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Primary open angle glaucoma
1. Primary open angle glaucoma
POAG , also referred to as chronic simple glaucoma is generally a
bilateral, but not always symmetrical disease, characterized by:
Adult onset
IOP>21 mmHg
An open angle of normal appearance
Characteristic optic disc cupping
Visual field loss
2. Predisposing and risk factors
1. Intraocular pressure( IOP)- most imp risk factor
2. Age - most cases >40 years, unusual <40years
3. Race - blacks >whites
4. Family history and inheritance – sibling > offspring
5. Diabetes mellitus
6. Reduction in perfusion pressure (BP-IOP)
7. Myopia
8. Retinal diseases like central retinal vein occlusion, retinal
detachment and retinitis pigmentosa
9. Thyroid disorders
10. Cigarrete smoking
11. Steroid usage – topical (>6 weeks) , systemic
3. Pathogenesis of rise in IOP
• Rise in IOP occurs due to decrease in the aqueous
outflow
• Reduced aqueous outflow facility occurs due to failure
of aqueous outflow pump mechanism
Thickening and sclerosis of trabecular meshwork with faulty
collagen tissue
Narrowing of intertrabecular spaces
Deposition of amorphous material in the juxtacanalicular
space
Collapse of schlemm’s canal and absence of giant vacuoles in
the cells lining it
4. Epidemiology of POAG
Affects about 1 in 100 of the general population (of either sex) above
the age of 40 years
Forms about one third cases of all glaucomas
PREVALENCE
5. Clinical features
Symptoms
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
6. Signs
1. Anterior segment signs
- corneal haze
- sluggish pupil
2. 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
Fig.Patterns of diurnal variations of IOP: A, normal slight morning rise; B, morning rise seen in 20% cases of POAG; C, afternoon rise seen in 25% cases of POAG; D,
biphasic variation seen in 55% cases of POAG
7. 3. 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
Blood vessels
10. Early glaucomatous changes include :
Vertically oval, large cup
Asymmetry of >0.2 between 2 eyes
Large cup i.e., 0.6 or more (normal cup
size is 0.3 to 0.4)
Pallor of the disc
Splinter haemorrhages
Atrophy of RNFL
C
D
FIG.optic disc showing early glaucomatous changes
(C, Diagrammatic depiction; D, Fundus photograph)
11. Advanced glaucomatous changes
Marked cupping (cup size 0.7 to 0.9)
Thinning of neuroretinal rim
Nasal shifting of retinal vessels (Bayonetting sign)
Pulsations of the retinal arterioles
Lamellar dot sign
Glaucomatous optic atrophy
All the neural tissue of the disc is destroyed and the
optic nerve head appears white and deeply excavated
12. Optic disc showing advanced glaucomatous changes (A, diagramatic depiction; B, fundus photograph) and
glaucomotous optic atrophy (C, diagramatic depiction; D, fundus photograph
A
B
D
D
13. 4. Visual field defects
Anatomical basis :
Distribution of retinal
nerve fibres
1. Papillomacular bundle(PMB)
2. Arcuate fibres
Superior arcuate fibers(SAF)
Inferior arcuate fibers(IAF)
3. Radiating fibres
Superior radiating fibers(SRF)
Inferior radiating fibers(IRF)
Arrangement of nerve fibres
within the optic nerve-arcuate
fibres occupy temporal portion
of the disc and are most
susceptible to damage
Distribution of retinal nerve fibres
Arrangement of nerve fibres within optic
nerve head
14. Nomenclature of 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
Perpheral field defects
Advanced glaucomatous field
defects
Field defects in POAG: A, baring of blind spot; B,
superior paracentral scotoma; C, Seidel's scotoma;
D, Bjerru-m's scotoma; E, double arcuate scotoma
and Roenne's central nasal step
15. Criteria to grade glaucomatous field defects
• The criteria to label early, moderate and severe glaucomatous field defect
from the HFA central 30-2 test, single printout is depicted in Table
16. Assessing visual field glaucomatous
field defects
Camparing individual single field
printouts
Overview printout
Progression analysis software( GPA IN
HFA machines and peritrend in octopus
perimeter)
Visual field index(VFI)
• For proper understanding of Table
evaluation of the Humphrey single
field printout described should be
revised
17. INVESTIGATIONS
1. Tonometry
2. Central corneal thickness(CCT)
3. Diurnal variation test
4. Gonioscopy
5. Documentation of optic disc changes
6. Slit-lamp examination of anterior segment
7. Perimetry to detect the visual field defects
8. Nerve fibre layer analyzer (NFLA)
9. Provocative tests
Water drinking test
18. TONOMETRY
• The intraocular pressure (IOP) is measured with the help of an
instrument called tonometer
• Indentation tonometery
• Schiotz tonometer
• Applanation tonometry
• Goldmann tonometer
• Perkin’s applanation tonometer
• Pneumatic tonometer
• Pulse air tonometer
• Tono-Pen
Schiotz tonometer
Perkin’s hand-held
applanation tonometer
19. Technique of Schiotz tonometry
Technique of applanation tonometry
End point of applanation tonometry. (A) too small; (B) too
large; (C) end point.
