THE HALO SYMPTOM IN GLAUCOMA. 
BV 
S. O. RICHEY, M.D., 
OF WASHINGTON, D. C. 
REPRINTED FROM 
ANNALS OF OPHTHALMOLOGY AND OTOLOGY, Vol III, No. 3. 
July, 1894. THE HALO SYMPTOM IN GLAUCOMA. 
By S. O. Richey, M. D., 
OF WASHINGTON, D. C. 
HALO is classed among the prodromata of glaucoma: it may 
occur later in the progress of primary simple glaucoma. 
Some subjects of glaucoma, more observant than others, mention 
it without suggestion from the physician. In many instances it is 
not noted, or little importance is attached to it. A few attempts 
have been made to explain it. DeWecker thinks it “ due to very 
slight alterations in the epithelial layer of the cornea, produced by 
temporary increase of pressure.” Wolfe suggests that it “ may be 
owing to dilatation of the pupil, to change in the lens, or to dis- 
turbance in the circulation.” Neither “ disturbance of the circula- 
tion nor dilatation of the pupil,” when they exist, under other 
circumstances, seem to cause the phenomenon. 
“Alteration in the epithelial layer of the cornea,” and “change 
in the lens” are phrases of vague significance, the exact meaning 
of which may be only surmised, except that Dr. deWecker quali- 
fies his statement by the expression “ is analogous to a similar 
phenomenon witnessed in most cases of conjunctival catarrh where 
there is irregular desquamation of the epithelium.” In conjunc- 
tival catarrh this peculiarity is rather due to diffraction of rays of 
light by globules of secretion on the surface of the cornea, as it 
disappears when they are removed. Moreover, cocain which 
disturbs the corneal epithelium lessens conjunctival secretion, and 
dilates the pupil, does not seem to produce the halo. Let it 
be further suggested that constant slight changes in the corneal 
epithelium are physiologically present without the phenomenon ; 
therefore, we must look for some other explanation. Dabrowol- 
sky, of St. Petersburg (Archiv. of Ophth., Yol. XV., p. 
267, 1S86) assumes that the glaucoma halo “ depends upon irri- 
tation of the retina and optic nerve by hyperemia,” in support of 
which he cites a personal experience while in a Russian bath. The 
rainbow rings became even more distinct when he entered a cooler 
room. He continues, “for the last few months I have constantly 
seen these rings around the lamplight in the evening. There is no 
noticeable increase of tension and the visual acuteness is fjp 
Tension of accommodation always renders them (the rings) more 2 
distinct. As the cause of glaucoma must be in action previous to 
increase of tension, or diminished acuteness of vision, and as the 
halo is a prodrome, Dr. Dabrowolsky’s eyes must rest under sus- 
picion of inherent tendency. 
The halo is never constant, but appears and disappears to recur 
again, and with increasing frequency as the disease develops. At 
one time it may be a corona ; at another, it appears in the shape 
of varicolored sparks of light. This intermittence and change of 
form would indicate that the cause is not persistent, that at times 
it lacks force, or distribution. Pressure upon the globe will pro- 
duce a ring of colored light, or a luminous spot, always opposite 
to the point of pressure. The halo may be present in glaucoma 
with seeming normal intra-ocular tension, and may be absent dur- 
ing increased tension; gradual, steady pressure will not produce 
sparks of light. The cause of the halo would seem not to be in 
the retina itself, but in the media anterior to it. Its variability 
suggests the aqueous humor, or some surface subject to the 
influence of the aqueous humor, for it is in the serum of the blood 
that the chief deviation from the healthy standard is perceived, 
products of excretion which have not been eliminated. (Garrod). 
The laws of nature are undeviating; the law of gravitation, ter- 
restrial or celestial is the same ; so with the law of light. The 
lunar halo is a familiar object, the cause of which does not exist in 
ourselves nor in the moon, but in the intervening media whose 
character changes. The Descartes theory of the encircling lunar 
halo was accepted by Marriotte, Dr. Thomas Young and Sir Isaac 
Newton, and remains to-day the unquestioned explanation. 
According to Descartes, it is owing to the refraction and reflec- 
tion of rays of light by minute snow and ice crystals in the upper 
strata of air, and occurs in the presence of the cirrus, or ice-cloud. 
Professor Cleveland Abbe explains the arrangement of colors in 
a circle of 22° radius, the inner edge red, the outer edge blue, to be 
“light polarized in direction of tangent to circumference; it is 
formed by light passing through the alternate faces of hexagonal 
ice-crvstals in the direction of minimum deviation through the base 
and sides of right prisms.” 
The prevailing arrangement of colors in the glaucomatous halo 
is red in the outer margin and bluish-green in the inner margin, 
the reverse of the lunar halo. 1 The difference in arrangement of 
11 he transposition of the colors of the halo is very strong evidence that 
the cause of the halo in glaucoma is to be looked for posterior to the iris, in 
accordance with the disposition of rays of light passing through the aper- 
ture of a screen. 3 
colors is owing to a difference in the position of the refracting 
crystals relative to the eye ; in one case, posterior to the pupil; in 
the other, external to the eye. 
“ Sodic chlorid -I- urea forms shining rhombic prisms,” 
(Landois & Sterling Text-book on Physiology, second Am. edition, 
page 432). Acid sodic urate appears as a brick-red deposit, more 
rarely gray or white, in rheumatic or febrile conditions. Micro- 
scopically, it is completely amorphous, consisting of granules 
which sometimes have spines on them. The potash salt is the 
same. They are easily soluble in warm water. (Yid. Suf, page 
433). As the menstrua cool they are precipitated. 
When the urates in the blood are in excess (uric acidemia), the 
same influences which determine their presence in the synovial 
fluid of the joints and their precipitation upon the serous surfaces 
operate in the eye which is more exposed to vicissitudes of tem- 
perature. Hence, variation in glaucoma halo, with variation of 
urates in the blood, might clearly occur without present change of 
intra-ocular tension. 
The glaucoma halo might “ depend upon irritation of the retina 
and optic nerve,” not caused by simple hyperemia, but by pre- 
cipitated urates; or, it may be due to the presence in the aqueous, 
or vitreous, humor of urates in the shape of rhombic prisms or 
amorphous granules (with or without spines), with power to cause 
diffraction of light. The prisms formed by sodic chlorid -j- urea 
at least have this faculty. ANNALS OF OPHTHALMOLOGY AND OTOLOGY. 
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