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Understanding the impact of a health care voucher scheme and service access barriers could facilitate optometry service promotion to the older population.A voucher is one strategy to improve the utilisation of the different health care services available in the private sector. This study aims to explore how a health care voucher system for older people impacts utilisation of optometry services from the perspective of service users and service providers.People aged 65 years or above were recruited to fill in a structured questionnaire studying the usage characteristics and access barriers of optometry services and the health care voucher. Views from the optometrists about the voucher scheme were collected by questionnaire.A total of 1156 valid questionnaires from eligible voucher users was collected. Results showed that 53.7% (621/1156) of participants had used optometry services within the past 2 years. Lack of familiarity with services provided, professional fees, and prices of spectacles were the main barriers to using optometry services. Of those participants who had used the voucher for optometry services previously, 80.4% (284/353) had an eye examination in the past 2 years. Among 389 optometrists who participated in the study, over 80% agreed that the voucher scheme improved awareness of major eye conditions and access to prescription spectacles when necessary.The health care voucher for older people improved access to optometry services. Access could be further improved by increasing price transparency of professional services and prescription spectacles. Responses from optometry service providers supported the view that the voucher scheme improved access to, and utilisation of, preventive care services.

ObjectiveThis study was conducted to evaluate the real-world effectiveness and potential cost-effectiveness of a community-based vision care programme for the ageing population aged 60 years or above.MethodsData from a total of 8899 subjects participating in a community based comprehensive vision care programme from 2015 to 2019 were extracted and analyzed to evaluate the effectiveness of the programme in terms of the prevalence of visual impairment (VI), the change in the prevalence of VI after refractive error correction, and the types of ocular disorders detected. VI was defined by a) visual acuity (VA) worse than 6/18 in any eye (worse eye) and b) VA worse than 6/18 in the better eye. The cost-effectiveness from the funder’s perspective was also estimated in terms of cost per VI avoided from such a programme.ResultsThe study found that referenced to VA of the worse eye, the prevalence of VI was 39.1% (3482/8899, 95% CI: 38.1%-40.1%) based on presenting VA and reduced to 13.8% (1227/8899, 95% CI: 13.1%-14.5%) based on best-corrected VA. Referenced to the VA in the better eye, the prevalence of VI was 17.3% (1539/8899, 95% CI: 16.5%-18.1%) based on presenting VA and decreased to 4.2% (373/8899, 95% CI: 3.8%-4.6%) after best-corrected VA. Uncorrected refractive error was the major cause of presenting VI. From the funder’s perspective, the cost per VI case prevented was HK$1921 based on VA in the worse eye and HK$3715 based on the better eye.ConclusionA community-based programme was effective to detect the VI and reduced a relative 65% to 76% VI after refractive error correction for the community-dwelling ageing population. The ageing population can benefit from regular comprehensive vision care.

ObjectiveTo study how a non-targeted publicly-funded health care voucher system for the elderly impact on access to optometry services from the perspective of service users and service providersDesignCross-sectional studySetting19 elderly community centersParticipants1176 people, aged 65 years or above, and 389 optometristsPrimary and secondary outcome measuresUsage characteristics of optometry services by eligible service users of the voucher schemePerspectives of eligible service users on access barriers to optometry servicesPerspectives of service providers on voucher schemeResultsIn total, 1156 valid questionnaires were collected from a cohort of eligible service users. Results showed that 53.7% of subjects had used optometry services within the past 2 years, while 22% had not used optometry services before. Lack of familiarity with services provided, professional fees and prices of prescription spectacles were the main barriers to using optometry services. Of those subjects who had used the voucher for optometry service before, 80.4% had eye examination in the past 2 years, versus 64.1% among subjects who had not use health care voucher on the optometry service. “Insufficient voucher value” was a commonly quoted reason for not using the health care vouchers for optometry services. Over 80% of optometrists agreed that the voucher scheme improved the awareness of major eye conditions and enabled the elderly to have prescription spectacles when necessary.ConclusionThe health care voucher for the elderly improved access to optometry services. Access could be improved further by promoting awareness optometry services, location of service providers, price transparency of professional services and prescription spectacles. Responses from optometry services providers are supportive of the view that the voucher scheme improved access to and utilization of preventive care services.Article SummaryStrengths and limitations of this study-High representativeness of community dwelling older population in Hong Kong.-The mixed method approach provided a more in-depth investigation of the population.-One limitation is the generalizability of the results with older people who are members in the community centers.

