Analysis of tear film breakup on Etafilcon A hydrogel lenses.

PURPOSE: There is a need to understand better the biomaterial characteristics responsible for tear film stability during hydrogel lens wear. The underlying cause of pre-lens tear film instability may be indicated by the distribution of sites of breakup. The purpose of this study was to compare the distribution of rupture sites during wear of a common biomaterial to that without lenses. METHODS: A videokeratography unit, the Topographic Modeling System, was used to capture an image of the tear film at the moment of breakup. Forty measurements were made for each of ten subjects, and the resultant rupture site distributions evaluated. The pre-lens tear film breakup locations were studied for Acuvue (Etafilcon A) disposable contact lenses using the same technique. RESULTS: There was a statistically significant trend for pre-corneal tear film breaks to occur more commonly in parameniscal zones than in areas overlying the central cornea (ANOVA, p = 0.002). With the Etafilcon A lenses, a significant difference in breakup frequency between the two regions was not observed. CONCLUSIONS: The pre-corneal tear film findings are consistent with the meniscus model of tear film stability; however, the biomaterial surface characteristics of Etafilcon A give other factors a more dominant role in tear film rupture.

Relationship between tear-meniscus parameters and tear-film breakup.

PURPOSE: Several flaws exist with the lipid-diffusion model for tear-film breakup. The aim of this study was to test an alternative model of tear-film rupture in which the negative hydrostatic pressure in each tear meniscus (related to the tear-meniscus radius of curvature) is proposed to influence the formation of breaks in the tear film. METHODS: Measurements of noninvasive breakup time (NIBUT) and tear-meniscus radius of curvature, height, width, and cross-sectional area (TMC, TMH, TMW, and XSA) were made for 15 aqueous-deficient dry-eye and 15 age-matched control subjects. An optic section of the inferior tear meniscus (colored with a minute volume of fluorescein) was photographed at x120 magnification, and images were computer analyzed. RESULTS: A significant positive correlation was found between log NIBUT and TMC (r2 = 0.141; p < 0.05). Furthermore, all subjects with TMC < 0.340 mm had NIBUT < 15 s, and two thirds of subjects with TMC > 0.340 mm had NIBUT > 15 s. There was a moderate linear relationship between TMH and log NIBUT, indicating an association between tear volume and tear stability. TMC, TMH, and tear meniscus XSA measurements all showed good reliability. CONCLUSIONS: The association between highly curved tear menisci and rapid tear-film breakup times is consistent with the meniscus model of tear-film rupture. However, a causal relationship has yet to be established.

Tear meniscus measurement in the diagnosis of dry eye.

PURPOSE: Assessment of the tear film meniscus is a quantitative, minimally invasive, direct measurement of tear film quantity. The aim of this study was to assess the efficacy of tear meniscus parameter measurement in the diagnosis of dry eye. METHODS: Tear meniscus radius of curvature, height, width and cross-sectional area (TMC, TMH, TMW, XSA) were determined by photographing an optic section of the inferior tear meniscus (colored with a min volume of fluorescein) at 12 x magnification, and then scanning developed images into a computer analysis program. Fifteen dry eye subjects and 15 age-matched controls were assessed. Dry eye subjects satisfied the criteria of a rose bengal staining score >/= 1, and a mean phenol red thread 15s wetted length

Soft lens movement: effect of blink rate on lens settling.

