Chapter 131 – Cystoid Macular Edema
• A pathological response consisting of fluid accumulation in the outer plexiform layer of the central macula that results in the formation of visible cystic spaces.
• Serous fluid accumulation in multiple cystoid spaces.
• Thickening of the central macula.
• Loss of the normal foveal depression.
• Best detected by slit-lamp biomicroscopy with a contact or handheld lens.
• A petalloid pattern of dye leakage from the perifoveal capillaries on fluorescein angiography.
• Conjunctival injection.
• Aqueous and/or vitreous cell and flare.
• Optic disc edema.
• A variety of ocular conditions, including aphakia, pseudophakia, inflammation, tumors, vascular abnormalities, dystrophies, medication usage, and foveal traction.
Cystoid macular edema (CME) represents a “final common pathway” response of the retina to a variety of possible insults. It has been reported in association with vascular problems (such as diabetes and retinal vein obstruction), inflammatory conditions (such as pars planitis), inherited diseases (such as retinitis pigmentosa or dominant CME), tractional problems (such as vitreomacular traction syndrome), and use of medication such as epinephrine (adrenaline) or latanoprost, but its most common setting is following cataract surgery ( Box 131-1 ).
Postcataract CME was initially reported in 1953 by Irvine. It represents a common clinical problem that, for the most part, is self-limited. The management challenge arises in the chronic and persistent case, for which a stepwise therapeutic approach is optimal. The clinician must always be alert to the possible side effects of the many effective, but potentially toxic, pharmaceutical agents used to treat this entity. In addition, surgical management should be considered for unremitting cases of CME.
EPIDEMIOLOGY AND PATHOGENESIS
CME is a common condition associated with intraocular inflammation, vitreoretinal traction, and vascular incompetence; CME following cataract surgery is known as the Irvine-Gass syndrome.  Intracapsular cataract extraction is associated with angiographically evident CME in 60% of uncomplicated cases. Extracapsular cataract extraction is associated with angiographically evident CME in 20% of uncomplicated cases. In the majority
Ocular Conditions Associated with Cystoid Macular Edema
• Cataract surgery
• Penetrating keratoplasty
• Astigmatic corneal incisions
• Scleral buckling
• Laser iridotomy
• Cryotherapy for retinal break
• Panretinal photocoagulation
• Retinitis pigmentosa
• Autosomal dominant cystoid macular edema
• Topical epinephrine
• Nicotinic acid
• Choroidal melanoma
• Choroidal hemangioma
• Retinal capillary hemangioma
• Idiopathic epiretinal membrane
• Vitreomacular traction syndrome
• Eales’ disease
• Cytomegalovirus retinitis
• Pars planitis
• Behçet’s syndrome
• Birdshot choroidopathy
• Idiopathic vitritis
• Diabetic retinopathy
• Retinal vein obstruction
• Ocular ischemic syndrome
• Idiopathic juxtafoveal telangiectasias
• Choroidal neovascularization
• Coats’ disease
• Acute hypertensive retinopathy
• Radiation retinopathy
• Retinal arterial macroaneurysm
of these eyes, no retinal thickening is apparent and no decrease in the visual acuity occurs. Clinically significant CME with decreased visual acuity following modern cataract surgery is seen in only 0.2 to 1.4% of eyes.  Although planned posterior capsulorrhexis at the time of phacoemulsification does not lead to an increased prevalence of CME, those with inadvertent rupture of the posterior capsule and/or persistent vitreous traction to anterior segment structures are at highest risk. Neodymium:yttrium-aluminum-garnet (Nd:YAG) capsulectomy, when performed at least 3 months after cataract surgery, does not appear to increase the incidence of CME. Diabetics who have any degree of retinopathy have an increased incidence of postcataract CME.
Also, CME can occur after other types of intraocular surgery. It is especially common after penetrating keratoplasty in eyes that require concurrent vitrectomy.  In a retrospective study, 6 of 14 eyes (43%) receiving a posterior chamber intraocular lens (PCIOL) implantation with scleral fixation had angiographic macular edema that was a cause of low final visual acuity. It has been reported following retinal detachment repair and glaucoma filtering procedures as well. In phakic eyes it nearly always resolves spontaneously.
