bluuebunny/crossref_metadata_2025 huggingface dataset:
The WHO AFRO external quality assessment programme (EQAP): Linking laboratory networks through EQA programmes
Authors: Boeras Debrah I. , Peeling Rosanna W. , Onyebujoh Philip , Yahaya Ali A. , Gumede-Moeletsi Hieronyma N. , Ndihokubwayo Jean B.
Published: October 2016

External Quality Assessment (EQA) surveys performed by the World Health Organization Regional Office for Africa (WHO AFRO) revealed the need for the strengthening of publichealth microbiology laboratories, particularly for testing of epidemic-prone diseases in theAfrican Region. These surveys revealed common issues such as supply chain managementskilled personnel, logistical support and overall lack of quality standards. For sustainableimprovements to health systems as well as global health security, deficiencies identified needto be actively corrected through robust quality assurance programmes and implementation oflaboratory quality management systems.Given all the pathogens of public health importance, an external quality assessment programmewith a focus on vaccine-preventable diseases and emerging and re-emerging dangerouspathogens is important, and should not be stand-alone, but integrated within laboratorynetworks as seen in polio, measles, yellow fever and rubella.In 2015, WHO AFRO collaborated with the US Centers for Disease Control and Preventionthe London School of Hygiene & Tropical Medicine and partners in a series of consultationswith countries and national and regional EQA providers for the development of qualityassurance models to support HIV point-of-care testing and monitoring. These consultationsrevealed similar challenges as seen in the WHO AFRO surveys. WHO AFRO brought forthits experience in implementing quality standards for health programmes, and also openeddiscussions on how lessons learned through such established programmes can be utilised tosupporting and strengthening the introduction of early infant diagnosis of HIV and viralload point-of-care testing.An optimised external quality assessment programme will impact the ability of countries tomeet core capacities, providing improved quality management systems, improving theconfidence of diagnostic network services in Africa, and including capacities to detect eventsof international public health importance.
The innovativeself - adjustable Adspecs TM
Authors: Carlson A.S.
Published: October 2016

A method of self-refraction, based onan old concept implemented with the aidof modern technology, is spectacles withadjustable lenses. The spectacle design isreferred to as the AdspecsTM. The advantageof the Adspecs is that the wearer can adjustthe powers of the lenses to suit his or hervisual needs. The power is spherical andranges from −6 to 6 D. Studies were undertakenin Ghana and South Africa. Subjectswere instructed under supervision to adjustthe powers of the Adspecs as accurately aspossible to correct their vision and obtainthe best visual acuity possible. An optometristthen refracted the patients and theresults were then compared. For the righteyes, the mean stigmatic coefficient differencefor distance vision was −0.13 D andthe standard deviation 0.89 D. For the lefteyes, the mean was −0.24 D and the standarddeviation 0.91 D. For near vision, themean for the right eyes was −0.27 D andstandard deviation 1.07 D, and for the lefteyes, the mean was −0.27 D and standarddeviation 1.23 D. The standard deviationsfor the means (at distance and near) forleft eyes were slightly greater than for theright eyes.
Opacities in the vitreous
Authors: Gillan W.D.H.
Published: October 2016

No Abstract Available
The cornea in systemic disease
Authors: Gillan W.D.H.
Published: October 2016

Systemic  disease  often  results  in  corneal signs that are easily observable by means of bio-microscopy. Optometry is in a unique position to detect the corneal manifestations of systemic disease. This review presents corneal signs of various systemic diseases. The list is not com-plete but the review rather attempts to empha-size the importance of detection, and referral, of systemic diseases.
Sports related traumatic hyphema
Authors: Mathebula S.D.
Published: October 2016

No Abstract Available
An introduction to the mathematics of ocular kinematics
Authors: MacKenzie Graeme E
Published: October 2016

The research surrounding ocular kinematics has widespread applications including the study of binocular vision, virtual reality and the detec-tion of ocular and neurologic pathologies. This field promises to have a significant impact on optometric diagnostic techniques. This paper in-troduces the terminology used in the description of eye rotations and explores a number of the mathematical approaches pertinent to the topic of ocular kinematics.
Rhino-orbital mucormycosis
Authors: Mathebula S.D.
Published: October 2016

Rhino-orbital mucormycosis is a rare but life-threatening infection that generally occurs in patients with immune deficiency. As such the condition is a medical emergency. Early rec-ognition and treatment are essential because it may lead to death within a few days. Fungal in-fections of the eye are uncommon but are being seen with increasing frequency in patients with immune deficiency.
Multiple measures of refractive state of the test eye making use of a Nidek ARK - 10000 OPD- Scan
Authors: Gillan W. D. H.
Published: October 2016

