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PubMed2002

The genetic control of eye development and its implications for the evolution of the various eye-types.

Mutations in the Pax 6 homologs of mammals and insects prevent eye development and targeted expression of both mammal and insect Pax 6 homologs is capable of inducing functional ectopic eyes. Supported by RNA interference experiments in planarians and nemerteans, these findings indicate that Pax 6 is a universal master control gene for eye morphogenesis. Since all metazoan eyes use rhodopsin as a photoreceptor molecule and the same master control gene for eye development, we postulate a monophyletic origin of the various eye types. The finding of well developed eyes in jellyfish which essentially lack a brain, leads us to propose that the eye as a sensory organ evolved before the brain which is an information processing organ. The finding of highly developed eyes with a lens, vitreous body, stacked membranes like a retina and shielding pigment in unicellular dinoflagellates, raises the possibility that the prototypic eyes might have been acquired from symbionts.

Animals↗
PubMed2006

Reliance on head versus eyes in the gaze following of great apes and human infants: the cooperative eye hypothesis.

As compared with other primates, humans have especially visible eyes (e.g., white sclera). One hypothesis is that this feature of human eyes evolved to make it easier for conspecifics to follow an individual's gaze direction in close-range joint attentional and communicative interactions, which would seem to imply especially cooperative (mututalistic) conspecifics. In the current study, we tested one aspect of this cooperative eye hypothesis by comparing the gaze following behavior of great apes to that of human infants. A human experimenter "looked" to the ceiling either with his eyes only, head only (eyes closed), both head and eyes, or neither. Great apes followed gaze to the ceiling based mainly on the human's head direction (although eye direction played some role as well). In contrast, human infants relied almost exclusively on eye direction in these same situations. These results demonstrate that humans are especially reliant on eyes in gaze following situations, and thus, suggest that eyes evolved a new social function in human evolution, most likely to support cooperative (mututalistic) social interactions.

Animals↗
PubMed2003

Autologous serum eye drops for the treatment of severe dry eye in patients with chronic graft-versus-host disease.

We investigated the efficacy and safety of autologous serum eye drops for the treatment of severe dry eye after allogeneic haematopoietic stem cell transplantation (SCT). A total of 14 patients (four males and 10 females; median age, 31.0 years) with severe dry eye associated with chronic graft-versus-host disease (cGVHD) were enrolled in this study. All patients were refractory to treatment with conventional artificial tears. Autologous serum eye drops, a solution made of 20% autologous serum in sterile saline, were applied 10 times per eye per day. The patients were evaluated every 4 weeks according to visual acuity, corneal sensitivity, vital staining of the ocular surface, tear dynamics, and subjective assessments of symptoms (complaints scores). The median follow-up period was 19.4 months (range: 4-41 months). After 4 weeks of treatment, significant improvement was observed in both complaint scores (from 33.7+/-12.3 to 23.6+/-10.6 points; P<0.01) and fluorescein scores (from 5.8+/-2.0 to 2.4+/-0.9 points; P<0.005). Significant improvements were observed also in rose-bengal staining and tear break-up time. In seven of the 14 patients, the responses were maintained for 6-41 months (median:19.4+/-8.3 months), while six of the other seven patients required treatment with punctal plugs in addition to autologous serum eye drops. One of these other seven patients developed eczema around the eyelids, after which the treatment was discontinued. No serious adverse events were observed. We conclude that autologous serum eye drops are safe and effective for treating severe dry eye associated with cGVHD and that more efficient control of dry eye may be achieved by the combined use of autologous serum eye drops with punctal plugs.

Adult↗
PubMed1983

Inheritance of brown-eye and colourless-eye in the mosquito Aedes aegypti.

An autosomal recessive gene bw (probably closely linked to y on chromosome 2) gives a brown eye colour. When this gene and the sex-linked gene re (red-eye) are both homozygous, a colourless-eye results. Brown-eye shows good viability and penetrance, and it has been maintained as a pure stock. Colourless-eye shows 87% penetrance in both sexes, and the females are low in viability and fertility. A colourless-eye stock has been maintained by crossing colourless-eyed males to their heterozygous red-eyed sibs. Crosses indicated no allelism between bw and ru (rust-eye), nor with w (white-eye). However some complementation between bw and w was indicated.

