Diseases of the retina

Initial Evidences of Salt and Pepper Retinal Lesions (SPRL) in Patients with Intestinal Protozoan Infections in Iran

BACKGROUND

It is made clear that salt and pepper retinal lesion (SPRL) has subsequently associated with the infection with Giardia lamblia (G. lamblia). However, little is known regarding the prevalence of SPRL among patients suffered from parasitic infections in the world.

OBJECTIVE

This study aimed to determine the prevalence of SPRL among patients with intestinal protozoan infections, for the first time, in Sari, northern Iran.

METHODS

In this case-control study, a total of 150 subjects participated: 75 were in the patients group diagnosed to have an intestinal parasite and 75 in the control group without any intestinal infection. Fecal samples were obtained from all participants and examined with wet mount and formalin-ether methods. The retina of both groups was examined by an ophthalmologist.

RESULTS

Overall, salt and pepper retinal changes were diagnosed in 12 (16 %) patients with at least one parasitic infection (7 females and 5 males). G. lamblia was diagnosed in 6 subjects (50%), Blastocystis hominis in 5 (41.6%), and Entamoeba coli in 1 (8.3 %). Most of the patients (58.3%) had a mild infection. Bilateral retinal involvement was observed in 75% of the patients. Furthermore, macula involvement was observed in 91.7 % with SPRL.

CONCLUSION

Our findings indicated the relatively high prevalence of SPRL in subjects with giardiasis and blastocystosis. It can be concluded that not only G. lamblia but also B. hominis can cause SPRL in Sari, Iran. Further studies are needed to find other etiologic parasites able to cause retinal damages.

Carbamazepine Alleviates Retinal and Optic Nerve Neural Degeneration in Diabetic Mice via Nerve Growth Factor-Induced PI3K/Akt/mTOR Activation

Aim: Diabetic retinopathy causes loss of vision in adults at working-age. Few therapeutic options are available for treatment of diabetic retinopathy. Carbamazepine (CARB), a widely used antiepileptic drug, was recently accounted for its neuroprotective effect. Nerve growth factor (NGF) activates various cascades among which, PI3K/Akt/mTOR pathway has a vital action in NGF-mediated neuronal differentiation and survival. This study evaluated the effect of CARB in the treatment of diabetic retina and unveiled some of the underlying molecular mechanisms. Main Methods: Alloxan diabetes model was induced in 36 albino well-acclimatized mice. After establishment of the diabetic model in 9 weeks, mice were assigned to treatment groups: (1) saline, (2) alloxan-diabetic, (3 and 4) alloxan+CARB (25 or 50 mg per kg p.o) for 4 weeks. After completion of the therapeutic period, mice were sacrificed and eyeballs were enucleated. Retinal levels of NGF and PI3K/Akt were assessed using real-time polymerase chain reaction. Further, total and phosphorylated TrKA, PI3K, Akt, mTOR as well as Caspase-3 were measured by Western blot analysis. Key Findings: Histopathological examination demonstrated that CARB attenuated vacuolization and restored normal thickness and organization of retinal cell layers. In addition, CARB increased pTrKA/TrKA ratio and ameliorated diabetes-induced reduction of NGF mRNA and immunostaining in retina. Additionally, it augmented the mRNA expression of PI3K and Akt, as well as the protein level of the phosphorylated PI3/Akt/mTOR. Significance: Results highlighted, for the first time, the neuronal protective effect for CARB in diabetic retina, which is mediated, at least in part, by activation of the NGF/PI3K/Akt/mTOR pathway.

Combination of ranibizumab and indomethacin for neovascular age-related macular degeneration: randomized controlled trial

Purpose

The aim of this study was to evaluate whether indomethacin eye drops and intravitreal ranibizumab (IVR) injections would provide additional benefit over ranibizumab alone in the treatment of choroidal neovascularization (CNV).

Participants and methods

This was a randomized, prospective pilot study of eyes with new-onset CNV. Fifty-eight patients were randomized 1:1 into a ranibizumab monotherapy (RM) group and a ranibizumab plus indomethacin (RI) group. All patients received monthly 0.5 mg IVR injections for 3 months, followed by monthly injections administered as needed. RI group patients also self-administered one drop of 0.5% indomethacin three times a day for 12 months. All patients were followed up for 12 months.

Results

At 12 months, both groups showed significant improvement in best-corrected visual acuity (BCVA) and central retinal thickness (CRT). The mean BCVA change from baseline to 12 months was -0.12±0.04 LogMAR and -0.20±0.04 LogMAR in the RM and RI groups, respectively, with the degree of change being significantly different between the two groups (P=0.04). At 12 months, the mean CRT in the RM group (316±41.2 µm) was significantly higher than that in the RI group (287±31.5 µm; P=0.004). The mean required number of IVR injections was 7.38±0.78 and 6.34±0.67 in the RM and RI groups, respectively (P<0.001).

Conclusion

Compared to IVR monotherapy, combination therapy with indomethacin eye drops and IVR provides superior anatomical and visual outcomes in patients with naive CNV lesions. Moreover, topical indomethacin might reduce the frequency of IVR injections, which is very beneficial considering the chronic and expensive nature of IVR therapy.

