Search

Clinical relevance: Caffeine intake has been demonstrated to influence several physiological measures, including some related to eye physiology. The ability to focus at different distances is of paramount importance in real-world situations, and thus, the possible impact of caffeine intake on accommodative facility may have important clinical implications. Background: This placebo-controlled, double-blind, balanced crossover study aimed to assess the acute effects of caffeine ingestion on the frequency and precision of the binocular accommodative facility. Methods: Twenty university students (21.9 ± 3.4 years) ingested a capsule of caffeine (4 mg/kg) or placebo (300 mg of corn-starch) on two different days and counterbalanced order. The binocular accommodative facility was objectively assessed, using the WAM-5500 binocular open-field autorefractometer, after 60 min of capsule ingestion (caffeine/placebo). Perceived levels of activation was also assessed in each experimental condition. Results: The ingestion of a single administration of caffeine (~ 4 mg/kg) causes an increase in the number of cycles performed per minute (p = 0.023, Cohen’s d = 0.55), whereas no effects were observed for the mean magnitude of accommodative change between the far and near targets (p = 0.794), and the percentage of incorrect cycles of accommodation and dis-accommodation (p = 0.271 and 0.396, respectively). Participants reported a perceived level of activation of 6.8 ± 1.5 and 7.6 ± 1.8 in the placebo and caffeine conditions, respectively (p = 0.059). Conclusion: Caffeine intake improves quantitative, but not qualitative, measures of accommodative facility. These results corroborate the impact of caffeine on visual function and suggest that this ergogenic effect of caffeine may be used to enhance visual performance in applied situations.

PurposeTo establish the optimum grading increment which ensured parity between practitioners while maximising clinical precision.MethodsSecond year optometry students (n = 127, 19.5 ± 1.4 years, 55 % female) and qualified eye care practitioners (n = 61, 40.2 ± 14.8 years, 52 % female) had 30 s to grade each of bulbar, limbal and palpebral hyperaemia of the upper lid of 4 patients imaged live with a digital slit lamp under 16× magnification, diffuse illumination, with the image projected on a screen. The patients were presented in a randomised sequence 3 times in succession, during which the graders used the Efron printed grading scale once to the nearest 0.1 increment, once to nearest 0.5 increment and once to the nearest integer grade in a randomised order. Graders were masked to their previous responses.ResultsFor most grading conditions less than 20 % of clinicians showed a ≤0.1 difference in grade from the mean. In contrast, more than 50 % of the student graders and 40 % of experienced graders showed a difference in grade from the mean within 0.5 for all conditions under measurement. Student precision in grading was better with both 0.1 and 0.5 grading increments than grading to the nearest unit, except for limbal hyperaemia where they performed more accurately with 0.5 unit increment grading. Limbal grading precision was not affected by grading step increment for experienced practitioners, but 0.1 and 0.5 grading increments were both better than the 1.0 grading increment for bulbar hyperaemia and the 0.1 grading increment was better than the 0.5 grading increment and both were better than the 1.0 grading increment for palpebral hyperaemia.ConclusionAlthough narrower interval scales maximise the ability to detect smaller clinical changes, the grading increment should not exceed one standard deviation of the discrepancy between measurements. Therefore, 0.5 grading increments are recommended for subjective anterior eye physiology grading (limbal, bulbar and palpebral redness).

Aqueous humor outflow (AHO) is important for supporting normal eye physiology and vision. Altered AHO occurs in glaucoma because increased AHO resistance leads to increased intraocular pressure (IOP). This increased resistance occurs at the trabecular meshwork (TM) and distal to the TM. Soluble factors such as transforming growth factor beta (TGF-β) have been implicated in this process. Numerous tools are available to structurally or functionally study AHO that are either static or real-time in nature. These methods have been instrumental to better understanding normal AHO and unveiling the pathophysiology of diseased AHO in glaucoma.

