0 In an emmetropic eye, images of objects 6 meters or more away are focused on the retina with the effect of the eye's refractive environments.
0 As objects come closer than 6 meters, their images begin to fall behind the retina.
0 With the adaptation mechanism, the refractive power of the lens is increased and the image is brought back onto the retina.
0 In harmony, the corpus ciliary contracts. The Zinn fibers holding the lens relax, the lens becomes spherical and the refractive power increases.
0 Accommodation is actually a triad:
1. Increasing the refraction of the lens by contraction of the corpus ciliary
2. Convergence: When objects come close, the eyes shift inward for the continuity of binocular vision.
3. Miosis
Adjustment Disorders
Presbyopia:
It is the decrease in the elasticity of the lens fibers with age, that is, the deterioration of the cohesion power.
It usually occurs after the age of 40 and is physiological.
It occurs EARLY in hypermetropes and LATE in myopia.
+D (convex) glasses are used in its treatment.
Accomodation paralysis:
Paralysis of the oculomotor nerve (III. nerve) results in paralysis of the ciliary muscle and iris sphincter muscle.
Mydriasis is seen, they cannot see far.
It is seen in the use of cycloplegic eye drops (atropine, cyclomid, etc.), in cases such as atropine poisoning.
Spasm of Accomodation:
It occurs as a result of continuous contraction of the ciliary muscle.
It is common in schoolchildren for psychic reasons.
The patients are myopic, miosis is seen.
It is also seen in cases such as parasympathomimetic drug use (pilocarpine), iridocyclitis, hysteria crises.
Treatment: 1% atropine drops are used in hysteria. In others, the cause is eliminated.