Little is understood about the mechanism by which soft lenses settle on the eye, although it has been suggested that lens base curve, steepening with in-eye lens dehydration or tear film changes may influence lens movement in the initial period of wear. In this study, we investigated the role of postlens tear fluid expulsion by assessing lens movement in 20 subjects wearing 38% water content hydrogel lenses for 10 min under three different conditions: 10 blinks/min, 30 blinks/min and eye closure. Over the 10 min wearing period, the total decrease in median lens movement for the 10 blinks/min condition was 0.07 mm, which was not a significant change (Friedman ANOVA, p = 0.13), while significant decreases occurred with conditions of 30 blinks/min (0.19 mm, p = 0.004) and eye closure (0.43 mm, p = 0.0001). As expected, lens movement under the three conditions was the same at insertion, but was significantly higher thereafter for the slower blink rate condition compared to the faster blink rate or eye closure conditions (Wilcoxon test, Z = 2.8 and -3.0, p = 0.006 and 0.003, respectively). Based on these findings, we postulate the model that the extent of lens settling and the degree of postinsertion lens movement are determined by the timeaverage pressure for postlens tear film expulsion exerted on the lens by the eyelids.

Analysis of transcription and estrogen insensitivity in the female mouse after targeted disruption of the estrogen receptor gene.

We employed homologous recombination in mouse embryonic stem cells to disrupt the estrogen receptor (ER) gene. Subsequently generated mice that are homozygous for the gene disruption, termed ERKO, possess no demonstrable wild-type ER by Western blot analysis. However, the presence of residual high affinity binding, as detected by [3H]estradiol binding assays and sucrose gradients in uterine extracts from ERKO females prompted further investigation of transcription and translation products from the disrupted ER gene. Analysis of ERKO uterine messenger RNA (mRNA) by reverse transcriptase-polymerase chain reaction demonstrated that although no full-length wild-type ER mRNA was present, two smaller transcripts, labeled E1 and E2, were identified and partially sequenced. Both ERKO transcripts are splicing variants that result in the disrupting NEO sequence being partially or completely removed from the mRNA. In the ERKO-E2 variant, this results in a frame shift and the creation of at least two stop codons downstream. In the ERKO-E1 variant, the ER reading frame is preserved and encodes for a smaller mutant ER that could be the source of the residual estradiol binding. When this mutant form is overexpressed and characterized in vitro, it results in a smaller protein of the predicted size that possesses significantly reduced estrogen-dependent transcriptional activity compared with that of the wild-type ER. Despite residual amounts of an impaired ER variant, estrogen insensitivity in the female ERKOs was confirmed by the failure of estrogen treatment to induce known uterine markers of estrogen action, such as increased DNA synthesis, and transcription of the progesterone receptor, lactoferrin, and glucose-6-phosphate dehydrogenase genes. Furthermore, serum levels of estradiol in the ERKO female are more than 10-fold higher than those in the wild type, consistent with a syndrome of hormone insensitivity.

Soft lens movement: effects of humidity and hypertonic saline on lens settling.

Hydrogel contact lenses require a settling period before lens fit stabilizes, but the process underlying the initial reduction in lens mobility is poorly understood. Explanations for this phenomenon include base curve steeping with dehydration, expulsion of postlens tear fluid, and osmotic flow of hypotonic tears into the cornea. We conducted two randomized, single-masked interocular comparisons for ten subjects wearing HEMA lenses for 1 h. We investigated potential mechanisms of dehydration-dependent lens tightening, by limiting dehydration in one eye using a high humidity environment (experiment 1), and of a hypotonic lacrimation-dependent decrease in lens movement, by presoaking lenses in isotonic (0.9%) or hypertonic (1.5%) saline (experiment 2). Lens mobility profiles were not significantly affected by modification of environment; lenses in both normal and high humidity environments displayed a significant reduction in lens movement during the first 15 min of wear (ANOVA, p = 0.0001), and no change in lens mobility thereafter. Lens mobility profiles were identical for lenses presoaked in isotonic and hypertonic saline, with initial lens movement being significantly greater than for subsequent measurements (ANOVA, p < 0.05). These studies find no evidence to support dehydration-dependent steepening of base curve, or osmotic-dependent binding from hypotonic lacrimation as mechanisms for the initial postinsertion decrease in lens movement.

Soft lens movement: temporal characteristics.

