116 HEALTH AND DISEASE 



Au alteration iu the form of the coruea, consisting of a protrusion of 

 the central portion in the form of a grape-like tumour (fig. 253) (Staphy- 

 loma) associated with distension of the glolje of the eye, has been met with 

 occasionally as the result of inflammation. It is obvious that no treat- 

 ment which can be employed would prevent the loss of sight m such a 

 case, but when the appearance of the organ is objected to, the tumour 

 may be dissected off with a reasonable probability of the wound closing, 

 or the eye may be entirely extirpated by an operation which is very easily 

 performed and is generally successful. 



Periodic or Recurrent Ophthalmia. — A form of ophthalmia which 



is known as periodic, or sometimes as " moon-blindness ", is peculiar to 

 the horse, and in all probability is chiefly 

 due to heredity. The cause to which it 

 was formerly attributed, i.e. irritating gases 

 and badly ventilated stables, is evidently 

 inadequate to explain its presence. The 

 fact that other animals are constantly ex- 

 posed to the influence of the same con- 

 ditions without suffering is in itself sufficient 

 Fig. J.-. i.-ueeun. lit Ophthalmia to throw Considerable doubt on the once- 



Eye showing an angular conditisn of the aCCeptCcl explanation, 

 upper lid the result of a succession of J- . i i n i i i t 



attacks of Specific Ophthalmia. it IS Undoubtedly true that the disease 



is much less frequent than it formerly was, 

 and it is also true that for many years past great care has been taken 

 at horse shows to reject all animals which gave evidence of having 

 suffered from the malady. In this way breeding animals affected with 

 the disease have been marked out, and their use largely curtailed in 

 consequence. 



Symptoms of periodic ophthalmia are in the first instance closely allied 

 to those of simple ophthalmia, but a great contrast is observed in the more 

 advanced stages. Swelling of the eyelids, redness of the conjunctiva, and 

 discharge of tears are the chief indications of the early stage of the disease. 

 To the experienced examiner the diseased eye presents a characteristic 

 appearance even at the outset of the malady, which becomes more and 

 more pronounced with each succeeding attack. A slight contraction iu 

 the centre of the upper lid, the edge of which is drawn upward (fig. 254), 

 gives a peculiar triangular appearance to the opening between the two lids. 

 This is an appearance which is not met with in simple ophthalmia; the 

 swelling is less marked also, and when there is a sufficient space between 

 the partially closed lids to allow the surface of the cornea to be seen, a 

 peculiar amber tinge of the part is observed. This is caused by a yellow 