To evaluate the risk factors associated with contamination of lens cases in a group of orthokeratology (ortho-k) lens wearers.Ortho-k patients attending the Contact Lens Clinic of the Hospital were required to complete a checklist about their routine daily care and handling of lens cases. Their cases were then collected for analysis. Contamination was evaluated by determining the optical density (OD) of crystal violet stained biofilm present in the cases. OD values were divided into three groups, lower, middle, and upper tertiles, and associations between risk factors were determined by multivariate analysis.A total of 194 subjects were recruited. Twenty-five subjects used cylindrical lens cases (CC), 98 flat cases with ridges (FCR), and 71 flat cases without ridges (FC). FCRs were the most heavily contaminated and CC showed least contamination (FCR FC, OR 2.16, CI 1.11-4.18, p = 0.023; FCRCC, OR 8.86, CI 2.97-26.44, p0.001; FC CC, OR 2.33, CI 1.35-12.45, p = 0.013). Replacing lens cases monthly significantly reduced the risk of high contamination (OR 0.013, CI 0.06-0.30, p 0.001), compared to those used for three months. Cases that were not rinsed (OR 3.44, CI 1.50-7.86, p = 0.003) or rinsed by other methods (OR 4.07, CI 1.67-9.92, p = 0.002) had significantly more contamination, compared to those rinsed with multipurpose solution. Lens cases, which were not dried (OR 11.36, CI 2.06-62.93, p = 0.005) or air-dried (OR 8.71, CI 1.16-65.56, p = 0.036), showed more contamination compared to those wiped with tissue daily.Case design (cylindrical), monthly replacement, daily rinsing with MPS, and wiping with tissue daily can effectively reduce biofilm formation in contact lens cases.

Purpose To determine the prevalence and risk factors of myopia-related retinal changes in Hong Kong Chinese adolescents with high myopia. Methods A cross-sectional study on Hong Kong Chinese teenage subjects with high myopia was conducted between January 2005 and June 2009. Subjects were recruited via newspaper advertisements, invitation letters to schools, leaflets and posters. Data collected included history related to myopia progression and retinal characteristics. Results In total, 120 subjects (61 boys and 59 girls) were recruited. The mean age was 14.8 ± 1.6 years (range: 12–18 years). The mean SER of the eyes was −8.41 ± 1.60 D. Ninety four of the 120 adolescents were found to have a retinal change of which 0.8% were sight-threatening, 2.5% were posterior pole changes, and 61.7% were peripheral retinal changes. The five most frequent retinal changes found were optic nerve crescents (52.5%), white-without-pressure (51.7%), lattice degeneration (5.8%), microcystoid degeneration (5%) and pigmentary degeneration (4.2%). After adjusting for myopia over −8 D, age, gender, duration of myopia, family retinal history and intraocular pressure (IOP), binary logistic regressions showed that an axial length longer than 26.5 mm was a significant risk factor for peripheral retinal changes, optic nerve crescents and white-without-pressure. Conclusions Peripheral retinal degenerative changes and optic nerve crescent were found in a significant proportion of high myopic teenage subjects. There is increased risk of retinal changes in eyes with an axial length >26.5 mm in 12–18 year-olds.

Purpose Myopia is a complex eye disorder. The X-linked form of complete congenital stationary night blindness (CSNB1A) is usually associated with moderate to high myopia, and is caused by mutations in the NYX gene. We explored if NYX mutations could be associated with high myopia, but not CSNB1A. Methods The coding regions of the NYX gene were sequenced for 204 Chinese males with high myopia (−8.00 dioptres or worse for both eyes). The frequencies of any sequence variations identified were determined in 200 Chinese males without myopia. Electro-oculography, electroretinography and standard cone function tests were performed on a male high myope carrying a mutation. Results A missense mutation (c.529_530GC>AT or p.Ala177Met) was identified in one male subject with high myopia, but not in 200 male emmetropes. Neither was this variant found in any of the 529 male and 567 female subjects of various ethnic backgrounds whose genome sequences are documented in the 1000 Genomes Project database. The mutation was predicted to affect the protein function. From ocular electrophysiological tests, the proband was found to have normal rod function, but mildly abnormal cone function and inner retina function. He did not seem to suffer from CSNB1A. Conclusions One novel missense NYX mutation was identified in an adult male presented with high myopia, but without the major electrophysiological features normally associated with CSNB1A. NYX gene mutations may be considered as one of the rare genetic risk factors for high myopia without key features of CSNB1A.

To investigate the interocular symmetry of optical, biometric, and biomechanical characteristics between the fellow eyes of myopic anisometropes.Thirty-four young, healthy myopic anisometropic adults (≥ 1 D spherical equivalent difference between eyes) without amblyopia or strabismus were recruited. A range of biometric and optical parameters were measured in both eyes of each subject including axial length, ocular aberrations, intraocular pressure, corneal topography, and biomechanics. Ocular sighting dominance was also measured.Mean absolute spherical equivalent anisometropia was 1.70 ± 0.74 D, and there was a strong correlation between the degree of anisometropia and the interocular difference in axial length (r = 0.81, p0.001). The more and less myopic eyes displayed a high degree of interocular symmetry for the majority of biometric, biomechanical, and optical parameters measured. When the level of anisometropia exceeded 1.75 D, the more myopic eye was more likely to be the dominant sighting eye than for lower levels of anisometropia (p = 0.002). Subjects with greater levels of anisometropia (1.75 D) also showed high levels of correlation between the dominant and non-dominant eyes in their biometric, biomechanical, and optical characteristics.Although significantly different in axial length, anisometropic eyes display a high degree of interocular symmetry for a range of anterior eye biometrics and optical parameters. For higher levels of anisometropia, the more myopic eye tends to be the dominant sighting eye.

