FAQ: Can the EyeLink systems be used with participants who are wearing contact lens?

[Sam]

Yes, EyeLink systems can be used with participants who wear contact lenses, but the type of lens matters.

• Soft Contact Lenses: Most soft contact lenses, including daily and monthly disposables, have no impact on eye-tracking quality.
  
• Tinted Contact Lenses: Heavily tinted cosmetic lenses are uncommon, but they can sometimes make it difficult for the tracker to get a clear view of the pupil. Standard, lightly tinted prescription lenses are typically not an issue.
  
• Hard Contact Lenses: Hard contact lenses will almost certainly cause problems and should be avoided. Hard lenses are smaller and tend to move around on the eye's surface. This movement means the corneal reflection (the small dot of light the tracker follows) is not stable, and the edge of the lens can obscure the pupil, making it difficult for the tracker to calculate the eye's position accurately. If possible, ask participants who wear hard contact lenses to wear their glasses instead.