1. WORKUP OF A CASE OF
PRIMARY OPEN ANGLE
GLAUCOMA
By- Dr. Priyanka Raj
2. Glaucoma
• Chronic, progressive optic neuropathy caused by a group of ocular conditions
which lead to damage of the optic nerve with loss of visual function
• IOP is the major risk factor
3. PRIMARY OPEN ANGLE GLAUCOMA
(POAG)
• Primary open-angle glaucoma (POAG) can be considered a chronic,
progressive, anterior optic neuropathy that is accompanied by a
characteristic cupping and atrophy of the optic disc, visual field loss,
open angles, and no obvious causative ocular or systemic conditions
4. Epidemiology
• Worldwide, over 2 million people develop this condition every year
• It is estimated that 45 million people in the world have open-angle glaucoma.
• Glaucoma (both open-angle and angleclosure) is the second leading cause of blindness worldwide,
with approximately 8.4 million people blind from glaucoma.
• In southern India, the prevalence of open angle glaucoma is 1.6% of the population with greater
than 98% unaware that they have the disease.
5. Incidence
• The Rotterdam study showed that the incidence of glaucoma over 6.5 years in those over 55 years
of age was 1.2% for probable open-angle glaucoma and 0.6% for definite open-angle glaucoma
6. GENETICS
• Mutations at 15 loci in the human genome GLC1A to GLC1O
GLC1A chromosome1 in the q23–25 region
GLC1Bchromosome 2
4 susceptible genes have been identified
• MYOC gene (chromosome 1q21-q31), coding for the glycoprotein myocilin that is found
in the trabecular meshwork and other ocular tissues
• OPTN gene on chromosome 10p, which codes for optineurin
• WDR36 gene on chromosome 5q22
• NTF4 gene on chromosome 19q13.3.
(Among them MYOC is the most frequently mutated gene in POAG)
• endothelial nitric oxide synthase gene in glaucoma associated with migraine
• Chromosoe 3, 15
7. Risk factors
1. Intraocular pressure( IOP)- most imp risk factor (In
the Baltimore Eye Survey, at an IOP of 30 mmHg,
nearly 7% of Caucasians and 25% of African
Americans had POAG)
2. Age - most cases >40 years, unusual <40years
3. Race – blacks and hispanics >whites
4. Family history and inheritance – sibling > offspring
5. Central corneal thickness
6. Diabetes mellitus
7. Reduction in perfusion pressure (BP-IOP)
8. Myopia (independent relationship between longer
axial length (axial myopia) and a higher prevalence
of OAG)
9. Retinal diseases like central retinal vein occlusion,
retinal detachment and retinitis pigmentosa
8. 10. Thyroid disorders
11. Cigarette smoking
12. Steroid usage – topical (>6 weeks)
13. Disc hemorrhage
14. Larger cup-to-disc ratio
15. Migraine - These conditions may decrease autoregulation of optic disc blood flow
9. Pathogenesis of rise in IOP
Rise in IOP occurs due to decrease in the aqueous outflow
• Failure of aqueous outflow pump mechanism
• A loss of trabecular endothelial cells interfere with various important trabecular
functions, including phagocytosis and synthesis and degradation of macromolecules.
• A reduction in pore density and size in the inner wall endothelium of Schlemm’s
canal.
• Accumulation of foreign material in the trabecular meshwork and juxtacanalicular
tissue, including pigment, red blood cells, glycosaminoglycans, amorphous material,
extracellular lysosomes, plaque like material, and protein
10. • Collapse of schlemm’s canal and absence of giant vacuoles in the cells lining it
(occurs a very high IOP)
• Disturbance of neurologic feedback mechanisms. interference with the feedback
mechanism could lead to unchecked elevation of IOP.
• Association of TGF-β
11.
