Brian Brown

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.

The Effect of Amblyopia on Fine Motor Skills in Children

PURPOSE In an investigation of the functional impact of amblyopia in children, the fine motor skills of amblyopes and age-matched control subjects were compared. The influence of visual factors that might predict any decrement in fine motor skills was also explored. METHODS Vision and fine motor skills were tested in a group of children (n = 82; mean age, 8.2 +/- 1.7 [SD] years) with amblyopia of different causes (infantile esotropia, n = 17; acquired strabismus, n = 28; anisometropia, n = 15; mixed, n = 13; and deprivation n = 9), and age-matched control children (n = 37; age 8.3 +/- 1.3 years). Visual motor control (VMC) and upper limb speed and dexterity (ULSD) items of the Bruininks-Oseretsky Test of Motor Proficiency were assessed, and logMAR visual acuity (VA) and Randot stereopsis were measured. Multiple regression models were used to identify the visual determinants of fine motor skills performance. RESULTS Amblyopes performed significantly poorer than control subjects on 9 of 16 fine motor skills subitems and for the overall age-standardized scores for both VMC and ULSD items (P < 0.05). The effects were most evident on timed tasks. The etiology of amblyopia and level of binocular function significantly affected fine motor skill performance on both items; however, when examined in a multiple regression model that took into account the intercorrelation between visual characteristics, poorer fine motor skills performance was associated with strabismus (F(1,75) = 5.428; P = 0.022), but not with the level of binocular function, refractive error, or visual acuity in either eye. CONCLUSIONS Fine motor skills were reduced in children with amblyopia, particularly those with strabismus, compared with control subjects. The deficits in motor performance were greatest on manual dexterity tasks requiring speed and accuracy.

Repeatability and intercorrelations of standard vision tests as a function of age.

Purpose We assessed repeatability and intercorrelations of five standard vision tests in subjects with normal vision. Methods Seventy-eight subjects (aged 21 to 68 years) completed five measurements each of high- and low-contrast visual acuity, near visual acuity and contrast sensitivity (Pelli-Robson chart). Results Except for correlations between high- and low-contrast visual acuity (r = 0.78), intercorrelations between tests were low to moderate (r < 0.5). For each measure, variability for the group was about one line on the chart (one triplet for the Pelli-Robson chart) and the minimum variability for an individual subject was about one third of this. On average, 1 to 2 lines can be expected to be lost over the normal lifespan on each test. Variability in responses did not increase significantly with age for any test. Conclusions The criterion for judging change on commonly used clinical vision tests is about one line for subjects over a wide age range.

Age-Related Changes in Contrast Sensitivity in Central and Peripheral Retina

Eight young (average age 20.4 years) and eight elderly (average age 64.4 years) observers took part in three experiments designed to study age-related changes in peripheral retinal function. A further eight young (average age 22.3 years) and eight elderly (average age 63.8 years) observers took part in a replication of experiment 3. All observers had normal or better-than-normal visual acuity and no evidence of ocular pathology. All testing was monocular and the eye with better visual acuity was used. In the first experiment contrast sensitivity was measured in central retina and 10 deg temporally, at spatial frequencies of 0.2, 0.8, 2.0, and 5.0 cycles deg−1. Young observers had better contrast sensitivities than older observers, but only at higher spatial frequencies (2.0 and 5.0 cycles deg−1). For both groups, contrast sensitivity was poorer with peripheral presentation of stimuli than with central presentation, but not for the lowest spatial frequency used (0.2 cycle deg−1). In the second experiment observers had to detect the presence of a sharp edge (square-wave luminance profile), while in the third and fourth experiments the target was a ‘fuzzy’ edge (sine-wave profile). Edges were again presented centrally or 10 deg temporally. As expected from the data of experiment 1, young observers were better able to detect the sharp edge than were the older observers in both central and peripheral viewing conditions. For both age groups, edge detection was better during central viewing than during peripheral viewing. However, contrary to expectations based on the results of experiment 1, detection of the fuzzy edge was better for central than for peripheral viewing for both age groups in experiments 3 and 4. The apparent (and expected) equality of performance found in experiment 3 for young and elderly observers in detecting the fuzzy edge was shown to be due to the range of contrast values used. When appropriate contrast values were used in experiment 4, young observers detected fuzzy edges presented in central retina better than did elderly observers. The results of experiment 1 show sparing of the ability to process low spatial frequencies across (i) age and (ii) retinal location, and are discussed in terms of the notion of (i) models of age-related loss of visual function and (ii) cortical magnification. The results of experiments 2, 3, and 4 provide some support for the proposition that the contrast sensitivity of observers may be used to predict their performance on other visual tasks. However, consideration must be given to the influence of the nature of the psychophysical task required of observers when making such predictions.

