EYE DISORDERS Flashcards
introduction
2 sections : the anterior segment (back) and the posterior segment (front)
the anterior segment : filled with clear watery fluid
the posterior segment: filled with a dense jelly called aqueous humour
AQ HUMOUR - nourishes the areas around the iris and cornea
maintains pressure so that the eye keeps its shape (intraocular pressure)
intraocular pressure
if the pressure in the back of the eye is high the pressure in the AQ humour causes pressure in the front of the eye too - this can damage the back of the eye and the optic nerve
its imported the aq humour at the front of the eye is well drained - there are drainage systems in the anterior of the eye to do this
ITS IMPORTANT TO KEEP THE CORNEA HYDRATED IT KEEPS THE LENSE CLEASR AND SUPLE - if it dyes up then it puts pressure on the back of the eye damaging the optic nerve
ocular hypertension (OHT)
some people can have raised intraocular pressure
where there is no optic disc damage
no loss of vision
this can be treated in the same way you would treat open angle glaucoma
SOMETIMES RASIED INTRAOCULAR PRESSURE DOESNT NEED TO BE TREATED - if there is no significant risk of a person developing glaucoma
- if at risk get measured by an optometrist
GLAUCOMA:
2 MAIN CATEGORIES :
open angle glaucoma :
progresses at a slower rate
patient may not realise they have lost significant vision until the disease has progressed quite far
chronic may be symptomless - no pain in the eye and raised intraocular pressure
closed angle glaucoma :
can appear suddenly and is painful visual loss that can progress quickly
the pain and discomfort normally causes patients to seek medical attention before permanent damage occurs
acute onset - patient can start to fell very ill
painful red eye - MEDICAL EMERGENCY
it is a group of disorders:
main features -
raised interocular pressure (IOP)
Visual field loss - this is when we start diagnosing glaucoma
Aetiology
intraocular pressure : blockage inside creating pressure and can cause significant damage
there is a balance between the production of AQ humor and the drainage of the fluid
there can be issues caused when the fluid is not drained puts pressure on the back of the eye
YOU NEED A BALANCE OF DRAINAGE AND PRODUCTION
normal IOP for people not at risk is 16-21mmHg
people at risk
high intraocular pressure (IOP): age over 40 Afro-Caribbean family members who have had the disease Farsighted/nearsighted Diabetes long term use of corticosteroid previous eye injury
risk factors :
people who have diabetes mellitus - can have both types of glaucoma
age
genetics - can pass down generations without knowing
Myopia- (short sighted) : high risk of glaucoma
race - BAME community is higher risk
Aqueous Humour flow
if its produced at the back of the eye it is pushed to the front of the eye then is drained out
it is important that the angles are open so that the fluid come out and is drained into the canal
it is important that the cillary body which is partially responsible for creating the AQ fluid flows through the pupil into the anterior chamber and then leaves via the drainage canal
TRABECULAR MESHWORK - where the fluid drains out
just behind the open drainage angle
Open and Closed Glaucoma
open angle glaucoma :
clogging of the trabecular meshwork
the angle between the iris and cornea is open but fluid cant drain out
closed angle glaucoma : complete closure of the trabecular meshwork
POAG - primary open angle glaucoma:
most common and is frequently an inherited condition
drainage canals become blocked over time - usually between months and years
no early symptoms - THE MOST IMPORTANT SYMPTOMS : THE DEVELOPMENT OF BLINDSPOTS OR PATCHES OF VISION LOSS OVER MONTHS OR DECADES
aetiology - POAG
occurs in the absence of any abnormality in the structure of the anterior chamber or the filtration angle
reduce outflow due to increase resistance in the trabecular meshwork or schlems canal
signs and symptoms - POAG
no symptoms until its quite advanced - main signs happen when u go to an optometrist
Asymptomatic initially
headaches may occur
raised IOP (only one of the symptoms)
optic disk cupping
progressive loss of peripheral vision - may eventually lead to blindness
usually bilateral (in both eyes)
Aims of treatment and disease management
aims of treatment :
prevent significant loss of sight
lower IOP
minimal side effects
disease management :
reduce the formation of AQ fluid
reduce the inflow of AQ fluid
increase. outflow of AQ fluid
Treatment of POAG
- decrease AQ production :
beta blockers
carbonic anhydrase inhibitors
alpha- adrenergetic agonists
2.increase outflow (either uveoscleral or trabecular)
alpha- adrenergetic agonists
Prostaglandin analogues
Cholinergenic drugs
drug with the least side effects should be given - best way to do this is with the use of topical treatments
Prostaglandin analogues
NORMALLY FIRST LINE TREATMENT FOR POAG
latanoprost ,travoprost, tafluprost - formulated in eye drops
Bimatoprost is a prostamide (similar in action to traditional PGAs)- increases AQ fluid outflow a bit better via the uveoscleral route and the trabecular route
increase AQ fluid outflow
most powerful topical hypotensive’s- reduce IOP by 25%-30%
well tolerated
can be administered one daily
Prostaglandin analogues
SIDE EFFECTS AND CONTRAINDICATIONS
side effects : Lengthening and thickening of eyelashes irritation pigmentation of the iris (not reversible !!) eye redness (hyperaemia)
Contraindications :
PMH Herpes Keratis
allergens to ingredients
Pregnancy/breastfeeding
aqueous humor reduction
topical beta blockers : timolol, carteolol
carbonic Anhydrase inhibitors : dorzolamide, brinzolomide
topical beta blockers : timolol, carteolol
carbonic Anhydrase inhibitors : dorzolamide, brinzolomide
reduce IOP by 20-30%
inhibit beta mediated production of AQ humor by the cilary epithelium
timolol- previously GOLD standard treatment
can be used with prostaglandin analogues
