Intro III - Packet 3

two types of glaucoma

• open angle glaucoma (chronic)

• closed angle glaucoma (acute)

two things that happen with glaucoma in the eye

• intraocular pressure increases

• increased pressure damages optic axons (it is an optic neuropathy caused by increased intraocular pressure)

open angle glaucoma (chronic condition)

an optic neuropathy characterized by progressive peripheral visual field loss, followed by central field loss in a typical pattern

prevalence of open angle glaucoma

• much more common and closed angle

• in 2020:

  • 65.5 million cases worldwide

  • 3.4 million cases in the US

what population does open angle glaucoma affect the most

those of european and african descents

other names for closed angle glaucoma

“narrow angle glaucoma”

“acute glaucoma”

prevalence of closed angle glaucoma

only makes up 5% of glaucoma cases, but it is an ophthalmologic emergency

what population is closed angle glaucoma more common in

those of asian descents

two cavities of the eye

1. posterior cavity which is the vitreous chamber

2. anterior cavity which is split into the posterior chamber and anterior chamber

posterior chamber

between the iris and the ciliary body and lens

anterior chamber

extends from the cornea to the iris

explain the flow of aqueous humor

• the ciliary body secretes aqueous humor fluid into the posterior chamber

• it flows from the posterior chamber, through the pupil, into the anterior chamber

• at the base of the anterior chamber, the aqueous fluid flows through a collecting duct called the canal of schlemm

• the fluid is then returned to the veins of the sclera

intraocular pressure

the pressure created by the fluid in the anterior chamber pressing against the inner surface of the cornea

if aqueous humor cannot enter the canal of schlemm…

fluid pressure rises, distorting small tissue within the eye

what is the IOP based on

the balance between fluid production and drainage determines the IOP

nickname for open angle glaucoma and why

“a silent thief in the night that steals your vision”

• it progresses very slowly and can go undetected for years- so it robs patients vision slowly

“Individuals with open angle glaucoma…

…rarely experience symptoms. Some people are unaware of field loss even when it has progressed to central tunnel vision. Thus, open angle glaucoma is generally detected incidentally on comprehensive ophthalmic examination.”

Open angle glaucoma is an optic neuropathy characterized by…

…progressive peripheral visual field loss, followed by central field loss in a typical pattern”

pressure build up…

…damages optic nerve

what is one of the most common causes of blindness in the united states and why is it so dangerous

open angle glaucoma - it can go undetected for years and progresses very slowly

open angle glaucoma is a _______, ________ ______ _________ characterized by….

asymptomatic, progressive optic neuropathy characterized by:

1. disc enlargement

2. cupping

3. visual field loss

what is the most common type of glaucoma

open angle glaucoma - 90% of glaucoma cases in the USA

how many people over the age of 40 are affected

2% over the age of 40

in what two categories do patients with open angle glaucoma have a decreased quality of life

1. driving - decreased peripheral vision

2. falls

risk factors for open angle glaucoma

• african americans over age 40

  • 3 times greater incidence in african americans than caucasians

  • the age adjusted blindness rate for glaucoma in AA’s is 6.6 times higher than in caucasians with blindness beginning 10 years earlier in AA’s

• caucasians over age 65

• 2.5 fold increased risk with family history

• DM

• HTN (increases intraocular pressure)

• myopia - nearsightedness

pathophysiology of open angle glaucoma

subtler microscopic blockage of the aqueous outflow near the canal of schlemm

symptoms (and more) of open angle glaucoma

• patients rarely experience any symptoms (asymptomatic)

• often diagnosed on comprehensive ophthalmic examination

• modest pressure build up over time

• no eye pain or redness

• pupil and cornea WNL

• often affects both eyes at the same time

American Academy of Ophthalmology screening criteria for those with no risk factors of eye disease

these individuals should receive a comprehensive ophthalmologic examination every:

• 5 to 10 years before age 40

• 2 to 4 years from age 40 to 54

• 1 to 3 years from age 55 to 64

• 1 to 2 years from age 65 and older

American Academy of Ophthalmology screening guidelines for those at risk for eye diseases like glaucoma

(african americans, hispanics, those with a family history) should receive a comprehensive eye examination every:

• 1 to 2 years if younger than 40 or age 55 and older

• 1 to 3 years from age 40 to 54

the only way to discover glaucoma before it becomes severe

get routine comprehensive eye examinations with a painless pressure test component (tonometry)

diagnosis of glaucoma is made by

• evidence of increased intraocular pressure (> 22 mm of mercury)

• retinal changes

  • pale optic disc

  • cup enlargement (larger than 50% of the vertical disc diameter)

  • cupping - a “scooped out” appearance of the central cup and nasal displacement of the blood vessels

• loss of visual fields (peripheral vision)

intraocular pressure for diagnosis of glaucoma

must be greater than 22 mm of mercury

normal intraocular pressure of the eye

8 to 21 mm of mercury

what is the test called that measures intraocular pressure and how does it work

tonometry - measures the force required to make an indentation on the eye

• done with a tono pen or with a non contact device - air puff machine

snellen chart exam with glaucoma

usually WNL - patients have good visual acuity, but a poor peripheral visual field

how do we simulate poor peripheral vision

roll up a piece of paper and place in over the eye - we can still see straight ahead but lack peripheral vision

automatic perimetry

an important diagnostic test that is much more reliable to detect visual field loss in glaucoma compared with confrontational field testing

perimetry test (visual field test)

• measures all areas of eyesight including the peripheral vision

• patients sit and look into a bowl shaped device (perimeter), they stare directly at the center of the bowl and lights begin to flash

• patients press the button when they see the flash

• generates a graph of the patients visual field - darker areas are where vision is the worst

what is the best measure for glaucoma progression

perimetry test

treatment for open angle glaucoma

no cure

what does treatment of open angle glaucoma focus on

decreasing intraocular pressure to prevent progressive visual field loss and changes to the optic disc

two categories of treatment for open angle

1. pharmacological therapy

2. laser therapy

Both are first line treatments

dosage of treatments for open angle

• doses for once or twice a day are very expensive

• we use high dose per day regimens (4 times/day) which is less expensive, but we have problems with compliance

two categories of pharmacological medications for glaucoma

• increase aqueous outflow

  • prostaglandins

  • alpha adrenergic agonists

  • cholinergic agonists

• decrease aqueous production

  • alpha adrenergic agonists

  • beta blockers

prostaglandins

• latanoprost

• bimatoprost

• travoprost

alpha adrenergic agonist

brimonidine

cholinergic agonists

• acetylcholine (miochol-e)

• carbachol (miostat)

• pilocarpine

beta blockers

• levobunolol

• carteolol

• metipranolol

trabeculoplasty

a procedure that improves aqueous outflow by improving drainage in the trabecular meshwork

how is a trabeculoplasty done

laser 80 to 100 holes in the trabecular meshwork. the small holes cause the burnt tissue to contract which pulls open the trabecular meshwork on the adjacent tissues to improve drainage

how often does angle closure glaucoma present

5% of all glaucoma cases

how severe is closed angle

it is an ophthalmologic emergency that can cause rapid blindness or vision loss

epidemiology of closed angle glaucoma

there is a decrease of outflow of aqueous fluid from an abrupt blockage of the drainage angle. If aqueous fluid cannot drain, intraoc