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PubMed2005

New perspectives on eye development and the evolution of eyes and photoreceptors.

Recent experiments on the genetic control of eye development have opened up a completely new perspective on eye evolution. The demonstration that targeted expression of one and the same master control gene, that is, Pax6 can induce the formation of ectopic eyes in both insects and vertebrates, necessitates a reconsideration of the dogma of a polyphyletic origin of the various eye types in all the animal phyla. The involvement of Pax6 and six1 and six3 genes, which encode highly conserved transcription factors, in the genetic control of eye development in organisms ranging from planarians to humans argues strongly for a monophyletic origin of the eye. Because transcription factors can control the expression of any target gene provided it contains the appropriate gene regulatory elements, the conservation of the genetic control of eye development by Pax6 among all bilaterian animals is not due to functional constraints but a consequence of its evolutionary history. The prototypic eyes postulated by Darwin to consist of two cells only, a photoreceptor and a pigment cell, were accidentally controlled by Pax6 and the subsequent evolution of the various eye types occurred by building onto this original genetic program. A hypothesis of intercalary evolution is proposed that assumes that the eye morphogenetic pathway is progressively modified by intercalation of genes between the master control genes on the top of the hierarchy and the structural genes like rhodopsin at the bottom. The recruitment of novel genes into the eye morphogenetic pathway can be due to at least two different genetic mechanisms, gene duplication and enhancer fusion.In tracing back the evolution of eyes beyond bilaterians, we find highly developed eyes in some box-jellyfish as well as in some Hydrozoans. In Hydrozoans the same orthologous six genes (six1 and six3) are required for eye regeneration as in planarians, and in the box jellyfish Tripedalia a pax B gene, which may be a precursor of Pax6, was found to be expressed in the eyes. In contrast to the adults, which have highly evolved eyes, the Planula larva of Tripedalia has single- celled photoreceptors similar to some unicellular protists. For the origin of photoreceptor cells in metazoa, I propose two hypotheses, one based on cellular differentiation and a more speculative one based on symbiosis. The former assumes that photoreceptor cells originated from a colonial protist in which all the cells were photosensitive and subsequent cellular differentiation to give rise to photoreceptor cells. The symbiont hypothesis, which I call the Russian doll model, assumes that photosensitivity arose first in photosynthetic cyanobacteria that were subsequently taken up into red algae as primary chloroplasts. The red algae in turn were taken up by dinoflagellates as secondary chloroplasts and in some species evolved into the most sophisticated eye organelles, as found, for example, in some dinoflagellates like Erythropsis and Warnovia, which lack chloroplasts. Because dinoflagellates are commonly found as symbionts in cnidarians, the dinoflagellates may have transferred their photoreceptor genes to cnidarians. In cnidarians such as Tripedalia the step from photoreceptor organelles to multicellular eyes has occurred. These two hypotheses, the cellular differentiation and the symbiont hypothesis, are not mutually exclusive and are the subject of further investigations.

Animals↗
PubMed2001

Measurement of eye length and eye shape by optical low coherence reflectometry.

BACKGROUND: The precise and rapid measurement of eye length and eye shape is essential for investigating eye growth regulation and myopia. For this purpose, we developed an optical low coherence reflectometer (OLCR) and present preliminary measurements. METHODS: The OLCR includes a super luminescent diode (wavelength: 845 nm, coherence length: approximately 30 microm) and rotating glass cube to produce longitudinal scans at a velocity of 0.42 m/s and a repetition rate of approximately 13 scans/s. Heterodyne detection of light reflected from the anterior cornea and the posterior retina permits to measure axial eye length and eye shape (off-axis eye length). Each measurement consists of five consecutive scans. Reproducibility and precision were determined in one volunteer by measuring axial eye length five consecutive times, each time repositioning the eye. Eye shapes were determined in right eyes of four volunteers by measuring eye length every 3.3 degrees from 10 degrees nasally to 10 degrees temporally. RESULTS: Axial eye length measured repeatedly in one volunteer did not differ between or within the measurements (one-factor ANOVA). The average standard deviation was 11 microm. Eye shapes (a) varied substantially among subjects and (b) differed considerably from the corresponding shapes of spherical model eyes with identical axial eye lengths. CONCLUSION: The newly developed OLCR permits the precise and rapid measurement of eye length and eye shape. Such measurements, especially in children, may provide important information about mechanisms of eye growth regulation and the development of myopia.

