glaucoma Flashcards
(41 cards)
what is galucoma?
is a group of eye diseases in which progressive damage to the optic nerve leads to impaired vision and, in a small proportion of people,
blindness.
what are the characteristics of visual field defects?
arcuate scotomas, nasal steps, and altitudinal
loss.
Changes to the head of the optic nerve — including pathological cupping
– Nerve fibre layer defects.
how can the head of the optic nerve become damaged?
combination of:
– IOP that is abnormally high — most common cause of damage.
– The blood supply to the optic nerve is compromised.
– There is a weakness in the optic nerve structure or fibres.
define suspected glaucoma
is defined as changes in the optic
nerve head (optic disc) or visual field that suggest glaucomatous damage (regardless of the intraocular pressure).
what is ocular hypertension?
Ocular hypertension is a condition defined by consistently or recurrently elevated intraocular pressure (greater than 21 mmHg) and no signs of glaucoma.
what is the purpose of the aqueous humour?
the fluid created by the ciliary body in the posterior chamber
what is the anterior chamber angle?
The space between the iris and pupil
behind and the cornea in front is called the anterior chamber. The anterior chamber angle is the structure formed where the iris and the cornea join the sclera (white of the eye) towards the outside of the eye.
what is the purpose of the intraocular pressure?
Keeps the eye in the shape of a globe.
how is the IOP maintained?
by the balance between production and outflow of aqueous humour.
what can raised IOP cause?
an cause glaucoma by damaging the optic nerve.
– Intraocular pressure is normally around 10–21 mmHg, but it can be as high as 70 mmHg in acute angle closure glaucoma.
how do drugs used to treat glaucoma work?
either reduce the production of aqueous humour, or increase its outflow.
what are the 4 ways of characterising glaucoma?
- Age of onset: congenital, infantile, juvenile, or adult.
- Rate of onset: acute or chronic.
- Cause: Primary (no known cause)
Secondary – causes include disease, drugs,
developmental disorders (increase in IOP) - Mechanism: Angle closure glaucoma v Open angle glaucoma.
what is angle closure glaucoma?
the angle between the iris and the cornea is at least partially closed.
what is the purpose of angle closure glaucoma?
This blocks the trabecular meshwork and
prevents drainage of intraocular fluid.
– As intraocular fluid continues to be
produced, the pressure within the eye
increases and the optic nerve is damaged.
Onset can be acute or chronic
what is open angle glaucoma?
the angle between the iris and the cornea is open.
– Onset is usually insidious, and the course
chronic.
– Both eyes usually affected - signs of damage
may be worse in one eye.
– IOP is usually increased but can be within
normal range
what is the prognosis of chronic open angle glaucoma without treatment?
- Will usually be asymptomatic until late in its
course — visual field defects do not appear until most of the optic nerve fibres have been lost.
what is the prognosis of open angle glaucoma with treatment?
- Most people with chronic open angle glaucoma will not go blind, although they
will have some visual field defects.
what is the prognosis for acute angle closure glaucoma?
Full recovery is likely for people
treated promptly Irreversible loss of vision is
more likely if there is:
* Delay in presenting for treatment.
* Delay in reducing intraocular
pressure to the normal range.
* Inability to maintain intraocular pressure within the normal range.
how will patients with acute ACG present?
acute painful red eye
* Blurred vision
* Headaches or eye pain associated with nausea and seeing halos around lights; these symptoms typically occur in the evening and are relieved by sleeping.
* Use of adrenergic drugs (eg. phenylephrine) or an antimuscarinic drugs (eg. TCA’s)
* Semi-dilated and fixed pupil.
* Tender, hard eye.
what is emergency management of acute ACG?
– One drop of pilocarpine 2% in blue eyes/ pilocarpine 4% in brown eyes
– Followed by a single dose of oral acetazolamide 500 mg
what is the management of acute ACG in secondary care?
Topical and IV drugs to reduce intra-occular pressure and analgesia.
– Definitive treatment is surgery (often laser surgery) to allow aqueous humour to flow from the posterior chamber into the anterior chamber.
what are the risk factors for Chronic OAG?
- Raised intraocular pressure -the main treatable risk factor for chronic
open angle glaucoma - Age - prevalence increases steeply with age.
- Family history - risk is increased when a first-degree relative has
glaucoma. - Ethnicity - more common in people of black African origin
- Corticosteroids - The use of oral, inhaled, or high-potency topical
corticosteroids has been associated with increased risk of glaucoma
…………….corticosteroids increase the resistance to outflow of the aqueous
humour………Most common with eye drop preparations! - Myopia - People who are short-sighted are more likely to develop
glaucoma and more likely to develop it at a younger age; the risk increases
with severity of myopia - Diabetes mellitus
how do you manage chronic OAG?
treatment based on the
person’s age, IOP, and central corneal thickness.
– Offer a topical prostaglandin analogue to people with IOP of 24 mmHg or more if they are at risk of visual impairment within their lifetime
what is the treatment for early/moderate COAG?
where treatment is indicated - a topical prostaglandin analogue is
recommended first line.