Topical nonsteroidal anti-inflammatory drugs for macular edema

Nonsteroidal anti-inflammatory drugs (NSAIDs) are nowadays widely used in ophthalmology to reduce eye inflammation, pain, and cystoid macular edema associated with cataract surgery. Recently, new topical NSAIDs have been approved for topical ophthalmic use, allowing for greater drug penetration into the vitreous. Hence, new therapeutic effects can be achieved, such as reduction of exudation secondary to age-related macular degeneration or diabetic maculopathy. We provide an updated review on the clinical use of NSAIDs for retinal diseases, with a focus on the potential future applications.

Red blood cell count as an indicator of microvascular complications in Chinese patients with type 2 diabetes mellitus

BACKGROUND

Rheological disorders of red blood cells (RBC) and decreased RBC deformability have been involved in the development of diabetic microangiopathy. However, few studies have evaluated the association of RBC count with microvascular complications in patients with type 2 diabetes mellitus (T2DM). The purpose of this study was to investigate the association of RBC count with microvascular complications in patients with T2DM.

METHODS

This study involved 369 patients with T2DM: 243 with one or more microvascular complications and 126 without microvascular complications. Anticoagulated blood was collected and analyzed in an automated blood cell counter. The presence of risk factors for microvascular complications was determined.

RESULTS

The proportion of patients with microvascular complications increased as the RBC count decreased (P < 0.001). After adjustment for known risk factors for microvascular complications by logistic regression analysis, lower quartiles of RBC count were associated with a higher risk of microvascular complications compared with the reference group composed of the highest quartile (first quartile, odds ratio 4.98, 95% confidence interval 1.54-6.19, P = 0.008; second quartile, odds ratio 3.21, 95% confidence interval 1.17-5.28, P = 0.024).

CONCLUSION

A decreased RBC count is associated with microvascular complications in Chinese patients with T2DM. The RBC count is a potential marker to improve further the ability to identify diabetic patients at high risk of microvascular complications.

An update on the pharmacotherapy of neovascular age-related macular degeneration

INTRODUCTION

Neovascular age-related macular degeneration (AMD) is currently the most common cause of legal blindness in industrialized countries. The advent of pharmacotherapy with intravitreal VEGF inhibitors has greatly improved outcomes for the treatment of this disease.

AREAS COVERED

The present review is divided into two major sections: the period prior to the use of anti-VEGF agents (triamcinolone acetonide, verteporfin photodynamic therapy) and the period following their introduction (pegaptanib sodium, bevacizumab, ranibizumab, aflibercept). The main pharmacological and clinical characteristics of each therapy are summarized.

EXPERT OPINION

Monotherapy with anti-VEGF agents is currently the 'gold standard' for treating neovascular AMD, but, with several drug choices and various different dosing regimens available, there is still wide variability in how individual clinicians manage their patients. Despite improved visual outcomes, there remains a significant unmet need for better treatments as the frequent office visits and injections associated with anti-VEGF therapy are costly and place a significant burden on patients, their family members and physicians.

Towards an ideal biomaterial for vitreous replacement: Historical overview and future trends

Removal of the natural vitreous body from the eye and its substitution with a tamponade agent may be necessary in cases of complicated retinal detachment. Many materials have been variously proposed and tested over the years in an attempt to find an ideal vitreous substitute. This review highlights the evolution of research in the field of vitreous replacement and chronicles the main advances that have been made in such a context. The suitability and limitations of vitreous tamponade agents and substitutes in current clinical use are examined, and the future promise of experimentally tested biomaterials are described and discussed. Future trends in research are also considered and, specifically, the great potential of polymeric hydrogels is emphasized, as they seem to be very effective in closely mimicking the features of the natural vitreous and they could successfully act as long-term vitreous substitutes without inducing clinical complications in the patient's eye.

Dietary hyperglycemia, glycemic index and metabolic retinal diseases

The glycemic index (GI) indicates how fast blood glucose is raised after consuming a carbohydrate-containing food. Human metabolic studies indicate that GI is related to patho-physiological responses after meals. Compared with a low-GI meal, a high-GI meal is characterized with hyperglycemia during the early postprandial stage (0-2h) and a compensatory hyperlipidemia associated with counter-regulatory hormone responses during late postprandial stage (4-6h). Over the past three decades, several human health disorders have been related to GI. The strongest relationship suggests that consuming low-GI foods prevents diabetic complications. Diabetic retinopathy (DR) is a complication of diabetes. In this aspect, GI appears to be useful as a practical guideline to help diabetic people choose foods. Abundant epidemiological evidence also indicates positive associations between GI and risk for type 2 diabetes, cardiovascular disease, and more recently, age-related macular degeneration (AMD) in people without diabetes. Although data from randomized controlled intervention trials are scanty, these observations are strongly supported by evolving molecular mechanisms which explain the pathogenesis of hyperglycemia. This wide range of evidence implies that dietary hyperglycemia is etiologically related to human aging and diseases, including DR and AMD. In this context, these diseases can be considered as metabolic retinal diseases. Molecular theories that explain hyperglycemic pathogenesis involve a mitochondria-associated pathway and four glycolysis-associated pathways, including advanced glycation end products formation, protein kinase C activation, polyol pathway, and hexosamine pathway. While the four glycolysis-associated pathways appear to be universal for both normoxic and hypoxic conditions, the mitochondria-associated mechanism appears to be most relevant to the hyperglycemic, normoxic pathogenesis. For diseases that affect tissues with highly active metabolism and that frequently face challenge from low oxygen tension, such as retina in which metabolism is determined by both glucose and oxygen homeostases, these theories appear to be insufficient. Several lines of evidence indicate that the retina is particularly vulnerable when hypoxia coincides with hyperglycemia. We propose a novel hyperglycemic, hypoxia-inducible factor (HIF) pathway, to complement the current theories regarding hyperglycemic pathogenesis. HIF is a transcription complex that responds to decrease oxygen in the cellular environment. In addition to playing a significant role in the regulation of glucose metabolism, under hyperglycemia HIF has been shown to increase the expression of HIF-inducible genes, such as vascular endothelial growth factor (VEGF) leading to angiogenesis. To this extent, we suggest that HIF can also be described as a hyperglycemia-inducible factor. In summary, while management of dietary GI appears to be an effective intervention for the prevention of metabolic diseases, specifically AMD and DR, more interventional data is needed to evaluate the efficacy of GI management. There is an urgent need to develop reliable biomarkers of exposure, surrogate endpoints, as well as susceptibility for GI. These insights would also be helpful in deciphering the detailed hyperglycemia-related biochemical mechanisms for the development of new therapeutic agents.

