neuro-ophthalamology Flashcards
How does the pupillary light reflex work?
The pupillary light reflex is initiated when light stimulates the optic nerve. Fibers from the optic nerve reach the pretectal nucleus in the midbrain, which then stimulates both Edinger-Westphal nuclei. These nuclei are responsible for the parasympathetic supply of the eye. Fibers travel with the oculomotor nerve to reach the ciliary ganglion, where they relay and then travel through the short ciliary nerves to the constrictor pupillae muscle, causing pupillary constriction.
What are the functions of the optic nerve and how can they be assessed?
The optic nerve is responsible for vision. Its functions can be assessed by measuring visual acuity, conducting color vision testing, examining the pupil, and performing visual field testing.
What aspects of the optic disc should be evaluated during a fundus examination?
When examining the optic disc, it is important to assess its size, shape, color, margins, cup, blood vessels, and the surrounding area.
What is a relative afferent pupillary defect and what causes it?
A relative afferent pupillary defect occurs in optic nerve lesions or extensive retinal lesions. It is characterized by the failure of the optic nerve to inform the pretectal nucleus about the presence of light.
What is Horner Syndrome and what are its clinical features?
Horner Syndrome is caused by interruption of the sympathetic supply of the eye. It can result from various conditions such as brain tumors, syringomyelia, Pancoast tumor of the lung, carotid artery dissection, and aneurysm. Clinical features include ptosis (partial), miosis, anhydrosis, enophthalmos, and flushing.
How is the parasympathetic supply of the eye regulated?
The parasympathetic supply of the eye starts from the Edinger-Westphal nucleus in the midbrain. Fibers relay in the ciliary ganglion and supply the constrictor pupillae and ciliary muscles.
What is Adie’s pupil and how is it diagnosed?
Adie’s pupil is a dilated pupil caused by inflammation of the ciliary ganglion or the short ciliary nerves, leading to a cut-off of parasympathetic supply to the eye. It is one of the causes of anisocoria. Diagnosis can be confirmed by using pilocarpine 0.125%, which causes constriction of the Adie’s pupil due to denervation hypersensitivity.
What is Argyll Robertson pupil and what conditions can cause it?
Argyll Robertson pupil is due to interruption of fibers in the area of the pretectal nucleus in the midbrain, which is responsible for the light reflex. It is associated with conditions such as neurosyphilis, demyelination, tumors, or hemorrhage.
How does the visual pathway work?
Both optic nerves travel to the cranial cavity and unite at the optic chiasm. Nasal fibers from both eyes decussate, while temporal fibers pass uncrossed to form the optic tract. The optic tract reaches the lateral geniculate body, and from there, the optic radiation arises, passing through both temporal and parietal lobes. The final destination is the primary visual cortex in the medial wall of the occipital lobe.
What visual field defects can occur based on the site of lesion along the visual pathway?
Lesions along the visual pathway can cause various visual field defects.
How is the sensory supply of the eye tested?
The ophthalmic nerve, which is the first branch of the trigeminal nerve, supplies sensation to the eye. Sensory supply can be tested by gently touching the eye with a cotton bud while the patient’s eyes are closed.
What muscles are responsible for eye motility and which cranial nerves supply them?
The motility of the eye is controlled by the four recti muscles (medial rectus, lateral rectus, superior rectus, and inferior rectus) and the two oblique muscles (superior oblique and inferior oblique). These muscles are supplied by the 3rd, 4th, and 6th cranial nerves.
What are the clinical features of nerve palsies affecting the eye muscles?
Nerve palsies affecting the eye muscles can occur due to various causes. The clinical features depend on the specific cranial nerve involved. For example, 6th nerve palsy is characterized by esotropia, 4th nerve palsy by hypertropia, and 3rd nerve palsy by ptosis and the eye being shifted down and out.
What is the role of the facial nerve in eye function?
The facial nerve supplies the orbicularis oculi muscle, which is responsible for closing the eyelids.Important Clinical Questions in Ophthalmology:
