And you thought glaucoma was a disease in which there was too much pressure in the eye! So did most ophthalmologists until several years ago.
But pressure certainly plays a role. Glaucoma is just too complicated to fit a nice simple definition.
The Advanced Glaucoma Intervention Study documented that pressure does play a crucial role in the visual field damage of many patients. Note that the greater the percentage of visits in which the pressure was below 28, the less visual field defects developed.
The three mainstays of glaucoma diagnosis are inadequate. The actual intra-ocular pressure is too imprecise, and the changes in the visual field and the optic nerve occur too late to prevent most of the damage.
Two standard deviations above the mean occurs at about 22-23 mmHg.
Large intra-day fluctuations as seen on the right are a risk factor for glaucoma
The aqueous humor is manufactured by the non-pigmented ciliary epithelium in the posterior chamber.
Iris Bombe with secluded pupil
Normal anatomy. The aqueous humor is made in the posterior chamber and escapes through the trabecular meshwork of the anterior chamber.
These techniques illustrate the two most common means of measuring intra-ocular pressures. Applanation is probably the most accurate method but requires a slit lamp to use it.
Is this island of vision seen from a right eye or a left eye?
No two disks are alike. Signs suggesting glaucoma as seen in the right photo include a large cup, nasalization of vessels, and pallor of the cup. Note the peripapilary depigmentation on the right which can make the true cup:disk ratio difficult to estimate.
In glaucoma of all types, if not controlled. There is progressive enlargement of the cup, increased pallor of the base of the cup, and nasalization of the disk vessels.
Whie there is lots of variation in glaucomatous disks, three common characteristics stand out: large cups, pale color and nasalization of the vessels.
Note how vessels can hide under the lip of the disk which helps explain the apparent loss of continuity of vessels clinically.
Note that eyes with the thinnest corneas and highest pressures are at the greatest risk for developing open angle glaucoma.
The thinnest corneas with the greatest vertical cup:disk ratios are the most likely to develop open angle glaucoma.
This lecture covers only congenital and adult varieties of glaucoma but it is important to realize there are many other causes.
Haab’s striae are found only in congenital glaucoma.
The right eye in each patient has congenital glaucoma.
The classical signs and symptoms of narrow angle glaucoma.
Anterior chamber angles vary widely. Only Grade I angles are occludable and might lead to an angle closure attack, similar to what a Grade 0 looks like.
When the trabecular meshwork is obstructed, outflow is impaired and pressure rises. This can occur due to congenitally narrowed angles, the development of synechiae (top right), or rubeosis with a flat chamber (bottom right).
Mid-dilated, fixed pupils and cloudy corneas during an angle closure attack.
The permanent surgical cure for narrow angle glaucoma.
Remember: most patients with open angle glaucoma have no symptoms. This is the best reason to have periodic eye examinations with pressure checks and optic nerve evaluations.
No treatment works all the time!
Mechanisms of drug action vary and many people require multiple medications.
These are the two most common surgical procedures for open angle glaucoma with success rates of 80+%.
Creating a path for the aqueous to escape into the sub-conjunctival space is the aim of filtration surgery.
Harold E. Cross M.D., Ph.D.
(Contributions by Todd Altenbernd, MD)
10-06-09 v. 7.0
What is it?
A disease of progressive optic
neuropathy with loss of retinal
neurons and the nerve fiber layer,
resulting in blindness if left
“Glaucoma describes a group of diseases that kill retinal
“High IOP is the strongest known risk factor for glaucoma
but it is neither necessary nor sufficient to induce the
Libby, RT, et al: Annu Rev Genomics Hum Genet 6: 15, 2005
What causes it?
There is a dose-response
relationship between intraocular
pressure and the risk of damage to
the visual field.
How do we diagnose it?
IOP is not helpful diagnostically until it reaches
approximately 40 mm Hg at which level the
likelihood of damage is significant.
Visual fields are also not helpful in the early stages
of diagnosis because a considerable number of neurons
must be lost before VF changes can be
Optic nerve damage in the early stages is difficult
or impossible to recognize.
50% of people with glaucoma do not know it!
Intraocular pressure is not the only factor
responsible for glaucoma!
95% of people with elevated IOP will never have
the damage associated with glaucoma.
One-third of patients with glaucoma do not have
Most of the ocular findings that occur in people
with glaucoma also occur in people without
Population distribution of IOP
Normal vs glaucoma:
How do we measure
The normal visual field: an island of
vision in a sea of darkness:
The histology of glaucomatous optic nerve
Optic nerve signs of glaucoma progression
Increasing C:D ratio
Development of disk pallor
Disc hemorrhage (60% will show progression of
visual field damage)
Increased visibility of lamina cribosa
Ocular hypertension treatment study
To evaluate the effectiveness of topical ocular hypotensive
medications in preventing or delaying visual field loss
and/or optic nerve damage in subjects with ocular hypertension at moderate risk for developing open-angle
1636 participants aged 40-80 years with IOP 24-32
mm HG in one eye, and 21-32 in the other, randomly
assigned to observation and treatment groups.
TREATMENT GOALS: Reduce pressure to less than
or equal to 24 mm Hg with a minimum pressure
reduction of 20% from the baseline.
OUTCOME MEASURES: Development of reproducible
visual field abnormality or development of optic disc
MEDICATIONS USED: beta-adrenergic antagonists,
prostaglandin analogues, topical carbonic anhydrase
inhibitors, alpha-2 agonists, parasympathomimetic
agents, and epinephrine.
At 60 months, the
probability of developing
9.5% in observation group
4.4% in treatment group
OHTS parameters that
influence the risk of
Central corneal thickness
Percentage of OHTS participants in
observation group who developed POAG
(mean follow-up = 72 mo)
IOP vs central
Normal central corneal thickness: 545 – 550 u
Add or subtract 2.5 mmHg for each 50 u
change in central corneal thickness
Types of glaucoma
C. Adult (common types)
1. Narrow angle
2. Open angle
33. Congenital Glaucoma
Onset: antenatally to 2 years old
34. Congenital Glaucoma
Buphthalmos and cloudy corneas
35. Congenital Glaucoma
36. Narrow Angle Glaucoma
Onset: 50+ years of age
Nausea and vomiting
Halos around lights
Intermittent eye ache
Red, teary eye
41. Open Angle Glaucoma
Aka: chronic simple glaucoma (CSG)
and primary open angle glaucoma (POAG)
Onset: 50+ years of age
May have loss of central Visual field loss
and peripheral vision
Glaucomatous disk changes
42. Open Angle Glaucoma
History of trauma
History of steroid
C/D 0.6 or greater
elongation of disc