Introduction: It is important for the users of automated instruments that measure refractive state to know that the results obtained from such instruments are accurate and repeatable. This study was conducted to investigate the repeat-ability of multiple measures of refractive state using a Nidek ARK-10000 OPD-scan.Method: 150 measurements of refractive state of a test eye were obtained using an OPD-scan. The method of focusing and triggering the instrument was varied for three sets of 50 measurements.Results: The results of this study suggest that the OPD-scan gives reliable and accurate measures of refractive state when taking multiple measurements. Although the means of the various sets of measurements were significantly different, clinically the differences are probably insignificant.
An investigation into diabetic patients’ knowl-edge of diabetes and its ocular complications in the Western Cape
Authors: Clarke-Farr P.C.
Published: October 2016

This paper presents the findings of a study which  evaluated  the  knowledge  of  a  sample of diabetic patients about their disease and its ocular complications. A comprehensive ques-tionnaire  was  provided  to  diabetic  patients in  the  Cape  Town  metropolitan  district  and its  surrounds.  Specifically,  the  questionnaire aimed  to  determine  the  patient’s  knowledge of  diabetes,  their  knowledge  of  the  ocular complications of diabetes, the options for its management and treatment as well as a section considering  other  general  information  relat-ing  to  diabetes  and  its  ocular  complications. Their subject knowledge about diabetes and its ocular complications was relatively limited as only 42% of respondents knew about the exis-tence  of  two  types  of  diabetes. Twenty  nine percent of respondents believed that diabetes would not affect their eyes. Although 76% of the patients felt it very important to measure their blood sugar and 80% rated blood sugar control  as  very  important,  only  37%  of  the respondents  measured  their  blood  sugar  on a  daily  basis. A  particular  concern  was  that although  96%  of  the  respondents  felt  that  it was important to have their eyes checked regu-larly, only 30% of the respondents stated that they had actually had their eyes checked every year. The results of this investigation support the need for diabetic patients to receive better patient education about diabetes and its ocular complications. Furthermore, attention needs to be paid to expanding patient access to diabetic screenings and ocular examinations in order to manage this condition effectively.
A retrospective analysis of heterophoria values in a clinical population aged 18 to 30 years
Authors: Makgaba N.T.
Published: October 2016

Information on heterophoria values in South Africans  is  scanty. The  purpose  of  this  paper therefore, is to present information on the distribution of heterophoria in a clinical popula-tion aged 18 to 30 years, which hitherto is not available. The data presented here was obtained from  the  record  cards  of  475  black  South African  patients  examined  at  the  Optometry clinic, University of Limpopo (Turfloop cam-pus) between 2000 and 2005. The patients were examined by final year students under the supervision  of  qualified  optometrists.  Heterophoria was  measured  for  each  patient  using  the  von Graefe  method.  The  horizontal  heterophoria for distance vision (6 m) ranged from 16 prism diopters (pd) esophoria to 12 pd exophoria with a mean of 0.74 pd exophoria (SD = ± 2.84 pd). For  distance  vision,  esophoria  ranged  from 0.5 to 16 pd with a mean of 3.08 pd (SD = ± 3.09), while exophoria ranged from 0.5 pd to 12 pd with a mean of 2.21 pd (SD = 1.82 pd). For near vision (0.4 m), the horizontal phorias ranged from 17 pd esophoria to 15 pd exopho-ria with a mean of 3.84 pd exophoria (SD = ± 4.80 pd). The near esophorias ranged from 0.5 to 17 pd with a mean 4.88 pd (SD = ± 3.41), while the exophorias ranged from 1.0 to 15 pd with a mean of 6.30 pd (SD = ± 2.58). Vertical heterophoria for distance vision ranged from 5 to 3 pd right hyperphoria with a mean of 0.05 pd right hyperphoria (SD = ± 0.76) whereas at near it ranged from 4 to 6 pd right hyperphoria with a mean of 0.08 pd right hypophoria (SD =  ±  0.96).  The  distributions  of  heterophoria at distance and near were non-normal.  There was  no  significant  gender  variation  in  the horizontal  values  for  distance  vision  and  the vertical  (distance  and  near)  ones.  However, there was a statistically significant gender varia-tion  in  the  near  horizontal  values  (p  >  0.05). There  was  no  significant  variation  in  heterophoria  values  with  age.    The  data  presented here will be useful for comparison with simi-lar data from South Africa or other countries.
A review of the use of Streptozotocin (STZ) in the induction of diabetes in rats and subsequent ocular tissue changes
Authors: Gillan W. D. H. , Eiselen R. J.
Published: October 2016

