Page 49 - CJO_F17_GLAUCOMA_SUPPLEMENT

MANAGING OPEN ANGLE GLAUCOMA

Table 8: Setting Target IOP Based on Stage of Glaucomatous Damage
Stage disease Suggested initial target pressure Consider lowering an additional 10% if:

• <50 years of age
Mild damage 20-30% lowering • African North American descent
• Sibling with advanced glaucoma
Moderate damage 30-40% lowering
Severe damage 40-50% lowering

Clinical Recommendations for setting target pressure:
• Gather sufficient data to determine the baseline pressure
(4 to 6 readings may be preferred; minimum of 3 with two as early in the morning as possible).

• Set a target IOP informed by the landmark trials based on stage of disease.

• Clearly document this value in the record, and reconsider when appropriate.

CHOOSING A THERAPY
The initiation of medical intervention in the treatment of glaucoma should not be taken lightly. Once treatment is
started it is normally maintained for life. When deciding on an intervention, the following components should be
among the general considerations: awareness of the efficacy, benefits and risks of the treatment; the frequency of
adverse effects and development of intolerance to the treatment; the many factors contributing to individual adher-
ence to therapy and risks for non-adherence; and the ability to conduct regular follow-up.
For many years, the monocular drug trial was employed in an attempt to assess treatment efficacy, comparing a
treated to an untreated eye to differentiate therapeutic IOP change from spontaneous fluctuation. The legitimacy
310
of this comparison depends upon a number of assumptions, including that each eye fluctuates symmetrically, that
fluctuations are repeatable, and that short-term response to treatment in one eye can accurately predict that of both
eyes in the long-term. Recently, however, investigators have questioned the validity of these assumptions. current
best practice is to obtain a number of pre- and post-treatment IOP measurements to establish a solid baseline and
assess the impact of therapy on both eyes. 311,312

While laser trabeculoplasty was initially considered as a treatment alternative to delay incisional surgery, more
recently, selective laser trabeculoplasty (SLT) has been shown to be a viable first-line treatment for glaucoma. 304,313
Indeed, not only does SLT demonstrate a good safely profile, and eliminate exposure to preservatives and the need
for adherence to a treatment regimen, it also shows one-year data on efficacy that is comparable to that of the pros-
taglandin analogue group of medications. One of the main drawbacks is the short-term efficacy of the procedure;
313
however, there is evidence suggesting that certain individuals, including those with initial high IOP and those who
responded well to the first procedure may benefit from repeat SLT. 314,315 Newer forms of laser trabeculoplasty are
being investigated with a view to reducing adverse effects.
316
In the majority of cases, monotherapy with a prostaglandin analogue will be the first-line treatment. The decision
to start a prostaglandin analogue is based on their superior efficacy, safety and tolerability profile. Due to their sys-
temic adverse effects, beta-blockers, while still considered first-line treatment, are generally not used before prosta-
glandin analogues unless the latter are ruled out due to contraindications/cautions or patient preference. Appendix
2 reviews and compares the classes of commonly used glaucoma medications available in Canada.

Prior to prescribing any medication and periodically thereafter, consulting the CPS (Compendium of Pharmaceu-
ticals and Specialties) via their web portal is recommended to ensure that contemporary prescribing information is
reviewed, including indications, contraindications, cautions, dosing, adverse effects and interactions [see: https://
www.pharmacists.ca/products-services/compendium-of-pharmaceuticals-and-specialties/ ].

CANADIAN JOURNAL of OPTOMETRY | REVUE CANADIENNE D’OPTOMÉTRIE VOL. 79 SUPPLEMENT 1, 2017 49