眼钝伤后视神经的形态学改变

在动物钝伤模型眼上，通过不同时间对视神经视网膜的形态学观察，并通过病理，电镜对视神经的组织学观察。发现眼钝伤后主要造成视乳头水肿和视网膜出血，水肿等眼底改变，视索纤维在光镜下改变为大小不等的水泡样性及毛细血管扩张，电镜下改变为轴突肿胀，微丝微管数目减少排列紊乱，以及髓鞘结构疏松和板板分离的脱髓鞘现象。     

Paralysis of the awake human: visual perceptions.

Subparalytic doses ofcurarewere given to three observers. Four major perceptions were reported: (1)displacement or repositioning of the perceived visual world in the direction of a successfully executedeye movement; (2)jumping during a saccade; (3)movement associated with drift of the eye; (4) increasedeffort associated with each eye movement. Paralytic doses ofsuccinylcholinewere administered to a single observer. Three major perceptions were reported: (1)displacement in the direction of the intended eye movement without jumping: (2) a sensation that greateffort was required to move the eye; (3)fading of the visual image due to effective retinal stabilization. Similar visual perceptions were observed when the eye was paralyzed with a local anesthetic; however, nofading or sense ofeffort was reported. No deficits in pattern vision (except for intermittent fading) were reported in any of the studies.     

Glutathione peroxidase activity in rat lens and other tissues in relation to dietary selenium intake

Glutathione peroxidase (E.C. 1.11.1.9: glutathione: H₂O₂ oxidoreductase) activity and selenium concentration were measured in lenses of female rats and their offspring after long-term feeding of either a selenium-supplemented ($\text{0·1 parts}\text{10}{}^6$) or selenium-deficient ($\text{<}\text{0·02 parts}\text{10}{}^6$) diet. Long-term selenium deficiency decreased lens glutathione peroxidase activity in parent rats and their offspring to 15 and 14% respectively of supplemented controls. For comparison to lens, glutathione peroxidase was also measured in liver, heart, lung, erythrocytes, kidney, adrenal, testis, and brain of the offspring. Selenium deficiency caused the enzyme to decrease most dramatically in liver (to 0) and least in brain (to 62% of selenium supplemented controls). Although glutathione peroxidase in lens was lower than that in the other organs assayed, it was among the organs more sensitive to depletion caused by selenium deficiency. A short-term selenium deficiency of 8 weeks in newborn lambs had no effect on lens glutathione peroxidase, but the enzyme in organs such as liver was dramatically decreased. Therefore, an extensive period of selenium deficiency appears necessary to affect lens glutathione peroxidase activity, which probably relates to the relatively slow turnover and slow growth of the lens. The possible role of the seleno-enzyme, glutathione peroxidase, in the prevention of cataracts and the relationship of selenium to vitamin E and sulfur-containing amino acids in this regard are discussed.     

The detection and localization of carbonic anhydrase in the rabbit cornea

A new, sensitive micromethod for the determination of carbonic anhydrase has been applied to the rabbit cornea. In this technique the concentration of carbonic anhydrase is related to the rate of exchange of ¹⁸O between labeled bicarbonate and water during the catalyzed dehydration of bicarbonate. Excised rabbit corneas and extracts prepared from the separated layers of rabbit corneas were placed in ¹⁸O-enriched carbonate-bicarbonate buffer solution at pH 9·4 and 25°C. The ¹⁸O content of the bicarbonate at periodic intervals was determined by mass spectrometry.Carbonic anhydrase was found to be present in the rabbit corneal endothelium at an estimated cellular concentration of 10^?6m, the same order of magnitude as in most secretory tissues. No carbonic anhydrase was detected in the stroma or epithelium.     

Acid mucopolysaccharides in the outflow apparatus.

The two major species of phenylalanine transfer RNA (tRNA) of lens cortex have been isolated using BD cellulose and reversed-phase chromatography. Specific activities of 1200 and 1500 pmol of phenylalanine accepted per A₂₆₀ of tRNA were obtained for phe-tRNA₁ and phe-tRNA₂ respectively. The fluorescence emission spectra of both phe-tRNAs were identical, with a fluorescence maximum around 420 nm. These measurements, along with chromatographic data, confirm the presence of the Y base in both tRNAs. Nucleotide analysis was carried out on the purified phe-tRNAs. The composition of phe-tRNA₂ was almost identical to the phe-tRNA of rabbit liver. Phe-tRNA₁, however, had a markedly different major base composition. Phe-tRNA₁ therefore, represents a different gene product than phe-tRNA₂. This was confirmed by the fact that phe-tRNA₁, and phe-tRNA₂ chromatograph as separate peaks on a reversed-phase column in the presence of 8·0 m-urea. Therefore the differentiation of a lens epithelial cell into a lens fiber cell is accompanied by a doubling of phe-tRNA as a result of the activation of a new phe-tRNA gene.     

