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Abstract This study investigated whether there is a relationship between reading age and clinical optometric tests that have varying degrees of spatial loading in their design. Spatial loading in this context is the demand on the visual system to process information about the relative position and orientation of stimuli. A total of 112 children aged 8-11 years were assessed using saccadic eye movement and rapid naming tasks with varying spatial loads. All were subtests of Garzia's Developmental Eye Movement test and Liubinas' SeeRite Reading Diagnostic Programme. Variability in load was achieved by comparing rapid naming of numerals vs the spatially loaded letters p, d, b, q; and by comparing the speed of reading numerals presented in increasingly complex arrays. Reading Age was assessed independently and results were analysed by multiple logistic regression. Spatially loaded naming tasks performed at speed exposed a Spatial Loading Factor which clearly differentiates children at risk with reading.

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While private hospitals provide an important access point for low vision services for children in urban India, little is known about this service delivery route. A cross sectional survey was done of consecutive records of 220 children presenting at a newly opened paediatric low vision centre in a private eye hospital in Hyderabad. On presentation, 49% of the children were classified as moderately visually impaired, 31% were severely visually impaired and 20% were blind. The four major causes of visual impairment were the hereditary/genetic conditions of congenital glaucoma, hereditary macular degeneration, retinitis pigmentosa and albinism. Approach magnification was sufficient for required near tasks in all pre-school children and about 50% of school children. Provision of a distance refraction decreased the prevalence of severe visual impairment and blindness by 31%. The most commonly prescribed low vision devices were spectacles indicating a key role for optometry in the management of visual impairment in Indian children. Establishment of low vision clinics in existing Indian eye hospitals using associated optometric staff would be a cost effective method to minimise visual impairment in Indian children.

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PURPOSE: To examine whether Na(+)-K(+)-2Cl(-) cotransport has the potential to contribute to corneal endothelial ion and fluid transport in cultured and fresh bovine corneal endothelial cells. METHODS: Cl- and Na+ sensitive fluorescent dyes were used to measure furosemide-dependent ion fluxes in cultured and fresh endothelial cells. Immunoblot analysis and immunofluorescence were used to determine expression and location of the Na(+)-K(+)-2Cl(-)cotransporter (NKCC1). RESULTS: Application of furosemide (50-100 microM) reduced Cl- and Na+ influx in approximately 50% of trials using cultured cells and only 10% of trials with fresh cells; however, in all cases pretreatment with furosemide slowed Cl- efflux when cells were bathed in Cl(-)-free Ringer's. Double-sided perfusion of cultured cells indicated that furosemide-sensitive Cl- fluxes were located on the basolateral side. Immunoblot analysis revealed 174-kDa bands in both fresh and cultured cells, but the bands were denser in fresh endothelial cells. Immunofluorescence showed distinct lateral membrane staining in addition to significant amounts of perinuclear staining. CONCLUSIONS: The Na(+)-K(+)-2Cl(-) cotransporter is present in both fresh and cultured bovine corneal endothelium, and the expression is apparently higher in the fresh cells. The cotransporter is present on the lateral membrane consistent with a role in loading endothelial cells with Cl-, thereby possibly contributing to a transendothelial Cl- flux. However, in the resting cell, net flux through the transporter is often not apparent.

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PURPOSE: To more fully investigate the effect of hyperglycemia on the aerobic metabolism of the corneal epithelium. METHODS: Corneal epithelial oxygen uptake rates and adenosine triphosphatase (ATPase) activities were measured in alloxan-induced diabetic and control rabbits over a 10 week period. RESULTS: A transient reduction in epithelial oxygen uptake rate was seen at week 1. A chronic 14% reduction in oxygen consumption occurred after 6 weeks of hyperglycemia. Epithelial ouabain-sensitive ATPase activity was unaffected by 10 weeks of hyperglycemia. Epithelial ouabain-insensitive ATPase activity decreased 14% after 10 weeks of hyperglycemia. CONCLUSIONS: Ten weeks of hyperglycemia in the alloxan induced diabetic rabbit was associated with a 14% decrease in corneal oxygen uptake, a 14% decrease in corneal epithelial ouabain-insensitive ATPase activity and no change in corneal epithelial ouabain-sensitive ATPase activity. The Crabtree effect may help explain some of the clinical signs seen in the diabetic cornea as well as explaining why diabetic patients can wear contact lenses with minimal clinical problems.

