Volume 1

The American encyclopedia and dictionary of ophthalmology / edited by Casey A. Wood, assisted by a large staff of collaborators.

Date:
1913-1921
Catalogue details

Licence: In copyright

Credit: The American encyclopedia and dictionary of ophthalmology / edited by Casey A. Wood, assisted by a large staff of collaborators. Source: Wellcome Collection.

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    velop or, having developed, are destroyed by the pressure of amni- otic bands, one is unable to state in the light of present knowledge. The condition is very rare. The incomplete forms are usually de- scribed under the heading of micro-blepharon in which cases the incomplete lids may take the form of nodules or narrow folds of skin surrounding an ill developed or rudimentary eyeball. Where micro- blepharon is present one frequently finds concomitant defects in the eyeball, clefts in the lids of the opposite eye or anomalies in other parts of the body.—(W. F. H.) Ablepharus. (L.), n. m. One afflicted with ablepharia (q. v.). Ablepsia. n. Blindness. Ablepsie. (G.) Blindness. Ablepsy. n. Blindness. d’Abie’s optophone. This is an instrument intended to enable totally blind persons to recognize, locate, and even measure light by means of the ear. It is based upon well-known property of selenium of changing its resistance under the action of light. The principle on which the optophone is constructed is the following: A cur- rent from a small battery is sent through a network of four con- ductors known as a “Wheatstone bridge.” Two of these conductors are wire resistances of a few hundred ohms each, the third is a sele- nium “cell” (now more appropriately termed a “selenium bridge”), and the fourth is an adjustable resistance, made of graphite de- posited on ground-glass or unglazed porcelain. When the first two resistances are in the same ratio as the last two, then no current will flow across the network. But a current will flow as soon as one of the resistances changes, as does that of selenium under the action of light. It is this current, made audible in a telephone, which is utilized in the optophone. The instrument consists of two parts, is light and portable and requires very little current, a sin- gle pocket “refill” sufficing for days of working. It is believed that great possibilities of aid to the blind may lie in this instru- ment. Ablosen. (G.), tr. v. To resolve, disperse. Ablosend. (G.) Resolvent. Ablosung. (G.),n. A detachment (as of the retina). Ablosung der Netzhaut. (G.) Detachment of the retina. Abmagerung. (G.), n. Emaciation; atrophy. Abmatten. (G.) To fatigue or tire. Abmeisseln. (G.), tr. v. To remove with a chisel. Abmessen. (G.) To measure; to measure exact. Abmessung. (G.) Measuring, measurement, adjustment.
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