Sequential Laser Iridotomy Using Argon and Q-Switched 532 nm Frequency Doubled Neodymium Yag Laser: A Pilot Study
Primary Purpose
Chronic Angle Closure Glaucoma, Primary Angle Closure, Primary Angle Closure Suspect
Status
Completed
Phase
Not Applicable
Locations
Singapore
Study Type
Interventional
Intervention
Q-switched fd Nd:yag in Laser Iridotomy
Sponsored by
About this trial
This is an interventional treatment trial for Chronic Angle Closure Glaucoma focused on measuring Sequential Laser Iridotomy, Q-Switched 532 nm Laser, Frequency Doubled Neodymium Yag Laser
Eligibility Criteria
Inclusion Criteria:
- More than 21 years old
- Able to give informed consent
- Diagnosis of either: chronic angle closure glaucoma (CACG), primary angle closure (PAC), primary angle closure suspect (PACS) or fellow eyes of acute angle closure glaucoma (AACG), and in need of a laser iridotomy
Exclusion Criteria:
- History of any prior laser treatment or intraocular surgery to the eye
- History of any corneal disease
- Any ocular infection/ inflammation within the last two months
- Inability to give informed consent
Sites / Locations
- National University Hospital
Outcomes
Primary Outcome Measures
Visual Acuity
Intraocular pressure
Total power delivered by each laser modality
Iridotomy patency and size
Pain rating during the procedure
Anterior segment inflammation
Endothelial cell count
Cataract progression
Rate of complications
Secondary Outcome Measures
Full Information
NCT ID
NCT00452998
First Posted
March 27, 2007
Last Updated
May 12, 2008
Sponsor
National University Hospital, Singapore
1. Study Identification
Unique Protocol Identification Number
NCT00452998
Brief Title
Sequential Laser Iridotomy Using Argon and Q-Switched 532 nm Frequency Doubled Neodymium Yag Laser: A Pilot Study
Official Title
Sequential Laser Iridotomy Using Argon and Q-Switched 532 nm Frequency Doubled Neodymium Yag Laser: A Pilot Study
Study Type
Interventional
2. Study Status
Record Verification Date
May 2008
Overall Recruitment Status
Completed
Study Start Date
November 2006 (undefined)
Primary Completion Date
December 2007 (Actual)
Study Completion Date
December 2007 (Actual)
3. Sponsor/Collaborators
Name of the Sponsor
National University Hospital, Singapore
4. Oversight
Data Monitoring Committee
Yes
5. Study Description
Brief Summary
Sequential Laser Iridotomy uses argon and Nd:yag laser in the first and second steps, respectively. Using q-switched 532 nm laser in the second step is hypothesized to be as good and effective as the conventional Nd:yag laser, because it selectively targets pigmented cells and delivers a short pulse duration of 3 nanoseconds, causing less thermal and collateral damage.
Detailed Description
Laser iridotomy is an established procedure in the management of angle closure glaucoma (ACG) and for prophylaxis in the fellow eyes.
Sequential argon-YAG (SAY) laser iridotomy is the serial use of argon and Nd:YAG laser at the same treatment session to create an iridotomy. Argon laser is initially used to make a bore of about 500 μm in diameter to an estimated two-thirds iris thickness in depth. The 1064 nm Q-switched neodymium YAG laser is next used to complete the perforation1. Others aim the argon laser at the iris surface to create a crater, and the next shots at the base of the crater until the iris is penetrated as evidenced by a pigment plume. The Nd:YAG laser then creates a photodisruptive explosion to enlarge the opening.
This procedure was first described by Zborwski-Gutman in 1988. Sixteen eyes were treated with two argon stretch burns and up to 35 penetrating burns that produced an iridotomy that was either imperforate or inadequate. Nd:YAG laser was used to complete the iridotomy. In all the eyes, the iridotomy was achieved in one session, and two eyes had a moderate increase in pressure that was easily controlled. The authors found that the total energy levels for each laser modality were significantly lower than those previously reported using either laser alone. The authors concluded that the sequential technique is safe and effective, and is recommended for iridotomy in difficult iris types.
Lim et al in 1996 did a prospective study that compared argon laser iridotomy and SAY in dark irides. Twenty-four eyes of 17 patients were involved; and 13 underwent argon laser iridotomies, and 11 underwent SAY. The argon laser settings were standardized at 1.2 W, 50 μm spot size and 0.1 second duration. The Nd: YAG laser was set at 2.5 mJ and single-pulse shots were used. All the iridotomies were completed in a single session. The mean total energy used for argon laser iridotomy was 8.28 J; while for SAY, 3.12 J was used for the argon laser stage and 7.5 mJ for the Nd:YAG stage. The authors concluded that the total argon laser energy used can be reduced by 2.65 times using the SAY technique.
