Onset of ocular action

No initial reaction; symptoms do not appear for some hours.

Immediate and painful reaction.

Pupillary reaction

Not affected.

Immediate strong miotic action.

Vascularization

Never occurs unless limbus is damaged.

Independent of the site of the primary lesion; occurs when a sufficient dose reaches the cornea or limbus.

Vascular lesions

Do not all perforate; tend to be chronic, to relapse, and to show intracorneal hemorrhages from newly formed vessels; vessels have peculiar and characteristic form.

Not all vascular lesions perforate; there are no relapses and no recurrent hemorrhages.

Cholesterin and other lipoid scars

Follow some vascular lesions, and subsequently these tend to break down (delayed mustard gas keratitis).

Do not occur, and there is no late breakdown due to them.

Perforation and loss of an eye

Caused by relatively large doses (0.005 cc), and even then are long delayed. Perforation never occurs as a primary lesion before the stage of vascularization.

Caused by relatively small doses (0.001 cc); perforation may occur within a few days without vascularization, or later after the entry of blood vessels.

Edema

Edema of the conjunctiva and cornea is present, but not excessive.

Edema of the lids and conjunctiva is immediate and severe. Edema of the cornea is extreme in all but the smallest doses.

Iris and ciliary body

Relatively little involvement. No late effect on pigment.

Early and severe involvement, followed by gradual depigmentation and shrinkage of the iris stroma.

Vessel formation

Characteristic vessels form in cornea and conjunctiva.

Corneal vessels do not show the characteristic varicosities of mustard vessels.