Transscleral noncontact cyclophotocoagulation

Transscleral noncontact photocoagulation is done with an Nd:YAG laser and a slit-lamp; air serves as the energy transmission medium. The laser spot is positioned 1.0–1.5 mm posterior to the sclerocorneal limbus; the distance is calculated with a compass or by positioning the sight at the center of a luminous slit 3 mm in length. The laser can be used in the free-running mode with pulses of 4–8 J, 20-s duration, and the defocus set to 9. With these parameters, one can treat 3601 (total: 30–40 spots, 8–9 per quadrant); the 3 and 9 o’clock positions are excluded from treatment to avoid damage to the long posterior ciliary arteries. Treatment is facilitated by the use of the Shields transscleral lens, which improves focusing and facilitates the passage of the laser energy, thus reducing the risk of conjunctival burns.

Postoperative treatment is based on the administration of antibiotics and steroids for approximately 2 weeks; pressure-reducing therapy is continued (with possible withdrawal of miotics), and the patient is checked 1 h, 1 day, and 1 week after treatment.

Transscleral contact cyclophotocoagulation

Transscleral contact cyclophotocoagulation is the most widely used cyclophotocoagulation technique. Contact treatment offers the advantage of energy transmission through the conjunctiva and sclera by means of an optic fiber probe placed directly on the bulb. Compared with the noncontact approach, this technique uses less energy.

It can be carried out with a Nd:YAG laser (1064 nm) in the continuous-emission mode by means of an optical fiber or with a diode laser (810 nm). In the Nd:YAG procedure, the probe is positioned at a right angle to the conjunctiva, 0.5–1 mm behind the sclerocorneal junction; the full circumference (3601) is treated (total: 16–40 spots, 4–6 J) with the exception of the 3 and 9 o’clock positions. The exposure time is 0.5–0.7 s, and scleral indentation facilitates energy transmission. Better results are obtained with a relatively

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light initial treatment followed by one or more additional treatments as needed.

With diode systems, the energy is delivered by means of the G-probe, a bundle of optical fibers whose contour adapts to the curvature of the sclerocorneal junction. The application site is 0.5–2.0 mm behind the limbus; transillumination is used to visualize the ciliary processes; 8–15 spots (1500–2500 mW lasting 1–2 s) are made from 901 to 2701. The upper temporal zone is generally spared so that trabeculectomy or other surgical procedures can be performed if necessary. The diode laser (DLCP) is a semiconductor laser with a wavelength of 810 nm. Its advantages include good penetration and selective absorption by the pigmented tissue of the ciliary body; transscleral DLCP is thus a selective cycloablative technique that is more conservative than the others.

Complications

In all cases subjected to cyclophotocoagulation treatment, mild reactive iritis develops after treatment. Conjunctival edema and pain during the treatment are common, especially when contact application is used. The most severe complications are seen is eyes treated with noncontact methods, which use high-energy levels and are often associated with arbitrary focusing of the laser beam. In the literature, phthisis bulbi is reported in 10% of all cases, permanent hypotonus in 26%, and anterior-chamber hemorrhage in 10–30%; less frequent complications include detachment of the choroid, hemovitreous, and sympathetic ophthalmia.

Complications are rare in eyes treated with a diode laser:

phthisis bulbi 1.6% (Kramp et al., 2002) pain during treatment 25%

Pupil ovalization due to the use of high-energy lasers (2000 mW) (very rare) (Pucci and Tappainer, 2003).

Recent studies have assessed the efficacy and complication rates of diode laser treatment with spots of different energy levels in patients with refractory glaucoma: there were no significant differences in the reductions in IOP. However,

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high-energy spots were associated with a higher rate of postlaser complications (hypotonus, transient hyphema, and anterior-chamber exudates) (Murphy and Burnett, 2003; Chang et al., 2004).

Efficacy

The results of contact and noncontact YAG laser cyclophotocoagulation are similar. Pressure reductions (p24 mmHg) are observed in 45–80% of cases during the first year of follow-up; additional medical treatment is necessary in 28–70% of treated eyes and retreatment in 30–50% (Dickens and Nguyen, 1995; Lin et al., 2004).

The success of the treatment varies with the energy used: high energy increases the efficacy but also the rate of complications.

Transscleral contact diode laser photocoagulation reduces the IOP by 35–43% from pretreatment levels with a single treatment; the need for pressure-reducing drugs is reduced by approximately 50%, with improvements in the quality of life and compliance with medical therapy.

Retreatment is necessary in 45% of all cases (Pucci and Tappainer, 2003).

The efficacy of the treatment seems to be positively correlated with the age of the patient, inversely correlated with previous surgical procedures and the type of glaucoma: higher rates of success are reported in cases of open-angle, inflammatory, or neovascular glaucoma (Schlote and Derse, 2001).

Excimer laser trabeculotomy

Excimer laser trabeculotomy (ELT) is a new minimally invasive method for treatment of open-angle glaucoma that can easily be combined with cataract surgery.

Laser spots are applied on to trabecular meshwork via an endoscopic fiber and a gonio lens (Fig. 2). In contrast to ALT, shunts between the anterior chamber and Schlemm’s canal are prepared by a photoablative laser, thus increase the outflow of aqueous humor (Herdener and Pache, 2007).