Repeatability and reproducibility of retinal nerve fibre layer thickness measurements with the iVue-100 optical coherence tomographer

Background: Accurate and repeatable measurements of the retinal nerve fibre layer (RNFL) thickness are important in the diagnosis and management of glaucoma and other disorders. Objective: To assess the repeatability and reproducibility of the iVue-100 optical coherence tomographer (OCT).Methods: The thickness of the RNFL was measured for 50 healthy participants using the iVue-100 OCT. Although both eyes per participant were measured, only right eyes were analysed here. Repeatability and reproducibility of the iVue-100 OCT were assessed using the intraclass correlation coefficient (ICC), coefficient of variation (CoV), paired t-tests and Bland-Altman analysis.Results: Good intra-observer repeatability was obtained as indicated by the ICC of observer 1 (range: 0.941 - 0.976) and observer 2 (range: 0.829 – 0.953) as well by the CoV of observer 1 (range: 0.098 – 0.137) and observer 2 (0.091 – 0.132). In terms of inter-observer reproducibility, significant differences (p< 0.05) in mean measurements between the observers were noted for the average RNFL readings and in the superior and inferior quadrants as assessed with paired t-tests. Even though significant inter-session differences were found for the average RNFL thickness and the superior quadrant (p = 0.003 and p = 0.013, respectively), excellent ICCs were obtained for inter-session reproducibility (range: 0.914 – 0.979). Conclusion: The iVue-100 OCT demonstrated good repeatability and reproducibility for RNFL thickness measurements.Keywords: Retinal nerve fibre layer thickness, optical coherence tomography, repeatability, reproducibility, iVue-100 OCT

Repeatability and reproducibility of retinal nerve fibre layer thickness measurements with the iVue-100 optical coherence tomographer

Background: Accurate and repeatable measurements of the retinal nerve fibre layer (RNFL) thickness are important in the diagnosis and management of glaucoma and other disorders. Objective: To assess the repeatability and reproducibility of the iVue-100 optical coherence tomographer (OCT). Methods: The thickness of the RNFL was measured for 50 healthy participants using the iVue-100 OCT. Although both eyes per participant were measured, only right eyes were analysed here. Repeatability and reproducibility of the iVue-100 OCT were assessed using the intraclass correlation coefficient (ICC), coefficient of variation (CoV), paired t-tests and Bland-Altman analysis. Results: Good intra-observer repeatability was obtained as indicated by the ICC of observer 1 (range: 0.941 - 0.976) and observer 2 (range: 0.829 \u2013 0.953) as well by the CoV of observer 1 (range: 0.098 \u2013 0.137) and observer 2 (0.091 \u2013 0.132). In terms of inter-observer reproducibility, significant differences (p< 0.05) in mean measurements between the observers were noted for the average RNFL readings and in the superior and inferior quadrants as assessed with paired t-tests. Even though significant inter-session differences were found for the average RNFL thickness and the superior quadrant (p = 0.003 and p = 0.013, respectively), excellent ICCs were obtained for inter-session reproducibility (range: 0.914 \u2013 0.979). Conclusion: The iVue-100 OCT demonstrated good repeatability and reproducibility for RNFL thickness measurements

Distribution of corneal thickness measured using optical coherence tomography in South African young adults

Background: Corneal thickness measurements have various diagnostic and therapeutic applications. Studies have reported on the distribution of corneal thickness measurements in Caucasian and Asian subpopulations with limited focus on African subpopulations. Aim: The goal of this study was to examine the distribution of corneal thickness measured using optical coherence tomography in a South African young adult population. Setting: The study was conducted at the eye clinic at the University of KwaZulu-Natal. Methods: The study used a quantitative cross-sectional research design and participants were recruited using two-stage random sampling. Seven hundred participants consisting of 50% South African blacks and 50% South African Indians aged between 17 and 30 years were included. The sample included an equal distribution of male (n = 350) and female (n = 350) participants. Corneal thickness was measured using the Fourier-domain Optovue iVue100 optical coherence tomographer. As the data from the right and left eyes showed high levels of interocular symmetry, data from only the right eyes were analysed using descriptive and inferential statistics. Results: The mean age of the sample was 20.42 ± 1.80 years. Corneal thickness measurements resembled Gaussian curves (p ≥ 0.095) and the mean central corneal thickness (CCT) was 501.91 µm. Corneal thickness at the thinnest point was 495.73 µm and 1.23% thinner than the mean CCT measurement (p < 0.001). Males had slightly higher corneal thickness measurements than females but these differences (0.35 µm – 3.93 µm) were not significant (p ≥ 0.137). Corneal thickness varied significantly with refractive error and was lowest in emmetropes followed by myopes and then hyperopes. Conclusion: Corneal thickness measurements are normally distributed in South African young adults. The mean CCT is different from that reported in other populations and lower than the calibrated CCT measurement for Goldmann applanation tonometry. Eye care personnel should consider the characteristics of corneal thickness measurements and its implications on intraocular pressure measurements when examining South African individuals

Repeatability of central and peripheral corneal thickness measurements with the iVue100 optical coherence tomographer

