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Quantification of holmium: YAG and thulium: YAG laser-induced scleral shrinkage for buckling procedures
1Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami School of Medicine, FL 33136, USA.
Background And Objective:
To quantify and compare holmium:YAG (2.1 microns) and thulium:YAG (2.0 microns) laser-induced scleral shrinkage for retinal buckling procedures.
Materials And Methods:
Two overlapping spots of either laser radiation were applied at the equatorial sclera of 50 human cadaver eyes. Scleral shrinkage was expressed as a relative change of length between two reference points on the scleral surface, and quantified as a function of energy per pulse, total energy, scleral thickness, and intraocular pressure (IOP). Tissue effects were studied histopathologically.
Results:
Shrinkage was most dependent on total fluence and attained a maximum of 27% to 30% with an IOP of 4 mm Hg, regardless of scleral thickness or laser parameters, but decreased with increasing IOP. The thulium:YAG laser produced more efficient scleral shrinkage and less collagen damage than the holmium:YAG laser.
Conclusion:
The recommended parameters for laser-induced scleral shrinkage are the thulium:YAG laser, with 2.4 J/cm2 per pulse and 12.0 to 14.4 J/cm2 total fluence (5 to 6 pulses). IOP control (< or = 4 mm Hg) is crucial during laser scleral buckling.