Biometry↗
PubMed1998

Neural constraints on eye motion in human eye-head saccades.

We examined two ways in which the neural control system for eye-head saccades constrains the motion of the eye in the head. The first constraint involves Listing's law, which holds ocular torsion at zero during head-fixed saccades. During eye-head saccades, does this law govern the eye's motion in space or in the head? Our subjects, instructed to saccade between space-fixed targets with the head held still in different positions, systematically violated Listing's law of the eye in space in a way that approximately, but not perfectly, preserved Listing's law of the eye in head. This finding implies that the brain does not compute desired eye position based on the desired gaze direction alone but also considers head position. The second constraint we studied was saturation, the process where desired-eye-position commands in the brain are "clipped" to keep them within an effective oculomotor range (EOMR), which is smaller than the mechanical range of eye motion. We studied the adaptability of the EOMR by asking subjects to make head-only saccades. As predicted by current eye-head models, subjects failed to hold their eyes still in their orbits. Unexpectedly, though, the range of eye-in-head motion in the horizontal-vertical plane was on average 31% smaller in area than during normal eye-head saccades, suggesting that the EOMR had been reduced by effort of will. Larger reductions were possible with altered visual input: when subjects donned pinhole glasses, the EOMR immediately shrank by 80%. But even with its reduced EOMR, the eye still moved into the "blind" region beyond the pinhole aperture during eye-head saccades. Then, as the head movement brought the saccade target toward the pinhole, the eyes reversed their motion, anticipating or roughly matching the target's motion even though it was still outside the pinhole and therefore invisible. This finding shows that the backward rotation of the eye is timed by internal computations, not by vision. When subjects wore slit glasses, their EOMRs shrank mostly in the direction perpendicular to the slit, showing that altered vision can change the shape as well as the size of the EOMR. A recent, three-dimensional model of eye-head coordination can explain all these findings if we add to it a mechanism for adjusting the EOMR.

Adult↗
PubMed2001

Eye-head coordination and the variation of eye-movement accuracy with orbital eccentricity.

Different humans vary widely in the tendency to move the head during saccadic shifts in gaze. The reasons for this variation are unknown. Because combined eye-head movements are associated with a recentering of the eyes in the orbits, humans who are "head movers" tend to maintain the eyes within a narrower range than do non-head movers. We explored the possibility that variations in the ability to control eye movements at eccentric positions lead to variations in customary ocular motor range and, by extension, explain the variations in head-movement tendencies. We studied ten normal adults. In each, we measured the full-scale ocular motor range and customary ocular motor range (the eccentricity range within which the eye was found at the conclusion of eye- or eye-head saccades). We also determined the eye-only range, the orbital range within which the probability of a head movement accompanying a gaze shift was low. Customary, eye-only, and full-scale ranges spanned (mean +/-SD) 41.1+/-16.9 degrees, 30.2+/-18.8 degrees, and 92.8+/- 9.1 degrees, respectively. We then assessed variations in kinematics of several ocular motor behaviors as functions of eye eccentricity. The stable fixation range, defined by the range over which drift velocities were below 1 degree/s, spanned 81.1+/-11.2 degrees in the light and 69.5+/-21.5 degrees in the dark. The range over which the gains of the vestibulo-ocular reflex in the light and smooth pursuit approached their values at zero eccentricity spanned 66.3+/-7.1 degrees and 69.0+/-10.0 degrees, respectively. Small centrifugal saccades (5-10 degrees) tended to become either slowed or hypometric with increasing eccentricity. Sensitive to both slowing and hypometria, the ratio of peak gaze velocity to target shift amplitude was flat over a range spanning 65.7+/-14.9 degrees. Finally, the ranges over which the initial saccade placed the fovea upon the target averaged 35.5+/-10.7 degrees for eye-only saccades and 36.6+/-15.0 degrees for eye-head saccades. With the exception of the range of stable fixation in the light, the kinematic ranges were either unrelated or inconsistently related to full-scale range, indicating that the deterioration of eye movements with increasing ocular eccentricity is not a simple consequence of the eyes encountering the limits of their excursion. None of the kinematic ranges correlated positively with customary or eye-only range. Thus, while head movements may be orchestrated so as to maintain the eyes within a desired range, that range (and thus head movement tendencies) is not predicated upon the range of ocular eccentricity over which eye movements are accurately controlled.

