Causes.—­The cause is usually Bright’s disease, (nephritis) and usually the chronic Interstitial variety.  Pregnancy causes it sometimes.  Interference of the vision, sight, is what the patient complains of.  This may be very slight, when you consider the great changes occurring in the retina.  Such patients are subject to attacks of temporary blindness of uremic origin.  The vessels of the retina are swollen and tortuous.  Bleeding and shining white patches are scattered through the back part of the eye and a peculiar arrangement of glistening white dots around the yellow spot.  This disease shows itself late in Bright’s disease and the patient is not likely to live more than two years after the appearance of this eye lesion.

Treatment.—­It sometimes occurs during pregnancy.  Then the question of inducing premature labor arises.  There is no local treatment that can be of any use when it is caused by Bright’s disease.

Fitting glasses.—­This is done by lenses and prisms, etc.

Lens.—­A lens is made of glass and prisms graded in strength, one surface curved, and has the power of refracting or changing the direction of the rays of light.  A prism is wedge-shaped and bends rays of light towards its base.  A great many people are troubled with their eyes, much more than years ago.  We even see little children wearing glasses.  It is unfortunate, but true, that even more children and grown people should wear them.  Fitting glasses is an art in itself.  It takes more ability to fit glasses well than it does to operate well.  Poorly-fitted glasses are not only annoying to the wearer, but dangerous.  Glasses rest the eyes, not tire them.  When the eyes water and feel tired or strained, even after using them but little, glasses are needed.  Headaches are frequently caused by the eye strain.  When glasses are needed it does not pay to put off getting them and the person needing them should go to one competent to properly fit them.  A great many eyes are hard to fit, and they need not only ability to fit them well, but time and attention must be given to fitting them properly.

[356 Mothers’ remedies]

Squint or strabismus.—­Both lines of sight are not directed towards the same object of fixation.

Internal or Convergent Squint.—­Where one eye is turned inward toward the nose.

External or Divergent Squint.—­One eye turns outward toward the temple.  Squinting upward and downward are uncommon.

Causes of Convergent (Internal) Squint.—­It generally appears between two and five years; at first periodically, later constantly.  The patient is generally far-sighted.

Treatment.—­Internal squint in very young children may be treated by covering the well eye and forcing the child to use the other.  When the child is old enough, proper glasses should be worn.  Operation can be done when needed and is generally successful.