Much has been written on the theory that congenital blindness might protect against schizophrenia, but proof remains elusive. It has been suggested that visual ability might be associated with schizophrenia in a bell-shaped distribution, with both lifelong absent and perfect vision being protective. Alternatively, ocular aberrations and schizophrenia may share an aetiology. Any neuronal pathology implicated in schizophrenia could affect the retina, since it is an embryological extension of the brain. The retina is more amenable to direct imaging than other parts of the central nervous system and may give unique insights into schizophrenia-associated neuropathology. It is also possible that psychosis causes visual impairment: people with psychotic illnesses are probably not accessing optical care optimally and have higher levels of risk factors for visual loss.

It has been shown that the visual acuity loss experienced by the deprived eye of kittens following an early period of monocular deprivation (MD) can be alleviated rapidly following 10 days of complete darkness when imposed even as late as 14 weeks of age. To examine whether 10 days of darkness conferred benefits at any age, we measured the extent of recovery of the visual acuity of the deprived eye following the darkness imposed on adult cats that had received the same early period of MD as used in prior experiments conducted on kittens. Parallel studies conducted on different animals examined the extent to which darkness changed the magnitude of the MD-induced laminar differences of the cell soma size and immunoreactivity for the neurofilament (NF) protein in the dorsal lateral geniculate nucleus (dLGN). The results indicated that 10 days of darkness imposed at one year of age neither alleviated the acuity loss of the deprived eye induced by an earlier period of MD nor did it decrease the concurrent lamina differences of the soma size or NF loss in the dLGN.

Objectives: To compare the recently used phacoemulsification systems using a health technology assessment (HTA) model.

Methods: A self-administered questionnaire, which included questions to gauge on the opinions of the recently used phacoemulsification systems, was distributed to the chief cataract surgeons in the departments of ophthalmology of eighteen tertiary hospitals in Shanghai, China. A series of senile cataract patients undergoing phacoemulsification surgery were enrolled in the study. The surgical results and the average costs related to their surgeries were all recorded and compared for the recently used phacoemulsification systems.

Results: The four phacoemulsification systems currently used in Shanghai are the Infiniti Vision, Centurion Vision, WhiteStar Signature, and Stellaris Vision Enhancement systems. All of the doctors confirmed that the systems they used would help cataract patients recover vision. A total of 150 cataract patients who underwent phacoemulsification surgery were enrolled in the present study. A significant difference was found among the four groups in cumulative dissipated energy, with the lowest value found in the Centurion group. No serious complications were observed and a positive trend in visual acuity was found in all four groups after cataract surgery. The highest total cost of surgery was associated with procedures conducted using the Centurion Vision system, and significant differences between systems were mainly because of the cost of the consumables used in the different surgeries.

Conclusions: This HTA comparison of four recently used phacoemulsification systems found that each of system offers a satisfactory vision recovery outcome, but differs in surgical efficacy and costs.

The objective of the study was to examine whether a nutritional antioxidant supplementation could improve visual function in healthy dogs as measured by electroretinography (ERG) and autorefraction. A total of twelve Beagles, 6 to 8 years of age, with normal eyes upon indirect ophthalmoscopy and slit lamp biomicroscopy, were age and sex matched and randomly assigned to receive a feeding regimen for 6 months with or without a daily antioxidant supplementation. Portable, mini-Ganzfeld ERG and a Welch Allyn hand-held autorefractor were used to test retinal response and refractive error in the dogs at baseline and at the end of the supplementation period. All ERG a-wave amplitudes obtained were increased in the treatment group compared with those of dogs in the control group, with significant improvements in the scotopic high and photopic single flash cone ERG responses (P < 0·05 for both). For the b-wave amplitudes, all responses were similarly increased, with significant improvements in responses for the scotopic high light intensity stimulation (P < 0·05), and for photopic single flash cone and 30 Hz flicker (P < 0·01 for both) recordings. Change in refractive error was significantly less in the treatment group compared with that of the control group during the 6-month study (P < 0·05). Compared with the control group, the antioxidant-supplemented group showed improvement to varying degrees for retinal function and significantly less decline in refractive error. Dogs, like humans, experience retinal and lens functional decline with age. Antioxidant supplementation as demonstrated may be beneficial and effective in the long-term preservation and improvement of various functions of the canine eye.