Aedes↗
PubMed1970

The spectral sensitivities of single receptor cells in the lateral, median, and ventral eyes of normal and white-eyed Limulus.

Spectral sensitivity curves can be distorted by screening pigments. We have determined whether this is true for Limulus polyphemus by determining, from receptor potentials recorded using intracellular microelectrodes, spectral sensitivity curves for normal animals and for white-eyed animals (which lack screening pigment). Our results show: (a) In median ocelli, the curve for UV-sensitive receptor cells peaks at 360 nm and does not depend on the presence of screening pigment, (b) The curve for ventral eye photoreceptors is identical to that for retinular cells from the lateral eyes of white-eyed animals and peaks at 520-525 nm. (c) In normal lateral eyes, when the stimulating light passes through screening pigment, the curve indicates relatively more sensitivity in the red region of the spectrum than does the curve for white-eyed animals. Therefore, the screening pigment is probably red-transmitting, (d) In median ocelli, the curve for visible-sensitive cells peaks at 525 nm and is approximately the same whether the ocelli are from normal or white-eyed animals. However, the curve is significantly broader than that for ventral eyes and for lateral eyes from white-eyed animals.

Animals↗
PubMedDate not supplied

Eye pigments in wild-type and eye-color mutant strains of the African malaria vector Anopheles gambiae.

Chromatographic analysis of pigments extracted from wild-type eyes of the mosquito Anopheles gambiae reveals the presence of the ommatin precursor 3-hydroxykynurenine, its transamination derivative xanthurenic acid, and a dark, red-brown pigment spot that probably is composed of two or more low mobility xanthommatins. No colored or fluorescent pteridines are evident. Mosquitoes homozygous for an autosomal recessive mutation at the red-eye (r) locus have a brick-red eye color in larvae, pupae, and young adults, in contrast to the almost black color of the wild eye. Mosquitoes homozygous for this mutant allele have levels of ommochrome precursors that are indistinguishable from the wild-type, but the low-mobility xanthommatin spot is ochre-brown in color rather than red-brown as in the wild-type. Mosquitoes with two different mutant alleles at the X-linked pink-eye locus (p, which confers a pink eye color, and pw, which confers a white eye phenotype in homozygotes or hemizygous males) have normal levels of ommochrome precursors but no detectable xanthommatins. Mosquitoes homozygous for both the r and p mutant alleles have apricot-colored eyes and show no detectable xanthommatins. Both the pink-eye and red-eye mutations appear to involve defects in the transport into or assembly of pigments in the membrane-bound pigment granules rather then defects in ommochrome synthesis.

Animals↗
PubMed2005

Effects of eye position on estimates of eye displacement for spatial updating.

Neurons in the parietal cortex represent spatial memory of visual stimuli in an eye-centered coordinate frame. To preserve spatial stability across eye movements, spatial memory must be updated during each eye movement. Because eye movement signals in the parietal cortex are known to be modulated by eye position in the orbit, estimates of eye displacement on the basis of these signals could also be influenced by eye position. The present study examined the possible effect of eye position on the accuracy of memory-guided saccades in monkeys following saccades or smooth pursuit during the memory period. The results showed that eye position has a modest effect on saccade localization, suggesting that eye position signal plays a modulatory role in updating visuospatial working memory.

Animals↗
PubMed2005

Increase in central corneal thickness in dry and normal eyes with application of artificial tears: a new diagnostic and follow-up criterion for dry eye.

