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Tonic Pupil: Typical and Atypical Forms and Clinical Observations, Lecture notes of Human Biology

Adie's classification of tonic pupil into typical and atypical forms, each associated with absence of one or more tendon reflexes but no other neurological abnormalities. The typical tonic pupil is characterized by a larger-than-normal, unresponsive pupil with slow contraction and relaxation in the dark and daylight. The document also includes clinical observations of fifteen patients and measurement of pupil diameter and response to stimuli.

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J.
Neurol.
Neurosurg.'Psychiat.,
1949,
12,
219.
THE
TONIC
PUPIL
BY
G.
S.
GRAVESON
From
the
Department
of
Neurology,
Manchester
Royal
Infirmary
The
peculiar
phenomenon
of
the
tonic
pupil
was
first
described
in
detail
by
Strasburger
in
1902.
Later
in
the
same
year
both
Saenger
and
Nonne
reported
further
cases
and
Saenger
proposed
the
name
"
myotonic
pupillary
movement"
for
the
condition.
Until
this
time
the
disorder
had
not
been
separated
from
others
causing
mydriasis
or
alteration
in
the
pupillary
reflexes.
Yet
the
curious
slowness
of
pupillary
movement,
characteristic
of
the
condition,
must
have
been
recognized
earlier;
indeed
in
1818
James
Ware
described
a
patient
who
very
probably
had
a
tonic
pupil.
His
patient,
whose
pupillary
abnormality
had
been
known
to
exist
for
at
least
twenty
years,
was
"
a
lady
between
twenty
and
thirty
years
of
age,
the
pupil
of
whose
right
eye,
when
she
is
not
engaged
in
reading
or
in
working
with
her
needle,
is
always
dilated
very
nearly
to
the
rim
of
the
cornea;
but
whenever
she
looks
at
a
small
object,
nine
inches
from
the
eye,
it
contracts
within
less
than
a
minute
to
a
size
nearly
as
small
as
the
head
of
a
pin
...
its
contraction
never
remains long
after
the
attention
is
withdrawn
from
a
near
object."
After
1902
the
condition
was
reported
on
several
occasions,
both
in
this
country
(Markus,
1906;
Weber,
1923;
Moore,
1923,
1931;
and
Morgan
and
Symonds
1927,
1931)
and
abroad,
but
it
did
not
attract
much
attention
until
the,
work
of
Holmes
(1931)
and
Adie
(1931,
1932).
To
Adie
in
particular
must
be
given
the
credit
for
attempting
a
synthesis
of
available
information
into
a
semeiological
plan.
He
divided
the
tonic
pupil
into
two
forms,
the'
typical
and
the
atypical,
each
of
which
might
be
associated
with
absence
of
one
or
more
tendon
reflexes,
but
with
no
other
neurological abnormality.
Collier
(1933)
first
called
this
combination
"
Adie's
Syndrome,"
a
name
which
has
been
generally
applied
ih
Europe
and
America.
In
this
country,
following
Bramwell's
(1936)
suggestion,
the
double
eponymous
title
of
the
"
Holmes-Adie
syndrome"
has
been
perhaps
more
widely
used.
The
"
typical
"
tonic
pupil,
in
Adie's
view,
was
a
unilateral
disorder
in
which
the
affected
pupil
was
larger
than
normal,
did
not
react
to
torch
light
but
dilated
slowly
in
the
dark,
subsequently
contracting
slowly
in
daylight,
and
showed
a
characteristically
slow
contraction
and
relaxation
with
ocular
convergence.
The
"
atypical
"
forms
were
less
clearly
defined
but
included
some
forms
of
internal
ophthalmoplegia
and
complete
light
rigidity
with
a
tonic
convergence
reaction.
Since
Adie's
description,
this
conception
of
the
atypical
tonic
pupil
has
been
so
far
enlarged
upon
that,
for
example,
Lowenstein
and
Friedman
(1942)
write,
"
In
atypical
cases
all
the
modifications
obserVable
in
pupillary
disease
both
of
syphilitic
and
other
causation
may
be
exhibited."
Similarly
Alajouanine
and
Morax
(1938)
claim
that
between
the
typical
tonic
pupil
and
the
Argyll
Robertson
pupil
all
intermediary
forms
are
possible.
If
these
statements
are
even
partly
true
the
practical
difficulties
of
diagnosis
which
not
infrequently
arise
are
understandable
enough.
Apart
from
what
distinctive
pupillary
abnormali-
ties
must
necessarily
be
found
before
a
diagnosis
can
be
made,
two
other
problems
remain
to
be
solved:
(1)
the
site
of
the
anatomical
lesion
and
(2)
the
nature
and
specificity,
or
otherwise,
of
the
underlying
pathological
process.
This
paper
is
an
attempt
to
throw
light
on
some
of
these
problems.
Clinical
Observations
Fifteen
patients,
twelve
females
and
three
males,
varying
in
age
from
12
to
55
years,
have
been
studied,
in
each
of
whom
was
found
evidence
of
"tonicity
"
of
one
or
more
of
the
three
principal
actions
of
the
intrinsic
ocular
muscles,
viz
:
pupil-
lary
contraction
on
exposure
to
light
and
with
ocular
convergence,
and
the
ciliary
muscle
response
to
accommodation.
The
detailed
clinical
findings
in
these
patients
are
set
out
in
Tables
I
and
II.
Symptoms.-Of
the
fifteen
patients,
eleven
were
originally
seen
because
of
pupillary
inequality
noticed
either
by
themselves,
their
friends,
or
their
doctors;
and
four
attended
because
of
blurring
of
vision
with
or
without
headaches.
219
pf3
pf4
pf5
pf8
pf9
pfa

