Corneal changes following short-term rigid contact lens wear

Purpose: The aim of this cross-over study was to investigate the changes in corneal thickness, anterior and posterior corneal topography, corneal refractive power and ocular wavefront aberrations, following the short term use of rigid contact lenses. Method: Fourteen participants wore 4 different types of contact lenses (RGP lenses of 9.5 mm and 10.5 mm diameter, and for comparison a PMMA lens of 9.5 mm diameter and a soft silicone hydrogel lens) on 4 different days for a period of 8 h on each day. Measures were collected before and after contact lens wear and additionally on a baseline day. Results: Anterior corneal curvature generally showed a flattening with both of the RGP lenses and a steepening with the PMMA lens. A significant negative correlation was found between the change in corneal swelling and central and peripheral posterior corneal curvature (all p ≤ 0.001). RGP contact lenses caused a significant decrease in corneal refractive power (hyperopic shift) of approximately 0.5 D. The PMMA contact lenses caused the greatest corneal swelling in both the central (27.92 ± 15.49 μm, p < 0.001) and peripheral (17.78 ± 12.11 μm, p = 0.001) corneal regions, a significant flattening of the posterior cornea and an increase in ocular aberrations (all p ≤ 0.05). Conclusion: The corneal swelling associated with RGP lenses was relatively minor, but there was slight central corneal flattening and a clinically significant hyperopic change in corneal refractive power after the first day of lens wear. The PMMA contact lenses resulted in significant corneal swelling and reduced optical performance of the cornea.

Axial length changes with shifts of gaze direction in myopes and emmetropes

Purpose. The purpose of the study was to investigate the changes in axial length occurring with shifts in gaze direction. Methods. Axial length measurements were obtained from the left eye of 30 young adults (10 emmetropes, 10 low myopes, and 10 moderate myopes) through a rotating prism with 15° deviation, along the foveal axis, using a noncontact optical biometer in each of the nine different cardinal directions of gaze over 5 minutes. The subject's fellow eye fixated on an external distance (6 m) target to control accommodation, also with 15° deviation. Axial length measurements were also performed in 15° and 25° downward gaze with the biometer inclined on a tilting table, allowing gaze shifts to be achieved with either full head turn but no eye turn, or full eye turn with no head turn. Results. There was a significant influence of gaze angle and time on axial length (both P < 0.001), with the greatest axial elongation (+18 ± 8 μm) occurring with inferonasal gaze (P < 0.001) and a slight decrease in axial length in superior gaze (−12 ± 17 μm) compared with primary gaze (P < 0.001). In downward gaze, a significant axial elongation occurred when eye turn was used (P < 0.001), but not when head turn was used to shift gaze (P > 0.05). Conclusions. The angle of gaze has a small but significant short-term effect on axial length, with greatest elongation occurring in inferonasal gaze. The elongation of the eye appears to be due to the influence of the extraocular muscles, in particular the oblique muscles.

Monocular myopic defocus and daily changes in axial length and choroidal thickness of human eyes

Recent research indicates that brief periods (60 minutes) of monocular defocus lead to small but significant changes in human axial length. However, the effects of longer periods of defocus on the axial length of human eyes are unknown. We examined the influence of a 12 hour period of monocular myopic defocus on the natural daily variations occurring in axial length and choroidal thickness of young adult emmetropes. A series of axial length and choroidal thickness measurements (collected at ~3 hourly intervals, with the first measurement at ~9 am and the final measurement at ~9 pm) were obtained for 13 emmetropic young adults over three consecutive days. The natural daily rhythms (Day 1, baseline day, no defocus), the daily rhythms with monocular myopic defocus (Day 2, defocus day, +1.50 DS spectacle lens over the right eye), and the recovery from any defocus induced changes (Day 3, recovery day, no defocus) were all examined. Significant variations over the course of the day were observed in both axial length and choroidal thickness on each of the three measurement days (p<0.0001). The magnitude and timing of the daily variations in axial length and choroidal thickness were significantly altered with the monocular myopic defocus on day 2 (p<0.0001). Following the introduction of monocular myopic defocus, the daily peak in axial length occurred approximately 6 hours later, and the peak in choroidal thickness approximately 8.5 hours earlier in the day compared to days 1 and 3 (with no defocus). The mean amplitude (peak to trough) of change in axial length (0.030 ± 0.012 on day 1, 0.020 ± 0.010 on day 2 and 0.033 ± 0.012 mm on day 3) and choroidal thickness (0.030 ± 0.007 on day 1, 0.022 ± 0.006 on day 2 and 0.027 ± 0.009 mm on day 3) were also significantly different between the three days (both p<0.05). The introduction of monocular myopic defocus disrupts the daily variations in axial length and choroidal thickness of human eyes (in terms of both amplitude and timing) that return to normal the following day after removal of the defocus.

