Understanding Open Angle Glaucoma

Summary

This video by Zero to Finals covers open-angle glaucoma, a condition caused by increased intraocular pressure leading to optic nerve damage. The presenter explains the anatomy and physiology of the eye, focusing on the flow of aqueous humor and its role in maintaining eye pressure. The video discusses the causes, symptoms, and diagnosis of open-angle glaucoma, highlighting risk factors like age, family history, and myopia. Treatments include eye drops, beta blockers, and surgical procedures, aiming to reduce pressure and prevent further vision loss.

Takeaways

• 📈 Glaucoma refers to optic nerve damage caused by increased intraocular pressure.
• 👁️ Open-angle glaucoma involves a gradual increase in resistance through the trabecular meshwork, causing a slow rise in eye pressure.
• 💡 The aqueous humor flows from the ciliary body through the anterior chamber and drains via the trabecular meshwork into the canal of Schlemm.
• 🔍 Normal intraocular pressure ranges from 10 to 21 mmHg, and higher pressures indicate increased resistance to aqueous humor flow.
• 👓 Risk factors for open-angle glaucoma include age, family history, black ethnic origin, and nearsightedness (myopia).
• 👁️‍🗨️ Open-angle glaucoma often presents without symptoms but can lead to gradual peripheral vision loss, tunnel vision, and night-time halos around lights.
• 🩺 Two common methods to measure intraocular pressure include non-contact tonometry (air puff test) and Goldman applanation tonometry (more accurate).
• 🔬 Diagnosis of glaucoma involves checking intraocular pressure, optic disc cupping, and visual field assessment for peripheral vision loss.
• 💧 First-line treatment involves prostaglandin analogs like latanoprost, which increase the outflow of aqueous humor and reduce pressure.
• 🔧 Surgery, such as trabeculectomy, may be needed when eye drops are ineffective, creating a new drainage channel for aqueous humor.

Q & A

What is glaucoma, and how is it related to intraocular pressure?

Glaucoma refers to optic nerve damage caused by a significant rise in intraocular pressure (IOP). Elevated IOP occurs due to a blockage in the drainage of aqueous humor from the eye, leading to increased pressure.

What are the two main types of glaucoma, and which type is discussed in the video?

The two main types of glaucoma are open-angle and closed-angle glaucoma. The video focuses on open-angle glaucoma, where the resistance to the outflow of aqueous humor through the trabecular meshwork increases gradually.

How does aqueous humor flow through the eye, and how is it related to intraocular pressure?

Aqueous humor is produced by the ciliary body, flows from the posterior chamber to the anterior chamber, and drains through the trabecular meshwork into the canal of Schlemm. Resistance to this outflow creates intraocular pressure; if the resistance increases, the IOP rises.

What is the normal range of intraocular pressure, and what happens when this pressure increases in open-angle glaucoma?

The normal intraocular pressure is between 10 to 21 mmHg. In open-angle glaucoma, increased resistance in the trabecular meshwork leads to a gradual rise in pressure, causing damage to the optic nerve over time.

What is optic disc cupping, and how is it associated with glaucoma?

Optic disc cupping occurs when raised intraocular pressure causes the optic cup (a small indent in the optic disc) to become larger and deeper. An optic cup greater than 0.5 the size of the optic disc is considered abnormal and may indicate glaucoma.

What are the key risk factors for developing open-angle glaucoma?

Risk factors for open-angle glaucoma include increasing age, family history of glaucoma, black ethnic origin, and myopia (nearsightedness).

How does open-angle glaucoma typically present, and what are the common symptoms?

Open-angle glaucoma often presents asymptomatically, with a gradual loss of peripheral vision (tunnel vision), fluctuating pain, headaches, blurred vision, and halos around lights, especially at night.

What are the methods used to measure intraocular pressure, and how do they work?

Intraocular pressure is measured using non-contact tonometry, which estimates IOP by shooting a puff of air at the cornea, and Goldmann applanation tonometry, the gold standard, which applies pressure to the cornea to get an accurate measurement.

How is open-angle glaucoma diagnosed?

Diagnosis involves measuring intraocular pressure with Goldmann applanation tonometry, assessing optic disc cupping through fundoscopy, and checking for peripheral vision loss using visual field tests.

What are the treatment options for managing open-angle glaucoma?

Treatment aims to reduce intraocular pressure. First-line treatment includes prostaglandin analogs like latanoprost, which increase uveoscleral outflow. Other options include beta blockers, carbonic anhydrase inhibitors, sympathomimetics, and surgical procedures like trabeculectomy if eye drops are ineffective.

