Volume 5, Number 35
Monday, September 5, 2005



In this issue: (click heading to view article)
Erythropoietin as a Retinal Angiogenic Factor in Proliferative Diabetic Retinopathy
Abnormal Fundus Autofluorescence in AMD Patients
Ethambutol Ocular Toxicity in Treatment Regimens for Mycobacterium avium Complex Lung Disease
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Erythropoietin as a Retinal Angiogenic Factor in Proliferative Diabetic Retinopathy

Vascular endothelial growth factor (VEGF) is a primary mediator of retinal angiogenesis, but VEGF inhibition alone is insufficient to prevent retinal neovascularization. It is therefore believed that other potent ischemia-induced angiogenic factors exist. According to Japanese investigators, erythropoietin is a powerful ischemia-induced angiogenic factor acting independently of VEGF during retinal angiogenesis in proliferative diabetic retinopathy.

In this study, researchers measured both erythropoietin and VEGF levels in the vitreous fluid of 144 patients using radioimmunoassay and enzyme-linked immunosorbent assay. They measured vitreous proliferative potential according to the growth of retinal endothelial cells in vitro and with soluble erythropoietin receptor. They also used a murine model of ischemia-induced retinal neovascularization to evaluate erythropoietin expression and regulation in vivo.

The median vitreous erythropoietin level in 73 patients with proliferative diabetic retinopathy was significantly higher than that in 71 patients without diabetes (464.0 vs. 36.5 mIU per milliliter). The median VEGF level in patients with retinopathy was also significantly higher than that in patients without diabetes (345.0 vs. 3.9 pg per milliliter). Multivariate logistic-regression analyses indicated that erythropoietin and VEGF were independently associated with proliferative diabetic retinopathy and that erythropoietin was more strongly associated with the presence of proliferative diabetic retinopathy than was VEGF. Erythropoietin and VEGF gene-expression levels are upregulated in the murine ischemic retina, and the blockade of erythropoietin inhibits retinal neovascularization in vivo and endothelial-cell proliferation in the vitreous of patients with diabetic retinopathy in vitro.

SOURCE: Watanabe D, Suzuma K, Matsui S, et al. Erythropoietin as a retinal angiogenic factor in proliferative diabetic retinopathy. New Engl J Med 2005;353(8):782-92.
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Abnormal Fundus Autofluorescence in AMD Patients

A study by Germany’s University of Bonn aimed to describe and classify patterns of abnormal fundus autofluorescence (FAF) in the junctional zone of geographic atrophy (GA) in patients with age-related macular degeneration (AMD).

Researchers recorded digital FAF images in 164 eyes of 107 patients using a confocal scanning laser ophthalmoscope (cSLO; excitation 488 nm, detection above 500 nm) as part of a prospective, multicenter natural history study (FAM Study). They obtained FAF images in accordance with a standardized protocol for digital image acquisition and generation of mean images after automated alignment.

Image quality was sufficient for classification of FAF patterns in 149 eyes (90.9 percent); lens opacities were the most common reason for insufficient image quality. Abnormal FAF outside GA in 149 eyes was classified into four patterns: focal (12.1 percent), banded (12.8 percent), patchy (2.0 percent) and diffuse (57.0 percent); 12.1 percent had normal background FAF in the junctional zone. Four percent of patients had no predominant pattern. The investigators subdivided the diffuse pattern into four groups, including reticular (4.7 percent), branching (27.5 percent), fine granular (18.1 percent) and fine granular with peripheral punctate spots (6.7 percent).

The authors believe that these distinct patterns may reflect heterogeneity at a cellular and molecular level, in contrast with a non-specific aging process. They suggest that a refined phenotypic classification may be helpful to identify prognostic determinants for the spread of atrophy and visual loss, for identification of genetic risk factors and for the design of future interventional trials.

SOURCE: Bindewald A, Schmitz-Valckenberg S, Jorzik JJ, et al. Classification of abnormal fundus autofluorescence patterns in the junctional zone of geographic atrophy in patients with age related macular degeneration. Br J Ophthalmol 2005;89(7):874-8.
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Ethambutol Ocular Toxicity in Treatment Regimens for Mycobacterium avium Complex Lung Disease

Ethambutol (EMB) is an important component of multidrug treatment regimens for Mycobacterium avium complex lung disease, and ocular toxicity is the most significant potential EMB toxicity, especially in the elderly population with M. avium complex lung disease. Researchers at the University of Texas and the Louisiana State University studied 229 patients with M. avium complex lung disease and found that intermittent EBM administration was associated with less ocular toxicity than daily EMB administration.

