Under normal circumstances, if you expose your eyes to light, the pupil will constrict to limit how much light goes into your eye. When we need to examine the inside of your eyes, we need to shine a light through that pupil so examine the structures. In order to see this clearly and with stereopsis (depth perception or ‘3D’), we need to make the pupil stay open using eyedrops. Our view before dilation is similar to looking into a room through a keyhole using only one eye. After dilating the pupil the view is like opening the door and putting your head in the room to look around. To adequately evaluate those structures we need to dilate.
The dilation process requires us to instill eyedrops and wait for the pupil to open. The pupil will start to dilate within 5 minutes and peaks at about 20 minutes. Once your pupil is dilated we examine your eyes.
The side effects of the dilation vary based on your age. Under the age of 45 it will blur your near vision (reading) when you are wearing your glasses and will make you sensitive to bright light. Over the age of 45 it will typically only make you sensitive to bright light as your eyeglasses will help to correct the reading. This blurred reading vision lasts for about 90 minutes and the light sensitivity lasts about 4 hours.
We do not recommend that you drive after being dilated due to these complications. Most people do drive, but if you have never driven dilated, we strongly urge that you bring a driver or return to be dilated another day when someone will drive you. Remember to bring sunglasses with you, if you have them.
Most eye care professionals dilate your pupils annually. The health risks for the eye increase with age, so this is absolutely more important as you age.
Some instruments can take images of the retina without dilation. As part of our pretesting we take ‘fundus photographs’. Some current scanning laser instruments are capable of obtaining 2 dimensional images of nearly 80% of the retina. These are wonderful technologies, but do not replace a 3-dimensional evaluation of the retina when performed by the doctor with an indirect ophthalmoscope (but keep your eyes peeled as technology continues to advance and this could change).