Purpose: To investigate the retinal thickness profile in myopic and non-myopic eyes. Methods: The retinal thickness profile of 30 myopic eyes [spherical equivalent error (SER) between −6.00 and −13.63 D] and 31 non-myopic eyes (SER between +2.75 and −0.50 D) were measured using the Stratus OCT (Carl Zeiss Meditec, Dublin, CA, USA). Two scan types were used: the Macular Thickness Map and the Customized Line Scan for a central 80° horizontal retinal thickness profile. Results: At foveal center and fovea, myopic eyes had a thicker retina than the non-myopic group (p = 0.002 and 0.044, respectively). At other zones of the macula, the retina was significantly thinner in myopic eyes compared to non-myopic eyes (p

Background: The relationship between monochromatic aberrations of the human eye and myopia has been investigated extensively over the past decade or so but the results are inconclusive. Wide age range, narrow refractive error range and large individual variations are common confounding factors in previous studies. To address these shortcomings, we conducted a two-part study. The first part set out to determine whether the monochromatic aberrations in myopic eyes are different from those in the non-myopic eyes in adults. Subjects were drawn from a narrow age band to minimise the confounding effect of age. The second part of this study compared the monochromatic aberrations of the more myopic and less myopic eyes of anisometropes. Methods: Monochromatic aberrations were measured for 5 mm pupils using the Complete Ophthalmic Analysis System (COAS) Wavefront Analyzer in 116 subjects with refractive spherical equivalent between -10.38 D and +1.38 D and in 26 anisometropes. Measurements were done in a dark room with natural pupils. The refractive errors, corneal curvatures and axial lengths of the eyes were measured under natural accommodation. Results: Highly myopic eyes had significantly smaller root mean square (RMS) values of fourth order (p = 0.015) and spherical aberrations (p = 0.009) than non-myopic eyes. The correlation coefficient was 0.2354 (p = 0.011) between fourth-order aberrations and refractive spherical equivalents and 0.2817 (p = 0.002) between spherical aberration and refractive spherical equivalents. Less myopic eyes of the anisometropes showed significantly larger total higher-order, third-order and spherical aberrations than the more myopic eyes (p < 0.05, p < 0.05 and p < 0.01, respectively). Conclusions: Our study shows that spherical aberration is associated with refractive error. More myopic eyes tended to have smaller amounts of spherical aberration, however, the ‘cause or effect’ question remains. Longitudinal studies are needed to further investigate the relationship between monochromatic aberrations and refractive development.

Background: Optomap uses the ultra-wide field scanning laser ophthalmoscopy to provide retinal examination. It permits fundus examination without the use of a mydriatic, which is more comfortable for the patients. This paper determines the sensitivity and specificity of the Optomap for detecting retinal signs under non-mydriatic conditions.----- Methods: Fifty-four eyes identified with retinal/choroidal signs and eight normal eyes were recruited from 31 Hong Kong Chinese subjects. Photo-documentation of fundal changes was obtained with the Optomap under non-mydriatic conditions before a dilated fundus examination by a clinician using standard procedures. The eyelid was retracted using a cotton bud when necessary. Dilated fundus examinations were performed by another clinician using binocular indirect ophthalmoscopy and slitlamp biomicroscopy with a fundus lens. The Optomap images were evaluated by four other investigators under masked condition. The International Classification of Disease, Ninth Revision (ICD-9-CM) was adopted for recording retinal features. Screening results were compared with those obtained using the dilated fundus examination as the gold standard.----- Results: The cotton bud method for eyelid retraction showed an improvement in the area of retina that could be visualised. The sensitivity and specificity of the Optomap averaged 76.4 and 71.9 per cent, respectively. Some fundal signs were missed by all observers in the Optomap but not with the biomicroscope. These included white-without-pressure, lattice degeneration, paramacular drusen and pigmentary changes at central fundus.----- Conclusion: Optomap serves as a reliable screening tool for fundus examination especially because it covers a much wider area of the peripheral retina than other digital instruments for fundus photography.

The prevalence of myopia is high in many parts of the world, particularly among the Orientals such as Chinese and Japanese. Like other complex diseases such as diabetes and hypertension, myopia is likely to be caused by both genetic and environmental factors, and possibly their interactions. Owing to multiple genes with small effects, genetic heterogeneity and phenotypic complexity, the study of the genetics of myopia poses a complex challenge. This paper reviews the current approaches to the genetic analysis of complex diseases and how these can be applied to the identification of genes that predispose humans to myopia. These approaches include parametric linkage analysis, non-parametric linkage analysis like allele-sharing methods and genetic association studies. Basic concepts, advantages and disadvantages of these approaches are discussed and explained using examples from the literature on myopia. Microsatellites and single nucleotide polymorphisms are common genetic markers in the human genome and are indispensable tools for gene mapping. High throughput genotyping of millions of such markers has become feasible and efficient with recent technological advances. In turn, this makes the identification of myopia susceptibility genes a reality.

