Optometry has a long history of using spectacle lenses to correct for refractive errors (spherical and cylindrical). Different patient conditions require the doctor to utilize different clinical decisions when prescribing eyeglasses. These include whether to prescribe cylindrical power to correct astigmatism (warping of vision), prism for double vision or strabismus, progressive addition or bi-/tri-focal lenses for presbyopia to see different distances without blurred vision.
Additional considerations are also given to avoid glare by adding special coatings on the front and back surfaces of the lenses, and to improve image contrast by adding chromatic filters that blocks or attenuate specific wavelengths of light. Strong ultraviolet and blue light can cause cataract and age-related macular degeneration for older patients and should be reduced from a younger age to avoid the cumulative damaging effects of sunlight.
The increase of vision use indoor, including working in front of a computer screen or reading at a near distance, also can causes patients in all ages to experience visual discomfort (eyestrain, dry eye, eye pain, blurred vision, double vision, burning and sandy sensation on eye surface. These are due to the sustained stress on the muscles inside and around the eyes, and the reduction of eye blinks. Doctors usually prescribe progressive addition glasses or office-/learning-related eyeglasses.