Diurnal variation of intraocular pressure and the overriding effects of sleep.

ABSTRACT Intraocular pressure (IOP) was recorded regularly over a 24‐h period in 13 normal subjects. All subjects showed a dramatic rise in IOP after sleep, ranging from 37 to 248%. In a second experiment, IOP decreased when 15 subjects remained upright and awake throughout the night. When sleep was not permitted IOP was lowest at 3:00 a.m. (0300); when six of these subjects were permitted to sleep from 0600 to 0800, they showed a rapid and significant increase in IOP of up to 150%, whereas the remaining nine subjects showed (posturally induced) increases of up to 38%.

Review of the tear break-up time and a closer look at the tear break-up time of Hong Kong Chinese

The technique of assessing tear stability using the fluorescein instillation technique has been widely used in the clinical diagnosis of “dry eye” and in the screening of potential contact lens wearers. Various inconsistencies in the application of the tear break-up time (TBUT) techniques and the results obtained were noted in the literature and this review summarizes the differences and the conclusions of various investigators. The reliability of this technique using two different methods of observation was examined and the mean TBUT of Hong Kong Chinese subjects (HK-Chinese) was determined. We conclude that the TBUT can be measured reliably using either the scanning or full beam method in most patients. The mean TBUT of HK-Chinese is approximately 8 s and about 70% of HK-Chinese have TBUTs less than 10 s.

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.

Reading Performance in Low Vision Patients: Relation to Contrast and Contrast Sensitivity

Closed circuit television (CCTV) systems have proven useful in professional and recreational rehabilitation of the partially sighted. However, the parameters for optimum performance on such systems have not been examined. This investigation shows that contrast is an important parameter in CCTV reading performance; for many patients, even slight contrast reductions significantly reduce reading performance. Distance acuity is not a good predictor of CCTV reading performance, nor is performance on conventional contrast sensitivity measures. However, a commercially available test for contrast sensitivity (the Arden plates) may be useful for predicting CCTV reading performance.

Investigation of retinitis pigmentosa using the multifocal electroretinogram

Retinitis pigmentosa (RP) patients have pathological changes in both the macula and the periphery, and are known to have abnormal electroretinograms (ERGs). The response densities measured by the multifocal electroretinogram (MERG) in the macula and pericentral retina were greatly reduced in RP. In photopic conditions, some patients had relatively better ERG responses in the macula than in the pericentral retina, and this agreed with the finding that there is usually relatively well‐preserved macular function in RP. In scotopic conditions, both macula and pericentral retina gave poor responses. There was very little increase in response as stimulus luminance increased in RP. The topographical mapping of the MERG results can provide objective, localized assessment of retinal function.

Contribution of vision variables to mobility in age-related maculopathy patients.

ABSTRACT Can mobility performance be predicted from measures of vision function? This study addressed this question by measuring a series of vision variables including visual acuity, visual fields, and differential motion sensitivity in a group of patients with age‐related maculopathy (ARM) and a group of age‐matched normals. Mobility performance at three adaptation levels was determined objectively on an indoor course. The results indicate that for the patients with ARM, mobility variables can be predicted from measures of vision function, including differential velocity sensitivity, and that simple variables such as time taken to complete the course and average speed are those which relate best to vision.