Repeatability of central and peripheral eye length and choroidal thickness measurements in healthy subjects.

The length of the eye and the thickness of a layer inside the eye called the choroid can change over time and are important measurements in optometric research — particularly in understanding why some people become more short-sighted over their lives. Two instruments, the Lenstar LS 900 and the Triton Swept-source OCT, are used by eye researchers to take these measurements, but how consistent and repeatable their readings are has not been fully established. This study will simply take eye measurements using both instruments on two separate days (at least one day apart) and compare the results to determine how reliable the readings are. This is important so researchers know how much change in a measurement represents a true biological change versus just measurement variation. To be eligible you need to be 18 or older with normal eye health and either normal vision or a refractive error (short-sightedness, long-sightedness, or astigmatism). People with health conditions like diabetes, hypertension, or heart disease, or who have had eye surgery or used orthokeratology lenses, are not eligible. The study involves only non-invasive eye scans — no drops, medications, or procedures.