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
aqueous humor reduction
SIDE EFFECTS AND CONTRAINDICATIONS
contraindications of topical beta blockers :
some people have had significant bradycardia - significant heart blockage or uncontrolled heat failure
caution when using with asthmatics
side effects : Ocular side effects- corneal anaesthesia dryness burning and itching Uveitis systemic side effects possible
carbonic anhydrase inhibitors
Selectively inhibits carbonic anhydrase
reduce the production of AQ humor
reduces production of bicarbonate required for AQ fluid formation
dorzolamide, brinzolomide = topical inhibitors
acetazolamide : oral or intravenous for use in eye emergencies
carbonic anhydrase inhibitors
SIDE EFFECTS
derived from sulphonamides- cautions in known hypersensitivity
local reactions : burning irritation Conjunctivitis eyelid dermatitis
systemic side effects:
hypokalaemia
drowsiness
paraesthesia
Sympathomimetics and Parasympathomimetics
Sympathomimetics:
non selective - stimulate alpha and beta receptors
Dipiverfrin (prodrug of adrenaline)- rarely used
selective - alpha 2 receptor agonist Brimonidine and apraclonidine
reduce AQ fluid production
increase uvsceleral outflow
SIDE EFFECTS : red eye , stinging , blurring of vision
Parasympathomimetics :
pilocarpine (quick acting drug)
stimulates the cilary muscle which opens the trabecular meshwork thus enhancing outflow
unpopular due to side effects and frequency of administration (4-6 drops daily)
RARELY USED- LAST RESORT
NICE Guidelines
1st line = prostaglandin Analogue (PGA)
2nd line = PGA and Beta blocker
3rd line = PGA and Beta blocker + carbonic anhydrase inhibitor (CAI)
4th line = PGA and Beta blocker + carbonic anhydrase inhibitor (CAI) + brimonidine or use to replace CAI
after all these treatments have been tried then the last option is surgery
the evidence for pharmacology
good evidence to show that lowering IOP with pharmacological intervention (NICE,SIGN AND THE EUROPEAN GLAUCOMA SOCIETY)
Mono-therapy with PGAs first choice (NICE,SIGN AND THE EUROPEAN GLAUCOMA SOCIETY)
mixed results in trials : choice of drugs within a class (NICE Guidelines
MEDICINES OPTIMISATIONS :
awareness of drug therapies and the evidence
monitoring for side effects
Recognising allergies
improving adherence :
correct usage and administration
compliance aids
use of combination drops
the role preservatives : ocular surface disease
pressing the tear duct - avoid systemic absorption
timing of drops :leave at least 5mins between drops
expiry dates
use of topicals steroids : eye drops, nasal sprays, inhalers (monitor use)
people with co-morbidities of the eye (cataracts, diabetic retino-therapy)
ocular side effects of drugs
alternative treatments (trabeculectomy)
patient support - NICE Guidelines
personalised care plan : sign-positing to optometrists and community services including social workers
patient information
DVLA
emphasise the importance of regular eye tests for all individulas
at all times consider language and communication support needs :
people with english as a second language
those with a learning disability/conjunctive impairments
people with visual loss receive good quality accessible information throughout their patient journey
acute closed angle glaucoma
affects 0-1% of 40yr olds +
female:male ratio = 4:!
eye emergency - requires immediate treatment
Abrupt onset
structural defect
caused by a narrow angle between the iris and the cornea
acute closed angle glaucoma
AETIOLOGY
anatomy of the eye predisposes to ACAG
Restricted flow of the aq humor through the pupil (PUPIL BLOCK)
increase pressure behind the iris
isis pushes forward and blocks trabecular meshwork
acute closed angle glaucoma
SYMPTOMS
suddens serve painful red eyes
blurred vision
halo’s around lights
+/- nausea or vomiting
headaches
if not treated you can loose vision in 1-3hrs and become blind
MEDICAL EMERGENCY - patient is prepared for surgery to reduce IOP
acute closed angle glaucoma
TREATMENT
acetazolamide oral or IV - rapidly reduces formation of aqueous humor
short term treatment
laser iriclotomy/surgical iridoctomy to enable drainage via the trabecular meshwork
