The effects of prostaglandin F2α in the human eye

The ocular effects of 200 g of topically applied prostaglandin F₂ were studied in 18 nonglaucomatous volunteers. A fall in intraocular pressure was seen in the prostaglandin-treated eyes when compared with the placebotreated control eyes. The maximum intraocular pressure reduction was observed at the 7th h and hypotensive ocular effect persisted for 24 h. Prostaglandins did not produce any change in pupillary diameter or signs of intraocular inflammation visible by anterior segment biomicroscopy or iris fluorescein angiography. The drug caused side effects: conjunctival hyperemia was constant and many patients complained of ocular smarting and headache. It could be useful in the treatment of ocular hypertension, although its usefulness would be limited by the side effects.     

The evaluation of chosen cytokines in induction of ocular changes in Sjögren's syndrome of dry eye

PURPOSE: To evaluate the role of pro-inflammatory cytokines interleukin-8 (IL-8) and interferon-gamma (IFN-gamma) in pathogenesis of Sjogren's syndrome of dry eye (SS--dry eye), and in induction of ocular changes in this disease. MATERIAL AND METHODS: Tear samples were collected from 25 patients with Sjogren's syndrome of dry eye and 33 healthy volunteers. Cytokine levels were determined by ELISA. Ophthalmic examinations, including tests for dry eye, were used to study the ocular surface. The levels of these cytokines in tears and dry eye findings were compared. RESULTS: The tears level of IL-8 and IFN-gamma in SS--dry eye patients were significantly higher than those in controls. We found positive correlation between the tears levels of pro-inflammatory cytokines and dry eye findings (subjective and objective assessments and diagnostic tests). CONCLUSIONS: The elevated level of pro-inflammatory cytokines in tears fluid of patients with Sjogren's syndrome of dry eye may be important factor in the pathogenesis of this disease. Significant correlation between tears level of cytokines and dry eye findings suggest, that these cytokines induce inflammatory changes of ocular surface in Sjogren's syndrome of dry eye.     

The effects of β-adrenergic agonists on cone systems in the cat eye

The effects of the -adrenergic agonist nylidrin and the ₂-adrenergic agonist clenbuterol on electroretinogram and optic nerve response were studied in the isolated and arterially perfused, light-adapted cat eye. Two cone mechanisms, short wavelength-sensitive and long wavelength-sensitive, were functionally separated by means of intense yellow adaptation. A reversible increase in b-wave amplitude in response to nylidrin or clenbuterol was observed for the cone systems. Both drugs also caused a reversible alteration in configuration of the optic nerve response, mainly a depression of the late components related in time to the changes in the electroretinogram. These observations suggest that -adrenergic mechanisms are involved in cone systems. The greater increase in b-wave amplitude on 558-nm stimulation and preliminary evidence for greater increase in sensitivity observed in the V-log I function compared with 439 nm further suggest that the short and long wavelength cone systems are affected differently by -adrenergic agonists.     

What is the best fixation target? The effect of target shape on stability of fixational eye movements

People can direct their gaze at a visual target for extended periods of time. Yet, even during fixation the eyes make small, involuntary movements (e.g. tremor, drift, and microsaccades). This can be a problem during experiments that require stable fixation. The shape of a fixation target can be easily manipulated in the context of many experimental paradigms. Thus, from a purely methodological point of view, it would be good to know if there was a particular shape of a fixation target that minimizes involuntary eye movements during fixation, because this shape could then be used in experiments that require stable fixation. Based on this methodological motivation, the current experiments tested if the shape of a fixation target can be used to reduce eye movements during fixation. In two separate experiments subjects directed their gaze at a fixation target for 17 s on each trial. The shape of the fixation target varied from trial to trial and was drawn from a set of seven shapes, the use of which has been frequently reported in the literature. To determine stability of fixation we computed spatial dispersion and microsaccade rate. We found that only a target shape which looks like a combination of bulls eye and cross hair resulted in combined low dispersion and microsaccade rate. We recommend the combination of bulls eye and cross hair as fixation target shape for experiments that require stable fixation.     

The eyes of a tiny ‘Orsten’ crustacean – A compound eye at receptor level?