The mechanisms by which postoperative CME has been postulated to occur include vitreomacular traction, vascular compromise, and prostaglandin (PG) secretion and inflammation, although the exact cause remains unknown. Regardless of the initial insult(s), the fluid accumulation in CME is the direct consequence
Figure 131-1 Prostaglandin synthesis pathway and inhibitory agents.
of damage to the retinal vascular endothelium. When extracellular fluid in the central macula accumulates in the outer plexiform layer, cystoid spaces can develop due to the horizontally loose intracellular adhesions.
Although many mechanisms may be active in the genesis of CME, the most important is intraocular inflammation. It is clear that many affected patients exhibit signs and symptoms of intraocular inflammation that may respond to anti-inflammatory agents. Figure 131-1 illustrates the synthesis of PGs and the sites of action of corticosteroids and cyclo-oxygenase inhibitors (COIs). The formation of the end product in this pathway, PGs, can be blocked at the outset by corticosteroids. Step two in this pathway, which leads to the formation of endoperoxidases, can be blocked by COIs.
Aside from the postcataract patient, CME occurs most commonly in the setting of diabetic retinopathy, in which case associated microaneurysms and hard exudates are often evident. In most diabetics, CME occurs along with diffuse macular edema; however, rarely it is an isolated problem. While the Early Treatment Diabetic Retinopathy Study demonstrated the visual benefit of focal photocoagulation for clinically significant macular edema, the CME component does not respond as well to laser photocoagulation. Panretinal photocoagulation for high-risk characteristics in diabetics can result in CME, which is usually self-limited.
Retinal vein obstructions represent another common retinal vascular cause of CME. Both branch and central vein occlusions can result in severe macular edema. In these conditions it is due to hypoxic capillary endothelial damage secondary to increased intravascular hydrostatic pressure. Branch vein occlusions are associated acutely with a sectoral pattern of dilated and tortuous blood vessels, flame and dot-and-blot hemorrhages, and cotton-wool spots. In the chronic phase, persistent CME, venous sheathing, microaneurysms, collateral vessels, shunts, and hard exudates are seen. The Branch Vein Occlusion Study demonstrated a visual benefit following the application of a grid pattern of photocoagulation to the area of chronic macular edema. Acutely in central retinal vein obstruction, retinal hemorrhages and dilated retinal veins are prominent. In the chronic phase, vascular sheathing, absorption of retinal hemorrhages, and optociliary collateral vessels may develop. The macula may demonstrate CME, epiretinal membrane, and lamellar hole formation. The Central Retinal Vein Occlusion Study showed no visual benefit in the use of grid macular photocoagulation for the treatment of associated macular edema. However, a possible benefit may be seen in younger patients who undergo treatment.
It is not unusual for CME to overlie a choroidal neovascular membrane or a serous retinal detachment. Often it goes unnoticed in light of the accompanying severe subretinal and/or intraretinal abnormalities.
Other, more unusual retinal vascular conditions produce CME. Retinal telangiectasis (also known as Leber’s miliary aneurysms or Coats’ disease) is a unilateral condition that occurs more commonly in males. The retinal vasculature is anomalous and produces leakage with resultant cystoid and diffuse macular edema. The vascular anomalies may be local or widespread. Cryotherapy or laser treatment is applied if these lesions threaten macular function. Idiopathic juxtafoveal telangiectasis can occur in either a unilateral or bilateral pattern. Exudation and CME result in visual loss. Photocoagulation may help to improve vision if there is no spontaneous improvement.
Patients who receive radiation treatment involving the head and neck may develop signs of radiation retinopathy 6 months to 3 years following this treatment. The incidence depends on total dose and the daily fraction, with changes developing most commonly after doses of 3000–3500?rads (30–35?Gy). A bilateral retinopathy occurs in almost one third of patients treated with external beam irradiation. Local plaque therapy requires higher doses than external beam therapy to produce damage. The clinical features of radiation retinopathy mirror those of diabetic retinopathy and include CME. Although no therapy is proved, grid laser photocoagulation is believed to lessen the macular edema.