AIMS: To investigate the effect of artificial tear application on central corneal thickness (CCT) in dry and normal eyes. METHODS: Forty eyes of 40 patients with symptomatic dry eyes and 20 eyes of 20 controls were included in the study. A combination artificial tear therapy was given to both groups for 1 week. The CCT was measured with ultrasonic pachymetry before and after the therapy. In addition, at the beginning of the study, 11 dry eye patients and eight control patients were evaluated separately as a subgroup: they received artificial tears every 10 min for an hour to determine whether this might constitute a diagnostic criterion. Results were analysed with a Wilcoxon test, accepting p < 0.01 as significant. RESULTS: The mean CCT in the dry eye group before and after 1-week therapy was 531.5 +/- 16.5 and 559.6 +/- 26.1 microm, respectively (p < 0.0001); thus yielding an average CCT increase of 28.1 +/- 9.4 microm (=5.30%: 1.65% minimum; 7.03% maximum) from baseline. The mean CCT in the control group before and after 1-week therapy was 549.2 +/- 37.8 and 552.3 +/- 39.8 microm, respectively (p = 0.001); thus, yielding an average CCT increase of 3.1 +/- 1.9 microm (=0.56%: 0.00% minimum; 1.18% maximum) from baseline. When the subgroup was evaluated separately, the average increase from baseline in 11 dry eye patients was 10.4 +/- 4.0 microm (=1.89%: 0.60% minimum; 4.26% maximum) after 1 h of artificial tear application, while it was 2.9 +/- 2.0 microm (=0.51%: 0.00% minimum; 0.58% maximum) in eight control patients (p < 0.0001). CONCLUSION: The CCT in dry eyes increases rapidly and significantly compared to normal eyes after application of artificial tears. It is suggested that this increase could be used as a criterion in the diagnosis and follow up of dry eyes, and that this increase in thickness should be considered in intra-ocular pressure measurements as well as in refractive surgical procedures.

Adult↗
PubMed1982

Eye position signals in the flocculus of the monkey during smooth-pursuit eye movements.

1. Discharges of Purkinje cells and mossy fibres were recorded from the flocculus of monkeys trained to fixate a small visual target and to track the target when it moved slowly.2. Discharges of Purkinje cells changed tonically with shifts of gaze. Firing rates were linearly related to eye positions for either the entire or more than half the eye-position range in 12.6% of Purkinje cells tested (76/603 units).3. The eye position-related activity (position component) was observable in these cells also during smooth-pursuit eye movements. It was typically seen during slow eye movements (velocities less than 10 deg/s) but became undetectable during high velocity movements (faster than 50 deg/s).4. The position component became prominent when smooth pursuit was executed at the preferred loci of the individual cells. In the majority of the cells tested at their preferred loci, the position component was observable to a relatively high frequency, such as 0.5 Hz (+/- 10 deg; peak velocity 31 deg/s).5. Forty-five mossy fibre units showed saccade-related bursts and position-related intersaccadic tonic activity during steady eye position. In each unit, the position component was found only during fixations within a specific range of eye positions. During fixations outside these regions, all position-related mossy fibres were completely silent.6. During sinusoidal smooth-pursuit eye movements, the mossy fibres also displayed cyclic modulations in activity. All fibres discharged with eye movements in one direction and were silent during eye movements in the other direction.7. Saccade-related bursts from mossy fibres led the onset of saccades, ranging from 0 to 19 ms with a mean lead-time of 6.9 ms. This observation negates the possibility that the position-related signals might represent proprioceptive impulses from the stretch receptors of the extraocular muscle.

Action Potentials↗
PubMedDate not supplied

Autologous serum eye drops for dry eye after LASIK.

