Dr.
Kiran’s Success Learning Forum
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Management of Glaucoma
- Dr. Kiran Vakade
Introduction:
Glaucoma: It is a disorder associated with optic nerve damage resulting in vision loss.
Increased intraocular pressure (>21 mm of Hg) is one of the most important risk factor for
glaucoma.
Glaucoma can permanently damage vision in the affected eye, first by decreasing peripheral
vision (reducing the visual field), and then potentially leading to blindness if left untreated
Types of glaucoma
1. Open angle glaucoma/ wide angle glaucoma/ Chronic simple glaucoma.
2. Angle closure glaucoma/Narrow angle glaucoma/ Acute congestive glaucoma
1. Open angle glaucoma/ wide angle glaucoma/ chronic simple glaucoma.
It is the most common type of glaucoma.
Pathophysiology: it is a genetically determined degenerative disease of the eye affecting
patency of trabecular meshwork. Patency of it gradually lost past middle age. Hence drainage
of aqueous humor decreases resulting in increase in IOP.
Iridocorneal at angle is not affected in this type of glaucoma
IOP rises slowly and progressively.
It has no symptoms until the disease has progressed significantly.
Treatment of choice : Ocular hypotensive drugs
2. Angle closure glaucoma/Narrow angle glaucoma/ acute congestive glaucoma
It occurs in individuals with a narrow iridocorneal angle and shallow anterior chamber.
The i.o.t. remains normal until an attack is precipitated, usually by mydriasis.
The i.o.t. rises rapidly to very high values (40–60 mmHg).
It is an emergent condition with marked congestion of eyes and severe headache.
Failure to lower i.o.t. quickly may result in loss of sight.
Definitive treatment is surgery.
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Classification of drugs useful in the management of glaucoma:
A. Drugs acting on cholinergic system (Miotics)
1. Cholinergic agonists: Pilocarpine
2. Anticholinesterase Drugs: physostimine
B. Drugs acting on adrenergic system:
1. β antagonists: Timolol, Betaxolol, Levobunolol
2. α agonists: Dipivefrine, Apraclonidine, Brimonidine
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C. Prostaglandin Analogues : Latanoprost, Travoprost, Bimatoprost
D. Carbonic anhydrase inhibitors: Actazolamide, Brinzolamide, Dorzolamide
E. Osmotic agents: Hypertonic manitol (20%), Glycerol (10%)
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1. Drugs acting on cholinergic system (Miotics)
Till 1970’s considered as the drug of choice.
Because of several drawbacks, now a day’s these are considered as the last option.
Drawbacks of Miotics:
Diminution of vision in dim light and in patients of cataract.
Headache/ Bow pain
Induce myopia.
Fluctuation in IOP
6-8 hr administration is needed
Systemic adverse effects at high doses: Nausea, diarrhoea, sweating and bronchospasm
Mechanism of action:
In open angle glaucoma: they improve ciliary muscle tone (contraction) pulls ciliary
muscle towards lens improves patency of trabeculae decrease IOP by increasing
drainage
In narrow angle glaucoma: Miotics Contraction of sphincter pupillae muscle changes
the direction of forces in iris to lessen its contact with lens and spreads the iris mass
centrally Pupillary block is removed and narrow iridocorneal angle is corrected.
How mydriasis precipitates attack of glaucoma and how are miotics useful in narrow angle
glaucoma?
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2. β adrenergic blockers
examples : topical beta blockers: Timolol, Betaxolol, Levobunolol
Topical β blockers have been the first line drugs till recently, but PG F2α analogues are the
preferred drugs now.
They are as effective as miotics and produce less ocular side effects.
Advantages of β blockers over Miotics:
1. No change in the pupil size: no diminution of vision in dim light and in patients
with cataract.
2. No induced myopia which is usually troublesome in young patients.
3. No headache and bow pain due to persistent spasm of iris and ciliary muscle.
4. No fluctuation in IOP as occur with pilocarpine drops
5. Convenient: twice/once daily application is sufficient
Mechanism of action:
β blockers responsible for decrease in aqueous humor secretion from ciliary body by
inhibiting β2 adrenergic receptors present on the ciliary epithelium.
Betaxolol have additional Ca++ channel blocking property on retinal neurons.
Adverse effects:
Ocular adverse effects: Allergic blepharoconjuctivitis, Blurred vision, Corneal
hypoesthesia, Dryness of eyes, Redness, Stinging sensation (ABCD-RS)
Systemic adverse effects: Bradycardia, Broncoconstriction, Metabolic adverse effects
etc.
