The anatomical basis of eye examinations Flashcards
snellen chart for visual acuity
if you fail on two letter on that line then the line before that is how you mark it
measures the global function of the eye
let them have glasses on
6metres away
If the patient reads the 6/6 line but gets more than 2 letters wrong, the previous line should be recorded as their acuity
If the patient cannot see the top line, reduce the distance to 3 and then 1 metres (record as 3/denominator or 1/denominator)
Then ask if they can count how many fingers you are holding up
Then ask if they can see gross hand movements
Then ask if they can detect light with a pen torch
Each line is labelled with the distance in metres it should be seen by a normally sighted eye
Acuity is recorded as a fraction – the distance from the chart is the numerator (number on top) and the furthest line seen as the denominator e.g. at 6 metres the patient can read to the 9 metre line = 6/9
Ask the patient to cover one eye and read the lowest line they are able to
Test acuity first with spectacles and then a pinhole if available
causes of decreased visual acuity
Visual acuity is a test of the optic nerve (cranial nerve II). Causes of decreased visual acuity include: Optic neuritis Lesions higher in the visual pathways Cataracts/corneal scarring Age-related macular degeneration
When you shine a light in one eye, both pupils constrict.
How does this happen?
Afferent (sensory) = Optic nerve (II) – projects to pretectal nucleus
Efferent (motor) = Oculomotor nerve (III) – projects from Edinger-Westphal nucleus to ciliary ganglion
funduscopy inspect what - whispering in ear
retina
gives indications about ICP - twiddle until you can see the retina
Assess for fundal reflex/red refex: look through the scope and shine the light at the patients eye about one arms length away. Look for a reddish reflection in the pupil = light reflecting back from the vascularised retina
Right eye of patient – hold ophthalmoscope in right hand
‘Whisper not kiss’ – be slightly to the patients side
Identify a blood vessel and follow this to the optic disc. Assess the four retina quadrants
Assess the macula – ask patient to look briefly directing into the light
what is a papilloedema
Papilloedema refers to optic disc swelling secondary to raised intracranial pressure. Optic disc margins appear blurred and small haemorrhages may be seen.
disc becomes indistinct and white
what might you see on hypertensive retinopathy
flame haemorrhage
hard exudates
papilloedema
cotton wool spots
absence of red reflex in children
congenital cataracts, retinoblastoma
absence of red reflex in adults
cataracts, vitreous haemorrhage, retinal detachment
Retinoscopy
Hand held instrument (retinoscope) projects a beam of light into the eye
The light is then moved around the back of the eye, which gives the examiner information about whether the patient has a refractive error and what type (short sightedness, long sightedness or astigmatism)
who is it useful for
Performed by optometrist
Useful for people who can’t communicate e.g. children or people with dementia
refraction test
what does this help test for
Helps to determine whether short/long-sighted or whether has astigmatism
Long-sightedness (hypermetropia/hyperopia) causes the light from distant objects to focus
how to correct
happens when older
behind the eye
requires convex lens
Short-sightedness (myopia) causes light from distant objects to focus
how to correct it
in front of the retina.
concave lens
Objects close to the eye can be focussed onto the retina.
what is astigmatism
In astigmatism, the eye is shaped more like a rugby ball than a football. This makes the light focus in more than one place in the eye. This can lead to headaches and vision. Astigmatism can often be associated with long or short-sightedness. This can be corrected with a lens.
what test measures the shape and curve of the cornea
Keratometry test
kernatoconus
cornea protrudes out looks like eye is a pyramid falling out
afrocaribbean people - corrected with glasses
bulls keratopthy
cysts in cornea
side effects of surgery to the eye
corneal scarring - viral infection like herpes
peripheral field vision test
what is normal
Peripheral vision is vision as it occurs outside the point of fixation, i.e. away from the centre of gaze.
Normal is 90-95 degrees temporal to central vision.