Adult↗
PubMed2003

CNV subtype in first eyes predicts severity of ARM in fellow eyes.

AIM: To examine the relation between the type of choroidal neovascularisation (CNV) in the first eye and age related maculopathy (ARM) severity in the fellow eye. METHODS: Colour fundus photographs and fluorescein angiograms from 67 subjects with a clinical diagnosis of CNV in one eye were scrutinised. CNV was classified as wholly classic, predominantly classic, minimally classic, or occult based on the proportion of classic leakage within the lesion. ARM changes in the fellow eye were assigned a severity stage using the system described by the Rotterdam Eye Study. Logistic regression analysis was employed to examine the association between CNV subtype and ARM stage. RESULTS: Of subjects with classic or predominantly classic CNV in the first eye 78% exhibited least no or early ARM features in the fellow eye. By contrast, 85% of subjects with minimally classic or occult CNV in the first eye exhibited more advanced ARM features in the fellow eye. Kruskall-Wallis one way ANOVA by ranks showed that this was highly significant (p = 0.002). Logistic regression analysis showed that as the proportion of occult CNV increased in the first eye, fellow eyes of subjects in this category were more likely to have been assigned to a higher ARM stage (p = 0.019). The area occupied by the CNV in the first eye also influenced severity of ARM changes in the fellow eye. CONCLUSION: The type and extent of CNV in the first affected eye has a distinct relation to ARM severity in the fellow eye. Fellow eyes of subjects with minimally classic or occult CNV in the first affected eye show widespread ARM changes suggestive of retinal pigment epithelial dysfunction. These findings suggest that classic CNV may be focal disease while occult CNV is essentially a more widespread retinal pigment epithelial disorder.

Aged↗
PubMed2006

Perceived barriers to care and attitudes about vision and eye care: focus groups with older African Americans and eye care providers.

PURPOSE: To identify by using focus group methods the perceived barriers to eye care and attitudes about vision and eye care among older African Americans as well as among ophthalmologists and optometrists serving their communities. METHODS: Seventeen focus groups of older African Americans residing in the Birmingham or Montgomery, Alabama, areas were led by an experienced facilitator. Discussion was stimulated by a semistructured script focused on their perceived barriers to eye care and attitudes about vision and eye care. Six focus groups of ophthalmologists and optometrists who practiced in this geographic region addressed the same topics. Discussion was audiotaped and transcribed. Comments were coded using a multistep content analysis protocol. RESULTS: One hundred nineteen African Americans (age range, 59-97 years) and 35 eye care providers (51% ophthalmologists, 49% optometrists) participated. The barrier-to-care problem most frequently cited by both African Americans and eye care providers was transportation. The next most common problems mentioned by African Americans were trusting the doctor, communicating with the doctor, and the cost of eye care; and for eye care providers, the next most common problems were cost, trust, and insurance. With respect to older African Americans' comments on their attitudes about vision and eye care, these comments were predominantly positive (69%), highlighting the importance of eye care and behavior in their lives and attitudes that facilitated care. However, when eye care providers relayed their impressions of African Americans' attitudes about vision and eye care, their comments were largely negative (74%) centering on concerns and frustrations that older African Americans did not have attitudes or engage in behavior that facilitate eye care. CONCLUSIONS: These results provide some guidance for the design of interventions to increase the use of routine eye care in this population. At a societal level, there is a need for affordable and accessible transportation services for older African Americans seeking eye care. For ophthalmologists, optometrists, and their staffs, there is a need for continuing education that imparts culturally sensitive and age-appropriate communication and trust-building skills for interactions with this population. In addition to reinforcing the generally positive attitudes of older African Americans toward the importance of eye care, community-based educational programs should be focused on strategies for overcoming the common barriers to care.

