The pathogenesis and clinical presentation of macular edema in inflammatory diseases

Outcome of intravitreal triamcinolone acetonide in postoperative cystoid macular oedema

AIMS

To assess the efficacy and safety of intravitreal triamcinolone in the treatment of postoperative cystoid macular oedema (CMO).

METHODS

A retrospective case series review of 21 eyes (20 patients) that had an intravitreal injection of triamcinolone 4 mg for postoperative CMO. Diagnosis was confirmed by fundus fluorescein angiography and/or optical coherence tomography in all eyes.

RESULTS

Mean age of patients was 71.1 years. CMO had developed following routine phacoemulsification cataract extraction (13 eyes), phacoemulsification cataract extraction complicated by posterior capsule tear and vitreous loss (two eyes), vitrectomy (three eyes), or planned combined phacoemulsification and vitrectomy (three eyes). Mean duration of CMO before triamcinolone injection was 4.9 months. Mean duration of follow-up was 7.4 months. Two eyes required a repeat injection. Mean logarithm of minimum angle of resolution (LogMAR) visual acuity (VA) before treatment was 0.53; at 1 month post injection, this increased significantly to 0.33 (P<0.001). Improvement in VA was maintained throughout follow-up; at 6 months or later, mean LogMAR VA was significantly better than baseline (0.33 vs 0.53, P=0.02). At the latest review, 43% of eyes had improved Snellen VA by two or more lines and 86% by one or more lines compared to baseline. The remaining 14% had reduced Snellen VA compared to baseline. In the post-injection period, 33% of eyes developed an intraocular pressure of 22 mm Hg or higher and all responded well to short-term topical agents. There were no other post-injection complications.

CONCLUSION

Intravitreal triamcinolone results in a rapid improvement in VA that may be sustained for more than 6 months.

Prospective optical coherence tomographic evaluation of the efficacy of oral and posterior subtenon corticosteroids in patients with intermediate uveitis

PURPOSE

To prospectively evaluate the efficacy of oral corticosteroids and posterior subtenon injection in the treatment of macular edema in patients with intermediate uveitis using optical coherence tomography (OCT).

METHODS

Twenty-two patients with intermediate uveitis were treated with posterior subtenon injection when the disease was unilateral (group A, n=11) or with oral steroids when the disease was bilateral (group B, n=11). Changes in macular thickness from baseline was determined using OCT in both groups at day 0, day 3, day 14, 6 weeks and 12 weeks.

RESULTS

Statistically significant improvement in Snellen visual acuity in group A was seen at 6 weeks and in group B at 2 weeks. In patients receiving oral corticosteroids, foveal thickness decreased by 63% by day 3. In those treated with posterior subtenon injection, even at day 14 only a 55% reduction of foveal thickness was evident. Spearman's correlation coefficient for visual acuity and foveal thickness was found to be significant.

CONCLUSION

OCT confirms a significantly more rapid decrease in macular edema in patients treated with oral corticosteroids. A short course of oral steroids may be useful in enabling earlier visual recovery in patients treated with posterior subtenon injection for unilateral uveitic macular edema.

HB-EGF: Increase in the ischemic rat retina and inhibition of osmotic glial cell swelling

We determined whether the expression of heparin-binding epidermal growth factor-like growth factor (HB-EGF) in the sensory rat retina alters during ischemia-reperfusion, and whether HB-EGF affects the osmotic swelling which is a characteristic feature of Müller glial cells after ischemia. Transient retinal ischemia was induced by elevation of the intraocular pressure for 1 h. Western blots revealed an upregulation of HB-EGF in the retina at 1, 3, and 7 days after reperfusion. HB-EGF inhibited the swelling of glial cells in retinal slices, via stimulation of the synaptic release of glutamate and subsequent activation of glial metabotropic glutamate receptors which resulted in an autocrine release of purinergic receptor agonists. Finally, activation of A1 receptors resulted in opening of glial K(+) and Cl(-) channels. It is suggested that the increased expression of HB-EGF and the inhibition of glial cell swelling may be parts of a protective role of HB-EGF in the ischemic retina.