The presence of myocilin is often used in the process of validating trabecular meshwork (TM) cells and eye tissues, but the antibody reagents used for detection are poorly characterized. Indeed, for over a century, researchers have been using antibodies to track proteins of interest in a variety of biological contexts, but many antibodies remain ill-defined at the molecular level and in their target epitope. Such issues have prompted efforts from major funding agencies to validate reagents and combat reproducibility issues across biomedical sciences. Here we characterize the epitopes recognized by four commercial myocilin antibodies, aided by structurally and biochemically characterized myocilin fragments. All four antibodies recognize enriched myocilin secreted from human TM cell media. The detection of myocilin fragments by ELISA and Western blot reveal a variety of epitopes across the myocilin polypeptide chain. A more precise understanding of myocilin antibody targets, including conformational specificity, should aid the community in standardizing protocols across laboratories and in turn, lead to a better understanding of eye physiology and disease.

PURPOSE: To assess the relationship between short-term and long-term changes in power at different corneal locations relative to the change in central corneal power and the 2-year change in axial elongation relative to baseline in children fitted with orthokeratology contact lenses (OK). METHODS: Thirty-one white European subjects 6 to 12 years of age and with myopia -0.75 to -4.00 DS and astigmatism ≤1.00 DC were fitted with OK. Differences in refractive power 3 and 24 months post-OK in comparison with baseline and relative to the change in central corneal power were determined from corneal topography data in eight different corneal regions (i.e., N[nasal]1, N2, T[temporal]1, T2, I[inferior]1, I2, S[superior]1, S2), and correlated with OK-induced axial length changes at two years relative to baseline. RESULTS: After 2 years of OK lens wear, axial length increased by 0.48±0.18 mm (P0.05). CONCLUSION: The reduction in central corneal power and relative increase in paracentral and pericentral power induced by OK over 2 years were not significantly correlated with concurrent changes in axial length of white European children. Sin financiación 2.386 JCR (2018) Q2, 21/60 Ophthalmology 0.824 SJR (2018) Q2, 38/126 Ophthalmology, 758/2844 Medicine (miscellaneous) No data IDR 2018 UEM

Currently, there are many types of virtual displays and new types arise every year. However, their vast majority appear technically inapplicable because they are inconsistent with a number of key factors related to the eye physiology. In this paper, we present the general requirements for optical systems of virtual displays, taking into account human eye physiology.

Mud crabs use their eyes function to guide their movement activities i.e., to avoid predator and to support their environment orientation. In tropical environment such as Indonesia, mud crabs live in mangrove area as their habitat. To support their visual acuity, mud crabs depend on the number of con sell as photoreceptor and carapace width. The purpose of this study is to prove whether mud crab eye physiology is different between life stages (juvenile, sub-adult and adult stadia) especially in Semarang territorial water. Histology methods were used to determine the density of cone cell on three life stages. The highest number of eye cell in juvenile, sub-adult and adult are 25, 15 and 13 units, respectively and found in frontal inner side. The visual acuity in juvenile is 6.005×10-3-7.46×10-3; sub-adult is 9.17×10-3-15.4×10-3; and the adult is 16.03×10-3-19.6×10-3. The results indicate that the increase of visual acuity follows the growth of carapace width in mud crabs.

In monozygotic twins two embryos are formed from a single fertilized egg. In "mirror image twins" identical siblings have reverse asymmetric features in the right and left sides of the body. We report the case of twins with mirror-image hypermetropic anisometropia. They were referred to an ophthalmologist at the age of 3.5 years for amblyopia. Cycloplegic refraction of twin 1 was +1.00 in the right eye and +4.50 -0.75 ×180 in the left eye; of twin 2, +4.75 -1.00 ×180 and +1.25. Keratometry and axial length were measured with Lenstar LS 900 when the twins were 6 years of age. In twin 1, the axial length was 22.18 mm in the right eye and 20.97 in the left eye; in twin 2, 20.94 mm and 22.13. Keratomtry of both eyes of these twins was relatively equal.

