Effect of multifocal spectacle lenses on eye length and other ocular parameters in human.

INTERVENTION: This will be a prospective, randomized, non‐dispensing, short term wear (60 minutes) clinical trial. 20 healthy young adults with low to moderate myopia (‐0.75D to ‐5.0D) will be enrolled. Participants will be asked to wear a 5 different types of multifocal spectacle lenses and one single vision spectacle lens over 6 days with a minimum of 24 hour of washout period between each lens wear. They will be asked to wear a spectacle frame fitted with a plano powered spectacle lens in one of the two eye frames and one of the randomly assigned multifocal spectacle lens in the other eye frame for 60 mins. Measurements of refractive error, axial length, choroidal thickness and contrast sensitivity will be measured before and after lens wear. Lens descriptions: Lens 1 is a single vision spectacle lens (control) Lens 2 is a commercially available multifocal ophthalmic spectacle lens (control). Lens 3 to 6 are prototype spectacle lenses, comprise of central zone for refractive error correction and a peripheral zone area comprising a refractive power that varies from central zone up to +/‐ 5.0D. Prototypes 3 and 4 will have central zone diameter of up to 9 mm whereas prototypes 5 and 6 will have central zone diameter of up to 5 mm. This study will be conducted at Brien Holden Vision Institute Clinic and will be conducted and managed by student researcher with supervision by BHVI employed registered research optometrist and the study investigators. Student researcher is an optometrist by background with experience in study procedures including fitting of contact lenses and spectacles. He has also completed Good Clinical Practice training. Brien Holden Vision Institute has clinical facilities to conduct the study and access to relevant study population. < CONDITION: Eye ‐ Diseases / disorders of the eye Myopia; ; Myopia PRIMARY OUTCOME: Changes in axial length of the eye will be assessed using an ocular biometer (LENSTAR LS900®, HAAG‐STREIT, Switzerland). Participant will be seated with their chin resting on chin rest and forehead against a headrest. The participant will look into the red fixation target. No part of the instrument touches the eye during the procedure. [changes will be assessed after 60 minutes of lens wear for each prototype lens and a control lens. ] Changes in choroidal thickness will be assessed with a standard, commercially available Optical Coherence Tomography (DRI OCT™, TOPCON CORPORATION, Tokyo Japan) instrument. The participant will be seated for approximately 3 minutes with their chin in a chin‐rest and forehead against a head‐rest. The participant will look into the camera which will emit a fixation light. No part of the instrument touches the eye during the procedure. [changes will be assessed after 60 minutes of lens wear for each prototype lens and a control lens. ] INCLUSION CRITERIA: • Non‐cycloplegic spherical equivalent refractive error ranging from ‐0.75D to –5.00D • Best corrected visual acuity of 20/30 or better in both eyes • Normal ocular health (No ocular disease) • No history of ocular surgery; • No manifest squint or intermittent tropias; • Astigmatism less than 1.50 D; • Anisometropia of not more than 1.00 D; • Absence of any ocular disease that might influence the trial outcomes‐ for example corneal or retinal disease, cataract and ptosis. • Normal general health. • No current use of ocular or systemic medications excepting use of lubricating or anti‐allergic eye drops SECONDARY OUTCOME: Changes in central and peripheral refractive error of the eye will be assessed together using a commercially available autorefractor (MVISION‐K 5001, SHIN NIPPON, JAPAN) to determine refractive error. Participant will be seated with their chin resting on chin rest and forehead against a headrest. It momentarily projects an infrared target on the retina that is imaged and digitally analyzed to calculate the refractive error. No part of the instrument contacts the eye. [changes will be assessed after 60 minutes of lens wear for each prototype lens and a control lens. ] Changes in contrast sensitivity function will be measured using targets projected on a screen using custom MATLAB code.[changes will be assessed after 60 minutes of lens wear for each prototype lens and a control lens. ]