1 - Introduction to Glaucoma: Terminology, Epidemiology, and Heredity

Question 1

Glaucoma Definition

Answer 1

1. Group of diseases defined by characteristic optic neuropathy consistent with remodeling of connective tissue elements of optic nerve head
2. IOP one of the primary risk factors for development of glaucoma, but DOES NOT have a role in the definition of the disease
3. Preperimetric glaucoma → glaucomatous change in optic nerve head in absence of development of clinically detectable Visual Field changes

Question 2

Traditional Classification

Answer 2

1. Open angle → angle open
2. Closed angle → angle closed
3. Primary → No identifiable underlying anatomical cause leading to aq aoutflow obstruction and elevated IOP. Etiology of outflow obstruction thought to be abnormality in extracellular matrix of TM and in trabecular cells in juxtacanalicular region
4. Secondary → abnormality identified

Question 3

Classification: Outflow Obstruction Mechanism

Answer 3

Question 4

Normal Aqueous Humor Flow

Answer 4

1. Uveoscleral outflow → Through root of iris and ciliary body face into suprachoroidal space
2. Trabecular Meshwork → Schlemm canal → collector channels → venous system

Question 5

Combined-Mechanism Glaucoma

Answer 5

1. Secondary angle-closure in a patient who has open-angle glaucoma
   
   1. IOP elevated due to OAG from resistance of TM outflow
   2. IOP elevated due to synechiae
2. Narrow angle treated BUT with continued elevated IOP in absence of synechiae

Question 6

POAG

Answer 6

1. US → 1.86% of population older than 40 years
   
   1. 84K - 110K bilaterally blind (VA < 20/200, VF < 20 degrees)
2. ~ Accounts for 12.3% of cases of blindness; thus 2nd leading cause of blindness worldwide following cataract
3. 8M people with blindness from glaucoma with 4M caused by POAG
4. Blacks > Whites
5. Older > Younger
6. Elevated IOP, reduced perfusion pressure, advanced age, + family history, thin central corneas, race/ethnicity = risk factors associated with progression of POAG. Role of DM, HTN, atherosclerosis, ischemic vascular disease, gender debated.
7. Note → in assessment of elevated IOP, clinician should keep in mind circadian variation in IOP. Peak IOP occurs in early-morning hours and not seen in clinical setting

Question 7

PACG

Answer 7

1. Inuit > Asians > Whites = Blacks
2. Women, Older age (depth and volume of AC decreased with age predisposing to pupillary block), + family hx. If seen in myopic eyes consider plateau iris

Question 8

Genetics

Answer 8

1. Mechanisms of inheritance NOT clear
2. May be substantially influenced by environment (twins with discordant glaucoma rates), may demonstrate incomplete penetrance, many have AD inheritance pattern that may be polygenic
3. GLC1A gene → 1st gene described for POAG, aka TIGR/MYOC1, 3% of general OAG population