Transscleral cyclophotocoagulation using a contact laser probe: A histologic and clinical study in rabbits

Fasanella

Journal of Ophthalmology

et al. 2017

The ciliary body ablation is still considered as a last resort treatment to reduce the intraocular pressure (IOP) in uncontrolled glaucoma. Several ablation techniques have been proposed over the years, all presenting a high rate of complications, nonselectivity for the target organ, and unpredictable dose-effect relationship. These drawbacks limited the application of cyclodestructive procedures almost exclusively to refractory glaucoma. High-intensity focused ultrasound (HIFU), proposed in the early 1980s and later abandoned because of the complexity and side effects of the procedure, was recently reconsidered in a new approach to destroy the ciliary body. Ultrasound circular cyclocoagulation (UC3), by using miniaturized transducers embedded in a dedicated circular-shaped device, permits to selectively treat the ciliary body in a one-step, computer-assisted, and non-operator-dependent procedure. UC3 shows a high level of safety along with a predictable and sustained IOP reduction in patients with refractory glaucoma. Because of this, the indication of UC3 was recently extended also to naïve-to-surgery patients, thus reconsidering the role and timing of ciliary body ablation in the surgical management of glaucoma. This article provides a review of the most used cycloablative techniques with particular attention to UC3, summarizing the current knowledge about this procedure and future possible developments.

Section: Cyclodestructive Techniquesmentioning

confidence: 99%

Section: Miniaturized High-intensity Focused Ultrasounds For Cyclomentioning

confidence: 99%

High-Intensity Focused Ultrasound Circular Cyclocoagulation in Glaucoma: A Step Forward for Cyclodestruction?

Fasanella

Journal of Ophthalmology

et al. 2017

“…28 Most clinical studies 15,19 have considered 4-6 weeks as the time frame for the response of DLCP, after which the eyes are re-treated. We waited for 6 weeks before re-treating our patients.…”

Section: Transcleral Diode Laser Cyclophotocoagulation S Kaushik Et Almentioning

confidence: 99%

Lower energy levels adequate for effective transcleral diode laser cyclophotocoagulation in Asian eyes with refractory glaucoma

Kaushik

Pandav

Jain

et al. 2006

Eye

Purpose To study the treatment parameters for diode laser cyclophotocoagulation (DLCP) in Asian Indian eyes using laser energy titrated to clinical response. Methods This prospective interventional longitudinal study included 66 eyes of 66 patients with varied aetiology refractory glaucoma, no previous cycloablation, and minimum 1 year follow-up. DLCP was performed using the Oculight s Diode laser system (IRIS & Medical Instruments Inc., CA, USA). Power used per spot was titrated according to the audible 'pops' indicating tissue microexplosion. The mean laser energy delivered, post-laser intraocular pressure (IOP) reduction, complications, and requirement of re-treatment in various subgroups were analyzed. Differences in energy delivered in each subgroup were assessed by analysis of variance with post hoc Bonferroni corrections. Linear regression analysis was used to identify possible predictive factors for failure of cyclodiode therapy. Results The mean total energy delivered per eye was 87.80731.8 J (range 105.4736.8 J in neovascular glaucoma (NVG) to 61.578.8 J in uveitic glaucoma (P ¼ 0.134)). Mean pre treatment IOP was 36.4710.7 mmHg, which reduced to 19.479.8 mmHg (Po0.001) at 1 week, and 15.676.6 mmHg at 1 year. At 1 year, 58 of 66 patients had IOPo22.0 mmHg (response rate 87.8%), and six patients had hypotony (success rate 78.8%). The uveitic glaucoma group had 100% success rate. NVG group required maximum re-treatments. Conclusions DLCP with a titrated energy protocol needs resulted in lower energy in Asian Indian eyes compared to that reported in literature, and different energy levels are needed for different diseases. 'Standard treatment parameters' for DLCP may be inappropriate for all diseases and all races.

“…Our results show that the light of Nd: YAG lasers (1,064 nm) and of diode lasers (804 nm) is well transmitted through the sclera and hardly absorbed in scleral tissue. This corresponds to the observation made in various histological studies that after Nd:YAG and diode laser cyclocoagulation at moderate energy levels, the tissue effects are confined to the ciliary body [2,8,10,12,[17][18][19]41,42]. Only at high-energy levels (5 J in a rabbit eye) far above the coagulation threshold and at long exposure times (300 ms to 2 s), was scleral damage found, obviously having been caused by heat conduction from the ciliary body into the sclera [8,411. Comparison of the laser effects in pigmented rabbits and albino rabbits has shown that cyclocoagulation relies on the light absorption in the ciliary pigment epithelium [1,43,441.…”

Section: Clinical Consequencesmentioning

confidence: 99%

Optical properties of human sclera, and their consequences for transscleral laser applications

Vogel¹,

Dlugos²,

Nuffer³

et al. 1991

Lasers Surg Med

155

The spectral dependence of the optical properties of human sclera adjacent to the limbus was investigated and related to the potentials of transscleral photocoagulation. The total transmission, absorption, and reflection, as well as the angular distribution of the transmitted and reflected light were measured at five laser wavelengths (442 nm, 514 nm, 633 nm, 804 nm, and 1,064 nm), both for noncontact and contact applications. Absorption and scattering coefficients were determined using the Kubelka-Munk model for light propagation through a scattering tissue. The scleral transmission is only 6% at 442 nm but increases to 35% at 804 nm and to 53% at 1,064 nm. The absorption is high at short wavelengths with 40% at 442 nm but it is only 6% at 804 nm and 1,064 nm. The reflection is generally higher than 40% and shows little wavelength dependence. The transmitted light is scattered diffusely at short wavelengths, but at 804 nm and 1,064 nm it exhibits a fairly narrow angular distribution in forward direction. Fiber contact leads to an increase of transmission, with a factor of 3.5 at 442 nm, of 2.0 at 804 nm, and 1.5 at 1,064 nm. Our results indicate that the diode laser (804 nm) and the Nd:YAG laser (1,064 nm) with contact delivery are best suited for transscleral photocoagulation.