Ординатура / Офтальмология / Английские материалы / Oxford American Handbook of Ophthalmology_Tsai, Denniston, Murray_2011

PIGMENT DISPERSION SYNDROME (PDS) 277

Pigment dispersion syndrome (PDS)

This describes the release of pigment from the mid-peripheral posterior surface of the iris, from where it is distributed around the anterior segment. Pigment release is thought to occur as a result of posterior bowing of the mid-peripheral iris rubbing against the zonules.

This unusual iris configuration may be due to reverse pupillary block in which there is a transient increased IOP in the AC relative to the posterior chamber. This theory is supported by an observed improvement in the condition when treated with miotics or YAG PI.

Risk factors

•Myopia.

•Age: 20–40.

•Male sex.

•Race: Caucasian.

Clinical features

•Pigment on the corneal endothelium (sometimes in a vertical line—Krukenberg spindle), pigment elsewhere (e.g., in the AC), midperipheral spoke-like transillumination defects; increased rate of lattice degeneration (see Table 10.5).

•Gonioscopy: open angle, concave peripheral iris, 360*dense homogeneous pigmentation of the TM, and may be anterior to Schwalbe’s line inferiorly.

•Pigment in the anterior vitreous (Scheie’s line).

Pigmentary glaucoma

Glaucoma may develop in 10–35% of patients with PDS. Often OHT will resolve with age, as less pigment is available to be released and obstruct the TM.

Clinical features

•Usually asymptomatic, but blurred vision, halos, and red eye(s) may occur after acute pigment shedding following mydriasis or exercise (pigment storm).

•Increased IOP ± corneal edema (if acute); features of PDS (see above); optic disc changes and visual field defects as for POAG (p. 269).

Treatment

•Topical: as for POAG; miotics have theoretical benefits (minimize iridozonular contact) but tend to be poorly tolerated in this age group and carry a small risk of inducing retinal detachment (myopia, lattice degeneration).

•ALT or SLT particularly effective early on; >50% failure rate by 5 years

•Trabeculectomy: similar success rate to that for surgery in POAG, but increased risk of hypotony maculopathy (especially if augmented with antimetabolites).

•PI: controversial use; despite theoretical benefits of normalizing iris configuration and minimizing pigment release, there are no trial data to support its use.

NEOVASCULAR GLAUCOMA (NVG) 279

Neovascular glaucoma (NVG)

Vasoproliferative factors, typically a product of posterior segment ischemia (diabetes or CRVO), promote neovascularization of the angle leading to the formation of a fibrovascular membrane over the trabecular meshwork. Initially, the neovascular vessels cover the trabecular meshwork so that the angle appears open, but with time, peripheral anterior synechiae form and the membrane contracts to zip the angle shut.

Ischemic CRVO and diabetes each account for around a third of the cases of neovascular glaucoma.

Causes include

•Ischemic CRVO (common); risk of progression to NVG is 50%.

•Diabetic retinopathy (common); risk of NVG is highest in PDR.

•Other vascular disorders: ocular ischemic syndrome, central retinal artery (CRAO) and branch retinal vein (BRVO) occlusion.

•Other retinal disease: chronic retinal detachment, sickle cell retinopathy.

•Chronic inflammation.

•Retinal or choroidal tumors.

Clinical features

•Pain is often a feature and may be severe; the predisposing condition may be known or may be suggested by the history (e.g., sudden loss of vision a couple of months previously in cases of CRVO).

•Iris rubeosis: abnormal or nonradial vessels at pupil; increased IOP; AC flare/cells, hyphema; ectropion uvea; conjunctival injection and corneal edema if acute IOP rise or decompensation if chronic; disc changes and field loss as for POAG (p. 269).

•Gonioscopy: abnormal vessels in the angle; fibrovascular membrane overlying the TM (open angle type) or membrane + peripheral anterior synechiae (PAS) zipping angle shut (angle closure type).

Investigation (to determine cause)

•Dilated funduscopy in all cases.

•Carotid Doppler: if no retinal pathology or asymmetric diabetic retinopathy.

•B-scan ultrasound: if poor fundus view (cataract may be associated with chronic retinal pathology such as tumors, detachment, inflammation).

Treatment

•Underlying pathology: panretinal photocoagulation (PRP) for retinal ischemia; retinal reattachment for RD; carotid endarterectomy (CEA) for suitable carotid artery stenosis

•Glaucoma: mydriatic (e.g., atropine 1% 2x/day) + topical steroid (e.g., prednisolone 1% q1–4h) + ocular hypotensive agents as for POAG. If medical treatment fails, consider trabeculectomy (high rate of failure), tube-shunt procedures, or cyclodestruction (e.g., cyclodiode and cyclocryotherapy) depending on visual prognosis.

280CHAPTER 10 Glaucoma

•Pain: if the eye is blind and painful, consider retrobulbar alcohol or evisceration/enucleaton.

