PERIODIC OPHTHALMIA. 
411 
It is well to remember that when one eye is affected with 
the disease, that, as a rule, the other will become affected 
sooner or later. This should be especially remembered, for 
when you have one eye cleaned up and apparently sound, a 
month or two later you are called to treat the other eye, 
affected more or less severely, either from sympathy, direct 
nerve influence, or by infection. 
The effects of cocaine appear to be especially beneficial in 
this operation. It renders the cornea and the mucous 
membrane of the conjunctival sac and membrana nictitans 
non-sensitive to pressure, touch of the fingers or speculum. 
A great advantage from its use is its action on the small 
capillaries; they become for a time contracted, and the 
operation is nearly bloodless. It also renders the use of 
fixation forceps unnecessary, as the eye-ball can be moved in 
any direction, or to any position. A solution of cocaine— 
five per cent.—is most advantageous ; discs of gelatine with 
cocaine are not satisfactory. 
The antiseptic solution to be preferred is boric acid, 
especially in treating the eye, as the bicloride of mercury 
causes the cornea to become too dry. By its continued use, 
the epithelial layer is lifted up as a vescicle, and extensive 
and obstinate opacities may be formed. 
In using ointments or powder containing mercury the 
administration of iodide of potassium internally is to be 
avoided, as this reaches eventually the tear fluid and the 
secretions of the conjunctiva, and changes it into the 
bin-iodide of mercury, which is very irritating and painful to 
the eye. Also calomel, if allowed to remain in the eye in too 
great quantities during the night, would be changed into the 
bichloride of mercury and act as a caustic, and might cause 
deep burns, followed by extensive sloughs of the conjunctiva, 
especially of the lower lid. 
Cleanliness is very important before, during, and after 
the operation. Sponges are to be avoided, and absorbent 
cotton substituted. Instruments are best disinfected by the 
heat and flare of an alcohol lamp. One of the best and cheap¬ 
est antiseptic solutions to be used in washing away discharges 