Background: Accurate assessment of corneal thickness is essential in corneal refractive surgery, contact lens wear and corneal pathology. Aim: To assess the repeatability (intra-observer, inter-observer and inter-session) of central (0 mm – 2 mm), mid-peripheral (2 mm – 5 mm) and peripheral (5 mm – 6 mm) corneal thickness measurements using the iVue 100 spectral domain optical coherence tomographer (SD-OCT). Setting: Optometry Eye Clinic at the University of KwaZulu-Natal (UKZN). Methods: Corneal thickness measurements were taken on 50 healthy participants by two observers independently. A second set of readings was taken by one observer on another session. Repeatability was assessed using Bland–Altman analysis, the intraclass correlation coefficient, coefficient of variation and one-way analysis of variance (ANOVA) analysis. Results: For all corneal regions, the intraclass correlation coefficients for observer one ranged from 0.942 to 0.999 and that for observer two ranged from 0.946 to 0.999, indicating good intra-observer repeatability. Using linear regression, the corneal thickness measurements were found to be comparable (within 1 µm of each other) in all regions with the exception of the nasal and temporal mid-periphery and periphery. The inter-session repeatability was based on the measurements of observer one only with the mean differences ranging from 0.02 µm to 0.63 µm. Linear regression revealed no significant differences between session 1 and session 2 (p > 0.05) except for the measurement of minimum corneal thickness. Conclusion: This study found evidence of good intra-observer, inter-observer and intersession repeatability of central, mid-peripheral and peripheral corneal measurements with the iVue 100 SD-OCT

A review of African studies on central corneal thickness

Recently, there has been increasing interest in understanding central corneal thickness (CCT) measurements in various populations. This may be related to the influence of CCT in the diagnosis, classification and management of glaucoma. In addition, CCT measurements are also important for monitoring corneal diseases and contact lens wear, indicating the overall health of the cornea and assessing eligibility for refractive surgery. This article reviews studies that have reported CCT measurements in non-glaucomatous African sub-populations. The CCT measurements, gender associations and limitations of these studies are highlighted. The findings of these studies and their implications are discussed in relation to global studies reporting on CCT measurements

Near vision anomalies in Black high school children in Empangeni, South Africa: A pilot study

Background: The ability to read efficiently and comfortably is important in the intellectual development and academic performance of a child. Some children experience difficulties when reading due to symptoms related to near vision anomalies. Aim: To explore the feasibility of conducting a large study to determine the prevalence, distribution and characteristics of near vision anomalies in high school children in Empangeni, South Africa. Methods: The study was a cross sectional descriptive pilot study designed to provide preliminary data on prevalence, distribution and characteristics of near vision anomalies in a sample of high school-children in South Africa. Study participants comprised 65 Black children (30 males and 35 females), ages ranged between 13 and 19 years with a mean age and standard deviation of 17 ± 1.43 years. The visual functions evaluated and the techniques used included visual acuity (LogMAR acuity chart), refractive error (autorefractor and subjective refraction), heterophoria (von Graefe), near point of convergence (push-in-to-double), amplitude of accommodation (push-in-to-blur) accommodation facility (± 2 D flipper lenses), relative accommodation, accommodation response (monocular estimation method) and fusional vergences (step vergence with prism bars). Possible associations between symptoms and near vision anomalies were explored using a 20-point symptoms questionnaire. Results: Prevalence estimates were: Myopia 4.8%, hyperopia 1.6% and astigmatism 1.6%.  For accommodative anomalies, 1.6% had accommodative insufficiency while 1.6% had accommodative infacility. For convergence anomalies, 3.2% had receded near point of convergence, 16% had low suspect convergence insufficiency, no participant had high suspect convergence insufficiency, 1.6% had definite convergence insufficiency and 3.2% had convergence excess. Female participants reported more symptoms than the males and the association between clinical measures and symptoms were not remarkable. Conclusion: Although the overall prevalence of near vision anomalies was low,  convergence anomalies were found to be more prevalent than refractive and accommodative anomalies. Symptoms were not significantly associated with near vision anomalies.  Overall, the pilot project reveals that it is feasible to conduct the study on a large scale with minor modifications. Identification and referrals for near vision anomalies are important steps towards diagnosis and treatment which will minimize discomfort with reading and subsequent poor performance which may be associated with such anomalies

Ocular injuries and eye care seeking patterns following injuries among cocoa farmers in Ghana

