open angle glaucoma

Question 1

what is glaucoma?

Answer 1

• refers to the optic nerve damage that is caused by significant rise in intraocular pressure
• the raised intra ocular pressure is caused by a blockage in aqueous humour trying to escape the eye
• there are two types of glaucoma: open angle and closed angle

Question 2

what does aqueous humour do?

Answer 2

-provides a transparent and colourless medium between the cornea and lens that bathes and nourishes the lens and maintains the pressure within the eye

Question 3

what are the two types of glaucoma?

Answer 3

• closed angle

- open angle

Question 4

what part of the eye is filled with vitreous humour?

Answer 4

-the vitreous chamber

Question 5

what part of the eye is filled with aqueous humour?

Answer 5

-the anterior chamber of the eye between the cornea and iris and the posterior chamber between the lens and the iris

Question 6

what produces aqueous humour?

Answer 6

-ciliary body

Question 7

where does the aqueous humour travel?

Answer 7

• produces in the ciliary body, travels around the lens and the iris, through the anterior chamber, through the trabecular meshwork and into the canal of Schlemm
• from the canal of Schlemm it eventually rejoins the general circulation

Question 8

what is the normal intra ocular pressure?

Answer 8

10-21mmHg

Question 9

what causes the intra ocular pressure in the eye?

Answer 9

-the pressure is created as the aqueous humour travels from the trabecular meshwork to the canal of scheme

Question 10

what is the pathophysiology of open angle glaucoma?

Answer 10

• 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 pressure slowly builds within the eye and this gives a slow and chronic onset of glaucoma

Question 11

what is the pathophysiology of an acute angle closure glaucoma?

Answer 11

• the iris bulges forward ad seals of the trabecular meshwork from the anterior chamber preventing aqueous humour from being able to drain away
• this leads to a continual build up of pressure

THIS IS AN OPTHALMIC EMERGENCY!!

Question 12

what does the increased pressure in the eye do to the cup in glaucoma?

Answer 12

• it causes cupping

- this is when the cup in the optic disc increases in size

Question 13

what are risk factors for open angle glaucoma?

Answer 13

• increase in age
• family history
• black ethnic origin
• near sightedness (myopia)

Question 14

how does open angle glaucoma present?

Answer 14

• often is asymptomatic for a long time
• affects peripheral vision first, gradually patents will lose peripheral vision until they are experiencing tunnel vision
• headache
• gradual onset o fluctuating pain
• headaches
• blurred vision
• halos appearing around lights, especially at night time

Question 15

what is the gold standard test for measuring intra ocular pressure?

Answer 15

• goldmann applanation tanometry
• this involves a special device mounted on a slit lamp that makes contact with the cornea and applies different pressure to the from of the cornea to get an accurate measure of intraocular pressure

Question 16

what investigations are done to test for open angle glaucoma?

Answer 16

• Goldmann applanation tanometry (to check intraocular pressure)
• Fundoscopy (will show cupping)
• visual field assessment (will show peripheral vision loss)

Question 17

what is the management of open angle glaucoma?

Answer 17

• aim is to reduce intraocular pressure
• Prostaglandin analogue eye drops (e.g. latanoprost) = FIRST LINE
• BB (timolol)
• carbonic anhydrase inhibitors (e.g. dorzolamide)
• sympathomimetics (e.g. brimonidine)

Trabeculectomy surgery may be required if drops are innefective