20. Gonioscopy
The technique of biomicroscopic examination of the angle of the
anterior chamber using a goniolens.
The angle structures seen from behind forward are:
1. Root of the iris
2. Ciliary body band
3. Scleral spur
4. Trabecular meshwork
5. Schwalbe’s line
21.
22. PERIMETRY
• The visual field is a three-dimensional area of
a subject’s surroundings that can be seen at
any one time around an object of fixation
• Perimetry
• It is the procedure for estimating extent of the
visual fields
• Kinetic versus static perimetry
• Peripheral versus central field charting
• Peripheral field charting
Central field charting
• Confrontation method
• Perimetery: Lister’s, Goldmann’s and automated
• Campimetry or scotometry
• Goldmann’s perimetry
• Automated field analysis
• Manual versus automated perimetry
• Manual perimetry
• Automated perimetry
Extent of normal visual field
24. • AUTOMATED PERIMETRY
• Automated perimeters are computer assisted and test visual fields by a
static method
• Commonly used automated perimeters are: Octopus, Field Master and
Humphrey field analyser
Humphrey field analyser (automated
perimeter)
25. • Advantages of automated perimetry over manual perimetry
• Interpertation of automated perimetry print out field charts
• Automated perimeter variables
• Testing strategies and programmes
• Automated perimeter variables
• Background illumination
• Stimulus intensity
• Stimulus size
• Stimulus duration
• Testing strategies and programs
• Suprathreshold testing
• Threshold testing
• Full threshold testing
• Fast Pac
• SITA (Swedish Interactive Threshold Alogarithm)
Stimulus intensity scales compared
26. • Test programmes- The standard test programmes used with static threshold
strategy on the Humphrey’s Field Analyser (HFA) can be grouped as below
A. Central field tests
• Central 30 - 2 test,
• Central 24 - 2 test,
• Central 10 - 2 test,and
• Macular test
B. Peripheral field tests
• Peripheral 30/60-1,
• Peripheral 30/60-2,
• Nasal step, and
• Temporal crescent
C. Speciality tests
• Neurological-20,
• Neurological -50,
• Central 10-12, and
• Macular test
D. Custom tests
27. • Evaluation of Humphrey single-field
print-out
I. Patient data and test parameters
II. Reliability indices
III. Gray scale simulation of the test data
is depicted in zone III or part III of the
printout
IV. Total deviation plots
V. Pattern deviation plots
VI. Global indices
VII. Glaucoma hemifield test (GHT)
VIII.Actual threshold values
28. 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
29. Triad of abnormalities in disc, field and intraocular pressure (IOP) for the diagnosis
of glaucoma.
30. Management
The primary aim of treatment is to prevent functional impairment of vision.
It is important to perform a good baseline evaluation with which future progress
can be compared and documented
The initial data should include: visual acuity, slit-lamp examination of anterior segment,
tonometry (preferably with applanation tonometer); optic disc evaluation (preferably with
fundus photography), gonioscopy and visual field charting
GRADING- American Academy of Ophthalmology (AAO) grades severity of
glaucoma damage into mild, moderate and severe
32. Medical therapy
The initial therapy of POAG is still medical, with surgery as the last
resort
Basic principles of medical therapy of POAG
Identification of target pressure
Treatment regimes :
Single drug therapy
One topically instilled anti-glaucoma drug is chosen after considering
patient’s medical history and socio-economic background. If the initial drug is
ineffective or intolerable, it is to be replaced.