12. • Histopathologic study of the conventional aqueous drainage system from patients with POAG
reveals a number of abnormalities, including those that follow (Fig. 17-1):
• 1. Alterations in the trabecular beams, including fragmentation of collagen, increased curly and
long-spacing collagen, and coiling of fiber bundles
• 2. Thickened basement membranes
• 3. Narrowed intertrabecular spaces
• 4. Fused trabecular beams
• 5. Decreased number of trabecular endothelial cells
• 6. Reduced actin filaments
• 7. Accumulation of foreign material
• 8. Decreased number of giant vacuoles
• 9. Narrowing of collector channels
• 10. Closure of Schlemm’s canal
• 11. Thickened scleral spur.
13. Pathogenesis of glaucomatous optic
neuropathy
• Cupping is the hallmark of glaucomatous damage. Cupping consists of backward bowing of the
lamina cribrosa, elongation of the laminar beams, and loss of the ganglion cell axons in the
rim of neural tissue
• 1.Ischaemic theory
• Suggests that poor blood perfusion of ONH causes ischaemia and resultant loss of optic nerve
fibres
• 2.Mechanical theory
• Suggests that weakness of supporting tissues of optic nerve head makes it susceptible to
mechanical deformation by IOP with resultant nerve fibre damage
14. • 3. Immune theory
• Increased incidence of paraproteinemia and auto antibodies and antiglutathione S-
transferace antibodies cause retinal ganglion cell apoptosis
• 4. Apoptotic theory
• Genetically programmed destruction of retinal ganglion cells may play a part in
the pathogenesis
17. • Symptoms
• Alarming signs
• Past ocular History
• Systemic History
• Drug History
• Addictions
• Family History
• Socioeconomic History
18. Patient particulars
• Age- increasing age
• Gender- females although in some recent studies men have also been found
to have more predilection
• Race- POAG highest in blacks, intermediate in whites & south Asia, lowest
in northern Asia
19. Age
• Increasing age related to increased prevalence of
• glaucoma
• Rule of thumb of prevalence
• Doubles for each decade over 40 (RR=2/decade)
• Ten fold higher in > 80yrs compared to 40-49 yrs.
20. Complaints
• Insidious and asymptomatic disease Gradual painless loss of vision
• Mild headache, eye ache
• Visual field defect (SCOTOMA)
• Frequent change in presbyopic glasses
• Delayed dark adaptation
• Significant loss of vision and blindness
21. Past ocular history
• Myopia- 2-3 folds increased POAG prevalence.
(It is often difficult to diagnose glaucoma in myopic individuals because they have (1) broad,
shallow optic cups with less distinct margins; (2) baring of the blind spot or other refractive
scotomata on visual field testing; (3) low ocular rigidity, which makes Schiøtz tonometer readings
inaccurate, and (4) thin corneas and sclera which may give falsely low readings on Goldmann
tonometry.)
• Previous glaucoma Treatment
• For secondary glaucoma
• Uveitis
• Ocular surgery
• Refractive, RD, cataract
• Trauma
22. Sytsemic illness
• Diabetes
• Probable risk factor
• POAG prevalence appears to be 2-folds than normal
• Blood pressure
• Most meaningful is ‘diastolic ocular perfusion pressure’
• DOPP < 55 mmHg have RR of 3.2 in POAG incidence
• Hypertension relation to glaucoma is confusing
• Thyroid disorders
• Graves disease- raised episcleral pressure
• Some also suggest- hypothyroidism
• Cushing syndrome
• Pituitary dysfunctions
• Testosterone may raise IOP
• Estrogen & progesterone may lower IOP
23. Drug history
• Current & previous topical medications
• Steroids use
• Anticoagulants- for surgical planning
• Drugs that raise IOP-
• Corticosteroids
• Anticholinergics & antihistamines
• Sulfonamides- rare
• Caffeine- slight transient rise
• Ketamine & muscle relaxants
25. Family history
• 5–50% of cases of POAG are hereditary, with the best estimate being 20–25%.
