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11.3:
Eyes
In the
IHS Classification of Headache, separate categories are given to
headache associated with acute glaucoma (11.3.1), refractive errors
(11.3.2), and heterophoria or heterotropia (latent or manifest squint)
(11.3.3). The comment is made that uncorrected refractive errors and
heterophoria may cause headaches, but their importance is widely
overestimated. However, ocular disease clearly causes headache and pain
in and around the eyes. This section is meant to describe these
conditions.
Ocular
and Retrobulbar Pain Associated With Ocular Disease
The
response of a patient to an intrinsic or extrinsic ocular lesion that
causes the symptom of pain is infinitely varied as is the description of
the pain itself. Nevertheless, clinical ocular and orbital conditions
associated with pain in the eye may be grouped according to the anatomic
site of the lesion (Hitchings, 1980). These sites and their associated
conditions include: (1) the cornea--erosion, foreign body, ulcer,
bullous keratopathy; (2) the sclera--scleritis; (3) the iris--iritis,
miotics, iridectomy, photocoagulation, anterior segment ischemia, acute
angle closure glaucoma; (4) the ciliary body--photocoagulation; (5) the
retina and choroid--photocoagulation, extreme glare; (6) the optic
nerve--optic neuritis; and (7) the orbit--inflammation, tumors, injury.
In addition to the discussion that follows, the reader may be interested
in the reviews of this subject by Behrens (1976, 1978).
The
sensation of pain may result from direct stimulation of pain nerve
endings or from excessive stimulation of sensory terminals that usually
transmit other sensations.
The
extensive network of sensory nerves that innervate the cornea and sclera
is described in detail elsewhere. Bergmanson (1977) studied denervation
within the monkey eye after section of the ophthalmic division of the
trigeminal nerve. He found minimal evidence for sensory innervation of
the choroid and little innervation of the iris. The ciliary muscle had
no sensory nerves, but the ciliary body adjacent to the base of the iris
and the trabecular meshwork had a rich sensory plexus. Bergmanson was
unable to identify specific sensory nerve terminals from the sections
that he studied; however, there did not appear to be any proprioceptors.
Thus, sensations carded by the plexus could include pain, temperature,
and tactile stimulation.
The
sensation of pain can be generated by direct mechanical stimulation or
by a combination of one or more of the following: tissue distortion,
vasodilation, heat perception, and chemoreceptor awareness of
inflammatory products that affect sensory terminals.
The
nature and severity of pain produced by extrinsic or intrinsic ocular
diseases vary depending on the region of the eye being damaged and the
underlying cause.
Cornea
and Sclera
Superficial
Corneal Disease
Mechanical
stimulation after loss (foreign body, erosion, ulceration) or disease (bullous
keratopathy) of corneal epithelium produces directly a sensation of
pain. The pain from a corneal foreign body, abrasion, or disease of the
external portions of the eye producing irritation of the conjunctiva and
cornea is so characteristic as to be described as a foreign body
sensation. It differs entirely from the deep seated neuralgic pain of
iritis or iridocyclitis. The pain from a corneal foreign body or
abrasion is accompanied by profuse lacrimation, photophobia,
conjunctival injection, blepharospasm, and radiation of pain to the
forehead. Foreign body sensation is not referred to the cornea but
instead is routinely interpreted as a localized scratching sensation
beneath the upper lid (Burton, 1981). Experimental evidence by several
groups of investigators (Bill et al., 1979; Nicholl et al., 1980)
suggests that after direct pain has occurred, subsequent antidromic
impulses cause release of substance P, a polypeptide that
consists of 11 amino acids, from the iris, resulting in inflammation and
further pain. This experimental evidence is in agreement with the
clinical observation that severe ocular pain with miosis and anterior
chamber ``inflammation'' may follow delayed healing of a corneal
erosion.
Limbal
Disease
Inflammation
affecting either the cornea or sclera will cause pain through tissue
distortion, vasodilation, and stimulation of chemoreceptors.
Posterior
Scleritis
There
is little direct sensory innervation of the posterior sclera. The pain
from posterior scleritis may occur from direct involvement of the short
posterior ciliary nerves or from inflammation of adjacent extraocular
muscles or orbital structures.
Iris
Iritis
The
pain of anterior uveitis can be severe, but is usually less overwhelming
than that of acute angle closure glaucoma (see below). It is frequently
widespread in its reference, and patients may complain of earache, pain
in the teeth, or pain over one of the sinuses. It is usually described
as throbbing or neuralgic in character, and is often associated with
photophobia that may be severe enough to overshadow other aspects of the
pain. Excessive lacrimation and blepharospasm are frequently observed.