Intravitreal bevacizumab for subfoveal choroidal neovascularization in age-related macular degeneration at twenty-four months: the Pan-American Collaborative Retina Study

PURPOSE

To report the 24-month anatomic and Early Treatment Diabetic Retinopathy Study (ETDRS) best-corrected visual acuity (BCVA) response after primary intravitreal bevacizumab (IVB) (Avastin; Genentech Inc., San Francisco, CA) (1.25 or 2.5 mg) in patients with subfoveal choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD).

DESIGN

Retrospective, multicenter, interventional, comparative case series.

PARTICIPANTS

We reviewed the clinical records of 180 consecutive patients (207 eyes) with subfoveal CNV secondary to AMD at 9 centers from 8 countries.

METHODS

Patients were treated with at least 1 injection of IVB 1.25 mg (124 eyes [59.9%]) or 2.5 mg (83 eyes [40.1%]). Patients underwent ETDRS BCVA testing, ophthalmoscopic examination, optical coherence tomography (OCT), and fluorescein angiography (FA) at baseline and 1-, 3-, 6-, 12-, and 24-month visits.

MAIN OUTCOME MEASURES

Changes in BCVA and OCT.

RESULTS

The mean age of our patients was 74.3±7.5 years. The mean number of IVB injections per eye was 5.1 (range, 1-24 injections). In the 1.25 mg group, baseline BCVA improved from 20/235 (logarithm of the minimum angle of resolution [logMAR] 1.07) to 20/172 (logMAR 0.92) at 24 months (P<0.0001). Similar BCVA changes were observed in the 2.5 mg group. At baseline, the mean central macular thickness (CMT) by OCT in the 1.25 mg group was 308.4±127.52 μm, which was reduced to 269.35±97.92 μm, 262.1±94.81 μm, 264.03±97.06 μm, 245.91±89.52 μm, and 249.27±89.14 μm at 1, 3, 6, 12, and 24 months, respectively (P<0.0001). Similar changes were observed in the 2.5 mg group. In the 2.5 mg group, systemic complications included 2 new cases (2.6%) of arterial hypertension, 1 case (1.3%) of stroke, and 1 case (1.3%) of death.

CONCLUSIONS

Primary IVB at a dose of 1.25 or 2.5 mg seems to provide stability or improvement in BCVA, OCT, and FA in subfoveal CNV secondary to AMD at 24 months. Our results show no significant difference regarding BCVA with IVB at doses of 1.25 or 2.5 mg.

The Clinical Application of Ozonetherapy

The reader may be eager to examine in which diseases ozonetherapy can be proficiently used and she/he will be amazed by the versatility of this complementary approach (Table 9 1). The fact that the medical applications are numerous exposes the ozonetherapist to medical derision because superficial observers or sarcastic sceptics consider ozonetherapy as the modern panacea. This seems so because ozone, like oxygen, is a molecule able to act simultaneously on several blood components with different functions but, as we shall discuss, ozonetherapy is not a panacea. The ozone messengers ROS and LOPs can act either locally or systemically in practically all cells of an organism. In contrast to the dogma that “ozone is always toxic”, three decades of clinical experience, although mostly acquired in private clinics in millions of patients, have shown that ozone can act as a disinfectant, an oxygen donor, an immunomodulator, a paradoxical inducer of antioxidant enzymes, a metabolic enhancer, an inducer of endothelial nitric oxide synthase and possibly an activator of stem cells with consequent neovascularization and tissue reconstruction.

Primary intravitreal bevacizumab for subfoveal choroidal neovascularization in age-related macular degeneration: results of the Pan-American Collaborative Retina Study Group at 12 months follow-up

PURPOSE

To report the 12-month anatomic and Early Treatment Diabetic Retinopathy Study best-corrected visual acuity (BCVA) response after primary intravitreal bevacizumab (Avastin, Genentech Inc., San Francisco, CA) (1.25 mg or 2.5 mg) in patients with subfoveal choroidal neovascularization secondary to age-related macular degeneration.

METHODS

Sixty-three eyes of 63 consecutive patients with subfoveal choroidal neovascularization secondary to age-related macular degeneration, a mean age of 73.7 +/- 7.5 years and a minimum of 12 months (mean 55.5 +/- 6.2 weeks) of follow-up participated in this interventional retrospective multicenter case series in 7 centers from 6 countries. Patients were treated with at least 1 intravitreal injection of 1.25 mg or 2.5 mg of bevacizumab. Patients underwent Early Treatment Diabetic Retinopathy Study BCVA testing, ophthalmoscopic examination, optical coherence tomography, and fluorescein angiography at baseline and follow-up visits. Repeated measures analysis of variance was used to compare mean values.

