Term
| What is the effect of a lesion in the macula? |
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Definition
| Unilateral central scotoma with distortion. |
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Term
| What is the effect of a lesion in the peripheral retina eg. detachment |
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Definition
| Unilateral peripheral/ total. |
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Term
| What is the effect of a lesion in the optic nerve (acute)? |
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Definition
| Unilateral central scotoma. |
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Term
What is the effect of a lesion in the Optic Nerve (Chronic)
Eg Glaucoma, chronic papilloedema |
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Definition
Peripheral constriction (tunnel vision)
(also seen in functional visual loss) |
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Term
| What is the effect of a lesion in the chiasm? |
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Definition
| Bitemporal Hemianopia (Outer field loss in both eyes). |
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Term
| What is the effect of a lesion post chiasm |
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Definition
Loss of field opposite to site of lesion in both eyes
Eg left optic tract lesion causes inner field loss in left eye and outer field loss in right eye. |
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Term
| What is the pupil light reaction? |
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Definition
| When light is shone in one eye, both pupils constrict (direct and consensual). |
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Term
| What can cause total afferent pupil defect in one eye? |
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Definition
| Sectioned optic nerve or retina totally detached. |
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Term
| What would you observe in a patient with total afferent pupil defect in one eye? |
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Definition
-Both pupils the same at rest
-No constriction of affected eye
-Consensual response present
-When light moved from normal to affected eye both pupils dilate. |
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Term
| What does relative afferent pupil defect indicate? |
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Definition
| Widespread unilateral retinal or optic nerve pathology. |
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Term
| What is the main sign of an efferent pupil defect? |
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Definition
| Pupils are different sizes at rest. |
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Term
| What causes a failure of the pupil to constrict? |
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Definition
| Damage to the preganglionic nerve which travels from the midbrain to the orbit with the third nerve or the postganglionic nerve which travels from the ciliary ganglion to the eye. |
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Term
| What conditions are normally responsible for a failure of the pupil to constrict? |
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Definition
1) A compression of the preganglionic nerve by brain swelling or an aneurysm in the circle of willis
2) Damage as part of a third nerve palsy
3) A lesion of the ciliary ganglion.
4) Pathology of the pupil sphincter |
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Term
| What does damage to the sympathetic supply to the eye cause? |
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Definition
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Term
| What are the main symptoms of Horner's syndrome? |
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Definition
Failure of pupil dilation
Partial Ptosis (drooping of eyelid)
If preganglionic:
-Anhydrosis
(Failure to sweat on affected side)
-Absence of flushing
If congenital (or onset prior to 12 months):
-Iris heterochromia |
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Term
| What can cause Horner's syndrome? |
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Definition
Lesions:
1) Preganglionic from T1 to superior cervical ganglion
2) Postganglionic from SCG to eye via ICA via long posterior ciliary nerves
3) Pathology of the pupil dilator eg. uveitis |
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