The purpose of this study was to compare the intraocular pressure (IOP) values measured with the Tono-Pachymeter NT530P (Tonopachy™) and the iCare® rebound tonometer (iCare®) with those obtained by the Goldmann applanation tonometer (GAT). The right eyes of 105 subjects aged 18 to 82 years (mean age = 29.27 ± 14.67 years) were assessed with the three tonometers. Central corneal thickness (CCT) was measured first using the Tonopachy™ and then IOP was measured by Tonopachy™, iCare® and GAT. The data was analyzed with descriptive statistics, paired t-test, correlation and regression analysis. The Bland-Altman method of analysis was used to evaluate agreements between the sets of data from the three devices. The CCT values ranged from 440 µm to 606 µm (mean= 518.49 ± 33.01 µm). There was little or no correlation between CCT and IOP for any of the instruments used in this study (r = 0.29 for Tonopachy™, r = 0.22 for iCare®, r = 0.17 for GAT). The mean IOP measured with the Tonopachy™ was 14.31 ± 3.57 mmHg (range 8.7 mmHg to 31 mmHg) and 16.64 ± 4.38 mmHg (range 8 mmHg to 32 mmHg) using the iCare®. The mean IOP measured with the GAT was 14.79 ± 3.09 mmHg (range 8.7 mmHg to 29.7 mmHg). Using the Bland-Altman method, the upper and lower limits of agreement between the Tonopachy™ and GAT, iCare® and GAT, iCare® and Tonopachy™ were 5.1 mmHg and –4.2 mmHg, 8.6 mmHg and –4.9 mmHg, 7.5 mmHg and –2.8 mmHg respectively. In 79.1% of the eyes studied, the mean IOP difference between Tonopachy™ and GAT was less than 3 mmHg and in 20.9% of the eyes, the difference was greater than 3 mmHg. However, mean IOP differences of greater than 3 mmHg were obtained by iCare® in comparison with GAT (40%) and Tonopachy™ (34.3%) respectively. Findings of this study suggest that the Tonopachy™ yielded IOP readings that were consistent with those of GAT values while iCare® yielded higher IOP values compared to both GAT and Tonopachy™. (S Afr Optom 2011 70(3) 109-116)
Background: Oculocutaneous albinism results in defects of the visual pathway and ocular structures.Aim: To determine the ocular findings and vision status of learners with oculocutaneous albinism (OCA) as well as to establish the level of visual acuity, contrast sensitivity and reading rate improvements following optical correction.Setting: Three special education schools in KwaZulu-Natal, South Africa.Methods: A total of 81 learners with OCA participated in this study. Testing procedures included logMAR distance and near visual acuity (VA) measurements, cover tests, retinoscopy (dry), subjective refraction, tangent screen, ophthalmoscopy, contrast sensitivity and reading rate determination. Results:The majority of participants (96.3%) had wheat straw coloured hair and 95.1% had grey irides. All the learners presented with iris-transillumination and an absent foveal reflex and all but one exhibited nystagmus. Esophoria and esotropia represented 72.8% of binocular vision anomalies. Myopic astigmatism was noted in 41.4% of the learners while with the rule astigmatism was predominant (64%). Following optical correction, VA significantly improved from a range of 0.50 to 1.40 logMAR to a range of 0.5 to 1.06 logMAR for distance (p < 0.05) and from a range of 0.40 to 1.30 logMAR to a range of 0.30 to 1.08 logMAR) for near (p < 0.05). In addition, contrast sensitivity improved from a range of 0.48 to 1.92 logCS to a range of 0.88 to 1.92 logCS (p < 0.05). However, the reading rate did not show any significant improvement following optical correction (p > 0.05). Conclusion:Learners with OCA exhibited various ocular and vision defects which impair visual functions. Their VA and contrast sensitivity could be significantly improved with optical correction; however, their reading rate was not improved.
