Because myopia is a refractive error, the physical cause of myopia is comparable to any optical system that is out of focus. Borish and Duke-Elder classified myopia by these physical causes: *Axial myopia is attributed to an increase in the eye's axial length *Refractive myopia is attributed to the condition of the refractive elements of the eye. Borish further subclassified refractive myopia: *Curvature myopia is attributed to excessive, or increased, curvature of one or more of the refractive surfaces of the eye, especially the cornea. In those with Cohen syndrome, myopia appears to result from high corneal and lenticular power. *Index myopia is attributed to variation in the index of refraction of one or more of the ocular media. As with any optical system experiencing a defocus aberration, the effect can be exaggerated or masked by changing the aperture size. In the case of the eye, a large pupil emphasizes refractive error and a small pupil masks it. This phenomenon can cause a condition in which an individual has a greater difficulty seeing in low-illumination areas, even though there are no symptoms in bright light, such as daylight. Under rare conditions, edema of the ciliary body can cause an anterior displacement of the lens, inducing a myopia shift in refractive error.
symptom of Keratoconus
symptoms of Keratoconus
symptom of Dermatitis
symptom of Skin cancer
symptom of Vertigo
symptom of Meesmann corneal dystrophy
symptom of Angular cheilitis
symptom of Psoriasis