Combination therapy
If one drug is insufficient to control the IOP, then a combination therapy is
advised
Monitoring of therapy by disc changes and field changes and
tonometry is most essential on regular follow-up
33. ANTI-GLAUCOMA DRUGS
• Classification
• A. Parasympathomimetic drugs (Miotics)
• B. Sympathomimetic drugs (Adrenergic agonists)
• C. β-blockers
• D. Carbonic anhydrase inhibitors
• E. Hyperosmotic agents
• F. Prostaglandins
• G. Calcium channel blockers
34.
35. Prostaglandin analogues
Mechanism of action: uveoscleral outflow
Indication : first line therapy
Preparations :
1. Latanoprost (0.005%) - PG F2-α analogue, OD dosage, additive
effect with timolol.
2. Bimatoprost (0.03%) - decreases outflow resistance, OD dosage.
3. Travoprost (0.04%) – PG F2-α analogue, OD dosage.
4. Unoprostive isopropyl (0.12%) – dolosanoid related structure
similar to PG F2-α, BD dosage.
36. Side effects
Systemic
1. Upper respiratory tract symptoms (flu like )
2. Headache and precipitation of migraine in susceptible individuals
3. Muscle and joint pains
4. Skin rash
37. Ocular Side Effects
1. Conjunctival hyperaemia and
foreign body sensation
2. Eyelash lengthening, thickening,
hyperpigmentation, increase in
number
3. Iris hyperpigmentation
4. Increase in severity and recurrence
of herpetic keratitis
5. Anterior uveitis
6. Cystoid macular edema
38. β–adrenergic antagonists
Mechanism of action – block β receptors in ciliary processes
aqueous production
Indication – used as first line therapy for patients who cant PG
analogues.
Preparations
1. Timolol maleate(0.25%,0.5%) – non selective β blocker, BD
dosage
“short term escape” and “long term drift”
2. Betaxolol(0.25%,0.5%) – cardioselctive (β1) bocker, BD dosage,
useful in asthmatics, less effective than timolol.
3. Levobunolol(0.5%) – non selective β blocker
4. Carteolol(1%, 2%) – lesser incidence of bradycardia
5. Metipranolol(0.1%, 0.3%, 0.6%)
43. Mechanism of action trabecular outflow
Preparations
1. a) Pilocarpine e/d(1%,2%,4%)BD-QID dosage
b) ocuserts(pilo-20,pilo-40)
c)Pilocarppine gel(4%)HS
2. Carbachol(0.75%,1.5%,3%)BD-TDS dosage, may be useful in
pilocarpine sensitivity
3. Echothiophate iodide(0.125%)OD-BD dosage, intense miosis, more
GI side effects
4. Demecarium bromide(0.125%,0.25%)
5. Physostigmine(0.5%)
45. Ocular
1. Miosis leading to decrease visual acuity in cases of posterior polar cataracts,
impairment of night vision
2. Brow ache, head ache
3. Myopia
4. Keratitis
5. Iritis, iris cyst, posterior synechiae
6. Lenticular opacities
7. Retinal detachment
46. Carbonic anhydrase inhibitors
Mechanism of action aqueous humor production
Indications : useful as short term therapy, especially in acute cases
48. Side effects
Systemic
1. Paraesthesias, numbmness, lethargy, depression, malaise
2. Metabolic acidosis, hypokalemia, increased serum urate level
3. Urinary frequency
4. Anorexia, cramps, flatulence, weight loss, diarrhoea
5. Sulfonamide related – blood dyscrasias, renal calculi, steven-Johnson
syndrome
Topical agents are less likely to induce systemic side effects
49. Ocular
1. Induced myopia, blurred vision
2. Stinging senstaion
3. Conjunctivitis, keratitis
Ocular side effects are seen with topical agents
50. Adrenergic agonists
Mechanism of action aqueous outflow by both α and β
receptor stimulation, aqueous production due to stimulation
of α receptors
51. Classification and preparations
Non selective(α and β receptor stimulation)
1. Epinephrine(0.5%,1%,2%), BD dosage
2. Dipivefrine (0.1%) – prodrug of epinephrine, increased corneal panetration
α2 adrenergic agonists
Apraclonidine (0.5%,1%)BD-TDS dosage, used prophylactically for prevention
of IOP elevation following laser trabeculoplasty, YAG laser iridotomy and
posterior capsulotomy
Clonidine (0.125%,0.25%) BD dosage, centrally acting anti-hypertensive agent
Brimonidine(0.2%)BD-TDS dosage
Clinically, nonselective adrenergic agents have been replaced by α2 adrenergic
agonists because of their improved efficacy and side effect profile
54. Hyperosmotic agents
Mechanism of action plasma tonicity
osmotic gradient dehydrated the vitreous