•Off-label intravitreal or intracameral injections of recombinant anti– vascular endothelial growth factor (anti-VEGF), bevacizumab (Avastin), or ranibizumab (Lucentis) result in rapid regression of rubeosis and are often used in combination with PRP. Anti-VEGF agents do not reverse ischemia or decrease the production of VEGF, so therapy targeting the underlying process is vital.

•If IOPs permit, many surgeons opt to wait 2 or more days after an anti-VEGF injection, prior to surgery, to reduce the amount of

neovascularization, which may decrease the incidence of intraoperative or post-operative hyphema.

•Anti-VEGF agents may also play a role in decreasing tube-shunt or trabeculectomy bleb failure from aggressive fibrous encapsulation.

INFLAMMATORY GLAUCOMA: GENERAL 281

Inflammatory glaucoma: general

Raised IOP in the context of intraocular inflammation is a common clinical problem. The challenge is to elucidate the time course (acute vs. chronically elevated IOP), the state of the angle (open vs. appositional closure vs. synechial closure), and the underlying mechanism.

Therapy may be made difficult because of marked fluctuations in IOP (ciliary body shutdown l dIOP; trabeculitis l iIOP, and concerns over whether anti-inflammatory treatment could be making things worse, steroid-induced glaucoma]).

Open-angle type

Acute

•Mechanism: acute trabeculitis (particularly with HSV, VZV), trabecular meshwork blockage.

Clinical features

•Elevated IOP; open angle; signs of uveitis with or without keratitis; IOP returns to normal after acute episode of inflammation.

Treatment

•Inflammatory process: treatment of underlying cause may be sufficient (e.g., topical steroids and mydriatic for anterior uveitis; p. 325).

•Increased IOP: if there are features of concern (e.g., IOP >30 mmHg; sustained increased IOP; vulnerable optic disc), consider topical (e.g., B-blocker, carbonic anhydrase inhibitor) or systemic

(e.g., acetazolamide) medication for as long as required.

Chronic

• Mechanism: trabecular scarring; chronic trabeculitis.

Clinical features

•Increased IOP; open angle; no active inflammation but may have signs of previous episodes; ± disc changes or field defects (p. 264).

Treatment

•Medical: as for POAG; prostaglandin agonists are occasionally useful but may exacerbate inflammation.

•If medical treatment fails, consider trabeculectomy (which has poorer results than for POAG, but improves if augmented) or tube procedure.

•If surgical treatment fails, consider cyclodestruction (e.g., cyclodiode), but there is a significant risk of phthisis.

Steroid-induced glaucoma

Although related to the treatment rather than the underlying disease process, this is an important differential diagnosis of inflammatory glaucoma. Raised IOP due to steroids requires a reduction in the potency and frequency of topical corticosteroids, whereas if it is due to uncontrolled inflammation, the steroid dose may need to be increased.

If patients require large or frequent doses of steroids or develop an adverse response to steroids, it is often advisable to initiate systemic immunomodulatory therapy (methotrexate, cyclosporine, etc).

282 CHAPTER 10 Glaucoma

Angle closure type

With seclusio pupillae

•Mechanism: 360*posterior synechiae (seclusio pupillae) block anterior flow of aqueous humor, causing iris bombé and appositional angle closure.

Clinical features

•Increased IOP; seclusio pupillae; iris bombé; shallow AC; angle closure (appositional); signs of previous inflammatory episodes.

Treatment

•Inflammatory process: minimize posterior synechiae formation by rapid and effective treatment of anterior uveitis (consider subconjunctival steroid injection).

•Increased IOP: Nd-YAG PI needs to be larger than is necessary for acute-angle closure glaucoma (AC will be shallow, so watch out for the corneal endothelium), and surgical PI may be necessary if Nd-YAG PI closes, although there is a high chance that PI will close

if the inflammatory response is not well controlled. Consider topical (e.g., B-blocker, carbonic anhydrase inhibitor) or systemic (e.g., acetazolamide) medication as a temporary measure or for as long as required.

With synechial closure

•Mechanism: peripheral anterior synechiae may zipper the angle closed; the risk of synechial closure is increased in presence of granulomatous inflammation and possibly pre-existing narrow angles.

Clinical features

•Increased IOP, shallow AC, PAS with angle closure, signs of previous inflammatory episodes.

Treatment

•Medical: as for POAG, but some practitioners would advise caution with prostaglandin agonists.

•If medical treatment fails, consider trabeculectomy (augmented) or tube shunt.

•If surgical treatment fails, consider cyclodestruction (e.g., cyclodiode), but there is a significant risk of phthisis.

•If >25% of angle remains open, consider Nd-YAG PI to deal with any pupillary block component.

•Goniosynechiolysis has been shown to be effective if synechiae have been present for <6 months.

INFLAMMATORY GLAUCOMA: SYNDROMES 283

Inflammatory glaucoma: syndromes

Posner–Schlossman syndrome (glaucomatocyclitic crisis)

This syndrome of recurrent unilateral episodes of very high IOP typically affects young males. The cause is not known; acute trabeculitis has been postulated, possibly secondary to HSV or cytomegalovirus (CMV).