Acquired retinal arterial macroaneurysms are often multiple and may thrombose and close spontaneously. This entity is treated if lipid exudate threatens the macula or if CME develops. Two modalities of laser treatment to be considered are direct laser treatment to close off the lesions and indirect laser treatment in a tight grid pattern around the macroaneurysm.
Also, CME with choroidal tumors, such as nevi, malignant melanomas, and cavernous hemangiomas, can occur. Intraretinal cystoid changes occur over the tumor and at sites distant from the tumor as a result of lack of oxygenation of retinal tissue.
A multitude of ocular inflammations and infections can result in CME. These include idiopathic uveitis, intermediate uveitis, birdshot retinochoroidopathy, sarcoidosis, toxoplasmosis, posterior scleritis, Harada’s syndrome, and Behçet’s syndrome. The common underlying cause is an inflammatory-mediated breakdown in the blood-retina barrier.
Medications such as epinephrine, nicotinic acid, and latanoprost cause CME rarely. In one study, angiographically visible macular edema occurred in 28% of aphakic eyes under treatment with epinephrine drops for glaucoma versus a 13% incidence in aphakic eyes that did not receive epinephrine. These findings were reversed with cessation of the medication. The mechanism of epinephrine maculopathy may be reduced blood flow in the retina and choroids. Nicotinic acid, a treatment for hypercholesterolemia, is a rarer cause of CME. Tiny cysts are seen in a regular pattern in the foveal region, sparing the anatomical fovea, with no leakage from retinal vessels on fluorescein angiography and a small scotoma near the point of fixation. The fundus findings resolve upon discontinuation of nicotinic acid. Latanoprost in various studies has been associated with CME. As a PG analog, latanoprost is thought to contribute to the disruption of the blood-aqueous barrier and angiographic CME formation in early postoperative pseudophakes.     
Patients who have retinitis pigmentosa can also have CME. Although the precise pathophysiology is not clearly defined, it is felt that the perifoveal capillaries demonstrate increased permeability in such cases. An inherited form of CME exists as well.
The presence of epiretinal membranes and the vitreomacular traction syndrome are associated with CME, particularly in areas of greatest traction and distortion of retinal blood vessels. Management of this condition is to remove the membrane surgically.
Figure 131-2 Cystoid macular edema in the Irvine-Gass syndrome. Note the radial cystoid changes centered in the fovea causing a “yellow spot.”
The major symptom of CME is decreased central visual acuity. Accompanying symptoms may include metamorphopsia, micropsia, scotomata, ocular irritation, photophobia, and conjunctival injection. Presenting visual acuities usually range from 20/25 (6/8) to 20/80 (6/26) but may be as poor as 20/400 (6/133).
Clinically, CME is seen best using the slit lamp and either a contact lens (e.g., Goldmann lens) or a handheld, noncontact lens (e.g., 78D, 60D). The edema results in light scattering due to the multiple interfaces created by the separated retinal cells. This light scattering decreases the neural retina’s translucency so that the normal retinal pigment epithelial and choroidal background patterns are blurred. Individual pockets of fluid in the outer plexiform layer are seen, with the largest pockets centrally and progressively smaller cysts peripherally. Retroillumination can help to delineate the polycystic spaces. As these changes can be subtle and media opacity can affect the view, clinical confirmation of CME may be difficult in certain eyes. A yellow spot, believed to be due to diffusion of the luteal pigment, may be evident in the central macula ( Fig. 131-2 ). Small intraretinal and intracystic hemorrhages, microaneurysms, and telangiectasias may be seen as well.
The underlying cause of CME does not alter its appearance, but the associated ocular findings vary widely depending on etiology.
After cataract surgery, aqueous and/or vitreous cell and flare, optic nerve head swelling, and a ruptured anterior hyaloid face may be evident. Other patients show vitreous traction to anterior chamber structures. Epiretinal membranes are concurrently present in about 10% of eyes. Inflammatory, vascular, tractional, inherited, and tumor-related causes result in the corresponding associated ocular findings.