No abstract available
Transformations of ray transferences of optical systems to augmented Hamiltonian matrices and the problem of the average system
Authors: Cardoso J. R.
Published: October 2016

The first-order optical nature of an optical system (including an eye) is completely characterized by a 55 ×  matrix called the ray transference.  It is known  that the image of a ray transference by the matrix logarithm function is an augmented Hamiltonian matrix.  It turns out that there are other ways of transforming transferences into augmented Hamiltonian matrices.  They include Cayley transforms and modified Cayley transforms.  This paper will describe these transforms with a view to finding the most suitable one for quantitative analyses of eyes and other systems in augmented Hamiltonian spaces.  In particular we look at the calculation of average systems.
Quantitative analysis in Hamiltonian space of the transformed ray transferences of a cornea
Authors: Marhebula S. D.
Published: October 2016

The primary purpose of this paper is to illustrate the quantitative analysis of the linear-optical character of a cornea using transformed ray transferences in a 10-dimensional Hamiltonian linear space. A Pentacam was utilized to obtain 43 successive measurements of  the powers of the anterior and posterior corneal surfaces and the central corneal thicknesses of the right eye of a single subject.  From these measurements 44 ×  ray transferences were calculated (and principal matrix logarithms for all the transferences were determined).  This produced a set of 43 transformed transferences for the cornea which represent 43 points in a 10- dimensional Hamiltonian space.  A 10-component mean and  10 10 ×  variance-covariance matrix were calculated from the transformed transferences.  The mean, and variances and covariances represent, in the 10-space, the average and the spread respectively of the measurements characterising the optical nature of the cornea.  The matrix exponential of the mean gives a value for the mean transference of the cornea; it represents the average cornea.  The analysis described here can be applied to most optical systems including whole eyes and is complete within linear optics.  We believe it to be the first such analysis.
A comparative study of autokeratometric and Scheimpflug keratometric measurements of the anterior corneal surface: results for a single subject
Authors: Mathebula S. , Rubin A.
Published: October 2016

One purpose of the broader study was to determine whether keratometric measurements obtained with an autokeratometer (Nidek ARK-700) would be comparable with those measured using the Oculus Pentacam(model 70700). Ten healthy subjects without ocular abnormality, no previous or current contact lens wear or history of ocular surgery were recruited and at least 43 successive keratometric measurements were obtained for the right eye of each subject using both instruments, namely the autokeratometer and the Pentacam. This paper will concern itself with data from only one of the ten subjects involved, namely Subject 1. The corneal powers were analyzed using multivariate methods for analyzing dioptric power. Scatter plots and meridional profiles of skewness and kurtosis were used to compare the results for the two instruments. Mean dioptric powers in conventional and scientific notation were determined.The results for this subject indicated that there was a statistically significant difference between the autokeratometry and the Pentacam. Although the means  between the two instruments were found to be significantly different at a 95% level of confidence, there was minimal clinical difference between the means of the two instruments. That is, this preliminary investigation suggests that in normal eyes, clinically, keratometric results obtained by means of an autokeratometer and a Pentacam are reasonably similar and can be used interchangeably.
Short-term variation of autorefraction in Diabetic Macular Edema (DME) *
Authors: Sukha A. Y. , Rubin A.
Published: October 2016