RESULTS

The mean number of intravitreal bevacizumab injections per eye was 3.5 (range, 1-8). Mean baseline BCVA was 20/320, logarithm of the minimum angle of resolution = 1.2, and mean final BCVA was 20/200, logarithm of the minimum angle of resolution = 1.0 (P < 0.001). Central macular thickness at baseline by optical coherence tomography had a mean of 389.2 +/- 149.6 microm which was significantly reduced to a mean of 281.0 +/- 96.1 microm, 268.2 +/- 82.6 microm, 262.6 +/- 92.3 microm, and 241.3 +/- 76.7 microm at 1, 3, 6, and 12 months after initial treatment, respectively (P < 0.0001). Ocular adverse events included transient increased intraocular pressure in 2 (3.1%) eyes, endophthalmitis in 2 (3.1%) eyes, and transient hypotony in 1 eye (1.1%). No systemic adverse events were observed.

CONCLUSION

Primary intravitreal bevacizumab at doses of 1.25 mg or 2.5 mg seems to provide stability or improvement in BCVA, optical coherence tomography, and fluorescein angiography in subfoveal choroidal neovascularization secondary to age-related macular degeneration at 12 months.

Oxidative stress and diabetic retinopathy: pathophysiological mechanisms and treatment perspectives

Retinopathy is one of the most severe ocular complications of diabetes and is a leading cause of acquired blindness in young adults. The cellular components of the retina are highly coordinated but very susceptible to the hyperglycemic environment. The microvasculature of the retina responds to hyperglycemic milieu through a number of biochemical changes, including increased oxidative stress and polyol pathway, PKC activation and advanced glycation end product formation. Oxidative stress is considered as one of the crucial contributors in the pathogenesis of diabetic retinopathy, but oxidative stress appears to be highly interrelated with other biochemical imbalances that lead to structural and functional changes and accelerated loss of capillary cells in the retinal microvasculature and, ultimately, pathological evidence of the disease. One such potential connection that links oxidative stress to metabolic alterations is gyceraldehyde-3-phosphate dehydrogenase whose activity is impaired in diabetes, and that results in activation of other major pathways implicated in the pathogenesis of diabetic retinopathy. Alterations associated with oxidative stress offer many potential therapeutic targets making this an area of great interest to the development of safe and effective treatments for diabetic retinopathy. Animal models of diabetic retinopathy have shown beneficial effects of antioxidants on the development of retinopathy, but clinical trials (though very limited in numbers) have provided somewhat ambiguous results. Although antioxidants are being used for other chronic diseases, controlled clinical trials are warranted to investigate potential beneficial effects of antioxidants in the development of retinopathy in diabetic patients.

Effect of retinal permeability, diffusivity, and aqueous humor hydrodynamics on pharmacokinetics of drugs in the eye

AIM

Retinal permeability is one of the important parameters that determine drug distribution during diseased retinal conditions, whose effect is still unclear. Thus, the main aim of this study was to understand the influence of varying retinal permeability (P) on drug distribution under normal (F1) and elevated vitreous outflow pathophysiologic conditions (F10) for a wide variety of drug diffusivities-high: D(-5) and low: D(-7).

METHOD

A computational model of the rabbit eye was developed that took into account the varying effects of convection during normal and pathophysiologic conditions.

RESULTS

High retinal permeability, P(-5), is associated with low peak macular concentration and a rapid clearance from the ocular chambers, with the retina as the major route of elimination. For low permeability, P(-7), there is very high peak macular concentration, slow elimination, and a buildup of drug concentration, which depends on vitreous outflow. The variation of t(1/2) with P was found to be of linear and nonlinear trends for F1 and F10 flow cases, respectively. Moreover, for D(-5) diffusivity, there was a 1.5-fold increase and a 1.6-fold decrease in t(1/2) values when the retinal permeability values were P(-5) and P(-7). On the contrary, for D(-7) diffusivity, there was a 2.5-fold decrease and a 1.4-fold increase in t(1/2) values for P(-5) and P(-7), with t(1/2) increasing for P(-6) during both high and low diffusivities.

CONCLUSIONS

Thus, the combined effect of variables P, D, and F are important factors that should be considered in order to determine drug dosage. This study could be used to estimate the drug distribution and elimination for (1) wide range of physicochemical properties of drugs and (2) normal and abnormally elevated vitreous flows during the diseased condition of the eye. These results could help in obtaining essential information about the treatment protocol for targeted retinal diseases while simultaneously avoiding the toxic effects of these drugs.

Pharmacokinetics and retinal distribution of ranibizumab, a humanized antibody fragment directed against VEGF-A, following intravitreal administration in rabbits

PURPOSE

Ranibizumab (Lucentis) is a humanized antigen-binding fragment designed to inhibit all isoforms and active degradation products of vascular endothelial growth factor A (VEGF-A); it is in clinical development for the treatment of neovascular age-related macular degeneration (AMD). This study evaluated its pharmacokinetics (PK) and retinal distribution in rabbits when administered intravitreally (ITV).

METHODS

A total of 27 New Zealand white rabbits received a single bilateral ITV injection of ranibizumab 625 muicrog/eye (Group 1, n = 24) or I-labeled ranibizumab 625 microg/eye, 22.5 microCi/eye (Group 2, n = 3). Ranibizumab concentration was determined in the vitreous, aqueous humor, and serum up to 60 days postdose by enzyme-linked immunosorbent assay in Group 1. Group 2 eyes were microautoradiographed on days 1-4.

