Toxocaral infection in hydatid control officers: diagnosis by enzyme immunoassay.

An enzyme-linked immunosorbent assay for Toxocara canis larva excretory/secretory antigen has been set up in Christchurch. Employing this test, elevated specific antibody levels for toxocara larvae were found in 3.3% (3/90) of urban adult blood donors and 4.4% (4/90) of secondary school students. In comparison, elevated levels were present in 25.6% (23/90) of New Zealand hydatid control officers. It can be concluded from the present study that the higher risk of toxocariasis experienced by hydatid officers is reflected in elevated specific antibody titres in a significant proportion of individuals when compared with controls.

The clinical value of ophthalmic electrodiagnosis in children.

A group of 113 children with poor vision who had been referred to the Electrodiagnostic Clinic over a five year period were investigated for disease of the retina and optic pathway by electroretinography (ERG), electro-oculography (EOG) and visual evoked response (VER). The electrodiagnostic measurements were made using an automated system developed at Christchurch Hospital. The results of these investigations confirmed the clinical value of ophthalmic electrodiagnosis both as an aid in the diagnosis of these young patients and in determining their prognosis. In some cases it permitted an early detection of their condition. In addition the analyses of the ERG into rod and cone mediated responses helped to establish the diagnosis of hereditary retinal disorders and was particularly useful in the case of infants with nystagmoid movements of the eyes who were suspected of having poor vision. Interestingly 21 of the 113 patients were found to have functional visual loss. These patients complained of visual loss but subsequent examinations revealed their ocular findings, EOG, ERG and VER were all normal. The age of this functional visual loss group ranged from 7 to 15 years, with the average being 11.3 years (SD = 2.6 years). Furthermore they were a large group representing 32% of all the children between 7 and 15 years and in most cases were not happy at school.

Pattern VEP for glare sensitivity testing.

Conditions such as optic neuritis and cataract cause a patient to be unduely affected by glare and this occurs even though they may have normal visual acuity. A new test incorporating visual evoked potential (VEP) and glare sensitivity has been developed in Christchurch which shows promise for the objective assessment of such conditions. This report describes the methodology of the new technique and its application to the glare sensitivity testing of fifteen normal volunteers and ten patients with post optic neuritis. The effect of glare was expressed in terms of the glare disability score (GDS). This was defined as the percentage reduction in the amplitude of the P2 peak in the VEP waveform after glare was introduced. In these preliminary results, in spite of relatively good visual acuity, nine out of ten patients with a past history of optic neuritis showed elevated GDS values indicating that they were more sensitive to glare than the normal volunteers. In addition we report a dramatic reduction in the GDS of one patient with a lens opacity following extracapsular cataract extraction and the implantation of an intraocular lens.

A comparison of two patient-friendly ERG electrodes.

The ideal electroretinography (ERG) electrode does not exist. In deciding which electrode should be used in clinical practice the capacity to provide reproducible waveforms, maximal amplitudes and minimal irritation to the patient's eyes are the most important characteristics. This study tested two patient friendly electrodes, the gold foil (CH Electrodes, UK) and the H-K loop (Avanta, Slovenia). Seventeen normal volunteers were subjected to three standard measurements namely flash ERGs under photopic and scotopic conditions and the transient pattern ERG (PERG). Each test followed the guidelines set by the International Society for Clinical Electrophysiology of Vision (ISCEV). It was found that the mean values of the flash ERG a and b wave amplitudes and the PERG P50 and N95 amplitudes from the gold foil electrodes were approximately a factor of two larger than those from the H-K loop. In addition most of the subjects (13/17) felt less discomfort with the gold foil electrodes. We reached the conclusion that gold foil electrodes are the electrode of choice because they provide good patient comfort, reasonably high amplitudes and relatively reproducible results.

Acute ocular methanol toxicity: clinical and electrophysiological features.

PURPOSE: The present report describes previously undocumented changes in the electroretinogram (ERG) and visual-evoked response (VER) following acute methanol ingestion and highlights the ocular effects of methanol poisoning. METHODS: Two cases of acute ocular damage following methanol ingestion are presented. One patient underwent extensive electrophysiological and psychophysical testing. RESULTS: Both patients reported transient visual disturbances. In each patient vision was 6/6 in both eyes at presentation but subsequently improved to 6/4. Colour vision (Ishihara plates) and pupillary reactions were normal. The optic discs were hyperaemic and swollen and retinal oedema extended along the major vascular arcades. There was cystoid macular oedema and 'pseudo cherry red spots' were observed. Automated field analysis revealed a generalized depression of retinal sensitivity, an enlargement of one blind spot and paracentral scotomas. The scotopic ERG was subnormal with diminished a- and b-waveforms and the cone response to flicker was reduced. The pattern VER P2 waveform was normal in latency but decreased in amplitude. CONCLUSIONS: Acute methanol ingestion can cause characteristic ocular damage, together with widespread electrophysiological dysfunction. The data presented suggest that methanol affects the photoreceptors, Muller cells and the retrolaminar portion of the optic nerve.