Outlines

00:00

👁️ Introduction to Open-Angle Glaucoma

Tom from Zero2Finals introduces open-angle glaucoma, explaining that it's caused by damage to the optic nerve due to a rise in intraocular pressure. The blockage of aqueous humor within the eye increases pressure, leading to glaucoma. He briefly outlines the types of glaucoma—open and closed angle—before diving into the basic anatomy and physiology of the eye, focusing on the aqueous humor's production and flow. The trabecular meshwork, the resistance it creates, and its role in regulating intraocular pressure are also explained.

05:01

🧠 Pathophysiology and Effects of Open-Angle Glaucoma

Tom explains that open-angle glaucoma develops gradually due to increased resistance in the trabecular meshwork, resulting in a slow buildup of intraocular pressure. This chronic pressure leads to cupping of the optic disc, where the optic cup expands due to pressure, indicating glaucoma if it exceeds half the size of the optic disc. Risk factors include age, family history, black ethnic origin, and myopia. He notes that early stages of the disease are often asymptomatic and detected during routine eye exams, with peripheral vision being affected first.

10:02

👓 Symptoms and Diagnosis of Open-Angle Glaucoma

Tom describes the symptoms of open-angle glaucoma, which include gradual peripheral vision loss, tunnel vision, fluctuating pain, headaches, and halos around lights, especially at night. He explains two methods to measure intraocular pressure: non-contact tonometry (using a puff of air) and Goldman applanation tonometry (the gold standard). These methods help diagnose glaucoma, alongside fundoscopy (to check for optic disc cupping) and visual field assessments (to detect peripheral vision loss).

💊 Treatment and Management of Open-Angle Glaucoma

The goal of glaucoma treatment is to reduce intraocular pressure, especially when it reaches 24 mmHg or above. Prostaglandin analogs like latanoprost, which increase uveoscleral outflow, are the first-line treatment, though side effects include eyelash growth and iris pigmentation. Other treatments include topical beta blockers, carbonic anhydrase inhibitors, and sympathomimetics, all aiming to reduce aqueous humor production or increase its drainage. In severe cases, a trabeculectomy surgery may be performed to create a new drainage channel for the aqueous humor.

📢 Conclusion and Resources

Tom concludes the video by encouraging viewers to explore more resources on Zero2Finals.com, including detailed notes, illustrations, questions, books, and flashcards. He also mentions his personal YouTube channel where he shares tips on learning medicine. He encourages viewers to subscribe and follow the channel for more content.

Keywords

💡Open-angle glaucoma

Open-angle glaucoma is a type of glaucoma where the drainage angle for the aqueous humor remains open, but the trabecular meshwork becomes gradually less efficient, leading to increased intraocular pressure. This slow buildup of pressure can cause optic nerve damage, often without noticeable symptoms in the early stages. The video focuses on this type of glaucoma, explaining its anatomy, causes, and treatment options.

💡Intraocular pressure

Intraocular pressure (IOP) refers to the fluid pressure inside the eye. In the context of glaucoma, increased IOP is a key factor that causes optic nerve damage. The video details how a blockage in the trabecular meshwork can lead to higher IOP, causing glaucoma. A normal IOP range is 10-21 mmHg, and managing this pressure is essential to treating glaucoma.

💡Aqueous humor

Aqueous humor is the clear fluid produced by the ciliary body that fills the anterior and posterior chambers of the eye. It supplies nutrients to the cornea and lens and helps maintain intraocular pressure. In glaucoma, its impaired drainage through the trabecular meshwork leads to increased pressure. The video explains how this fluid flows through the eye and the consequences of its disrupted outflow.

💡Trabecular meshwork

The trabecular meshwork is a spongy tissue located at the drainage angle between the cornea and the iris, responsible for regulating the outflow of aqueous humor. In open-angle glaucoma, this meshwork develops increased resistance, which prevents the fluid from exiting the eye properly, leading to elevated intraocular pressure. The video discusses this as the main site of dysfunction in open-angle glaucoma.

💡Optic nerve

The optic nerve transmits visual information from the eye to the brain. In glaucoma, increased intraocular pressure can damage the optic nerve fibers, leading to vision loss. The video highlights how the optic nerve is affected in glaucoma, specifically focusing on the cupping of the optic disc as a result of prolonged elevated pressure.

💡Cupping of the optic disc

Cupping of the optic disc refers to the enlargement of the optic cup (a depression in the optic disc) due to increased intraocular pressure. When the optic cup becomes more than 0.5 times the size of the optic disc, it is considered abnormal and may indicate glaucoma. The video describes this as a key diagnostic feature of optic nerve damage in glaucoma.

💡Non-contact tonometry

Non-contact tonometry is a method used to measure intraocular pressure by shooting a puff of air at the cornea and measuring its response. It is commonly used in optometry clinics for general screening, though it is less accurate than other methods. The video explains how this technique is used to detect potential cases of glaucoma.

