Abstract
Purpose: :
To evaluate predictive factors for intraocular pressure (IOP) reduction with selective laser trabeculoplasty (SLT) treatment in patients with medically uncontrolled glaucoma.
Methods: :
A total of 185 eyes of 143 patients with open-angle glaucoma were included. All eyes were treated using a Q-switched 532nm frequency-doubled Nd:YAG laser (Ellex SoloTM). An ophthalmogical examination was recorded including gonioscopy, a standardized automated perimetry (SAP), central corneal thickness measurement (CCT) and evaluation of biomechanical corneal properties using the Ocular Response Analyser (ORA, Reichert, Inc.), generating corneal hysteresis (CH), corneal compensated IOP (IOPcc) and corneal resistance factor (CRF). Treatment success was defined as 20% IOP reduction from baseline and IOP values below 21 mmHg six and twelve months after SLT treatment. Spearman's rank correlation and linear regression models were calculated. A p-value below 0.05 was considered to be significant.
Results: :
The distribution of glaucoma diagnosis was as follows: primary open angle glaucoma (POAG) n=105, normal tension glaucoma (NTG) n=7, pigment dispersion glaucoma (PDG) n=11, pseudoexfoliative glaucoma (PEX) n=23 and secondary glaucoma (SG) n=8. Six months after SLT overall IOP reduction was 2.9±6.2mmHg (12.0%, from baseline 18.1±5.2mmHg). For the subgroups, IOP reduction was 3.5±4.6mmHg (16.8%, from baseline 17.8±4.6mmHg), 1.0±4.0mmHg (3.2%, from baseline 11.8±2.3mmHg), -0.1±5.0 mmHg (-7.1%, from baseline 17.4±4.2mmHg), 3.1±5.8mmHg (13.7%, from baseline 20.0±5.1mmHg), -0.7±19.8mmHg (-30.5%, from baseline 21.9±8.7mmHg) in the groups POAG, NTG, PDG, PEX and SG, respectively. After twelve months the pressure lowering effect was stable in each group. In correlation analysis, the preoperative IOP correlated significantly with relative and absolute IOP reduction after six and twelve months (range of Spearman`s correlation coefficient from r=0.465 to r=0.725, p<0.001). There was no correlation between IOP reduction and any of the other clinical parameters. However, in linear regression models, the corneal biomechanical properties and CCT were significant predictors of the IOP lowering effect of SLT in addition to the baseline IOP (R²= 0.429 and R²=0.479 for success at six and twelve months, respectively).
Conclusions: :
Baseline IOP is the only clinical parameter that correlates with the IOP lowering effect of SLT. In regression analysis, the corneal biomechanical properties corneal hysteresis and corneal resistance factor as well as central corneal thickness predict the outcome of SLT for uncontrolled glaucoma after 12 months.
Clinical Trial: :
Institutional Review Board, MUC-SLT-2010
Keywords: laser • clinical (human) or epidemiologic studies: outcomes/complications