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October 2, 2014

Overview of therapeutic strategy for glaucoma management

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There are many medical treatment options available for glaucoma.  When selecting a treatment, it is important to take into account efficacy, mode of action, safety, tolerability, contraindications, quality of life, adherence and cost.

Management algorithm for glaucoma medications

Recommendations

  • Assess each eye individually when selecting therapy
  • After diagnosis measure untreated intraocular pressure (IOP) more than once before initiating IOP-lowering treatment
  • If feasible, a therapeutic trial on one eye first may be useful to determine IOP lowering efficacy (unless very high IOP or advanced disease)
  • Always aim for the lowest possible dose
  • Involve patients in decision-making

Monotherapy

  • Prostaglandins/prostamides have been approved as first line treatment for several years. In spite of their cost, they are increasingly used as first choice treatment; reasons include:

a)   fewer instillations (once a day vs. twice daily)

b)   lack of relevant systemic side-effects

c)   IOP lowering efficacy

  • If  the  first  choice  monotherapy   does not appear to lower the IOP satisfactory or  is not  tolerated,  it  is  preferable  to switch to any of th eother topical agents that can be  initiated  as  monotherapy  before adding a second drug (see algorithm).
First choice treatment A drug that a physician prefers to use as initial IOP lowering therapy (see algorithm for first and second choice treatments).

First line treatment: A drug that has been approved by an official controlling body (i.e. EMEA) for initial IOP lowering therapy.

  • Meta-analyses are available for most of the drugs used for glaucoma (see Table 1 for comparative IOP reductions)

Table 1: lowering effect of topical IOP-lowering medications as determined by meta-analysis*

Active ingredient %IOP difference from baseline
Peak Through
Bimatoprost

Travoprost

Latanoprost

-33

-31

-31

-28

-29

-28

Timolol

Brimomidine

Betaxolol

Brinzolamide

Dorzolamide

-27

-25

-23

-20

-20

-26

-18

-20

-17

-17

* These meta-analyses do not include combination products or adjunctive therapy. Moreover,  while meta-analyses focus on IOP reduction, other aspects like patient characteristics, quality of life, side effects, convenience/compliance and cost effectiveness should be taken into consideration in making a drug therapy choice particularly when IOP differences between the compounds are small.

Rationale for adjunctive drug therapy

Evidence shows that monotherapy fails to achieve a satisfactory IOP reduction in 40-75%  of  glaucoma  patients  after more than two years of therapy.  While switching monotherapy should be attempted first,  there  are  cases  in  which  one  drug  is  inadequate  to  lower  a  patient´s  IOP  to  a  desirable target pressure and add-on therapy is then required.  Antiglaucoma eye drops can then be combined with each other, as well as added to laser and surgical treatments.

  • If  the  first  selected monotherapy  is  well  tolerated  and  effective,  but  not  sufficient  to  reach  the  target  IOP,  or  there  is evidence of progression and the target IOP is being reconsidered,  adjunctive therapy with any other topical agent can be initiated.
  • Use of β-blocker preparations with either  a prostaglandin/prostamide, a carbonic anhydrase inhibitor, pilocarpine or with brimonidine have been shown to be more effective at IOP lowering than the use of one of these drugs separately.
  • Drugs which belong to the same pharmacological group should not be used in combination (e.g. do not combine two prostaglandin derivatives or two beta-blockers) (see Table 2).
  • When  available,  fixed-combined  drugs  preparations  may  be  preferable  than  two  separate instillations of the same agents. A fixed combination may improve compliance and may reduce the daily amount of preservatives to which the eyes are exposed.

Table 2: Drug combinations – Additive effects

ADDITIONAL DRUG
CURRENT DRUG α2 agonists β blockers topical CAIs Cholinergic Prostaglandin/Prostamides
α2 agonists xxx + + + +
β blockers + xxx + + +
topical CAIs + + xxx + +
Cholinergic + + + xxx +/-
Prostaglandin/Prostamides + + + +/- xxx

CAI: Carbonic anhydrase inhibitor