Visual functioning at various retinal illuminance levels is usually measured either by determining grating acuity as a function of light level or by determining how sensitivity to sine-wave gratings changes with retinal illuminance. The former line of research has shown that grating acuity follows a two-branch relationship with retinal illuminance, with the point of discontinuity occurring at the transition from scotopic to photopic vision. Results of the latter line of research have summarily been described as a transition from the DeVries-Rose law to Weber's law, according to which log sensitivity increases linearly with log illuminance with a slope of 0.5 over a range of low illuminances (the DeVries-Rose range) and then levels off and does not increase with further increases of illuminance (the Weber range). This paper aims at determining the compatibility of the results of these two lines of research. We consider empirical constraints from data bearing on the shape of the surface describing contrast sensitivity to sine-wave gratings as a function of spatial frequency and illuminance simultaneously, in order to determine whether they are consistent with a summary description in terms of DeVries-Rose and Weber's laws. Our analysis indicates that, with sine-wave gratings, the DeVries-Rose law can only hold empirically at low spatial frequencies.

Albinism alters the neural projections of the visual system. The authors wondered how this would affect visual function in rodents. They had previously shown that it doesn't alter the luminance threshold. They now explore visual acuity in the albino rat. In this work, they describe its contrast sensitivity function (CSF), as determined electro-physiologically. They recorded cortical visual evoked potentials (VEP) on six albino rats, stimulated by sinusoidal contrast reversal gratings. The curve showed the same characteristics that this function has in other mammals. Compared with the pigmented rat, the albino reached lower sensitivity values and showed a loss of sensitivity at high spatial frequencies. The estimated cut-off was 0.48 c/°, that is, 0.72 log units below the estimated cut-off for the pigmented rat under similar experimental conditions. VEP and behavioral cut-off were very close, the VEP estimation being slightly higher than the behavioral one.

The aim of this review is to evaluate the effects of omega-3 long chain polyunsaturated fatty acids (n-3 LCPUFA) supplementation in pregnant and lactating women and infants during postnatal life, on the visual acuity, psychomotor development, mental performance and growth of infants and children. Eighteen publications (11 sets of randomized control clinical trial [RCTs]) assessed the effects of the n-3 LCPUFA supplementation during pregnancy on neurodevelopment and growth, in the same subjects at different time points; 4 publications (2 data sets from RCTs) addressed physiological responses to n-3 LCPUFA supplementation during pregnancy & lactation and 5 publications (3 data sets from RCTs) exclusively during lactation. Some of these studies showed beneficial effects of docosahexaenoic acid (DHA) supplementation during pregnancy and/or lactation especially on visual acuity outcomes and some on long-term neurodevelopment; a few, showed positive effects on growth. There were also 15 RCTs involving term infants who received infant formula supplemented with DHA, which met our selection criteria. Many of these studies claimed a beneficial effect of such supplementation on visual, neural, or developmental outcomes and no effects on growth. Although new well designed and conducted studies are being published, evidence from RCTs does not demonstrate still a clear and consistent benefit of n-3 LCPUFA supplementation during pregnancy and/or lactation on term infants growth, neurodevelopment and visual acuity. These results should be interpreted with caution due to methodological limitations of the included studies.

Visual-evoked potentials (VEPs) were recorded from the surface of the optic tectum of the freshwater turtle, Pseudemys scripta elegans, in response to phase reversal of square-wave gratings of different spatial frequency and contrast. The refractive state of a group of 12 turtles in air was assessed from VEPs by placing trial lenses in front of the eye. The group mean refraction did not differ significantly from emmetropia, as compared to 4.8 diopters of hyperopia when refracted retinoscopically. The difference was explained by the retinoscopic reflex originating from the interface between vitreous humor and retina. Peak VEP amplitude was approximately linear with log grating contrast; extrapolation to zero VEP amplitude yielded contrast thresholds as low as 1%. High spatial-frequency cutoffs ranged from 4.4–9.9 cycle/deg in different animals, the highest values corresponding to the intercone spacing in the area centralis and to behavioral measures of acuity in a related species.

