Orbital development in Hong Kong Chinese 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.     

Inter- and intra-individual variability of non-invasive tear break-up time in Hong Kong Chinese

Non-invasive tear break-up time (NITBUT) has been proposed as a measure of tear film integrity which is superior to the more commonly used tear break-up time (TBUT), since it does not alter the volume or the physicochemical properties of the tear layer by the addition of fluorescein. We measured NITBUT by measuring the time taken for distortions or discontinuities to appear in the reflected image of a grid pattern which covered about 80 per cent of the corneal surface. NITBUT measures were made 100 times on seven Hong Kong Chinese subjects with up to 20 consecutive measures being made on a single day. We also measured NITBUT on one occasion on an unselected population of 52 Hong Kong Chinese subjects. NITBUT shows a skewed distribution in all subjects, with many shorter values and some extremely long values. There are statistically significant variations in NITBUT from day to day, and from subject to subject. The group of 52 subjects also had a skewed NITBUT distribution with many short values and some very long values. The arithmetic mean does not adequately represent NITBUT data, either for individual subjects or for this group of subjects. As many as five to eight measures may be necessary to gain a stable estimate of the NITBUT and stability of the measure is improved if extreme values are omitted. We recommend the use of nonparametric statistics to compare NITBUT values from day to day in or between subjects.     

Reliability of the tear break-up time technique of assessing tear stability and the locations of the tear break-up in Hong Kong Chinese.

The measurement of tear break-up time (TBUT) in assessing stability of the tear film is somewhat controversial, even though the technique is widely used. We examined reliability of the technique within and among examiners and conclude that measurements of TBUT can be made reliably; full-beam observation of the cornea is preferable to scanning the cornea with a narrow slit in making the measurements. There may be differences in TBUT measurements made in the same subjects among examiners, but these differences are smaller with more experienced practitioners. In the Hong Kong Chinese (HK-Chinese), tear break-up appears to be more likely to first occur in the inferior periphery of the cornea. In this population mean TBUT is about 7.20 s; assuming a Gaussian distribution of TBUT values, 2.1 s should be adopted as the lower limit for normal TBUT in HK-Chinese.     

Mechanical manipulation of the lids and tear break-up time measurements in Hong Kong Chinese

We measured tear break-up time (TBUT) after lid-rubbing in a single masked experiment, and found that TBUT was unaltered. A further single masked experiment in which non-invasive tear break-up Lime (NITBUT) was measured after the lids were raised as if to apply fluorescent also showed no effect of this interference with the lids. An experiment in which fluorescent was applied either with the lid raised or not raised during fluorescein application, again with the experimenter masked with respect to treatment, also produced no significant difference in TBUT. When we measured TBUT with the lid raised so that it was not in contact with the cornea, there was no difference in TBUT for the group between the "lifted" and 'non-lifted' eye; some subjects showed substantially shorter TBUT values, while others showed substantially longer TBUT values. These findings are surprising in view of the concerns expressed in the literature regarding the sensitivity of the tear film to mechanical interference, and suggest that the tear film is more resistant to disruption than has previously been thought.     

Eye position and head size in the Chinese population: a comparison of the Chinese from Hong Kong with the Chinese from Guangdong Province.

Measurements obtained in this study include facial and head dimensions. From our findings, it would appear that the Chinese population in Hong Kong have not become different in the two or three generations that separate them from those living in Guangdong province of China.     

Nearwork-induced transient myopia in preadolescent Hong Kong Chinese

PURPOSE: To compare the magnitude and time course of nearwork-induced transient myopia (NITM) in preadolescent Hong Kong Chinese myopes and emmetropes. METHOD: Forty-five Hong Kong Chinese children, 35 myopes and 10 emmetropes aged 6 to 12 years (median, 7.5), monocularly viewed a letter target through a Badal lens for 5 minutes at either 5.00- or 2.50-D accommodative demand, followed by 3 minutes of viewing the equivalent target at optical infinity. Accommodative responses were measured continuously with a modified, infrared, objective open-field autorefractor. Accommodative responses were also measured for a countercondition: viewing of a letter target for 5 minutes at optical infinity, followed by 3 minutes of viewing the target at a 5.00-D accommodative demand. The results were compared with tonic accommodation and both subject and family history of refractive error. RESULTS: Retinal-blur-driven NITM was significantly greater in Hong Kong Chinese children with myopic vision than in the emmetropes after both near tasks, but showed no significant dose effect. The NITM was still evident 3 minutes after viewing the 5.00-D near task for 5 minutes. The magnitude of NITM correlated with the accommodative drift after viewing a distant target for more than 4 minutes, but was unrelated to the subjects' or family history of refractive error. CONCLUSIONS: In a preadolescent ethnic population with known predisposition to myopia, there is a significant posttask blur-driven accommodative NITM, which is sustained for longer than has previously been found in white adults.     

