G. H. M. Van Lith

Estimation of visual function after optic neuritis: a comparison of clinical tests.

A group of 53 patients who had suffered an attack of unilateral (n = 45) or bilateral (n = 8) optic neuritis more than six months before were subjected to a battery of tests to determine their spatial contrast sensitivity, visual field, and colour vision. The 106 eyes investigated were classified according to their clinical status and visual acuity at the time of the study into unaffected (n = 45), recovered (n = 33), and non-recovered (n = 28). At least one of the three tests gave an abnormal result in 67%, 88%, 100% of the three groups respectively. The results obtained with these three tests showed a significant statistical association.

Variation in latency times of visually evoked cortical potentials.

Latency times of visually evoked cortical potentials stimulated by reversal of a slow checkerboard pattern are highly dependent on the time needed to accomplish the reversal movement. If, owing to the method, the pattern reversal time is not kept stable, variability of the latency times is unnecessarily high for clinical purposes. This may be the case when television equipment is used.

Measuring oscillatory potentials: Fourier analysis

Studying the oscillatory potentials in diabetic retinopathy, the authors experienced several problems interpreting results of digital filtering. The main problem was the separation of the first potential from the a-wave, since their frequencies are within the same range. To improve the procedure of measuring implicit times and of calculating amplitudes, the filtering was started with a finite impulse response filter and followed by a fast Fourier transform. The power of the oscillatory potential was calculated by determining the dominant frequency in the Fourier transformed response and expressed in microwatts. A group of normal subjects was compared with a group of early diabetic retinopathy patients. It appears that even in pathological circumstances a quantitative expression of the oscillatory potential is possible.

The pattern-elicited electroretinogram. I: A tool in the early detection of glaucoma?

The pattern-elicited electroretinogram (PERG) was recorded in 75 patients known with glaucoma, each one of them having a normal visual acuity, and compared with the results in normal test subjects. Although there is a great overlap between normal and glaucomatous eyes, a lower average amplitude and a delay in latency is recorded in the case of glaucoma. A correlation was sought between the PERG outcome on the one hand and different glaucomatous parameters (visual field loss, intraocular pressure, cup disc/ratio) on the other; this could only be confirmed for the cup/disc ratio. In beginning glaucoma the PERG is more often disturbed than the VECP.

Retinal dystrophy in long chain 3-hydroxy-acyl-coA dehydrogenase deficiency

BACKGROUND Long chain 3-hydroxy-acyl-CoA dehydrogenase (LCHAD) is one of the enzymes involved in the breakdown of fatty acids. A deficiency of this enzyme is associated with life threatening episodes of hypoketotic hypoglycaemia during prolonged fasting. Neuropathy and retinopigmentary changes were mentioned in only a few cases. METHODS The case histories of two girls, aged 8 and 15 years, with LCHAD deficiency are reported. RESULTS Both children with LCHAD deficiency exhibited extensive macular pigmentary depositions and a ‘salt and pepper’ scattering of pigment in their retinas. The patients have decreasing visual acuity. CONCLUSION The early recognition of LCHAD deficiency can increase the life expectancy in these patients through avoiding catabolism and through appropriate diets. Patients tend to be free of symptoms between attacks, however. Testing for the disorder, therefore, should be included in the diagnostic process for children with retinal dystrophy, in particular when other clinical symptoms are known to have occurred.

Blue-Yellow Colour Vision Changes as Early Symptoms of Ethambutol Oculotoxicity

To find out the most sensitive parameter of early toxic ocular changes, a group of patients was extensively examined at regular intervals during therapy with ethambutol. Colour vision abnormalities could be detected using the desaturated panel of Lanthony in the presence of normal visual acuity, normal visual fields, normal visual-evoked potentials and a normal panel D-15 test. Major blue-yellow errors were found in treated patients without visual complaints as well as in a group of healthy volunteers, but there was a significant difference between both groups. In a later stage of intoxication, blue defects, red-green defects or tritanomalous defects can be observed, together with other symptoms of ocular intoxication.

Visual function and pattern visual evoked response in optic neuritis.

The disparity between clinical visual function and pattern visual evoked response (VER) was studied in 53 patients who had suffered an attack of optic neuritis (ON) more than six months before. The visual functions tested included Snellen visual acuity, colour vision, visual field, and contrast sensitivity. The effect of pattern presentation, check size, and luminance was tested by recording VERs with several stimulus configurations. VER amplitudes were found to be associated with the outcome of all four clinical tests, independently of check size, luminance, or the presentation method used. On the other hand VER latencies were hardly ever related to the results of any of the four clinical visual tests. These findings support the idea that VER amplitude provides information about visual spatial perception, while VER latency is more related to the extent of demyelination.

Pattern EPs in endocrine orbitopathy

Since delayed pattern evoked potentials (EPs) are a sensitive symptom of demyelination or compression of the optic nerve, a group of 33 patients with endocrine orbitopathy were examined in order to see whether or not, in this disease too, damage to the optic nerve could be detected at an early stage. Below a visual acuity of 0.4, all patients had delayed responses. Most interesting was the group of patients with normal visual acuity and delayed responses. Before conclusions can be drawn this group will have to be enlarged and followed up.

Oscillatory potentials in early diabetic retinopathy.

To study the oscillatory potentials in early diabetic retinopathy the authors developed a new power measurement based on the fast Fourier transform. Three groups totalling 46 patients were examined, varying from nonvisible to preproliferative diabetic retinopathy. The oscillatory potentials expressed in microwatts were measured under scotopic and photopic conditions. The data of the three groups are compared with those of a group of 22 normal individuals. The oscillatory potential power measurement appears to be a reliable method in detecting diabetic retinopathy at an early stage.

Ophthalmological examination of patients taking chloroquine

EOGs have been routinely measured once a year in rheumatoid arthritis (RA) patients treated with chloroquine derivatives.Criterion for the advice to stop the treatment was a decrease in the EOG of more than 20% of the value obtained before treatment was started or, where this value had not been determined, a decrease in the EOG to below 1.85, i.e. the Arden criterion.Evaluating the results, it appears that in RA patients, examined once a year, the variability of the EOG is approximately 30% of the value obtained. Furthermore, instead of a lower limit for the normal value of 1.85, we found in the rheumatism group 1.6. If these new criteria were to be applied, less than 4% of the patients would be advised to stop chloroquine treatment. We wonder whether check-ups of these patients remain necessary when dosage of chloroquine or its equivalent is below 75 g per year.