The effects of bilateral lesions of the centrifugal visual system (CVS) on the visual-discrimination capacity were studied in pigeons. Three different behavioral experiments, each testing different aspects of visual analysis, were performed. In the first two experiments, a grain-grit discrimination task and a visual-acuity determination, stimuli were presented in the frontal binocular visual field. A third experiment investigated the early detection of slow moving objects, introduced into the monocular lateral visual field. After bilateral lesions in the nucleus isthmo-opticus (ION) and in the ectopic nucleus isthmo-opticus (EION), a multiple linear regression analysis was employed to correlate the postoperative performance in all three tasks with the amount of structure loss within ION and EION. Deficits in the grain-grit discrimination procedure were a function of the ION lesion extent and did not depend on EION damage. Thus, these two structures could be functionally differentiated for the first time. Neither the ION nor the EION seems to be involved in visual- acuity performance or the early detection of large shadows moving forward through the visual field. Our data support the hypothesis that the CVS is involved in pecking and food selection among static stimuli at a short viewing distance in ground-feeding birds such as pigeons and chickens.

The aim of this project was to investigate the interaction between Y retinal ganglion cells and the cells of the dorsal lateral geniculate nucleus (LGNd) of the cat, with particular reference to center-surround antagonism and intrageniculate inhibition. Responses of cells in the LGNd were studied by stimulating the retina with spots of light of constant contrast but varying size. The peak discharges of nonlagged X (XN) cells were strongly suppressed with increase in spot size but the responses of lagged X (XL) cells and nonlagged Y (YN) cells were inhibited much less strongly. The effect of the Y system on these responses was examined by producing a selective block of conduction in Y fibers in one optic nerve by means of a pressure cuff (Y-blocking). These effects were assessed by measuring the peak discharge rates and by calculation of a “peak suppression index.” Y-blocking had no significant effect on the peak suppression index of XL, cells in either lamina or on YN cells in the normal (not Y-blocked) lamina but had significant effects on the responses of XN cells, causing a decrease in peak suppression index, both for cells in laminae receiving their principal excitatory input from the Y-blocked eye (both lamina A and lamina A1 ) as well as those in lamina A (but not lamina A1 ) receiving their excitatory input from the normal eye. These effects were obtained with relatively large spots of light. Thus Y optic fibers have both intralaminar (monocular) and interlaminar (binocular) inhibitory effects on XN cells. In addition to these suppressive effects, the experiments also show that ipsilaterally projecting Y fibers have facilitatory effects on XN cells in lamina A when small spots of light, about optimal size for the XN cell, are used. These results suggest that the Y system plays a powerful role in shaping the responses of XN cells, possibly enhancing visual acuity.

Evidence from several sources indicates that the photoreceptors of rabbit retina include rods, green cones and blue cones, and that blue-green color opponency occurs in select retinal ganglion cells. One of us (Famiglietti) has identified wide-field cone bipolar cells as probable blue-cone-selective bipolars, and type C horizontal cells as possibly connected to blue cones. We wished to extend the analysis of blue cone pathways in rabbit retina and to characterize the topographic distribution of blue and green cones. Two monoclonal antibodies raised against chicken visual pigments are reported to label medium- and long-wavelength cones (COS-1) and short-wavelength cones (OS-2) in all mammalian retinas studied thus far (Szél and colleagues). Using selective labeling with these two antibodies and a nonselective method in nasal and temporal halves of the same retinas, we have found that densities of photoreceptors vary systematically, depending upon the size of the eye and age of the animal. In ‘standard’ New Zealand rabbits of 2–3 kg (2–3 months old), rods reached a peak density of about 300,000/mm2 just dorsal to the visual streak, while cones exhibit peak density at mid-visual streak of about 18,000/mm2. Published measurements of visual acuity in rabbit are less than predicted by this calculation. The ratio of cones to rods is significantly higher in ventral retina, where the density of cones declines to a plateau of 10,000–12,000/mm2, when compared to dorsal retina, where cones are uniformly distributed at a density of about 7000/mm2. The density of OS-2 labeled (presumably “blue”) cones is uniformly low, 1000–1500/mm2, in a wide expanse that includes dorsal retina, the visual streak, and much of ventral retina, except for a region of higher density along the vertical midline. We confirm that there is a far ventral horizontal region near the perimeter that is populated exclusively by a high density (about 13,000/mm2) of OS-2-positive cones (Juliusson and colleagues). This region does not extend to the ventral retinal margin, however, where cone density drops precipitously. Transitional zones between COS-1 and OS-2 labeling, in a region of relatively high and uniform cone density, where sums of COS-1 and OS-2 labeling are higher than expected and in which weakly and strongly labeled cones are intermixed, raise questions about the identities of the visual pigment epitopes, the possibility of double labeling, and therefore the possibility of dual expression of pigments in single cones. The “inverted- T -shaped” topography of higher density OS-2 labeling raises doubts about the significance of a ventral concentration of blue cones for visual function in rabbit retina.