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J. Neurol. Neurosurg.'Psychiat., 1949, 12,^ 219.

THE TONIC^ PUPIL BY

G. S. GRAVESON

From the Department of Neurology, Manchester Royal Infirmary

The peculiar phenomenon of the tonic pupil was

first described in detail by Strasburger in 1902. Later in the same year both Saenger and Nonne reported further cases and Saenger proposed the

name "^ myotonic pupillary^ movement"^ for the

condition. Until this time the disorder had not

been separated from others causing mydriasis^ or

alteration in^ the^ pupillary reflexes. Yet^ the curious

slowness of pupillary^ movement, characteristic^ of the condition, must^ have been^ recognized^ earlier; indeed in 1818 James Ware described a patient who

very probably had a tonic pupil. His patient,

whose pupillary abnormality had been known to

exist for at least twenty years, was " a lady between

twenty and^ thirty^ years^ of^ age,^ the pupil^ of^ whose

right eye, when she is not engaged in reading or in

working with her needle, is always dilated very

nearly to the rim of the cornea; but whenever she

looks at a small object, nine inches from the eye,

it contracts within less than a minute to a size

nearly as small as the head ofa pin ... its contraction

never remains long after the attention is withdrawn

from a near object."

After 1902 the condition was reported on several

occasions, both in this country (Markus, 1906;

Weber, 1923; Moore, 1923, 1931; and Morgan and

Symonds 1927, 1931) and abroad, but it did not

attract much attention until the, work of Holmes

(1931) and Adie (1931, 1932). To Adie in particular

must be given the credit for attempting a synthesis

of available information into a semeiological plan.

He divided the tonic pupil into^ two^ forms,^ the'

typical and^ the^ atypical, each^ of^ which^ might^ be

associated with^ absence^ of^ one^ or^ more^ tendon

reflexes, but^ with^ no^ other^ neurological^ abnormality.

Collier (1933) first called this combination "^ Adie's

Syndrome," a name which has been generally

applied ih Europe and America. In this^ country,

following Bramwell's (1936) suggestion, the double

eponymous title^ of^ the^ "^ Holmes-Adie^ syndrome"

has been perhaps more widely used.

The "^ typical "^ tonic pupil, in Adie's view, was

a unilateral disorder in which the affected pupil

was larger than normal, did not react to^ torch

light but dilated slowly in the dark, subsequently

contracting slowly in daylight, and showed a

characteristically slow contraction and relaxation

with ocular convergence. The "^ atypical "^ forms were less clearly defined but included some forms

of internal ophthalmoplegia and complete^ light

rigidity with a^ tonic convergence reaction.^ Since

Adie's description, this^ conception of^ the^ atypical

tonic pupil^ has been^ so^ far enlarged^ upon^ that,

for example, Lowenstein and^ Friedman^ (1942)

write, "^ In^ atypical^ cases^ all^ the^ modifications

obserVable in pupillary disease both of syphilitic

and other causation may be exhibited." Similarly

Alajouanine and Morax (1938) claim that between

the typical tonic pupil and the Argyll Robertson

pupil all intermediary forms are possible. If these

statements are even partly true the practical

difficulties of diagnosis which not infrequently

arise are understandable enough.

