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April 2009 Newsletter

Is Whole Eye Transplantation Possible?

Rarely does a day go by when a patient doesn't ask about whether eye transplantation is possible. The stock answer is "No," primarily because the optic nerve (which connects the eye to the brain) will not regenerate once it has been cut. But a review of the scientific literature in the March edition of the British Journal of Ophthalmology seems to offer some hope.

The article addresses three specific questions:

(1) Is recovery of visual function following eye transplantation greater in cold-blooded vertebrates compared with mammals? The researchers found that in a majority of the studies, recovery of visual function can occur after whole eye transplantation in cold-blooded vertebrates.

(2) Will the retinal photoreceptors continue to function after an eye has been removed from the body (a procedure known as enucleation) and then reconnected? The literature review finds that following enucleation retinal photoreceptor function is maintained from four to nine hours.

(3) The nerve cells that make up the optic nerve are known as ganglion cells. The researchers investigated whether there is a correlation between ganglion cell survival and either time after transection or proximity of optic nerve transection to the eye? The researchers found that the longer the eye is disconnected from the body, the more ganglion cells will die. Also, more nerve cells will die if the optic nerve is cut nearer the eye. However, newly developed drugs, such as neurotrophins, can increase ganglion cell survival following transection.

The researchers conclude that the use of a donor eye is feasible for whole eye transplantation. While technically feasible, it will be many years before this will be a viable treatment option. On the other hand, retinal prosthetics - sometimes referred to as "bionic eyes" - are an exciting technological advance that is projected to be commercially available by the end of 2010.

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Red Meat Consumption Associated With Increased Risk Of AMD

Eating lots of red meat has been linked to a higher risk of developing AMD.

The researchers conducted a study of 6,734 persons aged 58-69 years in 1990-1994 in Melbourne, Australia. Meat intake was estimated from a food frequency questionnaire at baseline.

The investigators found that compared to those who ate red meat less than five times a week, people who ate it 10 or more times a week were nearly 50% more likely to develop AMD in old age. However, they also found that people who ate chicken at least three times a week were 50% less likely to develop the condition compared with those eating it less than once a week.

Fish consumption was not associated with AMD, the report indicates.

The researchers concluded that different types of meat appear to have different effects on the risk of developing AMD and helping people change their dietary habits could be a way to help them lower risk of developing AMD.

WHAT IT MEANS TO YOU: It is important to recognize that association does not imply causation. People who eat large amounts of red meat were found to have higher rates of AMD. Does this suggest that eating red meat causes AMD? Of course not! Perhaps, for example, people who eat red meat 10 or more times per week eat very few veggies? Or perhaps these people are more obese, or have higher blood pressure, etc. Before swearing off red meat, its important to recognize that there are many possible explanations for this association other than red meat causes AMD. Of additional concern is that this study failed to find a beneficial effect of fish consumption.

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Lutein Is Neuroprotective During Inflammation

A study finds that lutein decreases retinal cell damage during inflammation in mice.

Lutein is a carotenoid that is concentrated in the retina. It is thought that lutein may help protect the retina from oxidative stress and damage from high-energy blue light. However, there has, to date, been no convincing evidence that lutein intake is protective against the development of AMD. Lutein is being studied as part of the AREDS2 study.

The current study investigates, with the use of a mouse endotoxin-induced uveitis (EIU) model, the neuroprotective effects of lutein against retinal neural damage caused by inflammation.

The EIU-induced photoreceptor damage was prevented by lutein treatment. Inflammatory cytokine signals and reactive oxygen species, which are both upregulated during EIU, were reduced by lutein. Pathologic change of Muller glial cells was also prevented by lutein.

The researchers conclude that lutein was neuroprotective during EIU, suggesting a potential approach for suppressing retinal neural damage during inflammation.

WHAT IT MEANS TO YOU: There is strong evidence that inflammation plays a major role in the genesis of AMD. The importance of the complement factor H gene in AMD genetics supports this hypothesis. The role of inflammation in the development of AMD could mimic the processes of chronic inflammation in the pathogenesis of atherosclerosis. The finding that lutein can mitigate retinal cell damage from inflammation would seem to support the notion that lutein therapy could aid in the prevention of vision loss from AMD.

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Avastin For Subfoveal Choroidal Neovascularization In Highly Myopic Eyes

A small prospective study of intravitreal Avastin (bevacizumab) for subfoveal and juxtafoveal myopic choroidal neovascularization (CNV) finds that it is an effective and safe therapeutic procedure.

