DR. HUBERT AIRY ON A DISTINCT FORM OF TRANSIENT HEMIOPSIA. 259 
localized in any particular part: it lasts .for five or six hours or more, accompanied with 
slight nausea. 
Such is the normal course of an attack of transient Hemiopsia in my case. I will 
M 
presently mention such abnormal forms as seem to have interest. 
Reviewing the nomenclature of the disease, I think we must recognize the inaccuracy 
and insufficiency of the name ‘ Hemiopsia’ or ‘ Hemiopia,’ used by Brewster and others, 
especially as the same name has been given, appropriately, to the graver and more per- 
manent half-blindness, in which “ the line of demarcation between the sensitive and 
blind part of the retina is vertical and sharply defined” (Bader, p. 447). I am tempted 
to look for a single word which shall express the most striking feature of the morbid 
vision. In Sir John IIersciiel’s account (above, p. 251), it will be seen that he was much 
struck by the resemblance to a fortified wall “ with salient and re-entering angles, bas- 
tions, and ravelins and writing last year, he speaks of the visual phenomenon as “ the 
‘Fortification Pattern.’ ” Dr. Fothergill’s words (above, p. 254) are, “ surrounded with 
luminous angles, like those of a fortification .” Other persons also have habitually 
used this expression in describing their own experience. I think this similitude may 
furnish me with the word I seek, and I venture to propose the name ‘ Teichopsia’ (rsi%o£, 
town-wall, ofig, vision) to represent the bastioned form of transient Hemiopsia which I 
have been describing, not without a reminiscence of some words of Tennyson’s : 
“ as yonder ivalls 
Rose slowly to a music slowly breathed, 
A cloud that gathered shape.” 
Various particulars, which would have burdened the description, I have reserved for 
consideration here. 
Circumstances of the attack . — Want of exercise, sedentary employment, close reading 
and writing, are the usual antecedents of Teichopsia. It generally comes on while the 
eyes are engaged with toilsome reading. Several times I have believed the attack to be 
favoured by bad windy weather, for the reason that different members of my family have 
been affected on the same day, in such weather, though unaware of the synchronism till 
afterwards. I am careful to add this last caution, because I have thought (and by 
reference to the quotation above, page 252, it will be seen that Sir John Herschel 
entertained the same idea) that an attack might be induced by the mind dwelling on the 
description or imagination of the thing. 
Sudden change of air and living have sometimes seemed to be the exciting cause. On 
one occasion, some years ago, on going into the country for a winter holiday, I had three 
or four attacks in the first two days. 
Over exercise may bring it on, I believe. It has come on after a long walk before 
breakfast. It will be remembered that Dr. Wollaston attributes his first attack to a 
similar cause. 
