Conversely, parasympathetic stimulation causes contraction of the circular muscle and constriction of the pupil. Sympathetic stimulation of the adrenergic receptors causes the contraction of the radial muscle and subsequent dilation of the pupil. The sphincter is controlled by nerves of the parasympathetic nervous system, and the dilator by the sympathetic nervous system. There are two types of muscle that control the size of the iris: the iris sphincter, composed of circularly arranged muscle fibers, and the iris dilator, composed of radially arranged muscle fibers. ( August 2014) ( Learn how and when to remove this template message) Unsourced material may be challenged and removed. Please help improve this article by adding citations to reliable sources in this section. This section needs additional citations for verification. Anisocoria is the condition of one pupil being more dilated than the other. Both mydriasis and miosis can be physiological. The opposite, constriction of the pupil, is referred to as miosis. Mydriasis is frequently induced by drugs for certain ophthalmic examinations and procedures, particularly those requiring visual access to the retina.įixed, unilateral mydriasis could be a symptom of raised intracranial pressure. More generally, mydriasis also refers to the natural dilation of pupils, for instance in low light conditions or under sympathetic stimulation.
The excitation of the radial fibres of the iris which increases the pupillary aperture is referred to as a mydriasis. A mydriatic pupil will remain excessively large even in a bright environment. Normally, as part of the pupillary light reflex, the pupil dilates in the dark and constricts in the light to respectively improve vividity at night and to protect the retina from sunlight damage during the day. Non-physiological causes of mydriasis include disease, trauma, or the use of certain types of drug. Once these are systematically excluded, benign episodic unilateral mydriasis should be considered a possibility.Mydriasis is the dilation of the pupil, usually having a non-physiological cause, or sometimes a physiological pupillary response. 1 Adies pupil and trauma are other common causes. These pupils can be identified by their refusal to constrict with 1% Pilocarpine. 4 Pharmacological blockade is the most common cause of such a presentation. 1 We found only one report of an intracranial aneurysm causing internal ophthalmoplegia without extraocular muscle involvement. 3 In the absence of any other ocular abnormality, unilateral mydriasis is rarely due to an intracranial cause. A systematic approach is required to examine and investigate this condition. The cataracts in our patient were an incidental finding.Īnisocoria is often viewed as a worrying sign. 2 The dilated pupil is the only ocular finding. 2 The episodes may be accompanied by blurred vision, orbital pain, headache, or photosensitivity. The features of our patient were consistent with a rare but innocuous condition termed ‘benign episodic unilateral mydriasis.’ 2 The affected individuals, usually women, often have a history of migraine. Each time there were no other significant findings and pharmacological tests were negative. Three of these episodes were accompanied by headache and two by ocular pain. Over the next 2 years, this patient presented four times with similar episodes of unilateral mydriasis, twice affecting the left eye ( Figure 1b). The anisocoria spontaneously disappeared in 3 days. It was observed that 0.125% Pilocarpine did not constrict the pupil, whereas 1% Pilocarpine constricted both pupils well. There was no other ocular abnormality, except for the previously noted cataracts.
#Fixed dilated pupil differential diagnosis full
There was no ptosis and full ocular motility.
Her vision was unchanged from her last visit to the department. A detailed history revealed no trauma and no possibility of pharmacological dilation. Six months later, she was referred to us with a dilated left pupil. This was interpreted as an abnormally prolonged response to tropicamide drops. The right pupil, however, remained dilated ( Figure 1a). The abrasion healed in 2 days with vision improving to 6/18. Examination revealed bilateral congenital cataracts. Vision was 6/12 in the right eye and 6/36 in the left.
She was systemically well, except the occasional classical migraine. A 39-year-old lady presented to the casualty with a traumatic corneal abrasion to the left eye.
0 kommentar(er)
