Dilating drops: why they are needed and how to prepare your child

The part of a child's eye exam that draws the most questions is the drops. Parents are right to ask: why are they needed, are they harmful, how long do they last?

This article covers what the drops do, why they should not be skipped, and how to plan the day of the exam.

The lens of the eye changes shape to sharpen near objects, a process called accommodation. In children that power is far stronger than in adults.

At an exam this strength is an obstacle rather than an advantage: a child can partly compensate for an existing prescription by pushing hard, so the measurement comes out lower than it truly is.

Long sight and a difference in prescription between the eyes are exactly the sort of findings that can be masked this way, and that difference is the most common cause of amblyopia.

The drops temporarily relax the focusing muscle. The child can no longer compensate, and the true refractive error becomes measurable.

The same drops also widen the pupil, letting the doctor assess the inside of the eye more easily. One step yields two pieces of information.

This is why a child's glasses prescription is not based on a measurement taken without drops.

The drops can sting for a few seconds as they go in, and that passes. Afterwards, near vision is blurry for some hours and light can be uncomfortable.

Depending on the type used, the effect can last from a few hours to a day; your doctor will tell you the expected window. During it, reading and close work are harder for the child.

These are expected, temporary effects and they leave no lasting harm.

Book the appointment for an afternoon or a weekend rather than a homework-heavy school day, and avoid scheduling close work right afterwards.

Bring sunglasses or a hat; they noticeably reduce the light sensitivity on the way out.

Describe the process to your child honestly beforehand: they will put a drop in your eye, it stings a little and then it passes, and things close up will look blurry for a while. A child who knows what to expect is far more relaxed.