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of the attack or after drug therapy aimed at reducing the intraocular pressure (IOP) and attenuating inflammation of the iris and corneal edema.

Narrow-angle glaucoma with positive results in provocative tests: treatment is indicated in young, high-risk patients with positive family histories.

Pigment dispersion syndrome and the initial phases of pigmentary glaucoma: the aim here is to eliminate iris concavity and iris-zonular contact. The long-term efficacy of laser therapy in this syndrome has not been demonstrated although its use is supported by the results of numerous studies (Gandolfi et al., 1996; Lagreze et al., 1996; Scuderi et al., 1997; Carassa et al., 1998).

Preparation for argon laser trabeculoplasty (ALT).

Contraindications

The main contraindications are corneal opacity, neovascularization of the iris, and athalamia.

Patient preparation

After the patient’s informed consent has been obtained, miotic drops (e.g., dapiprazole 0.5% or pilocarpine 2% or 4%) are usually administered to constrict the pupil and reduce the thickness of the iris so that it can be perforated more easily. Pilocarpine is a more effective miotic than dapiprazole, but it also causes greater congestion of the iris vessels, which increases the risk of bleeding. Systemic administration of acetazolamide or topical application of 1% apraclonidine 1 h before and immediately after the treatment prevents IOP increases and reduces the bleeding of the iris. Laser treatment is performed under topical anesthesia with 4% benoxinate or 4% oxybuprocaine.

Technique

Peripheral iridectomy must be performed in the upper quadrants, approximately 2/3 of the distance between the margin of the pupil and the limbus. The iridotomy is then covered by the upper

eyelid to prevent monocular diplopia. This is particularly important for the large iridotomies created with an argon laser; the location is less important for small YAG iridotomies. The thinner areas of the iris, such as the crypts, are the preferred treatment sites. Visible blood vessels should be avoided.

Peripheral laser iridectomies can be done with an argon laser or with an Nd:YAG laser, with the aid of an Abraham or Wise contact lens. Both lasers are effective, but they have different features. The predominant effect of the argon laser is photocoagulation with energy absorption by the iris pigment; the YAG laser produces photodestruction through a chromophoreindependent mechanism. Many authors prefer the Nd:YAG treatment because it is simpler to perform, uses less energy, and is associated with a lower rate of iridotomy closure than argon laser treatment. However, in eyes with visible iris vessels and for patients on anticoagulants, the iridotomy site should ideally be pretreated with argon.

Nd:YAG laser iridectomy

The Nd:YAG laser is the laser of choice for iridectomies.

Power consumption ranges from 1 to 6 mJ. One or more impacts are needed to perforate the iris. Depending on the model, applications consisting of pulse trains or a single pulse may be used; the spot diameter ranges from 50 to 70 mm. Use of a converging contact lens equipped with a magnification area improves laser-spot focusing and reduces energy consumption.

Perforation of the iris is generally accompanied by movement of the aqueous humor, together with particles of iris pigment, from the posterior to the anterior chamber (Fig. 1). Perforation can be verified by the use of transillumination, which allows visualization of the choroidal reflex through the gap in the stroma of the iris.

Mild, posttraumatic hemorrhage is a common finding. It can be controlled by exerting light pressure on the cornea for 10–20 s with the contact lens. If this is not sufficient, argon treatment with long-duration pulses can be used to coagulate the edges of the treatment area.