Effects of Selective Laser Trabeculoplasty on Aqueous Humor Dynamics

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. Identifier: NCT01342406
Recruitment Status : Completed
First Posted : April 27, 2011
Last Update Posted : February 19, 2014
Information provided by (Responsible Party):
Vikas Gulati, MD, University of Nebraska

Brief Summary:
This study will compare aqueous humor dynamics in adults with primary open angle glaucoma that receive Selective Laser Trabeculoplasty (SLT).

Condition or disease
Open Angle Glaucoma

Detailed Description:

Describe the background of the study. Include a critical evaluation of existing knowledge, and specifically identify the information gaps that the project is intended to fill.

Laser trabeculoplasty is currently a well established treatment option for lowering the intraocular pressure in the management of open angle glaucoma1,2. The procedure involves placement of laser spots over the trabecular meshwork, possibly through a variety of laser types. ALT has been the most widely utilized option for laser trabeculoplasty over the past few decades. Since its availability approximately a decade ago, SLT is currently an additional option for doing laser trabeculoplasty. 3,4. Current evidence suggests that SLT achieves its IOP lowering effect without thermal damage to the trabecular meshwork5. The IOP lowering effect of SLT has been shown to be comparable to ALT over the long term6.

In physiological terms, ALT has been shown to lower the IOP primarily by increasing the conventional outflow facility7. There are two putative mechanisms by which this may be facilitated8. Thermal coagulation and shrinkage by ALT may mechanically open up the adjacent trabecular meshwork and Schlemm's canal. Alternatively the delivery of laser energy may trigger biological processes and activation of matrix metalloproteinases in the microenvironment of trabecular meshwork that lead to a remodeling of tissues resulting in improved outflow facility. ALT uses argon or another thermal laser to photocoagulate tissues around the trabecular meshwork. The settings vary depending on the tissue response and pigmentation. Most clinicians use 600-1500mW, 50-100 spots, 50 micron spot size and 0.1 sec duration.

Also, there is limited data on fluorophotometric and tonographic studies on ALT and none on SLT to the best of our knowledge. All available reference known to the investigators have been included in the list of references.

The effect of SLT on the aqueous humor dynamics is currently unknown. Given the lack of demonstrable thermal damage on histopathologic examination5, it is unlikely that the effects of SLT could be mechanically mediated. There has been some suggestion of a potential interaction of IOP lowering effect when prostaglandins and SLT are used together9,10. This suggests that there could be a possible sharing of mechanisms between SLT and prostaglandins. The IOP lowering effect of SLT may be mediated in part by effects on uveoscleral pathways in addition to the trabecular outflow pathway. This study will determine the changes in aqueous humor dynamics produced by SLT that lead to its IOP lowering effect. SLT is a Q switched frequency doubled Nd:YAG laser. The duration is 3 nanoseconds and spot size 500 microns. Power varies from 0.5-1.5 mJ and total number of spots can be between 50-over 100. The mechanism of action may be disruption of melanosomes, but this has not been unequivocally proven yet.

Study Type : Observational
Actual Enrollment : 31 participants
Time Perspective: Prospective
Official Title: Effects of Selective Laser Trabeculoplasty on Aqueous Humor Dynamics
Study Start Date : September 2010
Actual Primary Completion Date : November 2013
Actual Study Completion Date : November 2013

Resource links provided by the National Library of Medicine

MedlinePlus related topics: Glaucoma
U.S. FDA Resources

Primary Outcome Measures :
  1. Changes in IOP after SLT and changes in outflow facility [ Time Frame: 3 years ]

Information from the National Library of Medicine

Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the contacts provided below. For general information, Learn About Clinical Studies.

Ages Eligible for Study:   40 Years and older   (Adult, Senior)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No
Sampling Method:   Non-Probability Sample
Study Population
Subjects with open angle glaucoma

Inclusion Criteria:

  • 40 years of age and older
  • Eye consideration for SLT (intraocular pressure above target with current medications, intolerance/allergy to topical medications, patient preference as primary treatment)
  • Open angles on gonioscopy

Exclusion Criteria:

  • Any previous surgical or laser procedures
  • Secondary glaucoma including pigmentary, exfoliative, uveitic, and traumatic glaucomas
  • Corneal opacities interfering with adequate fluorophotometry
  • Any active ocular infection within the past 2 months
  • Any corneal pathology increasing the likelihood of corneal abrasions
  • Inability to safely washout medications prior to laser treatment
  • Allergies to fluorescein, timolol, dorzolamide, or sulfa
  • Excessive (3+) trabecular meshwork pigmentation

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT01342406

United States, Nebraska
University of Nebraska Medical Center, Department of Ophthalmology
Omaha, Nebraska, United States, 68198-5540
University of Nebraska Medical Center, Department of Ophthalmology
Omaha, Nebraska, United States, 68198
Sponsors and Collaborators
University of Nebraska
Principal Investigator: Vikas Gulati, MD UNMC Department of Ophthalmology and Visual Sciences

Responsible Party: Vikas Gulati, MD, Principal Investigator, University of Nebraska Identifier: NCT01342406     History of Changes
Other Study ID Numbers: 191-10
First Posted: April 27, 2011    Key Record Dates
Last Update Posted: February 19, 2014
Last Verified: February 2014

Additional relevant MeSH terms:
Glaucoma, Open-Angle
Ocular Hypertension
Eye Diseases