The effect of transscleral laser cyclophotocoagulation on rabbit ciliary body vascularization

[Morphological evaluation of the results of laser activation of scleral hydropermeability in the treatment of glaucoma]

PURPOSE

The study attempted to experimentally substantiate the possibility of using the laser activation of scleral hydropermeability (LASH) technique in glaucoma treatment by morphological evaluation of treatment outcomes.

MATERIAL AND METHODS

The pulsed-periodic radiation from an Er-glass fiber laser (λ=1.56 μm) was used. The model experiment consisted of evaluating ultrafiltration of fluid through the tissues of human sclera autopsy specimen according to the original technique using neodymium chloride-based labeling agent and scanning electron microscopy. The clinical part of the study consisted of optical coherence tomography (OCT) and laser confocal microscopy of the sclera and conjunctiva (CMSC) performed in vivo immediately after laser treatment in the laser application sites in 5 patients (5 eyes) aged 57 to 68 years with uncompensated advanced (IIIb-c) stage of glaucoma who had previously underwent LASH surgery.

RESULTS

Results of morphological evaluation after LASH revealed structural changes indicating increased transscleral ultrafiltration: increased intrastromal hyporeflective areas in the sclera, thinning of collagen fibers, formation of porous structures. Using an original technique involving neodymium chloride-based labeling agent and scanning electron microscopy, we were able to prove the enhancement of transscleral ultrafiltration. The results of the experiment were confirmed by in vivo OCT images of the sclera and CMSC performed in 5 patients with advanced glaucoma after LASH surgery, in which tissue decompaction in the laser-exposed areas was clearly visualized.

CONCLUSION

The revealed structural changes indicate the possibility of reducing intraocular pressure after LASH by the means of forming scleral porous structures and increasing transscleral ultrafiltration. Experimentally selected optimal mode of laser exposure (0.66 W with total exposure time of 6 seconds) during LASH helps avoid gross destructive changes in the eye tissues, making the proposed intervention a sparing approach to the treatment of glaucoma.

[Transscleral laser therapy in the treatment of glaucoma]

Nowadays glaucoma is one of the leading causes of irreversible blindness worldwide. The main goal in preservation of vision in glaucoma patients is reducing intraocular pressure (IOP), which is considered the main controlled risk factor for progression of glaucomatous optic neuropathy. The article discusses the effectiveness and safety of various transscleral laser technologies in the treatment of glaucoma. Modern transscleral laser technologies that affect the uveoscleral drainage and scleral hydro-permeability are less traumatic and more gentle making them promising in the treatment of patients with early stages of glaucoma, and not only in terminal glaucoma with pain syndrome resistant to conventional treatment ("last resort surgery").

Lasers in glaucoma

While lasers have been used for many years for the treatment of glaucoma, proper indications and use of the procedures need to be considered before their application. This review summarizes the important laser procedures in Glaucoma.

Short- and long-term effects on the ciliary body and the aqueous outflow pathways of high-intensity focused ultrasound cyclocoagulation

Several physical methods can be used to coagulate the ciliary body and decrease intra-ocular pressure in patients with glaucoma. The study described here investigated the short- and long-term effects of high-intensity focused ultrasound (HIFU) cyclocoagulation on the aqueous humor production structures and outflow pathways. Thirty-four rabbit eyes were sonicated with a ring-shaped probe containing six miniaturized HIFU transducers. Light, scanning electron and transmission electron microscopy and corrosion casts were performed. In the affected regions, the epithelium of the ciliary processes was degenerated or necrotic and sloughed off. Examinations performed several months afterward revealed involution of the ciliary processes. Vascular corrosion cast revealed focal interruption of the ciliary body microvasculature. In most animals, a sustained fluid space was seen between the sclera, the ciliary body and the choroid, likely indicating an increase in the aqueous outflow by the uveoscleral pathway. These results suggest that HIFU cyclocoagulation has a dual effect on aqueous humor dynamics.

Endoscopic ophthalmic surgery of the anterior segment

We summarize the uses of anterior segment endoscopic techniques and the basic science and technology of endoscopic cyclophotocoagulation (ECP) as compared with transscleral cyclophotocoagulation. This is followed by an analysis of patient selection for ECP, a description of surgical techniques, and clinical results. In addition, the ophthalmic endoscope has other uses in anterior segment surgeries. We discuss the techniques for these endoscope-assisted surgeries.

The effect of probe placement and type of viscoelastic material on endoscopic cyclophotocoagulation laser energy transmission

BACKGROUND AND OBJECTIVE

Endoscopic cyclophotocoagulation is a laser modality used to treat refractory glaucoma through the ablation of ciliary epithelium on the ciliary processes, which results in reduced aqueous production. The purpose of this study was to investigate the effect of various viscoelastics and optimal probe positioning on endoscopic cyclophotocoagulation treatment.

MATERIALS AND METHODS

Six different viscoelastic materials and a balanced salt solution, which was used as a control, were evaluated by placing 2 mL of each in a separate 2 mL glass tube. Laser power was measured at six distances to represent clinical placement of the laser probe in relation to the ciliary processes.

RESULTS

The amount of energy measured with the probe at the bottom of the tube and 1 and 2 mm away was not statistically significantly different among the viscoelastic materials or the balanced salt solution. There was a gradual decrease in transmission of laser energy in all viscoelastics as the laser probe was moved farther away.

CONCLUSION

To preserve the intended laser energy setting, the optimal distance between the treated tissue and the laser probe is 2 mm.

Glaucoma lasers: a review of the newer techniques

PURPOSE OF REVIEW

This paper serves to review the safety and efficacy of new laser techniques for the treatment of glaucoma with emphasis on those studies published within the past year.

