Eye dilation is a common procedure performed during eye examinations, where special eye drops are used to enlarge the pupils. This widening of the pupil provides eye care professionals with a clearer and more comprehensive view of the eye’s internal structures, particularly the retina and optic nerve at the back of the eye. A frequent and expected side effect of this process is temporary blurry vision, which can affect both near and, to a lesser extent, distance vision.
How Your Eye Normally Focuses
The human eye focuses light to create clear images. A key component of this system is the pupil, the dark opening in the center of the iris, which is the colored part of the eye. The pupil’s primary role is to regulate the amount of light entering the eye, becoming smaller in bright conditions and larger in dim light. Another important structure is the eye’s natural lens, located behind the iris. This lens changes its shape to adjust focus, allowing you to see objects clearly at various distances, a process known as accommodation.
When Pupils Open Wide
During eye dilation, eye drops containing medications called mydriatics are administered. These drops work by stimulating the muscles that widen the pupil and inhibiting the muscles that constrict it, causing the pupil to become larger. A wider pupil allows more light to enter the eye than usual, which can lead to increased light sensitivity, also known as photophobia. This influx of light, combined with the enlarged pupil, reduces the eye’s depth of field, meaning fewer objects at different distances appear in sharp focus simultaneously. The increased light can also scatter within the eye, contributing to blurriness.
Why Your Eye Can’t Adjust Focus
Beyond simply widening the pupil, dilating drops often include another type of medication called cycloplegics. These cycloplegic agents temporarily paralyze the ciliary muscle, a ring of smooth muscle located behind the iris. The ciliary muscle is responsible for changing the shape of the eye’s natural lens, which is essential for focusing on objects at different distances. When this muscle is temporarily unable to function, the lens cannot alter its curvature to properly focus light, particularly for close-up objects. This temporary paralysis of accommodation makes near-vision tasks like reading or using a phone challenging, as the eye loses its ability to focus on close objects.
What to Expect After Dilation
The effects of eye dilation are temporary, with blurry vision and light sensitivity typically lasting 4 to 6 hours. Duration varies based on drop type, strength, and individual factors like eye color, with lighter eyes sometimes experiencing longer effects. In some cases, particularly for children or with certain drops, the effects may persist for up to 24 hours. To manage increased light sensitivity, wearing sunglasses after your appointment is recommended. Avoid driving or tasks requiring clear vision until your eyesight returns to normal.