Diabetes alters osmotic swelling characteristics and membrane conductance of glial cells in rat retina

The development of edema in the diabetic retina may be caused by vascular leakage and glial cell swelling. To determine whether diabetic retinopathy alters the swelling characteristics of retinal glial cells and changes the properties of the glial membrane K+ conductance, isolated retinas and glial cells of rats were investigated at 4 and 6 months of chemical diabetes. After 6 months of hyperglycemia, application of a hypotonic solution to retinal slices induced swelling of glial cell bodies, a response not observed in control retinas. The osmotic glial cell swelling was blocked by inhibitors of phospholipase A2 or cyclooxygenase and by a thiol-reducing agent. Glial cells from diabetic retinas displayed a decrease of K+ currents that was associated with an altered subcellular distribution of the K+ conductance and a loss of perivascular Kir4.1 protein. The observation that swelling of cells in control retinas was inducible with K+ channel-blocking Ba2+ ions suggests a relationship between decreased K+ inward currents and osmotic cell swelling in diabetic retinas. The data show that glial cells in diabetic retinas are more sensitive to osmotic stress, which is associated with a decrease of K+ currents, than cells in control retinas. It is suggested that these alterations may be implicated in the development of diabetic retinal edema.

The developmental expression of K+ channels in retinal glial cells is associated with a decrease of osmotic cell swelling

A major function of glial cells is the control of osmotic and ionic homeostasis, mediated by K+ and water movements predominantly through inwardly rectifying K+ (Kir) and aquaporin water channels. It has been suggested that K+ currents through Kir channels are implicated in the regulation of glial cell volume. Here, we investigated whether the developmental increase in Kir channel expression in Müller glial cells of the rat retina is associated with an alteration of cell volume regulation under anisoosmotic conditions. Around the time of eye opening at postnatal day (P) 15, developing retinal glial cells fully alter the profile of their membrane conductances, from a current pattern with prominent fast transient K+ and Na+ currents to a pattern of noninactivating currents through Kir and delayed rectifier K+ channels. Concomitantly, aquaporins-1 and -4 are expressed in the developing retina. This is accompanied by a conspicuous alteration of the swelling characteristics of cells; somata of immature glial cells in early postnatal retinas (P5-P15) swell under hypotonic stress but no swelling is inducible in mature cells at P18 and thereafter. However, glial cells at all developmental stages swell when their Kir channels are blocked by Ba2+. The postnatal maturation of Kir channel currents and volume regulation in retinal glial cells is delayed by visual deprivation. The data suggest that Kir channels are crucially involved in osmotic volume homeostasis of mature glial cells, and that the absence of Kir channels in immature cells is a major cause of their insufficient volume regulation.

Neuronal versus glial cell swelling in the ischaemic retina

Under normal conditions, the pigment epithelium dehydrates the outer retina while Müller glial cells mediate the rapid water transport within the inner retina. Gliotic alterations of Müller cells may be implicated in the development of oedema in the post-ischaemic retina. Here, we suggest a mechanism of Müller cell-supported neuronal cell swelling and apoptosis in the ischaemic retina. During ischaemia, over-excitation of ionotropic glutamate receptors leads to neuronal cell depolarization that causes excess Ca(2+) influx into the cells, and to activation of the apoptosis machinery. The ion fluxes into the retinal neurons are associated with water movements that are mediated by aquaporin-4 water channels expressed by Müller cells and result in neuronal cell swelling. After reperfusion, the glial cells may swell due to the down-regulation of their K(+) conductance, which results in intracellular K(+) overload and water movements from the blood and vitreous into the cells. An inhibition of the glial cell-mediated water movements during ischaemic episodes should reduce the ion shifts at the neuronal synapses, resulting in decreased neuronal cell swelling and apoptosis. An inhibition of the water movements in the post-ischaemic phase may prevent cytotoxic Müller cell swelling but may impair the fluid clearance from retinal tissue in the presence of vasogenic oedema. Thus, pharmacological modification of the ion and fluid clearance functions of Müller cells may become a novel way to resolve both cytotoxic and vasogenic oedema in the retina.

