Understanding Open Angle Glaucoma

0:02[Applause]

0:03[Music]

0:10hi this is tom from zero2finals.com

0:12in this video i'm going to be going

0:14through open angle glaucoma

0:17and you can find written notes on this

0:18topic at zero to finals dot com slash

0:21open angle glaucoma or in the

0:23ophthalmology section

0:25of the zero to finals medicine book

0:28so let's jump straight in glaucoma

0:30refers to the

0:31optic nerve damage that's caused by a

0:35significant rise in

0:36intraocular pressure the intraocular

0:39pressure is essentially the pressure

0:41within the eye

0:43itself raised intraocular pressure is

0:46caused by a blockage

0:48in the aqueous humor trying to escape

0:50the eye

0:52and we'll talk more about the

0:53pathophysiology shortly

0:56there are two types of glaucoma open

0:59angle

1:00and closed angle and here we're going to

1:02be talking about

1:03open angle so let's talk about the basic

1:07anatomy and physiology because it's

1:10important to understand

1:12some basic anatomy and physiology of the

1:13eye and how the eye

1:15functions in order to understand the

1:17pathophysiology

1:19of glaucoma the vitreous

1:22chamber of the eye is filled with

1:24vitreous humor

1:26and this is the main bulk the main area

1:28of the eye

1:31the anterior chamber is between the

1:33cornea and the iris

1:36and the posterior chamber is between the

1:38lens and the iris

1:40these anterior and posterior chamber are

1:43filled with

1:44aqueous humor that supplies nutrients to

1:46the cornea and keeps it healthy

1:49the aqueous humor is produced by the

1:51ciliary body

1:52and then the aqueous humor flows around

1:55the iris

1:56from the posterior chamber into the

1:58anterior chamber

2:00where it drains through something called

2:02the trabecular

2:03meshwork at the angle between the cornea

2:06and the iris

2:09the aqueous humor flows from the ciliary

2:12body

2:13around the lens and under the iris

2:16through the anterior chamber through the

2:19trabecular meshwork and

2:20into something called the canal of

2:22schlem

2:23from the canal of slam it eventually

2:25enters the general circulation

2:28and is reabsorbed into the body the

2:30normal

2:31intraocular pressure is 10 to 21

2:35millimeters of mercury and this pressure

2:38is created by the resistance to flow

2:40through the trabecular meshwork so

2:43aqueous humor

2:44is trying to flow through the trabecular

2:47meshwork

2:48out of the eye and if there's more

2:51resistance in the trabecular meshwork

2:53the pressure will go up because there's

2:56more resistance

2:57of aqueous humor trying to escape the

2:59eye if there's less resistance

3:01the pressure will go down because the

3:03aqueous humor is able to flow more

3:05freely out of the eye

3:08so let's talk about the pathophysiology

3:10of open-angle glaucoma

3:11and in open-angle glaucoma there's a

3:13gradual

3:14increase in resistance through the

3:16trabecular meshwork

3:18and this makes it more difficult for

3:19aqueous humor to flow through the

3:21meshwork and

3:22exit the eye therefore the pressure

3:25slowly builds within the eye

3:27and this gives a slow and chronic onset

3:29of glaucoma so let's talk about the

3:32effects of the increased pressure in the

3:34eye

3:35and this causes cupping of the optic

3:37disc

3:40and remember in the center of a normal

3:42optic disc is something called the optic

3:44cup and this is a small indent in the

3:47optic disc

3:48and is usually less than half the size

3:50of the optic cup

3:51and when there's a raised intraocular

3:53pressure this

3:54indent becomes larger because the

3:56pressure in the eye puts pressure on

3:58that indent making it

4:00wider and deeper this is called cupping

4:04an optic cup greater than 0.5 the size

4:08of the optic disc

4:09is abnormal so if the optic cup is more

4:12than half the size

4:13of the optic disc this suggests

4:16cupping and could indicate glaucoma

4:20so what are the risk factors for open

4:22angle glaucoma or increasing

4:24age family history black ethnic origin

4:28and near-sightedness which is called

4:30myopia are all

4:32key risk factors to remember for your

4:34exams

4:36let's talk about the presentation of

4:37open angle glaucoma

4:39often the rise in intraocular pressure

4:41is asymptomatic for a long period of

4:44time

4:45it's usually diagnosed by routine

4:47screening when they attend an

4:48optometry appointment for an eye check

4:51so whenever you get your eyes checked at