Apart from what distinctive pupillary abnormali-

ties must necessarily be found before a diagnosis

can be made, two other problems remain to be

solved: (1) the site of the anatomical lesion and

(2) the nature and specificity, or otherwise, of the

underlying pathological process. This paper is

an attempt to throw light on some of these problems.

Clinical Observations

Fifteen patients, twelve females and three^ males,

varying in age from 12 to^55 years, have^ been

studied, in each of whom^ was^ found^ evidence^ of

"tonicity "^ of^ one^ or^ more^ of the^ three^ principal

actions of the^ intrinsic^ ocular^ muscles, viz :^ pupil-

lary contraction on^ exposure to^ light and with

ocular convergence, and the ciliary muscle response

to accommodation. The detailed clinical^ findings in

these patients are set out in^ Tables^ I^ and^ II.

Symptoms.-Of the^ fifteen^ patients, eleven^ were

originally seen^ because^ of^ pupillary inequality

noticed either by themselves, their^ friends, or^ their

doctors; and four attended because^ of^ blurring

of vision with or without headaches.

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Within these limitations the range of values has been: for contraction normal (2) to 90 seconds; for relaxation 4 to 135 seconds (all measurements (^) by stop watch). Only excep- tionally did contraction take longer than 20 seconds or relaxation more than 40. Adie claimed that delay in addition to slowness of movement was the essential feature of the tonic reaction. Again, accurate assessment is difficult and probably necessitates the use of a slit lamp, which was not used in this series; but the irnpression gained has been that such delay is rather unusual and that when it occurs it is more frequently seen at the beginning of contraction than at the com- mencement of relaxation. It is certainly not always seen. One other feature of the convergence reaction has often been stressed, namely, the excessive contraction which may, so it is said, continue even after convergence has been relaxed. Miosis, by which is meant a pupil of 2-5 mm. diameter or less, was produced with convergence in eight affected ### pupils (Cases 3, 9, 10, 13, 14, and 15). However, ### the resting diameters of the pupils in these cases were never greater than 4 mm. and, since in normal eyes convergence may result in a contraction of one ### third of the resting diameter' (Kestenbaum, 1947), this miosis (^) may fairly be regarded as not very excessive. In only one of the (^) eight unilateral cases ### (Case 3) was the affected pupil smaller than the normal one at the end of convergence. Continua- tion of contraction after cessation of convergence was never seen, and it seems doubtful whether this ever occurs. ### If we exclude phases of the disorder in which the ### pupil is dilated and fixed it would seem from this ### series that the essential feature of the tonic pupil is its failure to dilate promptly when the eye relaxes from a convergence movement. This may be the ### only evidence of "^ tonicity "^ of the pupil and it ### clearly is the main justification for the term, because ### sluggishness of contraction may be, in fact, purely' ### a paretic dysfunction. Just as it is probably the ### earliest tonic feature, so it is usually the most pronounced one in a (^) temporal sense, being almost ### always of longer duration than contraction. The two movements may sometimes be equally slow, but relaxation is never faster than contraction. ### Accommodation.-Defective accommodation and ipsilateral frontal headaches^ are^ the^ only ocular ### symptoms produced by the condition. They occur ### in a few patients. In these cases the onset is fairly ### abrupt, the patient noticing that he cannot see objects clearly for a brief period immediately he looks at them. More frequently near objects only are affected in this way; less commonly distant objects are transiently blurred. Power of accom- ### modation may also be weakened as well as delayed and the near point of the eye may recede. These symptoms are associated with an enlarge- ### ment of the affected pupil and they may disappear after a^ period of weeks^ or months although the latter remains. On the other (^) hand, defects of accommodation which have^ never been^ appreciated ### by the^ patient may be^ found^ on^ routine^ testing. ### Accommodation was tested by first measuring the near (^) point of the (^) eye. Then a (^) Jaeger test (^) type ### which could be read comfortably at a distance greater than this (usually J4 to J8 at 30 cm.) was ### held between the patient's eye and a distant object ### (a chimney pot about seventy-five yards away) seen