The aims were to determine the level of compliance of contact lens wearers, to identify which procedures have highest levels of non-compliance and to study the effectiveness of a compliance enhancement strategy on the level of compliance.The level of compliance for each subject was evaluated with a self-administered questionnaire together with microbiological examination of their contact lenses, lens cases and lens care solutions. The effect of an intervention to improve the level of compliance was determined by a controlled trial. A regular self-review exercise on proper lens handling was given to the test group once every three months for 12 months. The levels of compliance and contamination of contact lenses and lens care accessories between test and control groups were compared at the end of the 12-month period to evaluate the effect of the intervention.Sixty-five subjects who were experienced contact lens wearers were recruited and 60 completed the study. All showed some degree of non-compliance in the care of their contact lenses and lens accessories. Most (about 60 per cent) were non-compliant with at least six of a total of 15 lens care procedures. The most common non-compliant behaviour among contact lens wearers was associated with the care of the lens case. By the end of the study period, our compliance enhancement strategy did not appear to have had a significant effect on the behaviour of our subjects, except for improvement in the care of lens cases. Compliance for other procedures improved in both test and control groups.All subjects showed some degree of non-compliance and the spectrum of non-compliance was wide. The poorest levels of compliance were associated with care of the lens case, which was also the most frequently contaminated item. Our compliance enhancement strategy showed a significant difference in improvement in compliance between the intervention and control groups only in the care of lens cases.

Purpose: This study aimed to examine the rates of microbial contamination, and identify contaminants associated with contact lenses and lens care accessories used by a group of young contact lens wearers. Methods: Collected contact lenses, lens cases, and lens care solutions were studied by bacterial culture. Contamination rates of these samples were recorded and compared with those reported in previous studies. Results: Of the samples tested, 9% of lens extracts, 34% of case extracts and 11% of solution samples were contaminated with ocular pathogenic microorganisms. Serratia spp., Staphylococcus aureus and coagulase-negative staphylococci were the most common microorganisms isolated. Lens cases were the most frequently contaminated item. Lens cases also yielded the widest range of bacterial isolates. Contact lenses used by occasional wearers were associated with a higher contamination rate. Using either saline or multipurpose solution to rinse lenses before use appeared to be effective in reducing incidence of contamination. Conclusion: Our findings demonstrate that contact lenses and lens care accessories are not well maintained by contact lens wearers. Regular reviews and reinforcement of lens care procedures for the usage and care of contact lenses and lens care accessories is therefore important and essential.

To study the effect of aging retina on the multifocal electroretinogram (mfERG). A total of 18 young subjects (age 18–24 years) and 36 elderly subjects (aged 60–85 years) with intraocular lenses (IOLs) were recruited for this study. No subjects had significant eye diseases or media opacities. mfERG was measured in standard conditions using the VERIS system (version 4.1). There were three groups of 18 subjects: (1) 18–25 years, (2) 60-70 years, and (3) 75–85 years. mfERG responses were grouped into central, paracentral, and peripheral regions for analysis. The N1 amplitude, P1 amplitude, N1 latency, and P1 latency of the first-order responses were analysed. Age had no effect on P1 latency, N1 amplitude, and P1 amplitude; however, N1 latencies from central to peripheral regions were significantly longer for group 3 than for group 1. This study suggests that measured age-related decreases in mfERG responses are due to optical factors (decrease in retinal light levels, scatter) before the age of 70 years, but neural factors significantly affect mfERG topography after the age of 70 years.

Purpose: The purpose of this study was to determine the macular pigment optical density (MPOD) in a group of Chinese subjects using a simple customized light emitting diode-based device. Methods: Heterochromatic flicker photometry was used in this study. With a 1° diameter circular test stimulus, MPOD was estimated by comparing the relative sensitivities to a blue light, against a green reference, between foveal and parafoveal 4° temporal locations. Fixed alternating frequencies were used. Repeatability was determined on a small group of subjects. A further group of 67 young healthy subjects provided data for MPOD norms. Results: All results were corrected to the common MPOD reference wavelength of 460 nm. The group-averaged MPOD was 0.48 (S.D. 0.23). We found no gender difference in MPOD. The coefficient of variability was 7.2–8.0% and the coefficient of repeatability was 0.12. Conclusions: The MPOD of Chinese subjects did not differ greatly from the reported MPOD in white subjects.

The purpose of this study was to examine the development of the orbit in Hong Kong Chinese subjects. Orbit volume was determined from magnetic resonance images of 81 subjects aged from 1 to 42 years old. Results show that orbit volume ranged from 11.56 to 25.50 cm3. In the first year of life, the mean orbit volume was 12.36 cm3. The orbit showed rapid growth in the first 3 years of life. From about 1–3 years old, the mean volume was 15.31 cm3. The orbit grew steadily to the age of 10 years. From age 11 to 15 years old, the mean volume was 20.24 cm3. Orbit growth levelled off at about 16 years of age with the mean volume at 21.00 cm3.

The purpose of this study is to determine if there is an association between eye size and the volume of the orbit in adult subjects. Thirty-three subjects with varying degrees of ametropia (+1.00 to -12.75 D) underwent magnetic resonance scan of the orbit. Results show that the larger myopic eye was not associated with a larger orbit.

To compare and contrast the prevalence of myopia and other refractive errors in Xiamen city, Xiamen countryside (Southern China), and Singapore.One hundred thirty-two schoolchildren aged 6 to 7 years from Xiamen city, 104 from Xiamen countryside, and 146 from Singapore city were recruited to join the study. Cycloplegic autorefraction, keratometry, and biometry measurements were performed on all children.The prevalence of myopia was 12.3% in Singapore city, 9.1% in Xiamen city, and 3.9% in Xiamen countryside. The prevalence of astigmatism was higher in Singapore compared with Xiamen. The rates of hyperopia and anisometropia were similar in all three locations.The myopia rate in Singapore city was higher than in Xiamen city; the lowest rates were found in Xiamen countryside. As the Chinese population from all three sites is of similar genetic stock (predominantly from Southern China), it is postulated that the differences in myopia rates in these three localities may be related to environmental factors.