RESULTS

Ranibizumab has a terminal half-life of 2.9 days in the ocular compartments. Systemic exposure was low, measuring less than 0.01% of vitreous exposure when comparing AUC0-t values. Microautoradiography analysis demonstrated that ranibizumab penetrated all retinal layers, reaching the choriocapillaris on days 1, 2, and 4.

CONCLUSIONS

This study demonstrates that following ITV injection, ranibizumab has a vitreous half-life of 2.9 days with minimal systemic exposure. Ranibizumab rapidly penetrates through the retina to reach the choroid, supporting its clinical development for neovascular AMD.

Nefropatia e retinopatia em diabéticos do tipo 1 de um programa de atendimento multiprofissional universitário

O diabetes mellitus (DM) tipo 1 é associado a complicações crônicas micro e macrovasculares. Propusemo-nos a estudar a associação entre nefropatia (ND) e retinopatia diabéticas (RD), e destas com variáveis clínico-laboratoriais em portadores de DM tipo 1 acompanhados em um centro universitário. Realizou-se um estudo transversal através de análise de prontuários. Foram estudados 81 pacientes; a prevalência de RD foi 21,0% e de ND, 35,8%; houve associação entre ambas. Os portadores de ND e RD possuíam maior tempo de DM, maior prevalência de hipertensão, pior controle glicêmico e LDL colesterol mais elevado. A taxa de filtração glomerular (TFG) foi associada ao tempo de DM, hipertensão e albuminúria. Identificou-se menor TFG nos portadores de complicações microvasculares, principalmente naqueles com lesões avançadas. Concluímos que, em nosso estudo com portadores de DM tipo 1, houve associação entre RD, ND e TFG, sendo tempo de DM e hipertensão variáveis associadas de forma independente.

Acetylcholine neuroprotection against glutamate-induced excitotoxicity in adult pig retinal ganglion cells is partially mediated through alpha4 nAChRs

In the mammalian retina, excess glutamate release has been shown to be involved in retinal ganglion cell (RGC) death associated with various diseases. Recent studies have determined that activation of alpha7 nicotinic acetylcholine receptors (nAChRs) partially protect isolated RGCs from glutamate-induced excitotoxicity. In this study, we further classify the types of nAChRs involved in neuroprotection against glutamate-induced excitotoxicity using isolated adult pig RGCs. Cells were isolated with a modified two-step immunoselective panning technique designed to isolate RGCs from other retinal neurons. Once isolated, nAChR subunits were identified using a combination of pharmacological and immunocytochemical techniques. In cell culture experiments, a variety of alpha4 nAChR specific agonists were found to have a partial neuroprotective against glutamate-induced excitotoxicity. This neuroprotection was abolished in the presence of the alpha4 nAChR antagonist, dihydro-beta-erythroidine (DHbetaE). Immunocytochemical results localized several nAChR subunits on isolated adult pig RGCs; in particular alpha4, alpha7 and beta2 nAChR subunits. Large RGCs exclusively immunostained with antibodies against alpha7 nAChR subunits whereas alpha4 and beta2 subunits exclusively immunostained only small RGCs. Double label experiments provided evidence that alpha4 and beta2 subunits co-localize on small RGCs. Knowledge of the receptor subtypes responsible for neuroprotection may lead to treatments associated with glutamate-induced excitotoxicity.

Current and future pharmacological intervention for diabetic retinopathy

Diabetic retinopathy (DR) is a potentially visually devastating complication of chronic hyperglycaemia. Prospective, randomised clinical trials have delineated the standard prevention protocols, including intensive glycaemic, blood pressure, and lipid control, and laser photocoagulation treatment for neovascularisation and clinically significant macular oedema. However, despite these interventions, vision loss from DR still occurs at an alarming rate. Researchers have directed their efforts towards better understanding the specific biological and chemical changes occurring in DR to develop more targeted pharmacological prevention and treatment strategies. This review of diabetic retinopathy will primarily detail the therapies in development at present, including aldose reductase inhibitors, advanced glycosylation end product inhibitors, antioxidants, supplemental oxygen, growth factor modulators including vascular endothelial growth factor inhibitors and protein kinase C inhibitors, extracellular matrix modifiers including corticosteroids, and vitreous modulators. The experimental therapies alter several different pathways that lead to DR. Future research will further delineate these pathways, and therapy is likely to involve arresting several different promoters of DR.

[Diabetic retinopathy]

Diabetic retinopathy is a frequently observed complication in both type 1 and type 2 diabetes, specially in patients with long term disease and poor glicemic control. Irreversible visual loss appears at the final stages of diabetic retinopathy and it is considered one of the most tragic of diabetic complications. It is also considered an important factor of morbidity and has a high economical impact once it is the leading cause of blindness. The pathophysiology of the retinal microvascular alterations is related to the chronic hyperglycemia that leads to the following circulatory disturbances: loss of vascular tonus, increase in vascular permeability, edema and exudation, with vascular obstruction and ischemia that stimulates neovascularization, which may lead to fibrous retraction and vitreous hemorrhages with retinal detachment. Recent studies have indicated that the strict glicemic and blood pressure controls are effective in reducing or blocking the progression of retinopathy. Up to now no pharmacological agents have shown to be effective in preventing or reducing neovascularization and visual loss. Presently, the most effective available treatment for proliferative retinopathy is laser photocoagulation. Further studies are needed to obtain new products and technologies that could effectively prevent or block retinopathy progression.