Indications
To control acute episodes of elevated IOP
55. Preparations
1. Mannitol IV(20% solution1-2g/kg over 20-30 minutes), to be used
cautiously in hypertensives
2. Glycerol oral(50% solution1-1.5g/kg, mixed with equal amoount of
water or lime juice), to be used cautiously in diabetics as it is
metabolised to glucose
3. Urea IV – not recommended for routine use
4. Isosorbide – metabolically inert
57. Calcium channel blockers
Mechanism of action
• Might be due to its effects on secretory ciliary epithelium
Preparations
• Verapamil has been tried as 0.125 percent and 0.25 percent eyedrops
twice a day
Indications
• place in the mangement of patients with POAG, where miotics, beta-
blockers and sympathomimetics are all contraindicated
NEUROPROTECTIVE AGENTS
58. Argon or diode laser trabeculoplasty
Indications
1. Avoidance of polypharmacy(>2 preparations)
2. Avoidance of surgery
3. Primary therapy in patients with non-compliance to medical therapy
Mechanism of action outflow facility by causing shrinkage of
trabecular meshwork
59. Technique
40- 50 spots on the anterior
half of trabecular meshwork
over 180° using a gonioloens
Complications
1. Acute rise of IOP
2. Uveitis, haemorrhage, PAS
60. Surgical management
Indications
1. Uncontrolled glaucoma despite maximal medical therapy(3 drugs)
and laser trabeculoplasty
2. Failure of medical therapy and /or laser trabeculaplasty
3. Non-compliance to medical therapy and unavailability of laser
trabeculoplasty
4. Advanced disease requiring a very low target pressure may benefit
from early surgery
5. Primary line of treatment
62. Trabeculectomy
Creation of a fistula between the angle of anterior chamber and
sub-tenon’s space which allows egress of aqueous from AC to a
drainage bleb
63. Procedure
Conjunctival flap
Partial thickness scleral flap
Excision of trabecular tissue
Peripheral iridectomy
Closure using 10-0
monofilament sutures
Subconj inj dexamethasone
and gentamycin
64.
65.
66. Use of antimetabolites
5-fluorouracil
Mitomycin C
Originally advocated for patients with high risk like aphakia,
pseudophakia, neovascular glaucoma, H/O failed operations, now
also being used as a routinely by many surgeons
67. Complications of trabeculectomy
Post – op shallow AC
Hyphaema
Iritis
Cataract due to accidental injury to the lens
Endophthalmitis
68. OCULAR HYPERTENSION
Ocular hypertension or glaucoma suspect, either ofthese terms is used when a patient has an
IOP constantly more than 21 mm of Hg but no optic disc or visual field changes
Glaucoma suspect
Defined as an adult having normal open angle on gonioscopy and anyone of the following signs in at least one
eye
Elevated IOP
Suspicious disc changes
Visual field defects
High risk factors
Significant diurnal variation
Significantly positive water drinking provocative test
Splinter haemorrhages over or near the optic disc
IOP constantly more than 28 mm of Hg
Retinal nerve fibre large defects
Parapapillary changes
Central corneal thickness < 555 μm
Significant asymmetry in the cup size of the two eyes
family history
high myopia, diabetes or pigmentary changes in the anterior chamber
69. Treatment
Patients with high-risk factors should be treated on the lines of POAG
Patients with no high risk factors should be annually followed by examination
of optic disc, perimetry and record of IOP
70. • NORMAL TENSION GLAUCOMA
• The term normal tension glaucoma (NTG), also referred to as low tension
glaucoma is labelled when typical glaucomatous disc changes with or
without visual field defects are associated with an intraocular pressure
(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
• Clinical features
• IOP – NORMAL OR LOWER THEN 21
• OPTIC DISC CHANGES
• Visual field defects
• Differential diagnosis
1. HIGH PRESSURE GLAUCOMAS
• POAG
• GLAUCOMA with intermitent rise in iop
• Previous episodes of glaucoma
2. Non glaucomatous optic neuropathies
• Congenital optic disc anomalies
• Acquired optic neuropathies
71. • Treatment
• Medical treatment to lower IOP
• Trabeculectomy
• Systemic calcium channel blockers
• Monitoring of systemic blood pressure