Professor Norhani Mohidin was born in a rubber plantation in Kampong Batang Benar in the State of Negeri Sembilan in Malaysia. The plantation was her grandfather's and there was enough land to gift...

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.

Tear volume, measured using a cotton thread test (CTT), was assessed in 91 Hong Kong (HK)-Chinese (46 females,45 males aged from 8 to 70 years) and 35 Singapore (S)-Chinese (21 females, 14 males aged from 7 to 65 years). The mean (±SD) CTT value of HK-Chinese and S-Chinese was 17.5 (±8.1) mm/min and 19.6 (±12.0) mm/min respectively. No significant difference in the CTT values between the two groups of Chinese was found, so their data were pooled. The mean (±SD) CTT value of the pooled data was 18.1 (±9.3) mm/min; 18.4 (±9.0) mm/min for female subjects and 17.8 (±9.7) mm/min for male subjects. Regression statistics of the pooled CTT values on age showed a correlation of −0.59 (p

We surveyed and assessed 2,323 schoolchildren aged seven to 17 years from four schools in China, two in the city of Tianjin and the other two in a neighbouring rural village, Ban Chau, to investigate the prevalence of refractive error and its relationship with environmental factors. Every child from each of the participating classes was recruited in this study to avoid self-selection. A questionnaire was issued which queried some aspects of the child's visual habits and home. Refraction was canied out using the Canon R-22 autorefractor. The degree and frequency of myopia in these children increased almost linearly from age seven to 17 years. There was little difference between the urban and rural groups. Of the factors explored, the number of hours spent on near work showed the best correlation with the degree of myopia, albeit only weakly.

Background: The aim was to examine the progression and regression of diabetic retinopathy within a four-year period in a Chinese population with type 2 diabetes mellitus in a community optometry clinic in Hong Kong. Methods: During the period May 2005 to November 2009, 5,160 patients with type 2 diabetes mellitus who had attended at least two diabetic retinopathy screening sessions at a community optometry clinic were included as subjects in this study. All had retinal photographs taken of both eyes, which were of sufficiently good quality for grading. For the purpose of this study, diabetic retinopathy grading was based on the results of the worst eye. The main outcomes were the within four-year incidence of diabetic retinopathy and the incidence of progression and regression of diabetic retinopathy. Results: Of the 5,160 subjects in this study, 3,647 had no diabetic retinopathy, while 1,513 had diabetic retinopathy at the baseline visit. Of those 3,647 subjects with no diabetic retinopathy, the within four-year cumulative incidence of any diabetic retinopathy, mild or moderate non-proliferative diabetic retinopathy and sight-threatening diabetic retinopathy was 15.16 per cent, 14.45 per cent, 0.69 per cent and 0.03 per cent, respectively. Of those 1,513 subjects with diabetic retinopathy at baseline, the within four-year progression incidence of diabetic retinopathy was 6.61 per cent and the regression incidence of diabetic retinopathy was 45.54 per cent. Conclusion: The high regression incidence of diabetic retinopathy suggests that it might not be necessary for all patients with diabetes to be screened annually. Other methods to determine the screening frequency for an individual patient should be explored.

Previous studies suggest that myopia in parents may influence the genesis of myopia in their offspring. In this study, we surveyed 2888 children of Chinese descent in China and Hong Kong to determine the relationship between the refractive state of parents and their children. The age range of the children was 7-17 years. Refraction was measured using a Canon R-22 objective infrared autorefractor and a survey on family history of ametropia was conducted using a questionnaire. We found that children with myopic parents are more likely to be myopic.

We measured stereoacuity in 41 subjects with normal Snellen acuity in each eye, and normal ocular health. Patients were measured in each of the age ranges 21-28, 41-49, 51-59 and 60-70 years. Stereoacuity was reduced from about 16 sec arc for the three younger groups to about 27 sec arc for the older subjects. Since stereopsis has a cortical neural substrate, these data suggest that there may be cortical changes affecting the interaction of information from the two eyes with advancing age, but whether these changes result from loss of contrast sensitivity, instability of ocular alignment or binocular stress, all of which have been reported in elderly subjects, is not known.

We investigated the influence of age, gender and refraction on ocular rigidity in Chinese patients. Two groups were studied: 76 healthy young subjects aged between 19–30 years; 70 healthy elderly subjects aged between 57–90 years. The Schiotz tonometer and the Friedenwald paired weight pressure rigidity table were used to determine the ocular rigidity. Age did not significantly affect ocular rigidity. The degree of myopia was poorly correlated with ocular rigidity (r= 0.109). The mean value for all healthy subjects was 0.0156 (sd 0.0065). This is lower than previously reported values which range from 0.0184 to 0.0263.