Background: It has been suggested that retinal thickness varies with demographic variables. Understanding the influence of demographic variables on retinal thickness could improve our knowledge of risk factors for retinal pathologies. Previous studies have focused exclusively on white and African-American populations, with limited attention to black and Indian populations.Aim: To compare retinal thickness in black and Indian myopic students at the University of KwaZulu-Natal (UKZN).Methods: A cross-sectional comparative research design was used. The study was conducted at UKZN, Westville campus. Retinal thickness was measured in 80 healthy myopic students using the Fourier/spectral domain iVue 100 optical coherence tomographer. Retinal thickness measurements of the right and left eyes showed significant correlations, therefore data from only the right eyes were analysed. Racial and gender variations in retinal thickness of the nine Early Treatment Diabetic Retinopathy Study (ETDRS) segments were assessed.Results: The mean central foveal thickness in black participants was 238 μm compared with 243 μm in Indian participants (p = 0.06). Indian participants had thicker parafoveal thickness measurements whilst black participants had thicker perifoveal thickness measurements. Male participants had thicker retinal thickness measurements in all nine ETDRS segments than female participants. Central foveal thickness showed no significant correlation with spherical equivalent (r = -0.14, p > 0.05) or axial length (r = 0.09, p > 0.05).Conclusion: The average central foveal thickness was slightly thinner in black and female participants than in Indian and male participants. Optometrists and ophthalmologists should consider these differences when evaluating black and Indian individuals with foveal retinal diseases.
Aim: To compare retinal nerve fibre layer (RNFL) thickness in black and Indian myopic students at the University of KwaZulu-Natal.Method: Eighty (40 black and 40 Indian) participants of both genders and aged between 19 and 24 years (mean and standard deviation: 21 ± 1.7 years) were included in the study. Refractive errors were assessed with the Nidek AR-310A auto-refractor and via subjective refraction. RNFL thicknesses were then measured using the iVue-100 optical coherence tomography device. Axial lengths were measured with the Nidek US-500 A-scan ultrasound device. Data were analysed by descriptive statistics, t-tests, Pearson’s correlation coefficients and regression analysis.Results: The mean myopic spherical equivalent was significantly more negative amongst the Indian (-2.42 D ± 2.22 D) than amongst the black (-1.48 D ± 1.13 D) (p = 0.02) participants.The mean axial length was greater amongst the black (23.35 mm ± 0.74 mm) than amongst the Indian (23.18 mm ± 0.87 mm) participants but the difference was not significant. In the total sample (n = 80), the average global RNFL thickness ranged from 87 μm to 123 μm (105 μm ±9 μm). Mean global RNFL thickness was slightly greater amongst black (108 μm ± 7 μm) than amongst Indian (102 μm ± 9 μm) (p = 0.00) participants. Mean global RNFL thickness was similar for male (106 μm ± 7 μm) and female (105 μm ± 10 μm) (p = 0.79) participants.A positive and significant association between myopic spherical equivalent and global RNFL thickness was found for the total sample (r = 0.36, p = 0.00) and for Indians (r = 0.33, p = 0.04)but not for the black (r = 0.25, p = 0.13) participants. There was a negative and significant correlation between axial length and global RNFL thickness amongst the Indian participants (r = -0.34, p = 0.03) but not amongst the total sample (r = -0.12, p = 0.30) or the black (r = 0.06, p = 0.73) participants.Conclusion: The findings suggest that racial differences in RNFL thickness need to be considered in the clinical examination and screening for glaucoma and other optic nerve pathologies amongst black and Indian people. Additionally, the possible influences ofrefractive error and axial length should be considered when evaluating RNFL thickness.
Purpose: To investigate the effects of spectacle and telescope corrections on visual acuity (VA), contrast sensitivity (CS) and reading rates (RR) in students with oculocutaneous albinism (OCA). Methods: An observational study design was conducted on 81 students with OCA. Distance and near VA, CS and RR were measured without correction, with spectacle correction and with a combination of spectacle correction and telescopes. Results: The mean distance and near VA values with a combination of spectacle correction and telescopes were significantly better than those without correction and with spectacle correction alone (p = 0.01). Mean CS values achieved with spectacles alone were significantly better than those obtained with a combination of spectacles and telescopes (p = 0.01). There was no significant difference between logCS values obtained without correction compared to those obtained with a combination of spectacle correction and telescopes. There were no significant differences between RR values obtained with a combination of spectacles and telescopes and those without and with spectacle correction alone (all p > 0.05). Conclusion: This article provides valuable information to eye care practitioners on the effects of spectacles and telescopes on visual acuity, contrast sensitivity and reading rate in students with OCA. Keywords: Oculocutaneous albinism; visual acuity; telescope; contrast sensitivity; reading rate.
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