The use of intravitreal antiangiogenic drugs to treat myopic CNV faces some specific risks, in addition to those inherent with intravitreous injection. First, the higher frequency of peripheral vitreoretinal lesions may increase the risk of retinal tears or detachments. Secondly, the use of antiangiogenic drugs among patients of childbearing age increases the concern of birth effects. Yet, the advantages of this therapy compared with PDT/steroid therapy are a lower risk of cataracts and glaucoma, as well as less RPE atrophy.

This was a prospective, nonrandomized pilot study. Twenty-six highly myopic eyes from 25 patients with subfoveal and juxtafoveal CNV were treated by three monthly intravitreal injections of Avastin. Fifteen eyes were naive for treatment and 11 eyes had been previously treated by photodynamic therapy (PDT) (average 2.5 PDT sessions).

Patients averaged 49.5 years of age. Five patients were male and 20 were female. Average spherical equivalent was -14.0 D (range -7.0 to -22.0 D). BCVA at baseline averaged 20/62 (range 20/200-20/32) and 20/38 (range 20/160-20/20) at month 6. Average central foveal thickness was 282.4 µm at baseline and 224.0 µm at month 6. Leakage from CNV had ceased in all eyes at month 3 and CNV was still closed at month 6. No safety issues appeared during follow-up.

The researchers conclude that intravitreal Avastin seems to be an effective and safe therapeutic procedure to treat subfoveal and juxtafoveal CNV in highly myopic eyes. They state that Avastin seems to be a useful in these patients as a first line therapy and after unsuccessful previous PDT. The investigators state that randomized trials comparing Avastin therapy with PDT are needed.

WHAT IT MEANS TO YOU: It is not clear whether the stimulus for CNV in myopia is the same as that in AMD. Therefore, treatments that are effective for AMD are not necessarily effective for myopic CNV. There are currently no randomized controlled trials of anti-VEGF therapy for myopic CNV, and no drugs are currently approved for the treatment of myopic CNV. Small case series of off-label use of Avastin and Lucentis have generally reported favorable results, but special precautions, as mentioned above, are warranted in this distinctive patient population.

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Laser Photocoagulation Vs. Steroids For Diabetic Macular Edema

The Diabetic Retinopathy Clinical Research Network did not find a benefit of intravitreal triamcinolone relative to laser photocoagulation in patients with diabetic macular edema (DME) after 3-years of follow-up.

Macular edema is a frequent manifestation of diabetic retinopathy and an important cause of vision loss in these individuals. A clinical trial involving 693 subjects evaluated intravitreal triamcinolone (1- and 4-mg doses) compared with focal/grid photocoagulation for the treatment of DME.

The study found that there was an initial beneficial effect of 4 mg of triamcinolone at 4 months compared with a 1-mg dose or with focal/grid photocoagulation. However, the benefit diminished thereafter, and at 2 years, mean visual acuity was better in the laser group than in either of the other 2 groups. Optical coherence tomography (OCT) results paralleled the visual acuity results. Both triamcinolone doses, especially the 4-mg dose, were associated with an increased incidence of elevated intraocular pressure and cataract surgery.

Between 2 years (time of the primary outcome) and 3 years, more eyes improved than worsened in all 3 treatment groups. Change in visual acuity letter score from baseline to 3 years was +5 in the laser group and 0 in each triamcinolone group. The cumulative probability of cataract surgery by 3 years was 31%, 46%, and 83% in the laser and 1-mg and 4-mg triamcinolone groups, respectively. Intraocular pressure increased by more than 10 mm Hg at any visit in 4%, 18%, and 33% of eyes, respectively.

The researchers conclude that there was no long-term benefit of intravitreal triamcinolone relative to laser photocoagulation. Rather, visual acuity outcomes slightly favored the laser group over either of the 2 triamcinolone groups. It appears that most eyes receiving this 4-mg triamcinolone preparation will require cataract surgery, though only a few will develop glaucoma.

WHAT IT MEANS TO YOU: There is a great deal of interest in finding a safe and effective medical therapy for diabetic retinopathy. The finding that steroids could improve vision in persons with DME was met with great excitement. The standard therapy for DME is laser photocoagulation. Laser therapy is effective, but as with any surgical intervention, there are also associated risks. This study found that over 3 years steroid therapy is less effective and is associated with a higher risk of cataract and glaucoma. Studies are ongoing investigating the use of Avastin and Lucentis in the treatment of DME.

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Complement Factor H Determines Benefit Of Fish Consumption

Weekly fish consumption decreases the risk of late AMD only in persons with the high-risk complement factor H (CFH) genotype, a study finds.

