Why do they ask which lens looks clearer?

Hi, I'm Dr. Vale. I'm an optometrist.

Why do they ask which lens looks clearer?

A refraction test finds the lens that focuses light most clearly on your retina, the light-sensing part at the back of your eye. The test finds which lens strength bends light to focus it more clearly on your retina. An eye care specialist uses this information to decide if you need corrective lenses.

One common method is subjective refraction, where you look at an eye chart through a series of different lenses. You sit behind a machine called a phoropter while someone on the team changes the lenses in front of your eyes. They ask questions such as, "Which one is clearer, one or two?" Answering that both choices look the same is also a valid response.

Other methods are available for people who cannot easily answer comparison questions, including young children. An autorefractor is a machine that measures how light focuses inside your eye, and it works best if you can hold still and look at a target. In retinoscopy, the clinician shines a light into your eye and watches the reflection. They change lenses to see how the reflection changes, without asking you to choose.

For some exams, eye drops are used to dilate, or widen, your pupils and relax the eye's focusing muscles. This can lead to a more accurate measurement, especially for children. The drops may cause blurry vision and sensitivity to light. Because of this, driving can be difficult until the effects of the drops wear off.

People often ask what the results mean for their vision. They also ask about the different types of corrective lenses that might be an option if needed.

Call the office if you have questions about your visit or your care. This is general information, not personal instructions. Your own care team can tell you what applies to you.

Thanks for watching.