The eye is likely to be tender upon palpation. According to Burton
(1981), the deep, throbbing pain is always worse at night and in the
early morning hours. Breakdown of the blood-aqueous barrier probably
allows a release of kinins and prostaglandin E1 from
polymorphonuclear leucocytes, while substance P and other
polypeptides (together with prostaglandin E2) are
released from the iris itself. These chemicals are believed to stimulate
chemoreceptors in the ciliary body nerve plexus and may also cause
miosis (Cole and Unger, 1973; Unger et al., 1974).
Mechanical
Stimulation
Manipulation
of the iris during an iridectomy causes pain by tugging at the root of
the iris rather than by cutting iris tissue. In addition, pulling on the
iris root and iris prolapse also cause inflammation and further pain.
Photocoagulation (laser) burns generate heat and will cause pain if the
duration of the burn is long. Although burns of short duration (2---3 µsec)
do not generate sufficient heat to produce pain, they may set up a shock
wave that produces an ill-defined sensation that has been described as
``like a blow'' (Unger et al., 1977).
Chemical
Stimulation
Ocular
pain after the instillation of pilocarpine is associated with but is
probably not caused by iris sphincter or ciliary spasm. The most likely
cause of this pain is traction of the ciliary muscle on the scleral spur
with distortion of the adjacent ciliary plexus.
Acute
Angle Closure Glaucoma
Severe
head pain localized within and around the involved eye is the symptom
that most often draws attention to the presence of acute angle closure
glaucoma. However, many patients are seen in whom the associated pain is
minimal, vague, and variable in location. Teeth have been extracted and
presumed sinus infections treated with antibiotics because of
misinterpretation of pain actually arising from a glaucomatous eye. At
the other end of the clinical spectrum is the patient whose pain is
excruciating and directly localized to the orbit. Such pain is
unremitting, and may or may not have a pulsatile quality. The associated
symptoms of nausea, vomiting, and abdominal pain can be attributed to
spread of pain impulses from trigeminal nuclei to other brainstem
nuclei. Severity of the nausea and vomiting, the degree of prostration,
and the patient's inability to cooperate during history taking and
physical examination may result in unnecessary laparotomy. Fortunately,
most patients are able to indicate the eyeball itself as the source of
the pain. Many patients describe aching as the essential quality of
their pain. We have seen three patients with intermittent angle closure
glaucoma who were referred with the diagnosis of migraine. Indeed, the
history of pain was suggestive of migraine; however, slit lamp
biomicroscopy confirmed the presence of occludable anterior chamber
angles, and the correct diagnosis was made. Patients with acute angle
closure glaucoma also complain of visual loss during the episode. We
have examined two patients whose combination of episodic visual loss
associated with pain were initially interpreted as ``painful amaurosis
fugax.'' One of these patients had already undergone cerebral
arteriography, and the other was scheduled for a complete
cerebrovascular disease evaluation when the correct diagnosis became
evident (see also Ravits and Seybold, 1984).
The
pain that occurs in acute angle closure glaucoma may be caused by the
associated intraocular inflammation. Whether elevation of intraocular
pressure alone can cause pain is less clear. Certainly, chronic
elevation of intraocular pressure may persist for years without
symptoms.
Ciliary
Body
Photocoagulation
of the ciliary processes is usually painless although prolonged
photocoagulation of the iris root may be quite painful.
Retina
and Choroid
Short
duration photocoagulation may be painful depending upon the instrument
used. Argon laser photocoagulation is usually painless, while krypton
laser photocoagulation may cause some pain.
Optic
Nerve
About
80% of patients with optic neuritis experience tenderness of the globe
or pain on eye movement (Perkin and Rose, 1979; McDonald, 1980). The
pain may be described as a sharp or a dull, aching sensation. It may
occur prior to, coincident with, or following the onset of visual
dysfunction. It has been suggested by Rose (1972) that the pain of optic
neuritis occurs from distention of the optic nerve sheath with
irritation of its trigeminal sensory fibers. That the optic nerve is
indeed swollen has been confirmed by ultrasonography (Coleman and
Carroll, 1972) and by computed tomography (Howard et al., 1980).
Orbit
Inflammation
Inflammatory
orbital conditions such as orbital cellulitis, orbital pseudotumor, and
extension of sinusitis are generally associated with moderate to severe
pain, presumably from involvement of the major trigeminal sensory
nerves.
Tumors
As a
general rule, neoplasms that involve the orbit are not painful; however,
when pain is present, the tumors are likely to be malignant (Grinberg
and Levy, 1974; Jones et al., 1979; McDonald, 1980; Trobe et al., 1982).
Tumors that spread to the orbit from the paranasal sinuses are usually
associated with late pain. In some cases, however, pain may be the
earliest sign of a tumor involving the orbital apex and cavernous sinus.
The pain is severe, continuous, and associated with facial dysesthesia.
