Eyesight; good & bad, Issue 350

accommodation effort afford ametropia angle appear Argand burner artificial light asthenopia astigmatism axis become blind burners called candle centre choroid colour colour-blindness concave lenses convergence effort convex lens cornea correction Crown 8vo crystalline lens curvature defect degree dense medium dioptrics of accommodation direction disease distance distant objects divergent emmetropic equal exert eyeball fall fatigue Fcap flame focal length focus four dioptrics frame hence horizontal hypermetropic illumination Illustrations inches increase injurious less lids look matter meridian myopia natural near-point nearer necessary object of vision ophthalmoscope optic nerve optical parallel rays patient person pince-nez plane position posterior pole presbyopia prisms produced Professor proportion pupil rays of light rays refracted render require retina retinal image sclerotic screen short-sighted shown in Fig side sight Silber spectacles squint straight muscles surface Surgeon transparent vergence vertical violet visual visual angle writing yellow spot