The changes of the media are generally due to some disease of the media themselves or changes of the density of the media, in such conditions are early cataract, etc.; these types of case are called Index type myopia. It is a common experience that in early cataract due to increased density of the lens a previously normal person become myopic, a myopia more myopic and a hypermetropic less hypermetropic.
These anomalies appear as convergence in – sufficiency, Divergence – in – sufficiency and Hyperphoria. Symptoms commonly noticed besides pain in the eyes, conjunctival irritation, headache – specially located in supra – orbital, orbital, temporal, and occipital regions. Spasms of the facial muscles are also noticed in some cases. A distinguishing feature of the asthenopic muscularis is that they disappear if one eye is closed.
The sensory nerve supply of the eye is from ophthalmic division of the trigeminal nerve, whose branches besides the eye, also supply the teeth of both upper and lower jaw by its maxillary and mandibular division. It also supplies branches to the supraorbital region, face and nose. Thus any trouble involving any one of these branches reflexly causes irritation and as a consequence watering of the eyes.