Among the oldest fossil crustaceans are those of the Late Cambrian (Furongian 499 ± 0.3–488.3 ± 1.7 Ma) of Västergötland, central Sweden and the lower Ordovician (Tremadocian 488.3 and 478.6 Ma) of the island of Őland. These are three-dimensionally preserved in nodules from the so called ‘stinkstone’ (‘Orsten’) limestone. ‘Orsten’-like fossils represent tiny, often meiobenthic organsisms (Haug, Maas, & Waloszek, 2009) smaller than 2 mm, which mainly were arthropods, especially crustaceans close to the stemline. As a result of phosphatisation, hairs, bristles and even cellular structures up to 0.3 μm are preserved (Walossek, 1993), especially compound eyes, as typical for all visually orientated crustaceans (Schoenemann et al., 2011). We show a miniscule prototype of a compound eye (∼40 μm) in a small crustacean, which lived almost half a billion years ago. The eye is close to but comfortably established above being limited in its resolving power by diffraction, but it is too small to be an apposition eye, normally regarded as the basal form of all compound eyes, as is found in bees, dragonflies, crustaceans and many other arthropods still living today. The facets of this compound eye are ∼8 μm in size, the surface structure indicates the relicts of a tiny lens covering each facet. In order to work functionally and to ensure that that diffraction and waveguide problems were avoided, it seems reasonable to suppose that the compound eye consisted of visual units, each with a single photoreceptor cell directly below a weak lens for capturing and slightly focusing the light. The entire unit has a diameter similar to that of a normal sensory cell as found in compound eyes. Thus, the early compound eye analysed here may be interpreted as a prototype representing the earliest stages of the evolution of crustacean compound eyes.     

The role of amniotic membrane extract eye drop (AMEED) in in vivo cultivation of limbal stem cells

Background

Limbal stem cell transplantation (LSCT) is the definitive treatment for total limbal stem cell deficiency (LSCD). This study evaluates the anatomical and visual outcomes of a surgical technique supplemented by amniotic membrane extract eye drop (AMEED) for in vivo cultivation of limbal stem cells (LSCs).

The top 100 papers in dry eye – A bibliometric analysis

Purpose

Citation analysis represents one of the best currently available methods for quantifying the impact of articles. Bibliometric studies list the ‘‘best sellers’’ in a single field of interest. The purpose of the present study was to identify and analyze the most frequently cited papers in dry eye research that may be of high interest for researchers and clinicians.

Non-concordance in amblyopia treatment: The effective use of ‘smileys’

PURPOSE The success of any specific occlusion regimen is limited by the level of concordance, which is difficult to measure accurately in patching treatment. The aim of this study was to investigate prospectively the concordance rate of a group of children with strabismic and/or anisometropic amblyopia using a schematic diary based on completing ‘smiley’ images, filled in by the child under parental supervision, and to assess the effect of correlates such as initial visual acuity, age, and total and daily occlusion time on concordance. METHODS We recruited 51 amblyopic children aged 13 months to 12 years (mean 6.57 ± 2.82). The median duration of treatment was 16 weeks. Non-concordance was defined as occluding less than 75% of the prescribed time and was analyzed using a concordance index calculated from occlusion time recorded in the diary / prescribed occlusion time. RESULTS Of the 51 patients followed prospectively, 12 (23.5%) failed to return their diaries (Group 1); 27 (52.9%) complied with occlusion (Group 2); and 12 (23.5%) failed to comply with occlusion completely (Group 3). The total proportion of non-concordance was 47.1% (Group1 + Group 3). Concordance was not significantly related to initial visual acuity (r = -0.22, p = 0.19), patient age (F = 1.0787, p = 0.349) or total occlusion time (X 2 = 2.779, p = 0.249), but the number of daily occlusion hours showed significant difference in Group 1 (X 2 = 15.894, p = 0.000). When the three groups were compared for change in visual acuity, a significant difference was found between group 1 and group 2 (X 2 = 6.125, p = 0.047). CONCLUSION The substantial proportion of non-concordance in our study suggests that, although useful for recording purposes, parental diaries may not be stimulating enough to increase the overall level of concordance. Therefore, other forms of monitoring need to be explored.     

Is manual counting of corneal endothelial cell density in eye banks still acceptable? The French experience

AIM: To examine the differences in manual endothelial cell counting methods in French eye banks and to analyse whether these differences could explain some substantial discrepancies observed in endothelial cell density (ECD) for corneas made available for transplant. METHODS: A questionnaire was sent to the 22 eye banks asking for details of the technical features of the light microscopes used, the microscope calibration, strategy for cell counting, the technical staff, and the method of presenting endothelial data. RESULTS: All eye banks responded and 91% (20/22) used only manual counting methods, in real time, directly through a microscope, and 62 different technicians, with varying experience, were involved in such counting. Counting of cells within the borders of a grid that were in contact with two adjacent borders was the most common method (17/22, 77%). Of the eight banks (8/22, 36%) that did not calibrate their microscopes, six reported the highest ECD values. Of the 14 others (64%), six applied a "magnification correcting factor" to the initial cell counts. In five of these cases, the corrected ECD was lower than estimated on initial count. Most of the banks (12/22, 55%) counted 100 cells or less in one to six non-adjacent zones of the mosaic. 14 of the banks (14/22, 64%) also graded cell polymegethism while seven (7/22, 32%) also graded pleomorphism ("hexagonality"). CONCLUSIONS: Lack of microscope calibration appears to be the leading cause of variance in ECD estimates in French eye banks. Other factors such as differences in counting strategy, the evaluation of smaller numbers of cells, and the different extent of experience of the technicians may also contribute to intraobserver and interobserver variability. Further comparative studies, including cross checking and the outcome of repeated counts from manual methods, are clearly needed with cross calibration to a computer based image archiving and analysis system.     

