17 terms

refractive errors

refractive errors
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near sightedness. eye ball too large. point of focus of light rays is in front of the retina
myopia
far sightedness. eyeball too small. point of focus of light rays is behind the retina.
hyperopia
regular and irregular.
regular caused by bulge in cornea.
irregular caused by bumpy cornea-cant correct
astigmatism
lens hardens with age. lens cannot change shape to focus light rays on retina. found in individuals older than 40
presbyopia
the process of the lens of the eye changing shape to focus light rays on the retina. ciliary muscle relaxes causing suspensory ligaments to tighten streching the lens and making it thinner resulting in less focusing. ciliary muscle contracts, lessening tautness of the suspensory ligaments causing the lens to become thicker resulting in more focusing power
accomodation
the process of the 2 eyes coming together to view objects at a close distance, the closer the object, the more conergence is needed.
convergence and accomodation work together. the closer the object of regard, the more the eye must accommodate and the more the eyes must converage.
convergance
light rays emanating from objects 20 feet away or further reach the eye in
parallel form
light rays emanating from objects closer than 20 feet reach the eye as they
spread apart
the closer the object
the more spreading apart they are
refract light rays
prisms
triangular shaped glass, light rays passing through the prism bend toward the base or thicker part
prism
comprised of 2 prisms which are put together base to base. bend light rays together
convex lenses
comprised of 2 prisms put together at their points. spread light rays apart
concave
a measure of the power of a prism or lens to bend light rays
diopeter
convex lenses correct
hyperopia
the point of focus is behind the retina. bring the light rays together sufficiently to bring the point of focus on the retina
hyperopia
cylindrical lenses corrects
regular astigmatism