A refractive error that prevents the light rays from coming to a single focus on
the retina because of different degrees of refraction in the various meridians
of the eye.
~ Astigmatism
Condition in which the steepest corneal meridian is in the horizontal plane. 0-30
degrees or 150-180 deg...
Which of the following can aphakia cause, myopia or hypermetropia?
✓~ Hypermetropia
Causes of aphakia
✓~ *Congenital absence of lens
*Surgical Aphakia
*Absorption of lens matter
,*Traumatic extrusion (push or forced out)
*Posterior dislocation- in vitreous, causes optical aphakia
The cornea thins and bulges outward into a cone shape
✓~ Keratoconus
Symptoms of Keratoconus
✓~ *distorted, blurred, double vision
*inability to see dim light
*sensitivity to light
Signs of keratoconus
✓~ CORNEAL THINNING AT THE APEX
CHANGES OF ASTIGMATISM
DECREASING VISION IN ONE EYE
cause of keratoconus
, ✓~ Cause is unknown, but it is believed to be present at birth or the loss of
collagen in the cornea
How can be keratoconus be treated?
✓~ *Surgical treatment
*Vision correction
*specialty contact
*Corneal cross link
Slows down and stop the progression of keratoconus but doesn't improve vision
✓~ Cornea Cross Linking
A conical shaped cornea can best be fit with contact lenses through the use of:
A.trial lenses
B. keratometer readings
C. eye impressions
D. topogometer readings
✓~ A. Trial lenses
, Prism ballast lenses can be useful for:
✓~ For cylindrical lenses and some bifocals
Helping to reduce lens rotation
What type of contacts needs prism ballast?
✓~ Front surface toric GP and bifocal/multifocal GP
What type of contacts does not need prism ballast
✓~ Back surface toric, Bitoric, and Spherical lenses
Base down prism from 0.75-1.5 diopters weighs the lens down and keeps it
stable so it doesn't rotate
✓~ Prism ballast
Bitoric lenses are prescribed:
A. Only when there is a small amount of corneal
B. Astigmatism and no residual when there 1s no corneal
C. Astigmatism only for bifocal contact lenses
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