Refracting Media.—­The aqueous humor completely fills the anterior and posterior chambers of the eyeball.  The anterior chamber is the space bounded in front by the cornea; behind by the front of the iris.  The posterior chamber is a narrow chink between the peripheral part of the iris, the “suspensory ligament” of the lens and the “ciliary processes.”

[348 Mothers’ remedies]

The vitreous body forms about four-fifths of the entire globe, It fills the concavity of the retina and is hollowed in front, forming a deep cavity, for the reception of the lens.  It is perfectly transparent and of the consistency of thin jelly.  The fluid from the vitreous body resembles nearly pure water.  The crystalline lens enclosed in its capsule is situated immediately behind the pupil, in front of the vitreous body.  The lens is a transparent, double-convex body.  It is more convex on the posterior than on the anterior surface.  The rays of light go through this body and converge to a point at the back of the retina.

Blepharitis Marginalis.—­This means a chronic inflammation of the margin or edge of the eyelids accompanied by congestion, thickening and ulceration of the parts and the formation of scales and crusts.

Causes.—­The underlying cause is often an inflammation of the conjunctiva where the proper care is not taken in cleansing the roots of the lashes when the discharge collects.

Other causes are keeping late hours, smoke and dust.

Symptoms.—­The red swelling along the roots of the lashes is often the only symptom.  This comes and goes at the least excuse, such as eye strain, late hours, dust and wind.  Scales and dust form in the severe forms, of the disease.  It is most common in children, extends over many years and may finally result in the loss of the lashes, with the edge of the lid, thickened, reddened and turned out.

Treatment.—­This is tedious.  Fit glasses if there is eye strain, reform the mode of life and attend to any constitutional disease that may tend to make it worse.

Local treatment.—­Keep the parts thoroughly clean.  The edges of the lids should be washed carefully with soap and warm water or mild solution of borax or soda until the crusts are all cleaned off and then use at night an ointment composed of the following ingredients: 

Yellow oxide of Mercury       2-1/2 grains
Petrolatum                    2-1/2 drams

Mix and make an ointment and rub on the edge of the lids every night, first cleaning them.  The conjunctivitis must be cured.

Stye (hordeolum).—­This is a swelling beginning in a gland or glands at the edge of the lid and pus forms finally.

Causes.—­Inflammation of the edge of the lid, stomach trouble, run down condition, poorly fitted glasses, when glasses should be worn to relieve the eye strain.

Symptoms.—­Itching and burning feeling followed by a red swollen area (lump) at the edge of the lid.  Later it comes to a point and discharges.