As a result of CME, a rupture of the inner retinal cyst can occur to give a lamellar macular hole. Prolonged CME may induce atrophy of the macular photoreceptors—visual acuity is poor, but clinical examination and fluorescein angiography may be grossly normal with the exception of a blunting of the foveal reflex.
Fluorescein angiography is much better than clinical examination to show CME. It has been demonstrated that a close relationship exists between mean macular thickening and visual acuity. However, fluorescein angiography yields only qualitative information. Quantitative data on retinal thickness can be derived only with newer techniques such as optical coherence tomography ( Fig. 131-3 ). 
The majority of cases occur between 4 weeks and 12 weeks after cataract surgery.  Rarely, cases can occur years after surgery. Most instances of CME (approximately 75%) resolve spontaneously within 6 months. Two thirds of patients who have intracapsular cataract extraction with CME regain 20/30 (6/10) or
Figure 131-3 Optical coherence tomogram of a patient who has postcataract cystoid macular edema. Note the central cyst, loss of the normal foveal depression, and macular thickening (normal is 165?m).
better vision 3–12 months after surgery. If, however, the surgery is complicated by vitreous loss or incarceration, resolution may be hindered.
DIAGNOSIS AND ANCILLARY TESTING
In eyes with clear media, clinical examination usually yields the diagnosis. Fluorescein angiography is the best ancillary test to assist in the diagnosis—in eyes with hazy media it is especially useful. It reveals a typical petalloid pattern in the central macula secondary to dye leakage from the perifoveal capillaries ( Fig. 131-4 ). The dye accumulates in cyst-like spaces within the outer plexiform layer (Henle’s layer). Late fluorescein angiographic pictures should be taken (up to 30 minutes following injection) to allow time for the dye to accumulate within the anatomical fovea. Also seen on fluorescein angiography is leakage from the disc and retinal vessels.
In cases of aphakic and pseudophakic CME it is critical to perform gonioscopy, which is helpful in diagnosing structural problems of the wound, such as in the iris, capsule, or vitreous, that may be playing a role.
Other methods proposed to quantify macular edema include confocal scanning laser ophthalmoscopy (SLO), retinal thickness analyzers, and optical coherence tomography (OCT). The axial resolution of SLOs has been estimated at 300?µm versus 50?µm for retinal thickness analyzers. OCT provides high-resolution cross-sectional imaging of the retina analogous to B-scan ultrasonography using optical rather than acoustic reflection. Its theoretical axial resolution is 10–14?µm and has been shown to be as effective at detecting CME as fluorescein angiography.    
The differential diagnosis is summarized in Box 131-2 .
Electron microscopy shows that an intracellular accumulation of fluid produces cystoid areas and swelling of Müller’s cells, a condition that is reversible. If excess fluid is present, it may break through cell membranes and accumulate extracellularly, at which stage the condition becomes irreversible.  Histologically, large cystic spaces are seen in the outer plexiform layer ( Fig. 131-5 ).
Medical Treatment ( Box 131-3 )
Corticosteroids act by inhibiting phospholipase A2 , preventing the conversion of membrane lipids into arachidonic acid. Locally, they decrease intracellular and intercellular
Figure 131-4 Fluorescein angiography demonstrates cystoid macular edema very well. A, In the early stage of the angiography, minimal leakage is seen. B, The petalloid leakage pattern, present in the late stages of the angiography, is diagnostic of CME. C, Note the profuse leakage from the optic nerve head in the late stages.
Differential Diagnosis of Cystoid Macular Edema
Stage 1 macular hole
Lamellar macular hole
Rhegmatogenous retinal detachment
Idiopathic epiretinal membrane
X-linked juvenile retinoschisis
Vitreomacular traction syndrome
Diffuse macular edema
edema, suppress macrophage activity, and decrease lymphokine production. Systemically, they sequester T cells out of circulation (inhibiting cytotoxic and recruitment functions) and decrease the enzymatic and phagocytic activity of polymorphonuclear leukocytes.  No well-controlled trial has been undertaken to evaluate corticosteroids in the treatment of chronic aphakic or pseudophakic macular edema.