Black or African American↗
PubMed1999

Sympathetic swelling response of the control eye to soft lenses in the other eye.

PURPOSE: To compare central corneal swelling and light scatter after 8 hours of sleep in eyes wearing high- and low-Dk hydrogel lenses and to the contralateral control eyes. METHODS: Twenty neophyte subjects wore a Lotrafilcon A (Dk, 140; Ciba Vision, Duluth GA) silicone hydrogel lens and an Etafilcon A (Dk, 18; Acuvue; Vistakon, Jacksonville, FL) 58% water content hydrogel lens of similar center thickness in random order in the right eye only, for overnight 8-hour periods. The contralateral nonwearing left eyes served as controls. Central corneal thickness was measured using an optical pachometer and light scatter using a Van den Berg stray-light meter before lens insertion, after lens removal on waking, and every 20 minutes for the next 3 hours. RESULTS: Central corneal swelling induced by the Etafilcon A lens on eye opening was significantly higher than with the Lotrafilcon A lens (8.66%+/-2.84% versus 2.71%+/-1.91%; P<0.00001). Light scatter induced by the Etafilcon A lens on eye opening was significantly higher than with the Lotrafilcon A lens (46.09+/-5.62 versus 42.78+/-6.07 Van den Berg units, P = 0.0078). The swelling of the control eyes paired with the Etafilcon A lens-wearing eyes was also slightly but significantly higher than that of the control eyes paired with the Lotrafilcon A lens-wearing eyes (2.34%+/-1.26% versus 1.44%+/-0.91%; P = 0.0002). Light-scatter measurements were not significantly different between control sets of eyes but showed the same trend. CONCLUSIONS: In neophyte subjects, corneal swelling of the contralateral control eyes appears to be influenced by the swelling of the fellow lens-wearing eyes-that is, the swelling of the contralateral control eye was significantly lower when there was less swelling of the fellow eye wearing the high-Dk lens. Although there was no statistically significant difference in light-scatter measurements between the control sets of eyes, a trend similar to the corneal swelling results was observed, which could be used to support the suggestion that this may be a sympathetic physiological response rather than an unusual sampling coincidence.

Adult↗
PubMed2006

[Repetitive instillation of 0.1% cyclosporin A eye drops induces miosis and anterior chamber inflammation-like reactions in monkey eyes].

PURPOSE: Miosis and anterior chamber inflammation-like reactions were recognized after six instillations of 0.1% cyclosporin A eye drops every 30 minutes into rabbit conjunctival sacs. In order to consider species specificity, 0.1% cyclosporin A eye drops were applied by the same method in monkeys. METHODS: Eye drops were applied in five monkeys (monkey A, B, C, D, E); in one eye as control and in nine eyes with 0.1% cyclosporin A. We investigated the changes of pupil diameter, intraocular pressure, and anterior chamber flare before and after applying the eye drops. We also examined the effect on ocular tissue histopathologically. RESULTS: Miosis was recognized in six eyes, but no significant intraocular pressure change was observed in any eyes. In both eyes of monkey A anterior chamber flare increased significantly, and flare increased slightly in both eyes of monkeys B, C, and D. On the other hand, there was no change in either eye of monkey E, including the control eye. Localized necrosis of nonpigmented ciliary epithelium was recognized at the beginning of the ciliary process in both eyes of monkey A. Mild cystoid degeneration of nonpigmented ciliary epithelium was seen at the beginning of the ciliary process in the right eye of monkey C, and in the left eye of monkey D. CONCLUSION: No species specificity can be recognized in monkeys from the fact that there is the selective destruction of nonpigmented epithelium at the beginning of the ciliary process after repeated instillation of 0.1% cyclosporin A eye drops, although there was a difference in miosis and anterior chamber inflammation-like reaction in individual monkeys.

