an ocular tumour, just to name a few.
When it’s done
Once your eyes are dilated, there is an increase in sensitivity to light because the pupil is large and more light is coming in, so bring your sunglasses, or your ophthalmologist can provide you with some disposable shades to wear. You may also experience blurred vision, especially if you are trying to read. Some patients feel a “tightening” or a different sensation in the eyelids.
If this is the first time your eyes have been dilated, or if you know that your vision is too impaired to drive after dilation, bring a friend or partner to drive you home after the exam. While there have been some eye drops in the past that could reverse dilation, these are no longer available, so you will have to wait 4-6 hours before the drops completely wear off.
Procedure for dilated pupillary exam
To dilate the pupil or dilated pupillary exam, the ophthalmologist must place drops in the eyes that take 15 to 30 minutes to work.
The most widely used pupil dilating drops in ophthalmology consultations are tropicamide, phenylephrine, and cyclopentolate. Its effect can last between 4 and 24 hours depending on the type of drop and the sensitivity of each patient. It is a completely painless procedure that can cause a slight stinging that disappears in seconds.
Complications of dilated pupillary exam
A dilated pupillary exam does not usually affect your distance vision. But because your pupils cannot control the amount of light that enters your eyes, the outside glare can bother you. For some people, that makes driving dangerous. If your eyes have never been dilated, have someone else drive you home after your appointment. Whether you are behind the wheel or not, it is a good idea to wear sunglasses to protect your eyes after the exam.
Side effects of dilated pupillary exam
The dilated pupillary exam is harmless in the long term but has short-term side effects. They usually last between four and six hours.
Side effects of dilation include:
- Sensitivity to light
- Blurry vision
- Trouble concentrating on nearby objects.
- Stinging just after putting in the drops.
If you wear contact lenses, you may not be able to wear them until the dilation drops are gone.
Dilated pupillary exam risk factors
The most common side effects of the dilated pupillary exam are sensitivity to light, photophobia, glare, and blurred vision, especially in myopia, which manifests as problems focusing on objects. These effects gradually disappear.