Efficacy and tolerability of 0.2% brimonidine tartrate for the treatment of acute non-arteritic anterior ischemic optic neuropathy (NAION): a 3-month, double-masked, randomised, placebo-controlled trial

Treatment of nonarteritic anterior ischemic optic neuropathy

Nonarteritic anterior ischemic optic neuropathy (NAION) is the most common clinical presentation of acute ischemic damage to the optic nerve. Most treatments proposed for NAION are empirical and include a wide range of agents presumed to act on thrombosis, on the blood vessels, or on the disk edema itself. Others are presumed to have a neuroprotective effect. Although there have been multiple therapies attempted, most have not been adequately studied, and animal models of NAION have only recently emerged. The Ischemic Optic Neuropathy Decompression Trial, the only class I large multicenter prospective treatment trial for nonarteritic anterior ischemic optic neuropathy, found no benefit from surgical intervention. One recent large, nonrandomized controlled study suggested that oral steroids might be helpful for acute NAION. Others recently proposed interventions are intravitreal injections of steroids or anti-vascular endothelial growth factor (anti-VEGF) agents. There are no class I studies showing benefit from either medical or surgical treatments. Most of the literature on the treatment of NAION consists of retrospective or prospective case series and anecdotal case reports. Similarly, therapies aimed at secondary prevention of fellow eye involvement in NAION remain of unproven benefit.

Non-arteritic anterior ischemic optic neuropathy (NA-AION) after intravitreal injection of bevacizumab (Avastin) for treatment of angoid streaks in pseudoxanthoma elasticum

BACKGROUND

To report a case of nonarteritic anterior ischemic optic neuropathy (NA-AION) following intravitreal injection of bevacizumab (Avastin).

METHODS

Interventional case report with an 18-month follow-up.

RESULTS

A 51-year-old male with pseudoxanthoma elasticum presented with NA-AION 2 weeks after treatment with intravitreal of bevazicumab (Avastin) for choroidal neovascularisation secondary to angioid streaks. Except from a small optic disc without cupping he did not show further risk factors.

DISCUSSION

Risk of NA-AION should be taken into consideration when deciding for intravitreal application of drugs including anti-vascular endothelial growth factors (VEGF) agents like bevacizumab (Avastin) in the treatment of retinal vascular diseases.

A critical discussion of the rates of progression and causes of optic nerve damage in glaucoma: International Glaucoma Think Tank II: July 25-26, 2008, Florence, Italy

The International Glaucoma Think Tank II brought together glaucoma clinicians and researchers from all over the world to discuss current practices in glaucoma diagnosis and management, and the neurobiology of glaucoma. The meeting focused on several themes, including rates of deterioration in glaucoma patients, mechanisms of optic nerve damage, and implications for treatment. Issues such as how to measure and integrate progression information into clinical practice, screening protocols, or trials were discussed, as were promising new technologies and limitations of currently available measurement tools. Clinical applications for genetic testing were considered. Study of the neurobiology of glaucoma continues to inform our understanding of underlying degenerative processes, as well as to introduce possibilities for early detection or prevention. Many questions regarding glaucoma pathophysiology and best treatment practices remain unanswered, but with continued research and discussion, we will advance our understanding of this disease and ensure that patients receive optimal care.

Neuroprotection: extrapolating from neurologic diseases to the eye

PURPOSE

To review the current status of neuroprotection in ophthalmic disease.

DESIGN

Perspective.

METHODS

Published and unpublished data on neuroprotection in neurologic and ophthalmologic diseases were reviewed and interpreted.

RESULTS

Almost all clinical studies of neuroprotection in neurologic and ophthalmologic disease so far have failed to show efficacy, despite encouraging preclinical studies.

CONCLUSIONS

Achievement of consensus on how to design and execute translational research in neuroprotection in ophthalmic disease would optimize the use of resources and would hasten the development and approval of effective neuroprotective agents.

Ischemic optic neuropathies

Anterior ischemic optic neuropathy (AION) is the most common cause of acute optic neuropathy after age 50, but may also occur in younger patients. The diagnosis is clinical and includes painless visual loss associated with a relative afferent pupillary defect and disc edema. In almost all cases, there is an underlying crowded optic nerve with a small cup-to-disc ratio. The visual prognosis is usually poor, although up to 43% of patients may improve over time. The fellow eye is involved in up to 15% of patients within 5 years, but the risk of recurrence in the same eye is less than 5%. There is no treatment for acute nonarteritic AION but it is essential to evaluate these patients for underlying treatable atheromatous vascular risk factors. A coagulation workup should also be considered in younger patients. It is essential to rule out giant cell arteritis in all patients over the age of 50 with ischemic optic neuropathies. Posterior ischemic neuropathy (in which the optic nerve is normal acutely) is rare and should be considered a diagnosis of exclusion.

