Glaucoma Pharmacology Flashcards
Glaucoma
A group of conditions that have in common damage to the optic nerve (optic neuropathy)
There are numerous variables that influence glaucoma development, but increased intraocular pressure is the only treatable factor
Glaucoma Visual Impact
Extreme: central island of vision
You slowly lose peripheral vision. It’s a gradual onset. A lot of people don’t notice it. large amounts of people walk around with it undiagnosed
Untreated glaucoma: lights out blind. the central island is snuffed out and they go into complete darkness
Open Angle Glaucoma
80% of cases in the US
If you look at angle of the eye, it anatomically looks open cause the pressure is high
Genetic component as well as anatomic
Closed Angle Glaucoma
60-80% of cases in Asia
Angle looks crowded, looks like drain of eye is compromised
Genetic component as well as anatomic
Glaucoma Epidemiology
Not only a chronic disease but a common one
70 mil world wide
3 mil in the US
2.75 of the 3 mil have open angle glaucoma
So many people are undiagnosed that its hard to know if this is an underestimation
Most common causes of blindness
Reversible blindness: cataracts
Irreversible blindness: glaucoma
Demographics
Due to it’s chronicity, prevalence increases with age
By the time people get in their 80s, very large number of people get it
Academy of Ophthalmology recommends annual eye exams after the age of 40
African Americans are more likely to have a diagnosis and it tends to be more aggressive. They go blind quicker.
Even when you look at non-Hispanic whites (still about 8% of population in their age range, so it’s still common)
Risk Factors
African American Heritage
Fam Hx (cluster of genetic markers rather than a clearly delineated predisposition)
Older than 40
Elevated intraocular pressure
Use of topical or systemic steroids: overlooked by many. When you put people on steroids, about 10% of those people have an abrupt increase in intraocular pressure. this may tip them over the edge if they already have risk factors
Societal Impact of Glaucoma
Individual impact: 120,000 blind from glaucoma-in spite of treatment, 10% lose eyesight
Societal: 10 million doctor visits per year. cost of glaucoma to the US gov is 1.5 billion per year
Glaucoma Pathogenesis
- Glaucoma is a progressive optic neuropathy
- degeneration of the retinal ganglion cells leading to a characteristic optic nerve head appearance known as “cupping”
- Progression is related to intraocular pressure (IOP)
- damage occurs at the lamina cribrosa. compressive axonal injury and decreased axonal transport
Open Angle Glaucoma (pathogenesis)
- ciliary processes: create fluid inside the eye. Aqueous humor is created here, goes through posterior chamber, goes through the pupil and goes through the Canal of Schlemm. Ordinarily this is what happens
- —in open angle: it’s exactly what it looks like (normal anatomy at the anterior chamber BUT there’s a decreased efficiency of the trabecular mesh work. So it’s produced normally but there’s a relative inefficiency that happens
Narrow Angle Glaucoma (pathogenesis)
There’s crowding of the angle
There’s an anatomical obstruction
Aqueous Humor Dynamics
- the aqueous is nutrition to the avascular cornea and lens
- ultrafiltration and secretion: targets for drugs
- Tight junctions at the nonpigmented epithelium create a blood-eye barrier
- aqueous is produced at the rate of 2-3 microliters/min
can’t have things in the eye that are vascularized: need to be CLEAR. Eye requires a lot of nutrition to be able to maintain a clear image
-it’s a dynamic balance: constant production and resorption
Aqueous Humor Dynamics-Production
In the ciliary process core
There’s a pump mediated by CARBONIC ANHYDRASE. It pumps aqueous into the posterior chamber
Making the Diagnosis
- measuring pressure
- evaluation of the angle (where the action is)
- visualization of the optic nerve
- measurement of the visual field
Intraocular Pressure
Normal pressure is 10-21mm Hg (can be relative depending on the individual)
- diurnal fluctuation (if you suspect someone has high pressure, might keep that in the office all day and measure every few hours)
- multiple methods for measuring pressure
Applanation Tonometry
Intraocular pressure=contact force/Area of contact
- gauge to increase pressure that’s exerted
- can read a gauge, through the ocular that tells us we’ve exerted enough pressure to flatten the cornea and that’s what we read
Gonioscopy
Visualization of Angle structures
- the way we can see into angle is by using a handheld lens that sits right at surface of eye with a mirror at a specific angle
- can see into the anterior chamber
- we can see all the way around for 360 degrees and can evaluate if the anterior chamber is open or not (if can’t see all structures, the angle is closed and we grade how wide or open the angle is on the exam)
