Cyclodiode useful treatment in refractory pediatric glaucomas

Although response may be temporary, cyclodiode may be safer than surgical modalities in high-risk patients.

LONDON – With repeated treatment, cyclodiode can provide control of IOP in refractory pediatric glaucoma. The surgery has a role as a temporizing measure, as an adjunct to surgery or in managing selected patients in whom surgery is undesirable because of a high risk of surgical complications, study authors said.

Peng T. Khaw, FRCOphth, PhD, and colleagues at Moorfields Eye Hospital and Institute of Ophthalmology reported the efficacy and complications of diode laser cyclophotocoagulation (cyclodiode) in the management of refractory pediatric glaucomas in a noncomparative interventional case series.

In the series, they studied pediatric patients with uncontrolled glaucoma. Seventy-seven eyes of 61 patients underwent cyclodiode. The mean age was 7.4 years (0.4 to 17 years). They measured for IOP, visual acuity and complications.

Background

Pediatric glaucomas, particularly secondary glaucomas, are notoriously difficult to manage. Drainage surgery may be complicated by hypotony because of large eyes with thin sclera and by failure to control IOP caused by an aggressive healing response. Patients whose glaucoma cannot be controlled by drainage procedures pose challenging management problems.

The authors used cyclodiode as a method of ciliary body ablation to lower IOP. Previously, cyclocryotherapy has been the most commonly used method of cyclodestruction.

Consecutive case records of patients aged less than 18 years undergoing cyclodiode between January 1994 and April 1998 were examined. Patients were excluded if less than 12 months follow-up was available. Records of 77 eyes of 61 patients were available for this study.

A total of 177 cyclodiode procedures were performed, with a mean of 2.3 sessions per eye. The median follow-up duration was 21 months (range 13 to 56 months). During the study period, cyclodiode was performed once on 33 of 77 eyes, twice on 20 eyes, three times on 12 eyes and four or more times on 12 eyes.

Primary cyclodiode treatment was not generally performed in phakic eyes; 23 of 28 eyes undergoing primary cyclodiode were aphakic. The use of primary cyclodiode in phakic eyes was restricted to eyes with an abnormal anterior segment (such as severe microphthalmia, secondary angle closure caused by Coats’ disease), where conventional surgery was inappropriate or for pain relief in a blind eye. A total of 46 of 77 eyes were aphakic.

Cyclodiode was performed in cases of advanced glaucoma with previous failed surgical procedures. In the study, other reasons for surgery included:

• markedly elevated IOP on acute presentation;
• where an at-least temporary IOP control was required before undertaking more definitive surgery;
• treatment of a blind painful eye with an elevated IOP;
• markedly elevated IOP;
• where the fellow eye was undergoing or had recently undergone surgery and the investigators wished to defer surgery until the fellow eye had stabilized;
• moderately elevated IOP with maximum medical therapy;
• where the risks of drainage surgery were considered high (such as where there had been severe complications in the fellow eye);
• or where surgery was declined by the patient or parents.

The surgery

All cyclodiode procedures were performed with the patient under general anesthesia. A lid speculum was used to permit adequate access to the treated eye. Transillumination of the ciliary body was used in all cases to demonstrate the position of the ciliary body, because its location varies considerably in these enlarged and abnormal eyes.

The cyclodiode treatment called for 40 applications at 1500 mW for 1500 ms, based on previous histological studies in the authors’ laboratory. All treatments were performed using the contact G-probe for transscleral cyclophotocoagulation with the Iris Medical OcuLight 810-nm laser system from Iridex.

The 3- and 9-o’clock and positions were spared for 60° to avoid the long ciliary nerves and to potentially reduce pain. A total of 300° was treated. Power was reduced if “pops” were heard during treatment, as these suggested rapid gaseous expansion. Subconjunctival dexamethasone was administered. Topical corticosteroids, to be used four to eight times daily, were then prescribed for 6 weeks after treatment.

“After treatment, if a satisfactory IOP response had been obtained, reduction of antiglaucoma medications was attempted. If an adequate IOP response was not obtained or the initial IOP effect was lost, then repeat treatment was considered, depending on the clinical circumstances, up to a maximum of eight sessions,” the authors reported.

Mean pretreatment IOP in this study was 32 mm Hg. Within the first 3 months after one session of treatment, the mean IOP was 20.2 mm Hg. The mean time from first treatment to final IOP recording was 9.9 months for each individual procedure. Many of these eyes subsequently underwent further cyclodiode treatment or drainage procedures.