Nonarteritic anterior ischaemic optic neuropathy

PURPOSE OF REVIEW

There have been many reports in recent literature concerning the use of scanning laser polarimetry, Heidelberg retinal tomography and optical coherence topography in assessing the optic nerve and peripapillary nerve fibre layer. It is important to assess the validity of new equipment and see whether this has improved our understanding of the disease. There are also reports about possible association of nonarteritic anterior ischaemic optic neuropathy with cataract surgery and phosphodiesterase type-5 inhibitors. This review attempts to look at some of the techniques used and possible associations with nonarteritic anterior ischaemic optic neuropathy.

RECENT FINDINGS

Scanning laser polarimetry, Heidelberg retinal tomography and optical coherence tomography have been helpful in quantifying optic nerve and peripapillary retinal nerve fibre layer defects, with different efficacy and limitations. Although these confirm the damage to retinal nerve fibre layer beyond what is detected by standard visual field examination, the effect of cataract surgery and phosphodiesterase type-5 inhibitors remains to be further studied on a larger scale. The few experimental treatments for nonarteritic anterior ischaemic optic neuropathy also need further confirmatory studies.

SUMMARY

More studies are required to evaluate the benefits of new imaging methods. The availability of a primate model may provide clues to assessing experimental treatments for nonarteritic anterior ischaemic optic neuropathy.

A pilot study of topical treatment with an alpha2-agonist in patients with retinal dystrophies

PURPOSE

The aim of this study was to assess the neuroprotective effect of a topical alpha2-agonist in patients with retinal dystrophies.

METHODS

This study was a prospective, placebo-controlled, double-masked, randomized clinical trial. A total of 26 patients with retinal dystrophies were included. One (1) randomly selected eye was treated with brimonidine tartrate 0.2% twice-daily, while the fellow eye received artificial tears. Disease progression parameters tested at 6-8-month intervals throughout the study included Goldmann visual fields, contrast sensitivity, color vision, and fullfield electroretinography.

RESULTS

Seventeen (17) of the 26 recruited patients completed the study. Except for 1 patient with an 18-month follow-up, all patients were followed up for 24-36 months (mean, 29). At the conclusion of the study, there were no differences detected in visual acuity, color vision, and contrast sensitivity between the treated and control eyes. There was a trend, however, toward a lesser degree of visual field loss in the brimonidine-treated eyes. There was also a delay in the time required to reach a 25% visual field loss in the treated eyes. These differences were more pronounced in a subgroup of patients diagnosed as retinitis pigmentosa and with visual fields of 5 cm2 or more at baseline.

CONCLUSIONS

The findings of this pilot study suggest a trend for slower progression in the eyes of patients with retinal dystrophy when treated with brimonidine, according to one of the parameters that was studied (visual field loss). Further studies that include a larger number of patients and a longer follow-up period are needed to clarify and confirm the potential neuroprotective effect of alpha2-agonists in human retinal dystrophies.

Neuroprotective effects of brimonidine treatment in a rodent model of ischemic optic neuropathy

Ischemic optic neuropathy (ION) is a common disorder caused by disruption of the arterial blood supply to the optic nerve. It can result in significant loss of visual acuity and/or visual field. An ischemic optic nerve injury was produced in rats by intravenous injection of Rose Bengal dye followed by argon green laser application to the retinal arteries overlying the optic nerve, causing a coagulopathy within the blood vessels and disruption of optic nerve and retinal perfusion. The effect of brimonidine tartrate eye drops on survival of retinal ganglion cell axons in this experimental paradigm was studied. One eye was treated and the contralateral eye served as a control. Four groups of animals were used for this study. Group 1 received 7 days of treatment with 0.15% brimonidine tartrate eye drops twice a day prior to the ischemic injury. Group 2 animals received 0.15% brimonidine tartrate eye drops twice a day for 14 days after photocoagulation injury. Animal groups 3 and 4 received eye drops of 0.9% NaCl twice a day either daily for 7 days before injury or daily for 14 days, respectively. All rats were sacrificed 5 months after the injury to ascertain long-term optic axon survival. Coagulopathy-induced optic nerve ischemia resulted in a 71% loss of optic axons. Treatment with brimonidine daily for the 7 days prior to the injury resulted in a greater survival of optic axons, with only a 56.1% loss compared to control. Brimonidine treatment every day for 14 days after the ischemic injury did not result in a significant rescue of optic axons compared to injury alone. In summary, the application of brimonidine eye drops for one week prior to an ischemic injury resulted in a statistically significant increase in survival of optic axons within the injured optic nerves. Brimonidine treatment of the eye after the ischemic injury did not result in axon rescue, and axon loss was similar to the injured optic nerves treated with saline only. These results suggest that brimonidine may have potential use for prevention of ION in at-risk patients.