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S. R. Babighian, E. Chen, A. Galan, P. Montan; Effect of Pneumatic Trabeculoplasty on Ocular Structures in a Rabbit Model. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4193. doi: https://doi.org/.
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To evaluate the histologic ocular findings after Pneumatic trabeculoplasty (PNT) in a rabbit model. Intraocular pressure (IOP) was also evaluated.
Animal Care Committee approval at St: Eriks Eye Hospital of Karolinska Institutet was obtained. Fourteen albino New Zealand white rabbits were treated with PNT (Ophthalmic International, Coronado Industries, Fountain Hills, AZ) in one eye randomly chosen while the fellow eye was used as control. All rabbits underwent a single PNT treatment on day 0 (baseline) and, after 7 days, only seven rabbits received a second PNT in the eye previously treated. A single PNT treatment included the vacuum application of 60 seconds and 5 minutes rest period followed by another equal vacuum application. Before and at specific time-points after PNT (day 1, 7, 14, 30) clinical signs as conjunctival redness and corneal transparency were assessed and tonometry was performed. The mean of three readings of Icare® (Tiolat Oy, Helsinki, Finland) was recorded for each eye. Eyes were harvested 1 month after PNT. Formalin-preserved specimens from eyes were embedded and serially sectioned sagittally and then tangentially. All the sections were treated with staining including H&E, Van Gieson’s technique, smooth muscle actin immunolabel and elastin stain.
No significant differences in IOP were evident between the eye treated with PNT and control eyes. Histologic data were collected from all rabbits but in one case the damage due to manipulations made the sample not analyzable. Light microscopy did not evidence any sign of inflammation, vascular alterations, oedema, tissue scarring or necrosis. Compared with the control group, eyes submitted to PNT showed a significant reduction of the corneal thickness in 7 (53.8%) cases (p<0.008) and a thinning of the ciliary body in 8 (61.5%) cases (p<0.0003). About the anterior chamber angle and the lens thickness, no significant differences in size between treated and not treated eyes were detected.
To our knowledge, this is the first histologic study of eyes treated with PNT. Several papers about the IOP lowering effect induced by PNT in glaucomatous patients have been reported but the mechanism of action has been only hypothesized. Our study supports the mechanical theory ascribing to PNT a "stretching effect" on the trabecular meshwork thus increasing the outflow of the aqueous without widening of the uveoscleral pathway.
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