Inclusion Criteria:  A person is eligible for inclusion in the study if he/she:  Is between the ages of 18 and 60. Has normal corneas i.e. no corneal infections, no systemic pink eye, no clinically significant dry eye, and no corneal dystrophies. Has refractive errors less than +/- 10.0 Diopters in both eyes.  Exclusion Criteria:  A person will be excluded from the study if he/she:  Adults between the ages of 18-60 who are unable to give informed consent Individuals below 18 years old Individuals above the age of 60 Pregnant women (self-reporting, hormonal changes may alter the refractive status of the eye) Prisoners Students for whom you have direct access to/influence on grades People who do not understand or speak English Has clinically significant dry eye. Has clinically significant cataract. Has spherical refractive error that exceeds the limits outlined above. Is unable to hold his or her head steady for the duration of study measurements.