Eye For Use Research Articles

Histological assessment of the effect of 50mW red laser on retina at variable time intervals: animal model.

To assess the histopathological effect of 50milliWatt red laser pointer on mice retinal tissue at variable exposure times. The experimental study was conducted in the Postgraduate Laboratory of the Unit of Medical Physics, Department of Physiology, College of Medicine, Mustansiriyah University, Baghdad, Iraq, from November 2020 to April 2021, and comprised albino mice. Histopathological effects on the retinal tissues were evaluated microscopically using conventional haematoxylin and eosin stain just after being exposed to commercially available 50 milliWatt red laser pointers with 630nm wavelength at 1, 2 and 3 minutes, grouped as R1, R2 and R3, respectively. The laser beam was focussed on the right eye of the mice sedated with sodium pentobarbital, reserving the left eye for use as a control group. Data was analysed using SPSS 24. Of the 12 mice, 4(33.3%) were in each of the 3 groups. There was significantly destructive effect of red laser on retinal outer cellular layers in all the groups compared to the controls (p<0.05). The effect was significant between R1 and R2 (p=0.0001), and between R2 and R3 (p=0.02). The handheld commercial red laser pointers could harmfully affect a wide range of mice retina and choroid.

Intraocular Injection of HyStem Hydrogel Is Tolerated Well in the Rabbit Eye.

Purpose: To determine the long-term biocompatibility of HyStem® hydrogel in the rabbit eye for use as a carrier for cell or drug delivery into the ocular space. Methods: HyStem hydrogel formulation solidifies ∼20 min after reconstitution, thus can potentially form a solid deposit after injection in situ. To study the ocular disposition of fluorescein-labeled HyStem, we delivered 50 μL/eye over 1 min into the vitreous space of the rabbit. We used 3 Dutch-Belted and 3 New Zealand-pigmented rabbits, all females, delivered the gel into the right eyes, and injected 50 μL BSS Plus into the left eyes as a control. Retinal morphology was assessed by optical coherence tomography (OCT) and white light fundus photography. Fluorescence fundus photography enabled measurement of the clearance of the labeled hydrogel from the posterior chamber. Visual function was evaluated using flash and flicker electroretinography (ERG) pre- and postinjection and at weekly intervals thereafter for 6 weeks. Retinal immunohistochemistry for microglial inflammatory markers was carried out with antiglial fibrillary acidic protein (GFAP) antibody, isolectin B4 (IB4), and 4',6-diamidino-2-phenylindole (DAPI). Results: The gel was successfully delivered into the vitreous space without the formation of a discrete retinal deposit. Fundus imaging, OCT measurements of retinal thickness, and immunohistochemical data indicated an absence of retinal inflammation, and ERG indicated no impact on retinal function. The half-time of HyStem clearance calculated from the loss of fundus fluorescence was 3.9 days. Conclusions: HyStem hydrogel appears to be biocompatible in the ocular space of a large eye and safe for long-term intraocular application.

A Moth's Eye.

The article reports on the research of Shin-Tson Wu of the University of Central Florida on moth's eye and the silicon dioxide mold he and his colleagues, from the National Taiwan University, that resembles that of the moth's eye for use in producing glimpled and hard coating of flexible sheet.

Inversion of contrast polarity abolishes spontaneous preferences for face-like stimuli in newborn chicks

A spontaneous preference for face-like stimuli has been demonstrated in domestic chicks, similar to that shown by human newborns, suggesting evolutionary continuity across species. Inversion of contrast polarity of face-like stimuli abolishes face preferences in human newborns. Here we investigated the effects of contrast polarity inversion and brain lateralization in chicks’ preferences for faces. In Experiment 1 face-naïve chicks were tested with a negative face obtained from a stimulus that elicited preferential approach in previous research. As in human newborns, reversal of contrast polarity abolished face-preferences. Experiments 2, 3 and 5 investigated the effect of adding a pupil-like dot within the inner features of the negative and of positive stimuli (a manipulation that re-established face-preference in human newborns). Chicks reacted to this by avoiding the face stimulus. In Experiments 4 and 6 we found that the preference expressed by chicks having only their left eye (right hemisphere) in use changed according to contrast polarity, whereas it remained unaffected in chicks having their right eye in use. Thus, in domestic chicks, as in human beings, a stimulus is perceived as face-like only if it presents the correct luminance pattern expected for a face under natural top-lit illumination and the right hemisphere seems to play a crucial role in this kind of social orienting responses.

