August 2019

GLAUCOMA

Research Highlight
Micropulse cyclophotocoagulation effective in keratoplasty eyes


by Rich Daly EyeWorld Contributing Writer


Micropulse transscleral treatment in advanced glaucoma patient performed in OR with a block
Source: Robert Noecker, MD

 

“This study demonstrated that micropulse can lower IOP significantly in a manner that is less traumatic and inflammatory than other modalities such as traditional transscleral
cyclophotocoagulation.”
—Robert Noecker, MD

Surgeons may consider a new treatment for a challenging group of glaucoma patients: pulsed transscleral cyclophotocoagulation (TSCPC).
Pulsed TSCPC breaks a continuous wave laser into a series of repetitive pulses separated by pauses that prevent thermal buildup in the tissue. The noninvasive procedure uses a probe placed directly on the sclera.
The mechanism of action in the treatment of glaucoma is not completely understood; some effect on the ciliary body epithelium has been demonstrated as well as some improvement with uveoscleral outflow, but no gross destruction to the ciliary body has been detected with ultrasonic biomicroscopy.
A retrospective review in Cornea evaluated TSCPC treatments of 61 eyes in 57 post-keratoplasty patients who received one (31 patients), two (21 patients), three (8 patients), or four treatments (1 patient).1 The study used the Cyclo G6 MicroPulse P3 (IRIDEX).
Pre-treatment, the mean IOP was 28±11 mm Hg. At 1 month post-treatment the mean IOP was 17±7 mm Hg, at 3 months it was 17±8 mm Hg, at 6 months it was 18±9 mm Hg, and at 12 months it was 15±5 mm Hg.
The proportions of eyes during the four post-treatment periods with IOP ≤15 mm Hg were 40%, 51%, 48%, and 55%, respectively. The proportions with IOP ≤12 mm Hg were 21%, 29%, 20%, and 29%, respectively.
Six eyes (10%) received subsequent glaucoma filtration surgery.
The mean number of anti-glaucoma medications used before the initial treatment was 2.7 (range, 0–4) versus 2.2 (range, 0–4) at the last follow-up.
Many eyes in the study had already undergone glaucoma filtration surgery, which is a major risk factor for graft failure. At baseline, seven grafts were decompensated and five of 54 clear grafts (9%) had endothelial cell density <700 cells/mm. Graft survival was 94% at 1 year and 81% at 2 years after the initial laser treatment.
“This study found that pulsed TSCPC was generally an effective noninvasive alternative to glaucoma filtration surgery in keratoplasty eyes; it reduced IOP by a mean of 35% at 12 months and was well-tolerated by most treated subjects,” the authors wrote.
Management of post-keratoplasty glaucoma is crucial because high IOP is detrimental to both optic nerve fibers and endothelial cells of the corneal graft. IOP control is often more complicated in post-keratoplasty eyes because the long-term use of topical corticosteroids to prevent transplant rejection causes IOP elevation, noted the authors.

Surgeon’s view

Robert Noecker, MD, said this study addressed an important niche for use of micropulse and that it was a good study with a good number of patients treated. 
“This is a very difficult population of patients to treat and the alternatives are not good,” Dr. Noecker said.
Dr. Noecker noted that tubes can achieve similar IOP lowering but are also associated with high rates of corneal failure. 
“The IOP lowering that was achieved with micropulse was similar to that in other populations such as primary open angle patients,” Dr. Noecker said. “This study demonstrated that micropulse can lower IOP significantly in a manner that is less traumatic and inflammatory than other modalities such as traditional transscleral cyclophotocoagulation.”
Other milder technologies such as MIGS are not indicated or will not deliver the desired efficacy, Dr. Noecker said.

Questions remain

Pulsed TSCPC can be titrated to minimize the occurrence of hypotony. However, it is not known how often the treatment can be repeated if the IOP is not sufficiently reduced, the study authors noted.
To varying degrees, the laser is applied blindly to the internal structures of the eye and may be treating either the ciliary body or the trabecular meshwork, and where the treatment is actually applied could influence the effect of subsequent treatments.
The authors said further research is needed to determine whether breakdown of the blood-aqueous barrier is less intense with TSCPC than it is with a trabeculectomy or aqueous shunts and to further assess graft survival and endothelial cell loss in eyes that are not as severely compromised as many of the eyes were in this study.
“Interestingly, the TSCPC treatment reduced IOP in our eyes with total angle closure, indicating that either the iris tissue covering the trabecular meshwork becomes more porous to fluid transfer across it or production of aqueous fluid by the ciliary body decreased,” the authors wrote.

About the doctor

Robert Noecker, MD
Ophthalmic Consultants of Connecticut
Clinical assistant professor of ophthalmology
Yale University
New Haven, Connecticut

Contact information

Noecker
: noeckerrj@gmail.com

Financial interests

Noecker: None

Reference

1. Subramaniam K, et al. Micropulse transscleral cyclophotocoagulation in keratoplasty eyes. Cornea. 2019;38:542–545.

Micropulse cyclophotocoagulation effective in keratoplasty eyes Micropulse cyclophotocoagulation effective in keratoplasty eyes
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