Evaluating How Well Different Types of Light-sensitive Cells in the Eye Contribute to Its Focusing Ability

A Randomized, Repeated-measures Study to Evaluate the Contributions of Different Cone Photoreceptor Classes to a Step Ocular Accommodation Task

In this experiment, subjects will view shapes on a screen with varying colors and be asked to focus their eyes on the shapes. The shapes will look as though they are jumping to random distances away from the eye. As the subjects focus their eyes on the shapes, the investigators will measure the focus of their eyes using a device called a wavefront sensor. This device uses infrared light to measure the optical properties of the eye in real time. Our goal is to find out how well the eye focuses on different colors. Our broad goal is to better understand how the eye focuses because that process is a major part of having clear and good vision.

In this experiment, subjects will view Gabor patterns on a display through a Badal relay. The Gabor patterns will vary in their color. The colors will be picked to selectively modulate cone photoreceptor activity in different directions in cone contrast space. Subjects will be instructed to accommodate to the patterns while the virtual distance of the screen is manipulated with a focus-adjustable lens. As they do so, the investigators will measure the wavefronts of their eyes using a Shack-Hartmann wavefront sensor.

Inclusion Criteria:

• Between 18-35 years of age
• Normal or corrected-to-normal (glasses/contact lenses) vision.

Exclusion Criteria:

• Vision worse than 20/20 while wearing glasses / contact lenses.
• Fragile or loose teeth (participants need to bite a piece of dental clay to stabilize their heads so that measurements can be taken from their eyes)
• Current pregnancy (experiment requires sitting down without moving for stretches of time)
• Heart disease
• Personal/familial history of epilepsy