166  OPHTHALMOLOGY SECRETS IN COLOR

may develop or progress after an attack. Cataract extraction can be beneficial for IOP control in primary angle-closure glaucoma.

•Zonules: Zonular weakness may not manifest until much later, i.e., during cataract extraction or spontaneous subluxation or dislocation.

•Gonioscopy: PAS.

•Optic nerve: Disc congestion and swelling, if present, may take several days to resolve. Acute attacks typically produce more pallor than cupping. Chronic angle closure usually produces more cupping than pallor, similar to open-angle glaucoma. OCT may show a loss of ganglion cells and thinning of the retinal nerve fiber layer.

•Retina: “Decompression retinopathy” may be seen after rapid lowering of the IOP as scattered intraretinal hemorrhages concentrated more around the posterior pole and optic nerve. Peripapillary atrophy can also develop over time, along with focal nerve-fiber bundle defects, diffuse thinning of the retina, etc.

29.What types of medications are contraindicated in narrow-angle glaucoma?

Topical and systemic sympathomimetic and anticholinergic medications should be avoided by people with eyes that have narrow and potentially occludable angles until a prophylactic laser iridotomy is performed. These are found in many over-the-counter antihistamine and cold remedies, antispasmodics for overactive bladder, and some antiparkinsonian agents. These medications are not contraindicated in patients with eyes that have narrow but not occludable angles, or eyes with a patent iridotomy, or in patients with open-angle glaucoma.

Use miotics with caution in patients with narrow angles, regardless of occludability, because of the risk of causing further narrowing by anterior displacement of the lens–iris diaphragm. These patients should at least have repeat gonioscopy after commencing miotic therapy to rule out this possibility. If the angles do become significantly narrower, one must consider discontinuation of miotic therapy or performing a prophylactic PI, if there is a compelling reason for continuing miotic therapy.

KEY POINTS: LONG-TERM SEQUELAE OF AN ACUTE PRIMARY ANGLE-CLOSURE ATTACK

1. Corneal endothelial cell loss, endothelial pigment.

2. Permanently middilated and unreactive pupil.

3. Iris sector atrophy, posterior synechiae.

4. Peripheral anterior synechiae in the angle.

5. Glaukomflecken, other cataractous changes.

6. Occasionally, lens zonular weakness (may be causative). 7. Optic nerve pallor out of proportion to cupping.

30.List some possible causes for persistent or recurrent intraocular pressure elevation after a successful peripheral iridotomy.

•PAS formation and/or undetected injury to the TM during the period of angle closure

•Nonpupillary block angle closure (see question 10, classification, II.A.1 to 4.)

•Incomplete iridotomy will result in persistent IOP elevation. Occlusion of the iridotomy with debris or a membrane may cause a recurrent episode of pupillary block angle closure. Remember that transillumination does not equal patency.

•Underlying or residual trabecular meshwork dysfunction—chronic apposition of iris to trabecular meshwork can induce trabecular dysfunction even in the absence of PAS.

PLATEAU IRIS

31.What is plateau iris configuration?

Anteriorly positioned (and sometimes larger than normal) ciliary processes push the peripheral iris more anteriorly than normal (Fig. 16-7). The central AC is usually slightly shallow or normal depth, but the angle recess is narrower than the depth of the AC would suggest. The iris has a relatively flat contour, with a sharp peripheral drop-off at the angle approach. This finding is designated “p” in our

CHAPTER 16  ANGLE-CLOSURE GLAUCOMA  167

Figure 16-7.  Ultrasound biomicroscopy image of the anterior segment of an eye with plateau iris. Note the large ciliary processes causing anterior displacement of the peripheral iris and angle closure, whereas the central iris remains flat.

gonioscopic system. A component of pupillary block is frequently present. With dilation, the peripheral iris folds into the angle and occludes the TM.

32.How does plateau iris present clinically?

It may be noted on routine examination or present as an acute or chronic angle-closure glaucoma.

33.Describe the epidemiology of plateau iris.

Traditional teachings describe patients with plateau iris configuration (PIC) as usually younger (typically fourth and fifth decades) and less hyperopic than patients with primary angle closure; they may even be myopic. With the advent of anterior segment imaging devices such as UBM, it has been found that plateau iris configuration is quite common in both Asians and Caucasians—about 20 to 30% of the population has PIC. PIC refers to a narrow angle with steep iris on gonioscopy despite a patent iridotomy; however, the IOP is normal in the plateau iris configuration. Eyes with PIC can develop elevated IOP acutely (APAC) or chronically (PAC). Traditionally, PIC eyes with elevated IOP, either acutely or chronically, are referred to as having plateau iris syndrome. It is unclear how many PIC eyes will progress to APAC or PAC. We suspect that only a small percentage of PIC patients will develop elevated IOP. However, we are still unable to identify which subset of PIC will progress to APAC or PAC.

34.How can plateau iris be distinguished from relative pupillary block (primary) angle closure on slit lamp examination?

