Glaucoma

Question 1

I N T R O D U C T I O N

Answer 1

• Increases the pressure within the eye
• Causing damage to the back of the eye around the optic nerve
• Mainly damages the optic disk
• Often undiagnosed

Question 2

A E T I O L O G Y

Answer 2

• In a normal eye, ciliary body produces aqueous humour which is drained from the posterior chamber into the anterior chamber and then into the systemic circulation
• Supplies that part of the eye with many nutrients including antioxidants, vitamin C, sugars, ions
• Also maintains pressure in this part of the eye
• In an affected eye, there is a narrowing angle between the posterior and anterior chamber causing a blockage in the flow of the aqueous humour
• Causes an increased intra ocular pressure
• Open eye glaucoma is where there is partial blockage
• Results in optic nerve head damage and cupping of optic disk
• Causes loss of visual field
• Angle closure glaucoma more likely to cause blindness that open angle glaucoma
• Primary open angle Glaucoma is a medical emergency resulting in urgent reduction of IOP

Question 3

P O A G S Y M P T O M S

Answer 3

• Asymptomatic until damage has happened presenting as field loss
• Frequent screening for intra ocular pressure is required in diabetics
• For acute open angle – halos when looking in light, redness of the eye, cloudiness of the eye, blurred vision, pain, nausea and vomiting
• IOP raised up to double
• Visual field impaired – up to 50% axons lost, peripheral field progressively lost, central field late

Question 4

B E T A B L O C K I N G A G E N T S

Answer 4

• Reduce rate of production of aqueous humour to prevent increased intra ocular pressure
• Can be used orally but not often used due to side effects
• Betaxolol, Carteolol, Levobunolol, Timolol
• Systemic absorption may occur
• Contraindicated with bradycardia, heart block, uncontrolled heart failure and uncontrolled asthma
• Not to be used in asthma or COPD unless no alternative treatment, then use selective β blocker
• Interacts with verapamil
• Side effects – Ocular stinging, burning, pain, itching and erythema

Question 5

P R O S T A G L A N D I N A N A L O G U E S

Answer 5

• Increases uveoscleral outflow increasing aqueous humour drainage and reducing intraocular pressure
• Latanoprost, tafluprost, tavoprost and bimatoprost
• Licensed for use with β blocker
• Side effects – change eye colouration, increase in iris brown pigment, ocular irritation and pain, rash, dry eyes, headache, photophobia, darkening thickening and lengthening of eye lashes
• Caution in aphakia (absence of lens), pseudophakia, torn lens capsule and anterior chamber lens

Question 6

C A R B O N I C A N H Y D R A S E I N H I B I T O R S

Answer 6

• Reduce aqueous humour production
• Acetazolamide, Dorzolamide, Brinzolamide
• Important to monitor electrolytes in particular potassium
• May cause metabolic acidosis

Question 7

S Y M P A T H E T O M I M E T I C S

Answer 7

• Α adrenergic agonists – brimonidine and apraclonidine
• Decrease aqueous humour production and increase uveoscleral outflow
• Brimonidine is a selective α 2 adrenoreceptor agonist

Question 8

M I O T I C S

Answer 8

• Act by opening inefficient drainage channels in the trabecular network
• Pilocarpine – not commonly used in open angle glaucoma
• Short acting drug so need to be used four times a day
• Dark pigmented iris may need higher concentration and more frequent administration
• Side effects – blurred vision and headaches

Question 9

C O N T A C T L E N S E S

Answer 9

• Drug and preservative may accumulate in soft lenses
• Lenses should be removed before and during treatment
• Hard lenses may be worn