42 Mr. Ware's Observations on the near 



the amendment is occasioned by a decay o^adeps at the bottom 

 of the orbit ; in consequence of which the eye, from a want 

 of the usual support behind, is brought, by the pressure of the 

 muscles on its sides, into a Jcind of oval figure, in which state 

 .the retina is removed to its due focal distance from the flat- 

 tened cornea. But if a morbid absorption of adeps at the bottom 

 of the orbit were sufficient to restore the presbyopic to a 

 good sight, it might be expected, that a morbid accumulation 

 of adeps in this part would produce a presbyopic or distant 

 sight. This, however, has not happened in any of the cases 

 that have come under my notice. On the contrary, in 

 some such persons a degree of near sightedness has been in- 

 duced by the accumulation ; and in others the sight, with 

 regard to distance, has not been affected by it. It appears 

 to me more probable, that this remarkable revolution in the 

 sight of old persons is occasioned by an absorption of part of 

 the vitreous humour ; in consequence of which, the sides of 

 the sclerotica are pressed inward, and the axis of the eye, by 

 this lateral pressure, is proportion ably lengthened. An altera- 

 tion of this kind is also sufficient to explain the reason, why 

 such aged persons retain the power of distinguishing ob- 

 jects at a distance, at the same time that they recover the 

 faculty of seeing those that are near; since the lengthened 

 axis of the eye leaves the power by which it is adjusted to see 

 at different distances, precisely in the same state, in which it 

 "was before the lengthening of the axis took place.* 



• Dr. Young, in the paper to which I alluded in page 38, has described a great 

 number of ingenious experiments devised by him, to shew that the faculty of seeing 

 at different distances is produced by a power in the crystalline humour, to become 

 more or less convex, according as the object is more or less distant from the eye. 