Erytrocyte membrane anionic charge in type 2 diabetic patients with retinopathy

BACKGROUND

The Steno hypothesis states that changes in basement membrane anionic charge leads to diabetic microvascular complications. In diabetic nephropathy, loss of basement membrane glycosaminoglycans and the association between glomerular basement membrane heparan sulphate and proteinuria has been documented. A correlation between erythrocyte surface and the glomerular capillary wall charges has also been observed. The aim of this study is to evaluate the relationship between retinopathy and erythrocyte anionic charge and urinary glycosaminoglycan excretion in type 2 diabetic patients.

METHODS

49 subjects (58 +/- 7 yrs, M/F 27/22) with type 2 diabetes with proliferative retinopathy (n = 13), nonproliferative retinopathy (n = 13) and without retinopathy (n = 23) were included in the study. 38 healthy subjects were selected as control group (57 +/- 5 yrs, M/F 19/19). Erythrocyte anionic charge (EAC) was determined by the binding of the cationic dye, alcian blue. Urinary glycosaminoglycan and microalbumin excretion were measured.

RESULTS

EAC was significantly decreased in diabetic patients with retinopathy (255 +/- 30 ng alcian blue/10(6) RBC, 312 +/- 30 ng alcian blue/10(6) RBC for diabetic and control groups respectively, p < 0.001). We did not observe an association between urinary GAG and microalbumin excretion and diabetic retinopathy. EAC is found to be negatively correlated with microalbuminuria in all groups.

CONCLUSIONS

We conclude that type 2 diabetic patients with low erythrocyte anionic charge are associated with diabetic retinopathy. Reduction of negative charge of basement membranes may indicate general changes in microvasculature rather than retinopathy. More prospective and large studies needs to clarify the role of glycosaminoglycans on progression of retinopathy in type 2 diabetic patients.

Treating azotemia-induced anemia with erythropoietin improves diabetic eye disease

BACKGROUND

Coincidental with the pandemic growth of diabetes as the prime cause of end-stage renal disease (ESRD), blindness attributable to diabetic retinopathy has become a major concern for all those involved in the care of diabetic ESRD patients. Vision loss is linked to progression of proliferative retinopathy and macular edema.

METHODS

Extracted from a study of azotemic anemic pre-ESRD patients treated with erythropoietin, a cohort of five diabetic subjects was reassessed in terms of stability of renal function, changes in blood rheology, and course of diabetic eye disease.

RESULTS

All subjects reported subjective improvement in well-being, including enhanced effort tolerance following an increase in hematocrit from a baseline level of to 29.6 +/- 2.0% to a level of 39.5 +/- 2.4% after one year of treatment with erythropoietin (P = <0.0005). Neither hypertension nor deterioration of renal function was noted in any subject. Three patients with macular edema evinced substantive improvement-based stable vision and documented resolution noted in flourescein angiography.

CONCLUSION

Erythropoietin treatment of anemic azotemic diabetic patients is well tolerated. In a small observational retrospective study of three patients with macular edema, retention of vision and resolution of exudates was noted.

Pharmacologic therapy for diabetic retinopathy

Diabetic retinopathy remains one of the major causes of acquired blindness in developed nations. This is true despite the development of laser treatment, which can prevent blindness in the majority of those who develop macular oedema (ME) or proliferative diabetic retinopathy (PDR). ME is manifest by retinal vascular leakage and thickening of the retina. The hallmark of PDR is neovascularisation (NV)--abnormal angiogenesis that may ultimately cause severe vitreous cavity bleeding and/or retinal detachment. Pharmacologic therapy aimed specifically at preventing vascular leakage and NV would be a welcome addition to the armamentarium. PDR and ME could be prevented by improved metabolic control or by pharmacologically blunting the biochemical consequences of hyperglycaemia (e.g., with aldose reductase inhibitors, inhibitors of non-enzymatic glycation or by protein kinase C [PKC] inhibition). The angiogenesis in PDR could be treated via growth factor (e.g., vascular endothelial growth factor [VEGF], insulin like growth factor-1 [IGF-1]) blockade, integrin (e.g., alpha-v beta-3) blockade, extracellular matrix alteration (e.g., with steroid compounds) or interference with intracellular signal transduction pathways (e.g., PKC and mitogen activated protein kinase [MAPK] pathway proteins). Some of these antiangiogenic agents may also prove useful for treating or preventing ME. Numerous potentially useful antiangiogenic compounds are in development; two drugs are presently in clinical trials for treatment of the preproliferative stage of PDR, while two are in clinical trials for treatment of ME.

Ophthalmologic emergencies in the patient with diabetes

Diabetes is associated with many emergent ophthalmologic conditions. The management of patients with diabetes requires careful monitoring for visual symptoms and frequent physical examination for signs of retinopathy. Randomized studies have documented a significant reduction in the development of new retinopathy and the progression of existing retinopathy with tight control of diabetes. Photocoagulation laser therapy is helpful in preserving vision in severe nonproliferative retinopathy, for proliferative retinopathy, and for clinically significant macular edema. Vascular events include arterial and venous occlusions and cranial nerve palsies; important diagnostic clues are visual symptoms and the findings of ocular and neurologic examinations. Life-threatening infections associated with diabetes include endophthalmitis and mucormycosis, which require prompt diagnosis to prevent blindness or systemic infection. Herpes zoster infection, which is common in older patients and in patients with immunosuppression, may affect the trigeminal nerve and cause anterior uveitis and keratitis. Patients with zoster and skin vesicles on the face need emergent ophthalmologic evaluation and treatment because untreated ocular infection and inflammation may lead to scarring and synechiae formation in the anterior chamber, resulting in vision loss.