Retinopathy of prematurity: Screening and optimal use of the ophthalmologist's time

In recent years it has been standard practice to recommend that indirect ophthalmoscopy be carried out between six and nine weeks of age in very low birthweight infants to screen for the presence of retinopathy of prematurity (ROP). Following this recommendation we examined 85 infants over a two-year period. Acute ROP occurred in 29 (34%), and two (2.4%) developed cicatricial disease. One-third of infants were initially examined slightly earlier or later than the strict six to nine week limits, but all except three infants were examined between 35 and 42 weeks gestation. One infant born at 26 weeks gestation, was examined 'too late' in that she had stage 4 disease when first seen at 11 weeks of age. Recent information on the natural history of ROP, and confirmation of the efficacy of treatment with cryotherapy, suggested that the timing of an initial screening examination for ROP needed reassessment. From our experience and a review of the literature we recommend that infants of less than 1000 g birthweight or less than 28 weeks gestation have an initial examination at six weeks of age; for infants of 1000 to 1250 g birthweight or 28 to 30 weeks gestation examination continue to be at six to nine weeks of age; and for infants of more than 1250 g birthweight or 31 weeks gestation screening at six to nine weeks of age is only necessary if the infant has had an unstable course or prolonged oxygen requirements. Such a protocol would not place too great a burden on ophthalmological services and would direct efforts towards the group of infants most at risk of severe visual handicap.     

Segregation of vitamin A1 and vitamin A2 cone pigments in the bullfrog retina

Measurement of the early receptor potential action spectra of the dorsal and ventral areas of theRana catesbeiana retina indicates that there are at least two long-wave cone pigments in this retina and that these pigments are not homogeneously distributed. We suggest that the ventral retina contains predominantly an A₁-based cone pigment absorbing maximally at 580 nm and that the dorsal retina contains a mixture of this A₁-based pigment and an A₂-based pigment absorbing maximally at 620 nm.     

应用随机点同视机立体图测定正常人融合功能的实验研究

目的：研究随机点立体图检测60例正常人立体融合功能的作用,方法：采用随机点同视机立体图（R．DSS,）检测60例10－29岁正常人融合范围,以立体感消失或出现作为判断融合破裂点的标志;计算内外融合比值。结果：①应用R．D．S．S测定融合范围：最大为800组,－94－＋243,最小为60组,－7.4~十17,0,平均范围-8．3±0．7－＋20．9±2.7,①各级内融合均数比较：800－200组与100－60组比较,差异均有显著性意义（P＜0．05）内外融合比值为2．7－2．3：1,结论：①Ⅱ纵融合与Ⅲ级融合两者的概念不同、内涵不同。②应用R．DS．S测定融合范围本质上就是测定Panums’融合区。③立体视锐度越大,融合范围越大,④提出假说：Panum’s融合区不仅包括静态而且还包括动态,这对于拓宽五作融合功能研究的视野提供了较重要的理论依据。     

Coenzyme dependency of alcohol dehydrogenase in the retina of the rat. III. Effect of light-and dark adaptation on the redox state of the pyridine nucleotides

The levels of the oxidized and reduced forms of NAD and NADP have been determined in the rat's retina following dark- and light-adaptation, to clarify further their roles in vision.The lack of a significant increase in the oxidized form makes it difficult to implicate either coenzyme in the visual cycle. However, in view of the previous results reported by this laboratory and others, it is felt that NADP may yet have a special role. There is little doubt that the present investigation can only stimulate further studies on this complex and exciting problem.     

Contrast sensitivity in children

We have used a spatial two-alternative, forced-choice staircase technique to measure contrast sensitivities for sinusoidally modulated gratings. Subjects, all of whom were untrained observers, consisted of children of ages 2–16 yr and adults. Our testing method was completely successful with children who were over 3.5 yr but failed with those below 2.5 yr. Mean contrast sensitivities of the youngest group from which data were obtained (2.5–4.5 yr) were 0.35 log units lower than those of adults. However, there was very little difference between these two groups in the middle range of spatial frequencies tested. A gradual increase with age of contrast sensitivities was found up to about 8 yr. This change is probably due to a combination of neural development and non-visual factors.     

