International Glaucoma Review

The Journal for the World Glaucoma Association

 

Pharmacological treatment for glaucoma

Patient education

In the field of pharmacological treatment, a poster by Silverstein et al. reported a multicentre, evaluator-masked study in 64 patients to evaluate the effect of patient education on acceptance of hyperaemia associated with bimatoprost therapy for glaucoma and ocular hypertension (OHT). A fact sheet was used to explain the importance of IOP reduction and treatment efficacy to the first group of patients, whereas instructions to instill the treatment twice a day were given to the second group. The findings showed that hyperaemia peaked one day after treatment started, and continued to decline throughout the study, Despite this decline, Group 2 was more bothered by hyperaemia, compared with Group 1. Group 1, more aware of the importance of IOP-lowering, was more likely to be willing to continue the treatment. It can be concluded that:

  • Patient compliance is a major issue in glaucoma treatment
  • Patient education can potentially improve patient compliance and treatment outcomes

 

Ocular surface

More insights into the effects of topical anti-glaucoma medications on ocular surface were given in a poster by Okada et al. These authors evaluated by the expression pattern of the tress-related genes c-fos, c-jun and COX-2, which is only minimal in uninjured rat corneal epithelium. Immunohistochemistry and in situ hybridization were used to detect the expression of these genes in the ocular surface of eyes from 52 rats, 3060 minutes after application of topical glaucoma medications (0.5% timolol, 0.005% latanoprost or 0.12% unoprostone) or the preservative benzalkonium chloride (BAK) (0.005%, 0.01% or 0.02%). Expression of the first two genes was detected in the corneal epithelium after application of all three medications and the higher concentration of BAK, and was more marked with the prostagandins (PGs) compared with timolol. COX-2 transcriptional signals were detected in the corneal and conjunctival epithelium after application of the PGs, but not that of timolol or BAK. These findings show that:

  • Early activation of corneal and conjunctival cells occurs following topical IOP-lowering medications
  • The effect of prostaglandins seems more marked than that of timolol
  • The expression of COX-2 indicates that an inflammatory process may be involved

 

Asymmetry IOP response

The findings of a study by Rai et al. bear relevance to the accuracy of monocular IOP measurements in clinical trials. They suggested an asymmetry in the responses of the left and right eyes to intraoc-ular pressure (IOP)-lowering monotherapy. IOP was measured over 24 hours by pneumatonometry in 34 untreated OHT and glaucoma patients before, and four weeks after, treatment with travoprost or timolol. Mean baseline IOPs and mean IOP changes in response to treatment were determined, and the strengths of the association between the left and right eyes were evaluated. A weak-to-moderate association was found between the response of the left eye and that of the right eye to treatment, although a better association was obtained for timolol. Thus:

  • Findings from therapeutic trials involving one eye of each subject are not predictive of the fellow eye
    Therapeutic trials involving both eyes of each subject would be preferable

 

Treatment after cataract surgery

The efficacy of latanoprost (0.005%) and timolol (0.5%) in the early post-operative period after cat-aract surgery was evaluated by Varavka et al. In this prospective, randomized, double-masked study in 80 patients with unoperated glaucoma, both treatments reduced IOP post-surgically. However, seven days after cataract surgery, a significantly (P < 0.05) lower mean IOP was found in patients treated with latanoprost (17.68 0.3 mmHg) compared with those administered timolol (21.18 0.53 mmHg). Surgery-associated inflammation in the anterior chamber was observed in both patient groups, and resolved within a few days. The outcomes of this study indicate that:

  • The PG is as safe as the beta-blocker after cataract surgery in glaucoma patients
  • The PG exerts a more pronounced hypotensive effect than the beta-blocker, irrespective of surgery-associated inflammation in the anterior chamber

 

IOP control

It is generally agreed that more than one IOP-low-ering agent is needed to control IOP effectively in about 50% of patients. Various agents with different mechanisms of action have been investigated for their potential use in combination therapies. A study by Oltmanns et al. was conducted in a rat ocular hypertensive model to investigate the IOP-lowering effect of the combination of timolol and cannabinoids. The results showed that:

  • Compared with single agents, the combinations of timolol + cannabinoids led to a more prolonged and pronounced IOP reduction
  • No ocular or systemic side effects were caused by the combinations
  • Interestingly, combining two cannabinoids also produced a synergistic IOP-lowering effect
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