KPNA3 variation is associated with schizophrenia, major depression, opiate dependence and alcohol dependence

KPNA3 is a gene that has been linked to schizophrenia susceptibility. In this study we investigated the possible association between KPNA3 variation and schizophrenia. To investigate a wider role of KPNA3 across psychiatric disorders we also analysed major depression, PTSD, nicotine dependent, alcohol dependent and opiate dependent cohorts. Using a haplotype block-based gene-tagging approach we genotyped six KPNA3 single nucleotide polymorphisms (SNPs) in 157 schizophrenia patients, 121 post-traumatic stress disorder patients, 120 opiate dependent patients, 231 alcohol dependent patients, 147 nicotine dependent patients and 266 major depression patients. One SNP rs2273816 was found to be significantly associated with schizophrenia, opiate dependence and alcohol dependence at the genotype and allele level. Major depression was also associated with rs2273816 but only at the allele level. Our study suggests that KPNA3 may contribute to the genetic susceptibility to schizophrenia as well as other psychiatric disorders.

Factors affecting technical efficiency of rice farmers in village reservoir irrigation systems of Sri Lanka

Given the importance of water for rice production, this study examines the factors affecting the technical efficiency (TE) of irrigated rice farmers in village irrigation systems (VIS) in Sri Lanka. Primary data were collected from 460 rice farmers in the Kurunagala District, Sri Lanka, to estimate a stochastic translog production frontier for rice production. The mean TE of rice farming in village irrigation was found to be 0.72, although 63% of rice farmers exceeded this average. The most influential factors of TE are membership of Farmer Organisations (FOs) and the participatory rate in collective actions organised by FOs. The results suggest that enhancement of co-operative arrangements of farmers by strengthening the membership of FOs is considered important for increasing TE in rice farming in VIS.

‘Supersize me’ : on equine obesity

There’s nothing like travel to broaden the mind. As a young man living in Britain during the 1980s I thought I knew about human obesity, but it took a visit to the US to show me what an epidemic looks like. Nowadays I live in Australia, where human obesity is rife. We have plenty of fat horses too (Sillence et al., 2006), but they are noticeable. In fact, it was only recently during a return visit to Britain, that I was finally sold on the concept of an equine obesity epidemic. It seems that in the UK, the fat horse or pony is now so commonplace that it has come to represent the norm in the eyes of many owners. I met clinicians who claim to have forgotten what a fit horse looks like, and heard anecdotes of a responsible owner who kept their animals in a healthy body condition, only to be reported to the RSPCA for ‘cruelty’. Round and shiny have become the order of the day and, as we have learned from the tsunami of human obesity, once a problem reaches a certain scale it can seem unstoppable, despite the attendant risks, costs and consequences.

