<unk>  occurs when a spasm of the ciliary muscle prevents the eye from focusing in the distance, sometimes intermittently; this is different from myopia which is caused by the eye's shape or other basic anatomy.<unk>  may be either organic, through stimulation of the parasympathetic nervous system, or functional in origin, through eye strain or fatigue of ocular systems. It is common in young adults who have active accommodation, and classically occurs after a change in visual requirements, such as students preparing for an exam, or a change in occupation.
Pseudomyopia
Heterotopia 
Quadrantanopia
Nyctalopia
Presbyopia
Tunnel vision
Cyclopia
Ocular dysmetria