• The risk of developing POAG in first degree relatives is 4–16%
• A monozygotic and dizygotic twin study estimated the inheritability to be 13%.
• Sibling of glaucoma pt. is at more risk than either parent or child
26. Socioeconomic status
• One of the costly disease
• Cost of medications for life long is difficult in our setup
27. EXAMINATION
• Slitlamp biomicroscopy for anterior segment
• Tonometry for IOP evaluation
Central corneal thickness(CCT)
Diurnal variation test
• Gonioscopy
• Fundus evaluation for optic nerve head changes
• Perimetry for visual field defects
• Nerve fibre layer analyzer (NFLA)
• Provocative tests
Water drinking test
28. • Visual acuity measurement
The best-corrected visual acuity, at distance and at near, should be determined.
• Anterior segment signs
corneal haze maybe seen occasionally, although it is more associated with angle closure
glaucoma
• AC- normal or deep in myopes. Gonioscopy is also done to exclude the alternative
diagnosis of angle-closure glaucoma or secondary causes for IOP elevation, such as
angle recession, pigment dispersion, exfoliation syndrome, peripheral anterior
synechiae, angle neovascularization, and inflammatory precipitates.
• Pupil examination
sluggish pupil
Maybe middilated
RAPD
29. • Intraocular pressure changes. Repeated observations of IOP(every 3-4 hour),
for 24 hour( diurnal variation test)
Different patters of diurnal variation of IOP
Morning rise in IOP- 20% of cases
Afternoon rise in IOP-25% of cases
Biphasic rise in IOP-55% of cases
Variation in IOP of over 5 mm Hg
(Schiotz) is suspicious and over 8 mm of Hg is diagnostic of glaucoma
• On gonioscopsy-
The angle is open
30. Optic nerve head evaluation
Normal optic nerve head
• Neuroretinal rim – tissue between the
outer edge of the cup and disc margin.
A normal rim is orange or pink in
colour and follows the ISNT rule
• Rim-disc ratio
Cup-disc ratio- normal vertical
C/D ratio= 0.1-0.4, although it varies
with the size of the disc
• Asymmetry between 2 eyes is < 0.2
31. Early glaucomatous changes
• Vertically oval, large cup
• Asymmetry of CDR >0.2 between 2
eyes
• Large cup i.e ≥0.6(normal cup size is 0.3
to 0.4)
• Pallor of the disc
• Splinter haemorrhages
• Atrophy of RNFL
(Note: ISN’T rule is no more applicable)
32.
33. Advanced glaucomatous changes
• Bayonetting sign: double angulation of blood
vessels
• Baring of circulinear blood vessels
• Laminar dot sign: Slit like pores of lamina
cribrosa is visible
• Marked cupping: Cup to disc ratio 0.7 to 0.9
• Nasal shifting of blood vessels
• NRR thinning (Crescentic shadow adjacent to
disc margin)
• Pulsation of retinal arterioles at disc margin
34. Glaucomatous optic atrophy
• All the neural tissue of the disc is destroyed and the optic nerve head
appears white and deeply excavated
35.
36. Visual field defects
It is a 3D hill – peak being fovea and at ground level,
it extends ~ 50° superiorly, 60° nasally, 70° inferiorly
and 90° temporally.
Normal blind spot is 15° temporal to the fixation and
measure 6° wide and 8° high.
Anatomical basis :
• Distribution of retinal nerve fibres
1. Papillomacular bundle(PMB)
2. Arcuate fibres
3. Radiating fibres
• Arrangement of nerve fibres
• Deeper fibers from peripheral retina occupy
peripheral or superficial location in ONH
• Superficial fibers from central retina occupy
central or deep location in ONH
within the optic nerve-arcuate fibres occupy temporal
portion of the disc and are most susceptible to damage
37.
