Optical and Non-Optical Equipment Flashcards
Optical Devices
devices or aids uses lenses or prisms to correct for an optical defect and are employed to magnify, reduce or otherwise change the shape or location of an image on the retina
Non-Optical Devices
Devices or aids that may be used to enhance visual functioning, especially by providing illumination or improving contrast
Refractive Error
Corneal irregularities in which parallel rays of light are not brought to focus on the retina because of a defect in the shape of the eye or the refractive media of the eye
Convex Lens
Lens that bulges outward.
Thicker at the center
Useful for correcting hyperopia
Concave lens
Lens that bulges inward and used to diverge light rays
Thinner middle
Useful for correcting myopia
Prism Lens
Often used with persons with strabismus or slightly reduced visual acuity who tend to neglect or are unaware of a field loss
Used to cue the person that additional information exists (remaining words on a line of text or objects in periphery)
Fresnel Prism
User can carry in their hand. Often used to decrease lens thickness and increase the field of view
Can be used as a treatment for double vision
Diopters
Power of a lens
Calculated by D=100cm/ focal distance of lens (in cm)
Shorter focal distance = greater dioptric power
Relative Distance Magnification
Occurs when an object is brought closer to the eyes
Relative Size Magnification
When the size of an object is increased and this larger object is viewed at a smaller distance to the original object
Angular Magnification
Makes objects at a distance appear closer to the eyes
Optical devices are common examples of using angular magnification
Projection Magnification
When an image is projected and the size is increased
