Clinical Skills 3 - C - Snellen Chart, Pupillary, accomodation and swinging light examination Flashcards
Visual actuity is known as the sharpness of vision What is an eye chart that can be used to measure visual acuity.?
Snellen chart
If patient cannot see any of the letters on the snellen chart what is done? What is the final test?
Get patient to move 1m closer to the snellen chat at a time and reasses if they can read the numbers If not at one metre, check ability to see fingers and then hands and finally light
The snellen chart is used to understand how good an individual’s visual actuity is What does a A visual acuity measurement of 6/60 mean?
that a person with 6/60 vision who is 6 feet from an eye chart sees what a person with unimpaired (or 6/6) vision can see from 60 feet away. they see from 6 metres what a person with unimpaired vision can see from 60 metres
What is a score of 6/6 mean?
A score of 6/6 means 20/20 vision
Say a person could read the final line of the snellen chart ie their measuremnt was 6/5, what would this mean?
6/5 means a person can see from 6 metres what a person with unimpaired vision can see from 5 metres (their vision is better than normal)
What distances are the snellen chart visual acuity measured from?
Measured form 3 metres or 6metres
What snellen chart score classifies as blindness in the eye?
Visual acuity of less than 3 / 60 with a full visual field.
When checking the pupillary reflex, what is the afferent and what is the efferent nerve fibres? (for both pupillary reflex to light and darK)
The afferent nerve fibres are the optic nerve The efferent is the parasympathetic division of the oculomotor nerve for sphincter pupillae or The sympathetic ganglion travelling on the oculomotor nerve for dilator pupillae
For the pupillary light reflex, you shine a light in eg the right eye What is the right eye known as here and what is the left eye known as?
The eye the light is shone in - right eye Right eye - direct reflex Left eye - consensual reflex
Why is it when testing the pupillary light reflex it is carried out by shining the light at the eye from below and not directly in front of the eye? When shining the pen light into the eye what do you have to be careful of?
Shone from below so as to not activate the accomodation reflex Be careful that the pen light does not cross over into the consensual eye therefore not testing the proper efferent response
What is the accomodation reflex?
This is where the pupil size constricts in response to looking at a close object s as to stop the image from being blurry Lens also becomes more spherical and eyes medially rotate
In the pupillary light reflex, due to the testing of both the direct and consensual eye Is this consensual eye constriction testing of the afferent or efferent response?
This is testing the efferent
Optic nerve pathology can arise at the retina or the optic nerve Require gross retinal pathology to affect the afferent impulses What could be the pathology affecting the retina or optic nerve?
Retinal detachment Optic nerve compression
What test is carried out to find if their is a relevant afferent pupillary efect?
The swinging light test
Describe normal finding in the swinging light reflex? and describe pathological findings?
Normally, each illuminated pupil promptly becomes constricted. The opposite pupil also constricts consensually. When the optic nerve is damaged, the sensory (afferent) stimulus sent to the midbrain is reduced. The pupil, responding less vigorously, dilates from its prior constricted state when the light is moved away from the unaffected eye and towards the affected eye.