Normal values of eye position in the Chinese population of Hong Kong.

Exophthalmos, interpupillary distance (IPD), interobital distance (IOD), and inner intercanthal distance (ICD) were measured in an adult Chinese population from Hong Kong (HKC). Mean values and normal range for 95% of the population were determined and the relation with head size and body height examined. Values of exophthalmos and IPD in our Chinese population were similar to those given for Caucasian groups. IOD and ICD were larger in the Chinese than in adult Caucasians. Our findings show generally larger values in the HKC than has been found for other populations in mainland China.     

Incidence of diabetic retinopathy in a Hong Kong Chinese population

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.     

Autosomal recessive inheritance of myopia in Hong Kong Chinese infants

Hong Kong Chinese infants were refracted by retinoscopy at regular intervals between the age of approximately 10 and 40 weeks. Cyclopentolate 1% was used to obtain cycloplegia. The spherical equivalent of the refractive error was calculated for each child and analysis of variance carried out according to the refractive status of the parents. From approximately 20 weeks of age a significant difference was found between the mean spherical equivalent of the refractive error of infants of parents both of whom were myopic and that of infants of parents neither of whom was myopic. At 40 weeks of age a good fit with an autosomal recessive probability model was obtained.     

Incidence and risk factors for microbial keratitis in Hong Kong: comparison with Europe and North America

PURPOSE: To establish the incidence, etiology and risk factors for microbial keratitis (MK) in Hong Kong. METHODS: Two hundred and twenty-three new cases of presumed MK were recruited over a period of 17 months and comprehensive microbiologic studies performed. A nested case-control study was pursued for patients wearing contact lenses (CLW) to determine risk factors for MK with regards to types of CLW and hygiene practice. RESULTS: Of the 223 patients recruited, 59 (26%) wore contact lenses. Corneal scrapes yielded positive cultures from 77 patients (35% overall, 56 non-CLW, 21 CLW). Two hundred and six CLW volunteers were recruited to participate in the case-control study, of whom 135 were matched with 45 CLW patients. The annual incidence of MK was 0.63 per 10,000 population and 3.4 per 10,000 CLW with rates for daily, extended and rigid lens wear of 3.09, 9.30 and 0.44 per 10,000 CLW respectively. Pseudomonas aeruginosa was the dominant bacterial pathogen. Six cases of Acanthamoeba keratitis occurred, five in CLW (incidence 0.33 per 10,000 CLW) and one following corneal abrasion. Non-CLW developed MK at a peak age of 73, which is 10 years younger than expected for Scotland and USA. CONCLUSIONS: Previous ocular surface disease and trauma were the main risk factors for MK in Hong Kong. CLW appears at least as safe as that found in Scotland and the USA. Acanthamoeba keratitis was detected but with an incidence rate five times lower than Scotland. Factors predisposing hydrogel CLWs to MK, that were statistically significant, included overnight wear, poor hygiene and smoking.     

Progression of myopia in Hong Kong Chinese schoolchildren is slowed by wearing progressive lenses.

PURPOSE: In Chinese societies, primary and secondary schoolchildren perform large amounts of reading and homework and thus spend long periods performing near work during their growth years. Progressive lenses, which can permit a focused retinal image at distance, intermediate, and near, without accommodation, may slow the development of myopia. This paper reports results of a 2-year longitudinal study to examine the effects of progressive lenses on myopia progression in myopic Chinese children; these children were aged between 9 and 12 years at the beginning of the study. METHODS: Prestudy vision screening tests and five examinations, which included noncycloplegic refraction, were conducted at half-yearly intervals. Of those who completed the study, 32 children wore single vision (SV) lenses (the SV group) and 36 wore progressive lenses; of the latter, 22 wore a +1.50 D addition (the P1 group) and 14 wore a +2.00 D addition (the P2 group). Refractive error, corneal curvature, axial length, vitreous depth, and intraocular pressure were measured at every examination. Height was measured as an index of general growth. RESULTS: Progressive lenses significantly retarded the progression of the myopia in these children. Initially, the mean refractive error of the SV group was -3.67 D, of the P1 group was -3.73 D, and of the P2 group was -3.67 D. The mean myopic progressions over the 2 years of the study were -1.23, -0.76, and -0.66 D for the SV, P1, and P2 groups, respectively. CONCLUSION: Progressive lenses reduce the progression of myopia. It may be that the interaction of the progressive lenses with the accommodation system is the cause of this reduction in myopia progression because the +2.00 D addition appeared more effective than the +1.50 D addition in slowing the progression.     

