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February 26, 2007
Prostaglandins such as latanoprost may decrease more than just IOP
Eyeworld Feb 2007
...A new study however, has found that latanoprost (0.005%), part of the family of prostaglandins, decreases anterior chamber depth (ACD) in patients with glaucoma or ocular hypertension after one month of treatment.Published in a recent issue of Investigative Ophthalmology & Visual Science, this study was a prospective, nonrandomized, auto-comparative trial comprising 40 eyes of 40 patients with glaucoma or ocular hypertension. Consuelo Gutiйrrez-Ortiz, M.D., Ph.D., Hospital Universitario Prнncipe de Asturias, Madrid, Spain, and colleagues measured ACD before and after one month of treatment with latanoprost using ultrasonography.They also measured ACD before and one hour after instillation of pilocarpine (2 %) both at baseline and one month after treatment with latanoprost. In addition, a control group comprising 20 eyes of 20 patients who did not receive latanoprost was analyzed to test the reproducibility of the ultrasonic measurements.
The mean IOP was lowered 34.7% after one month of treatment with latanoprost and did not affect visual acuity or lens thickness, the researchers reported.“We also found that the effect of topical pilocarpine on ACD after treatment with latanoprost is the same as before the therapy was started,” Dr. Gutiйrrez-Ortiz said in the study.The study authors reported consistent results with good reproducibility with the ultrasound device and also found the measurements of ACD and lens thickness on two repeated examinations in the same control eyes on separate days to be “virtually the same.”
“Based on these results, we believe that the differences found in the study group reflect real changes in the parameters analyzed,” Dr. Gutiйrrez-Ortiz said in the study.
The mechanics behind the alteration
The researchers postulated that latanoprost alters ACD by relaxing the ciliary zonules.“Some studies have shown that prostaglandins induce extracellular matrix remodeling by widening the intermuscular spaces along the longitudinal ciliary muscle bundles, fragmenting collagen types I and III, reducing the density and the branching of type IV collagen and laminin, and reducing the density of type III collagen,” Dr. Gutiйrrez-Ortiz wrote in the study.The study authors continued that collagen IV is also present in the human zonules while fibrillin-1 is a major component of the ciliary zonules and the zonular microfibrils are fragmented by the metalloproteinases.
“Thus, it makes sense that the structure and perhaps the dynamics of the ciliary zonules and the ciliary muscle could be modified by treatment with prostaglandin analogues,” Dr. Gutiйrrez-Ortiz wrote in the study.Because surgeons rely on zonules to hold intraocular lenses in place for 20 to 40 years, Dr. Robbins said it is important to understand these changes.“Are they resulting in just the relaxation of the zonules or is it a result of a weakening of the zonules so that [it] may be another risk factor for dislocated IOLs down the road or possibly increase the risk for vitreous loss at the time of surgery,” Dr. Robbins said.
Posted by mehdi khanlari at February 26, 2007 11:38 PM