💡Goldman applanation tonometry

Goldman applanation tonometry is considered the gold standard for measuring intraocular pressure. It involves direct contact with the cornea using a device that applies pressure to get an accurate reading. The video contrasts this method with non-contact tonometry, noting its higher accuracy in diagnosing glaucoma.

💡Prostaglandin analogs

Prostaglandin analogs, such as latanoprost, are first-line treatments for open-angle glaucoma. These eye drops work by increasing the outflow of aqueous humor through the uveoscleral pathway, lowering intraocular pressure. The video mentions this as the primary treatment option for reducing IOP and managing glaucoma.

💡Trabeculectomy

Trabeculectomy is a surgical procedure used to treat glaucoma when eye drops fail to lower intraocular pressure. It involves creating a new channel for aqueous humor to drain from the anterior chamber to a space under the conjunctiva, forming a 'bleb' where the fluid is reabsorbed. The video discusses this surgery as a last resort for managing open-angle glaucoma.

Highlights

Introduction to open-angle glaucoma, explaining it as optic nerve damage caused by a rise in intraocular pressure.

Open-angle glaucoma is due to increased resistance in the trabecular meshwork, leading to slow pressure buildup in the eye.

The anatomy of the eye, including the roles of the anterior and posterior chambers, filled with aqueous humor, is essential to understanding glaucoma.

Aqueous humor is produced by the ciliary body and drains through the trabecular meshwork into the canal of Schlemm.

Intraocular pressure normally ranges between 10 to 21 mmHg, with higher pressure indicating potential glaucoma.

Cupping of the optic disc is a key sign of glaucoma, where the optic cup becomes larger due to increased pressure.

Risk factors for open-angle glaucoma include age, family history, Black ethnic origin, and myopia (nearsightedness).

Open-angle glaucoma is often asymptomatic in early stages, detected during routine eye exams by checking intraocular pressure.

Peripheral vision is affected first in glaucoma, leading to tunnel vision as the disease progresses.

Glaucoma can also present with symptoms like fluctuating pain, headaches, blurred vision, and halos around lights, especially at night.

Non-contact tonometry is a common, less accurate way to measure intraocular pressure by using a puff of air.

Goldman applanation tonometry is the gold standard for measuring intraocular pressure, involving direct contact with the cornea.

Management of glaucoma aims to reduce intraocular pressure, with treatment often starting at 24 mmHg or above.

Prostaglandin analogues like latanoprost are first-line treatments, increasing the uveoscleral outflow to reduce eye pressure.

Surgical options, such as trabeculectomy, create a new drainage channel for aqueous humor when eye drops are ineffective.

Transcripts

[Applause]

[Music]