PURPOSE To explore the characteristics of choroidal thickness (ChT) in Chinese children. METHODS A total of 144 healthy children, aged 6 years to 12 years old, were enrolled in the study. The ChT of subfovea and peripheral locations 0.5, 1.5, and 2.5 mm away from the fovea were evaluated by enhanced depth imaging optical coherence tomography. The association between subfoveal ChT and systemic, as well as ocular factors, including age, sex, height, weight, body mass index, axial length, refractive error, intraocular pressure, preterm history, and the refractive status of parents were studied. RESULTS The mean subfoveal ChT was 302 ± 63 μm. In the nasal, superior, and inferior areas, the ChT of locations closer to the fovea was thicker than those farther away from the fovea (all P < 0.05); however, ChT was not significantly different among different locations in the temporal area (P = 0.16). The ChT of the nasal quadrant was significantly thinner than that of other areas (P < 0.01). Subfoveal ChT decreased with age, axial length, preterm history, and increased with height. Sex was not statistically associated with subfoveal ChT. CONCLUSION In Chinese children, the ChT is thinnest in the nasal quadrant and thicker in central regions than in peripheral areas. The subfoveal ChT independently decreases with age, axial length, preterm history, and increases with height.

Eye irritation, for example dry or irritated eyes, is generally among top three reported symptoms in office-like environments, in particular among workplaces with cognitive demanding visual display unit (VDU) work. The symptoms are especially among middle and advanced ages and particularly among women more than men. The symptoms are also among the most commonly reported complaints in the eye clinic. To be in a position to interpret the high prevalence of eye symptoms, a multidisciplinary and integrated approach is necessary that involves the external eye physiology (separate from internal eye effects), eye diseases (evaporative dry eye (DE), aqueous-deficient DE, and gland dysfunctions), and risk factors that aggravate the stability of precorneal tear film (PTF) resulting in hyperosmolarity and initiation of inflammatory reactions. Indoor environmental, occupational and personal risk factors may aggravate the PTF stability; factors such as age, contact lenses, cosmetics, diet, draft, gender, low humidity and high temperature, medication, outdoor and combustion pollutants, and VDU work. Psychological stressors may further influence the reporting behavior of eye symptoms. The impact of the risk factors may occur in a combined and exacerbating manner.

This study compared the axial length (AL), central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), mean anterior corneal radius of curvature (Rm), and postoperative refractive outcomes obtained from two different swept-source optical coherence biometers, the ARGOS (Movu, Aichi, Japan), which uses the segmental refractive index for each segment, and the IOLMaster 700 (Carl Zeiss Meditec, Jena, Germany), which uses an equivalent refractive index for the entire eye. One hundred and six eyes of 106 patients with cataracts were included. The refractive outcomes using the Barrett Universal II, Haigis, Hoffer Q, and SRK/T formulas were evaluated. The mean AL, CCT, ACD, and Rm differed significantly (P 0.05). The accuracy of the intraocular lens power calculations was clinically acceptable with both biometers, although the ocular biometry using these two biometers exhibited certain differences.

EnglishMorphology and physiology of bird eyes are similar to mammals; although, there are peculiarities that should be considered for a correct interpretation of an ophthalmic examination. While the ophthalmology of domestic species is already well established, there are gaps to be filled regarding birds, particularly due to the large number of existing species. This literature review consists of a brief contribution regarding peculiarities of anatomy, physiology, and ophthalmic semiotechnique of the avian eye. Key words: anatomy; eye physiology; intraocular pressure; ophthalmic examination; tear test; wild animals portuguesA morfologia e a fisiologia dos olhos das aves sao similares aquelas de mamiferos, mas existem particularidades que devem ser consideradas para a correta interpretacao do exame oftalmico. Enquanto a oftalmologia de especies domesticas ja e bem estabelecida, ainda ha diversas lacunas no que tange as aves, particularmente devido ao grande numero de especies existentes. Este trabalho objetiva realizar uma revisao bibliografica abrangendo anatomia, fisiologia e semiologia oftalmica de aves. Palavras-chave: animais selvagens; anatomia; exame oftalmico; fisiologia ocular; teste lacrimal; pressao intraocular