Serum and neutrophils alter the rate of excretory/secretory antigen release by Toxocara canis infective larvae in vitro.

Infective larvae of Toxocara canis are well suited for studies of nematode antigen expression in vitro. Larvae were labelled with 3H-glucosamine, an approach permitting dual analysis of antigen quantity and composition. Their excretory/secretory (E/S) glycoproteins were efficiently labelled and antigen identity confirmed by immunoprecipitation, SDS-PAGE and fluorography. Compartmental analysis revealed that common components of Mr 100-120 kD were present in somatic, surface and soluble material. The application of biosynthetic labelling and compartmental analysis of parasite responses in vitro to antibody, complement and neutrophils was tested. Results indicated that test larvae in vitro respond by quantitative rather than qualitative changes in antigen production. Specifically, human serum was shown to raise, and neutrophils depress, the rate of antigen release. The implications of these findings for establishing an in-vitro model for analysis of host/parasite reciprocal adaptive responses are discussed.

Retinopathy of prematurity: review of a five-year period, examination techniques and recommendations for screening.

The reported resurgence of retinopathy of prematurity prompted analysis of the prevalence of retinopathy among premature infants born at Christchurch Women's Hospital over a five-year period. Of the 129 surviving very-low-birthweight infants, 65 (50.4%) underwent ocular screening during the review period. Retinopathy was detected in 17.1% (22/129) of surviving infants, or 34% (22/65) of selected infants referred by paediatricians for ocular screening. Five infants had severe or blinding retinopathy and these premature infants were of significantly lower birthweight and born after shorter gestation periods than those found to have no retinopathy. Examination techniques for eyes of premature infants are discussed, and recommendations for screening for retinopathy of prematurity made.

The relationship between toxocara ELISA absorbance values and toxocara ELISA titres: a comparative study.

Enzyme-linked immunosorbent assays (ELISAs) may be made by a variety of techniques at one or several serum dilutions which is very confusing for clinicians. This study compares the ELISA results from two centres on sera from 12 patients investigated for ocular toxocariasis by two common ELISA methods--the absorbance and titration techniques. With one exception, ELISA results by the two methods correlated well. For reasons outlined, the absorbance ELISA method is likely to remain the preferred method in New Zealand and Australia. Attention is drawn to the implications of the serum response to Toxocara canis larvae, and the need to evaluate ELISA results against clinical findings is emphasized.

Ocular Toxocara canis infections: diagnosis by enzyme immunoassay.

An enzyme-linked immunoassay (ELISA) was used to establish the sero-prevalence of Toxocara canis infection in several New Zealand populations including those who, through environment or occupation, had close contact with dogs. The prevalence of positive ELISA values found reflected the degree of dog contact, e.g. positive ELISA's occurred in 2.8% of urban adults, 13.9% of dog breeders and 28.4% of hydatid control officers emphasizing that a history of dog contact needs to be considered when ELISA results are interpreted in a clinical context. Ophthalmoscopy of 102 hydatid officers, 28.4% of whom were seropositive, disclosed no evidence of ocular toxocariasis and suggested that the officers might be immunoprotected. Preliminary immunoblot analysis of the range of toxocara excretory/secretory antigens bound to serum immunoglobulin from patients with presumed visceral larva migrans and ocular toxocariasis, showed the same reactivity profile as a positive reference serum and serum from a seroresponsive hydatid control officer.

A fast system for reporting the Farnsworth-Munsell 100-hue colour vision test.

We have developed a system for rapidly reporting the Farnsworth-Munsell (FM) 100-hue test using a personal computer and a bar code scanner. The computer generated report duplicates the conventional manual report of the FM 100-hue test so is very familiar to ophthalmologists and optometrists. The new system has proved to be of great assistance both in saving time and in eliminating arithmetic errors in the scoring calculations. The scanner technique produces two reports, one for each eye, within 4 min of the patient completing the test. This compares with the 60 min required by the conventional manual reporting system. In addition, it also gives a statistical analysis of the results in accordance with Verriest norms. The program is very versatile and user friendly, achieving a standard not present in the other FM 100-hue computerised systems currently available. As a consequence it makes this valuable diagnostic test much more accessible to patients and clinicians.