We examined the grating acuity and contrast sensitivity of cats whose eye position was monitored with a scleral search-coil technique. During each trial, the cat was required to maintain fixation on a laser spot and respond to the presence or the absence of a grating by pressing a right or left pedal. With this procedure, acuity was measured along the horizontal and vertical meridian over a range of eccentricities in the nasal, temporal, superior, and inferior retina. In addition, contrast sensitivity for stationary and drifting gratings was measured for the temporal retina along the horizontal meridian. Acuity in area centralis reached about 3.5 cycle\deg and declined by 0.5 octaves at 4 deg and by about 1.3 octaves at 16-deg eccentricity in the nasal retina. The acuity was higher in the nasal than temporal retina. At all eccentricities, spatial resolution exceeded the resolution limit derived from Y (alpha)-cell properties. Contrast sensitivity also decreased as the eccentricity increased when the target size was held constant. The slope of sensitivity-eccentricity function was relatively shallow for a low spatial frequency (0.30 cycle\deg) with sensitivity decreasing by a factor of 1.5–2 at 8-deg eccentricity. The slope of the sensitivity falloff for high spatial-frequency gratings (1.2 cycle\deg) was steeper, with a 5–10-fold difference in sensitivity between 0 and 8 deg. By varying the target size, we determined that the summation area in the cat is about a factor of 3 smaller in area centralis than a 16-deg eccentricity. When the size of the centrally and peripherally viewed targets was scaled relative to visual acuity, the sensitivity was constant across the visual field.

We performed genome-wide chemical mutagenesis of C57BL/6J mice using N-ethyl-N-nitrosourea (ENU). Electroretinographic screening of the third generation offspring revealed two G3 individuals from one G1 family with a normal a-wave but lacking the b-wave that we named nob4. The mutation was transmitted with a recessive mode of inheritance and mapped to chromosome 11 in a region containing the Grm6 gene, which encodes a metabotropic glutamate receptor protein, mGluR6. Sequencing confirmed a single nucleotide substitution from T to C in the Grm6 gene. The mutation is predicted to result in substitution of Pro for Ser at position 185 within the extracellular, ligand-binding domain and oocytes expressing the homologous mutation in mGluR6 did not display robust glutamate-induced currents. Retinal mRNA levels for Grm6 were not significantly reduced, but no immunoreactivity for mGluR6 protein was found. Histological and fundus evaluations of nob4 showed normal retinal morphology. In contrast, the mutation has severe consequences for visual function. In nob4 mice, fewer retinal ganglion cells (RGCs) responded to the onset (ON) of a bright full field stimulus. When ON responses could be evoked, their onset was significantly delayed. Visual acuity and contrast sensitivity, measured with optomotor responses, were reduced under both photopic and scotopic conditions. This mutant will be useful because its phenotype is similar to that of human patients with congenital stationary night blindness and will provide a tool for understanding retinal circuitry and the role of ganglion cell encoding of visual information.