OBJECTIVES: Describe axial elongation using 14-year longitudinal data in a large, ethnically diverse group of myopic children, estimate age and axial length (AL) at stabilization and evaluate associations between the progression and stabilization of AL and myopia. METHODS: AL was measured by A-scan ultrasonography annually. AL data were fit with individual polynomial functions and curve-based parameters (AL at stabilization and age at stabilization when annual rate of axial elongation ≤0.06 mm) were estimated. For myopia progression, non-cycloplegic spherical equivalent refractions were fit with Gompertz functions. RESULTS: Four hundred thirty-one participants, with AL and myopia data fit successfully, were classified into four cohorts: Younger (n=30); Older (n=334); AL Stabilized at Baseline (n=19); AL Not Stabilized (n=48). At AL stabilization, participants in the Younger and Older Cohorts, mean (sd) age and AL were 16.3 (2.4) years and 25.2 (0.9) mm, respectively. No associations were found between age at AL stabilization and ethnicity, sex, or number of myopic parents. At stabilization, sex and number of myopic parents (both p< 0.003), but not ethnicity, were significantly associated with AL. AL and myopia progression curves were highly correlated overall (all r>0.77, p< 0.0001). However, unlike AL, the amount of myopia did not differ significantly between males and females. CONCLUSIONS: In the majority of participants, AL increased rapidly at younger ages and then slowed and stabilized. The close association between growth and stabilization of AL and myopia is consistent with the suggestion that axial elongation is the primary ocular component in myopia progression and stabilization.

Introduction Eye irritation is generally among top-3 reported symptoms in office environments. The symptoms are especially among middle and advanced ages and particularly among women more than men. The eye symptoms are the most commonly reported complaints in the eye clinic. A multidisciplinary understanding of potential risk factors is necessary to interpret the high prevalence of eye symptoms. Methods Literature from 2012 to June 2017 has been updated in context of dry eye (DE) symptom reporting in office-like environments by searches in the public databases and previous reviews. Results The overview reveals that the external eye physiology (separate from internal eye effects), eye diseases (evaporative dry eye, aqueous-deficient dry eye, and gland dysfunctions) aggravate the stability of precorneal tear film (PTF); this appears to cause hyperosmolarity and initiation of inflammatory reactions. Further, indoor environmental, occupational and personal risk factors may aggravate the PTF stability. These are, inter alia age, contact lenses, cosmetics, diet, draft, gender, low humidity and high temperature, medication, outdoor and combustion pollutants, and VDU work. Psychological stressors may further influence the reporting behaviour of symptoms. The risk factor impact may occur in a combined and exacerbating manner. Discussion Multifactorial causalities show two key indoor parameters, visually demanding tasks combined with low relative humidity. A substantial fraction of office workers may have unrecognised DE diseases which may further be exacerbated by environmental, occupational and personal risk factors. Dry eye-like related symptoms in office-like environments may be considered a subgroup of ‘dry eye’ disease. A number of other risk factors in the office environment are associated with reported DE symptoms. These may in combination exacerbate the symptom reporting. Except for combined events, indoor VOCs, formaldehyde, and acrolein are not expected to cause sensory-related eye symptoms in offices without aggravation of the PTF.

Purpose To investigate the relationship between lens power and age as well as the relationship between lens power and axial length (AL) in Chinese children and adolescents. Methods The participants underwent a comprehensive ophthalmic examination that included AL, cycloplegic refraction, and Pentacam measurements. The crystalline lens power was calculated using Bennett's formula and then compared among the children of different age groups, refractive statuses, and AL categories. The association of lens power and AL was analyzed using multiple regression. Results A total of 1992 children and adolescents aged 6- to 18-years old were included. The difference in lens power was greater before 10-years old, followed by a relatively smaller difference in children aged 10 to 14 years and the difference in lens power came to a near plateau in adolescents after 14-years old. The negative association between lens power and AL was found to be more evident in nonmyopes than in myopes irrespective of age (younger than 10 years: nonmyopes: β = -1.499, myopes: β = -0.872; older than 10 years: nonmyopes: β = -1.288, myopes: β = -0.390, all P < 0.001). Conclusions The lens power in children and adolescents aged 6 to 18 years exhibited three stages. The association between lens power and AL differed between the nonmyopes and myopes. These findings suggested that less reduction in lens power might be associated with both growing age and increasing AL in myopes.