PURPOSE: To evaluate the efficacy of autologous serum eye drops for dry eye after LASIK in a prospective, randomized study. METHODS: Fifty-four eyes of 27 male patients who underwent LASIK were divided into two groups; patients who used autologous serum eye drops and those who used artificial tears postoperatively. Schirmer test with anesthesia, tear break-up time (BUT), and rose bengal and fluorescein staining for the ocular surface were prospectively compared between the groups. All values were also compared before and after surgery (at 1 week [except for Schirmer test], 1 month, 3 months, and 6 months) in each group. RESULTS: Tear BUT was greater in the autologous serum eye drops group than in the artificial tears group at 6 months postoperatively. Rose bengal score was lower in patients using autologous serum eye drops than in patients using artificial tears at 1 month and 3 months postoperatively. No significant difference was noted between patients using autologous serum eye drops and patients using artificial tears in the value of Schirmer test with anesthesia and fluorescein scores. In the autologous serum eye drops group, tear BUT was increased at 3 months after LASIK, rose bengal score was lower at 1 month and 3 months, and fluorescein score was lower at 1 month after LASIK compared to preoperative values, respectively. In the artificial tears group, all values (Schirmer test, tear BUT, rose bengal score, and fluorescein score) showed no differences between before and after LASIK. No differences were noted in the subjective scores for dryness between the autologous serum eye drops and artificial tears groups. CONCLUSIONS: The autologous serum eye drops group showed prolongation of the tear BUT and a reduction in rose bengal staining score.

Adult↗
PubMedDate not supplied

Dry eye, blepharitis and chronic eye irritation: divide and conquer.

Dry eye and posterior blepharitis are the two most common causes for chronic eye irritation. Dry eye is caused by loss of water from the tear film resulting from either decreased tear production or increased tear film evaporation. The resultant increase in tear film osmolarity causes the changes on the eye surface responsible for the symptoms of dry eye. Posterior blepharitis causes eye irritation from inflammation, and leads to the development of meibomian gland dysfunction. The patient history is a powerful tool in narrowing the differential diagnosis of chronic eye irritation or even establishing the diagnosis. The exam adds power to the history, and sorts out the mechanisms causing dry eye symptoms. The primary goal of dry eye treatment is to lower elevated tear film osmolarity. This can be achieved with TheraTears treatment, either with or without punctal plugs. The primary goal of meibomitis treatment is to reduce inflammation. This can be achieved by hot compresses and lid massage and, when necessary, systemic treatment with low dose doxycycline. By determining the cause or causes of chronic eye irritation, effective treatments can be employed.

Blepharitis↗
PubMed1989

Donor eyes. A comparison of characteristics and outcomes for Eye Bank and local tissue.

The Corneal Recipient Registry was begun in 1985 to collect information on all recipients of corneal grafts in the province of Ontario, Canada, and on the donors providing tissue. While most of the tissue is handled by the Eye Bank of Canada (Ontario Division), ophthalmologists in centers away from the Eye Bank often use local tissue when it is available. Comparison of the donor characteristics of local tissue with that obtained through the Eye Bank revealed that local donors were 9-10 years younger (p less than 0.01), their times to enucleation were an hour less (p less than 0.02), and they were much more likely to be the victims of trauma than the donors of Eye Bank eyes. Prognosis of the graft, assessed using life table methods, suggested that success of local eyes was 89% after 6 months, compared with 80% for Eye Bank eyes in the same period, but this was not a significant difference (p greater than 0.05). While the Eye Bank is a more common source of tissue, eyes obtained locally are more likely to represent the "ideal" tissue for many corneal surgeons.

Adult↗
PubMed1980

Regeneration of optic nerve fibres from a compound eye to both tecta in Xenopus: evidence relating to the state of specification of the eye and the tectum.

Xenopus with one double-nasal (NN), double-temporal (TT) or double-ventral (VV) eye were induced to regenerate optic fibres from the compound eye to both tecta after metamorphosis. The extent of the projection from the compound eye was then estimated autoradiographically at various intervals after nerve section. The regenerated projection covered the whole of the contralateral tectum but covered only a restricted part of the ipsilateral tectum; thus NN eyes innervated caudomedial tectum only, TT eyes innervated rostrolateral tectum only and VV eyes innervated medial tectum only. Since the tectum ipsilateral to the compound eye also received the projection from the normal eye these results are taken to indicate that NN, TT and VV eyes are unregulated systems in terms of the retinal positional markers that they carry; each such eye bears only the appropriate half-set of such markers.

Animals↗
PubMed1997

Penetrating keratoplasty in the Singapore National Eye Centre and donor cornea acquisition in the Singapore Eye Bank.