4:52the optometrist

4:54they check the intraocular pressure to

4:57see whether there's any possibility

4:58you've developed glaucoma

5:00glaucoma tends to affect the peripheral

5:02vision first

5:04so there may be a gradual loss of

5:06peripheral vision

5:07as it closes in slowly and they

5:09experience something called tunnel

5:11vision

5:12it can also present with gradual onset

5:14of fluctuating pain

5:16headaches blurred vision and typically

5:20halos surrounding lights which are worse

5:22at night time

5:23so if a patient is losing their

5:25peripheral vision and at night time they

5:27see halos appearing around lights

5:30think about glaucoma

5:33so how can we measure intraocular

5:35pressure well there's two

5:37main ways we can measure the intraocular

5:39pressure the first is something called

5:41non-contact

5:42tonometry and this is commonly used with

5:45a machine

5:46to estimate the intraocular pressure

5:49when you go to an opticians

5:50and this involves shooting a puff of air

5:52at the cornea

5:54and measuring the corneal response to

5:56that puff of air

5:57if the cornea has a lot of pressure

5:59inside it from glaucoma

6:01it won't react very much when air is

6:04shot at it

6:05whereas if you've got a very soft cornea

6:07with a lack of

6:09intraocular pressure there'll be a large

6:11reaction to that puff of air

6:13this is a less accurate way of measuring

6:15the intraocular pressure

6:16but it gives a helpful estimate for

6:18general screening purposes

6:20the second way of measuring intraocular

6:22pressure is something called

6:23goldman applination tonometry

6:27this is the gold standard way of

6:29measuring the intraocular pressure

6:31this involves using a special device

6:33mounted on a slip lamp

6:34that actually makes contact with the

6:36cornea and applies different pressures

6:39to the front of the cornea to get an

6:40accurate measurement of the intraocular

6:42pressure

6:43so the machine actually presses down on

6:46the cornea

6:47to check how much resistance there is

6:50and indicate how much pressure there is

6:52within that cornea

6:55so how do we make a diagnosis of

6:57glaucoma well firstly

6:59using a goldman applination tonometry

7:02which can be used to check the

7:03intraocular pressure

7:04fundoscopy is used to assess

7:08the optic disc for cupping and also for

7:11optic nerve health

7:14visual field assessment is important to

7:16check for peripheral vision loss

7:18and all three of these will be useful

7:21for making the diagnosis

7:24so how do we manage open angle glaucoma

7:27management of glaucoma aims to reduce

7:29the intraocular pressure

7:31treatment is usually started at an

7:33intraocular pressure

7:34of 24 millimeters of mercury or above

7:37patients should be closely followed up

7:39to assess the response to treatment

7:41and treatment will be guided by an

7:43ophthalmologist

7:44the first line treatment is something

7:46called prostaglandin analogues

7:48used as eye drops and an example of this

7:51is

7:52latanoprost and these eye drops increase

7:55the uveo

7:56scleral outflow and the uv scleral

8:00outflow refers to the drainage of the

8:02aqueous humor from the anterior chamber

8:05into the anterior chamber angle

8:08rather than going through the

8:09traditional trabecular meshwork

8:12notable side effects from prostaglandin

8:14analog eye drops like litanoprost

8:17are eyelash growth eyelid pigmentation

8:21and iris pigmentation typically you get

8:24a browning of the iris

8:27the other options for treating open

8:29angle glaucoma are

8:30topical beta blockers like timolol

8:34which reduce the production of the

8:35aqueous humor

8:38carbonic anhydrase inhibitors like

8:40dorsolamide

8:41which reduce the production of the

8:43aqueous humor and

8:45sympanometics such as brimonidine

8:49which reduce the production of aqueous

8:51fluid and also

8:52increase the uv scleral outflow

8:55finally a surgical procedure called

8:58trabeculectomy may be used

9:00where the eye drops are ineffective this

9:02involves creating a new

9:03channel from the anterior chamber

9:06through the sclera

9:08to a location under the conjunctiva this

9:11causes a little bleb

9:13under the conjunctival where the aqueous

9:14humor drains

9:16and the aqueous humor is then reabsorbed

9:18from this bleb into the general

9:19circulation

9:20so it essentially creates a new way for

9:23aqueous humor to drain away from the eye

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