Of the 229 patients, 55 percent were women and 53 percent had nodular/bronchiectatic disease. Each received a mean of 16.1 +/- 10.8 months of multidrug therapy that included EMB. Fifty patients (22 percent) were known to have preexisting ocular disease. While on EMB, 97 patients (42 percent) consulted an ophthalmologist and 24 (10 percent) stopped EMB at least temporarily. Eight of 139 patients (6 percent) on daily therapy were diagnosed with EMB ocular toxicity, whereas 0 of 90 patients on intermittent therapy had EMB ocular toxicity. All patients with EMB ocular toxicity developed symptoms between outpatient clinic appointments; none were diagnosed with routine visual acuity and color vision testing. All patients with EMB ocular disease returned to baseline ocular status after discontinuation of EMB.

SOURCE: Griffith DE, Brown-Elliott BA, Shepherd S, et al. Ethambutol ocular toxicity in treatment regimens for Mycobacterium avium complex lung disease. Am J Respir Crit Care Med 2005;172:250-3.
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BRIEFLY
  • NATIONWIDE RECALL OF TRYPAN BLUE 0.06% OPHTHALMIC SOLUTION ANNOUNCED. Custom RX Compounding Pharmacy of Richfield, MN, is initiating a nationwide recall of Trypan Blue 0.06% Ophthalmic Solution, used during cataract surgery, because it may be contaminated with Pseudomonas aeruginosa. The FDA warns users of Trypan Blue to discontinue using it immediately. The solution was distributed to hospitals and clinics in Maryland, Minnesota, Illinois, Nebraska, North Dakota, Michigan, the District of Columbia and Pennsylvania. The dark blue solution is packaged in 1-cc sterile tuberculin syringes. Custom Rx Pharmacy requests that all unexpired syringes be collected and returned to the company. The recall includes, but may not be limited to, the following lot numbers: 05042005:86@17, 05252005:36@13, 06282005:91@27, 08012005:63@24 and 08182005:43@17. Custom RX has voluntarily recalled its product based on two reports of loss of vision, possibly associated with use of the product, by the Centers for Disease Control, as well as a positive bacterial culture obtained at an outside hospital. Custom RX has verified the processes and technicians involved preparing Trypan Blue and is keeping the FDA apprised of its recall efforts. It is working with the FDA on its investigation into the cause of the contamination. For more information, contact Verne Betlach at (612) 866-2211 or (612) 810-1363.
  • CIBA VISION EXPANDS O2OPTIX PARAMETERS. CIBA Vision’s O2Optix silicone hydrogel contact lenses are now available in expanded parameters, in minus powers ranging from -0.25D to -8.00D in 0.25D steps, and from -8.50D to -10.00D in 0.50D steps. In October, the company will add plus powers from +0.25D to +6.00D in 0.25D steps, thus covering 94 percent of spherical vision-corrected eyes. For more information, go to www.cibavision.com.
  • FDA APPROVES FINAL PHASE OF CLINICAL TRIAL FOR SCLERAL SPACING PROCEDURE. Refocus Group, Inc. has received FDA approval to begin enrollment in the final round of clinical trial surgeries for the company"s Scleral Spacing Procedure (SSP) for treatment of presbyopia. A significant percentage of the planned Phase II total of 150 study participants have been enrolled and randomized in a two-to-one surgical or control group. All surgical patients received the company"s SSP for the treatment of presbyopia. The procedure involves the placement of four scleral implants just under the surface of the sclera in the four quadrants; it is the same procedure used for treatment of glaucoma and/or ocular hypertension. For these conditions, Refocus believes that the procedure may restore the natural base-line tension in the ciliary body, allowing for improvement in the eye’s natural drainage and a lowering of intraocular pressure. When used to treat presbyopia, the company believes that SSP helps reduce crowding of the underlying tissues surrounding the crystalline lens, allowing the muscles to naturally reshape the lens and accommodate the eye. SSP does not remove tissue from the eye and does not affect the cornea; it is believed to be fully reversible. For more information, go to www.refocus-group.com.


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