60-65 nasal
Several types of test:
Automated perimetry/tangent screen exam – occur at optometrist, use machinery/computers
Confrontational exam – sit opposite the patient and move hand in and out of peripheral vision – patient will tell you when they are able to see your fingers
for bipolar hemianopia, nasal hemianopia, homonymous hemianopia and left homonymous hemainopai with macula sparing
what test for this
peripheral field test
total one eye blinds is via a VA test
Intraocular pressure measurement
Measures the pressure created by the fluid in your eyes
Can be measured using a tonometer. Sends a puff of air into the eyes, causes reflex closure
Pressure measured by reaction and resistance to pressure from the puff of air
Can also use applanation tonometry (manual) instrument placed on eye – done with anaesthetic drops
slit lamp gives 3D view of eye - assess depth
keratitis
corneal abrasion
cataracts feature
Binocular microscope the provides a 3D view of the eye
Slit beam allows the anterior segment of the eye to be examined
Can use in ED to look for and remove foreign bodies or assess abrasions
keratitis
cause
ifnalmtion of cornea - herpes simplex dendritic ulcer
corneal abrasion
blue trauma pain redness and photophobia and lacrimiantion
cataracts feature
cloudy lens
corneal reflex
Protective reflex – stimulation of one cornea causes both eyes to blink. Sensory input trigeminal nerve (ophthalmic division, Va), motor response facial nerve
You are testing a 42-year-old female patient’s visual acuity using a Snellen Chart. On examination you deem her left eye normally sighted, but she only able to read at 6 metres what a normally sighted person would be able to read at 18 metres with her right eye. What level of visual acuity should this be recorded as?
Left eye 6/6, right eye 6/12 Left eye 6/6, right eye 6/18 Left eye 6/6, right eye 18/6 Left eye 6/12, right eye 6/6 Left eye 6/12, right eye 12/6
left eye 6/6 right eye 6/18
Acuity is recorded as a fraction – the distance from the chart is the numerator (number on top) and the furthest line seen as the denominator e.g. at 6 metres the patient can read to the 9 metre line = 6/9
You are testing a the pupillary reflexes of a patient you suspect has multiple sclerosis. When you shine a light into their left eye, both pupils constrict. You then move the light source to their right eye and both pupils dilate. When you move the light source back to the left eye, both pupils constrict again. Which of the following have you observed?
A normal response
Left-sided relative afferent pupillary defect
Left-sided relative efferent pupillary defect
Right-sided relative afferent pupillary defect
Right-sided relative efferent pupillary defect
right sided relative afferent pupillary defect
Afferent = sensory arm of the reflex (A = Arrives)
The normal response to light should be constriction. When the light is shone in the abnormal right eye, the pupils dilate instead of constrict, as if the light is not ther
You are spending the day shadowing the optometrist. You watch them carry out a retinoscopy test on 10-year-old girl who is non-verbal due to a learning disability. She has been referred from her school due to concerns about her eyesight. The optometrist shines the light at the back of the eye and moves it from side to side. They note that the red reflex moves along the back of the eye AGAINST movement.
Which refractive error is the optometrist now suspecting?
Astigmatism Hypermetropia Myopia No refractive error Presbyopia
myopia
The retinal reflex at the back of the eye should not move if there is no refractive error.
The retinal reflex will move IN THE DIRECTION OF MOTION if there is hypermetropia or presbyopia and will CHANGE ANGLE if there is astigmatism.
It will move AGAINST motion in myopia (short-sightedness).
Astigmatism (uh-STIG-muh-tiz-um) is a common and generally treatable imperfection in the curvature of the eye that causes blurred distance and near vision. - cornea
Presbyopia is the gradual loss of your eyes’ ability to focus on nearby objects- ageing
Question 4: You are examining a patient with a history of idiopathic intracranial hypertension who has come in with a severe headache. In the Emergency Department. Using a fundoscope, you look into the back of their eyes. You note blurring of the optic disc margins.
Which of the following conditions are you now concerned about?
Astigmatism Diabetic retinopathy Hypermetropia Myopia Raised intracranial pressure
RAISED ICP
Blurred optic disc margins demonstrates papilloedema, which is a sign of raised intracranial pressure.
Whilst shadowing an ophthalmologist for the day, they ask you if you know of any tests which might be helpful to measure intra-ocular pressure in glaucoma. You say…
Fundoscopy Keratometry Ocular tonometry Retinoscopy Slit lamp examination
ocular tonometry
Fundoscopy: used to look at the retina at the back of the eye. Useful in concerns about raised ICP and monitoring diabetic and hypertensive retinopathy
Keratometry: measurement of the shape of the cornea
Retinoscopy: used to assess for refractive error
Slit lamp examination: can look for corneal damage and/or foreign body in the eye.
driving standard sneellen chart
6/12