The choroid provides the main blood supply to the eye and plays a key role in eye physiology. Different entities can compromise its structure and function, having a striking impact on vision. Knowing the histology of the normal eye is fundamental for the correct understanding of the pathologic processes. This chapter is therefore organized into pathological subcategories defined as congenital, inflammatory, and neoplastic processes. The correlation between these different entities and the histopathology would allow us to have the right interpretation of the interaction between the eye, the patient, and the disease, opening the field to different treatments and improving quality among health providers.

The results of many studies in a variety of species have significantly advanced our understanding of the role of visual experience and the mechanisms of postnatal eye growth, and the development of myopia. This paper surveys and reviews the major contributions that experimental studies using animal models have made to our thinking about emmetropization and development of myopia. These studies established important concepts informing our knowledge of the visual regulation of eye growth and refractive development and have transformed treatment strategies for myopia. Several major findings have come from studies of experimental animal models. These include the eye's ability to detect the sign of retinal defocus and undergo compensatory growth, the local retinal control of eye growth, regulatory changes in choroidal thickness, and the identification of components in the biochemistry of eye growth leading to the characterization of signal cascades regulating eye growth and refractive state. Several of these findings provided the proofs of concepts that form the scientific basis of new and effective clinical treatments for controlling myopia progression in humans. Experimental animal models continue to provide new insights into the cellular and molecular mechanisms of eye growth control, including the identification of potential new targets for drug development and future treatments needed to stem the increasing prevalence of myopia and the vision-threatening conditions associated with this disease.

To investigate the diurnal variations in ocular wavefront aberrations over two consecutive days in young adult subjects.Measurements of both lower-order (sphero-cylindrical refractive powers) and higher-order (third and fourth-order aberration terms) ocular aberrations were collected for 30 young adult subjects at 10 different times over two consecutive days using a Hartmann-Shack aberrometer. Seventeen subjects were myopic and 13 were emmetropic. Five sets of measurements were collected each day at approximately 3 hourly intervals, with the first measurement taken at ∼9 am and the final measurement at ∼9 pm.Spherical equivalent refraction (p = 0.029) and spherical aberration (p = 0.043) were both found to undergo significant diurnal variation over the two measurement days. The spherical equivalent was typically found to be at a maximum (i.e. most hyperopic) at the morning measurement, with a small myopic shift of 0.37 ± 0.15 D observed over the course of the day. The mean spherical aberration of all subjects (0.038 ± 0.048 μm) was found to be positive during the day and gradually became more negative into the evening, with a mean amplitude of change of 0.036 ± 0.02 μm. None of the other considered sphero-cylindrical refractive power components or higher-order aberrations exhibited significant diurnal variation over the two days of the experiment (p 0.05). Except for the lower-order astigmatism at 90/180 degree (p = 0.040), there were no significant differences between myopes and emmetropes in the magnitude and timing of the observed diurnal variations (p 0.05).Significant diurnal variations in spherical equivalent and spherical aberration were consistently observed over two consecutive days of measurement. Research and clinical applications requiring precise refractive error and wavefront measurements should take these diurnal changes into account when interpreting wavefront data.