through the window of the room. He was asked to look from one to the other as the test type was removed or replaced and to say immediately when the near or distant object became sharply focused. Any delay was timed by a stop watch. Normally there is no measurable delay. In all except six ### eyes some delay was found by this method. In the sixteen eyes in which such tonic accommodation was present the delay was found on looking only ### from the far to the near object in thirteen cases; ### only from the near to the far object once; and in both directions twice. These results are unusual in two respects ; first, in the matter of their fre- ### quency, for disturbances of accommodation are generally assumed to be relatively uncommon in ### this condition; and, secondly in^ the fact that ### delay in^ focusing was most commonly seen only ### when a near object was being looked at, that is, ### during active contraction of the ciliary muscle. ### Slow relaxation of this^ muscle was rare, a finding ### at variance with^ what is^ commonly described. Delay in accommodation was, (^) therefore, usually ### the result of a feebleness of action of the ciliary ### muscle. In spite of this, however, paresis of ### accommodation, as judged by a near point greater than 20 cm., was seen in only five eyes, Cases 8 and ### 10 being most definite. This slowness of accom- modation was never as great as the corresponding slowness of^ the^ sphincter muscle during conver- gence. It^ varied from^1 to^6 seconds. ### In contrast, therefore, to the convergence reaction, true tonicity, that is, delayed relaxation, of accom- ### modation is less frequently seen than simple sluggish- ### ness of ciliary contraction. The latter is analogous to the^ few instances in which contraction of the ### pupil to light was more delayed than subsequent relaxation. Adie stated that isolated tonic ace was unknown. This is confirmed iI series and no such cases have been literature. In^ all^ the^ sixteen^ eyes^ mer there was a tonic reaction on conver absent or^ tonic light reflex,^ with^ the Case 6 in^ which^ the pupil^ was^ fixed and on convergence. In this patient tion for near^ vision-^ was^ delayed^5 there was a paresis of accommodatio 29 cm.). In brief, therefore, disturbances of tion are common, though they are ofi by the patient, and a slowness of conti ciliary muscle is found more freqai slowness of relaxation. These (^) chang seen in isolation, and their only prac in the diagnosis of the type of tonic presents as a dilated and fixed pupil. Other Pupillary Reactions.-When tightly closed the pupils may contrai persons. Usually, however, they dila the removal of the light stimulus. former reaction occurs probably whether the eyes converge behind th( Similarly tonic pupils may contract^ M are closed. This, as in^ the^ normal^ cast uncommon, having been^ seen^ only^ on^ th in the series. In^ bilateral^ cases^ it^ n marked in^ one eye than another.^ On the pupil shows the^ same^ delay in after voluntary convergence.^ In^ mos ever, the^ tonic^ pupil remains^ uncha during firm^ lid^ closure. Both Holmes and^ Adie^ mention^ tI may contract^ during^ crying.^ This^ i one occasion in Case 12, a child a became alarmed and tearful when to] were to be put in her eyes. Both being widely dilated (9 mm.), sooi down to 7 mm. and slowly dilated afte had ceased. Unfortunately this war Presumably this pupillary reaction^ i more widespread parasympathetic dis occurs in^ crying. Reaction of the Pupil to Drugs.-Th reacts normally to the conjunctival i homatropine and eserine. Alajouanin (1938) go further^ and^ state^ that^ in^ eve is a "^ precocious "^ reaction, dilatation c occurring more rapidly in the affecte( the normal eye. Lowenstein and Frie moreover, found that at a certain contraction of the^ pupil to^ eserine^ th returned. Neither of these observati( ### G. S. GRAVESON commodation confirmed. In two bilateral tonic pupils (Cases n the present 11 and 15) homatropine-^ did^ not^ produce^ full ### found in the dilatation in^ one^ eye.