RECENT FINDINGS

Recently published studies have reinforced the strong safety profile, and efficacy of selective laser trabeculoplasty (SLT). Endoscopic photocoagulation, while more technically challenging and more invasive, offers several advantages over transcleral cyclophotocoagulation including direct observation of treatment and therefore, fewer complications. Laser goniopuncture is a fledgling technology with, thus far, a good safety profile, and benefits that include conjunctival sparing and good treatment response. Many unanswered questions remain including long-term success rates and ideal treatment parameters.

SUMMARY

The benefits of laser in the treatment of glaucoma have been well established, and while some techniques will add to the ophthalmologists' armamentarium, others will fall into disuse as the efficacy and safety profiles of these procedures become recognized. Novel laser modalities, as well as the more traditional ones, require continued evaluation to further refine treatment parameters and to determine their long-term benefits.

Long-term results of noncontact neodymium:yttrium-aluminum-garnet cyclophotocoagulation in neovascular glaucoma

PURPOSE

To determine the long-term efficacy and safety of noncontact transscleral neodymium:yttrium-aluminum-garnet (Nd:YAG) cyclophotocoagulation (CP) for the treatment of neovascular glaucoma (NVG).

DESIGN

Retrospective, noncomparative, interventional case series.

PARTICIPANTS

One hundred fifteen eyes of 111 subjects treated from December 1987 to January 2001.

METHODS

Eyes with uncontrolled NVG underwent noncontact Nd:YAG CP. Treatment parameters and pretreatment and posttreatment intraocular pressures (IOP) were reviewed. Preoperative and postoperative IOP were compared using a paired Student's t test. Success was defined as an IOP </=22 mmHg, with or without medications, in the absence of phthisis bulbi, and without having undergone further surgical procedures. Results were subjected to a Kaplan-Meier life-table analysis.

RESULTS

Mean follow-up was 27.0 +/- 34.3 months (range, 1-148 months). Mean preoperative IOP was 47.4 +/- 11.1 mmHg (range, 26-70 mmHg). Mean postoperative IOP was 18.3 +/- 12.2 mmHg (range, 0-44 mmHg). The mean number of treatment sessions was 1.4 +/- 0.7 (range, 1-6), with 82 eyes (71.3%) having only one treatment. Kaplan-Meier survival analysis showed a probability of continued success at 1 year of 65.0%, at 3 years of 49.8%, and at 6 years of 34.8%. Phthisis developed in 8.6% of the eyes.

CONCLUSIONS

Noncontact Nd:YAG CP provides long-term IOP reduction in eyes with medically uncontrolled NVG. This can be associated with complications that include inflammation, visual loss, and hypotony. Repeat treatment may be necessary.

Pathology of cyclodiode laser: a series of nine enucleated eyes

AIM

To study the histological effects of cyclodiode laser treatment in humans, and to compare these findings with the clinical course, treatment response, complications, and indications for enucleation.

METHOD

Detailed histological examination of nine enucleation specimens was undertaken in conjunction with a retrospective review of patient case notes.

RESULTS

Retreatments had been undertaken in three cases. Although all globes showed damage to pars plicata, intact ciliary processes within the treatment zone were present in all cases. Pars plana injury was also noted in two thirds of cases. Inflammation was mild. Ciliary epithelial proliferation was seen in most cases with increasing time following treatment, in a disorganised pattern, without replication of the ciliary epithelial bilayer. No regeneration of the ciliary processes with fibrovascular cores was found. The three patients with good IOP control at enucleation had all had multiple diode treatments. Neither phthisis nor sympathetic ophthalmia was seen.

CONCLUSIONS

Diode laser cyclophotocoagulation produces very characteristic injury to pars plicata, which frequently extends into pars plana, but with only mild persisting inflammation. Ciliary processes are, however, frequently spared within the treatment zone and may account for early or late treatment failure.

Ciliary body ablation: where are we and how did we get here?

Management of intraocular pressure remains the cornerstone of glaucoma treatment. Related medical and surgical practices involve increasing aqueous outflow or decreasing aqueous production. Filtration procedures that increase aqueous outflow are the first-line surgical defense in glaucoma. However, some cases of glaucoma are resistant to such treatment. In these cases, ciliary body ablation by various methods has had substantial success. Surgical manipulation of aqueous production has been used in glaucoma management since the turn of the century. Techniques have progressed markedly as technology has produced more discrete therapies designed to decrease aqueous production by destroying ciliary body epithelium. Over the past 90 years success has been achieved with a wide range of techniques, from surgical disinsertion of the ciliary body to recent laser and ultrasound techniques. With the development of more precise contact lasers and endoscopic visualization, side effects have been reduced and clinical success rates increased.

Noncontact thermal mode Nd:YAG laser transscleral cyclocoagulation in the treatment of glaucoma. Intermediate follow-up

Noncontact transscleral Nd:YAG laser thermal mode cyclocoagulation is known to reduce intraocular pressure (IOP). Thirty-five eyes were treated at a mean of 2.5 Joules and followed for a mean of 28 months. The mean preoperative IOP of 39.8 mmHg (standard deviation, 11.7) was consistently decreased by 45% to 55% over the follow-up period (standard deviation, 19.9 to 30.8), along with a significant reduction of medical therapy. This effect is comparable with that obtained by investigators using much higher energy levels. Successful control was defined as IOP between 5 and 21 mmHg for eyes with visual acuity of counting fingers or better, between 5 and 25 mmHg for eyes with hand motions to light perception, and as control of ocular pain for eyes with no light perception; 71% to 75% of the eyes were successfully controlled for up to 3 years. The use of lower energy levels appears to be associated with a lower incidence of vision loss and, therefore, merits further controlled investigation.