The SAY technique is ideal in Asian eyes because it avoids the disadvantages of argon and Nd-YAG laser, when they are used as separate methods.
In SAY, bleeding is uncommon and microscopic, unlike in Nd:YAG iridotomy wherein it can be severe enough to cause the abortion of the procedure. Nd:YAG iridotomy is rarely associated with focal lens or retina damage; but argon laser can cause inadvertent focal lens damage.
By using ND:YAG laser as second stage laser, SAY iridotomy avoids the tedious and hazardous chipping enlargement phase of argon iridotomy that can contribute to retinal damage. Likewise, with the argon laser pre-treatment, excessive pigment and debris dispersion, iris splintering, and high energy levels needed for iris perforation from a Nd:YAG iridotomy in an Asian eye is avoided. In Ho's series of 20 patients who underwent SAY, only one eye had iridotomy closure during a mean follow-up period of 14 months.
Q-switched 532 nm frequency-doubled neodymium:yytrium-aluminum-garnet (fd-Nd:YAG) laser has been used in the recent years for selective laser trabeculoplasty (SLT). It was developed by Latina et.al. to selectively target pigmented trabecular meshwork (TM) cells without causing thermal or collateral damage to the nonpigmented cells or structures of the TM. This is so because it is able to deliver a short pulse duration of 3 nanoseconds while selectively lysing intracellular melanosomes, killing pigmented cells and leaving cellular membranes and neighboring nonpigmented cells intact. This technique delivers less than 1% of the energy of ALT, with shorter pulse durations and consequently higher power levels. Latina noted bubble formation at higher fluence, but this is not from boiling tissue, but are microcellular cavitation effects.
6. Conditions and Keywords
Primary Disease or Condition Being Studied in the Trial, or the Focus of the Study
Chronic Angle Closure Glaucoma, Primary Angle Closure, Primary Angle Closure Suspect, Fellow Eyes of Acute Angle Closure Glaucoma
Keywords
Sequential Laser Iridotomy, Q-Switched 532 nm Laser, Frequency Doubled Neodymium Yag Laser
7. Study Design
Primary Purpose
Treatment
Study Phase
Not Applicable
Interventional Study Model
Single Group Assignment
Masking
None (Open Label)
Allocation
Non-Randomized
Enrollment
10 (Anticipated)
8. Arms, Groups, and Interventions
Intervention Type
Procedure
Intervention Name(s)
Q-switched fd Nd:yag in Laser Iridotomy
Primary Outcome Measure Information:
Title
Visual Acuity
Title
Intraocular pressure
Title
Total power delivered by each laser modality
Title
Iridotomy patency and size
Title
Pain rating during the procedure
Title
Anterior segment inflammation
Title
Endothelial cell count
Title
Cataract progression
Title
Rate of complications
10. Eligibility
Sex
All
Minimum Age & Unit of Time
22 Years
Accepts Healthy Volunteers
Accepts Healthy Volunteers
Eligibility Criteria
Inclusion Criteria:
More than 21 years old
Able to give informed consent
Diagnosis of either: chronic angle closure glaucoma (CACG), primary angle closure (PAC), primary angle closure suspect (PACS) or fellow eyes of acute angle closure glaucoma (AACG), and in need of a laser iridotomy
Exclusion Criteria:
History of any prior laser treatment or intraocular surgery to the eye
History of any corneal disease
Any ocular infection/ inflammation within the last two months
Inability to give informed consent
Overall Study Officials:
First Name & Middle Initial & Last Name & Degree
Paul Chew, FRCSEd,MMed
Organizational Affiliation
National University Hospital, Singapore
Official's Role
Principal Investigator
Facility Information:
Facility Name
National University Hospital
City
Singapore
ZIP/Postal Code
119074
Country
Singapore
12. IPD Sharing Statement
Citations:
PubMed Identifier
7789416
Citation
Latina MA, Park C. Selective targeting of trabecular meshwork cells: in vitro studies of pulsed and CW laser interactions. Exp Eye Res. 1995 Apr;60(4):359-71. doi: 10.1016/s0014-4835(05)80093-4.
Results Reference
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Sequential Laser Iridotomy Using Argon and Q-Switched 532 nm Frequency Doubled Neodymium Yag Laser: A Pilot Study
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