The time-course of on-eye hydrogel lens movement has not been carefully scrutinized, despite the importance of lens movement in optimizing lens fit and corneal physiology. We conducted a study to define the time-course of soft lens movement using 26 subjects. Video slitlamp recordings were made of lens movement at 5-min intervals for 30-min wear and after 8-h wear of 38 or 67% water content lenses (N = 14 and 12, respectively). Lens mobility profiles were statistically indistinguishable for high and low water content lenses, and for experienced and neophyte lens wearers. Lens movement displayed biphasic temporal characteristics, decreasing significantly over the first 25 min from a median of 0.6 to 0.3 mm (Wilcoxon matched-pairs signed-rank test, p = 0.002), then increasing significantly to 0.5 mm after 8 h of wear (p = 0.03). Although some subjects exhibited little alteration in lens movement, 31% showed a decrease in lens movement > 0.25 mm during the first half-hour of wear. Optimal predictability of lens mobility after 8-h wear was achieved 5 min after insertion, with 77% of subjects displaying lens movement within +/- 0.25 mm of the final value. In-office assessment of lens movement is best achieved 5 min after insertion, although clinical and real world lens mobility will differ significantly in about one in four patients.

X-ray and scanning electron microscopic analysis of the structural composition of tear ferns.

Dried tears from keratoconjunctivitis sicca eyes fail to exhibit the fern-like crystallization patterns observed with tears from eyes with normal tear function. To test our hypothesis that the extent of ferning depends on the ratio of salts to protein and mucin in the tear sample, dried tears from six normal subjects were subjected to scanning electron microscopy (SEM) and X-ray analyses. X-ray diffraction identified sodium chloride and potassium chloride as the major components of tear fern crystals. X-ray fluorescence detected the elements potassium, chlorine, calcium, and sulfur in the dried tear samples, with sulfur indicating the presence of protein and/or mucin. As well as confirming the presence of cubic fern nuclei, SEM revealed two kinds of material, having crystalline and globular appearances, that are hypothesized to be composed of salts and protein/mucin, respectively. Globular material appeared to block extension of crystal fern arms or to coat crystalline material, but did not crystallize. These findings suggest that tear fern crystals are composed of sodium and potassium chloride, with proteinaceous material controlling crystallization indirectly by coating crystal faces and blocking fern extension. This structural composition is consistent with the hypothesis that the ratio of salt to macromolecular species is an important determinant of tear ferning.

Alteration of reproductive function but not prenatal sexual development after insertional disruption of the mouse estrogen receptor gene.

Estrogen receptor and its ligand, estradiol, have long been thought to be essential for survival, fertility, and female sexual differentiation and development. Consistent with this proposed crucial role, no human estrogen receptor gene mutations are known, unlike the androgen receptor, where many loss of function mutations have been found. We have generated mutant mice lacking responsiveness to estradiol by disrupting the estrogen receptor gene by gene targeting. Both male and female animals survive to adulthood with normal gross external phenotypes. Females are infertile; males have a decreased fertility. Females have hypoplastic uteri and hyperemic ovaries with no detectable corpora lutea. In adult wild-type and heterozygous females, 3-day estradiol treatment at 40 micrograms/kg stimulates a 3- to 4-fold increase in uterine wet weight and alters vaginal cornification, but the uteri and vagina do not respond in the animals with the estrogen receptor gene disruption. Prenatal male and female reproductive tract development can therefore occur in the absence of estradiol receptor-mediated responsiveness.

Evaluation of interventions to improve solar protection in primary schools.

