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M. Pantcheva, J.Y. Yu, M.Y. Kahook, K. Lathrop, J.S. Schuman, R.J. Noecker; The Effect of Probe Placement on Endoscopic Cyclophotocoagulation Laser Energy Transmission . Invest. Ophthalmol. Vis. Sci. 2006;47(13):21.
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© ARVO (1962-2015); The Authors (2016-present)
Endoscopic cyclophotocoagulation (ECP) is used to treat refractory glaucoma by ablating ciliary processes (CP) using direct visualization during laser application. This study investigates the effect of the various distances of ECP probe placement on laser treatment.
An EndoOptiks® E2 laser equipped with a straight probe was set at 0.25 Watts. The Ophir Nova laser power meter was zeroed with a BSS filled test tube placed in direct contact with the meter’s detection head. After replacing the BSS with a Healon GV filled tube, laser power transmission was measured at six different distances: probe at the bottom of the tube (0 mm), 1 , 2 , 3 , 4 and 5 mm away from the power meter. Measurements were repeated five times and averaged. The results were analyzed with an ANOVA test. Next, measurements of probe placement were performed in a human cadaver eye to establish the anatomical relevance of probe position. Recordings were made, making note of the number of processes visible, at each set distance.
There was a gradual decrease in transmission of laser energy as the probe distance increased from the bottom of the tube. The decrease in energy was minimal between the 0 and 2 mm positions. However, energy dissipation increased significantly after 3 mm. The extent of structures seen through the endoscope ranged from 4 ciliary processes at 1 mm to 13 at 5 mm.
This study illustrates that the distance between treated tissue and the ECP probe should be kept at a maximum of 2 mm in order to preserve the intended laser energy setting. The surgeon can use the number of CPs in the view provided by the probe to gauge the distance in the eye.
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