Of the cases treated, 38 of 61 had an initial reduction of IOP by 30% or to less than 21 mm Hg. A further 10 treatments led to a partial response, IOP reduction by more than 20%. At 1 year, only 37% had IOP controlled to 21 mm Hg or less with one procedure in the treated eye. If success was defined as an IOP less than 17 mm Hg, then 21 of 61 had an initial response, and 10 of 61 had IOP control at 1 year.

With repeat treatment, the authors found that sustained control of IOP to the 21-mm-Hg level could be achieved in 72% of eyes at 1 year and 51% at 2 years. In these eyes the mean duration between treatment sessions was 8.4 months.

Patients with a profound early lowering of IOP within the first month to 15 mm Hg or less had more sustained IOP control. The median duration of effect was 9 months if the early post-treatment IOP was 16 to 21 mm Hg and 15 months if 15 mm Hg or less.

Antiglaucoma medications

The mean number of antiglaucoma medications was 1.97 before cyclodiode therapy and 2.28 at last follow-up. In some patients cyclodiode enabled discontinuation of systemic acetazolamide. However, a number of patients were treated with an increased number of medications as new drugs became available for clinical use during the study period.

The effect of cyclodiode in younger patients (age less than 5 years) showed a trend toward a shorter duration of effect; 43% of older subjects had IOP control at 1 year vs. 21% of younger subjects.

Aphakic patients had a more sustained IOP-lowering response to cyclodiode after their first treatment session. The mean early IOP was 19.3 mm Hg for aphakic patients and 21.4 mm Hg for phakic patients. Pretreatment IOP levels were similar for both groups (32.8 mm Hg and 31 mm Hg, respectively). Aphakic patients had a 42% chance of still having IOP control at 1 year compared with a 14% chance with phakic eyes. Aphakic patients were slightly, but not significantly, younger than phakic patients (mean ages 6.9 and 8.3 years).

Subsequent glaucoma drainage surgery was performed in 17 of 77 eyes (eight drainage tubes, 10 trabeculectomies). Two of these eyes that had multiple cyclodiode treatments (five and four treatments) subsequently underwent drainage tube surgery and developed hypotony-associated complications. Both of these eyes had advanced glaucoma at presentation.

Long-term possibilities

“To our knowledge, this is the largest series of pediatric glaucoma cases managed with cyclodiode,” Dr. Khaw said. “Our results for one treatment session are similar to another series in pediatric patients reported by Bock et al. Compared with adults treated with the same protocol, the degree of lowering of IOP was similar but for a shorter duration.”

The study found that a single diode laser cycloablation session reduces IOP at least temporarily in 60% of patients, but treatment effect may wear off rapidly, particularly in phakic, very young patients.

“Re-treatment frequently results in a more sustained IOP control. Cyclodiode treatment may be helpful when an IOP in the high teens-to-low 20s is considered acceptable, but if the target is an IOP less than 17 mm Hg off medication, cyclodiode has a very poor chance of success,” Dr. Khaw said.

He believes diode laser cycloablation will not replace drainage procedures in the management of complex secondary pediatric glaucomas.

“However, a significant number of patients in this study were poor candidates for drainage procedures,” he said. “Many had very poor or no vision in the fellow eye and often vision had been lost in one eye because of previous drainage surgery. If these patients were seen for the first time, the temporizing effect of cyclodiode allowed a relationship to be built with the patients and parents before surgery in the remaining eye was carried out. Many eyes had extremely large corneal diameters and axial lengths with thin sclera. Aphakic eyes may be particularly predisposed to severe posterior segment complications after drainage procedures.

“Our study is open to recall bias, as for any retrospective study. In addition, we have a particularly severe case mix, because many patients are referred when they have had unsuccessful or complicated previous surgery. The pediatric glaucoma service at Moorfields Eye Hospital receives referrals from across the United Kingdom, Europe and the Middle East. Many of these patients have had previous surgery fail or postoperative complications develop.

Dr. Khaw surmised that cyclodiode treatment has a reasonable success rate in this group of patients and has a lower rate of severe adverse effects than surgical modalities in very high-risk patients.

“In addition to temporizing, cyclodiode may act as an adjunct to surgery or in managing selected patients in whom surgery is undesirable because of a high risk of surgical complications. Diode laser cyclophotocoagulation is a useful addition to the armamentarium of the ophthalmologist managing pediatric glaucomas,” he said.

For Your Information:

• Peng T. Khaw, FRCOphth, PhD, can be reached at Moorfields Eye Hospital and the Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK; +(44) 20-7566-2989; fax: +(44) 20-7566-2972; e-mail: p.khaw@ucl.ac.uk. Dr. Khaw has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.

Reference:

• Kirwan JF, Shah P, Khaw PT. Diode laser cyclophotocoagulation in the management of refractory pediatric glaucoma. Ophthalmology. 2002;109:316-323.