Childhood and adolescence are critical periods in the etiology of subsequent melanoma and nonmelanocytic skin cancers. The aims of the study were (a) to develop a valid measure of solar protection in 9 to 11-year-old school students, (b) to evaluate the differential effectiveness of two interventions aimed at changing solar protection in this age group, and (c) to identify the predictors of use of a high level of solar protection. A Solar Protection Behavior Diary was developed and validated during a pilot, after which 11 schools were randomly allocated to one of three groups: intensive intervention (247 students), standard intervention (180 students), or control (185 students), with students in years 5 and 6 participating in the study. Students completed the validated diary (for 5 days) and a knowledge and attitudes questionnaire at pretest and at two posttest periods (4 weeks and 8 months after pretest). Results indicated that students in the intensive intervention group were significantly more likely to have used a high level of protection at both posttest periods compared to the control and standard intervention groups. There was no difference in the protection level of the control and standard intervention groups at either posttest, indicating that this minimal intervention was not effective in changing the solar protection behavior of the students. Students with a high level of solar protection at pretest were also significantly more likely to have a high level of protection at both posttest periods, and those with a greater number of opportunities to protect were less likely to protect at the second posttest.

Effect of hydrogel lens wear on tear film stability.

Noninvasive break-up time (NIBUT) of the tears was measured in a controlled, randomized, double-masked study to assess: (1) the stability of the prelens tear film during wear of new high and low water content lenses and (2) the stability of the precorneal tear film following lens removal after 1 h of wear. The prelens tear film NIBUT of 6 subjects was found to be relatively constant over a 1-h wearing period, averaging 6.1 +/- 1.1 s (mean +/- SEM). These values were significantly (Scheffe's S test, p less than 0.05) lower than those recorded for the precorneal tear film before lens insertion (33.5 +/- 10.6; mean +/- SEM), although 85% of prelens tear film NIBUT's were greater than the 3-s average interblink period reported previously for soft lens wearers. After lens removal, precorneal tear film NIBUT was reduced significantly compared to prewear levels (Scheffe's S test, p less than 0.05) for up to 15 min. Application of the monomolecular growth model to the NIBUT recovery data revealed a half-time for recovery of 6.0 min, with recovery 95% complete 25.8 min after lens removal. Lens type was not a significant factor in tear film stability, either during wear or after lens removal. The basis for reduced precorneal tear film NIBUT after lens removal is unknown; however, a disruption of the mucin layer coating the corneal epithelium is the most likely mechanism. Indeed, the technique of measuring precorneal tear film NIBUT after lens removal may be a useful determinant of the extent to which contact lens wear disrupts the precorneal mucin layer, providing an indication of the susceptibility of the cornea to a variety of complications.

The effect of soft lens lubricants on symptoms and lens dehydration.

In order to establish the efficacy of soft lens lubricants and their mode of action, we conducted a controlled, double-masked, randomized study. Symptoms of dryness as well as lens water content were assessed in 30 symptomatic hydroxyethylmethacrylate (HEMA) contact lens wearers who each applied either saline or one of two soft lens lubricants every 2 hours over a 6-hour wearing period. Short- and long-term symptomatic relief from ocular dryness was provided by both lens lubricants (ANOVA, P less than .05). However, neither lubricant was found to be significantly superior to saline. Contact lens dehydration was not significantly reduced by the instillation of any solution. A psychological rather than a physical (lens hydration) or physiological basis to the symptomatic relief provided by soft lens lubricants cannot be discounted.

Childhood peptic ulcer disease in Jamaica.

Thirty-one children with peptic ulcer disease (PUD) were diagnosed in two major hospitals in Jamaica between 1979 and 1988. There were 21 girls and 10 boys with a mean age of 9 years. There were 26 duodenal ulcers and 5 gastric ulcers. Five patients (19 per cent) with a duodenal ulcer had a family history of peptic ulcer. Recurrent abdominal pain was the predominant presenting feature in 68 per cent and pain was present for a mean of 20 months. Bleeding occurred in seven patients (23 per cent). Twenty-nine patients were successfully treated medically. Two with duodenal ulcers required surgery. The majority of patients have remained well after a mean follow-up of 14 months. Although uncommon in children peptic ulcers should be considered in patients with recurrent abdominal pain. The majority will respond to medical treatment.

Soft lens lubricants and prelens tear film stability.

