Flashcards in Ophthalmology Deck (58)
When do cataracts occur ?
When the lens in the eye become cloudy and opaque. This reduces visual acuity by reducing the light that enters the eye.
What is the job of the lens ?
To focus light coming in to the eye on to the retina at the back of the eye.
What holds the lens in place ?
The suspensory ligaments attached to the ciliary body..
How does the lens focus ?
By contraction and relaxation of the ciliary body
What other function do the ciliary bodies have ?
Produce aqueous humour into the anterior chamber
What happens to the lens when the ciliary bodies contracts and relaxes ?
Contract = It releases tension on the suspensory ligaments and the lens thickens.
Relaxes = It increases tension in the suspensory ligaments and the lens narrows.
Fill in the blanks. The lens is nourished by the ___ fluid. It doesn't have a ___ supply. It ___ and ___ throughout life.
Surrounding fluid, blood supply, grows and develops.
When do congenital cataracts occur and how are the screened for ?
They occur before birth and are screening for using the red reflex during the neonatal examination.
Name 6 risk factors for cataracts ?
Are the symptoms in cataracts asymmetrical or symmetrical + why? Name 4 symptoms ?
Usually asymmetrical as both eyes are affected separately. It presents with:
-Very slow reduction in vision
-Progressive blurring of vision
-Change in colour vision with colours becoming more brown or yellow
-"Starbursts" can appear around lights, particularly at night time
Key sign for cataracts ?
Loss of the red reflex. The lens can appear grey or white when testing the red reflex. This might show up on photographs taken with a flash.
It is useful in exams to distinguish the causes of visual problems based on the symptoms. Cataracts cause a generalised reduction in visual acuity with starbursts around lights. Glaucoma causes a peripheral loss of vision with halos around lights. Macular degeneration causes a central loss of vision with a crooked or wavy appearance to straight lines.
Management of cataracts ?
If the symptoms are manageable no intervention may be necessary.
Cataracts surgery involves drilling and breaking the lens to pieces, removing the pieces and implanting an artificial lens into the eye. This is usually done as a day case under local anaesthetic. It generally gives good results.
It is worth noting that cataracts can prevent the detection of other pathology such as macular degeneration or diabetic retinopathy. Once cataract surgery is performed these conditions may be detected. Therefore, the surgery may treat the cataract but they may still have poor visual acuity due to other problems.
What is endopthalmitis, what causes it, how can it be treated and what can it lead to ?
It is a rare but serious complication of cataract surgery. It is inflammation of the inner contents of the eye, usually caused by infection. It can be treated with intravitreal antibiotics, injected directly into the eye. Endopthalmitis can lead to loss of vision and loss of the eye itself.
What is glaucoma ?
Optic nerve damage caused by a significant rise in intraocular pressure
What causes a raised intraocular pressure ?
A blockage in aqueous humour trying to escape the eye.
Pathophysiology of open angle glaucoma ?
There is a gradual increase in resistance through the trabecular meshwork. This makes it more difficult for aqueous humour to flow through the meshwork and exit the eye. Therefore, the pressure slowly builds within the eye and this gives a slow and chronic onset of glaucoma.
What is the optic cup ? Increased pressure in the eye causes cupping of the optic disc, what is this ?
In the centre of a normal optic disc is the optic cup. It is a small indent in the optic disc where there is no nerve fibres or blood vessels. It is usually less than half the size of the optic disc
When there is raised intraocular pressure the indent becomes larger as the pressure in the eye puts pressure on that indent making it wider and deeper. This is called "cupping". An optic cup greater than 0.5 the size of the optic disc is abnormal.
4 risk factors for open angle glaucoma ?
-Black ethnic origin
Presentation of open angle glaucoma ?
Often the rise in intraocular pressure is asymptomatic for a long period of time. It is diagnosed by routine screening when attending optometry for an eye check.
Glaucoma affects the peripheral vision first. Gradually the peripheral vision closes in until they experience tunnel vision.
It can present with a gradual onset of fluctuating pain, headaches, blurred vision and halos appearing around lights, particularly at night time.
Gold standard way to measure intraocular pressure ?
Goldmann applanation tonometry
Diagnosis of open angle glaucoma (three components) ?
-Goldmann applanation tonometry - can be used to check the intraocular pressure
-Fundoscopy - assessment to check for optic disc cupping and optic nerve health
-Visual field assessment - to check for peripheral vision
Management of glaucoma (include aims of management, first line, other options, any surgical options) ?
Management of glaucoma aims to reduce the IOP. Pts are followed up closely to assess the response to treatment.
Prostaglandin analogue eyedrops (e.g. latanoprost) are first line. These increase uveoscleral outflow.
-B blockers (e.g. timolol) reduce the production of a
-Carbonic anhydrase inhibitors (e.g. dorzolamide) reduce the production of aqueous humour
-Sympathomimetics (e.g. brimonidine) reduce the proportion of aqueous fluid and increase uveoscleral outflow
Trabeculectomy surgery may be required where eye drops are ineffective. This involves creating a new channel from the anterior chamber, through the sclera to a location under the conjunctiva. It causes a "bleb: under the conjunctiva where the aqueous humour drains. It is then reabsorbed from this bleb into the general circulation.
What is age related macular degeneration ?
A condition where there is degeneration in the macular that causes a progressive deterioration in vision.
Key finding associated with macular degeneration ?
Drusen seen during fundoscopy.
What are drusen ?
Yellow deposits of protein and lipids that appear between the retinal pigment epithelium and Buch's membrane. Normal drusen are small and hard. Larger and greater numbers of drusen can be an early sign of macular degeneration.
The macular is made of four key layers, what are these layers
At the bottom is the choroid layer which contains blood vessels that provide the blood supply to the macula. Above that is Buch's membrane. Above Buch's membrane there is the retinal pigment epithelium and above that are the photoreceptors.
What are the two types of age related macular degeneration ?
90% of cases are dry and 10% are wet. Wet AMD carries a worse prognosis.
Name 3 features of dry AMD ?
-Atrophy of the retinal pigment epithelium, choroid and retina
-The pt develops a central scotoma
-The pt retains good peripheral vision