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Editors Selection IGR 8-3
Laser treatment: ALT effect on latanoprost
Comment by Mark Latina on:
14020 Effect of previous argon laser trabeculoplasty on the ocular hypotensive action of latanoprost, Arranz-Marquez E; Teus MA, Graefe's Archive for Clinical and Experimental Ophthalmology, 2006; 244: 1073-1076
Arranz-Marquez and Teus (865) designed a prospective observer-masked study to compare the effect of prior argon laser trabeculoplasty (ALT) on the ocular hypotensive effect of latanoprost in patients with primary open angle glaucoma who had never been treated with a prostaglandin analogue. The results of this study indicate that ALT treated eyes have less of a hyptotensive response to latanoprost than those who have not been treated with ALT.
The control group consisted of 43 newly diagnosed glaucoma or patients where treatment was considered ineffective or not well tolerated without prior ALT, and the study group (43 eyes) had undergone ALT, 180 degrees of treatment, by the same glaucoma specialist at least 1 year prior to inclusion in the study. Basal IOPs were matched in the study and control groups. Patients on medications underwent a 3-week washout before basal IOP was determined.
ALT treated eyes have less of a hyptotensive response to latanoprost than those who have not been treated with ALT
Basal IOPs were 22.4 &plm; .3 mmHg in each group. IOP's measured at 1 month and 3 months following initiation of treatment showed similar IOP reductions of 25-29% in the control group and 17-19% for the ALT treated eyes (p = 0.03). At 3 months, the control group had a smaller standard deviation of 2 mmHg or 12% versus the ALT treated group, which was 4 mmHg or 19%.
The authors point out that while a previous study (Patelska B, Am J. of Ophth 1997) showed that there was no association between previously ALT and the hypotensive effect of latanoprost, in that study the patients were receiving maximum tolerated medical therapy and therefore not the best candidates to evaluate the efficacy of a single drug. The strength of this study is that all patients on medications underwent a washout period prior to starting latanoprost. While the authors do not point out any study limitations, they do not identify how many patients in each group would be considered primary therapy and it is not clear whether ALT was used as primary therapy in any of the patients studied. Also, they did not supply any information regarding number of pre-treatment medications in each group.
The authors consider that "ALT and the prostanoid drugs share, in part, the same mechanism of action, thus accounting for the lower efficacy of latanoprost in ALT-treated eyes." While this is a plausible explanation for the results obtained based on activation of MMPs by both therapies, the effects of other medications on the hypotensive effect of either ALT or latanoprost cannot be discounted based on the information supplied in this study. The study does not provide any information as to the best hypotensive agents in patients with prior ALT, although the authors suggest that prior ALT should be taken into account when selecting "the best hypotensive drug to prescribe in a particular case."
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