PUPILS . . . CONT.
RELATIVE AFFERENT PUPILLARY DEFECT (RAPD) (see Neurology Chapter)
defect in visual afferent pathway anterior to optic chiasm
differential diagnosis: optic nerve compression, optic neuritis, large retinal detachment, CRAO, CRVO, advanced glaucoma
does not occur with media opacity e.g. corneal edema, cataracts
test: swinging flashlight
•if light is shone in the affected eye, direct and consensual response to light is decreased
•if light is shone in the unaffected eye, direct and consensual response to light is normal
•if the light is moved quickly from the unaffected eye to the affected eye, "paradoxical" dilation of both pupils occurs
•use ophtalmoscope with “+4” setting, using red reflex especially in patients with dark irides
Clinical Pearl
Even dense cataracts do not produce a relative afferent pupillary defect.
NEURO-OPHTHALMOLOGY
VISUAL FIELD DEFECTS (see Neurology Chapter)
lesions in the visual system have characteristic pattern losses
several tests used: confrontation (screening), tangent screen, Humphrey fields, Goldman perimetry
BITEMPORAL HEMIANOPSIA
a chiasmal lesion
Etiology
In children: craniopharyngioma
In middle aged: pituitary mass
In elderly: meningioma
HOMONYMOUS HEMIANOPSIA
a retrochiasmal lesion
the more congruent, the more posterior the lesion
check all hemiplegic patients for ipsilateral homonymous hemianopsia
e.g. left hemisphere ––> right visual field (VF) defect in both eyes
INTERNUCLEAR OPHTHALMOPLEGIA
commonly seen in multiple sclerosis (MS)
lesion of medial longitudinal fasciculus (MLF) (see Figure 5)
delayed movement in ipsilateral adducting eye
monocular nystagmus in contralateral abducting eye
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The MLF connects the Pontine Paramedian |
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Reticular Formation (PPRF) to the nucleus of |
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CN III contralaterally. When looking left, nerve |
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impulses originate in the right frontal cortex |
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Lateral Rectus |
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Medial Rectus |
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“Look left” |
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(not shown) and travel to the left PPRF. The |
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Muscle |
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Muscle |
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impulses then travel to the ipsilateral CN VI |
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nucleus and to the contralateral CN III nucleus |
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CN III |
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via the MLF. In INO, an MLF lesion inhibits |
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CN VI |
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transmission from the PPRF to the |
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PPRF |
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contralateral medial rectus muscle. |
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MLF |
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lateral gaze, in patient with ophthalmoplegia (INO)
NYSTAGMUS (see Otolaryngology Chapter)
definition: rapid, involuntary, small amplitude movements of the eyes that are rhythmic in nature
direction of nystagmus is defined by the rapid eye component of motion
can be categorized by movement type (pendular, jerking, rotatory, coarse) or as normal vs. pathological
Pendular Nystagmus
due to poor macular function or cerebellar lesioneye oscillates equally about a fixation point
may be present in people who become blind early in life
OP30 – Ophthalmology MCCQE 2002 Review Notes