LEAD POISONING may cause blindness, with atrophy of the optic nerve.
Diagnosis. — Sudden or rapidly pro gressive amblyopia should always raise the suspicion of a toxic origin. Inquiry will elicit the history of exposure to one of the above noxious agents. Testing the field of vision will determine the diagnosis. The especial characteristic of the one group of amblyopias, such as that from tobacco, is the central scotoma; but the patient may not at first recog nize that the cloud he complains of be fore his sight is confined to the centre of the field of vision. In the same way, until attention is called to it, limitation of the field of vision may not be appre ciated by the sufferer from quinine blindness or similar affections.
Prognosis. — When exposure to the toxic influence is continued useful vision is likely to be lost. With prompt and early suspension of the poisonous agent, the loss of sight will be checked, and often practically normal vision may be regained. For tobacco-amblyopia, the chance of full recovery is very good, if the case is treated properly during the first few weeks; and after many months prolonged treatment may produce great improvement in vision. Quinine-blind
ness is at first complete, but almost al ways some vision returns, and central vision may become normal. Some nar rowing of the field of vision remains per manently in all severe cases. The am blyopia from methyl-alcohol may im prove for a time, and then grow worse to complete blindness with optic atrophy. In general, the severity and duration of the poisoning influences the completeness of final restoration of sight.
Treatment.—The first and the essen tial point is to stop the entrance of the poison, by total cessation of its employ ment in any form; the use of tobacco and alcohol, as with all other toxic agents, must be given up. The admin istration of iodoform, quinine, salicylic acid, or acetanilid must be suspended. Workers with carbon bisulphide, nitro benzol, or lead must change their occu pations. The elimination of the poison may be hastened by potassium iodide in moderate doses, Turkish baths, and pilocarpine sweats. The general health should be looked after at every point. Strychnine is to be given in increasing doses up to the limit of tolerance.