Primary angle closure normally presents with a shallow central AC and moderate to significant iris convexity, which is in contrast to the appearance of PIC noted above. With indentation gonioscopy, the angle is much harder to open and does not open as widely as a typical narrow angle. A “hills and valleys” profile may be seen when looking at the angle. In addition, indentation gonioscopy reveals the almost pathognomonic “double hump sign,” characterized by posterior displacement of the midperipheral iris but a persistently anterior position of the peripheral iris. Persistence of the plateau iris appearance despite a patent iridotomy confirms the diagnosis clinically. High-resolution UBM can also confirm the diagnosis.

35.What is plateau iris syndrome?

Plateau iris syndrome is an acute or chronic angle closure that develops with dilation, or even spontaneously, in an eye with plateau iris configuration and a patent PI.

36.How is plateau iris syndrome treated?

PIC is a subset of PACS. Plateau iris syndrome (PIS) is APAC or PAC secondary to plateau iris configuration. The treatment of PIC or PIS is similar to the treatment of PACS, PAC, or APAC.

The primary procedure of choice in an eye with (or at risk for) angle closure is laser peripheral iridotomy, to eliminate any component of pupillary block that may be present. In general, the older the patient, the more the pupillary block contributes, as a percentage, to the mechanism of angle closure. However, laser iridotomy is not adequate treatment in these cases; it is merely the necessary

168  OPHTHALMOLOGY SECRETS IN COLOR

first step. Eyes with PIC often require other treatments to open the angle, especially if the patient has symptoms of intermittent angle closure or a positive prone darkroom test. It is essential to perform gonioscopy after the iridotomy to verify the angle status.

Laser peripheral iridoplasty may be necessary in patients whose angle approach remains very narrow despite a patent PI. This technique uses the argon laser to apply burns circumferentially to the peripheral iris, which cause it to contract and pull away from the angle. Although the green wavelength is usually used, use of the yellow-green wavelength may improve absorption of laser energy in more lightly colored irides. One important potential complication that should always be discussed with the patient is the risk of a permanently larger pupil size postoperatively and its attendant potential to increase problems with glare. Avoiding vessels is also important to prevent anterior ischemia.

Chronic miotic therapy can also be a useful alternative or adjunct to iridoplasty in eyes with a narrow approach despite a patent PI. With either method of therapy, the angle should be examined with gonioscopy after instillation of pilocarpine and at regular 6- to 12-month intervals afterward, to document the effect on angle configuration.

37.Are angles always open after a successful laser peripheral iridotomy?

No. About 20 to 40% of PACS eyes still have narrow angle even after a successful laser peripheral iridotomy. To reiterate, PACS eyes do not have elevated IOP. Angles can remain narrow after a successful laser PI with normal IOP. The possible mechanisms of narrow angle after laser PI are plateau iris configuration, thick peripheral iris (often found in Chinese PACS eyes), and lens-related mechanisms. Other secondary causes of angle narrowing should be sought as well. See question 10.

AQUEOUS MISDIRECTION SYNDROME (MALIGNANT/CILIARY BLOCK GLAUCOMA)

38.What is aqueous misdirection syndrome?

Posterior misdirection of aqueous into the vitreous cavity causes an anterior displacement of the lens– iris diaphragm. It most commonly occurs in eyes with narrow angles after ocular (typically glaucomafiltering as well as cataract) surgery, but can occur after laser procedures or, rarely, spontaneously.

Miotic use and previous angle-closure glaucoma increase the risk of occurrence. It typically presents within the first postoperative week with a shallow to flat anterior chamber and a high IOP, but the IOP may be normal in an eye with a functioning filter. Serous choroidal effusion/detachment, pupillary block, and suprachoroidal hemorrhage should be ruled out.

39.Why does aqueous misdirection occur? How does it present clinically?

It is still unclear why aqueous misdirection occurs. It is not an uncommon entity in glaucoma patients who undergo cataract or glaucoma surgery, especially in those with angle-closure glaucoma. It

is hypothesized that a spontaneous or induced choroidal effusion in an eye with an impermeable vitreous can cause anterior chamber shallowing from a posterior pushing mechanism (the vitreous pushing the lens–iris diaphragm). This hypothesis makes clinical sense as aqueous misdirection often occurs during the surgery when the anterior chamber volume is not maintained, leading to a transient hypotony.

Aqueous misdirection can occur during surgery or postoperatively. Patients will present with blurred vision with myopic shift (forward movement of lens). On slit lamp examination, the anterior chamber is diffusely shallow, both centrally and peripherally, in contrast to pupillary block, in which the anterior chamber is more shallow peripherally than centrally. The IOP is usually high to normal.

40.How is aqueous misdirection treated medically?

•Cycloplegics relax the ciliary muscle, which increases zonular tension and pulls the lens–iris diaphragm posteriorly. Cycloplegics are also essential in the management of angle closure due to anterior rotation of the ciliary body. They may be required indefinitely.

•Aqueous suppressants.

•Hyperosmotic agents.

•Miotics are contraindicated.

41.How can aqueous misdirection be treated with laser if it is unresponsive to medication?

The goal of therapy is to reestablish aqueous flow from the posterior chamber to the anterior chamber and to try to create a channel for aqueous flow from the posterior segment to the anterior segment.