We analyzed all penetrating keratoplasties performed in the Singapore National Eye Centre from 1 January 1991 to 31 December 1995, using records of the Singapore Eye Bank Registry, evaluating the indications, complications, causes of graft failure, visual outcome and graft survival rate. We also looked into donor cornea acquisition in the Singapore Eye Bank and its influence on the development of corneal transplantation in the Singapore National Eye Centre. A total of 327 penetrating keratoplasties were performed during the 5-year period. Bullous keratopathy was an indication in 26.3% of cases. Of these, aphakic bullous keratopathy accounted for 11.6% of all cases, while pseudophakic bullous keratopathy accounted for 11.3%. Other indications were regrafts (11.9%), corneal dystrophies (10.4%), traumatic corneal scarring (10.1%) and keratoconus (9.8%). Graft rejection was a complication in 20% of all cases. Of these, 40.9% led to graft failure. Other major complications were raised intraocular pressure (18%), epithelium-related problems (7.3%), wound dehiscence (4.3%), cataract (3.3%) and microbial keratitis (3.1%). The main causes of graft failure were graft rejection (8.2%), endothelial failure (2.4%), infection (2.4%) and glaucoma (2.1%). Of the 327 grafts, 40.3% achieved best corrected visual acuity of 6/12 or better; 70.8% achieved vision of 6/24 or better. The overall graft survival rate was 82.3% after a mean follow-up period of 2 years. Donor corneas for the penetrating keratoplasties were obtained from foreign eye banks as well as locally, with the local donation rate steadily increasing from 1991 to 1996, with the establishment of proper eye banking facilities and the Singapore Eye Bank. These results show that the indications and outcome of penetrating keratoplasty in the Singapore National Eye Centre are similar and comparable to that of other centres with established corneal grafting programmes. The establishment of the Singapore Eye Bank has ensured the proper co-ordination of acquisition of donor material which has been vital to the development of corneal transplantation in the Singapore National Eye Centre.

Adolescent↗
PubMed2001

Unique morphology of the human eye and its adaptive meaning: comparative studies on external morphology of the primate eye.

In order to clarify the morphological uniqueness of the human eye and to obtain cues to understanding its adaptive significance, we compared the external morphology of the primate eye by measuring nearly half of all extant primate species. The results clearly showed exceptional features of the human eye: (1) the exposed white sclera is void of any pigmentation, (2) humans possess the largest ratio of exposed sclera in the eye outline, and (3) the eye outline is extraordinarily elongated in the horizontal direction. The close correlation of the parameters reflecting (2) and (3) with habitat type or body size of the species examined suggested that these two features are adaptations for extending the visual field by eyeball movement, especially in the horizontal direction. Comparison of eye coloration and facial coloration around the eye suggested that the dark coloration of exposed sclera of nonhuman primates is an adaptation to camouflage the gaze direction against other individuals and/or predators, and that the white sclera of the human eye is an adaptation to enhance the gaze signal. The uniqueness of human eye morphology among primates illustrates the remarkable difference between human and other primates in the ability to communicate using gaze signals.

Adaptation, Physiological↗
PubMed1995

The role of eye protection in work-related eye injuries.

PURPOSE/BACKGROUND: A recent survey of general hospitals by the Victorian Injury Surveillance System found that ocular trauma represented 15% of work-related injuries. As circumstances surrounding occupational eye injuries have been poorly documented previously, their associations to occupation, industry and work-safety practices, including safety eyewear use, need to be identified to develop appropriate preventive strategies for high-risk groups. DESIGN AND SETTING: From a prospective cross-sectional survey of all eye injuries treated at the Royal Victorian Eye and Ear Hospital, work-related cases were analysed for demographic, occupational and safety eye-wear information. Hospital-based data were supplemented by information from WorkCover Authorities and Labour Force statistics to derive incidence and cost estimates. RESULTS: There were 9390 eye injuries during the 18-month survey period; 42% (n=3923) of total and 29% (n=52) of penetrating ocular injuries occurred at work. The most frequently injured were metal, automotive and building trades workers grinding and drilling (41% of outpatients) and hammering (53% of penetrating eye injuries). Automotive workers had the highest frequency for penetrating injuries, and most were exposed to hammering and were also the least likely to wear safety eye-wear. CONCLUSION: Eye injuries are frequent (10% of work-related injuries) and highly preventable by the correct use of safety eye-wear, a cost-effective intervention that may result in cost savings of $59 million for work-type activities in the occupational and domestic settings in Australia each year.