School children in Hong Kong who fail an Education Department vision screening at the age of five or six are referred to eyecare agencies for a full eye examination. Three hundred and ninety-one consecutive cases seen at the Hong Kong Polytechnic were analysed to obtain a breakdown of the type of refractive errors causing reduced vision among children starting primary school. There was a tendency towards myopia and with-the-rule astigmatism. Exotropia was more commonly encountered than was esotropia. Strabismus and amblyopia were predominantly associated with anisometropia and astigmatism. Key words: vision screening, retractive error, primary school children, Chinese, strabismus. Hong Kong

This report provides some statistical information based on clinical data gathered on low vision patients who attended the low vision clinic of the Hong Kong Society for the Blind in the first three years of its operation. In this period, low vision devices were prescribed for 393 patients (46.5 per cent of the sample). The most commonly prescribed aids were simple magnifiers and distance telescopes. Cataract was the major cause of low vision.

Purpose: To investigate the influence of eyelid position on wavefront aberrations. Methods: In study 1, the right eyes of 43 non-cyclopleged subjects were evaluated using the Complete Ophthalmic Analysis System (COAS) aberrometer. In study 2, the right eyes of the 23 cyclopleged subjects were evaluated using the Optical Pathway Difference Scan aberrometer. Measurements were made with wide-open and deliberately narrowed palpebral apertures in these subjects. In study 3, the influence of eyelashes on the COAS output was investigated in 20 subjects by placing artificial eyelashes in front of the eye, in close proximity to the natural eyelashes. Results: For study 1, the total root mean square (RMS) of the third- and fourth-order aberrations with the wide-open lids was significantly different from the narrowed lid position after the correction for multiple comparisons. There was a difference in the Zernike coefficient of the defocus (C4), 90/180 astigmatism (C5), vertical coma (C7) and spherical aberration terms (C12) between the narrowed and wide-open positions. For study 2, changes were observed with the narrowed lid position in the overall RMS of the third and fourth orders, and total coma aberrations, as well as the specific Zernike coefficients of the C5 and C7 terms. However, none of these changes were significant after the multiple comparison correction. The corneal topography also showed remarkable changes in the superior corneal zone. Placing artificial eyelashes in front of the eye significantly affected some Zernike terms and the RMS of the second and fourth orders, and total coma aberrations, for particular pupil sizes. Conclusions: Deliberate narrowing of the palpebral aperture can influence the wavefront aberrations significantly. The corneal curvature distortion in response to eyelid pressure may account for some of the effect on aberration change. Eyelashes interfering with the light path within the pupil zone distort the output from the COAS, causing significant errors.

The radius of curvature of the posterior surface of the cornea was measured in the vertical meridian for 120 children aged 6 to 17 years, using a Purkinje image method. The mean radius of curvature (+/-SD) was 6.42 +/- 0.31 mm, with a range from 5.62 to 7.22 mm. The ratio of anterior to posterior corneal radius was 1.210 +/- 0.045 or 0.827 +/- 0.029 when expressed as a reciprocal. There was a significant correlation between the anterior and posterior corneal radius (y = 0.798x + 0.228, r2 = 0.45). The study provides data that may be applied to a four-surface schematic eye.

Aim: To develop an isolated arterially perfused bovine eye as an in vitro model for studying retinal electrophysiology using multifocal electroretinography (mfERG). Methods: Fresh bovine eyes were cannulated through the ophthalmic artery and perfused with oxygenated Krebs’ solution at 37°C within 15 min postmortem. Multifocal ERG was recorded using the veris 1.0 (Visual Evoked Response Imaging System). Results: The mfERG waveform of in vitro bovine eyes had a typical trough (negative wave, N1) and peak (positive wave, P1) similar to those of human mfERG. The implicit times (peak latencies) for N1 and P1 were 20 and 42 ms respectively, and the average response amplitude (N1P1) was 55 nV. The implicit times of N1 and P1 were maintained for more than 4 h. The mfERG responses were affected proportionately by the stimulus intensity. Without a neutral density filter, the mean response amplitude was about 55 nV, which was diminished to 26, 18 and 10 nV under neutral density filters of 0.4, 1.0 and 1.4, respectively. Partial occlusion of the pupil completely abolished mfERG responses from the corresponding part of the retina. Conclusions: Isolated arterially perfused bovine eye may be used as an experimental model to study retinal electrophysiology using mfERG. The in vitro eye may offer a convenient and easily obtainable alternative to live animals, particularly for drug screening and invasive studies.