hi this is tom from zero2finals.com

in this video i'm going to be going

through open angle glaucoma

and you can find written notes on this

topic at zero to finals dot com slash

open angle glaucoma or in the

ophthalmology section

of the zero to finals medicine book

so let's jump straight in glaucoma

refers to the

optic nerve damage that's caused by a

significant rise in

intraocular pressure the intraocular

pressure is essentially the pressure

within the eye

itself raised intraocular pressure is

caused by a blockage

in the aqueous humor trying to escape

the eye

and we'll talk more about the

pathophysiology shortly

there are two types of glaucoma open

angle

and closed angle and here we're going to

be talking about

open angle so let's talk about the basic

anatomy and physiology because it's

important to understand

some basic anatomy and physiology of the

eye and how the eye

functions in order to understand the

pathophysiology

of glaucoma the vitreous

chamber of the eye is filled with

vitreous humor

and this is the main bulk the main area

of the eye

the anterior chamber is between the

cornea and the iris

and the posterior chamber is between the

lens and the iris

these anterior and posterior chamber are

filled with

aqueous humor that supplies nutrients to

the cornea and keeps it healthy

the aqueous humor is produced by the

ciliary body

and then the aqueous humor flows around

the iris

from the posterior chamber into the

anterior chamber

where it drains through something called

the trabecular

meshwork at the angle between the cornea

and the iris

the aqueous humor flows from the ciliary

body

around the lens and under the iris

through the anterior chamber through the

trabecular meshwork and

into something called the canal of

schlem

from the canal of slam it eventually

enters the general circulation

and is reabsorbed into the body the

normal

intraocular pressure is 10 to 21

millimeters of mercury and this pressure

is created by the resistance to flow

through the trabecular meshwork so

aqueous humor

is trying to flow through the trabecular

meshwork

out of the eye and if there's more

resistance in the trabecular meshwork

the pressure will go up because there's

more resistance

of aqueous humor trying to escape the

eye if there's less resistance

the pressure will go down because the

aqueous humor is able to flow more

freely out of the eye

so let's talk about the pathophysiology

of open-angle glaucoma

and in open-angle glaucoma there's a

gradual

increase in resistance through the

trabecular meshwork

and this makes it more difficult for

aqueous humor to flow through the

meshwork and

exit the eye therefore the pressure

slowly builds within the eye

and this gives a slow and chronic onset

of glaucoma so let's talk about the

effects of the increased pressure in the

eye

and this causes cupping of the optic

disc

and remember in the center of a normal

optic disc is something called the optic

cup and this is a small indent in the

optic disc

and is usually less than half the size

of the optic cup

and when there's a raised intraocular

pressure this

indent becomes larger because the

pressure in the eye puts pressure on

that indent making it

wider and deeper this is called cupping

an optic cup greater than 0.5 the size

of the optic disc

is abnormal so if the optic cup is more

than half the size

of the optic disc this suggests

cupping and could indicate glaucoma

so what are the risk factors for open

angle glaucoma or increasing

age family history black ethnic origin

and near-sightedness which is called

myopia are all

key risk factors to remember for your

exams

let's talk about the presentation of

open angle glaucoma

often the rise in intraocular pressure

is asymptomatic for a long period of

time

it's usually diagnosed by routine

screening when they attend an

optometry appointment for an eye check

so whenever you get your eyes checked at

the optometrist

they check the intraocular pressure to

see whether there's any possibility

you've developed glaucoma

glaucoma tends to affect the peripheral

vision first

so there may be a gradual loss of

peripheral vision

as it closes in slowly and they

experience something called tunnel

vision

it can also present with gradual onset

of fluctuating pain

headaches blurred vision and typically

halos surrounding lights which are worse

at night time

so if a patient is losing their

peripheral vision and at night time they

see halos appearing around lights

think about glaucoma

so how can we measure intraocular

pressure well there's two

main ways we can measure the intraocular

pressure the first is something called

non-contact

tonometry and this is commonly used with

a machine

to estimate the intraocular pressure

when you go to an opticians

and this involves shooting a puff of air

at the cornea

and measuring the corneal response to

that puff of air

if the cornea has a lot of pressure

inside it from glaucoma

it won't react very much when air is

shot at it

whereas if you've got a very soft cornea

with a lack of

intraocular pressure there'll be a large

reaction to that puff of air

this is a less accurate way of measuring

the intraocular pressure

but it gives a helpful estimate for

general screening purposes

the second way of measuring intraocular

pressure is something called

goldman applination tonometry

this is the gold standard way of

measuring the intraocular pressure

this involves using a special device

mounted on a slip lamp

that actually makes contact with the

cornea and applies different pressures

to the front of the cornea to get an

accurate measurement of the intraocular

pressure

so the machine actually presses down on

the cornea

to check how much resistance there is

and indicate how much pressure there is

within that cornea

so how do we make a diagnosis of

glaucoma well firstly

using a goldman applination tonometry

which can be used to check the

intraocular pressure

fundoscopy is used to assess

the optic disc for cupping and also for

optic nerve health

visual field assessment is important to

check for peripheral vision loss

and all three of these will be useful

for making the diagnosis

so how do we manage open angle glaucoma

management of glaucoma aims to reduce

the intraocular pressure

treatment is usually started at an

intraocular pressure

of 24 millimeters of mercury or above

patients should be closely followed up

to assess the response to treatment

and treatment will be guided by an

ophthalmologist

the first line treatment is something

called prostaglandin analogues

used as eye drops and an example of this

is

latanoprost and these eye drops increase

the uveo

scleral outflow and the uv scleral

outflow refers to the drainage of the

aqueous humor from the anterior chamber

into the anterior chamber angle

rather than going through the

traditional trabecular meshwork

notable side effects from prostaglandin

analog eye drops like litanoprost

are eyelash growth eyelid pigmentation

and iris pigmentation typically you get

a browning of the iris

the other options for treating open

angle glaucoma are

topical beta blockers like timolol

which reduce the production of the

aqueous humor

carbonic anhydrase inhibitors like

dorsolamide

which reduce the production of the

aqueous humor and

sympanometics such as brimonidine

which reduce the production of aqueous

fluid and also

increase the uv scleral outflow

finally a surgical procedure called

trabeculectomy may be used

where the eye drops are ineffective this

involves creating a new

channel from the anterior chamber

through the sclera

to a location under the conjunctiva this

causes a little bleb

under the conjunctival where the aqueous

humor drains

and the aqueous humor is then reabsorbed

from this bleb into the general

circulation

so it essentially creates a new way for

aqueous humor to drain away from the eye

thank you for watching this video if you

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left a comment or subscribe to the

channel thank you so much it really

helps

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