Clinical features

•Blurring of vision, halos, painless.

•Increased IOP (40–80 mmHg), white eye, minimal flare, occasional cells/fine keratic precipitates, no synechiae (PS or PAS), open angle.

Treatment

•Inflammatory process: topical steroid (e.g., dexamethasone 0.1% 4x/day).

•Increased IOP: consider topical (e.g., B-blocker, A2-agonist, carbonic anhydrase inhibitor) or systemic (e.g., acetazolamide) agents according to IOP level.

•Consider oral acyclovir for HSV or valganciclovir for CMV.

Fuchs’ heterochromic iridocyclitis

This syndrome of mild chronic anterior uveitis, iris heterochromia, and cataract may be complicated by glaucoma in 10–30% cases. It typically affects young adults and there is no sex bias. It is unilateral in >90% cases.

Clinical features

•Decreased vision due to cataract; floaters; often asymptomatic.

•White eye, white, stellate keratitic precipitates (KPs) over whole corneal endothelium, mild flare, few cells, iris atrophy (washed out, moth-eaten), transillumination defects, abnormal iris vessels, iris heterochromia (a dark iris becomes lighter; whereas a light iris may become darker), iris nodules, cataract (posterior cortical/subcapsular), vitritis, increased IOP.

•Gonioscopy: open angle; ± twig-like neovascularization of the angle associated with hyphema during cataract surgery.

Treatment

•Inflammatory process: treatment is not usually necessary.

•Increased IOP: treat as for POAG (p. 269).

284 CHAPTER 10 Glaucoma

Lens-related glaucoma

Lens-related glaucoma may result from abnormalities of lens size, lens position, release of lens protein (mature cataract, trauma, surgery), and/or the consequent inflammatory response.

Phacomorphic glaucoma

The enlarging lens causes pupillary block and anterior bowing of the iris with secondary angle closure. In an eye of normal axial length, this occurs secondary to an intumescent cataractous lens; in a short eye, this may result simply from the normal increase in lens size with age.

Clinical features

•Increased IOP, shallow AC, fixed semidilated pupil, swollen cataractous lens.

•Ipsilateral closed angle (appositional; sigma sign may be seen on indentation gonioscopy).

•Contralateral angle is open with deep AC (in contrast to PACG).

Treatment

•Medical (topical and systemic): as for PACG.

•Nd-YAG PI to reverse pupillary block component.

•Early cataract extraction is the definitive treatment.

Phacolytic glaucoma

The hypermature cataract loses soluble lens proteins through the anterior capsule, causing trabecular obstruction and subsequent secondary openangle glaucoma.

Clinical features

•Increased IOP, lens protein in a deep AC (may form a pseudohypopyon), hypermature or mature cataract, open angle (with lens protein); AC tap reveals lens protein and foamy macrophages.

Treatment

•Medical: topical (e.g., B-blocker, A2-agonist, carbonic anhydrase inhibitor) or systemic (e.g., acetazolamide) agents as required.

•Early cataract extraction.

Phacoanaphylactic uveitis

This is an inflammatory reaction to lens protein, usually following traumatic capsular rupture or postoperative retention of lens material (when it must be distinguished from endophthalmitis). This insult may also cause sensitization such that lens protein exposure in the contralateral eye (surgery, hypermature or mature cataract) may be associated with an aggressive inflammatory response.

Clinical features

•Recent trauma or surgery, exposed lens protein, AC flare + cells with or without hypopyon, KPs, synechiae (posterior synechiae + PAS), angle usually open (but may have PAS); IOP may be high, normal, or low.

LENS-RELATED GLAUCOMA 285

Treatment

•Inflammatory process: topical steroid (e.g., dexamethasone 0.1% hourly) and surgical removal of any retained lens fragments.

•Increased IOP: medical: topical (e.g., B-blocker, A2-agonist, carbonic anhydrase inhibitor) or systemic (e.g., acetazolamide) agents as required.

•Treat for contralateral cataract.

Glaucoma secondary to lens subluxation/dislocation

There is pupillary block by anterior lens subluxation or complete dislocation into the AC; there may also be a coincident angle abnormality (e.g., Marfan syndrome).

Clinical features

•Increased IOP, subluxed/dislocated lens, ± corneal edema (if acute or lenticulocorneal touch).

Treatment

•Positional: dilate and have patient lie supine (to encourage gravitydriven posterior movement of lens), and constrict (to keep lens safely behind pupil); long-term miotic therapy may be needed unless the lens dislocates safely into the vitreous.

•Occasionally, in cases of anterior lens dislocation associated with loose zonules, such as in microspherophakia, miotics are contraindicated, as they decrease tension on zonules and exacerbate anterior dislocation. In these situations, cycloplegics are indicated to maintain tension on zonules and posterior position of the lens diaphragm.

•Consider lens extraction if positional measures fail, if there is complete dislocation into the AC, or if there is a cataract or recurrent problem.