Purpose: The aim of this survey was to evaluate the use of contact lenses, current prescribing habits of practitioners and the development of the contact lens market in Hong Kong. Methods: Questionnaires were sent to all registered contact lens practitioners in Hong Kong. This questionnaire sought information about their choices on prescribing contact lenses and lens care products and their opinions on continuing education and future trends of contact lens development. Results: A total of 286 responses (22 per cent) were returned. On average, the respondents reported that 36 per cent of their patients were contact lens wearers and most were myopes. The ratio of new fittings to refittings was 1:3. Of the contact lens wearers, 66 per cent were fitted with planned replacement lenses, mostly daily disposable lenses. Multipurpose solution was the most popular lens care regimen prescribed. Only 48 per cent of astigmatic patients were fitted with toric lenses and the use of overnight orthokeratology and silicone hydrogel lenses was limited. Single vision contact lenses with over-spectacles and monovision contact lenses were the most popular management for presbyopes. Dryness was the major problem reported by contact lens wearers. Practitioners look forward to further development of custom-made toric, multifocal and silicone hydrogel lenses. The major source of new contact lens information was communication with contact lens suppliers. Conclusion: Compared to previous reports, there was no significant change in the prescribing habits of practitioners. The major complaint of contact lens wearers is still ocular dryness. The contact lens market is driven by younger contact lens wearers, and planned replacement soft contact lenses together with multipurpose solutions dominate. The use of bifocal/multifocal lenses remained low and practitioners want low cost bifocal/multifocal contact lenses with better visual performance and toric lenses with a wider range in parameters. The use of overnight wear lenses such as silicone hydrogel and ortho-k lenses is limited and 30 days continuous wear silicone hydrogel lenses are prescribed mainly for daily wear.

Background: Tear stability in normal Malays with consideration of gender and age has not been reported. In this study, we measured tear stability in normal Malays using the non-invasive tear break-up time (NIBUT). Methods: Forty-eight Malay subjects aged seven to 60 years were recruited from among the staff, their children and students of the faculty. NIBUT was measured by noting the time taken for distortions to appear in a reflected image of a grid pattern formed on the corneal surface. Results: The mean NIBUT of the sample was 15.8 ± 9.4 (SD) seconds. The median was 14.6 seconds with range of 4.2 seconds to 48.6 seconds. The majority (73 per cent) of subjects had NIBUT values between six and 20 seconds. There was no significant difference in NIBUT values between males and females but there was a decrease of NIBUT with age. Conclusion: The NIBUT values found in this study are comparable to those reported for Asian populations but much less than those of Western populations. Our findings point to the need for local clinical studies in contact lens and contact lens-related research as tear physiology of the local population may not be the same as in Western populations.

The influence of age on the amplitude density (nV/sq deg) of the multifocal electroretinogram (ERG) was studied in 90 healthy subjects aged 18-52 years. Subjects were divided into three separate age groups; (i) 18-22 years (ii) 33-37 years and (iii) 48-52 years. Amplitude density of first order kernel of the multifocal ERG was measured for the three different age groups. When the whole response of the retina is considered, analysis of variance showed no significant differences in amplitude density between the three age groups. (ANOVA, df. 2, 87 F = 2.29, p = 0.11. However if the responses were segregated into a central area and concentric rings around the central area, analysis of variance showed that there were significant differences in responses between rings at different eccentricities and between different age groups (Anova F = 76.19, df. 17, 522, p = 0.00001). Post hoc analysis showed that the responses from the centre and the second ring around the centre of fixation for 48-52 year olds were significantly lower than those responses from the 33-37 year old and the 18-22 year old age groups. The decline in the multifocal ERG in the central retina of the 48-52 year olds could be associated with the decline of the number of photoreceptors as the eye ages. Student t test revealed no significant differences in amplitude density between males and females.

Tonic accommodation is known to be different in different refractive gr Myopes show a lower degree of tonic accommodation than do hyperopes and eminetrof is not known is whether the lower tonic accommodation in emrnetrope,s predisposes the i’D myopia. In this study, we initially measured the refraction and tonic accommodation of 210 children, aged 6 to 16 years. We identified the emmetropic children and refracted them again 2 years later. We found that myopic children had lower tonic accommodation than emmetropic and hyperopic children. For the emmetropic children, there was no clear relationship between tonic accommodation and subsequent refractive change 2 years later. We conclude that the level of tonic accommodation does not predict refractive change in the short term.

Background: Cyclopentolate continues to be the cycloplegic of choice for refracting young children, although many studies of ocular biometry promote the use of tropicamide. Methods: To clarify the role of drug type in biometric measurements, cycloplegia was induced in two disparate age groups using cyclopentolate and tropicamide on two separate occasions. Refraction, phakometry and A-scan ultrasonography measurements were made on two groups of Tibetan children resident in Nepal. Results: Cyclopentolate produced significantly more cycloplegia in the younger group, which was supported by phakometry measurements. However, in clinical terms, the difference between the measurements was not significant. Conclusion: We conclude that although cyclopentolate is more effective than tropicamide in relaxing accommodation in young children, the use of a local anaesthetic prior to instillation of tropicamide produces refractive data virtually equivalent to that of cyclopentolate, regardless of the age group measured. However, biometric measurements may be susceptible to greater error when near fixation targets are used during phakometry procedures.

The speed of macular capillary blood flow can be estimated by using the blue field entoptic phenomenon. The technique uses a matching task in which the subject matches what is seen entoptically with a computer simulation of the phenomenon. In this study, we tested the repeatability of the leukocyte speed results obtained using this technique. Fourteen young subjects were tested on five different occasions. Group mean leukocyte speed did not vary significantly from one recording session to the next. However, readings for individuals varied substantially from one recording session to the next. This variability limits the usefulness of this technique for screening or monitoring macular blood flow in individuals.