Asymmetry of visually guided sexual behaviour in adult Japanese quail (Coturnix japonica)

Sexually active adult Japanese quail (Coturnix coturnix japonica) were trained to run across either a left- or a right-turning runway to obtain sexual access to a conspecific of the opposite sex. The birds tested with only their right eye in use showed significantly higher latencies to complete the runway task than the birds tested binocularly and those using the left eye. In all of the three experimental conditions, male birds were significantly faster than their female counterparts. Generally, these findings are compatible with previous evidence for lateralisation in sexually motivated behaviour in birds. However, unlike the previous findings that suggested a loss of lateralisation in pattern discrimination in quail during adulthood, the present study shows that asymmetries in visually guided sexual behaviour persist in adult quail. Thus, our study implies that ontogenetic and lateralised changes within the visual system can be differently organised for different output pathways.

Notes on the Effect of Diabetes Mellitus on the Morphology and Function of the Rat Lacrimal Gland

Purpose. The development of dry eye therapies requires clinical trial designs to be well-controlled, precise, and reliable. To accomplish this, we must consider proper patient selection, clinically relevant endpoints, and reproducible / predictable study procedures. The Controlled Adverse Environment (CAE) is an established model that controls the many environmental conditions which can influence dry eye for use in the evaluation of dry eye therapeutic agents. The purpose of this paper is to review lessons learned from the thousands of patients who have been evaluated in the CAE. Methods. The CAE standardizes the study of dry eye by regulating humidity (<10%), temperature (76 ± 6 F), airflow (constant, non-turbulent), lighting conditions, and visual tasking (television or PC use). By integrating specific diagnostic equipment such as digital imaging, eye tracking and standardized scales, objective and subjective measures are recorded before, during, and after CAE exposure. This model provides a standard method of challenging all patient eyes equally. Results. After reviewing patient responses in the CAE model, a number of observations have been documented. For example, it has been shown that a patient either exhibit signs only, symptoms only, or both signs and symptoms during exposure to adverse environmental conditions. Compensatory mechanisms such as the ability to reflex tear and blink when the ocular surface is challenged can vary according to the severity and cause of dry eye. Certain endpoints like keratitis, conjunctival redness, tear film stability, fluorophotometry, osmolarity, and the Ocular Protection Index (OPI) are modifiable by environmental conditions while others are not. The effects of influential factors such as age, sex, neural regulation, menopause, and systemic medications known to cause ocular drying have also been investigated in this model. Conclusions. With the use of standardized tools such as the CAE, we are able to maintain an empirical approach towards understanding the various underlying mechanisms of dry eye and evaluating future treatments for this disease.

Visual lateralisation in quails (Coturnix coturnix)

Two-week-old quails (Coturnix coturnix) were trained to discriminate food grains scattered randomly on a background of small pebbles of similar size adhering to the floor and differing from the grains in texture and hue (“pebble floor task”). Quails tested binocularly or with only their right eye in use showed less pecking to the pebbles and more pecking to the grains than quails tested with only their left eye in use. Adult quails in contrast did not show lateralisation. These findings add to previous evidence for visual lateralisation in birds in the pebble floor task suggesting that neural structures fed by the right eye, mainly located to the left hemisphere, are better suited to rapid visual categorisation of food objects. Like other galliformes species such as the domestic chick (Gallus gallus), but unlike non-galliformes species such as the pigeon, behavioural lateralisation in the pebble floor task may be associated with transitory anatomical asymmetries in the thalamofugal visual pathway.