The Glucocorticoid Triamcinolone Acetonide Inhibits Osmotic Swelling of Retinal Glial Cells via Stimulation of Endogenous Adenosine Signaling

The glucocorticoid triamcinolone acetonide is clinically used for the treatment of macular edema. However, the edema-resolving mechanisms of triamcinolone are incompletely understood. Since cell swelling is a central cause of cytotoxic edema in the brain and retina, we determined the effects of triamcinolone acetonide on the swelling of retinal ganglion and Müller glial cells in acutely isolated retinas from rats and guinea pigs in situ. Triamcinolone acetonide (100 microM) had no effect on the swelling of ganglion cells that was evoked in isolated whole mounts of the guinea pig retina by acute application of glutamate (1 mM) or high K+ (50 mM). However, triamcinolone reversed the osmotic swelling of Müller glial cells in retinas of the rat that was observed under various experimental conditions: in retinas isolated at 3 days after transient retinal ischemia, in retinas of eyes with lipopolysaccharide-induced ocular inflammation, and in control retinas in the presence of Ba2+ (1 mM), H2O2 (200 microM), arachidonic acid (10 microM), or prostaglandin E2 (30 nM). The inhibiting effect of triamcinolone on osmotic glial cell swelling was mediated by stimulation of transporter-mediated release of endogenous adenosine and subsequent A1 receptor activation, resulting in an elevation of the intracellular cAMP level and activation of the protein kinase A, and, finally, in an opening of extrusion pathways for K+ and Cl- ions. The inhibitory effect on the cytotoxic swelling of glial cells may contribute to the fast edema-resolving effect of vitreal triamcinolone observed in human patients.

Zystoides Makulaödem bei Uveitis

Cystoid macular edema (CME) is the most frequent cause of visual deterioration in uveitis patients. Intraocular inflammation disturbs the blood-retina barrier and leads to retinal edema. The basis of successful treatment is the anti-inflammatory and immunosuppressive therapy of uveitis. Restoration of the blood-retina barrier is mediated by corticosteroids and nonsteroidal anti-inflammatory agents. Resorption of extracellular fluid is improved by systemic carboanhydrase inhibitors. Despite aggressive therapy loss of visual acuity is frequent. Therefore, early diagnosis of CME and initiation of treatment, even if visual acuity is not yet impeded, is mandatory.

Ocular inflammation alters swelling and membrane characteristics of rat Müller glial cells

Ocular inflammation is a common cause of retinal edema that may involve swelling of Müller glial cells. In order to investigate whether endotoxin-induced ocular inflammation in rats alters the swelling and membrane characteristics of Müller cells, lipopolysaccharide (LPS; 0.5%) was intravitreally injected. At 3 and 7 days after treatment, hypotonic challenge induced swelling of Müller cell somata that was not observed in non-treated control eyes. Müller cells of LPS-treated eyes displayed a downregulation of inward K(+) currents and upregulation of A-type K(+) currents that was associated with a decreased expression of Kir4.1 protein in retinal slices. The data suggest that ocular inflammation induces alterations of both the swelling characteristics and the K(+) channel expression of Müller cells.

Makulaforamen

The theory of macular hole pathogenesis, which had so far been based on biomicroscopy, has been considerably altered by optical coherence tomography. The precise presentation of vitreofoveal pathology shows that forces acting in different directions are associated with different stages of the disease, making surgical treatment adapted to the different stages possible. Some surgical procedures are still controversial, and there is still no gold standard in macular hole surgery. Especially no agreement exists on the benefit of internal limiting membrane peeling, possibly assisted by staining with indocyanine green. Also details of endotamponade and postoperative positioning are controversial. Therefore, the method of surgical treatment depends a lot on the individual surgeon. This review summarizes the broad spectrum of the literature and the present knowledge in this field.

Intravitreal triamcinolone for macular oedema: efficacy in relation to aetiology

PURPOSE

To evaluate the efficacy and safety of intravitreal triamcinolone in patients with macular oedema of varying aetiology.

METHODS

Two milligrams of intravitreal triamcinolone acetonide was injected into 34 eyes with persistent macular oedema (17 eyes with macula oedema secondary to posterior uveitis, 13 eyes with diabetic retinopathy, and four with pseudophakic macular oedema). Best corrected visual acuity was determined and transfoveal optical coherence tomography performed after 1 week, 1 month, 3 months and 6 months.

