{Practical 4...Pupils!}
Wednesday, February 10, 2010
Marcus Gunn pupil is also known as relative afferent pupillay defect. (RAPD)It was named after a Scottish opthalmologist, Robert Marcus Gunn, who was an excellent ocular surgeon and he introduced systematic teachings of eye disorders.
Marcus Gunn pupil is a medical sign observed during swinging flashlight test, and this pupillary defect generally occurs with significant optic nerve or retinal disease.
Test to perform on patients with Marcus Gunn pupil
1) Shine a long steady light into one eye, and quickly switching to another eye
2) Since light shone on one pupil will cuase both eyes to constrict, switching quickly from one eye to another will give an indication of the functioning of each eye.
3) To start with, check the direct reflex of one eye, constriction of that pupil is expected
4) Observe the fellow eye for consensual reflex, it should constrict as well.
5) Next, the pentorch would be held infront of the defected eye to observe for a direct response,
and it should be absent.
6) Observation for the unaffeced eye's consnsual reflex would still be present.
1) Shine a long steady light into one eye, and quickly switching to another eye
2) Since light shone on one pupil will cuase both eyes to constrict, switching quickly from one eye to another will give an indication of the functioning of each eye.
3) To start with, check the direct reflex of one eye, constriction of that pupil is expected
4) Observe the fellow eye for consensual reflex, it should constrict as well.
5) Next, the pentorch would be held infront of the defected eye to observe for a direct response,
and it should be absent.
6) Observation for the unaffeced eye's consnsual reflex would still be present.
This is a short testing guide video.
Conditions leading to RAPD
Optic Nerve disease
- Optic Neuritis -Very mild optic neuritis with minimal loss of vision can lead to strong RAPD
- Ischemia Optic neuropathies
- Glaucoma
- Optic Nerve Tumour
- Optic Nerve inflammations or Infections
- Optic atrophy
Retinal Causes
- Ischemic Retina Disease
- Retinal Detechment
- Severe Macular Degeneration
- Retinal Infection
However there are conditions that do not cause RAPD:
- Refractive error even to the extreme
- Cataract
- Cornea scar
- Conditions with Efferent Pupillary Defect. E.g. Adie's pupil, Horner's Syndrome
This is a picture of a young patient diagnoised with Marcus Gunn Pupillary Defect
Ocular Physiology Practical 4, 3:38 AM
Pupil is a circular opening
located in the centre of the
iris of the eye that controls
the amount of light
entering the eye.