^ In^ all other cases^ tested, ntioned above normal results^ were^ obtained. ### gence and an^ Scheie^ (1940)^ reported^ a^ series of six^ patients^ in exception of all of whom contraction of tonic pupils occurred ### both to light with a 2i per cent. solution of acetyl B methyl ### accommoda- choline (" Mecholyl "), a concentration too weak ### seconds and t6 affect a normal pupil. His results are confirmed In (near point by Walsh (1947), who considers the test of great ### diagnostic value. A 2 per cent. solution of ### accommoda- " Amechol" (Savory and Moore) was used on all ### ten unnoticed patients-2 drops from an unstandardized dropper ### raction of the being placed in each eye. A contraction of 1 mm. ently than a after 30 minutes was seen in four eyes; of 1-5^ mm. ges are never in 2; of 2 mm. in 1 eye; of 2 5^ mm. in^ 1, and^ of ### :tical value is 5-7 mm. in 2. No response was^ found in twelve^ eyes. ### pupil which The response is therefore variable, but the^ test^ is worth applying for a positive result is of great help the eyes are when the diagnosis is in some doubt. ### Lct in normal When contraction occurred with this drug there ## ite, owing to was^ no^ change^ either^ ## in the light reflex or in the W'hether the pupillary^ response^ to^ convergence,^ but^ in^ one Whethens te patient (Case 12)^ the^ delay^ of accommodation^ was ### depends on^ ### abolished and^ the^ near^ point^ of^ the^ eyes^ reduced, ### v closed^ lids,^ and in^ another (Case^ 6)^ the^ delay^ in^ accommodation ### vhen the^ eyes was reduced. e, is relatively iree occasions Associated Loss of Tendon Reflexes.-Of the nay be more fifteen patients studied, twelve had absence of one ### ce contracted or more reflexes, one had a sluggish right ankle ## relaxation as jek, and in only two (Cases 2 and 8) were the t cases, how- reflexes normally brisk. Lnged in^ size^ Associated (^) Symptoms.-Apart from (^) blurring of hat the pupil vision and^ ipsilateral^ headaches,^ the^ Holmes-Adie was seen on syndrome^ is generally considered^ to^ be^ asymptom- lged 12 who atic.^ Holmes^ (1931),^ it^ is^ true,^ mentioned^ the ### Id thatLd that dropsdrops occurrence of^ mild^ pains^ and^ pareesthesix^ in^ the limbs at the time of onset of the pupillary disturb- icontracted ances, but Adie did not refer to them. (^) French n hrcsobntrad writers, however, have frequently^ stressed^ the srnot timed existence^ of^ obscure^ pains^ in^ many^ patients^ with is part of a^ this^ syndrome,^ pains^ which^ can^ be^ related^ neither ## charge which to^ the^ pupillary^ or^ the reflex^ changes.^ Aching ## .pains, muscle^ stiffness, cramps, and^ even^ sharp ### stabbing pains of a lightning type have been ### ne tonic pupil described in the limbs. Severe^ localized^ or^ general- ### instillation of ized headache^ of-both^ migrainous^ and^ non-specific ### ie and Morax type and unrelated to the pupillary abnormality, vry case there anginal chest pains, and pains in the throat and ### r contraction neck have also been reported (Barre and Klein, d eye than in 1934; Lhermitte, 1937; Alajouanine and Morax, ### dman (1942), 1938; Sigwald, 1941). ### stage of the^ Careful^ inquiry^ in^ this^ group^ of^ patients^ revealed ### ne light, reflex that such symptoms are, in fact, not uncommonly ### ons has been experienced (Cases 6, 7, 9, 14, and 15). Their ## 228 G. S. GR logical disease. With the one exception mentioned, no cause was found for the disorder in any of the present cases. The Anatomical Site of the Lesion Several suggestions have been made about the ### possible- site of 'the lesion causing a tonic pupil. ### The absence of any post mortem confirmation ### renders discussion purely speculative, but in spite ### of this the clinical features of the conditioA, when ### critically considered, limit the possibilities to a greater extent than theories have hitherto suggested. ### Five sites have been postulated: (1) the^ supra- ### nuclear oculomotor pathways (Lowenstein and ## Frie4,Man, 1942), (2)^ the^ hypothalamus (Kennedy ### and others, 1938), (3) the third nerve nucleus (Adie, ### 1932; Behr, 1921), (4) the ciliary ganglion and/or the ciliary nerves (Magitot, 1911), and (5) the, ### sphincter muscle (Saenger, 1902). ### Of these hypotheses, (1) and (2) may be^ dismissed at once for the absence of a light response in a unilateral tonic pupil with the retention of a con- sensual reaction^ in^ the normal^ pupil places^ the lesio'n on the efferent limb of the light reflex arc. ### Saenger's suggestion that the condition is^ a^ disorder ### of the sphincter muscle^ analogous to^ the^ myotonia of ThomsoiVs disease- may likewise be eliminated. ### The not^ infrequent absolute^ rigidity of the^ pupil ### to light, and less^ often^ to^ convergence, together with ### its normal contraction when stimulated directly by ### pilocarpine, clearly indicate that the lesion is in the ### nervous pathways controlling pupil movement. ### It seems most likely, therefore, that the lesion ### affects either the vegetative portion of the oculo- ### motor nucleus or some part of the peripheral path ### of its emerging fibres. At this point argument is ### harnpered by a lack of precise anatomical knowledge ### concerning the origin and course of fibres which ### control the pupillary reflexes. It