Accidents, Occupational↗
PubMed2000

Aerial performance of stalk-eyed flies that differ in eye span.

Stalk-eyed flies have eyes placed laterally away from the head on elongated peduncles. The elongation of eye span may increase the energetic cost of flight, reduce flight performance via aerodynamic effects or via increased load, or necessitate compensatory changes in other body dimensions. Body mass and body dimensions were measured to test the hypothesis that elongation of eye span is correlated with increased head mass in two closely related species of stalk-eyed flies. Cyrtodiopsis whitei is sexually dimorphic, with the eye span of larger males exceeding body length. Cyrtodiopsis quinqueguttata is sexually monomorphic with eye span substantially less than body length. Although eye span was significantly longer in C. whitei, head mass did not differ between species after accounting for differences in body mass. C. whitei males had longer wings, heavier thoraxes, and lighter abdomens in relation to body mass than did female C. whitei or C. quinqueguttata of either sex. Three-dimensional tracking of flight paths showed that path velocity and the horizontal component of velocity did not differ according to species or sex, but the long-eyed C. whitei males showed reduced overall aerial performance by flying at shallower ascent angles and reduced vertical velocity. Although increased mass loading does not occur in C. whitei males, increased drag, aerodynamic effects from the wake of the eye stalks, and constrained visual processing are possible mechanisms which could cause their reduced performance.

Animals↗
PubMed2006

Corneal thickness measurements in normal and keratoconic eyes: Pentacam comprehensive eye scanner versus noncontact specular microscopy and ultrasound pachymetry.

PURPOSE: To compare central corneal thickness (CCT) measurements taken with the Pentacam comprehensive eye scanner (CES), noncontact specular microscopy (SM), and ultrasound pachymetry (UP) in normal and keratoconic corneas. SETTING: Department of Ophthalmology, Ankara University School of Medicine, Ankara, Turkey. METHODS: In a prospective study, 3 CCT measurements were taken with the Pentacam CES, SM, and UP in that sequence from 1 eye of 45 consecutive patients with myopia (group A) and 62 consecutive patients with keratoconus (group B). Eyes with keratoconus were further divided into 3 subgroups, mild, moderate, and severe, according to the mean keratometry readings. RESULTS: Pentacam CES (r = 0.994) and UP (r = 0.993) demonstrated very high and comparable reproducibility in group A. In group B, Pentacam CES displayed better reproducibility (r = 0.988) than UP (r = 0.969) and SM (r = 0.901). The mean CCT measurements of Pentacam CES and UP were not significantly different in group A (P = .37) and in eyes with mild keratoconus (P = .29), whereas significant differences between all instrument pairs were evident in group B and in moderate and severely keratoconic eyes (P<.05). Noncontact SM measurements were significantly smaller than those of Pentacam CES and UP in all groups (P<.05) when a measurement could be obtained. There were significant linear correlations between CCT measurements of Pentacam CES, UP, and noncontact SM in groups A, B, and mildly keratoconic eyes (P<.001). CONCLUSIONS: Results suggest that whereas Pentacam CES and UP may be used interchangeably in normal eyes in the clinical setting for the measurement of CCT, one should be cautious interpreting corneal thickness data from Pentacam CES, UP, and particularly SM in eyes with keratoconus. Whereas, in normal and mildly keratoconic eyes, Pentacam CES and UP demonstrated very high and comparable reproducibility, in moderately keratoconic eyes, Pentacam CES readings showed better reproducibility than UP.

Adolescent↗