Astigmatic visual deprivation in cat: Behavioral,optical and retinophysiological consequences

Kittens were deprived of clear vision in one eye only by +7D or ?7D cylindrical lenses worn from eye opening until 7.5 months of age. Behavioral measurements subsequently demonstrated diminished acuity through the affected eye relative to the opposite control eye. However, single unit recordings at 3.5 years of age from retinal ganglion cells located within 1–11° of the centre of the area centralis showed neither loss of grating resolution nor any abnormal orientation bias. Furthermore, the astigmatic rearing had minimal effect on the development of the cat's natural optics to the emmetropic state. The experiments indicate that the amblyopic defect induced by the cylindrical lenses occurs in the brain rather than the eye.     

silent periodic cells in the cat striate cortex

A class of neurons called silent periodic cells, having properties intermediate between those in the simple and complex families, has been discriminated in the cat striate cortex. Silent periodic cells have relatively small receptive fields, a low spontaneous activity (i.e. relatively silent) and a preference for relatively slow stimulus velocities (< 3° /sec). In addition they give a mixed on/off response to a stationary flashing bar over virtually the whole of the receptive field with usually somewhat stronger on responses in some locations and stronger off responses in others (partial phase sensitivity). The most characteristic properties of these cells are, however, found in their responses to gratings, namely the nonlinearity manifested by the absence of a null point to a stationary flashing grating, a spatial periodicity revealed by a clearly modulated discharge to drifting gratings of medium and high spatial frequencies and, finally, a very sharp spatial frequency tuning curve with a half-sensitivity bandwidth between 0.5 and 0.95 octave, i.e. narrower than that of simple cells whose bandwidths are usually above 1 octave. Silent periodic cells resemble B-cells that have been described in other studies.     

Influence of stimulus parameters on visual sensitivity during saccadic eye movement

Visual threshold for stroboscope test flashes was measured during saccadic eye movements over various backgrounds and compared with measures obtained during eye fixation when the same backgrounds were “saccadically” displaced. Amount and time course of threshold change in the two situations compared well, suggesting no necessity for corollary discharge or other oculomotor interference with primary visual processes during eye movement. No significant threshold rise took place during saccades in the dark. Diffuse test flashes and small well focused flashes were affected differently by specific background conditions. Diffuse flashes were perceived with more difficulty during a saccade over a contour-free background than well focused, punctate stimuli. On the other hand, contours in the background raised saccadic thresholds for small stimuli much more than for diffuse test flashes. All threshold changes occurring during saccades were accentuated by increasing the background luminance.     

Intensity discrimination capacity of retinal ganglion cells of a tree shrew ( Tupaia chinensis)

Responses of single retinal on-centre ganglion cells were recorded in order to study the intensity discrimination threshold behaviour. A Poisson distribution fitted pulse number distributions of the spikes in the burst evoked by short duration stimuli presented within the receptive field centre of sustained units. A normal distribution was found for transient units. The dependence of the mean, standard deviation and regularity of the pulse number distribution on stimulus intensity mimicked the behaviour of the statistical parameters of the maintained activity as a function of background intensity. The transient cells displayed statistical characteristics which are found also in psychophysical studies. These cells, therefore, are assumed to be mainly involved in intensity discrimination.The dynamic range of ganglion cells in response to short duration stimuli is relatively narrow, 1 log unit, so the Weber law which is valid over many log units cannot be explained with the single-channel detection model. A multichannel energy summation model yields a threshold curve that closely resembles psychophysically measured curves.The psychophysical dependency of the discrimination threshold on background intensity level as investigated by Thijssen and Vendrik (1971) could be explained from the responses of both types of cells.     

Coenzyme dependency of alcohol dehydrogenase in the retina of the rat. IV. Retinol dehydrogenase (RDH) activity in the developing normal and retinitis rat retina, and the effect on enzyme activity of increasing concentrations of NAD or NADP

Retinol dehydrogenase activity has been determined in the developing normal, and retinitis, rat retina, using NAD and NADP as the coenzymes. Under the experimental conditions employed NADP increases RDH activity almost three-fold compared to NAD. Both types of retina reach peak activity around 3 weeks after birth. Thereafter enzyme activity falls off, particularly in the retinitis retina, the decrease being more marked when NADP is the enzyme. More importantly it has been shown that a quadrupling of NAD in the assay system increases RDH activity to NADP levels. The implications of these findings and their possible roles in vision are discussed.     

Effects of reference lines on displacement thresholds at various durations of movement

Displacement thresholds were determined for durations of movement between 10 msec and 2.5 sec, with and without the presence of a reference line. For all durations of movement, displacement thresholds were lower when a reference line was present. The magnitude of this effect was essentially constant across all durations of movement. These data suggest that previous reports of differential effects of reference lines on long and short durations of movement depend upon the stimulus paradigm employed.     

THE DIFFUSION OF OPHTHALMIC LASER IN AUSTRALIA*

This paper demonstrates the diffusion of ophthalmic laser into the Australian health care system. Australian ophthalmologists were quick to adopt the use of laser. Argon laser was introduced three years after its first use in the USA; YAG laser the same year as its use in the USA and Dye laser two years after its introduction in the USA. In the years 1975-84 there had been a gradual introduction of laser into ophthalmic practice growing from three to 39 in that period. From the end of 1984 to June 1986 the number increased by 68, an increase so sharp as almost to defy the classical S curve. The rapid rise can be attributed to its increased use in diabetic retinopathy, retinal vascular disease, senile macular degeneration, glaucoma and to perforate thickened posterior capsules.