RESULTS

Treatment improved visual acuity and subjective visual quality, and reduced foveal thickness in eyes with posterior uveitis and eyes with macular oedema secondary to diabetic retinopathy. Eyes treated for pseudophakic cystoid macular oedema demonstrated no improvement. A total of 32% of patients experienced a significant post-injection increase in intraocular pressure. Endophthalmitis, rhegmatogenous retinal detachment and cataract were absent.

CONCLUSION

Intravitreal triamcinolone appears to induce marked a improvement in macular oedema secondary to non-infectious uveitis and diabetic retinopathy.

Intraocular and plasma levels of cellular fibronectin in patients with uveitis and diabetes mellitus

AIMS

To determine intraocular and plasma levels of cellular fibronectin (cFN) in patients with uveitis or diabetes mellitus (DM) and to assess the association with disease activity, macular oedema, and vascular leakage on fluorescein angiography. In addition, to examine whether cFN is locally produced in the eye.

METHODS

Intraocular and plasma levels of cFN were determined by ELISA in 39 patients with uveitis (23 active, 16 non-active), in 11 patients with DM (eight with and three without diabetic retinopathy) and in 17 control patients. The influence of diabetic retinopathy, inflammatory activity, vascular leakage, and macular oedema (MO) on intraocular and plasma cFN levels was studied. Local production of cFN was determined by calculating absolute and relative intraocular to plasma ratios. Aqueous and vitreous levels of cFN were compared.

RESULTS

No differences in plasma cFN levels were found between patients with uveitis, DM, or controls. Intraocular cFN levels were significantly raised in patients with uveitis and DM, specifically in those with active disease (active uveitis and active diabetic retinopathy versus controls: p = 0.001 and 0.002 respectively). Further, intraocular cFN levels were significantly elevated in patients with macular oedema or vascular leakage, irrespectively of whether associated with uveitis or DM (p = 0.001 and 0.002). Intraocular cFN levels were consistently higher in the vitreous than the aqueous. Intraocular production of cFN was documented by elevated absolute and relative intraocular to plasma ratios in nine out of 11 patients tested.

CONCLUSIONS

Elevated intraocular cFN levels were found in uveitis and DM, especially in those with active processes, intraocular vascular damage, and MO. These results suggest that locally produced cFN levels reflect intraocular vascular damage.

Control of myeloid activity during retinal inflammation

Combating myeloid cell-mediated destruction of the retina during inflammation or neurodegeneration is dependent on the integrity of homeostatic mechanisms within the tissue that may suppress T cell activation and their subsequent cytokine responses, modulate infiltrating macrophage activation, and facilitate healthy tissue repair. Success is dependent on response of the resident myeloid-cell populations [microglia (MG)] to activation signals, commonly cytokines, and the control of infiltrating macrophage activation during inflammation, both of which appear highly programmed in normal and inflamed retina. The evidence that tissue CD200 constitutively provides down-regulatory signals to myeloid-derived cells via cognate CD200-CD200 receptor (R) interaction supports inherent tissue control of myeloid cell activation. In the retina, there is extensive neuronal and endothelial expression of CD200. Retinal MG in CD200 knockout mice display normal morphology but unlike the wild-type mice, are present in increased numbers and express nitric oxide synthase 2, a macrophage activation marker, inferring that loss of CD200 or absent CD200R ligation results in "classical" activation of myeloid cells. Thus, when mice lack CD200, they show increased susceptibility to and accelerated onset of tissue-specific autoimmunity.

Cystoid macular edema in uveitis

Cystoid macular edema (CME) can cause profound visual loss and is one of the major causes of legal blindness in patients with uveitis. It can complicate virtually any type of acute or chronic, anterior or posterior uveitis. When mild and of short duration, CME may respond to treatment used to control the intraocular inflammation. However, patients may need more aggressive treatment with local and systemic steroid therapy and other immunosuppressive drugs. Unfortunately, CME may become refractory to all currently available therapies and result in severe visual loss.

Intravitreal triamcinolone acetonide for refractory chronic pseudophakic cystoid macular edema

PURPOSE

To determine the safety and efficacy of intravitreal triamcinolone acetonide (TAAC) injections in patients with refractory cystoid macular edema (CME) after cataract extraction.