is generally agreed ### that the Edinger-Westphal nucleus is the origin of ### fibres which subserve the light reflex. These^ run ### to the sphincter muscle via the ciliary ganglion and ### the short ciliary nerves. They are usually described ### as being unilateral in distribution. Langworthy and Ortega (1943), however, state that each nucleus supplies fibres to both oculomotor -nerves. If this ### is so, then unilateral disorders of the light reflex ### can only arise from peripherally situated lesions. ## If n6t, however, it^ is^ conceivable that^ the^ changes ### seen in^ the^ tonic^ pupil may have a^ central^ cause. ### Greater obscurity surrounds the pathway of ### fibres which govern reflex pupillary contraction on ### convergence of the eyes. Its origin is depicted ### sometimes as the caudal end of^ the^ Edinger- ### Westphal nucleus, sometimes^ as^ the^ median nucleus ### of Perlia Whence fibres run to both oculomotor nerves. Their peripheral pathway is unknown, but they probably do not pass through the ciliary ganglion. Foerster and others (1936) have shown that removal of this structure in apes abolishes the light reflex but not 'pupillary contraction on con- vergence. In man, Nathan and- Turner (1942) have similarly reported isolated light rigidity of^ the ### pupil following head injuries in^ .which it^ seemed reasonably certain that the traumatic lesions were ### peripherally situated. They suggest that conver- gence fibres may relay in the episcleral ganglia of ### Axenfeld which lie in the scleral canals in close proximity to the short ciliary nerves. In the midst of this anatomical uncertainty, any attempt to localize further the site of disturbance of the tonic pupil must remain hypothetical. There seem to be valid reasons, nevertheless, for rejecting ### Adie's theory of a central nuclear disturbance. ### The term tonic pupil conjures up an idea of pupillary ### rigidity dependent on excessive tone preventing ### sphincter, movement. Adie (1932) for instance, ### speaks of a pupil " so stiff that at the time of ### examination no reaction to light or on convergence ### is obtained "^ and, again,, visualized stimuli " stored in excess and slowly liberated" from the cells of the oculomotor nucleus so producing slowness of contraction and relaxation. These two ideas are ### mutually exclusive since the first would depend 'on ### an excessive' ahd continuous sympathetic toine, ### whilst the second implies a continuous parasympa- ### thetic discharge. ### Moreover, since-, as we have seen, a tonic pupil may be persistently larger or smaller than normal ### and is always irregular, it is difficult to conceive how these various changes may result from a nuclear lesion. ### We are therefore left with the hypothesis that the lesion lies in the (^) peripheral oculomotor pathway ## viz. in^ the^ ciliary^ ganglion or the short ciliary nerves-a suggestion first made by Magitot (1911) ### and lately revived by Scheie (1940) and Leathart ### (1942). There is much to recommend this idea, though in its simplest form it fails to explain all the changes seen. Scheie suggests that there is an ### incomplete interruption of transmission in the ### ganglion or nerves which accounts for the sluggish- ### ness or absence of pupillary contraction. 'He further suggests that this partial interruption of ### conduction results in a slow liberation of acetyl- choline at the myoneural junction which diffuses ### through the sphincter muscle and so hinders its ### relaxation. If this were so it- might be expected ## that 'pupillary contraction would start in isolated segments of the iris and spread slowly to neighbour- ### ing ones.^ In^ fact^ no-such movement occurs.^ When contraction occurs the iris widens more or less ### THE TONIC PUPIL 229 ## uniformly so that the irregularity of its margin choline at the myoneural junction prevents normal ### remains unchanged. Nevertheless the implication relaxation and results in slowness of dilatation after ### of Scheie's suggestion, namely that there are the pupil contracts. This is best' seen with the' ### probably two fundamentally distinct changes, one convergence movement which is a stronger stimulus ### in the peripheral nerve the other at the myoneural to pupillary movement. Such a biochemical ### junction, seems a new and fruitful approach to the change may fluctuate' and be responsible for the ### problem. occasional variable size of the tonic pupil from day ### We have seen that sometimes light rigidity of the to day. ### tonic pupil is complete and that there may be no The site of the lesion producing a tonic pupil is ### movement of the pupil with ocular