Opthalomology Flashcards
What is amblyopia ?
Neurodevelopmental visual disorder with unilateral (less commonly bilateral) reduction of visual acuity
COMMON IN CHILDREN
What is amblyopia most commonly caused by?
strabismus
What is strabismus?
Eye alignment problems - ocular misalignment in one or BOTH the eyes
What are the 6 types of strabismus?
what are the two overall classes of strabismus ?
Heterotropia - deviation apparent if patient using both eyes (esotropia if crossed eye) and Exotropia if wall eyed) Hypertropia (upwards) Hypotropia (downwards)
Accomadative esotropia (eyes turned inward due to the effort of trying to accomadate to focus far sighted eyes Pseudostrabismus (appearance of esotropia due to prominant epicanthal folds esp. asians
Paralytic and Non paralytic:
Concomitant strabimus = Non Paralytic
deviation same no matter gaze position
Usually congenital or child onset due to sensory depreviation
Incomitant strabismus = Paralytic
Usually Nerve Palsy or Extra Ocular muscular disease (3,4 and 6th nerve palsy
Deviation varies when parient shifts gaze.
Heterophoria (latent deviation)
Deviation apparent when patient is using ONE eye deviation established by cover test (i.e. deviated when using one eye)
What is diagnosis assessment for strabismus (2)
Hirschberg test (corneal light reflex)
Cover test (assessing for deviation)
What is Hirschberg test ?
test for ocular alignment. Also known as corneal light reflex test.
how to perfrom hirschprings test
Use a light source, such as a penlight or finhoff transilluminator.
Instruct the patient to focus their gaze on your light source.
From a distance of 2 feet, shine your light source equally into the patient’s eyes at midline.
Observe the reflection of light off the cornea, which should appear as a pin-point white light near the center of the pupil in each eye.
In Esotropia (inward deviation) light source is displaced outwardly.
In Exotropia (outward deviation) light source displaced inwardly
In Hypertropia (upward deviation) light source is displaced down
In hypotropia(downward deviaiton) (light source is displaced up)
How to perform cover test –>
it is used to determine if a phoria (i.e. latent strabismus) is present.
- examiner occludes one eye for 1-2 seconds, then removes it. The eye that was previously occluded in observed (the one being tested for Heterophoria) for refixation movement (striaght looking) to re-establish sensory fusion with other eye.
What do you do with child who is diagnosed with strabismus?
PROMPT referral to opthalmologist, treatment may include :
glasses (for accomadative esotropia)
Opthalmic surgery
Accomodative Esotropia : What is this ?
Important to determine between long sightedness and whether they have a strabismus.
if a child islong sightedand needs to accommodate to see better, this can cause their eyes to turn in too much towards one another and they may go on to develop a convergentsquint(esotropia). Having glasses to correct theirlong sightednessallows their focusing to relax and give clearer vision
What is a refractive error? What are the 4 most common types?
Shape of lens does not bend light correctly, resulting in a blurred image. Main types of refractive errors are myopia, hyperopia, presbyopia and astigmatism
What is used to test for a refractive error?
Pin Hole Test
What will the pin hole show with refractive errors?
If reduced vision is caused by refractive error, a pinhole will cause improvement in visual acuity.
Vitreous what is it ?
The vitreous is the gel-like fluid that fills your eye. It’s full of tiny fibers that attach to your retina (the light-sensitive layer of tissue at the back of the eye)
Macula: What is it ?
macula is about 5mm across, and is part of the retina. Reponsible for main central vision, most of colour vision and fine details, with high concentration of photoreceptor cells - cells that see light
how often do diabetics get retinal screen ?
Two yearly (can be increased frequency)
What is the 5 main reasons diabetics cannot see?
- Blood sugar leading to osmotic effect changing shape of their lens = causing a refractive error
2nd commonest: Cataracts (over time)
RETINOPATHYS
3rd= Vitreous Hamorrhage (suddenly)
4th Macular Degeneration/blockage of retinal artery/vein
5th Optic nerve disease/Ischaemia of optic nerve
Diabetic Retinopathys: What are the 4 types?
- Background Retinopathy
- Diabetic Maculopathy
- Proliferative and Pre-proliferative
diabetic retinopathy - Advanced diabetic eye disease
Background retinopathy : What is this ?
commonest set of changes that reflect anatomical changes to vessels. Vision is usually normal
What is treatment for background retinopathy?
generally no ocular management
However when will background retinopathy need treatment ?
Unexplained decrease in visual acuity.
If not improved by pinhole (which would indicate a refractive error) refer as may be macula oedema
Rapid progression of background changes refer
Hard exudates close to the macula (refer)
Background Retinopathy 4 things that occur:
What does vision tend to be like?
Micro-anuerysms
haemorrhages
Hard exudates
Retinal oedema
Vision tends to be normal
Which of the 4 background retinopathy tends to cause symptoms and what should you do ?
Fluid leakage causing oedema that causes retinal dysfunction. Patients will only have symptoms if it tends to affect the macula and they will present with poor visual acuity that is not improved by pinhole test. REFER
Diabetic Maculopathy: What is pathophysiology?
2 types + clinical signs
What specifically happens to vision ?
Dsyfunction of macula that is caused by vessel dysfunction:
They may Transudate or exudate cuasing oedema (invisible to see but cause poor VA
They may Leak and form hard exudates which often form a ring
leakage can be localised or diffuse
Some can be caused by vessel ischaemia:
Clinically VA is poor, less exudates and more haemorrhages
What will dysfunction of the macula cause ?
CEntral vision loss (impaired reading) but retain peripheral visual field (impt for navigation)
What is visual acuity ?