Note: Systemic adverse effects of β blockers can be minimised by applying mild pressure at
the inner canthus of the eye for about 5 min after instilling the eyedrop to prevent entry of
the drug into nasolacrimal duct from which drug is mainly absorbed into systemic
circulation.
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3. α adrenergic agonists: Dipivefrine, Apraclonidine, Brimonidine
MOA : These are effective by decreasing aqueous humor secretion as well as by increasing
aqueous humor drainage
Considered as 3rd / 4th choice now a days.
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4. Prostaglandin analogues:
Examples: Latanoprost, Travoprost, Bimatoprost
Because of good efficacy, once daily application and absence of systemic complications, PG
analogues have become the first choice drugs for open angle glaucoma.
High cost is a disadvantage
Mechanism of action: Low concentration of PGF2α was found to lower i.o.t without
inducing ocular inflammation. It acts by increasing uveoscleral outflow, possibly by
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increasing permeability of tissues in ciliary muscle or by an action on episcleral vessels. An
effect on trabecular outflow has also been demonstrated, but is less marked
Adverse effects:
Ocular irritation, pain, blurring of vision, increase iris pigmentation, darkening of
eyelashes, macular oedema
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5. Carbonic anhydrase inhibitors:
Acetazolamide is used orally while brinzolamide and dorzolamide are used by topical route.
MOA: By inhibiting carbonic anhydrase enzyme these drug inhibits bicarbonate synthesis
which is important constitute of aqueous humor. Hence aqueous production decreases.
Adverse effects: Hypokalemia, Acidosis, Parasthesia
3rd/4th choice drug in open angle glaucoma.
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6. Osmotic diuretics:
Examples: Manitol , GLycerol
These drugs due to their osmotic nature increases drainage of aqueous humor.
Mainly used in angle closure glaucoma
High dose is required.
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Current approach in the treatment of open angle glaucoma:
Start monotherapy with latanoprost or a topical beta blocker; if target i.o.t. is not attained,
either change over to the alternative drug or use both the above concurrently.
Brimonidine/dorzolamide (occasionally dipivefrine) are used only when there are
contraindications to PG analogues and/or beta blockers, or to supplement their action.
Topical miotics and oral acetazolamide are added only as the last resort.
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Management of Angle closure glaucoma:
1. Hypertonic mannitol (20%) 1.5–2 g/kg or glycerol (10%): infused i.v. decongests the
eye by osmotic action. A retention enema of 50% glycerine is also sometimes used.
2. Acetazolamide: 0.5 g i.v. followed by oral twice daily is started concurrently.
3. Miotic:
4. Once the i.o.t. starts falling due to the above i.v. therapy, pilocarpine 1–4% is instilled
every 10 min initially and then at longer intervals.
5. Contraction of circular muscle (sphincter pupillae/ constrictor pupillae) changes the
direction of forces in the iris to lessen its contact with the lens and spreads the iris mass
centrally pupillary block is removed and iridocorneal angle is freed .However, when
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i.o.t. is very high, the iris muscle fails to respond to miotics; tension should be reduced
by other measures before miotics can act.
6. Topical beta blocker: Timolol 0.5% is instilled 12 hourly in addition.
7. Apraclonidine (1%)/latanoprost 0.005% instillation may be added.
8. Definitive treatment is surgery or laser iridotomy.
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Name of drug/class Aqueous secretion Trabecular outflow Uveoscleral outflow
β blockers Decrease due to
(Timolol, blockade of β2
Betaxolol, receptors present of - -
Levobunolol) ciliary epithelium
Carbonic anhydrase Decrease by
inhibitors inhibiting
(Acetazolamide, bicarbonate synthesis
- -
Brinzolamide, which is important
Dorzolamide) constituent of
aqueous humour
Cholinergic drugs In POAG: Increase
:Miotics due to contraction
(Pilocarpine, of ciliary muscle
Physostigmine) towards lens
In angle closure
glaucoma:
trabecular outflow
is increased due to
removal of pupillary
block.
Prostaglandins Increase (Prominent
(Latanoprost, action/ Main Action)
Bimatoprost, possibly by increasing
Travoprost) Increase permeability of the
tissues in ciliary muscle
or action on episcleral
vessel
α2 agonists Decrease due to
(Apraclonidine/ agonist action on α2
Increase
Brimonidine) receptor present of
ciliary epithelium
Nonselective Decrease due to
adrenergic drugs agonist action on α2
( Dipivefrine) receptor present of
ciliary epithelium and
Increase Increase
due to
vasoconstriction of
ciliary blood vessel
through α1 action