Soft contact lens wearers complaining of "dry eye" are frequently prescribed rewetting drops, although the mode of action and efficacy of this treatment have not been established. Enhancement of prelens tear film (PLTF) stability could provide a basis for symptomatic relief with solution instillation. Thirty symptomatic hydroxyethyl methacrylate (HEMA) lens wearers participated in 4 separate trials of no solution (baseline), saline, and 2 soft lens lubricants. Solutions were applied for a 6-h adaptation period, and PLTF noninvasive break-up time (NIBUT) was monitored for 1 h after a final instillation. PLTF NIBUT was significantly elevated 1 min after instillation of all solutions (p less than 0.001, logrank test) but this effect persisted for less than 5 min. The transient enhancement of PLTF stability arising from the instillation of these rewetting solutions is unlikely to provide a basis for prolonged symptomatic relief.

Bimodal nuclear estrogen receptor binding: synchrony in athymic mouse uterus and human breast tumor xenografts.

Human MCF-7 tumors were transplanted into ovariectomized female athymic nude mice supplemented with estradiol pellets. Ten days after hormone pellet removal, the animals were treated with 10 micrograms/kg estradiol, and the nuclear estrogen receptor (ERn) profile was assessed by the exchange assay. The pattern in the tumors was qualitatively similar to that in the uterus. A bimodal pattern of ERn was seen, with peaks at 1 and 8 h. Further biochemical analysis of uterine samples showed that both peaks were comprised of similar levels of salt-resistant ERn forms. Scatchard plot analysis of estradiol binding demonstrated high affinity receptors (Kd = 0.73-0.86 nM) as components of both peaks. In the ovariectomized adult rat there was also a bimodal pattern of ERn 1 and 13-14 h after the injection of 20 micrograms/kg estradiol. Direct hormone stimulation of the uterus was achieved with intraluminal (IL) injection of estradiol. IL injections of estradiol (100-800 pg/horn) stimulated uterine DNA synthesis compared to IL saline injections in the contralateral horn. IL injection of 200 pg/horn estradiol resulted in a bimodal pattern of ERn at 3 and 9 h. These data indicate that a bimodal pattern of ERn is present in estrogen target tissues exhibiting a growth response.

Estradiol-stimulated proteolytic cleavage of the estrogen receptor in mouse uterus.

Increased proteolytic degradation of the estrogen receptor (ER) was detected in uterine cytosol of estradiol-treated ovariectomized mice compared to saline controls. Estradiol had no direct effect on the proteinase activity or susceptibility of the ER to the enzyme. The proteolytic activity gradually increased after a single injection of estradiol with early increases at 2 and 8 h followed by a progressive increase which reached a maximum at 36 h. The proteinase(s) activity resulted in cleavage of the native ER form of 65,000 (65 K ER) to a product of limited proteolysis having an apparent molecular weight of 54,000 (54 K ER). The pH optimum for this proteinase activity was 6.0. The proteinase was inhibited by 2.5 mM p-chloromercuribenzoic acid and 2.5 mM p-chloromercuriphenylsulfonate and partially inhibited by 2.5 mM iodoacetamide but not by 1 mg/ml leupeptin, 0.1 mg/ml antipain, 0.1 mg/ml chymostatin, 0.1 mg/ml pepstatin, 0.1 mg/ml E-64, 2.5 mg/ml soybean trypsin inhibitor, 2.5 mM phenylmethylsulfonylfluoride, 2.5 mM diisopropylfluorophosphate, and 10 mM EGTA. The results suggested that the proteinase(s) had a thiol group essential for its activity. Estrogen receptor in the mouse uterine cytosol fraction appears to be degraded sequentially in two steps in which 65 K ER is cleaved to a 54 K ER which upon longer incubation is further degraded to a 37 K form. The second step was inhibited by leupeptin, antipain, chymostatin, E-64, and p-chloromercuribenzoic acid. A possible function of the 54 K ER under physiological conditions is discussed since the 54 K ER was also found in nuclear samples. This form of the ER still retains the ability to bind estradiol and DNA.