CHAPTER XIII 



EFFECTS ON THE VISUAL APPARATUS 



The visual apparatus includes the eyeballs, together with the accessory 

 organs, lacrimal glands, conjunctiva, etc. General impairment of the visual 

 apparatus has frequently been observed in cases of famine or malnutrition. 

 Recently a specific disorder (xerophthalmia) has been shown to result from 

 deficiency of vitamin A. Apparently the deficiency lowers the resistance to 

 bacterial infection, which is the direct cause of the ophthalmia. Thus dietetics 

 becomes a factor of importance in ophthalmology, and particularly among 

 malnourished children. Following a brief summary, the effects of inanition 

 upon this apparatus will be considered under (A) total inanition, and (B) partial 

 inanition. 



Summary of Effects on the Visual Apparatus 



During total inanition, or on water only, there is but little or no loss (some- 

 times even an increase) in the weight of the eyeballs, although the remaining 

 orbital contents (muscles, fat, etc.) undergo the usual atrophy. In the young, 

 both human and infrahuman, there occurs during chronic inanition a persistent 

 growth in weight of the eyeballs, similar to that found in the nervous system. 

 The eyeballs usually resume their normal proportions after appropriate 

 refeeding. 



During total inanition (complete or incomplete) the eyes may remain normal 

 in appearance; or conjunctivitis, corneal ulceration, etc. may occur (probably 

 due chiefly to vitamin deficiency). Histologically, progressive atrophic and 

 degenerative changes occur in the tissues of the eyeball. These changes are 

 usually comparatively slight, affecting the iris, ciliary processes and muscle, 

 choroid and especially the cornea and retina. The retina may present anemia, 

 edema and cellular degeneration, notably in the ganglionic layer. In sala- 

 mander larvae, mitosis is almost completely suppressed in the cornea during 

 total inanition. 



In the various types of partial inanition, as in total inanition, there is a 

 marked tendency to progressive increase in the weight of the eyeballs in the 

 young, and little or no loss in adults. Dimness of vision in the form of nyctal- 

 opia (night blindness) or hemeralopia (day blindness) has been observed during 

 famine edema and scurvy, with retinal and conjunctival hemorrhages in the 

 latter. Conjunctivitis may occur in these conditions, as well as in pellagra and 

 especially during aqueous inanition (thirst). 



The visual apparatus in the young is remarkably sensitive to a deficit in 

 vitamin A, which produces a typical ophthalmia in both human and lower species 

 (mammals and birds). In the earlier stages, there is a mild conjunctivitis with 



