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S. K. Charisis, I. Naoumidi, H. S. Ginis, M. K. Tsilimbaris; Transcleral Ciliary Body Photodynamic Therapy With Verteporfin in pigmented Rabbits : Hypotensive Effect and Morphologic Changes After 4 Retreatments. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3970.
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It is already known that transcleral ciliary body photodynamic therapy (PDT) with verteporfin has a significant but temporary hypotensive effect in animal models. The purpose of this study is to investigate both hypotensive effect and morphologic changes of the ciliary body in the eyes of normal pigmented rabbits after 4 consecutive retreatments.
Transscleral irradiation of the ciliary body was performed using light at a wavelength of 689 nm delivered via a 600µm core optical fiber with 40mW and 90sec application time. A first group of six pigmented rabbits received a bolus i.v. infusion of verteporfin at a dosage of 1mg/Kg 1 min prior to irradiation. A second group of other six pigmented rabbits were irradiated without verteporfin infusion and served as a control group. In both groups, one eye of each animal was treated and the fellow eye served as internal control. At each animal 10 consecutive laser applications were placed, covering 120 degrees in the upper-temporal limbal area and this procedure was repeated every 4 days, for a total of 4 retreatments. Daily IOP measurements were performed by means of the Tono-Pen XL (Medtronic Solan, Jacksonville Florida) applanation tonometer. The morphologic effect of PDT on the ocular structures was assessed at day 1 and 17 by light microscopy.
The mean IOP in treated eyes was significantly reduced compared to the control eyes in all rabbits of the study group. After the first treatment and at every retreatment, the hypotensive effect was present at 12 hours, was maximum at day 2 and 3 and attenuated at day 4, when retreatment was done. After the last retreatment, at day 17, the IOP returned to normal values. In all cases no adverse events were observed with the exception of minimal conjunctival oedema during the first 24 hours. The histologic exam showed that most of the ciliary body blood vessels in treated area were thrombosed 1 day after PDT. At day 17 normal structure of ciliary processes was maintained, with presence of local areas of thrombosed and normal vessels, small local areas of separation of inner and outer epithelial layer, a lot of mast cells full of pigmented granules and absence of scar tissue. No significant IOP reduction and morphologic alterations were observed in the study eyes of the control group rabbits.
Our findings suggest that transcleral ciliary body PDT results in short term hypotensive effect. The effect remains similar even after 4 consecutive retreatments.The effect on ciliary body morphology seems to be transient and reversible for this amount of retreatments.
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