Glaucoma Medical Treatment
Table 1: Mechanism of Action, Number of Daily Instillations and Main Side Effects of Medications Commonly Used to Lower Intraocular Pressure4
Beta-receptor blockers
Timolol 0.1 %; 0.25 %; 0.5 % Levobunolol 0.25 %; 0.5 %
Carteolol 1 %; 2 % Betaxolol 0.25 %; 0.5 %
Prostaglandin F2 alpha analogues Latanoprost 0.005 % Travoprost 0.004 % Bimatoprost 0.03 % Tafluprost 0.0015 % Unoprostone 0.15 %
Carbonic anhydrase inhibitors Dorzolamide 2% Brinzolamide 1%
Acetazolamide 250 mg tablet, 500 mg intravenous injection
Selective alpha 2-receptor agonist Brimonidine 0.15 %; 0.2 % Parasympathomimetics Pilocarpine 1 %; 2 %
Mainly suppression of aqueous humour production
Increase of trabecular outflow
Table 2: Efficacy of Various Drugs Frequently Used to Lower Intraocular Pressure to Treat Open-angle Glaucoma (Monotherapy Data)4
IOP-lowering Ingredient
Bimatoprost 0.03 % IOP Reduction (%) Compared to the Untreated
Baseline IOP Peak Effect 33
Latanoprost 0.005 % 31 Travoprost 0.004 % Tafluprost 0.0015 % Timolol 0.5 % Betaxolol 0.5 %
Brimonidine 0.2 % Dorzolamide 2 % Brinzolamide 1 %
IOP = intraocular pressure.
or at least daytime IOP phasing to identify IOP spikes, mean diurnal IOP and diurnal IOP fluctuation. If previous visual field test results are available, it is very useful to calculate the progression rate for mean defect (MD) in dB/year on no treatment or on the previous and current treatments.4
If the progression rate is not controlled,
treatment intensification is needed. For example, for an eye with an MD of -5.5 dB (relatively early damage level) that shows a 1 dB/year MD progression rate, only one decade is necessary to deteriorate to -16 dB MD (severe damage level), and thus early and effective intervention is needed to reduce the progression rate.
Which Features of Intraocular Pressure are Important?
It is not easy to use IOP information. The measurement frequency (IOP sampling) is necessarily small compared to the true IOP continuum even if a 24-hour IOP curve is obtained. Clinical studies strongly suggest that in eyes with elevated IOP, the mean IOP (the
124
31 31 27 25 23 20 20
Trough Effect 28 29 28 28 26 18 20 17 17
2 to 3 times daily 3 to 5 times daily
Increase of uveoscleral aqueous humour outflow
Once daily (twice daily for unoprostone)
Increased periocular pigmentation, eyelash changes, conjunctival
hyperaemia, irreversible darkening of the iris, exacerbation of herpetic uveitis, cystoid macula oedema when
other risk factors of cystoid macula oedema are present
Suppression of aqueous humour production
2–3 times daily Twice daily
1–2 tablets or injections per day
Systemic administration: acute agranulocytosis, anaemia,
thrombocytopenia; paraesthesia, gastrointestinal complaints,
fatigue, depression Topical administration: bitter-taste feeling
Fatigue, lethargy or transient coma in newborns and young children Miosis, myopic shift of vision formation of posterior synechia
mathematical average of the individual time-point IOP values) is a good measure of the clinically important features of IOP.7,8
Mechanism of Action Suppression of aqueous
humour production
Number of Daily Administrations Once or twice daily
Main Side Effects
Manifestation/worsening of bronchial asthma, bradycardia, heart failure, sexual dysfunction, depression
The role of
diurnal IOP fluctuation may represent a separate risk for glaucoma progression in such eyes. However, when a clinically significant medical or surgical IOP reduction is achieved, the mean IOP value is well controlled and in the low teens, the significance of long-term (between visits) IOP fluctuation increases considerably.8–11
Thus, the
general principle is to intervene early, reduce both mean IOP and IOP fluctuation and continuously monitor the visual field, the optic nerve head and the retinal nerve fibre layer for progression or stability (which is not equal to missed progression).
How to reach this goal? There are six key issues to the success:
• selection of appropriate monotherapy; •
•
selection of appropriate combination therapy when monotherapy is not enough;
use of fixed-combination drugs when available and the usefulness of the individual components is verified;
• if available, the use of drops not preserved by benzalkonium chloride (non-BAK) for long-term treatment;
• •
evaluation and support of the patient’s compliance (adherence) to the prescribed therapy; and
introduction of laser or filtering surgery when the IOP reduction achieved with medical therapy is insufficient.
Selection of Monotherapy
Except for cases with very high IOP and advanced structural and functional damage at the time of diagnosis (when rapid and functionally significant progression may occur), the recommendation is to start IOP-lowering medication monotherapy.4
The advantage of this approach
is that many patients are well-controlled on monotherapy and combined therapy increases the risk for side effects and frequently reduces the adherence of the patient. A classification of the various
EUROPEAN OPHTHALMIC REVIEW
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