Dipotassium diaqua-bis(methyl-enedi-phospho-nato-κO,O')cobaltate(II).

In the title complex, K(2)[Co(CH(4)O(6)P(2))(2)(H(2)O)(2)], the asymmetric unit contains two K(+) cations and two half-anions in which the Co atoms lie on inversion centers. The Co(II) ions assume an octa-hedral CoO(6) coordination geometry. In the crystal, a three-dimensional network is formed through O-H⋯O hydrogen-bond inter-actions as well as inter-molecular inter-actions between the K(+) cations and neighbouring O atoms.

Pyridinium diaqua-bis-(methyl-enediphospho-nato-κO,O')chromate(III) tetra-hydrate.

In the title complex, (C(5)H(6)N)[Cr(CH(4)O(6)P(2))(2)(H(2)O)(2)]·4H(2)O, the Cr(III) atom, lying on an inversion centre, is coordinated by two bidentate methyl-ene diphospho-nate ligands and two water molecules in a distorted octa-hedral coordination geometry. The pyridinium cation is located on an inversion centre, with an N atom and a C atom sharing a position each at a half occupancy. A three-dimensional network is constructed by O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds between the pyridin-ium cation, complex anion and uncoordinated water mol-ecules.

Diammonium diaqua-bis(methyl-enediphospho-nato-κO,O')cobaltate(II).

In the salt, (NH(4))(2)[Co(CH(4)O(6)P(2))(2)(H(2)O)(2)], the methyl-ene-diphospho-nate acts as a bidentate ligand and the Co(II) ion (site symmetry ) assumes an octa-hedral CoO(6) coordination geometry. The acid H atom of the ligand is distributed over two O atoms. In the crystal, a three-dimensional network is formed through O-H⋯O and N-H⋯O hydrogen bonds between the cations and anions.

Photorefractive keratectomy for hyperopia after radial keratotomy.

BACKGROUND: Progressive hyperopia is a common complication following radial keratotomy. METHODS: Ten eyes of ten consecutive patients with hyperopia after radial keratotomy between +1.75 and +4.00 diopters (D) were treated with the hyperopia module of the Nidek Model EC-5000 excimer laser. The mean preoperative uncorrected visual acuity was 0.38 (20/60+). RESULTS: After excimer laser photorefractive keratectomy (PRK), mean uncorrected visual acuity improved to .72 (20/30+). No complications occurred with the exception of one eye with haze greater than 2+. CONCLUSION: PRK for hyperopia is a valuable method for correcting hyperopia after radial keratotomy.

Peribulbar anesthesia. A prospective statistical analysis of the efficacy and predictability of bupivacaine and a lignocaine/bupivacaine mixture.

The object of this trial was to determine the efficacy in peribulbar anesthesia of bupivacaine 0.5%, 0.75%, and a combination of bupivacaine 0.5% and lignocaine 2% in equal parts. Fifty-one and 50 patients in random order were injected with 0.5% and 0.75% bupivacaine, respectively, and another 50 patients with the lignocaine/bupivacaine mixture. The results were recorded and all data were statistically analyzed. We concluded that the peribulbar route with the agents used in this trial was not a successful technique. Our criterion for a successful block, i.e., akinesia, was not achieved in more than 54% of cases.

Posterior peribulbar anaesthesia for intra-ocular surgery.

Posterior peribulbar anaesthesia is a safe alternative to the better-known retrobulbar route because the local anaesthetic agent is deposited outside the ocular muscle cone and away from the retrobulbar nerves and blood vessels. The potential dangers of a retrobulbar injection are therefore greatly reduced but the same degree of anaesthesia and akinesia is achieved. The much safer and easier posterior peribulbar technique for intra-ocular surgery is described with reference to more than 400 cases.