This survey was conducted to determine the testability, distribution and associations of ocular biometric parameters in Chinese preschool children. Ocular biometric examinations, including the axial length (AL) and corneal radius of curvature (CR), were conducted on 1,688 3-year-old subjects by using an IOLMaster in August 2015. Anthropometric parameters, including height and weight, were measured according to a standardized protocol and body mass index (BMI) was calculated. The testability was 93.7% for the AL and 78.6% for the CR overall and both measures improved with age. Girls performed slightly better in AL measurements (P = 0.08) and the difference in CR was statistically significant (P P = 0.12), whereas it was not in boys (P P = 0.16 for boys; P = 0.20 for girls), but the distribution varied when the subgroups were combined (P P = 0.11), whereas the AL/CR ratio was abnormal (P P

Background: To investigate whether ocular axial length influences the tamponade efficacy of three commonly used agents: gas, silicone oil, and heavy silicone oil. Methods: A series of filling experiments was conducted using 19-mm and 25-mm surface-modified spherical model eye chambers to mimic the vitreous cavity. For each agent, tamponade efficacy was assessed across a range of percentage fills, and comparison was made between the two model eye chambers. The behavior of each tamponade agent was quantified by measuring (1) the maximum height of the tamponade bubble, and calculating (2) the arc of retinal contact subtended by the tamponade bubble. Results: Polynomial regression analysis found no statistically significant difference between the regression models for the different-sized model eye chambers for bubble height or arc of retinal contact subtended. This applied to all of the tamponade agents under investigation. Conclusions: Across the range of cavity sizes under investigation, no significant difference in tamponade efficacy (as reflected by the measured dimensions of the tamponade bubble) was identified. © 2010 The Author(s)., published_or_final_version, Springer Open Choice, 21 Feb 2012

Purpose. To investigate the correlation of anterior chamber depth (ACD) with the peripapillary retinal nerve fiber layer (RNFL) thickness, age, axial length (AL), and spherical equivalent in children.Subjects. Consecutive subjects aged 4 to 18 were recruited. Visually disabling eye conditions were excluded. Only the right eye was included for analysis. The ACD was correlated with RNFL thickness, age, spherical equivalent, and AL for all subjects. Subjects were then divided into 3 groups based on their postcycloplegic spherical equivalent: myopes (+1.0 D). The ACD was compared among the 3 groups before and after age adjustment.Results. In 200 subjects (mean age7.6±3.3years), a deeper ACD was correlated with thinner global RNFL (r=-0.2,r2=0.06,P=0.0007), older age (r=0.4,r2=0.1,P<0.0001), myopic spherical equivalent (r=-0.3,r2=0.09,P<0.0001), and longer AL (r=0.5,r2=0.2,P<0.0001). The ACD was deepest in myopes (3.5±0.4 mm,n=67), followed by emmetropes (3.4±0.3,n=60) and then hyperopes (3.3±0.2,n=73) (allP<0.0001). After age adjustment, myopes had a deeper ACD than the other 2 groups (allP<0.0001).Conclusions. In children, a deeper ACD was associated with thinner RNFL thickness, older age, more myopic spherical equivalent, and longer AL. Myopes had a deeper ACD than emmetropes and hyperopes.

Eye is one of the most vital sense organs, important for survival as well as for all the basic needs of day to day life. Eye physiology is a delicate balance between clear refractive media like the lens of a camera and retinal neural layer akin to the photographic film. Any disturbance in this delicate balance can lead to severe diminution of visual capacity leading to permanent incapacitation. In our country, acute eye conditions constitute the commonest group of preventable blindness. Access to proper eye care in India is as such very poor. According to statistics there is one Ophthalmologist for every one million Indians and out of them also, most are urban based. In Armed Forces scenario also, most personnel are in contact with Medical Officers who provide the primary care. Hence, it is important for general public as well as Medical Officers/General practitioners to be aware of common acute eye conditions as well as their emergency first aid.