SETTING

LSU Eye Center, Louisiana State University Health Sciences Center, New Orleans, Louisiana, USA.

METHODS

In this nonrandomized retrospective case review, 8 eyes of 8 patients with a history of pseudophakic CME recalcitrant to current standard treatment modalities were enrolled. The mean duration of the CME was 20 months. The patients received intravitreal injections of 1 mg of TAAC and were followed for a mean of 8 months. The main outcome measures included visual acuity, the presence of CME on biomicroscopic examination, angiographic evidence of perifoveal leakage, intraocular pressure (IOP), and complications related to treatment.

RESULTS

The visual acuity increased in all patients. The magnitude of improvement was mainly restricted by underlying macular pathology and correlated well with the level of visual acuity at entry into the study. Angiographic improvement occurred in all patients. Temporary increases in IOP were easily controlled with topical medications. No other adverse effects could be attributed to this technique. Repeated injections were required.

CONCLUSIONS

Intravitreal administration of TAAC was safe and effective in recalcitrant cases of pseudophakic CME with a beneficial effect on the macular edema and visual acuity. A prospective randomized study is needed to determine with accuracy the efficacy, safety, and exact timing of this technique and possibly to recognize subtypes with a more favorable response. Repeated injections were required in all eyes. The development of a sustained-release intravitreal drug-delivery system would be beneficial.

Experimental macular edema induced by macular venule occlusion in monkey

PURPOSE

Visual prognosis after retinal vein occlusion varies, because it may be affected by macular edema or an avascular area. The mechanism describing how macular edema and avascular areas occur, however, has not been clearly understood. We induced macular edema in cynomolgus monkeys by occluding macular venules to evaluate the retinal microcirculation.

METHODS

We produced venous occlusion by applying dye laser in three cynomolgus monkeys. Macular edema was examined by slit lamp biomicroscopy and optical coherence tomography. Acridine orange leukocyte fluorography (AOLF) and fluorescein angiography were performed to study blood flow and vascular leakage before and after laser application.

RESULTS

We observed three types of retinal changes in the macular area: (1) macular edema did not develop; (2) macular edema developed, but improved with avascular area formation; (3) macular edema developed, but disappeared without avascular area formation. Under physiological conditions, observation revealed that leukocytes flowed from arterioles into either superior or inferior venules. When macular edema did not develop, most leukocytes from arterioles escaped into the adjacent non-occluded venules. In contrast, when macular edema occurred, leukocyte flow became stagnated. Macular edema developed when capillary leakage was observed from venules and subsequently arterioles, but disappeared when an avascular area was formed by arteriole occlusion.

CONCLUSIONS

We demonstrated that experimental macular edema could be induced by macular venule occlusion in monkeys. According to our observation by AOLF, whether macular edema is induced or not depends on the function of collateral routes of the remaining non-occluded venules. We could consider that a gradual increase in intravascular pressure was associated with the avascular area formation.

Cystoid macular edema associated with topical latanoprost in glaucomatous eyes with a normally functioning blood-ocular barrier

PURPOSE

To study prospectively using optical coherence tomography (OCT) whether topical latanoprost induces retinal disorders, such as cystoid macular edema, in patients with glaucoma and a normally functioning blood-ocular barrier.

METHODS

Sixty-eight eyes of 38 patients with glaucoma and no history of intraocular surgery, uveitis, or laser trabeculoplasty were studied. Before initiation of latanoprost treatment and after 1, 3, and 6 months of treatment, OCT images were taken, and the following tests were performed: visual acuity examination, fundus ophthalmoscopy, intraocular pressure measurement, and fundus color photography. To evaluate retinal thickness in the fovea accurately. OCT scanning was repeated six times, and the smallest value was used as the retinal thickness in the fovea.

RESULTS

Latanoprost ophthalmic solution did not influence retinal thickness in the fovea at any investigated time points compared with the time before instillation, and no changes were observed in visual acuity, ophthalmoscopic findings, and fundus photographs. The intraocular pressure was reduced significantly at all investigated time points compared with the time before instillation.

CONCLUSIONS

It is unlikely that topical latanoprost induces retinal disorders, such as cystoid macular edema, in glaucomatous eyes with a normally functioning blood-ocular barrier.