Measurement of posterior corneal asphericity on Hong Kong Chinese: A pilot study

The posterior comeal p-value and apical radius of 60 Hong Kong Chinese were assessed. The values were derived based on the information of the anterior corneal topography and the corneal thickness in different regions. The mean posterior corneal apical radius along the horizontal meridian was 6.51 mm (SD ± 0.40 mm) and the p-value was 0.34 (SD ± 0.38). The apical radius is greater while the p-value is smaller than a previous study using a similar principle. This may indicate a flatter posterior cornea and greater peripheral flattening in Hong Kong Chinese. No significant difference between the nasal and temporal corneal thickness, nasal and temporal posterior p-value and apical radius was demonstrated The right and left eyes were also similar in different ocular parameters apart from a smaller anterior corneal p-value on the fight eye (R eye: 0.70 ± 0.13: L eye: 0.67 ± 0.12), but the difference may not be significant clinically. The method used here is simple and the generation of posterior corneal topography is informative.     

Prevalence of myopia in local and international schools in Hong Kong.

PURPOSE: This study aims to investigate genetic and environmental influences on physiological myopia by studying the difference in myopia prevalence between local schools and international schools in Hong Kong. METHODS: Vision screening was carried out in local and international schools for students 13 to 15 years old. Types of refractive error were identified by visual acuity measurement, the presence of spectacles, a simple refraction, and the use of plus and minus ophthalmic lenses. RESULTS: Three local schools and six international schools participated in the study. Two hundred eighty-nine students were from the local schools, and 789 students were from the international schools. Prevalence of myopia at the local schools ranged from 85 to 88%, whereas it ranged from 60 to 66% in the international schools. Students in the international schools were subdivided into Chinese origin, white, mixed Chinese, and Asian. Prevalence of myopia was highest in the Chinese group (82.8%) and lowest in the white group (40.5%). There was no age or gender difference in the prevalence of myopia. CONCLUSIONS: Hong Kong Chinese students had a higher prevalence of myopia regardless of whether they studied in local or international schools when compared with other ethnic groups, such as whites. This further supports a genetic input into myopia development.     

Effect of parental myopia on the development of myopia in Hong Kong Chinese

A representative sample of Hong Kong Chinese children was followed from 7 to 12 years of age. Refractive error was measured every year (n = 123 at age 7 years and n = 83 at age 12 years), the axial length of the eye was measured at age 12 years (n = 81) and the refractive status of the parents was also determined. Thirty-one percent of the parents in the sample were myopic and at the age of 12 years 53% of the children were myopic. There was no association between the refractive status of the parents and whether or not a child had myopia. The probability of a 12-year-old child with early-onset myopia having at least one myopic parent was 0.55 and the probability of myopic parents having a myopic child was 0.6. There was no difference in the refractive error or the axial length of 12-year-old children according to whether neither, one or both parents were myopic. The genetic influence on myopia may be different in Caucasian and Chinese children, although it is also possible that non-expression of the genotype in the parents may have confounded the determination of the inheritance pattern of myopia in Hong Kong Chinese children.     

驻香港部队战士外伤性前房积血的临床治疗分析

目的:探讨眼球钝挫伤引起的前房积血的治疗方法。方法:对我院2009-01/2010-10收治的32例32眼外伤性前房积血战士资料进行回顾性分析。结果:治疗后32眼中吸收时间分别为Ⅰ级积血1～4d;Ⅱ级积血3～10d;Ⅲ级积血7～14d。积血吸收后视力为0.1～0.5者2例,0.6～1.0者12例,1.0以上者18例。结论:及时合理的治疗是外伤性前房积血视力恢复的关键,做好前房积血的预防宣教是保障部队战斗力的必要措施。