CFH is an important regulator of the complement system. Persons having the high-risk CFH genotype are roughly 6 times more likely to have AMD than persons with the low-risk genotype.

Fish oil is rich in omega-3 fatty acids. Studies have found that consumption of foods rich in omega-3 fatty acids and fish intake twice or more per week may prevent AMD. Furthermore, AREDS participants reporting the highest consumption of fish oil were approximately 30% less likely to develop advanced AMD.

This study assessed the combined effects of CFH genotypes with smoking, fish consumption, and inflammatory markers on the risk of AMD in 3,654 persons aged 49 years. They reexamined participants after 5 and 10 years.

The high-risk genotype (denoted as CC) was present in 13.6% of the participants. The low-risk genotype (TT) was found in 39.7% of the participants. A mixed genotype (CT) was the most common, present in 46.7% of the participants.

As expected, the risk of AMD was higher in CT participants than TT participants, and highest in CC participants.

Weekly compared with less than weekly consumption of fish was associated with reduced AMD risk in participants with the high-risk CC genotype, but not the mixed CT or low-risk TT genotypes.

The researchers conclude that joint contributions from genetic and systemic factors are involved in determining the progression of AMD.

WHAT IT MEANS TO YOU: Other than the AREDS vitamin-mineral supplement, fish oil is the only other intervention that has been consistently found to decrease the risk of vision loss from AMD. (However, a study suggesting that folic acid may also be able to prevent AMD has been published). Recently, the AREDS study group reported that their supplement is only statistically significantly effective in preventing disease progression in persons with the high risk CFH genotype. Now, just as with the AREDS supplement, this study reports that fish consumption cuts the risk of AMD only in persons with the high-risk CFH genotype. While these persons are at highest risk for the disease, most persons (including many people that develop AMD) do not have this genotype. Additional research is necessary to better understand the interaction between genetic and systemic factors in AMD.

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Avastin Plus Radiation Therapy For AMD

A study of Avastin (bevacizumab) plus epiretinal brachytherapy combination treatment of subfoveal CNV secondary to AMD reports favorable safety and efficacy data.

In this prospective, non-randomised, multicenter study, 34 treatment-naive patients with subfoveal CNV received a single treatment with 24 Gy beta radiation (strontium-90) and two injections of Avastin.

Twelve months after treatment, no radiation-associated adverse events were observed. At 12 months 91% of patients lost less than 3 lines of vision, 68% improved or maintained their BCVA, and 38% gained 3 lines. The average change in BCVA observed at month 12 was a gain of 8.9 letters.

The safety and efficacy of intraocular, epiretinal brachytherapy delivered concomitantly with anti-VEGF therapy for the treatment of subfoveal CNV secondary to AMD were promising in this small study population. These results are consistent with earlier studies of radiation combined with anti-VEGF therapy.

WHAT IT MEANS TO YOU: Radiation therapy is effective in treating ocular neovascularization. It is not only antiangiogenic but also anti-inflammatory. This study shows that it can work synergistically with Avastin to combat CNV associated with AMD. This radiation treatment is currently being evaluated in a large, multicenter, FDA phase III study.

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Emerging Treatments For AMD

Jason S. Slakter, MD, discussed emerging AMD treatments during the Irving H. Leopold Lecture at the Wills Eye Institute Alumni Conference. Lucentis has revolutionized the treatment of AMD. However, anti-VEGFs alone are not effective for all patients, Dr. Slakter said, and studies are under way on new treatments. Sirolimus targets mTOR, a protein that plays a role in promoting VEGF. The agent is in phase 2 trials. RTP801, a small interfering RNA molecule that suppresses VEGF production, is in phase 1 testing for intravitreal delivery. VEGF Trap-Eye (Bayer HealthCare, Regeneron), a fusion protein that inhibits the VEGF molecule, has been effective in improving visual acuity and reducing choroidal neovascularization. The agent is now in phase 3 testing against Lucentis. Emerging treatments for dry AMD include an implant that produces and delivers ciliary neurotrophic factor, a neuroprotective agent. Early data from a phase 2 study of geographic atrophy showed favorable results, Dr. Slakter said.

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One Year Results Of Iluvien Steroid Implant For Diabetic Macular Edema

Alimera Sciences has reported 12-month safety and efficacy results from the first human pharmacokinetic study of its Iluvien steroid implant for treating patients with diabetic macular edema. Each Iluvien insert is designed to provide a sustained therapeutic effect for up to 36 months for low doses and up to 24 months for high doses, according to a press release from the company. According to 12-month interim results, 23.1% of the low-dose patients and 27.3% of the high-dose patients achieved an improvement in best corrected visual acuity of 15 letters or greater from baseline, according to the release. No adverse events related to IOP were seen in the low-dose patients, while 23.5% of the high-dose patients experienced IOP spikes greater than 30 mm Hg. Data from this study will be evaluated on an ongoing basis, with interim results reported at 18, 24, 30 and 36 months.

