epidemiology Flashcards
Glaucoma: definition
is a group of diseases; defined by:
- optic neuropathy
- remodeling of the optic nerve head cognitive tissues
- loss of neural tissue
- distinctive patterns of visual dysfunction.
when we talk about glaucoma we mostly talking about ……… glaucoma
POAG
Glaucoma: Natural history 5
- Glaucoma(POAG)isnotafastmovingdisease
- Thereisawiderangeofnormalandborderlineclinicalpresentations making correct detection and classification difficult
- Cross-sectionalclassification–verychallenging
- Sensitivity/Specificity(prevalence)
- Longitudinalchangeinclinicalfindings(Progression)isanimportantkeyto clinical management (incidence)
sensitivity
is the number of correct cases of disease that you were able to detect
specificity
is the number of correct normal individuals that were called as normals
Correct Classification (2)
true positive
true negative
Aqueous Humor Flow
aqueous humor is produced in the posterior chamber by the ciliary body. It then flows between the anterior surface of the lens and the posterior surface of the iris before reaching the anterior chamber. Aqueous fluid then circulates within the anterior chamber before returning to vascular circulation via the trabecular meshwork, Schlemm’s canal, and the finally the episcleral veins.
when the pupil is constricted the angle is ….
open
The pupil is mid-dilated, the iris is bowed anteriorly and the angle is
narrowed
The pupil is mid-dilated, the iris is bowed anteriorly and the angle is
reduced because the iris has a relatively flatter configuration
Classifcation of glaucoma (2)
- open angle
2. Closed angle
types of Open Angle glaucoma (6)
- POAG
- NTG
- JOAG
- OHT
- GLAUCOMA Suspect
- Secondary open angle
classification of Closed angle Glaucoma (5)
- Primary angle closure (PACG)
- primary angle closure/suspect (PAC/PACS)
- Chronic angle closure
- Secondary angle closure
- secondary angle closure without pupillary block
primary glaucoma
there is no other known cause
secondary glaucoma
there is an identifiable cause
Classification based on angle status is an important…..
therapeutic distinction
age dependent class-action
- ≤ 3 years (congenital) cornea normally stops growing at this age
- 435 adult (the majority)
POAG
usually associated with elevated IOP but no other known cause
NTG
not associated with elevated IOP and no other known cause
JOAG
glaucoma diagnosed at a young age (atypical)
OHT
elevated IOP without ONH structural degeneration or VF loss
Glaucoma suspect
NH degeneration or suspicious VF loss regardless of
IOP
2o open angle-
increased resistance to outflow—association with other conditions: pigmentary, phacolytic, steroid induced, angle recession, uveitis
PACG
narrow angle with elevated pressure or PAS with evidence of ONH
damage
PAC
narrow angle with elevated IOP or PAS but no evidence of optic nerve damage
PACS
narrow angle with no signs of trabecular meshwork or optic nerve damage
Chronic angle closure
IOP elevation caused by variable portions of the anterior chamber angle being permanently closed by PAS
Secondary angle closure (pupillary block)
pupillary block occurs as a result something other than anatomical configurations, e.g. intumescent lens air bubble etc.
Secondary angle closure(without pupillary block)
posterior pushing mechanism, e.g. lens iris interface pushed forward: uveal effusion, posterior segment or anterior pulling mechanism: PAS, ICE, neovascular glaucoma
Epidemiology of glaucoma
- second leading cause of blindness in us
- asymptomatic in early stages
- damage is irreversible (for now)
- 12.3 individual bilaterally bin in the us
incidence
the number of new cases of a disease that develop during a specific period
prevalence
total number of individuals with a disease at a specific time
how do we estimate prevalence
by taking a sample from the pool.
the pool is reduced when cases leave the pool
the number in the pool is increased by: community screening, examination, space flight
well established risk factors for POAG
- Elevated iop
- age
- family hx of glaucoma
- african ancestry/ mexican ancestry
- diabetes mellitus
who is at a higher risk of glaucoma:
- african american 40+ years
2. everyone 60+ especially mexican americans
why high iop is risk factor
- it satisfies many of the criteria required of a as risk factor and as a causative factor
- Strong dose-response relationship
- Lowering (25-30%) decreases the incidence and progression of glaucoma (by 1/3 to 1⁄2) compared to no treatment
IOP level is related to …………………. regardless of race
POAG prevalence,
age-specific prevalence of COAG
AA>Mex>white>asian>white
POAG: PREVALENCE BY AGE, GENDER, AND RACE
Men AA> WOMEN AA> WOMEN CAUCASIAN > MEN CAUCASIAN.
POAG RISK FACTOR: AFRICAN AMERICAN HERITAGE
POAG occurs at earlier age
- POAG more advanced when discovered
- blindnes = 3-4 items more common
- age > 70 = 10 % prevalence (2% for caucasians >70)
race is surrogate for (3)
- Genetics
- Environment
- Behavior
- Combinations of these factors
POAG: OTHER RISK FACTORS
- Family hx: sibling (OR: 3.7), parent (OR: 2.2), then child (OR: 1.1)
- Black: 4-10 fold (increasing with age) Baltimore eye study
- Latino: 2-10 fold (again with age) LALES
- Myopia (50-70%) increased prevalence with myopia: OHTS and EMGT did not show this as a risk factor
- Corneal thickness (cause or effect)
- Blood pressure: Diastolic Perfusion pressure
- Migraine—vasospasm and poor autoregulation capacity (seen in LTG)
- CSF pressure (low)
What does increased risk with decrased corneal thickness mean?
- Common connective tissue abnormalities
- thinner lamina
- IOP measurement error due to influence of corneal resistance on IOP measurement.
blood flow to the ONH
- SYSTEMIC BP GOES DOWN AT NIGHT
- IOP GOES UP AT NIGHT
- CSF CHANGES AS WELL
- DOES VASCULAR INSUFFIENCY LEAD TO AXONAL CHANGE.
