Our study has three parts has three parts, and the main aim of the study is to find out if corneal hysteresis was associated with myopia or even a predictor of myopia poor control predictor:

• Part 1 of our study: patients with anisomeropia whose spherical equivalent refraction as measured by cycloplegic autorefraction between the two eyes differ greater than 1.5 D.
• Part 2 of our study: Minus spherical equivalent refraction as measured by cycloplegic autorefraction.
• Part 3 of our study: patients with minus spherical equivalent refraction as measured by cycloplegic autorefraction who are under regular atropine for the treatment of myopia;patients who are prescribed with atropine treatment are in need of myopia control instead of for research interest

Inclusion Criteria:

1. Normal ocular health other than myopia or anisometropia
2. In good general health with no history of prematurity or cardiac or significant respiratory diseases
3. No allergy to atropine, tropicamide, proparacaine, and benzalkonium chloride
4. No previous or current use of contact lenses, bifocals, progressive addition lenses
5. No amblyopia or manifest strabismus, including intermittent tropia

Exclusion Criteria:

1. presence of keratoconus or other corneal disease
2. previous eye drops usage except Atropine
3. major ocular surgery history (including refractive surgery, scleral buckle, glaucoma filtering, cornea transplant, cataract and vitreoretinal surgery)
4. presence of other ocular conditions such as glaucoma, uveitis, or other ocular inflammatory or vitreoretinal diseases.

age under 25 year old with or without myopia