To examine the objective clinical performance of 'comfort-enhanced' daily disposable contact lenses over a 16-h day.Four contact lenses (Hilafilcon B, Etafilcon A Plus, Nelfilcon A and Nelfilcon A Plus) were evaluated in an investigator masked, open label trial at the end of a week's bilateral wear. Pre-lens non-invasive tear break-up time (PL-NITBUT), tear prism height, bulbar hyperaemia and ocular surface temperature (OST) were measured with the lens in situ at 8, 12 and 16h of wear.There was no difference between how many hours the lenses types were worn each day (F=0.90, p=0.44). The PL-NITBUT decreased with the duration of daily lens wear (F=32.0, p0.001) and was more stable with Nelfilcon A Plus (F=6.00, p=0.002) than with the other lenses evaluated. Bulbar blood vessels increased in coverage (F=11.5, p0.001) but not overall redness (F=0.0, p=0.99) with the duration of daily lens wear, but there was no difference between the lenses (p0.05). The tear prism height decreased with the duration of daily wear (F=27.0, p0.001) and differed between lenses (F=2.9, p=0.04). The OST decreased with the duration of lens wear (F=119.7, p0.001) and was reduced by daily disposable lens wear (F=7.88, p0.001), but did not differ between lenses (F=0.88, p=0.45).Objective measures of tear film indicated a difference between the lenses evaluated for PL-NITBUT and tear prism height, but not for wearing time or bulbar conjunctival hyperaemia. Therefore clinical benefits of daily disposable 'comfort enhancing' contact lenses can be measured, but challenges remain in producing contact lenses that do not compromise anterior eye physiology over the whole day.

I read the article of Lois et al 1 with great interest. I believe, however, that at least in some points it should be supplemented. My recent survey2 concerning a similar subject, which was limited to articles published in the last 2 years, revealed more aspects of the effects of tobacco smoking on the eye physiology and pathology than presented in the paper of Lois et al . It has just been demonstrated that actively smoking at presentation was associated with a fourfold increased risk of cystoid macular oedema (CMO) versus never smoking.3 Former smoking also increased the risk …

Purpose To understand the visual information essential for maintaining stable refraction after emmetropization, we investigated the effects of spatial and temporal stimuli on the refractive status of guinea pigs. Methods Eighty-eight guinea pigs (4 weeks old) were randomly divided into 10 groups. Thirty animals were raised in backgrounds of gray (N = 13), square-wave (N = 9), or sine-wave grating (N = 8). Thirty-one animals were raised in gray backgrounds with three frequencies of flicker: gray-1-Hz (n = 10), gray-6-Hz (n = 12), and gray-20-Hz (n = 9). Eighteen animals were raised in regular cages with different frequencies of flicker (n = 6 respectively in 1-Hz-, 6-Hz-, and 20-Hz-flicker groups). Nine animals were raised in regular cages with no additional stimuli and used as normal controls. Ocular biometry was measured before and after 3 weeks of exposure to the test environments. Results Guinea pigs raised in the gray background for 3 weeks developed myopia, -6.1 ± 2.1 diopters (D), whereas those exposed to either sine-wave or square-wave gratings, or raised in regular cages, retained stable refractions. Animals in the gray-6-Hz group developed lower myopia, -2.7 ± 2.7 D, than the gray group not exposed to flicker. Animals stimulated with a range of flickering frequencies in regular cages also developed myopia but to a lower degree, -3.1 to 0.2 D, than those in gray backgrounds, -5.0 to -2.7 D. Conclusions Guinea pigs require both spatial and temporal stimuli to maintain stable refractions. The influence of temporal stimuli on refraction varies with the type and amount of spatial information available in the visual environment.

In this section we shall be concerned with the peripheral mechanisms in the visual process. When light strikes the retina, physical and chemical changes are induced that lead eventually to a discharge of electrical impulses in the optic nerve fibres. The ‘messages’ in these nerve fibres are a record of the events taking place in the retina; because of the variety of sensations evoked by visual stimuli, these records must be of almost fantastic complexity when even a simple image is formed on the retina. The aim of investigators in this field of eye physiology is to disentangle the skein; their approaches are various but may be classed generally as psychophysical, chemical, and electrophysiological. Remarkable progress has been made, especially in recent years, but there is still a long way to go before anything approaching an exact picture of the retinal processes can be elaborated. The following description is designed more to show the modes of approach to the various problems than to present a theoretical picture of the ‘mechanism of vision’.