Animals↗
PubMed2003

Direction of saccadic and smooth eye movements induced by electrical stimulation of the human frontal eye field: effect of orbital position.

The present study reports on the direction of saccadic and smooth eye movements, which were induced electrically from the human dorsolateral frontal cortex including the human frontal eye field (FEF). The eye position prior to stimulation was varied in order to examine its effect on induced eye movement direction. The five patients of the study underwent invasive presurgical evaluation for pharmacoresistant epilepsy. The present data show that the direction of electrically induced eye movements was always contralateral and either horizontal or oblique upward if the eye started from the primary position. The elicited direction was changed if the eyes started from an eccentric position. The frequency of oblique eye movements was increased and oblique downward responses were induced, which were not observed if the eye started from the primary position. This was found for saccades and, especially, for smooth eye movements. Head movements, which were almost exclusively induced with saccades, did not depend on initial orbital position. Four conclusions can be drawn. Firstly, saccades and smooth eye movements induced from the human dorsolateral cortex including the human FEF have the same directional bias. Secondly, the frequent upward responses and the absence of downward responses induced from the primary position suggests either a more numerous or a more superficial representation of neurons that code for the former direction. Thirdly, at some sites the direction of saccades and smooth eye movements varies depending on the initial orbital position. Since these directional changes were observed without changes in eye-head coordination, our data suggest that stimulation of the FEF might evoke goal-directed saccades or interferes with a resettable saccade integrator. Fourthly, human studies that investigate eye movements induced from the lateral frontal cortex need to control eye position prior to stimulation.

Adolescent↗
PubMed2006

Visual field recovery after vision restoration therapy (VRT) is independent of eye movements: an eye tracker study.

AIM: It has been argued that patients with visual field defects compensate for their deficit by making more frequent eye movements toward the hemianopic field and that visual field enlargements found after vision restoration therapy (VRT) may be an artefact of such eye movements. In order to determine if this was correct, we recorded eye movements in hemianopic subjects before and after VRT. METHODS: Visual fields were measured in subjects with homonymous visual field defects (n=15) caused by trauma, cerebral ischemia or haemorrhage (lesion age >6 months). Visual field charts were plotted using both high-resolution perimetry (HRP) and conventional perimetry before and after a 3-month period of VRT, with eye movements being recorded with a 2D-eye tracker. This permitted quantification of eye positions and measurements of deviation from fixation. RESULTS: VRT lead to significant visual field enlargements as indicated by an increase of stimulus detection of 3.8% when tested using HRP and about 2.2% (OD) and 3.5% (OS) fewer misses with conventional perimetry. Eye movements were expressed as the standard deviations (S.D.) of the eye position recordings from fixation. Before VRT, the S.D. was +/-0.82 degrees horizontally and +/-1.16 degrees vertically; after VRT, it was +/-0.68 degrees and +/-1.39 degrees , respectively. A cluster analysis of the horizontal eye movements before VRT showed three types of subjects with (i) small (n=7), (ii) medium (n=7) or (iii) large fixation instability (n=1). Saccades were directed equally to the right or the left side; i.e., with no preference toward the blind hemifield. After VRT, many subjects showed a smaller variability of horizontal eye movements. Before VRT, 81.6% of the recorded eye positions were found within a range of 1 degrees horizontally from fixation, whereas after VRT, 88.3% were within that range. In the 2 degrees range, we found 94.8% before and 98.9% after VRT. Subjects moved their eyes 5 degrees or more 0.3% of the time before VRT versus 0.1% after VRT. Thus, in this study, subjects with homonymous visual field defects who were attempting to fixate a central target while their fields were being plotted, typically showed brief horizontal shifts with no preference toward or away from the blind hemifield. These eye movements were usually less than 1 degrees from fixation. Large saccades toward the blind field after VRT were very rare. CONCLUSION: VRT has no effect on either the direction or the amplitude of horizontal eye movements during visual field testing. These results argue against the theory that the visual field enlargements are artefacts induced by eye movements.