Measure of how well small details are resolved in the centre of visual field, does not indicate how larger patterns are visualised, and therfore ALONE cannot determine quality of visual function
What are the clinical signs of maculopathy?
Microanuerysms, hard exudates +/- poor VA if oedema is present
Treatment of two types of diabetic maculopathy:
Control of BP, glucose and renal function.
- Leakage of vessels = improved with lasers +/- Avastin
- Vessel ischamia: Laser does not help
What is avastatin ?
it is an Anti-VEGF drug that decreases leakage, decrease oedema.
Pre Proliferative REtinopathy
They have background retinopathy that puts them at high risk, cotton wool spots, numerous blot haemorrhages, vessel dilation
What is treatment for pre-proliferative retinoapthy?
None except monitoring closeles
Proliferative retinoapthy pathophysiology:
When enough retinal capillaries close (over 25% of retina) resultant ischemia cuases formation of new blood vessels to attempt to re-oxygenate the tissues like grnualation tissue in MI.
Where are the two places in proliferative retinopathy that the new vessels grow due to ischamia?
- either peripheral if ischamia is sectioned
2. grow at optic disc if the ischamia is widespread = POOR prognosis
What is the problem with the new vessels in proliferative retinopathy ?
Leak protein
Haemorrhage esaily
Induce scarring which causes retinal detachment
are patients symptomatic or unsymptomatic inproliferative retinopathy ?
Unsymptomatic until there is bleeding or detachment i.e. Present at a late stage unless detected by screening.
What is treatment for proliferative retinopathy?
Treated by: BP control Blood glucose controlled Inject anti vascular endoethelial growth factor drug (VGEF) = AVASTIN LASER
What is used to diagnose ischamic maculopathy?
Fluorescein angiography :
Where dye does not normally escape from normal retinal vessels but it does in disease. Photos taken to assess the vascular state of the retina and choroid.
What are other common causes of visual impairments in diabetics?
refractive error (changes with blood glucose) Glaucoma Vitreous Haemorrhage Retinal Detachment Cataracts
Concomitant vs Incomitant (e.g. Non Paralytic vs paralytic strabismus) which will present with diplopia?
Diplopia only present in paralytic Incomitant strabismusm (3,4,6 nerve)
what are the two types of gluacoma?
Open angle
Closed angle
What is the critical ratio of optic disc?
0.7
what is the optic disc?
represents the beginning of the optic nerve and is the point where the axons of retinal ganglion cells come together . “physiological blind spot”
where is the “blind spot” of the eye ?
blind spot is the small portion of the visual field of each eye that corresponds to position of the optic disc.
What is the optic cup?
The optic disc has a center portion called the “cup” which is normally quite small in comparison to the entire optic disc. Optic cup contains nothing . Tissue arround optic cup is the axons
If the optic cup is LARGER what does this mean?
Larger optic cup means = LESS axons = axonal loss = glaucoma
In Gluacoma, what is the number of axons reflected in ?
Ratio of vertical size of cup compared to the vertical diameter of the optic disc.
Gluacoma is associated with a cup/disc ratio of 0.7 or more “cupping”
What is normal cup/disc ratio ?
0.6 or less
What is pathophysiology of acute closed angle glaucoma
this is where the angle formed by the cornea and the iris narrows, blocking the aqueous humour from draining the eye, leading to increased intra-ocular pressure.
What is the treatment of closed angle glaucoma?
IV acetazolamide
What is the definitive treatment of closed angle glaucoma?
Laser peripheral iridotomy: cuts holes in the tissue rather than just burning.
Laser iridoplasty: ring of laser burns is applied to iris peripherally, causing contraction of tissue - pulls peripheral iris away from drainage angle.
How many classes of license ?
6 classes
Test both eyes open, must see 6/12
What is ptosis ?
abnormally low position of the upper eyelid
Causes of Ptosis: Above tentorium
Third Nerve Causes
Nueromuscular Junction
Above tentorium = drugs of any kind
Third Nerve Causes: any causes aneurysm/brain tumour etc
Neuromuscular Junction : Myasthenia Gravis
Muscle disorders: Muscular Dystrophy/Multiple Sclerosis
Senile Ptosis (Levator dehiscence ptosis, the tendon of the muscle that lifts the eyelid (the levator palpebrae) may loosen or detach from its point of insertion.)
Heavy lid (stye/oedema)
eyelid ptosis: two muscles
Levator palprabrae under third nerve
Meuller (sympathetic control) from the sympathetic nerve plexus
Ptosis and constriction is sign of ?
Horners syndrome
Causes of ACUTE Horners Syndrome
More chronic?
NECK TRAUAM Sporting Activities resulting in wrenching of neck WHICH CAUSES BRUIT OF CAROTID
- vascular
CHRONIC: Pancoast tumour
Minimum eyesight requirements for normal driving:
6/12 with both eyes open and 140 degrees of visual field with both eyes open
what is macular degeneration
loss of photoreceptor density in the macula (caused by age)
what are the two types of macular degeneration ?
Atrophic (dry)
Exudative (wet)
What is presentation of atrophic age related macular degeneration
gradual painless loss of central vision
What is giant cell arteritis?
Large vessel vasculitis that affects temporal artery and
Leads to infarction of the optic nerve = leads to
What are the investigations of temporal arteritis ?
ESR often >60mm.
Temporal artery biopsy +ve > 50%
What is the treatment for temporal arteritis
Oral Steroids
Cataracts big three:
Age, diabetes, smoking
Causes of Cataracts: Surgical Sieve:
Endocrine: Galactosaemia: congential catarracts
Autoimmune: Juvenilie Arhtirtis : catarcts
Muscular: Myotonic Dystrophy Cataracts
Viral: Rubella cataracts
Genetics: Downs