Sodium hyaluronate eye drops of different osmolarity for the treatment of dry eye in Sjögren's syndrome patients

AIM: To study the effect of the treatment of dry eye in Sj?gren's syndrome patients with hypotonic or isotonic hyaluronate eye drops. METHODS: 40 Sj?gren's syndrome patients were divided in two groups and treated as follows: group 1 with hypotonic (150 mOsm/l) 0.4% hyaluronate eye drops; group 2 with isotonic 0.4% hyaluronate eye drops. The eye drops were instilled six times a day for 90 days. Grading of subjective symptoms, break up time (BUT), corneal fluorescein staining, conjunctival rose bengal staining, Schirmer's I test, and conjunctival impression cytology were carried out at 0 and 15, 30, 90 days from the beginning of the study. Patients were examined in a blind fashion. For the statistical analysis the Student's t test, Mann-Whitney U test, and chi(2) test were performed. RESULTS: Symptoms were statistically significantly improved at day 15 in both groups but group 1 patients had a global score statistically significantly better group 2 (p=0.02). At day 15 group 1 patients had an improvement from baseline values of BUT (p=0.003), fluorescein, and rose bengal score (p=0.000001 and p=0.0004 respectively). Group 2 patients had, at day 15, an improvement of BUT and fluorescein score compared to baseline values (p=0.05 and p=0.0001 respectively). A comparison between the two groups showed better results for group 1 patients at day 15 for rose bengal stain (p=0.01) and for BUT (p=0.05) and fluorescein score (p=0.0003) at day 90. The conjunctival impression cytology showed that group 1 had a statistically significant better total score than group 2 starting from day 15 and lasting throughout the study (p<0.02). Also group 2 patients showed an improvement from baseline values starting from day 30 (p=0.000005). CONCLUSION: Hyaluronate eye drops are useful for treating severe dry eye in Sj?gren's syndrome patients. The use of a formulation with pronounced hypotonicity showed better effects on corneoconjunctival epithelium than the isotonic solution.     

How red is a white eye? Clinical grading of normal conjunctival hyperaemia

PURPOSE: To quantify the level of normal bulbar conjunctival hyperaemia using the Cornea and Contact Lens Research Unit (CCLRU) grading scale, and to investigate inter-observer agreement. METHODS: Bulbar conjunctival hyperaemia was assessed by two trained observers, using the CCLRU grading scale (zero to four units) interpolated into 0.1 increments, on the right eye of 121 healthy, non-contact lens-wearing subjects (male=58, female=63, median age=28 years, range 16-77). The eye was observed using a slit-lamp bio-microscope (x 10 magnification) under diffuse, white illumination. The subject's position of gaze was directed to allow grading of four quadrants: superior, nasal, inferior, and temporal conjunctiva. Bulbar redness was defined as the average of those four grades of conjunctival hyperaemia. A further twenty subjects were recruited to assess inter-observer agreement (male=8, female=12, median age=23 years). RESULTS: The average bulbar redness was 1.93 (+/-0.32 SD) units. The nasal (2.3+/-0.4) and temporal (2.1+/-0.4) quadrants were significantly redder than the superior (1.6+/-0.4) and inferior (1.7+/-0.4) quadrants (P<0.0001). Males had redder eyes than females by 0.2 units. Inter-observer 95% limits of agreement for bulbar redness was 0.38 units. CONCLUSIONS: The average bulbar redness of 1.9 units was higher than expected, reflecting the design of the grading scale. A bulbar redness of greater than 2.6 units may be considered abnormal, and a change in bulbar redness of > or =0.4 units may be significant.     

How can artificial eye motility be improved? The influence of fornix configuration and tissue thickness in front of hydroxyapatite-silicon implants in 66 patients

Porous hydroxyapatite of various origins has proven to be a suitable material for orbital volume replacement. Its biocompatibility surpasses all other options. The transmitted motility to the artificial eye has nevertheless, not always been to the full satisfaction of patients, oculists and ophthalmologists. Our study has shown a strong correlation between the depth of the superior and interior fornices as well as the thickness of tissue material covering the implant anterior surface.