Abnormal, harmful, or undesirable effect on an organism that causes anatomical or functional damage, irreversible physical changes, or increases the susceptibility to other biological, chemical, or environmental stresses.
Optometrists can prescribe glasses, contact lenses, eye exercises, vision aids and therapy, and (in some states) oral and topical medications to treat certain eye diseases. Ophthalmologists are doctors of the eye. They have graduated from medical school and are licensed to practice medicine, so their credentials are either doctor of medicine (MD) or doctor of osteopathy (DO).
Refraction assessment. To determine your prescription for glasses, your doctor does a refraction assessment. He or she asks you to look through a mask-like device that contains wheels with different lenses of different strengths (phoropter) to help judge which combination gives you the sharpest vision.efraction assessment. To determine your prescription for glasses, your doctor does a refraction assessment. He or she asks you to look through a mask-like device that contains wheels with different lenses of different strengths (phoropter) to help judge which combination gives you the sharpest vision.