Near work-induced contrast adaptation in emmetropic and myopic children

Purpose. Contrast adaptation may induce an error signal for emmetropization. This research aims to determine whether reading causes contrast adaptation in children and, if so, to determine whether myopes exhibit greater contrast adaptation than emmetropes. Methods. Baseline contrast sensitivity was determined in 34 emmetropic and 34 spectacle-corrected myopic children for 0.5, 1.2, 2.7, 4.4, and 6.2 cycles per degree (cpd) horizontal sine-wave gratings. Effects of near tasks on contrast sensitivity were determined during periods spent looking at a 6.2 cpd horizontal grating and during periods spent reading lines of English text, with 1.2 cpd row frequency and 6 cpd stroke frequency. Results. Both emmetropic and myopic groups (mean ± SD; age, 10.3 ± 1.4 years) showed reduced contrast sensitivity during both near tasks, with greatest overall adaptation at 6.2 cpd. Adaptation induced by viewing the grating (0.15 ± 0.17 log unit [40%]; range, 0.07-0.27 log unit) was significantly greater than adaptation induced by reading text (0.11 ± 0.18 log unit [29%], 0.08-0.16 log unit) (F(1,594) = 10.7; P = 0.001). Myopic children showed significantly greater adaptation across the tasks (0.15 ± 0.18 log unit [42%]) than emmetropic children (0.10 ± 0.16 log unit [26%]) (F(1,66) = 7.30; P = 0.009), with the greatest difference occurring at 4.4 cpd (mean, 0.11 log unit [30%]). Conclusions. Grating and reading tasks induced contrast adaptation; viewing horizontal gratings induced greater adaptation than reading, and myopes exhibited greater adaptation than emmetropes. Contrast adaptation effects may underlie findings of prolonged near work being associated with myopia. However, our research does not show whether this is consequential or causal.

Identification of GABA receptors in chick cornea

Purpose: The cornea has an important role in vision, is highly innervated and many neurotransmitter receptors are present, e.g., muscarine, melatonin, and dopamine receptors. γ-aminobutyric acid (GABA) is the most important inhibitory neurotransmitter in the retina and central nervous system, but it is unknown whether GABA receptors are present in cornea. The aim of this study was to determine if GABA receptors are located in chick cornea. Methods: Corneal tissues were collected from 25, 12-day-old chicks. Real time PCR, western blot, and immunohistochemistry were used to determine whether alpha1 GABAA, GABAB, and rho1 GABAC receptors were expressed and located in chick cornea. Results: Corneal tissue was positive for alpha1 GABAA and rho1 GABAC receptor mRNA (PCR) and protein (western blot) expression but was negative for GABAB receptor mRNA and protein. Alpha1 GABAA and rho1 GABAC receptor protein labeling was observed in the corneal epithelium using immunohistochemistry. Conclusions: These investigations clearly show that chick cornea possesses alpha1 GABAA, and rho1 GABAC receptors, but not GABAB receptors. The purpose of the alpha1 GABAA and rho1 GABAC receptors in cornea is a fascinating unexplored question.

Comparative effects of posterior eye cup tissues from Myopic and Hyperopic chick eyes on cultured scleral fibroblasts

