ERRORS OF REFRACTION Flashcards
AMETROPIA
refractive error
Eyeglasses
the safest and simplest way to correct a refractive error
high index lenses
reduce the lens thickness and weight and are useful in correcting high refractive errors and provide comfort and better cosmetic appearance
safety glasses or eye protectors
recommended for those who are involved in certain sports and hazardous activities
shatterproof eyeglasses
they are recommended for those who have good vision in only one eye
polycarbonate plastic
material of choice when ocular protection is the foremost consideration in making glasses as it is more impact resistant than plastic or hardened glass
ambylopia
lazy eye
sulfonamides
is a medication that causes the ciliary processes to swell and also the forward movement of the lens
uncorrected hyperopia
frequently associated with accommodative esotropia
concave lenses
the type of lenses for myopic eyes
convex lenses
the type of lenses for hyperopic eyes
refractive surgeries
range of procedures that is aimed at changing the refraction of the eye by altering the cornea or lens
hypermetropia up to 4D, astigmatism up to 4D and myopia up to 12D
the range that LASIK surgery can correct
250um
the residual bed that should remain after LASIK surgery to avoid ectasia
ectasia
the bulging and thinning of the cornea
lasik
the laser beam would reshape the cornea after opening a flap
photorefractive keratectomy
the epithelial cells are removed with laser, which is the superficial corneal layer to the Bowman’s layer
clear lens exchange
replace the natural lens of the eye with an introcular lens implant
phakic posterior chamber implant
implantable contact lens is implanted behind the iris and in front of the lens
-3D to -20.5D
the range that phakic posterior chamber implant can correct
59 diopters
the total refractive power of the eye
1.40
the refractive power of the lens
1.38
the refractive power of the cornea
myopia
the eyeball is too long
myopia
the image is focused in front of the retina
hyperopia
the eyeball is short
hyperopia
the image is focused at the back of the retina
astigmatism
there is an irregular curvature of the eyeball
presbyopia
there is a loss of accommodation of the lens due to it being hardened
more than -6 diopters
meaning of high myopia in which the axial length is usually greater than 26 mm
pathological or degenerative myopia
progressive anteroposterior elongation of the scleral envelop associated with range of secondary ocular changes
Amblyopia
Is the unilateral, or rarely bilateral, decrease in best
corrected visual acuity (VA) caused by form vision deprivation and/or abnormal binocular interaction, for which there is no identifiable pathology of the eye or visual pathway.
Strabismic amblyopia
results from abnormal binocular interaction where there is continued monocular suppression of the deviating eye.
Anisometropic amblyopia
is caused by a difference in refractive error between the eyes and may result from a difference of as little as 1 dioptre. it is frequently associated with microstrabismus and may co-exist with strabismic amblyopia
Stimulus deprivation amblyopia
Results from vision deprivation. It may be unilateral or bilateral and is typically caused by opacities in the media (e.g. cataract) or ptosis that covers the pupil.
Bilateral ametropic amblyopia
Results from high symmetrical refractive errors, usually hypermetropia.
Meridional amblyopia
Results from image blur in one meridian. It can be unilateral or bilateral and is caused by uncorrected astigmatism (usually >1 D) persisting beyond the period
of emmetropization in early childhood.
crowding phenomenon
The phenomenon where VA in amblyopia is usually better when reading single letters than letters in a row.
A difference in best-corrected VA of two Snellen lines or more (or >1 log unit)
Is indicative of amblyopia.
7–8 years
The sensitive period during which the acuity of an amblyopic eye can be improved is usually up to ___ years in strabismic amblyopia
occlusion of the normal eye
most effective treatment for amblyopia
6 months
how long should occlusion of the normal eye as treatment take
penalization
the vision of the normal eye is blurred with atropine and works best with mild-moderate amblyopia