It has been described as chronic, burning, and intermittently stabbing,
and it involves one or more divisions of the trigeminal nerve. When this
type of pain is present, it is evidence of intraneural infiltration by
neoplastic cells, usually from basal cell, squamous cell, or
nasopharyngeal carcinoma (Jefferson, 1953; Ballantyne et al., 1963;
Moore et al., 1976; Trobe et al., 1982). When the pain is combined with
involvement of one or more ocular motor nerves, it confidently predicts
neural infiltration within the cavernous sinus (Mohs and Lathrop, 1952;
Willis, 1952; Ballantyne et al., 1963; Moore et al., 1976; Unsöld et
al., 1980; Trobe et al., 1982).
The
differential diagnosis of painful ophthalmoplegic migraine with cranio-orbital
lesions is shown in Table 3.
Trauma
Non-neoplastic
proliferation of neural tissue may occur in the orbit after injury or
surgery, producing severe pain (Biette, 1900; Lohlein, 1910; Bäbel and
Valerio, 1945; Blodi 1949; Wolter and Benz, 1964; Johnson et al., 1966;
Jakobiec and Jones, 1979; Sutula and Weiter, 1980; Folberg et al.,
1981). These ``amputation neuromas'' represent abortive regenerative
attempts on the part of severed nerves. In such lesions, the connective
tissue components of the nerve--endoneurium, perineurium, and Schwann
cells--all proliferate. Axon cylinders elongate, branch, and ramify from
the proximal to the distal portion of the nerve (Hogan and Zimmerman,
1962; Henderson, 1973). Removal of the offending structure is usually
followed by prompt relief of pain.
Postoperative
Pain
Pain
that occurs after ocular surgery is not infrequent, and ocular surgical
procedures including cyclocryotherapy, circular buckling for retinal
reattachment, or evisceration, may cause severe and persistent pain that
is not relieved even by the more potent analgesics. Michels and Maumenee
(1973) recommended postoperative administration of retrobulbar alcohol
in seeing eyes to prevent unnecessary suffering. Ticho et al. (1980)
have obtained excellent pain relief with subcutaneous electric
stimulation using a portable, battery-operated apparatus, while Jolson
(1982) has advocated transcutaneous electric nerve stimulation for
ocular pain control. These systems apparently act through stimulation of
endogenous opiates. Finally, selective percutaneous radiofrequency
thermocoagulation of the trigeminal ganglion has been used to treat some
patients with chronic ocular pain with good success and no serious
complications (Rosenberg et al., 1981).
Ocular
and Retrobulbar Pain Without Ocular or Orbital Disease
The
complaint of mild, localized intraocular retrobulbar pain when no
obvious corneal, intraocular, or orbital disease exists is a common
problem to ophthalmologists as well as to internists, neurologists, and
neurosurgeons. Many of the patients who seek ophthalmologic consultation
for such pains are middle aged women. In many cases, the symptoms seem
to be magnified by the patient's unfounded anxiety regarding the
possibility of glaucoma, impending blindness, or brain tumor.
Occasionally, such pains are mentioned as an afterthought by the patient
who came only for a routine ophthalmologic examination and for the
prescription of glasses. Some patients are able to give a rather precise
description of their pain while others are vague and have difficulty
conveying any accurate impression of their discomfort. Some describe
stabbing pains, others dull continuous pain, and others a feeling of
pressure in their eye. We have been impressed with the rarity of
positive findings when these patients are fully evaluated. Only rarely
has it been possible to find any plausible ocular, orbital, or
intracranial explanation. Now and then an obvious lacrimal insufficiency
as indicated by a Schirmer's test seems to be responsible. Desiccation
of the cornea and minor epithelial change may initiate the symptoms that
some patients describe as pain. Relief of symptoms with the use of
various tear replacement solutions or ointments seems to support the
diagnosis but by no means establishes its validity.
Patients
with cervical arthritis may complain of ocular pain. This pain may
originate from the upper cervical nerve roots from whence it is referred
to the eye. Conceivably, some of these pains could arise from other
structures innervated by the ophthalmic nerve (nasal mucosa, orbital
vessels, or the intracranial dura), but proof of the source is rarely
possible. Exhaustive radiologic studies and consultation with other
specialists are seldom required as they are rarely of help. A
sympathetic, reassuring physician and routine analgesics are, in most
cases, all that the patient requires.
Lansche
(1964) described a type of pain for which he suggested the term ophthalmodynia
periodica. This pain is an intermittent, single stab or jab of
local, ocular pain that strikes without warning and often causes the
patient to quickly place a hand over the involved eye. The pain leaves
as quickly as it comes and causes no tearing or nasal stuffiness. A
second pain may immediately follow the first, but rarely is there a
third or a fourth. The pain may not recur for weeks or months; however,
some patients have a series of attacks and then are free of symptoms for
long periods. Lansche (1964) had no plausible explanation for these
apparently genuine symptoms, although transient ischemic pain from an
embolus is an interesting possibility.
Bilateral
ocular or retrobulbar aching and tenderness is a common finding
associated with the so-called tension headache.
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