Adult↗
PubMed2004

Eyes open and eyes closed as rest conditions: impact on brain activation patterns.

The patterns of associated brain activations during eyes-open and eyes-closed states in complete darkness considerably differ in fMRI. An "interoceptive" state with the eyes closed is characterized by visual cortex activation, while an "exteroceptive" state with the eyes open is characterized by ocular motor system activity. The impact of the chosen rest condition (eyes open or eyes closed in complete darkness) on the pattern of brain activations during visual stimulation was evaluated in 14 healthy volunteers. During fixation or dim light room illumination, the activation of the visual cortex was larger with the eyes-open rest condition than with the eyes-closed rest condition; however, activation of the lateral geniculate nucleus was smaller. Activations that can be attributed to ocular motor structures, such as the prefrontal cortex, parietal and frontal eye fields, cerebellar vermis, the thalamus, and basal ganglia were larger with the eyes-closed rest condition than with the eyes-open rest condition. BOLD signal decreases of cortical areas that represent visual, somatosensory, auditory, and vestibular functions were seen in the comparison fixation of light emitting diode (LED) minus eyes closed. Thus, the choice of rest condition (either eyes closed or eyes open) is critical for stimulus-induced brain activation patterns. Activity of the ocular motor system as well as deactivation of sensory cortical areas may go undetected with eyes open as rest condition.

Adolescent↗
PubMed2005

The effect of two novel lubricant eye drops on tear film lipid layer thickness in subjects with dry eye symptoms.

PURPOSE: Because the lipid layer of the tear film is recognized as a critical component in dry eye disease, this study was designed to determine if a single eye drop of either Soothe or Systane produces a significant increase in lipid layer thickness (LLT) for subjects reporting symptoms indicative of dry eyes. METHODS: A double-blind, internally paired study was performed. A custom-built lipid layer interferometer, enabling characterization of lipid layer interference patterns, was used to quantify baseline LLT (OU) of eligible subjects. Inclusion criteria included: 1) presence of dry eye symptoms and 2) baseline LLT < or =75 nm. Subjects (n = 40) received a single eye drop of Soothe in one eye and a single eye drop of Systane in the contralateral eye. After the instillation of each test drop, LLT was reanalyzed for all subjects. RESULTS: The mean +/- standard error baseline LLT pre-eye drop instillation was 60.0 +/- 1.8 nm for eyes treated with Soothe and 61.5 +/- 1.8 nm for eyes treated with Systane. These means were not significantly different (p > 0.5). The mean LLT for eyes treated with Soothe increased to 124.4 +/- 4.9 nm (p < 0.0001). The mean LLT for eyes treated with Systane increased to 71.3 +/- 2.6 nm (p < 0.0001). The LLT increase from Soothe was significantly greater than that from Systane (p < 0.0001). CONCLUSIONS: In subjects with symptoms indicative of dry eye states and LLT < or =75 nm, one eye drop of Soothe more than doubled LLT, a 107% mean increase, whereas Systane increased LLT by 16%.

Adult↗
PubMed2004

Utilization of eye care services by Victorians likely to benefit from eye care.

AIM: To assess the utilization of eye care services by Australians most likely to benefit from eye assessment. METHODS: The Melbourne Visual Impairment Project was a population-based study that collected demographic, health and vision-related information including use of eye care services. A standardized detailed ophthalmic examination was performed. Utilization of eye care services by those who might most benefit from eye care was assessed and compared to the general population. These participants include those with undiagnosed glaucoma, unoperated visually significant cataract, undercorrected refractive error, diabetes mellitus, age-related macular degeneration and visual acuity < 6/12. Sociodemographic characteristics were assessed for their influence on eye care utilization among these participants. RESULTS: A total of 4744 urban and rural residents participated (86% of those eligible) and 4612 (83% of total eligible) of these had a complete data set for the use of eye care services and were included. There were 933 participants (20.2%) who did not report eye assessment in the previous 5 years, and 891 participants (19.3%) had one or more aforementioned conditions potentially benefiting from eye care. Of these, between 34.4% and 59.4% reported no examination in the previous year and between 9% and 25% reported no examination within the previous 5 years. These participants were more likely to seek eye care within the short term (1 year) if they had a family history of eye disease, otherwise a noticed change in vision was the main influence in the longer term (2-5 years). Male participants, younger participants and those whose main spoken language was not English were less likely to seek eye care in the longer term. CONCLUSIONS: In Victoria 19% of those >40 years of age have potentially unmanaged eye disease including glaucoma, unoperated visually significant cataract, undercorrected refractive error, age-related macular degeneration, diabetes mellitus or visual acuity < 6/12. A substantial proportion of these report no eye assessment in the previous 1, 2 or 5 years or ever before. Younger age, male sex and main language other than English make assessment less likely. Many may have these conditions despite having had a recent eye assessment.

