Sorption and degradation characteristics of phosmet in two contrasting Australian soils.

The organophosphate insecticide phosmet [phosphorodithioic acid, s-((1,3-dihydro-1,3-dioxo-2H-isoindol-2yl)methyl), o,o-dimethyl ester] is used to control red-legged earth mites (Halotydeus destructor), lucerne flea (Sminthurus viridis), and Oriental fruit moth (Cydia molesta) in horticulture and vegetable growing. This study was undertaken with two soils of contrasting properties to determine the extent to which sorption and degradation of the insecticide might influence its potential to leach from soil into receiving waters. Two soils were used: a highly organic, oxidic clay soil (Ferrosol) and a sandy soil low in organic matter (Podosol), sampled to 0.3 m depth. The extent of sorption and decomposition rate of a phosmet commercial formulation were measured in laboratory experiments. Sorption followed a Freundlich isotherm at all depths. The Freundlich coefficient K was significantly correlated (p = 0.005) with organic C content in the Podosol, and significantly correlated (p = 0.005) with organic C and clay content in the Ferrosol. K was highest (48.8 L kg-1) in the 0- to 0.05-m depth of the Ferrosol, but lowest (1.0 L kg-1) at this depth in the Podosol. Degradation followed first-order kinetics, with the phosmet half-life ranging from 14 h (0-0.05 m depth) to 187 h (0.2-0.3 m depth) in the Ferrosol. The half-life was much longer in the sandy Podosol, ranging from 462 to 866 h, and did not change significantly with depth. Soil organic C and to a lesser degree clay content influenced phosmet sorption and degradation, but the interaction was complex and possibly affected by co-solvents present in the commercial formulation.

Perfluorocarbon liquids (perfluorodecalin) in vitreoretinal surgery--a local experience.

A low viscosity perfluorocarbon liquid (perfluorodecalin) known commercially as DKLine was used intraoperatively as a temporary vitreous substitute in 20 patients undergoing vitrectomy surgery for a variety of complicated vitreoretinal conditions. The indications for its use included giant retinal tears (9), proliferative vitreoretinopathies (2), dislocated lenses (2), dislocated posterior chamber implant (1), endophthalmitis with retinal detachment (2), traction retinal detachment (1), pseudophakic retinal detachment (2) and exudative retinal detachment (1). In all cases with retinal detachment, perfluorodecalin was successful in flattening the retina intraoperatively. It was also successful in permitting the safe removal of dislocated lenses that were lying on the retina. In all except four cases, removal of perfluorodecalin was complete. We observed no toxic effects from remnant bubbles of perfluorocarbon in the eye.

Secondary syphilis presenting with optic perineuritis and uveitis.

We describe a 40 year-old man with optic perineuritis due to secondary syphilis. This condition which is due to inflammation of the optic nerve sheath is often mistaken for papilloedema or papillitis. We discuss its diagnosis and stress the importance of recognising it because it is easily treated by a course of Penicillin.

Idiopathic subretinal neovascularization.

Idiopathic subretinal neovascularization is a potentially blinding condition and often strikes patients in their prime of life. It appears to be seen in more females, at an earlier age than males. Treatment is possible by photoablation of the subretinal new vessel by Argon or Yag laser. There is a clinical impression that Argon laser is more effective than the Yag laser for this purpose.

Current and future trends in the correction of aphakia: a local perspective.

Over the last 20 years, the correction of aphakia has moved from spectacles and contact lens to intraocular lenses. Advances in lens design and implantation techniques are now in the exciting process of refinement--the aim being bionic perfection.

Implantation and diabetes: analysis of 525 cases.

This is a retrospective study of 525 posterior chamber implants in diabetics performed by A S M Lim and B C Ang of Singapore. The patients were reviewed by visiting ophthalmologists--J E Kennedy (Sydney), M Ngui (East Malaysia) and P M Hart (Belfast). This study did not show any significant difference in the complication of post-operative visual acuity between diabetics and non-diabetics. 95% obtained 6/12 vision or better when pre-existing disease was excluded. It also showed that posterior chamber implants can be inserted in eyes with maculopathy or proliferative retinopathy if laser treatment was effectively done before or after surgery.

Scanning electron microscopic evaluation of posterior chamber intraocular lenses.

A great variety of Intraocular Lenses (IOLs) made by various manufacturers are now available to the Implant Surgeon. The Surgeon must decide which IOLs are better than others, and be aware of physical characteristics of IOLs that would be potentially dangerous to the intraocular structures. The Scanning Electron-Microscope (SEM) is now recognised as a powerful tool in providing detailed information of the physical characteristics of Intraocular lenses. We randomly selected five posterior chamber intraocular lenses from each of five different manufacturers and subjected them to scanning with the SEM to evaluate their physical qualities as well as to assess the consistency of manufacture. Striking differences in quality of finish of the intraocular lenses were revealed. The consistency of quality of good or of defective characteristics was high amongst manufacturers.

Eye diseases in the elderly in Singapore.

Ocular disorders in the elderly have become more important because of increased longevity and the demand for good vision. Many serious ocular conditions are age-related and they include cataract, glaucoma, diabetic retinopathy and other retinal conditions. The most important ocular disorder is cataract which fortunately is curable with excellent results when a posterior chamber implant is inserted. Angle closure glaucoma is common in the elderly Singapore Chinese and can be effectively treated with microscopic peripheral iridectomy or trabeculectomy. Blindness from diabetic retinopathy can be prevented with argon laser photocoagulation. In most cases blindness is preventable with early diagnosis e.g. in glaucoma and diabetic retinopathy. Severe visual loss in the elderly requires careful explanation and compassion by doctors and social workers.