In a unit of 20 lessons sighted children were taught about the long cane, guide dogs, daily living skills, eye physiology, causes of blindness, eye care, braille, and attitudes toward blindness. The children were also required to perform some activities under blindfolds. After completing the unit, the children revealed far greater knowledge about blindness and had more positive attitudes toward blind persons—valuable preliminaries for mainstreaming blind children.

(1955). An Electrical Method for Registration and Analysis of the Movements of the Eyes in Nystagmus. Acta Oto-Laryngologica: Vol. 45, No. 1, pp. 25-41.

In the usual course of a prism-vergence test, the eyes are slowly forced to converge (or diverge) until the subject reports that he sees the test object double. Then the prismatic power is slowly decreased, and, at a certain point, fusion of the double images is suddenly regained. Just at this moment when recovery of fusion takes place, the two double images must have attained a certain critical separation, which is capable of initiating fusional movements of the eyes to overcome the diplopia. If, just at the moment of recovery, one of the double images falls in the fovea of one eye, the other image will necessarily fall extrafoveally on the retina of the other eye at a certain angle, an angle of disparity, which is one dimension of the so-called perimacular fusional area. 1 It has been generally assumed that in the prism-vergence tests, as soon as the images

Auf Grund experimenteller Untersuchungen mittels131Jod markierter Rinderalbuminlosung last sich die bisherige Vermutung bestatigen, das die Wirkung des Antigens nach einmaliger Zufuhr in den Glaskorper infolge einer durch die lokale Allergisierung bedingten Resorptionsverzogerung der Wirkung einer weiteren Allergenzufuhr, d.h. einer Zweitinjektion gleichkommt.

Es handelt sich um eine rechnerische und experimentelle Untersuchung der Optokinetik des menschlichen Auges unter veranderlichen Reizbedingungen und durch Anwendung asynchroner und reizsynchroner Einzel- und Doppelblitzserien. 1. Die auf ein verhaltnismasig festes Zeitraster bezogene Blickbewegung tastet langsam bewegte und ruhende Figuren und deren Hintergrund ab, ohne an bestimmte Bildpunkte oder Konturen gekoppelt zu sein. Sie hat zwischen schnell bewegten Figuren und deren Hintergrund die Moglichkeit der Auswahl. 2. Die kritischen Minimal- und Maximalgrosen eines optokinetischen Nystagmus lassen rechnerisch und experimentell bestimmbare Zusammenhange mit den Grosenordnungen der Aktionstypen retinaler und corticaler Neurone erkennen. 3. Die Blockierung und Inversion der optokinetischen Reaktion des Menschen und die damit korrelierenden Sinnestauschungen vermitteln die Wahrscheinlichkeit, das unsere Optomotorik durch die im Tierexperiment mikrophysiologisch untersuchten Reaktionstypen bestimmter Neurone von Retina und optischem Cortex masgebend beeinflust wird.

Ocular movements evoked by stimulation of brain-stem sites in the feline encéphale isolé have been analyzed in an attempt to demonstrate an extraocular proprioceptive mechanism. Procedures designed to reduce extraocular proprioceptive input to the central nervous system included tenotomy of the muscles of one eye, procaine block of one or both Gasserian ganglia, and acute cerebellectomy. None of these procedures resulted in a consistent alteration in accuracy of the induced oculomotor responses. Immobilization of one eye, however, significantly reduced the accuracy of the freely moving eye in assuming the same final position with repeated stimulation of one site. All procedures tested, including occipital lobectomy, resulted in a significant shift of the final position reached by the eyes in response to repeated stimulation of one site. While the shift, unlike the decrease in accuracy seen with immobilization, cannot be interpreted as evidence for an extraocular proprioceptive mechanism, it is discussed with reference to the significance of the ‘goal’ position obtained by repeated stimulation of one site at constant stimulus parameters.