Adult↗
PubMed1991

Analysis of vertebrate eye movements following intravitreal drug injections. IV. Drug-induced eye movements are unyoked in the turtle.

1. Eye movements of awake turtles were measured from both eyes simultaneously using two search-coil contact lenses. Optokinetic nystagmus (OKN) was evoked by full field patterns moving horizontally at different stimulus velocities. Intravitreal injections of either bicuculline or 2-amino-4-phosphonobutyrate (APB) were then made into one eye, after which eye movements were again recorded under similar stimulus conditions. Several days later, eye movements were again recorded and recovery was observed. 2. The effects of these two synaptic drugs on the optokinetic responses of the injected eye were similar to those previously reported in turtles, rabbits, and decorticate cats. APB, which blocks the retinal ON pathways, completely blocked visually evoked responses to any stimulus direction or velocity presented to the injected eye. On the other hand, the uninjected eye was still responsive to optokinetic stimuli. This difference between the eyes is consistent with the nonconjugate nature of OKN in the turtle. 3. After bicuclline application, the injected eye displayed a spontaneous nystagmus with its slow phase in the temporal-to-nasal direction. The movements of the injected eye were independent of stimulus direction or a range of stimulus velocities. During that effect, the eye contralateral to the injection still responded to visual stimuli in a direction- and velocity-dependent manner. For example, if the uninjected eye was exposed to optokinetic stimuli moving temporal-to-nasal, both eyes would then move in their respective temporal-to-nasal directions. This nonconjugate ocular behavior is similar to that seen when each eye of a normal turtle was exposed to its temporal-to-nasal stimulus.(ABSTRACT TRUNCATED AT 250 WORDS)

Aminobutyrates↗
PubMed2003

Single gene controlling black eyes found from the intercross of two yellow-eyed strains of Heliothis virescens.

Black eyes of the moth of Heliothis virescens were controlled by a single, autosomal recessive gene, b. Black-eyed moths were discovered among progeny in an outcross made to test for allelism of two known genes ye, conferring yellow eyes, and yes, conferring yellow eyes and scales. Complementation to the wildtype gray eye color was observed in 686 (99.1%) of the progeny; however, six progeny of one mating exhibited the new phenotype, black eyes. Two black-eyed females mated to a wildtype sibling produced descendents displaying golden eyes, striped eye, purple eyes, white eyes, and "cat's" eyes. No black-eyed progeny were observed in the F2 generation of lines segregating for y, ye, and yes, confirming that black eye was not a combination of those other genes. These newly discovered genes could be useful in basic studies of developmental genetics or in applied transgenesis.

Animals↗
PubMed1994

[Recording characteristics of the eye mark recorder in measurements of vertical eye movements].

