Fig. 14.1
Each type of laser emits a specific wavelength of energy and this determines its mechanism of action
There are various types of laser treatments, suitable for every form of glaucoma (Fig. 14.1). They include the iridotomy for closed-angle glaucoma with pupil block, iridoplasty for en plateau irises, trabeculoplasty for open-angle glaucoma, cyclo-photocoagulation of the ciliary body for neovascular or refractory glaucoma. Moreover, the laser may also be used after glaucoma surgery to modulate the postoperative IOP through lysis of the sutures following the trabeculectomy or perforation of the Descemet membrane following canaloplasty (goniopuncture).
Fig. 14.2
Iridotomy. The objective of the iridotomy is to create small, full-depth holes in the peripheral iris tissue to reduce the pupil block in closed-angle glaucoma (either chronic or following an acute attack). The iridotomy is also indicated in pigmentary glaucoma with the inverted pupil block
Iridotomy (Fig. 14.2)
The iridotomy procedure is traditionally contraindicated in the following cases:
Corneal edema
Iris-corneal contact
Iris rubeosis
Anticoagulant therapy
This method generally involves the use of a Neodimium-yag: Q-switched laser and includes the following steps:
Instillation of 1–2 drops of pilocarpine 30–60 min prior to treatment to thin the iris tissue and provide better vision of the crypts;
Treatment inside an iris crypt (if possible), preferably in the superior sector between 10 and 2 o’clock to avoid diplopia, and in the peripheral section, between the internal 2/3 and the external 1/3 of the distance between the pupil edge and the limbus, to avoid the block of the iridotomy by the crystalline or by the ciliary body (Fig. 14.3).
Fig. 14.3
Corrected localization od laser beam during iridotomy
The laser parameters for the iridotomy procedure are described in Table 14.1.
Fig. 14.4
The most popular lenses used for the iridotomy are the Abraham lens with an optic disk of +66D and the Wise lens with an optic disk of +103D
Table 14.1 Laser iridotomy parameters.
Iridotomy: laser settings | |
|---|---|
Power | 3–10 mJ |
Exposition time | 30 ns–20 ps |
Spot number | 1–2 |
Spot target | Between the inner 2/3 and the outer 1/3 of pupillary border and limbus distance |
Generally-speaking, this is an extremely low risk procedure. The most frequent complications observed are pressure spikes 2–3 h from treatment, iritis, small areas of sub-capsular opacity of the crystalline, rare episodes of retinal detachment, cystoid macular edema or late closure of the iridotomy.
Iridoplasty (or Gonioplasty)
Fig. 14.5
(a–c) This is photocoagulative treatment of the extreme peripheral iris that induces retraction and atrophy with consequent widening of the camerular angle
The indications for iridoplasty are:
En plateau iris (that can be associated with an iridotomy procedure to eliminate the effect of the pupil block)
Nanophthalmos
Sectorial angle stricture
Contraindications to iridoplasty are:
Marked corneal opacity
Excessively low AC
Fig. 14.6
The technique involves the use of a laser: argon or krypton and the use of the Ritch gonioscopy lens
The laser parameters are described in Table 14.2.
Table 14.2 Laser iridoplasty parameters.
Iridoplasty: laser settings | |
|---|---|
Spot diameter | 150–200 μm |
Power
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