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Abstract #24401 Published in IGR 11-3
Laser treatment of glaucoma: Evolution of laser trabeculoplasty techniques
Fea AM; Dorin GTechniques in Ophthalmology 2008; 6: 45-52
PURPOSE: To review the historical perspective and the evolution of the laser trabeculoplasty (LT) techniques clinically used for lowering intraocular pressure (IOP) with continuous wave (CW) 514-nm argon LT (ALT), CW 532-nm frequency-doubled Nd:YAG LT (fd Nd:YAG LT), CW 810-nm diode LT (DLT), Q-switched 532-nm frequency-doubled Nd:YAG LT (selective LT or SLT), and micropulse 810-nm diode LT (micropulse-diode LT or MLT). METHODS: Literature review, clinical, physical, and technical considerations. Result:The average IOP reduction reported with ALT, SLT, and MLT has been consistently comparable and appears to be more dependent on patients' factors (race, age, pigmentation, preoperative IOP, stage of glaucoma, and fellow eye response to laser) than on the LT technique/protocol. This supports the hypothesis that all forms of LT may share at least one common mechanism of action, which is likely the stress response to a laser-induced nonlethal injury with a cellular cascade initiated by cytokine expression and upregulation of matrix metalloproteinases (MMP-3). This process could not occur in trabecular meshwork (TM) cells destroyed by the laser but could only take place in still-viable TM cells injured but not killed by sublethal photothermal rise. Such nonlethal thermal elevation (ie, 5-10°C) is directly produced by the absorption of low-irradiance laser micropulses in MLT and indirectly derived by the thermal spread from the high temperature of the laser-induced "burn" in ALT or of the "microexplosion" in SLT's photothermolysis. CONCLUSION: Laser trabeculoplasty is a proven and effective IOP-lowering glaucoma therapy, whose usage however has been limited in the past by concerns over iatrogenic scarring of the TM. Argon laser trabeculoplasty, SLT, and MLT produce comparable IOP-lowering effects with different degree of TM tissue damage. The LT technique with the lowest level of tissue damage, of intraoperative discomfort, and of postoperative complications will eventually gain the preference of the ophthalmic surgeons, especially if administrable with a multipurpose laser without requiring the purchase of a special single-application laser device.
Dr. A.M. Fea, Istituto di Fisiopatologia Clinica, Clinica Oculistica dell' Universita di Torino, Via Juvarra 19, 10100 Torino, Italy. antoniofea@interfree.it
Classification:
12.4 Laser trabeculoplasty and other laser treatment of the angle (Part of: 12 Surgical treatment)