Creating cataract in a pig eye

The purpose of this study was to create a uniform, reproducible hardened lens nucleus and an anterior capsule in a pig eye that approximate those in the human eye for use in cataract surgery training. the lens nuclei was hardened and anterior capsule elasticity was reduced in pig eyes by injecting the lens with mixtures of formalin and alcohol (ethanol, 2-propanol, or both). a 30 gauge needle was used to pierce the lens 3.0 mm from the limbus. then, 0.2 ml of the formalin and alcohol mixture was injected. the most effective mixture was formalin, ethanol, and 2-propanol in the ratio 4:3:3. Fifteen minutes after this mixture was injected, the pig eye had nuclear cataract with grade III hardness and an anterior capsule that approximated the capsule in a human cataractous eye. The cataract created by this method will be useful in teaching continuous curvilinear capsulorhexis, divide and conquer and phaco chop phacoemulsification, and nuclear hydrodelineation and rotation.

Footedness in Binocular and Monocular Chicks

The first foot used during bouts of ground scratching in 16-day-old chicks searching for food in the floor of an arena covered with sawdust was recorded in animals with normal binocular vision and in animals with an eye temporarily occluded by an eye-patch. Binocular chicks showed a significant right foot bias, whereas monocular chicks tended to use the foot contralateral to the eye in use. Data for monocular chicks thus suggest that the activated hemisphere (contralateral to the eye in use) is the one that takes control of posture, leaving to the other hemisphere reflex-like responses associated with ground scratching or body wiping. It is argued that footedness in chicks might have arisen from the limb that is used to maintain postural and positional control, rather than from the limb that is used during motor activities.

Evaluation of the International Standards Organisation/Draft International Standard model eye for use with automated infra-red optometers

A recent Draft International Standard describes a method for establishing the accuracy of automated infra-red optometers, using model eyes. In the present study we evaluate the performance of a series of automated infra-red optometers using model eyes constructed to the specifications of the Draft International Standard. The results demonstrate systematic differences between the values predicted by calculation from the standard and those found by measurement. These differences were reduced but not eliminated when the effects of non-paraxial refraction through the limiting aperture of the model eyes was taken into account. We conclude that the formula used to predict values of refractive power from the Draft International Standard is inappropriate because it fails to account for higher order aberrations.

Color character recognition method based on human perception

Color is one of the most powerful and important types of visual information in various fields such as image processing, electronic imaging, and robot vision technologies. A new color character recognition system, composed of a camera, optical filters, an image board, a neuro board, and a micro computer was constructed. Using typewriter characters and backgrounds in five colors, two kinds of experiments were performed. The first consisted of preliminary experiments testing the effectiveness ofthe modified opponent-colortheory ofthe human eye for use in machine character recognition. The second was an experiment in color character recognition, in which the system recognized both characters and their colors.

Right hemisphere advantage for social recognition in the chick

Recognition of familiar and unfamiliar conspecifics was studied in pair-reared chicks tested binocularly or with only one eye in use. Chicks were tested on day 3 in pairs composed of either cagemates or strangers. Social discrimination, as measured by the ratio “number of pecks at the strangers/total number of pecks” was impaired in right-eyed chicks with respect to left-eyed and binocular chicks. Male chicks showed higher levels of social pecking than females, and chicks that used both eyes showed higher pecking than monocular chicks. There were no significant differences in the total number of pecks (i.e. pecks at companions plus pecks at strangers) between right- and left-eyed chicks: the impairment in social discrimination of right-eyed chicks seemed to be due partly to a reduction in pecking at strangers and partly to an increase in pecking at companions. It is suggested that neural structures fed by the left eye (mainly located at the right hemisphere) are better at processing and/or storing of visual information which allows recognition of individual conspecifics. This may be part of a wider tendency to respond to small changes in any of a variety of intrinsic stimulus properties.

A model of the eye for use in medical education

A model simulating the operation of the human eye has been constructed for use in a practical medical physics course. The following experiments carried out with the aid of this model are described: (i) Refractive power measurements to determine whether the eye is myopic or hypermetropic, calculation of the refractive power of the lens needed to correct this condition if present and testing of the lens prescribed in this way. (ii) Accommodation measurements. (iii) Simulation of the surgical removal of the crystalline lens of the eye which is often necessary in the treatment of cataract, and calculation of: (a) the power of the lens to be implanted in the eye to correct this aphakia, or (b) the power of the lens needed to correct the aphakia if no lens is implanted; and testing of the prescribed lenses. (iv) Demonstration of the effect of pupil diameter on depth of focus. (v) Demonstration of the influence of ocular opacity-caused e.g. by cataract-on the sharpness of the image on the retina.