April 2014
Volume 55, Issue 13
Free
ARVO Annual Meeting Abstract  |   April 2014
Mechanism of Action of Selective Laser Trabeculoplasty
Author Affiliations & Notes
  • Vikas Gulati
    Ophthalmology & Visual Sciences, University of Nebraska Medical Center, Omaha, NE
  • Shan Fan
    Ophthalmology & Visual Sciences, University of Nebraska Medical Center, Omaha, NE
  • Donna G Neely
    Ophthalmology & Visual Sciences, University of Nebraska Medical Center, Omaha, NE
  • Bret J Gardner
    Ophthalmology & Visual Sciences, University of Nebraska Medical Center, Omaha, NE
  • Marie T Schaaf
    Ophthalmology & Visual Sciences, University of Nebraska Medical Center, Omaha, NE
  • Shane Havens
    Ophthalmology & Visual Sciences, University of Nebraska Medical Center, Omaha, NE
  • Carol B Toris
    Ophthalmology & Visual Sciences, University of Nebraska Medical Center, Omaha, NE
  • Footnotes
    Commercial Relationships Vikas Gulati, None; Shan Fan, None; Donna Neely, None; Bret Gardner, None; Marie Schaaf, None; Shane Havens, None; Carol Toris, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science April 2014, Vol.55, 820. doi:
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    • Get Citation

      Vikas Gulati, Shan Fan, Donna G Neely, Bret J Gardner, Marie T Schaaf, Shane Havens, Carol B Toris; Mechanism of Action of Selective Laser Trabeculoplasty. Invest. Ophthalmol. Vis. Sci. 2014;55(13):820.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: To determine the mechanism by which intraocular pressure(IOP) decreases following selective laser trabeculoplasty(SLT) in patients with ocular hypertension(OH) and primary open angle glaucoma(POAG).

Methods: Thirty one subjects with OH or POAG undergoing SLT as primary IOP lowering therapy were enrolled in this prospective study. All subjects underwent a baseline assessment of aqueous humor dynamics(AHD) in both eyes. The primary outcomes assessed were IOPs at 9AM and 12 noon (pneumatonometry), daytime(9AM-noon) aqueous flow (fluorophotometry), episcleral venous pressure (venomanometry), outflow facility (pneumatonography and fluorophotometry after oral acetazolamide) and uveoscleral outflow (Goldmann equation). All subjects underwent 360 degrees SLT (80 spots) within a week after baseline measurements. Subjects underwent a repeat assessment of AHD in both eyes at 3 months following SLT. Subjects were not on any IOP lowering medications at the time of either assessment.

Results: In the 29 subjects that completed all study visits the IOPs at 3 months after SLT were significantly lower at 9AM(19.5±3.1mmHg vs. 22.9±5.0mmHg at baseline; p=0.001) and 12 noon (19.9±3.4mmHg vs. 23.4±4.5mmHg at baseline; p<0.001). Outflow facility by fluorophotometry was significantly increased from 0.17±0.11 µl/min/mmHg at baseline to 0.24±0.14 µl/min/mmHg at 3 months(p=0.012). The changes in outflow facility by tonography (baseline:0.17±0.09 µl/min/mmHg vs. 3-months:0.21±0.12 µl/min/mmHg; p=0.14) did not reach statistical significance. There was no change in aqueous flow, episcleral venous pressure or uveoscleral outflow at 3 months after SLT. There were no changes in IOP or AHD in the untreated eye. A comparison of AHD was made between 16 subjects with >10% IOP reduction after SLT treatment (responders), and those without an IOP change (non-responders). Responders had a significant increase in fluorophotometric outflow facility from 0.16±0.13 µl/min/mmHg at baseline to 0.28±0.14 µl/min/mmHg at 3 months after SLT(p<0.001). Non responders did not have any change in outflow facility (baseline:0.19±0.09 µl/min/mmHg; 3 months:0.19±0.12 µl/min/mmHg, p=0.84). The only predictor of response was higher baseline IOP in the responder group (25.3±5.5mmHg vs. 20.3±2.8mmHg, p=0.004).

Conclusions: The IOP lowering effect of SLT appears to be mediated through an increase in trabecular outflow facility. Higher baseline IOP is associated with a better response to SLT laser.

Keywords: 633 outflow: trabecular meshwork • 568 intraocular pressure • 427 aqueous  
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