A defect in the blood-retina barrier in the optic nerve head region in the rabbit and the monkey

The permeability properties of the tissues in the optic nerve head region have been investigated in monkey and rabbit using horseradish peroxidase as an histochemical tracer. Following intravenous administration, the tracer diffused from the peripapillary choroid into the different parts of the optic nerve head region, and also into the receptor layer of the sensory retina adjacent of Kuhnt intermediary tissue. This observation demonstrates a defect in the blood-retina barrier in this region. The defect in the permeability barrier is most likely located either to the retinal pigment epithelium near the optic nerve head, to the Kuhnt intermediary tissue, or to the junction between these tissues.     

Investigations of the enzymes involved in the fructose breakdown in the cattle lens

By introducing fructose into the glycolysis, it is possible to stimulate ATP formation. As is the case in animal experiments, in human lenses, too, the first step in the phosphorylation to fructose-1-phosphate via the enzyme ketohexokinase. The present investigation deals with the question whether enzymes present in the lens are responsible for the further steps in fructose degradation. Particularly the aldolase isoenzyme C splits fructose-1-phosphate into glyceraldehyde and dihydroxyacetone phosphate in the same way as in glucose catabolism. Dihydroxyacetone phosphate can further be directly degraded and thus utilized to ATP formation. From glyceraldehyde, glycerol (aldose reductase) or glycerate (aldehyde dehydrogenase) can be formed. The presence of triosekinase, which phosphorylates glyceraldehyde directly to glyceraldehyde-3-phosphate, could only be determined in the lens tissue of young animals. The presence of glycerokinase (glycerol leads to glycerophosphate) could not be verified. Thus, in the lens tissue 1 ATP molecule net per fructose molecule can be formed. In older age, the glucose breakdown is limited by hexokinase and phosphofructokinase, so that the glucose, after transformation via the sorbitol pathway to fructose, can also be utilized for the energy metabolism.     

Keeping the practice in the family

Congress eased the bite of gift and estate taxes but complying with federal rules and regulations is an often complex and frustrating process. However, close adherence to the rules and a search for so-called "loopholes" can be quite rewarding for the optometrist's family and heirs. Professional assistance is required in this area but this paper presents an overview of basic tax provisions and estate-planning strategies, and offers hints for overcoming a few of the potentially troublesome pitfalls created by the law.     

Role of low and high spatial frequencies in the face-selective responses of neurons in the cortex in the superior temporal sulcus in the monkey

There are neurons in the cortex in the anterior part of the superior temporal sulcus of the macaque monkey with visual responses selective for faces. One aim of the present study was to analyze further the information which leads them to respond, by measuring their responses to parametrically filtered stimuli. The responses of 32 such single neurons were measured to faces which were digitized, lowpass filtered at spatial frequencies of 2, 4, 8,...128 cycles/face, highpass filtered at frequencies of 4, 8,...64 cycles/face, and presented in random sequence using a video framestore. It was found that many of the neurons could respond to blurred images of faces, with a mean frequency at half-maximum amplitude of the neuronal response to the series of lowpass filtered images of faces of 3.3 cycles/face. Almost all the neurons had lowpass cutoff frequencies defined in this way below 8 cycles/face. Many of the neurons could also respond to images of faces in which the only information remaining was a limited amount of high spatial frequency edge information. The mean frequency at half-maximum amplitude of the neuronal response to the series of highpass filtered images of faces was 29.7 cycles/face. Almost all the neurons had highpass cutoff frequencies above 8 cycles/face. Thus, many of the neurons could respond to a lowpass and a highpass filtered image of a face even when these had no spatial frequencies in common. The mean separation between the lowpass and highpass cutoff frequencies was 3.2 octaves. For comparison, face recognition in man can be performed with images which contain only information up to 8 cycles/face, or with highpass filtered images which contain only information down to 8 cycles/face. The response of the neurons was not always a smooth function of frequency, but could decrease as higher frequencies were included in the lowpass filtered images of faces, or as low frequencies were included in the highpass filtered images of faces. This indicates that information in certain frequency bands was able to inhibit these neurons. This was particularly likely to occur for the non-optimal face stimulus for a given neuron, indicating that the selectivity of these neurons to different faces was a combination of the excitation produced by some information in faces and inhibition produced by other.     

Changes in the oscillatory potentials of the electroretinogram in glaucoma

Dark adapted and progressively light adapted electroretinograms (ERGs) were recorded from 34 normals and from 45 glaucoma patients. To enhance the oscillatory potentials (OP) the ERGs were highpass-filtered. The OP were characterized by two indices: their root-mean-square value and the inter-flash interval for which the maximal amplitude was obtained. In most of the glaucomatous OP, 50 of 81 eyes, both indices were abnormal, in 22 one parameter was abnormal and only in 9 were both parameters normal. In 13 of the 14 OP recorded from the opposite ('normal') eye of patients with unilateral glaucoma either one or both of the indices were abnormal. These findings indicate that the damage to the retina in glaucoma may extend more distally than the ganglion cell layer and that subclinical changes might be revealed by OP changes.     

Ophthalmology in Europe in the days of the French Revolution

The authors highlight the political and scientific landmarks in 18th century France; the Revolution of 1789 had positive effects, in that it marked the accession of the French middle-class to political power and enabled the promotion of young scientists without consideration of social class or fortune; it had negative effects, in that France lost the scientific edge it had gained when all existing chairs in ophthalmology were abolished. The status of ophthalmology and of physiological optics in the 18th century are discussed, with a brief mention of the most important innovators in the field.     

Changes in the oscillatory potentials in the electroretinogram during the evolution of diabetic retinopathy

Oscillatory potentials where intensely studied in diabetic patients with various degrees of retinopathy. Classical reports pointed out the early reduction of their amplitude, as well as of their latency, while a and b waves remained still normal. A prognostic value was attached to these modifications, the reduction of oscillatory potentials being correlated with a ten time higher probability of developing a high risk retinopathy. 27 diabetic patients where investigated electroretinographically by us. No significant variation of the amplitude of oscillatory potentials was observed during the progression of diabetic retinopathy.     

Errors in determining the direction of the visual axis in the presence of defocus

The visual axis is the ray path from the fixation point to the fovea by way of the nodal points. Such a ray path does not exist in unaccommodated vision when the fixation point does not coincide with the far point of the eye because of induced or natural defocus. Nevertheless an approximation to the visual axis can be obtained by the position of a small pupil close to the cornea for which a bichromatic vernier target appears correctly aligned. When the visual axis is determined, an eye rotation from the visual fixation position must occur, which is reversed upon removing the small pupil. Upon engaging in any experiments for which the visual axis is then used as a reference, there is an error in this reference position. We develop simple paraxial equations to estimate this error. We show that these equations have good accuracy. The error associated with locating the visual axis at the cornea is 0.002 mm per dioptre of defocus, which is small enough to be ignored.     

Voriconazole in the treatment of fungal osteomyelitis of the orbit in the immunocompromised host

Scedosporium apiospermum is an uncommon cause of fungal infection in the orbit and sinus. Morbidity and mortality rates in immunocompromised patients are high. We review the first case of Scedosporium apiospermum orbito-sinus infection that was successfully treated with the new antifungal agent voriconazole. We highlight the efficacy of this drug, particularly in the treatment of osteomyelitis of the orbit and sinus, which may lead to an improvement in survival rates after Scedosporium infection.