Quantitative image analysis of laser-induced choroidal neovascularization in rat

Rodent models of laser-induced choroidal neovascularization (CNV) are now extensively used to identify angiogenic proteins, determine the role of specific genes with knockout mice, and evaluate the efficacy and safety of anti-angiogenic therapies. CNV is typically evaluated by fluorescein angiography or vascular endothelial cell labeling in histologic sections. The current study examined an alternative method using high molecular weight FITC-dextran (MW 2 x 10(6)) for high resolution angiography in RPE-choroid-sclera flat mounts. At 24 hr after lasering, the lesions appeared as a circular weakly fluorescent area of approximately equal diameter to the laser spot. No FITC-dextran labeled blood vessels were visible in the lesion at day 1. Three days after lasering, 47% of the lesions showed FITC-dextran labeling indicative of CNV. The incidence (71%) and extent of CNV increased by day 6, and by day 10 all lesions were vascularized, and the maximal area was attained. No significant change followed day 10, and the neovascular area remained constant through day 31. The highest rate of blood vessel growth (between 3 and 10 days after laser) correlates with the peak expression of VEGF, bFGF, and their receptors shown in previous studies. Morphologic analysis of flat mounts and histologic sections showed that the neovascular plexus in most lesions originates from deeper choroidal vessels in the center of the lesion, grows towards the neural retina, then branches circumferentially to anastamose with uninjured choriocapillaris. The microvessels in these lesions are broad and flat, similar to normal choriocapillaris. In a separate study, rats were treated daily with the angiostatic corticosteroid dexamethasone (20-500 microg kg(-1)day(-1)), and CNV was examined at day 10 in FITC-dextran labeled flat mounts and histologic sections. Dexamethasone dose-dependently inhibited CNV, and its highest dose inhibited approximately 95% of CNV labeled by FITC-dextran and resulted in lesions with no detectable Factor VIII immunostaining. High resolution angiography with FITC-dextran is reproducible and quantifiable, and it may accelerate the discovery of therapeutic agents that modulate choroidal neovascularization.

Biomaterials used in the posterior segment of the eye

The treatment of posterior segment eye disease and related conditions has improved greatly in recent years with the advent of new therapies, materials and devices. Vitreoretinal conditions, however, remain significant causes of blindness in the developed world. Biomaterials play a major role in the treatment of many of these disorders and the success rate of vitreoretinal surgery, especially in the repair of retinal detachment and related conditions, would increase with the introduction of new and improved materials. This review, which focuses on disorders that feature retinal detachment, briefly describes the anatomy of the eye and the nature and treatment of posterior segment eye disorders. The roles, required properties and suitability of the materials used in vitreoretinal surgery as scleral buckles, tamponade agents or drug delivery devices, are reviewed. Experimental approaches are discussed, along with the methods used for their evaluation, and future directions for biomaterial research in the posterior segment of the eye are considered.

Inhibition of mitosis and microtubule function through direct tubulin binding by a novel antiproliferative naphthopyran LY290181

The mechanism of action of a novel antiproliferative compound LY290181 [2-amino-4-(3-pyridyl)-4H-naphtho(1,2-b)pyran-3-carbonitrile] was characterized. LY290181 is a potent inhibitor of cell proliferation, producing 50% inhibition of vascular smooth muscle, endothelial, Chinese hamster ovary, HeLa, and human erythroleukemia cells at concentrations of 8-40 nM. Cell cycle analysis showed that LY290181 caused accumulation of smooth muscle cells at the G2/M phase and induced mitotic arrest in Chinese hamster ovary cells and HeLa cells. At low concentrations (3-30 nM), LY290181 blocked transition of cells from metaphase to anaphase and disrupted mitotic spindle organization. At high concentrations (>/=100 nM), LY290181 produced a concentration-dependent loss of cytoplasmic and spindle microtubules. LY290181 inhibited the polymerization of purified bovine brain microtubule protein into microtubules, and it depolymerized preformed microtubules. Using tubulin-1-anilino-8-naphthalene sulfonate complex fluorescence, we have shown that LY290181 directly interacted with tubulin in a unique manner. These studies show that LY290181 induces cell growth arrest in prometaphase/metaphase, and tubulin appears to be its molecular target.

