Intro to Opthalmology Flashcards
Anatomy of the eye
Emmetropia is the refractive state of an eye in which parallel rays of light entering the eye are focused on the retina, creating an image that is perceived as crisp and in focus. Myopia, hyperopia, and astigmatism are abnormalities of this desired condition.
In an emmetropic eye the light should come to focus on the macula which is the centre of the retina.
Refractive errors
In people with refractive erroes, either long-sightedness or short-sightedness. The images come into focus either in front of the retina such as in myopia (short sight) or hypertropia (long sightedness) where a short eyeball causes the images to come into focus behind the retina.
Think of the eye as being in the eye socket or orbit:
6 muscles
7 orbital bones
Extraocular muscles
Any misalignment of the visual axis will lead to double vision in adults when good vision has been obtained in each eye.
If the visual axis is misaligned in a child this will lead to suppression of the second image, one lazy eye.
Inflammation in the eye socket:
Will lead to bulging of the eye and possibly compression of the optic nerve. Similarly a tumour in a bony box=proptosis/exopthalmos
On the other hand, what happens with an orbital fracture?
=This leads to in sinking-enophthalmos of the eye and sometimes eye movement restriction if the extra ocular eye muscles are trapped.
In this case-cant look up with left eye as IR is trapped.
Embryology of the eye:
Facial development happens 4-8 weeks of development of the embryo. If things don’t fuse according to plan it can lead to varying clefting syndromes.
The optic vesicle develops as an outpouching of the forebrain from about 4 weeks onwards and tends to invaginate to a form which looks like the eyeball and similarly the structures of the eye form alongside it. Any disturbance of this process will lead to colobomas
The optic vesicle develops as an outpouching of the forebrain from about 4 weeks onwards and tends to invaginate to a form which looks like the eyeball and similarly the structures of the eye form alongside it. Any disturbance of this process will lead to…
…colobomas
Given that the fusion line is inferior, these leads to the typical colobomas defects in the iris and in the retina.
Visual milestones-newborns
So best toy for a child isnt a flully animal but actually a chessboard since they can actually see it
Visual milestones-5 to 8 months
9 months-1 year
The crucial first 7 years
If this process is disrupted in the first 7 years, often irreversible lazy eye (s) can result, which cannot be remedied later on.
Blindness definition
Blindness is the inability to see. The leading causes of chronic blindness include cataract, glaucoma, age-related macular degeneration, corneal opacities, diabetic retinopathy, trachoma, and eye conditions in children (e.g. caused by vitamin A deficiency). Age-related blindness is increasing throughout the world, as is blindness due to uncontrolled diabetes. On the other hand, blindness caused by infection is decreasing, as a result of public health action. Three-quarters of all blindness can be prevented or treated.
There are four levels of visual function:
1 normal vision
2 moderate visual impairment
3 severe visual impairment
4 blindness
Most common cause of visual impairment:
=cataract and not having the correct glasses
Cataract is also most common cause of blindness
Causes of blindness
Globally, the leading causes of blindness, in order of frequency, are:
- cataract (a clouding of the lens of the eye that impedes the passage of light),
- uncorrected refractive errors (near-sightedness, far-sightedness or astigmatism),
- glaucoma (a group of diseases that result in damage of the optic nerve),
- age-related macular degeneration (which involves the loss of a person’s central field of vision).
Other major causes include corneal opacities (eye diseases that scar the cornea), diabetic retinopathy (associated with diabetes), blinding trachoma, and eye conditions in children such as cataract, retinopathy of prematurity (an eye disorder of premature infants), and vitamin A deficiency
Trachoma:
Slippery slope to blindness
Strategy: SAFE
Surgery-to rotate the eyelashes out so they don’t wear away at the eye
Antibiotics to treat the infection
Facewashing
Education and environment
Visual impairment in our community
Significant impact on qol and comorbidities
Age related macular degeneration
The retina which is the light sensitive film of the eye develops changes which affects vision and bleeding and scarring happens as a result.
In wet type, the visual loss is accelerated.
Age Related macular degeneration (AMD)
‘Dry’ and ‘wet’ .1/3 of those over 75y will have dry AMD changes 2.2% of UK population >65y is blind in 1 or both eyes from AMD. Treatment options: Anti VEGF treatments via intravitreal injections
Wet AMD:
Prevention of wet AMD
Wet AMD treatment options
-Anti-vascular endothelial growth factors which can stabilise the vision in 95%
How is the treatment for wet AMD given?
- The injection is given directly inside the eyeball through the pars plana (safe place)
What does the treatment for wet AMD do?
It reverses the changes. See bleeding and exudation on left and on right changes have been reversed.
Another condition which causes bleeding in the back of the eye is…
…diabetic retinopathy
National service framework
What is diabetic retinopathy?
Diabetic Retinopathy is a microvascular complication of diabetes. The severity is due to the duration and control of diabetes. All patients over the age of 12 have to attend annual screening and are referred to the eye department if the disease exceeds nationally set criteria. Treatment is with laser, a destructive modality which can control progression but cannot restore vision.
Glaucoma-another leading cause of blindness
Glaucoma
A progressive optic neuropathy characterized by typical optic disc changes and commensurate visual field deficits. Blind registration statistics (? Bias)Ireland: Glaucoma accounts for 16% of blind Prevalence and incidence studies2% population over 50 yrs Incidence 0.2% per year 5-10% go blind Overall UK prevalence approx. 1-2 %Up to 75 patients per GPs list Only 50% of glaucoma patients diagnosed. The principle of screening: glaucoma is more common in certain well defined groups Intraocular pressure is a risk factor for glaucoma Ocular hypertension = ↑ IOP - optic neuropathy1/3 of patients with open angle glaucoma have normal IOP (Normal Tension Glaucoma)Lowering IOP is mainstay of treatment. This is usually achieved with eyedrops and sometimes with laser and surgery
Glaucoma epidemiology
Glaucoma is generally associated with a
raised intraocular pressure
but some people can have normal so complex
Prevelance higher in non-white populations
The idea is that intraocular pressure builds up in the eye because of problems with outflow and this has an effect on the nerve at the back of the eye. So imagine the optic nerve is like a donut and with progressive glaucoma, this gets erroded from the inside and the nerve becomes bigger and bigger to an end stage where there is only a thin rim of neural tissue left.
Glaucoma optic disks
What’s another way to monitor and diagnose glaucoma?
=To look at visual fields
By plotting the visual fields you can demonstrate the characteristic visual field losses to reflect how the nerve fibres enter the optic nerve of these arcuate defects shwon on back of card.
All patients with glaucoma are monitored using…
=optic nerve head imaging so you can plot the changes over time (visual field plotting as well as pressure and thickness)
Thyroid eye disease
TED pathophysiology:
-Most common in patients with Graves’ hyperthyroidism
This causes adipogenesis as well as hyluron deposition in the muscles, this leads to swelling in the orbit
TED treatment:
Diagnosing TED:
-MDT is needed especially endocrinologists and opthalmologists
EYE is down and out, observe pupil which is fixed and dilated.
Third nerve runs alongside the posterior communicating artery, and an aneurysm in this area can cause a non pupil staring third nerve palsy. So if seen in casulty dont send to eye doctors, they need urgent neurosurgical attention.
What does she have?
=life threatening emergency