Topical corticosteroids composed of lipophilic acetate suspensions of prednisolone penetrate the intact corneal epithelium and reach the anterior chamber in higher concentration than water-soluble forms, such as dexamethasone. The relative potency of steroids tested in decreasing order is as follows: dexamethasone 0.1%, prednisolone 1%, fluorometholone 0.1%, rimexolone 1%, loteprednol 0.5%, and medrysone 1%. Phosphate preparations are water soluble and available as solutions—acetate and alcohol preparations are marketed as suspensions.
Significant potential complications of topical corticosteroid therapy include glaucoma, posterior subcapsular cataracts, exacerbations of infections, and corneal problems.
Potent topical corticosteroids such as prednisolone, dexamethasone, and betamethasone, applied four times a day for 6 weeks, cause an elevation of intraocular pressure (IOP) to over 31?mmHg (4.13?kPa) in 5% of the general population (steroid responders). A rise in the range 22–30?mmHg (29.3–3.9?kPa) is exhibited
Figure 131-5 Typical pathological appearance of cystoid macular edema. Large cystoid spaces in the outer plexiform layer of the retina are demonstrated. (Courtesy of Dr W. Spencer.)
by 35% and the remaining population show no pressure response. Less potent steroids, such as fluorometholone, have a lower likelihood of elevating IOP. Of note, anecdotal evidence indicates that the visual acuity of “corticosteroid responders” with postcataract CME improves more than that of patients whose IOP remains normal. This may be explained by a hydrostatic effect.
Posterior subcapsular cataracts can be induced by local (topical and periocular) and systemic corticosteroid administration, with systemic medication being associated with a greater
Stepwise Approach to the Medical Management of CME
A topical indomethacin 1% suspension or topical ketorolac 0.5% (one drop three times a day for 2–6 weeks) may be given as prophylaxis following cataract surgery in addition to concurrent corticosteroid therapy.
Corticosteroids may be beneficial in cases of persistent CME. Many patients show improvement of visual acuity within 1–2 weeks of initiation of intensive topical corticosteroid therapy. The initial treatment consists of topical prednisolone acetate 1% every 2?h while awake, for 3 weeks. With good clinical response, taper and discontinue over 2–3 weeks. A trial of topical therapy also allows the determination of whether the individual will respond to corticosteroid therapy with elevation of IOP. Should the pressure increase, subsequent sub-Tenon’s injections should not be given.
If no improvement occurs with topical therapy, posterior sub-Tenon’s injection of a long-acting corticosteroid such as methylprednisolone (40?mg) or triamcinolone (40?mg) should be considered. A total of three injections can be given at 1-month intervals. Topical and sub-Tenon’s injections are used concurrently.
Should no response or a poor response occur, systemic therapy with prednisone 40?mg orally once per day for 1 week can be considered. Discontinue by tapering the dose over 2–3 weeks. Ranitidine 150?mg should be given orally twice a day as long as the patient is receiving systemic corticosteroids. It should be noted that there is a high rate of recurrence of CME following cessation of corticosteroid therapy. Data obtained with the use of a single intravitreal injection of triamcinolone (4?mg/0.1?mL) also appear encouraging and may be considered for refractory cases.
Favorable responses have been documented with the use of COIs. Topical ketorolac four times per day for 2–3 weeks may be highly effective and can be used instead of, or in addition to, topical corticosteroids in the initial management of persistent CME.
Consider oral acetazolamide 500?mg/day as an adjunct to topical corticosteroids or topical COIs in the initial management of persistent CME.
propensity for this complication. Cataract induction varies with the potency and the length of application of the medication. Application of topical corticosteroids exacerbates external herpes simplex virus infections and compromises the immunological resistance to bacterial and fungal infections. Corneal melting can be enhanced by corticosteroid therapy due to inhibition of collagen synthesis. Of great importance is the fact that local therapy (including topical and periocular) has minimal systemic side effects but can perpetuate already existing adrenal suppression. 
