Clinical Refraction Flashcards
what is the definition of
Emmetropia
the refractive state in a healthy eye in which, any individual achieves the perfect visual function, when the accomodation is at rest
How does the emmetropic eye achieve a perfect image?
- antero posterior length = 24mm
- diameter of cornea 12mm
- curvature of the cornea is 7.8 mm
- Dioptric power
- the media are clear
- the vision is 6/6
- kappa = +5
definition of
Ametropias
light rays do not focus correctly on the retina when the eye is relaxed.
types of
Ametropias
- myopia
- hypermetropia
- astigmatism
definition of
Anisometropia
a difference in the refraction between both eyes.
Untreated high anisometropia in children can results
- amblyopia
- strabismus
A ____ change in axial length resulting in 1.00 D of
anisometropia
0.33mm
the commonest cause of ametropia
Changes in the axial length
the medical term of
short sight
myopia
classification of myopia
- congenital
- pathological
- simple
key features of each class
classification of myopia
- simple = good prognosis
- congenital = with anomalies + poor
- pathological = progressive
which type of lens is used in myopia or hypermetropi?
myopia = concave
hypermetropia = convex
surgeries for myopia
- Corneal Ablation By Excimer Laser
- Phakic IOL
causes of hypermetropia
- axial
- curveture
- index
- aphakia
- posterior deslocation of the lens
How do the axis and curvature relate to hypermetropia and myopia?
high axis = high myopic
high diameter of curveture = hypermetropia
high diameter of curveture = flat cornea !!!