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Employment Of Visually Impaired People In The UK

Employment rate among working age people in the UK who are registered blind or partially sighted is estimated at 33% according to a survey of visually impaired people conducted by VISION 2020. This figure is approximately the same as was found when the survey was conducted in 2005. In terms of differences across ages, the highest proportion of respondents in employment is found in the 30-49 age group (44%) then the 18-29 group (at 33%) and the lowest proportion in the 50-64 group (only 22%). The data was collected during interviews with 503 visually impaired people of working age between November 2006 and January 2007. All the participants were registered as either blind or partially sighted and lived in Great Britain. The employment rate amongst visually impaired people is very low compared to the general working age population. Overall, three quarters of the general population reported being in some form of employment. Visually impaired individuals of working age are much more likely to describe themselves as being unemployed, long term sick or disabled, or retired than those in the general population.

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Safety Of Intravitreal Avastin And Lucentis Injections

A study reports on the frequency of complications associated with Avastin and Lucentis therapy in a busy university-based retina practice over a 2-year period. Four hundred fifty patients receiving 2,000 injections (1,275 Avasatin and 725 Lucentis) were studied retrospectively. Injections were performed in a usual examination room under the standard sterile conditions. Follow-up varied from 3 to 24 months. Serious ocular adverse events were uncommon. Only one patient developed retinal detachment (0.05%). Most common procedure-related ocular adverse event was injection-site redness (64.75%). Postoperative subconjuctival hemorrhage occurred after 200 (10%) injections. Patients receiving aspirin treatment were more prone to have subconjuctival hemorrhage (P = 0.0002). Most common drug-related ocular adverse event was uveitis (1.90%), which was treated successfully and lasted no longer than 12 days. There was no statistically significant difference between the patients treated with Avastin or Lucentis regarding the noted adverse events (P > 0.5%). The investigators conclude that Avastin and Lucentis were both well tolerated and safe. The study appears in the March 2009 edition of the Journal Retina.

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Roche Agrees To Buy Genentech

After months of pursuit, Swiss drugmaker Roche reached an agreement with U.S.-based Genentech to acquire all outstanding shares of the biotechnology firm in a $46.8 billion deal. In the approved deal, Roche said it will pay $95 a share, or approximately $46.8 billion, for the 44% of Genentech it doesn't already own. The combined company is expected to generate $17 billion in annual revenues and save Roche nearly $750 million to $850 million a year, according to statement issued jointly between the companies. Genetech produces Avastin and Lucentis, drugs used in the treatment of neovascular age-related macular degeneration. Roche said its U.S. pharmaceutical commercial operations would operate under the Genentech name so as to leverage the strong brand value of Genentech in the U.S. market. The deal between Roche and Genentech follows nearly two decades of partnership and is expected to result in a combined company that would rank seventh in terms of U.S. pharmaceutical market share.

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Avastin For Diabetic Macular Edema

A prospective evaluation of intravitreal Avastin for diabetic macular edema finds that three monthly injections Avastin results in significant improvement in both visual acuity and central macular thickness, according to a study published in the March 2009 edition of the journal Retina. Fifty-two eyes of 52 patients with diabetic macular edema were randomized to receive three monthly intravitreal injections of 1.25 mg or 2.5 mg Avastin followed for 6 months. Significant mean central foveal thickness reductions were observed in both groups at all follow-up visits (P < 0.013). The investigators conclude that three monthly intravitreal Avastin injections resulted in significant reduction in central foveal thickness and improvements in BCVA in diabetic macular edema patients. This is in agreement with earlier studies that have found that Avastin is effective for diabetic macular edema.

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Bevasiranib SiRNA Therapy For AMD Clinical Trial Terminated

Opko Health has decided to terminate its phase 3 trial of bevasiranib for treating wet AMD, the company announced in a press release. The decision to conclude the clinical program follows a review of preliminary trial data which found that although the trial was unlikely to meet its primary endpoint, the release said. Bevasiranib is a first-in-class small interfering RNA (siRNA) drug designed to silence the genes that produce vascular endothelial growth factor (VEGF), believed to be largely responsible for the vision loss of wet AMD. Bevasiranib was the first therapy based on RNA interference technology to advance to Phase III clinical trials. The study identified no systemic or ocular safety issues with bevasiranib.

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