Posterior sub-Tenon’s injections may have advantages over topical application. They exert a maximal, long-lasting response at the site of injection, and water-soluble drugs have excellent penetration through the sclera via periocular injection as opposed to topical application. Periocular injections carry the risk of inadvertent penetration of the globe. Contraindications for patients receiving posterior sub-Tenon’s injections include steroid-induced glaucoma, hypersensitivity to components of the injected steroid preparation, active necrotizing scleritis, and active ocular toxoplasmosis.
Intravitreal triamcinolone for the treatment of CME secondary to uveitis has been described. A single intravitreal injection of triamcinolone induced clinical and angiographic resolution of CME. The side effects of treatment were similar to those of periocular injection including IOP rise and increased rate of cataract formation.
Systemic corticosteroids used for CME are administered orally or intravenously.  Numerous potential side effects occur. Ocular complications include elevated IOP, posterior subcapsular cataract, increased incidence of viral ocular infections, ptosis, mydriasis, scleral melt, and lid skin atrophy. Potential short-term systemic effects include peptic ulcer disease, aseptic necrosis of the femoral head, and mental changes consisting of euphoria, insomnia, and psychosis. Long-term systemic side effects include osteoporosis, a cushingoid state, electrolyte imbalance, reactivation of latent infections such as tuberculosis, myopathy, suppression of the pituitary-adrenal axis, and increased severity of preexisting diabetes and hypertension. Patients should be observed by an internist and informed of all risks and complications associated with systemic corticosteroid use.
Cyclo-oxygenase is inhibited by COI drugs, which prevents the conversion of arachidonic acid into endoperoxides and, hence, inhibits PG synthesis. Clinically, COIs decrease capillary leakage.
Topical COIs (e.g., topical indomethacin 1% three times per day for 2 weeks to 9 months) are effective in achieving prophylaxis against CME.    However, these studies included concurrent corticosteroid treatment and no significant long-term benefit in vision was documented. A synergistic effect with corticosteroids may play a role in the improvement, particularly as corticosteroids inhibit the generation of PGs. It was shown by Flach et al. that treatment with topical ketorolac tromethamine (0.5%) with no concurrent corticosteroid treatment resulted in a reduction in postoperative angiographic CME but no significant difference in visual acuity. A later study using topical ketorolac tromethamine (0.5%) versus prednisolone versus combination therapy indicated improvement in vision with the use of combination therapy over monotherapy with either agent alone.
Complications associated with the use of topical anti-inflammatory agents include ocular irritation and discomfort following application, conjunctival injection, mild punctate keratopathy, and mydriasis. In addition, allergic and hypersensitivity reactions have been reported.
Topical COIs are used to treat symptomatic CME. Two studies indicate their efficacy in this situation. In a study in which 1% topical fenoprofen was used three times a day for 8 weeks, only two patients showed an improvement in vision and this improvement ceased with discontinuation of treatment but returned when treatment was reinstituted. A multicenter study conducted by Flach et al. demonstrated a statistically significant improvement in visual acuity of two Snellen lines in a group treated with a topical ketorolac 0.5% compared with a placebo-treated group. This improvement remained statistically significant 1 month following cessation of treatment.
Systemic absorption of COIs can occur following topical application. Whether this is clinically important is unknown. No study has shown that the use of these drugs topically before or after ocular surgery increases bleeding tendencies in ocular tissues. It is prudent to keep in mind the possibility of increased bleeding time.
Yannuzzi et al. studied a systemic COI (oral indomethacin 25?mg three times a day) for its effect on postoperative CME. No significant effect was noted on visual acuity or the presence of chronic CME.
Systemic COIs are associated with multiple side effects. Gastrointestinal side effects include nausea, vomiting, diarrhea, anorexia, abdominal discomfort, ulceration, and gastrointestinal bleeding. These agents can interfere with platelet function and clotting. Bone marrow suppression, hepatotoxicity, impaired renal function, and central nervous system symptomatology, including headache, dizziness, somnolence, depression, fatigue, insomnia, and confusion, have been reported. Hypersensitivity and induction of asthmatic attacks can occur. Indomethacin can be deposited in the cornea in a whorl-like pattern. Association with optic nerve dysfunction has been reported. Finally, dermatologic reactions include rash, dermatitis, and Stevens-Johnson syndrome can occur.