We investigated the effect of age and gender on the tear break-up time (TBUT) of 2 groups of normal, asymptomatic subjects [92 Hong Kong-Chinese (HK-Chinese) and 76 Singapore-Chinese (S-Chinese)] using the conventional fluorescein-instillation technique. The mean TBUT (+/- SD) is 6.5 (+/- 4.0) s for the S-Chinese and 7.8 (+/- 2.4) s for the HK-Chinese. The mode was 7.0 s for HK-Chinese and 5.0 s for S-Chinese. About 80% of the subjects of each group have TBUT less than 10 s. The TBUT of both groups of Chinese decreases with age. It was found that TBUT was significantly different between the two sexes in the S-Chinese but no equivalent effect was observed in the HK-Chinese.

Since its introduction by Schirmer in 1903, the Schirmer test has been widely used for the assessment of the adequacy of tear production. Although the faults of the Schirmer test have been well documented, it is nevertheless still being used to assess tear production, especially in the diagnosis of keratoconjunctivitis sicca (KCS) and for screening potential contact lens wearers. We summarize the findings and conclusions of some of the previous studies.

Editor: We wish to supplement the excellent profile on Professor Leo Carney (Clin Exp Optom 2010; 93: 2: 105–108).Apart from his outstanding research and academic achievements in Australia and the ...

Binocular summation, defined as an increase in the binocular response compared with the monocular, occurs when the sensitivities of the two eyes are equal. We investigated the psychophysical and electrophysiological binocular response to a difference in monocular retinal illuminance. Different levels of unequal monocular sensitivities were induced by means of neutral density filters placed in front of one eye. Both studies produced similar results. In the absence of filters, maximum binocular summation was produced. With increasing difference in monocular illuminance, the binocular response decreased steadily until it reached a level below the monocular. The clinical implications of binocular inhibition, a perceptual phenomenon similar to Fechner's Paradox, are discussed.

The use of the Arden gratings (AO contrast sensitivity system) in optometric practice is evaluated. A total of 320 patients presenting for eye examination were screened with the gratings. Sixty-four eyes (10%) gave abnormal grating scores although results from conventional examination techniques revealed no abnormality. Of the 110 abnormal eyes detected by routine examination techniques, 8 presented with normal grating scores, 6 with "borderline suspect" scores and 96 with abnormal scores. Used in isolation, the failure rate of the Arden gratings to detect ocular abnormality in the patient population was 1.3% and the "false positive" referral rate was 10%.

The utility of the Melbourne Edge Test (MET) in optometric practice was evaluated by screening 293 consecutive patients who presented for routine eye examination. The MET identified ocular abnormalities in 37 eyes. Of these, 36 also manifested a reduction of visual acuity. The incidence of "false positives" was 1.0%. The MET test failed to detect ocular abnormalities revealed by conventional examination techniques in 29 eyes (4.9%), of which 28 exhibited Snellen acuity losses.

Most previous studies have found no visual advantage for the use of yellow filters. This study reports the effect of wearing a long-pass yellow filter on monocular spatial contrast sensitivity under photopic and mesopic conditions. Contrast sensitivity was improved with the yellow filter under photopic conditions but not significantly at most spatial frequencies under mesopic conditions.

The size of the foveal avascular zone (FAZ) reflects the condition of the microcapillary circulation in the foveal area. A number of studies have shown a significant increase in FAZ size in conditions of vascular pathology including diabetes. A non-invasive method of estimating FAZ size may be a valuable addition to a psychophysical test battery. We used a blue-light field to reveal the activity of the retinal leucocytes to two groups of normal subjects with average ages 24 and 61 years. Two methods were used to estimate the FAZ size, making use of the fact that subjects could see their own FAZ as the area free of leucocyte activity. The first method required subjects to indicate when leucocyte activity stopped as the field size was decreased and when it reappeared as field size was increased. The second required subjects to match the size of the leucocyte-free area with a white circle superimposed on the field. A search algorithm was used to change circle size according to subjects' responses. Results show a significant difference in FAZ size between the two age groups with both methods of measurement, and estimates were comparable to those reported using angiographic methods.

A retrospective review of the BD8 forms submitted for the period 1980–85 in the Bradford Metropolitan District was conducted to ascertain the incidence and causes of blindness and partial sight. A total of 1485 cases were registered in this period of which 755 (50%) were included in the Blind register and 730 (49.2%) in the Partially Sighted register. Age-related macular degeneration was the most important cause of visual handicap, accounting for 43.9% of all registrations, followed by glaucoma (16.2%), diabetic retinopathy (6.3%), myopic degeneration (6.1%), optic atrophy (4.4%), cerebrovascular disease (3.8%), cataracts (3.6%), retinal vascular occlusive disease (3.2%), corneal opacities (3.0%), congenital anomalies (2.7%), retinitis pigmentosa/tapeto-retinal degeneration (1.9%), retinal detachment (1.8%) and others (3.1 %). The ratio of female to male registrations was 1.8:1. Eighty-four per cent of this sample population was above the age of 60 years at the time of registration.

One hundred and ninety-nine elderly inhabitants of a fishing village in Hong Kong were screened for vision and ocular abnormalities. About three-quarters of the sample had a binocular visual acuity of 6/18 or worse and for a quarter of these, the binocular acuity was 6/60 or worse. Less than half of those screened could see local Chinese newsprint well enough to read. Cataract and pterygium were the commonest ocular anomalies found.