The role of individual ocular tissues in mediating changes to the sclera during myopia development is unclear. The aim of this study was to examine the effects of retina, RPE and choroidal tissues from myopic and hyperopic chick eyes on the DNA and glycosaminoglycan (GAG) content in cultures of chick scleral fibroblasts. Primary cultures of fibroblastic cells expressing vimentin and -smooth muscle actin were established in serum-supplemented growth medium from 8-day-old normal chick sclera. The fibroblasts were subsequently co-cultured with posterior eye cup tissue (full thickness containing retina, RPE and choroid) obtained from untreated eyes and eyes wearing translucent diffusers (form-deprivation myopia, FDM) or -15D lenses (lens-induced myopia, LIM) for 3 days (post hatch day 5 to 8) (n=6 per treatment group). The effect of tissues (full thickness and individual retina, RPE, and choroid layers) from -15D (LIM) versus +15D (lens-induced hyperopia, LIH) treated eyes was also determined. Refraction changes in the direction predicted by the visual treatments were confirmed by retinoscopy prior to tissue collection. Glycosaminoglycan (GAG) and DNA content of the scleral fibroblast cultures were measured using GAG and PicoGreen assays. There was no significant difference in the effect of full thickness tissue from either FDM or LIM treated eyes on DNA and GAG content of scleral fibroblasts (DNA 8.9±2.6 µg and 8.4±1.1 µg, p=0.12; GAG 11.2±0.6 µg and 10.1±1.0 µg, p=0.34). Retina from LIM eyes did not alter fibroblast DNA or GAG content compared to retina from LIH eyes (DNA 27.2±1.7 µg versus 23.2±1.5 µg, p=0.21; GAG 28.1±1.7 µg versus. 28.7±1.2 µg, p=0.46). Similarly, the choroid from LIH and LIM eyes did not produce a differential effect on DNA content (DNA, LIM 46.9±6.4 versus LIH 51.5±4.7 µg, p=0.31), whereas GAG content was higher for cells in co-culture with choroid from LIH eyes (GAG 32.5±0.7 µg versus 18.9±1.2 µg, F1,6=9.210, p=0.0002). In contrast, fibroblast DNA was greater in co-culture with RPE from LIM eyes than the empty basket and DNA content less for co-culture with RPE from LIH eyes (LIM: 72.4±6.3 µg versus Empty basket: 46.03±1.0 µg; F1,6=69.99, p=0.0005 and LIH: 27.9±2.3 µg versus empty basket: 46.03±1.0 µg; p=0.0004). GAG content was higher with RPE from LIH eyes (LIH: 33.7±1.9 µg versus empty basket: 29.5±0.8 µg, F1,6=13.99, p=0.010) and lower with RPE from LIM eyes (LIM: 27.7±0.9 µg versus empty basket: 29.5±0.8 µg, p=0.021). GAG content of cells in co-culture with choroid from LIH eyes was higher compared to co-culture with choroid from LIM eyes (32.5±0.7 µg versus 18.9±1.2 µg respectively, F1,6=9.210, p=0.0002). In conclusion, these experiments provide evidence for a directional growth signal that is present (and remains) in the ex-vivo RPE, but that does not remain in the ex-vivo retina. The identity of this factor(s) that can modify scleral cell DNA and GAG content requires further research.

Telehealth for nursing homes: the utilization of specialist services for residential care

Specialist care consultations were identified by two research nurses using documentation in patient records, appointment diaries, electronic billing services and on-site observations at a 441-bed long term care facility. Over a six-month period there were 3333 consultations (a rate of 1511 consultations per year per 100 beds). Most consultations were for general practice (n = 2589, 78%); these consultations were mainly on site (99%), with only 27 taking place off site. There were 744 consultations for specialities other than general practice. A total of 146 events related to an emergency or unplanned hospital admission. The remaining medical consultations (n = 598, 18%) related to 23 medical specialities. The largest number of consultations were for surgery (n = 106), podiatry (n = 100), nursing services including wound care (n = 74), imaging (n = 41) and ophthalmology (n = 40). Many services which are currently being provided on site to metropolitan long-term care facilities could be provided by telehealth in both urban and rural facilities.

Prevalence of papillary changes and folliculosis of the palpebral conjunctiva in asymptomatic Chinese children

Purpose To determine the prevalence of papillary changes of the upper palpebral conjunctiva and folliculosis of the lower palpebral conjunctiva in Chinese children with no history of contact lens wear. Method Ninety-nine subjects (aged 6–15 years old) who were interested in a myopia control study were screened for papillary changes and folliculosis of the palpebral conjunctiva. Photodocumentation was performed under white and blue light (after the application of fluorescein) with a yellow filter and the photographs were graded by a group of practitioners according to a pre-set grading scale. Analysis was performed with the subjects divided into groups according to gender and age. Results More than 48% of the subjects had clinically significant (≥Grade 3) papillary changes in the upper palpebral conjunctiva. The prevalence of significant folliculosis in the lower lid was about 33%. The prevalence of significant papillary changes and folliculosis were similar between genders. No differences were observed between younger (age ≤ 10 years old) and older (age > 10 years old) in papillary changes but younger subjects showed a higher prevalence of folliculosis. Conclusions The prevalences of clinically significant papillary changes and folliculosis of unknown aetiology are high in Chinese children.