convergence, therefore, on this view, at the efferent end of the ### no matter how intense the stimulus may be. There pupillary reflex pathway. Circumstantial evidence ### is, in fact, in such cases a paralysis of the sphincter supporting this is found in the occasional occur- ### muscle and the pupil is dilated. This can only be rence of a tonic pupil after orbital injuries. Such ### the result-of an interruption of fibre conduction, cases have been recorded by Axenfeld (1906) and ### In less severe cases the pupiL contracts only under Ohm (1907). ### intense illumination and does so slowly. This If this hypothesis is correct it follows that the ### suggests a partial interruption of conduction in the tonic pupil should always be larger tha-n normal. ### efferent fibres, and we may suppose that usually In most cases this is so, but occasionally it may be, ### this affects the short ciliary nerves to a greater smaller and sometimes even miotic. In such cases ### extent than the still hypothetical convergence fibres, there may be, in addition, a paresis of the dilator ### for in most cases convergence results in pupillary mechanism, and it may be that the same process ### movement when the light'reflex is completely or that attacks the parasympathetic fibre spreads to ### almost completely absent. The irregularity of the adjacent sympathetic nerve endings. The very ### pupil may be explained by supposing that these occasional occurrence of a partial ptosis in associa- ## changes do not affect the^ ciliary nerves^ uniformly. tion with a tonic pupil (Alajouanine and Morax, ### Sluggishness of^ contraction is, therefore,^ merely 1938; Moore, 1931) supports sucli a view. ### an indication of a partial interruption of conduction The very frequent association of the tonic pupil ### in the efferent fibre. But delayed conduction will with absent tendon reflexes raises the suspicion ### not explaiii slowness of relaxation. Here we must that the two phenomena have a common' patho- ### assume a functional disturbance^ at^ the^ myoneural logical cause and a similar underlying anatomical ### junction; that, just as^ there^ is^ a^ slow^ liberation of^ or biochemical defect. Tendon areflexia in such ### acetylcholine, so^ its^ destruction^ by cholinesterase^ cases is unaccompanied by any of the objective ### is delayed. The contraction of a tonic pupil motor or sensory changes, which in other diseases ## produced by concentrations of acetyl B methyl help to determine the site of the lesion causing loss ## choline which are too weak to affect normal pupils of reflexes. This isolation of the absent reflex, ### lends support to this suggestion, for in normal eyes however, may possibly be a point in favour of ### this substance is presumably destroyed by -the regarding it as being due to a peripheral defect. ### cholinesterase present. Whether this lies on the sensory side of the reflex ## It is, therefore, possible to construct a plausible arc, whether, for example, there is some change in ## working hypothesis concerning the underlying the str6tch receptors, or on the motor* side, as for ### physiopathological disorder which results in a instance in the motor fibre or at the myoneural' ### tonic pupil. There is, first, a disturbance of junction is, however, quite unknown. Arguing by ## conduction in pupillomotor fibres, and secondly analogy from the probable site of the lesion causing ### an alteration in the chemical changes resulting from the tonic pupil, it seems perhaps more likely that ## such stimuli at the myoneural junction. Possibly the lesion is in tlhe motor pathway, but this con- ### the latter is a sequel of the former. The conduction clusion is purely a speculative one for as yet we ### defect occurs in^ the short ciliary nerves conveying possess no knowledge, either clinical or patho- ### the light 'reflex fibres and, to a greater or lesser logical, to help in the elucidation of this problem. extent, in^ the still unknown^ convergence reflex ### fibres. As a result of this the pupil may become Summary completely immobile. More often its response to 1. Fifteen patients with tonic pupils have been ### light is impaired and sluggish so that it may only studied The variability from case to case of the ### contract slowly on exposure to a strong source Of abnormal pupillary reflexes is stressed; no single ## illumination, whilst^ its^ contraction^ on^ convergence, combination^ can be regarded as typical. ## although slow, is^ more^ readily demonstrable.^ At 2. Two types of tonic pupil may be distinguished ### the' same time a delay in the destruction of acetyl- (a) the fixed type, and (b) the ordinary type of tonic