The availability of topical formulations that provide good ocular penetration of the drug make it unnecessary to recommend
TABLE 131-1 — SURGICAL TREATMENT OF CHRONIC APHAKIC AND PSEUDOPHAKIC CYSTOID MACULAR EDEMA
Intracameral lens (within the pupil; iris suspended).
Remove, consider exchange for flexible AC IOL, or suture-fixated PC IOL.
Anterior chamber IOL with distorted pupil and vitreous strands in AC.
Vitrectomy to restore normal pupil. Leave IOL if flexible, remove if not.
Would a sulcus-fixated PC IOL be safe? Omitting IOL is another option, as is a suture-fixated PC IOL.
AC IOL without distorted pupil or vitreous in AC.
Remove, especially if rigid IOL; replace with flexible IOL or would sulcus-fixated PC IOL be safe?
Omit IOL; use contact lens or place a suture-fixated PC IOL.
Elevated, isolated vitreous strand distorting pupil with AC or PC IOL.
Consider YAG vitreolysis.
PC IOL with pupillary capture.
PC IOL with moderate pupillary distortion from vitreous strands.
Anterior vitrectomy for restoring pupil to normal and consider leaving lens.
PC IOL, sulcus fixation, normal pupil.
Consider removing IOL; possibly exchange for flexible AC IOL, or leave IOLs out, or use a suture-fixated PC IOL.
PC IOL; “in-the-bag,” normal pupil.
Pars plana vitrectomy if evidence of traction on macula (rare). Rule out other causes of CME.
AC, Anterior chamber; PC, posterior chamber.
systemic therapy for ophthalmic indications, particularly in view of the many serious side effects of systemic administration.
Acetazolamide is a carbonic anhydrase inhibitor. It has been shown to facilitate the transport of water across the retinal pigment epithelium from the subretinal space to the choroids. A case report suggests a direct correlation of resolution of pseudophakic CME with acetazolamide therapy.
A study conducted by Cox et al.  demonstrated that 16 of 41 patients responded to acetazolamide treatment with partial or complete resolution of edema and improved vision. These patients had macular edema secondary to a host of other conditions, including the Irvine-Gass syndrome.
The complications and side effects of acetazolamide include paresthesias, which occur almost universally. Fatigue, depression, anorexia, weight loss, and loss of libido, as well as nausea, diarrhea, cramps, and gastric irritation, may occur. Hematologic complications consist of Stevens-Johnson syndrome and blood dyscrasias. Finally, renal stone formation is a well-known and potentially serious complication.
Improvement in aphakic CME with hyperbaric oxygen therapy was reported by Ploff and Thom. The dosage given was 2.2?atm (222.92?kPa) oxygen for 1.5?h twice a day for 7 days, followed by 2?h daily for 14 days. The mechanism was hypothesized to be macular capillary contraction.
Surgical management is directed toward reducing vitreomacular traction, which may play a role in the development of CME. However, it is not as important in the pathogenesis of this condition as is inflammation. Eyes that continue to have depressed central vision, photophobia, conjunctival injection, and discomfort almost always have vitreous strands adherent to the undersurface of the cataract wound, the iris, or the intraocular lens (IOL) implant. This may be accompanied by a peaked pupillary margin, which results from vitreous emerging from the posterior chamber to the cataract wound or from formed vitreous that has condensed on the anterior surface of the iris.
If medical management fails and evidence exists of vitreous adhesions to the cataract wound, consideration should be given to the application of the YAG laser to sever these connections. In cases of persistent and unremitting CME, consideration can also be given to performing a vitrectomy or removing the IOL. The vitrectomy should eliminate any vitreous in the anterior chamber. Anterior chamber lenses, in particular, may require removal if they appear to be associated with chronic uveitis. Table 131-1 summarizes the surgical treatment of chronic aphakic and pseudophakic CME present in a variety of situations.
COURSE AND OUTCOME
The majority of patients who have aphakic or pseudophakic CME attain vision of 20/30 (6/9) or better 3–12 months following surgery. In unrelenting cases, medical or surgical management may be indicated.
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