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PURPOSE: To determine the visual success outcomes following treatment in an urban private eye hospital in India. METHODS: A retrospective survey was done of 4122 consecutive files of fee-paying patients admitted to a private eye hospital in Hyderabad during a 3-month period in 1996. Data obtained a minimum of 4 months after completion of treatment included age, sex, diagnosis and distance visual acuity in the best eye. RESULTS: After completion of treatment 86.5% of patients had normal vision, 10.9% had low vision and 2.5% were blind. Of the people with low vision or blindness after treatment, 81.7% had a best corrected visual acuity of between 6/18 and 6/60. The 4 most common causes of low vision after treatment were unoperated cataract (20.4%), glaucoma (13.3%), diabetic retinopathy (12.4%) and retinitis pigmentosa (10.2%). CONCLUSION: The visual success rates in an urban Indian private eye hospital appear high with nearly 90% of patients achieving normal vision after the completion of treatment.

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A retrospective survey of 4,122 consecutive patient records was performed in a tertiary care eye hospital in Hyderabad, India. Data collected included age, gender, visual acuity after completion of treatment and diagnosis. 62.8% of the patients were male. After completion of treatment, 10.8% had low vision (best corrected visual acuity < 6/18 to 3/60 in the better eye) and 2.6% were blind (best correct visual acuity < 3/60 in the better eye). Most cases of low vision were found in the 50 to 70 year age group (42.9%). The most common visual acuity range after treatment amongst patients with vision loss was < 6/18 to 6/60 (71%). The 4 main causes of low vision were cataract (21.4% of low vision group), glaucoma (14.0%), diabetic retinopathy (13.0%), and retinitis pigmentosa (10.7%). The 4 main causes of blindness were glaucoma (16.3% of blind group), diabetic retinopathy (13.2%), corneal opacities (11.6%) and retinitis pigmentosa (11.6%). It is suggested that patients with low vision at the conclusion of treatment be referred to a vision rehabilitation centre. Referral should be made in cases with a best corrected visual acuity < 6/18 to 3/60 or with visual field loss to within 15 degrees of fixation. Patients aged under 50 years of age are expected to achieve maximal rehabilitation success. Motivation and vocational requirements should be assessed in older or more complex cases before referral. The data of this study show that about 10% of patients seen at a tertiary care eye hospital in India could benefit from low vision rehabilitation.

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Low vision rehabilitation often concentrates on vocational and living skills training. Nonetheless, the motivation for improving reading or travel skills may be to pursue some enjoyable recreational activity. A case report of a telescopic aid for surfing is presented, emphasizing the importance of recreation in low vision rehabilitation.

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A new method of quantifying the dynamics of the human dark adaptation function is presented. This method is based on nonlinear regression analysis and allows the derivation of a number of clinically useful indices of dark adaptation ability. The analysis method is applied to literature data describing the effect of ageing on dark adaptation and to clinical data from a retinitis pigmentosa patient. Ageing was seen to decrease the rate of adaptation in the cone portion of the dark adaptation function, and to have little effect on the rate of adaptation in the rod portion of the dark adaptation function. One case of retinitis pigmentosa was associated with increased rod and cone thresholds but little change in the rate of adaptation of the cone portion of the dark adaptation function. It is suggested that this analysis method may offer advantages in quantifying changes in dark adaptation dynamics.

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This study compares corneal thickness and corneal endothelial Na,K ATPase activity in normal and age-matched diabetic rabbits with up to 10 weeks of hyperglycemia. Corneal endothelial Na,K ATPase activity in normal rabbits increased between 10 and 20 weeks of age. Corneal thickness increased after 5 weeks of hyperglycemia. Decreased corneal endothelial homogenate Na,K ATPase activity was first seen after 10 weeks of hyperglycemia, though an earlier onset was possible due to sampling restrictions. Corneal endothelial homogenate Mg++ ATPase activity showed a transient increase after 2 to 5 weeks of hyperglycemia. This study shows that hyperglycemia in rabbit is associated with complex dynamic interactions between corneal thickness and corneal endothelial Mg++ ATPase and Na,K ATPase activities.

