Error of RefractionTan, Michelle Lorraine B.

DBE

Refraction

The bending of light rays at the junction of two transparent substances with different densities

Accommodation

Increase in the curvature of the lens for near vision

Near Point Vision

The minimum distance from the eye that an object can be clearly focused with maximum accommodation.

Distance is about 10cm(4in.) in a young adult.

Presbyopia

Presby-= old; -opia= eye/vision

Lens loses elasticity and its ability to accommodate

Mid-forties

Bye age 40: near point vision=20cm(8in.)

60 to 80 y/o: near point vision=60 to 80cm(31in)

Refraction Abnormalities

Emmetropic eye

Normal eye

Refract light rays from an object 6m(20ft.) away

Myopia

Nearsightedness

Eyeball is too long relative to the focusing power of the cornea and lens

Hypermetropia/ hyperopia

Farsightedness

Eyeball is short relative to the focusing power of the cornea and lens

Astigmatism

Either the cornea or the lens has irregular curvature

Parts of the image are out of focus—the vision is blurred or distorted

Correction

Eyeglasses

Contact lenses

Laser surgery

Thank you!