(S)-13-[(dimethylamino)methyl]-10,11,14,15-tetrahydro-4,9:16, 21-dimetheno-1H, 13H-dibenzo[e,k]pyrrolo[3,4-h][1,4,13]oxadiazacyclohexadecene-1,3(2H)-d ione (LY333531) and related analogues: isozyme selective inhibitors of protein kinase C beta

Protein kinase C (PKC) is a family of closely related serine and threonine kinases. Overactivation of some PKC isozymes has been postulated to occur in several diseases states, including diabetic complications. Selective inhibition of overactivated PKC isozymes may offer a unique therapeutic approach to disease states such as diabetic retinopathy. A novel series of 14-membered macrocycles containing a N-N'-bridged bisindolylmaleimide moiety is described. A panel of eight cloned human PKC isozymes (alpha, beta I, beta II, gamma, delta, epsilon, sigma, eta) was used to identify the series and optimize the structure and associated activity relationship. The dimethylamine analogue LY333531 (1), (S)-13-[(dimethylamino)methyl]-10,11,14,15-tetrahydro-4,9:16, 21-dimetheno-1H, 13H-dibenzo[e,k]pyrrolo[3,4-h][1,4,13]oxadiazacyclohexadecene++ +-1,3(2H)-dione, inhibits the PKC beta I (IC50 = 4.7 nM) and PKC beta II (IC50 = 5.9 nM) isozymes and was 76- and 61-fold selective for inhibition of PKC beta I and PKC beta II in comparison to PKC alpha, respectively. The additional analogues described in the series are also selective inhibitors of PKC beta. LY333531 (1) exhibits ATP dependent competitive inhibition of PKC beta I and is selective for PKC in comparison to other ATP dependent kinases (protein kinase A, calcium calmodulin, caesin kinase, src tyrosine kinase). The cellular activity of the series was assessed using bovine retinal capillary endothelial cells. Retinal endothelial cell dysfunction has been implicated in the development of diabetic retinopathy. Plasminogen activator activity stimulated by a phorbol ester (4 beta-phorbol 12,13-dibutyrate) in endothelial cells was inhibited by the compounds in the series with ED50 values ranging from 7.5 to 0.21 microM. A comparison of the PKC isozyme and related ATP dependent kinase inhibition profiles is provided for the series and compared to the profile for staurosporine, a nonselective PKC inhibitor. The cellular activity of the series is compared with that of the kinase inhibitor staurosporine.

Renal syndromes in diabetes

Renal disorders attributed to diabetes mellitus are increasingly recognized as the dominant feature of long-term management. Renal failure in diabetic patients is the most commonly recognized cause of irreversible uremia in the United States, Europe, and Japan. Treating hypertension and normalizing hyperglycemia slows the previously thought inexorable progress of renal insufficiency in diabetes. Once end-stage renal disease has developed, either dialytic therapy or a renal transplant affords life extension, often with excellent rehabilitation.

Nonsteroidal anti-inflammatory drugs alter chloride and fluid transport in bovine retinal pigment epithelium

Nonsteroidal anti-inflammatory drugs (NSAIDs) were added to the solutions bathing the apical membrane of bovine retinal pigment epithelium (RPE)-choroid explants. For example, niflumic acid (100 microM) depolarized the basolateral membrane voltage (VB) by approximately 12 mV, increased transepithelial potential by 4.5 mV, decreased intracellular Cl activity by 13 mM, decreased transepithelial resistance by 17 omega.cm2, and increased the ratio of apical to basolateral membrane resistance nearly threefold. All of these changes are consistent with an increase in basolateral membrane Cl conductance. In addition, niflumic acid caused intracellular Ca concentration to decrease by 16 nM and fluid transport rate to increase by 1.5 microliters.cm-2.h-1. Flufenamic acid, which is structurally very similar to niflumic acid, had the opposite effects on membrane voltage and resistance. Basal application of the Cl channel blocker 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid or current clamping VB to the reversal potential for Cl practically abolished the niflumic acid response. The niflumic acid results suggest that certain NSAIDs can directly alter Cl conductance in the bovine RPE, apparently independently of cyclooxygenase inhibition.

Orbital sonography in children

Orbital sonography with color-flow Doppler imaging is a relatively new technology with significant application in the pediatric patient. This review stresses the primary indications for pediatric ophthalmic ultrasound and also discusses those instances where the use of ultrasound supplements other imaging studies.

Erythropoietin in diabetic macular edema and renal insufficiency

Erythropoietin was administered to five anemic azotemic diabetic subjects for 1 year to assess the effect of increasing red cell mass on clinical well-being and the course of renal functional decline. None of the subjects manifested worsened hypertension or cerebrovascular or cardiovascular complications despite an increase in mean hematocrit from a baseline mean of 29.6% to a mean of 39.5%. The serum creatinine concentration after 1 year of treatment with erythropoietin was 3.7 mg/dL, which was unchanged from the baseline value of 3.5 mg/dL. Plasma viscosity remained constant as red cell mass increased. Although the viscosity of whole blood rose as the hematocrit increased, it was within the range of normal blood viscosity for an equivalent hematocrit. The favorable impact of erythropoietin treatment on three diabetic subjects who had macular edema and anemia is described. One hypothesis to explain the benefit of a raised hematocrit on both diabetic nephropathy and retinopathy is that the metabolic, hormonal, and hemodynamic components of the diabetic syndrome, in concert, produce tissue and cellular hypoxia that is ameliorated in part by the greater oxygen-transporting capacity of a raised red cell mass. The pseudohypoxia of diabetes may be implicated in the pathogenesis of diabetic neuropathy, retinopathy, muscular dysfunction, and nephropathy.

Neuropathology of the retina in acquired immunodeficiency syndrome

The pathogenesis of HIV-mediated neurodegeneration is unknown. Presently, work is focused on two main hypotheses: direct (caused by HIV or component proteins) versus indirect (monocyte-mediated) neurotoxicity. In HIV-induced retinal disease, the high incidence of opportunistic infections and the low HIV viral burden found in most clinical specimens present challenges in defining the roles played by potential factors. Future studies will see the resolution of these controversies by showing the mechanism of HIV-induced neuronal damage and its relationship to retinal disease.