Background: The work environment of cocoa farmers exposes them to several ocular hazards that predispose them to eye diseases and injuries. However, the extent of ocular injuries and health seeking patterns following these injuries are unknown among cocoa farmers in Ghana.Objectives: To determine the prevalence of ocular injuries and health seeking behaviour following injury among cocoa farmers in Ghana.Methods: Five hundred and fifty six participants were recruited through simple random sampling using a multistage approach from four cocoa growing districts in Ghana. A structured questionnaire was used to collect relevant information such as demography, ocular hazards and injuries experienced. An ocular examination was also conducted to assess the eye health of the participants. Descriptive and regression statistics were used to analyze the data. The rate of ocular injuries was calculated by using the number of injuries reported that resulted in lost work time/days divided by the number of worker years at risk of injury (sum of years worked in cocoa farms for all the participants).Results: The rate of ocular injuries was 11.3/1000 worker years (95% CI: 9.4 - 31) which led to lost work time of 37.3/1000 worker years (95% CI: 34.1 - 40.8). The major causes of ocular injury were plants/branches (n=73, 51.1%), chemicals (n=27, 18.9%), cocoa pod/husk (n=14, 9.8%) and occurred mostly during weeding, harvesting and chemical spraying. Few (n=34, 6.1%) participants reported the use of ocular protection. Fifty-five (38.5%) participants visited the local chemical shops, while 37 (25.9%) visited hospitals/clinics for ocular treatment of their injuries.Conclusion: There is a high rate of ocular injuries among cocoa farmers who make insufficient use of appropriate eye care services. There is the need for eye health education among cocoa farmers in Ghana.Keywords: Ocular injuries, cocoa farmers, ocular protective device, eye care service

A review of vision screening methods for children

Abstract: Background: What constitutes an appropriate vision screening protocol is controversial, because the tests or methods are expected to be cost-effective, expedient and easy but efficient in detecting visual anomalies among children. Aim: This review intends to compare the different vision screening tests for children and methods in the interest of identifying the most effective screening method from the standpoint of validity, public acceptance, expediency and cost. Method: The literature search was performed for this review using the Medline, Science Direct and EBSCOhost databases. The search terms used were vision screening methods or tests, children’s vision screenings, computer software programs and vision screening instruments. The inclusion criteria for the articles reviewed were all types of articles related to vision screening methods. The exclusion criteria were all articles for which full text was not available and those not available in English. Eighty articles were analysed, of which 33 were found to have complied with the inclusion criteria and were selected. From the first round of articles retrieved, additional references were identified by a manual search among the cited references. Results: Evidence from the literature reviewed demonstrated that the conventional vision screening method (isolated and combination tests) is the method commonly used to detect a range of relevant visual anomalies among the schoolgoing age group (≥ 6 years) and drew attention to the need for training of vision screening personnel. However, in addition to the conventional method, other vision screening methods include instruments as an adjunct for screening preschoolers and those difficult to screen (≤ 6 years). Conclusion: Inconsistencies in what constitutes an appropriate vision screening method still exist, especially with the booming market of using computer software programs, which still needs to be validated

Ocular injuries and eye care seeking patterns following injuries among cocoa farmers in Ghana.

Background: The work environment of cocoa farmers exposes them to several ocular hazards that predispose them to eye diseases and injuries. However, the extent of ocular injuries and health seeking patterns following these injuries are unknown among cocoa farmers in Ghana. Objectives: To determine the prevalence of ocular injuries and health seeking behaviour following injury among cocoa farmers in Ghana. Methods: Five hundred and fifty six participants were recruited through simple random sampling using a multistage approach from four cocoa growing districts in Ghana. A structured questionnaire was used to collect relevant information such as demography, ocular hazards and injuries experienced. An ocular examination was also conducted to assess the eye health of the participants. Descriptive and regression statistics were used to analyze the data. The rate of ocular injuries was calculated by using the number of injuries reported that resulted in lost work time/days divided by the number of worker years at risk of injury (sum of years worked in cocoa farms for all the participants). Results: The rate of ocular injuries was 11.3/1000 worker years (95% CI: 9.4 - 31) which led to lost work time of 37.3/1000 worker years (95% CI: 34.1 - 40.8). The major causes of ocular injury were plants/branches (n=73, 51.1%), chemicals (n=27, 18.9%), cocoa pod/husk (n=14, 9.8%) and occurred mostly during weeding, harvesting and chemical spraying. Few (n=34, 6.1%) participants reported the use of ocular protection. Fifty-five (38.5%) participants visited the local chemical shops, while 37 (25.9%) visited hospitals/clinics for ocular treatment of their injuries. Conclusion: There is a high rate of ocular injuries among cocoa farmers who make insufficient use of appropriate eye care services. There is the need for eye health education among cocoa farmers in Ghana. Keywords

Knowledge, attitudes and practices of contact lens use in a South African adolescent population

Background: Contact lens usage is becoming increasingly popular amongst young people. Assessing their knowledge, attitudes and practices in relation to contact lens wear is therefore important, so that gaps in understanding or incorrect practices can be rectified to promote continued safety and success of contact lens wear. Objectives: This study aimed to assess and describe the knowledge, attitudes and practices of contact lens wearers aged 18 to 30 years, in the greater Durban area of South Africa. Methods: A semi-structured questionnaire was used to assess the knowledge, attitudes and practice of the participants. Results: Two hundred and forty six participants completed the survey. Young contact lens wearers in this sample generally had poor knowledge with regards to appropriate hygiene and contact lens wear complications. Despite wearers exhibiting a positive attitude with satisfactory hand hygiene and lens cleaning practices, important aspects such as lens case hygiene, storage and lens removal practices were found to be unsatisfactory. Compliance with after-care visits was also unsatisfactory. Conclusion: There is a need for contact lens practitioners to educate young contact lens wearers regarding appropriate contact lens-related care, to promote long term ocular health and contact lens-related safety