Corneal changes following near work in myopic anisometropia

Purpose: To examine the symmetry of corneal changes following near work in the fellow eyes of non-amblyopic myopic anisometropes. Methods: Thirty-four non-amblyopic, myopic anisometropes (minimum 1 D spherical equivalent anisometropia) had corneal topography measured before and after a controlled near work task. Subjects were positioned in a headrest to minimise head movements and read continuous text on a computer monitor for 10 minutes at an angle of 25 degrees downward gaze and an accommodation demand of 2.5 D. Measures of the morphology of the palpebral aperture during primary and downward gaze were also obtained. Results: The more and less myopic eyes exhibited a high degree of interocular symmetry for measures of palpebral aperture morphology during both primary and downward gaze. Following the near work task, fellow eyes also displayed a symmetrical change in superior corneal topography (hyperopic defocus) which correlated with the position of the upper eyelid during downward gaze. Greater changes in the spherical corneal power vector (M) following reading were associated with narrower palpebral aperture during downward gaze (p = 0.07 for more myopic and p = 0.03 for less myopic eyes). A significantly greater change in J0 (an increase in against the rule astigmatism) was observed in the more myopic eyes (-0.04 ± 0.04 D) compared to the less myopic eyes (-0.02 ± 0.06 D) over a 6 mm corneal diameter (p = 0.01). Conclusions: Changes in corneal topography following near work are highly symmetrical between the fellow eyes of myopic anisometropes due to the interocular symmetry of the palpebral aperture. However, the more myopic eye exhibits changes in corneal astigmatism of greater magnitude compared to the less myopic eye.

Comparison of antigen detection and quantitative PCR in the detection of chlamydial infection in koalas (Phascolarctos cinereus)

The gold standard method for detecting chlamydial infection in domestic and wild animals is PCR, but the technique is not suited to testing animals in the field when a rapid diagnosis is frequently required. The objective of this study was to compare the results of a commercially available enzyme immunoassay test for Chlamydia against a quantitative Chlamydia pecorum-specific PCR performed on swabs collected from the conjunctival sac, nasal cavity and urogenital sinuses of naturally infected koalas (Phascolarctos cinereus). The level of agreement for positive results between the two assays was low (43.2%). The immunoassay detection cut-off was determined as approximately 400 C. pecorum copies, indicating that the test was sufficiently sensitive to be used for the rapid diagnosis of active chlamydial infections.

Antigenic specificity of a monovalent versus polyvalent MOMP based Chlamydia pecorum vaccine in koalas (Phascolarctos cinereus)

Chlamydia continues to be a major pathogen of koalas. The bacterium is associated with ocular, respiratory and urogenital tract infections and a vaccine is considered the best option to limit the decline of mainland koala populations. Over the last 20 years, efforts to develop a chlamydial vaccine in humans have focussed on the use of the chlamydial major outer membrane protein (MOMP). Potential problems with the use of MOMP-based vaccines relate to the wide range of genetic diversity in its four variable domains. In the present study, we evaluated the immune response of koalas vaccinated with a MOMP-based C. pecorum vaccine formulated with genetically and serologically diverse MOMPs. Animals immunised with individual MOMPs developed strong antibody and lymphocyte proliferation responses to both homologous as well as heterologous MOMP proteins. Importantly, we also showed that vaccine induced antibodies which effectively neutralised various heterologous strains of koala C. pecorum in an in vitro assay. Finally, we also demonstrated that the immune responses in monovalent as well as polyvalent MOMP vaccine groups were able to recognise whole chlamydial elementary bodies, illustrating the feasibility of developing an effective MOMP based C. pecorum vaccine that could protect against a range of strains.