Electronystagmography (ENG) has been widely used in physiological studies of eye movements. It is generally known that ENG is at a disadvantage in recording the vertical component of eye movements, and thus there has been a great deal of difficulty in physiological studies of vertical eye movements using ENG. The eye mark recorder is an instrument which has already been used in the study of visual point movement in various situations. We tried to apply the eye mark recorder to the recording of eye movements in normal volunteers, and then compared its recording characteristics with those of ENG. When recording vertical eye movements with the eye mark recorder there is little baseline drift and no confusing waves caused by blinking, which is sometimes misinterpreted as nystagmus. The result is easy calibration of the device and more accurate measurement of the slow-phase velocity of nystagmus than ENG. Recording with the eye mark recorder is atraumatic and allows binocular visual stimulation. There are certain other techniques, such as search coil or video oculography, which allow more accurate recording of vertical eye movements than ENG. The search coil techniques, however, requires the attachment of a measuring contact lens during the examination and video oculography is still in development process, so both of them are difficult to use widely. Thus, we found that the eye mark recorder has a great advantage in recording the slow-phase eye velocity of vertical nystagmus and the vertical component of smooth eye movements in humans. We think that eye mark recorder can serve as a powerful new tool to investigate vertical OKN and OKAN.

Adult↗
PubMed1995

A comparative microbiological study of clinically healthy eyes and those affected by ophthalmia in cattle and the association of noctuid eye-frequenting moths.

The eyes of clinically healthy Simmentaler cattle and those affected by ophthalmia were sampled once a month over a continuous period of 12 months for bacterial, mycoplasmal and ureaplasmal infections. In total 478 eyes, representing from a clinical viewpoint 414 healthy and 64 affected eyes, were swabbed. Bacteria were isolated from 201 (48.6%) healthy eyes and 56 (87.5%) affected eyes. No bacteria were isolated from the remaining eyes. Eleven genera of bacteria were isolated from healthy eyes and 8 genera from affected eyes. The majority of isolates were classified in the genera Moraxella, Neisseria and Staphylococcus. Mycoplasmas were isolated from 247 (50.7%) healthy eyes and 27 (42.2%) affected eyes. No mycoplasmas were isolated from the remaining eyes. Ureaplasmas were not isolated from any animal. Eye-frequenting moths were collected on 3 occasions during the investigation and bacterial and mycoplasmal isolation techniques were performed on a total of 21 moths. Twelve different genera of bacteria, mostly Nocardia, Corynebacterium, Staphylococcus, Moraxella, and mycoplasmas were isolated from various eye-frequenting moths. Scanning electron microscopical studies of the proboscis of the moths showed it to contain various sensillae and short triangular denticles that could possibly cause damage to the mucous membranes of the eyes and predispose to ophthalmia in cattle.

Animals↗
PubMed2000

Fellow eye prognosis in patients with severe visual field loss in 1 eye from chronic open-angle glaucoma.

OBJECTIVES: To examine the prognosis for the fellow eye of patients with severe visual field loss in 1 eye from chronic forms of open-angle glaucoma, and to identify risk factors for visual field progression in such eyes. METHODS: Review of 36 patients followed in an academic medical center with monocular severe visual field loss (Advanced Glaucoma Intervention Study score > or =12) from open-angle glaucoma either at initial Humphrey visual field testing or during follow-up. Change in Advanced Glaucoma Intervention Study visual field score and clinical evaluation were used to determine visual field progression. Kaplan-Meier survival analysis and Cox proportional hazards survival regression were used to estimate visual field progression in fellow eyes and assess possible risk factors. RESULTS: During 67+/-32 months (mean +/- SD), 12 of 36 first-affected eyes (33%) and 6 fellow eyes (17%) had significant visual field progression. The Kaplan-Meier estimate of visual field progression in the fellow eye was 12.4% at 5 years after severe visual field loss in the first eye. Compared with stable fellow eyes, fellow eyes with visual field progression had significantly larger initial cupdisc ratio, smaller between-eyes difference in the initial Advanced Glaucoma Intervention Study score, and lower calculated ocular perfusion pressure. Ocular perfusion pressure was the only variable significantly associated with visual field progression by Cox proportional hazards survival regression (P = .019). During an average of 10.2 years of disease, 2 patients (6%) became bilaterally blind from glaucoma. CONCLUSIONS: In this predominantly white population, fellow eyes of patients with severe visual field loss in 1 eye from open-angle glaucoma were not at particularly high risk for further visual field progression, and few patients became bilaterally blind. Fellow eye visual field progression was associated with lower calculated ocular perfusion pressure.

Adult↗