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PURPOSE: To compare the contact lens-induced corneal edema recovery dynamics of human subjects with type 1 diabetes with those of age- and sex-matched normal human subjects; to compare the human data with previously reported data from alloxan-induced diabetic rabbit. METHODS: Corneal edema was induced by 2 hours of closed eye wear with a thick, soft contact lens. After removal of the contact lens, central corneal thickness measurements were made at 30-minute intervals for 3 hours using optical pachometry. RESULTS: Human subjects with type 1 diabetes demonstrated a significantly slower rate of corneal edema recovery than age- and sex-matched human controls. The rate of corneal edema recovery found in this study for human subjects with type 1 diabetes is similar to that previously reported for alloxan-induced diabetic rabbits. CONCLUSIONS: The decreased corneal edema recovery ability of the patient with type 1 diabetes suggests that care should be taken when prescribing contact lens use in these people. The similarity between corneal edema recovery rates in the human subject with type 1 diabetes and the alloxan-induced diabetic rabbit supports the use of the alloxan-induced diabetic rabbit as an animal model for studies of corneal edema recovery dynamics in diabetes.

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Measurement of the topographical corneal edema response has been previously restricted by the use of optical pachometry and small sample sizes. This study uses ultrasound pachometry to measure changes in the corneal thickness of 23 subjects at 9 locations during 2 hours' wear of a thick soft contact lens. The data are analysed using both averaged and individual location data. The averaged location analysis supports the current paradigm that less edema occurs in the peripheral cornea than in the central cornea during contact lens wear. However, the individual location analysis reveals a more complex corneal edema response in which the greatest amount of edema following 2 hours' contact lens wear occurred in the central and mid-peripheral temporal cornea, in comparison with the peripheral nasal and peripheral inferior cornea which showed the least edema. The edema measured in the peripheral temporal and peripheral superior cornea following 2 hours' contact lens wear was not significantly different from that measured in the central cornea. The edema measured in the central cornea following 2 hours' contact lens wear was not significantly different from that found at any mid-peripheral location. This study demonstrates that the corneal edema response associated with 2 hours' wear of a thick soft contact lens is a complex dynamic topographical process and cannot be simply modelled using averaged data from small samples.

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The central thickness of the left eyes of 1082 New Zealand students aged 5 to 20 years were measured using optical pachometry. No significant variation in corneal thickness was found with increasing age. The mean corneal thickness of the left eye was 540 +/- 25 microns. No significant differences in corneal thickness were found when the effects of sex or cultural groupings were examined. Corneal thickness appears to remain constant between the age of 5 and 20 years, irrespective of sex or cultural grouping.

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The corneal thickness of 108 human subjects, ranging from 17 to 75 years of age, was measured using ultrasound pachometry. One central, four mid-peripheral and four peripheral corneal positions along the vertical and horizontal meridians were assessed using ultrasound pachometry. No significant differences were found in the thicknesses of the central, midperipheral or peripheral cornea with increasing age using analysis of variance. These results suggest that ageing has no significant effect on human corneal thickness between the ages of 16 to 75 years. However the high Type II error probability (beta = 0.90) suggests that 108 subjects (18 in each age group) were insufficient to adequately answer the question. Thus power analysis may help explain the conflicting reports available in literature. The diversity in data interpretation may be due to the statistically small sample sizes used in most studies. Power analysis shows that at least 80 subjects are needed in each age group (480 subjects in total) before a statistically reliable test of the null hypothesis is possible. This study emphasizes the importance of power analysis in calculating an adequate sample size.

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Corneal edema was induced by a 2-h closed-eye wear of a thick hydrogel contact lens. Corneal edema production and edema recovery responses were measured in the central and mid-peripheral (3 mm inferior) cornea of 10 younger (20.4 +/- 2.0 years) and 10 older (69.0 +/- 3.4 years) subjects using optical pachometry. The amount of edema produced was not significantly different between the two corneal locations nor between the two age groups. The edema recovery rates of the central and mid-peripheral cornea were not significantly different in either the younger or older group. The edema recovery rates at both corneal positions were significantly faster in the younger group than in the older group. The results of this study suggest that the mechanisms that control edema production and recovery in the inferior mid-peripheral cornea are similar to those previously described in central and temporal mid-peripheral locations. Ageing appears to influence the edema production and recovery mechanisms of both the central and mid-peripheral cornea in similar ways.

