Pigmented Trabecular Meshwork Cells Research Articles

Augendrucksenkung nach selektiver Lasertrabekuloplastik (SLT) mit zwei unterschiedlichen Lasersystemen und nach Argonlasertrabekuloplastik (ALT) - Eine kontrollierte prospektive klinische Studie an 284 Augen

Selective laser trabeculoplasty (SLT) is a new method to reduce intraocular pressure in eyes with primary open angle glaucoma. The laser parameters of a Q-switched, frequency-doubled Nd:YAG-laser are set to selectively target pigmented trabecular meshwork cells without visible damage to the adjacent non-pigmented tissue. SLT acts non-thermally, the intracellular microdisruptions triggered by the laser are confined to the targeted cells, the laser pulses are so short that heat caused within the targeted cells does not have time to spread to the surrounding tissue. A controlled prospective randomised clinical study was conducted to compare the long-term results, safety and efficacy after SLT with two different laser systems and after ALT in the treatment of ocular hypertension and medically uncontrolled open angle glaucoma. About two years ago the authors performed a selective laser trabeculoplasty in 119 eyes using the SLT laser unit Otello (Glautec AG, ARC, EC), here named as SLT-I, and in 124 eyes using the SLT laser unit Selecta II (Lumenis, Palo Alto, CA), here named as SLT-II. In 41 eyes the authors performed argon laser trabeculoplasties using the argon laser Argus (Aesculap Meditec, EC). Two months after treatment mean IOP reduction from baseline was 1.9 mmHg or, respectively, 8.8 % after SLT with the SLT-System I, 2.0 mmHg or, respectively, 9.5 % after SLT with SLT-System II, and 2.2 mmHg or, respectively, 9.9 % after ALT with the argon laser. Twelve months after LTP mean pressure reductions were 1.7 mmHg (7.9 %) after SLT-I, 1.8 mmHg (8.5 %) after SLT-II, and 2.1 mmHg (9.4 %) after ALT. The response curve of the eyes with SLT-I greatly resembled that of the eyes with SLT-II and those eyes with ALT. Pressure reduction was highest after ALT, followed by SLT-II, in SLT-I reduction was the least, but the differences were not significant. Our findings did not correspond with those of other authors reporting an average IOP reduction of 25 % after SLT and ALT. SLT has shown reasonable efficacy in lowering IOP in eyes with ocular hypertension and primary open angle glaucoma, SLT achieves about the same level of IOP reduction compared with ALT. As a result of the preservation of the structure of the trabecular meshwork and low rate of complications, SLT is a safe alternative to ALT. The exact biological effect induced with SLT is still not yet understood. For the early glaucoma stages SLT provides an alternative to drug treatment, for the advanced glaucomas SLT is an additional option for further pressure reduction. More long-term follow-up studies are needed to determine whether the IOP lowering effect is sustained over time, and to assess the efficacy of repeated SLT.

Langzeitergebnisse nach selektiver Lasertrabekuloplastik - eine klinische Studie an 269 Augen

Selective laser trabeculoplasty SLT is a new method to reduce intraocular pressure in eyes with primary open angle glaucoma. With a Q-switched, frequency-doubled Nd:YAG laser it targets the pigmented trabecular meshwork cells without visible damage to the adjacent non-pigmented tissue. SLT acts non-thermally, the intracellular microdisruptions triggered by the laser are confined to the targeted cells, the laser pulses are so short that heat created within the targeted cells does not have time to spread to the surrounding tissue. A clinical prospective study was conducted to evaluate the long-term results, safety and efficacy of SLT in the treatment of open angle glaucoma. Since 2002, we have performed a selective laser trabeculoplasty in 269 eyes: in 17 eyes with ocular hypertension, in 239 eyes with primary open angle glaucoma, in 11 eyes with low tension glaucoma, while 2 eyes had a secondary glaucoma due to uveitis. In 22 eyes the primary initial treatment was SLT. Three months after treatment, the mean IOP reduction from baseline was 3.4 mm Hg, respectively 15 %, after 12 months the mean IOP reduction was 3.0 mm Hg (12.9 %), and after 24 months 2.7 mm Hg or 12.1 %. The response curve of the eyes with ocular hypertension greatly resembled the eyes with primary open angle glaucoma and with low tension glaucoma. SLT has shown reasonable efficacy in lowering IOP in eyes with primary open angle glaucoma and ocular hypertension, both as a first-line treatment and as a treatment in medication-refractory eyes. SLT is effective for patients who have had prior treatment with ALT. Long-term follow-up studies are needed to determine whether the IOP lowering effect is sustained over time, and to assess the efficacy of repeated SLT. The exact biological effect induced with the SLT is still not understood.

Immediate intraocular pressure response to selective laser trabeculoplasty

BACKGROUND/AIMSSelective laser trabeculoplasty targets the pigmented trabecular meshwork cells without damage to the trabecular meshwork architecture in vitro. A study was conducted in vivo of eight eyes with uncontrolled open...

Selective targeting of trabecular meshwork cells: In vitro studies of pulsed and CW laser interactions

The purpose of the present study was to selectively target pigmented trabecular meshwork cells without producing collateral damage to adjacent non-pigmented cells or structures. The ability to selectively target trabecular meshwork cells without coagulation, while preserving the structural integrity of the meshwork, could be a useful approach to study whether the biological response of non-coagulative damage to the trabecular meshwork and trabecular meshwork cells is similar to that seen with coagulative damage to the trabecular meshwork which occurs with argon laser trabeculoplasty. This approach also may be useful to non-invasively deplete trabecular meshwork cells while preserving the structural integrity of the trabecular meshwork in an animal model. A mixed cell culture of pigmented and non-pigmented trabecular meshwork cells were irradiated with Q-switched Nd-YAG and frequency-doubled Nd-YAG lasers, microsound pulsed dye-lasers, and an argon ion laser in order to define a regime where laser absorption would be confined to pigmented trabecular meshwork cells, thereby permitting selective targeting of these cells without producing collateral thermal damage to adjacent non-pigmented cells. Pulse durations ranged from 10 nsec to 0.1 sec. A fluorescent viability/cytotoxicity assay was used to evaluate laser effects and threshold energies, and cells were examined morphologically by light and TEM. Selective targeting of pigmented trabecular meshwork cells was achieved with pulse durations between 10 nsec and 1 microsec and 1 microsec without producing collateral thermal or structural damage to adjacent non-pigmented trabecular meshworks cells when examined by light and transmission electron microscopy. Pulse durations greater than 1 microsec resulted in non-selective killing of non-pigmented trabecular meshwork cells. Threshold radiant exposures were as low as 18 mJ cm-2, and increased at longer wavelengths, longer pulse durations and lower melanin contents within the cells. It is concluded that selective targeting of pigmented trabecular meshwork cells can be achieved using pulsed lasers with low threshold radiant exposures avoiding collateral thermal damage to adjacent non-pigmented trabecular meshwork cells. This approach can be readily applied in vivo.