Clinical outcome of intravitreal gentamicin injection for the treatment of end-stage glaucoma in five rabbits (eight eyes).

Background: Glaucoma is a painful and blinding condition that occurs in many species, including rabbits. When medication is no longer effective in maintaining intraocular pressure (IOP), enucleation is the recognized treatment for rabbits with end-stage glaucoma. However, this procedure carries risks relating to the procedure and the anesthesia. Aim: The aim of this retrospective study was to report the efficacy of intravitreal gentamicin injection in controlling IOP in blind eyes of rabbits with end-stage glaucoma. Ocular and non-ocular complications were retrospectively assessed. Methods: Medical record review was performed to identify five client-owned rabbits (eight eyes) that were treated by intravitreal injection of 6-20 mg of gentamicin per eye (median 7.18 mg/kg) for chronic, end-stage glaucoma. Treatment was unilateral in two and bilateral in three rabbits. IOP control was assessed via rebound tonometry readings performed approximately 2 weeks, 1 month, 3 months, and 6 months after injection. Total follow-up was between 313 and 1,111 days. Ocular complications were recorded and systemic health was estimated by the owner-answered questionnaire and changes in body weight. Results: IOP was <25 mmHg in 87.5% of eyes 3 months post-injection. The most common ocular complications were cataracts (62.5%), anterior uveitis (25%), retinal detachment (12.5%), and corneal erosion (12.5%). There were no behavioral or body weight changes suggestive of systemic complications. Conclusion: 87.5% of rabbit eyes treated with intravitreal gentamicin had controlled IOP 3 months after injection. All eyes were blind at the time of injection. Ocular side effects were common. Investigation of the safety and systemic effects of intravitreal gentamicin injection is required; however, no overt complications were identified in treated rabbits in this study.

An asymmetric distribution of positrons in the Galactic disk revealed by gamma-rays.

Gamma-ray line radiation at 511 keV is the signature of electron-positron annihilation. Such radiation has been known for 30 years to come from the general direction of the Galactic Centre, but the origin of the positrons has remained a mystery. Stellar nucleosynthesis, accreting compact objects, and even the annihilation of exotic dark-matter particles have all been suggested. Here we report a distinct asymmetry in the 511-keV line emission coming from the inner Galactic disk ( approximately 10-50 degrees from the Galactic Centre). This asymmetry resembles an asymmetry in the distribution of low mass X-ray binaries with strong emission at photon energies >20 keV ('hard' LMXBs), indicating that they may be the dominant origin of the positrons. Although it had long been suspected that electron-positron pair plasmas may exist in X-ray binaries, it was not evident that many of the positrons could escape to lose energy and ultimately annihilate with electrons in the interstellar medium and thus lead to the emission of a narrow 511-keV line. For these models, our result implies that up to a few times 10(41) positrons escape per second from a typical hard LMXB. Positron production at this level from hard LMXBs in the Galactic bulge would reduce (and possibly eliminate) the need for more exotic explanations, such as those involving dark matter.

Astronomy (communication arising): black holes, fleas and microlithography.

Fresnel lenses allow almost perfect imaging in widely different circumstances, but their focus is perfect only for a single wavelength. Wang et al. have shown how the effective bandpass may be widened for X-ray microscopy by using a compound diffractive/refractive lens near to an absorption edge. A compound lens has also been proposed for high-energy astronomy, working well above all absorption edges. Although the scale is very different, we point out here that the principle is the same. Ever since Galileo constructed an astronomical telescope that he was able to reconfigure to study fleas and gnats, astronomy and microscopy have relied on optics that are closely related, but different in detail.