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.5% proparacaine HCl is commonly used for topical anaesthesia in ultrasound pachometry prior to refractive surgery. This drug is known to alter corneal epithelial adhesion. Does 0.5% proparacaine result in an alteration in corneal thickness due to changes in the corneal epithelium? Corneal thickness was measured by optical pachometry at 30 sec intervals for 15 min under 3 experimental conditions; 1) 2 drops of artificial tears, 2) 1 drop of 0.5% proparacaine, 3) 2 drops of 0.5% proparacaine. Baseline measurements were recorded before each trial. No significant differences were found between the mean corneal thicknesses measured in the baseline, 2 drops of artificial tears and 1 drop of 0.5% proparacaine conditions. The mean corneal thickness in the 2 drops of 0.5% proparacaine condition was significantly greater than those measured in the other conditions. In particular the measured corneal thickness was significantly different from the baseline measurements 1 to 2 min after instillation of the 2 drops of 0.5% proparacaine. Exponential modelling of the corneal edema recovery function demonstrated that recovery to baseline corneal thickness occurred 7 to 8 min following the instillation of 2 drops of 0.5% proparacaine. The data of this study suggest that only 1 drop of 0.5% proparacaine should be used for topical anaesthesia prior to ultrasound pachometry. This recommendation may minimize the possibility of measuring artifactually large corneal thickness estimates, and thus reduce the possibility of corneal microperforation during refractive surgery.

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The relationships between dioptric blur, pupil size, retinal eccentricity, and retinal sensitivity were investigated in the central 5 degrees of the visual field in 10 normal subjects using the Humphrey Field Analyzer. Pupil size did not influence the foveal sensitivity or retinal profile in the unblurred condition. The slope of the retinal profile was significantly steeper in the 3 mm pupil size condition (-0.62 dB/degree) than when compared to the 8 mm pupil size condition (-0.34 dB/degree), when averaged over all dioptric blur conditions. The depth of focus for the 3 mm pupil size condition (3.86 diopters) was significantly greater than that found for the 8 mm pupil size condition (1.82 D). The retinal threshold doubling eccentricity (E2) was calculated to be similar to that of grating acuity and contrast sensitivity (3.71). The data suggest that while large depth of focus effects in small pupil sizes appear to reduce the need for accurate refractive error corrections in determining perimetric retinal sensitivities, variations in the slope of the retinal profile under conditions of uncontrolled dioptric blur and pupil size may result in the artifactual sensitivity decreases. Therefore, it is recommended that measurement of pupil size and accurate correction of near refractive errors be performed to minimize the possibility of incorrect detection of central visual field defects.

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The records of 10,254 people attending rural eye clinics in South Africa during 1984-85 were analyzed to determine the reasons for presentation. The main reasons for presentation were refractive error, conjunctivitis, and cataract. It is expected that population growth plus the increased vocational needs for the correction of refractive errors will result in an increased demand for optometric services in rural eye clinics. It is suggested that optometry has a major role to play in providing primary eye care services to the underserved populations of the South African homelands.

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Altitudinal hemianopsia is a relatively rare visual field defect. A case report is presented describing a patient suffering from sudden-onset traumatic altitudinal hemianopsia. Other conditions which may produce sudden or gradual onset altitudinal hemianopsias are discussed. The importance of the optometrist being aware of the possibility of an altitudinal visual field defect in conditions of trauma to the face after motor vehicle accidents is stressed.

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The two eyes of a subject often yield correlated data. Statistical analysis which treats correlated data as if it were independent is most likely to be biased toward statistical significance; that is, the probability of a type I error is likely to be inflated. To illustrate the importance of lack of independence to the inferential process, data from an experimental design commonly used in optometric research are used to demonstrate (1) the potential magnitude of between-eye correlation, (2) the statistical bias toward a significant outcome when the between-eye correlation is ignored via inappropriate analysis, and (3) simple ways by which the bias can be avoided. The researcher must be aware of the between-eye correlation which exists for the particular effect under study, and the statistical bias that ensues from the correlation when the data are not handled correctly.

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