38. Glaucomatous field defects
• Isopter contraction
• Baring of blind spot
• Wing shaped paracentral scotoma-earliest
clinically significant field defect
• Seidel’s scotoma – paracentral scotoma
joins the blind spot to form a sickle shaped
scotoma
• Arcuate or Bjerrum’s scotoma
• Ring or double arcuate scotoma
• Roenne’s central nasal step
• Peripheral field defects
• Advanced glaucomatous field defects
39. Early non-specific changes:
1. Isopter contraction (Generalized
depression): Mild constriction of central and
peripheral field
2. Baring of blind spot: Exclusion of blind spot
from the central field due to inward curve of
the outer boundary of 30° central field
40. Early significant changes:
• Peripheral nasal step (may be early or late):
Due to unequal contraction of peripheral
isopter
• Small wing-shaped Paracentral
scotoma (Within Bjerrum’s area): Isolated or
associated with nasal step
• Siedel’s sickle-shaped scotoma: Paracentral
scotoma joins the blind spot (it is also known as
Derringer scotoma)
41. • Roenne’s central nasal step: Because of the
anatomy of the horizontal raphe, all complete
arcuate scotomas end at the nasal horizontal
meridian. A steplike defect along the horizontal
meridian results from asymmetric loss of nerve
fiber bundles in the superior and inferior
hemifields.
42. Late significant changes:
• Arcuate or Bjerrum scotoma: Extension of
Seidel’s scotoma in an area either above or
below the fixation point to reach the horizontal
line corresponding to the arcuate retinal nerve
fibers. In the temporal portion of the field, it is
narrow because all of the nerve fiber bundles
converge onto the optic nerve
• Ring or Double arcuate scotoma: When 2
arcuate scotomas join together
43.
44.
45. Advanced glaucomatous field defects
• Tubular vision: Only a small island of
central vision accompanied by temporal
island
• No light perception: Complete visual field
defect (temporal island is the most
resistant one)
46. Anderson’s criteria
• On static perimetry, glaucomatous field loss is considered significant if:
1. Analysis of glaucoma hemi-field test is abnormal in 2 consecutive occasions
2. 3 contiguous non-edge points on the pattern deviation plot within Bjerrum
area have a probability of < 5% of being in normal population, one of which
have a probability of < 1%
3. Pattern standard deviation (PSD) should have a probability of < 5%
confirmed on two consecutive tests
47. DIAGNOSIS
1. Primary open angle glaucoma (POAG)
raised IOP(>21 mm of Hg) associated with definite glaucomatous optic disc cupping and visual
field changes
2. Ocular hypertension or glaucoma suspect
patient has an IOP constantly more than 21 mm of Hg but no optic disc or visual field changes
3. Normal tension glaucoma (NTG) or low tension glaucoma (LTG)
diagnosed when typical glaucomatous disc cupping with or without visual field changes is
associated with an intraocular pressure constantly below 21 mm of Hg
50. NORMAL TENSION GLAUCOMA
• The term normal tension glaucoma (NTG), also referred to as low tension glaucoma is
labelled:
• Typical glaucomatous disc changes
• with or without visual field defects
• IOP constantly below 21 mm of Hg
• It is believed to result from chronic low vascular perfusion, which makes the optic nerve
head susceptible to normal IOP
• • Multifactorial disease
• • Higher prevalence of vasospastic disorders such as
• migraine headache and Raynaud phenomenon, ischemic vascular diseases, autoimmune
diseases, and coagulopathies
51. OCULAR HYPERTENSION
• Individuals with IOPs of 21 mmHg (the statistical upper end of the ‘normal’ range)
or greater, normal visual fields, normal optic discs, open angles, and absence of any
ocular or systemic disorders contributing to the elevated IOPs are referred to as
having ocular hypertension.
• occurs in 4–10% of the population over age 40
• The OHTS, showed that 9.5% of untreated ocular hypertensives will go on to develop
open-angle glaucoma as manifest by optic nerve changes or visual field changes in 5
years.