Very few studies have investigated autorefraction in diabetic subjects presenting either with diabetic retinopathy (DR) and/ or diabetic macular edema (DME). To the best of our knowledge this is the first study using multivariate methods for investigating short-term autorefraction in a small sample of subjects diagnosedwith DME. Forty consecutive autorefractor measurements were taken over a short interval on each of seven diabetic subjects with varying stages of DME, and the results were compared to a smaller group of four diabetic control subjects without DME (reasons for the differences in sample sizes will be explained later). Measurements were obtained from both the right and left eyes of all subjects.  Subjects in the two groups were similarly matched according to duration of diabetes mellitus (DM), age and glycated hemoglobin (HbA1c) values. Normality of data distribution was mostly achieved with the removal of outliers (where necessary) until profiles of skewness, kurtosis, and standard mean deviation exhibited near-normal distribution. Thereafter, stereo-pair scatter plots with 95% surfaces of constant probability density (distribution ellipsoids) were generated and compared between the experimental and control subjects.The diabetic subjects with DME demonstrated a larger spread of measurements in the eyes with the more severe DME, with the exception of one subject (subject 5). The volumes and orientation of the distribution ellipsoids also differed between the subject’s eyes. Some eyes with severe DME and poor visual acuitydisplayed more stigmatic variation (for example, subjects 2 and 4), while others (subjects 1 and 3) displayed more ortho-antistigmatic variation or near oblique antistigmatic variation (subject 7).  In all experimental subjects, with the exception of subject 5, the eye with the more severe DME had a larger distribution ellipsoidvolume, indicating greater variation in autorefraction and thus it might be surmised that this paper provides some preliminary data to suggest that diabetic subjects with DME display greater short-term variation of refractive behaviour when compared to diabetic subjects without DME. Secondly, in diabetic subjects withDME, eyes with the more severe DME or worse VA also display greater variation of refractive status. However, there seemed to be no distinctive or obvious pattern to the type of variation.In addition, a suitable statistic in terms of a Cubic Root Difference (CRD) was introduced in this study to compare inter-ocular ellipsoidal volumes. This statistic is also useful for comparing variances between eyes, or between means for groups of eyes, and could be used in studies involving anisometropia,  et cetera. Nevertheless, this study suggests that further investigation remains necessary before autorefraction can be used effectively in the early diagnosis, monitoring, and assessment of eyes with diabetic-related complications to the macular regions.
Global and local contributions to corneal surface curvature: a simple model
Authors: Harris W. F.
Published: October 2016

Variations in corneal surface powers reflect variations in the geometry of the cornea.  In particular one can regard corneal surface curvature as a combination of local and global effects.  A simple mathematical model of the cornea is presented which makes use of measurements of the curvature of the anterior and posterior surfaces to decompose the curvature into global and local contributions.  The model gives insight into the source of variations in keratometric measurements, lids and eye turn, perhaps, for global effects and the tear film, perhaps, for local effects.  The model also takes account of the thickness of the cornea.  A numerical example is presented.
Mucormycosis
Authors: Mathebula S. D.
Published: October 2016

The zygomycoses are infections caused by fungi of the class zygomycetes, comprised of the orders Mucorales and Entomophthorales. Fungi ofthis order are causes of mucormycosis, an acute opportunistic infection occurring mostly in immunocompromised individuals, particularly in patients with diabetic ketoacidosis. The purpose of this paper is to present an academic perspective on thepathophysiology, presentation and management of mucormycosis. Possible management strategies are provided.
Colour vision screening among Saudi Arabian children
Authors: Oriowo O. Matthew , Alotaibi Abdullah Z.
Published: October 2016

Purpose: To determine the prevalence of congenital red-green colour vision defects among Saudi Arabian male and female children.Methods: The study involved 1638 elementary and high school participants (838 males, and 800 females), who were randomly selected and screened for red-green colour vision defects using the Ishihara (pseudo-isochromatic plates) test. Inclusion criteria were Snellen VA 20/20 or better and absence of known ocular pathologies.Among the females, 0.75% of the 800 participants showed CVD, with 0.25% and 0.5% demonstratingprotan and deutan defects, respectively.Conclusion: The results show that the prevalence of red-green colour deficiency among the female children from central Saudi Arabia is not significantly different from that of female populations inwestern countries.  The current prevalence among the males is higher than previously reported for central Saudi Arabia, but less than for Caucasian populations.
An assessment of the level of diabetic patients’ knowledge of diabetes mellitus, its complications and management in Durban, South Africa
Authors: Mashige K. P. , Notshweleka A. , Moodley S. , Rahmtoola F. H. , Sayed S. B. , Singh S. , Sardiwalla Z.
Published: October 2016

Epidemiological data shows that Diabetes Mellitus (DM) in South Africa is increasing with changes in lifestyles and ageing of the population. Early diagnosis and management of DM is an important factor for limiting visual and physical complications of the disease. The purpose of this study was to establish the level of knowledge about DM, its ocular complications and management protocol amongst diabetic patients. A questionnaire was provided to a total of 106 diabetic patients attending the Tongaat Community Clinic, the University of KwaZulu Natal Eye Clinic and the Diabetic Awareness day in Chatsworth. All patients were receiving treatment for DM. The questionnaire consisted of questions relating to the patients’ knowledge of the disease, its ocular complications and its management. The respondents were mostly females (65%), aged between 30 to 85 years (mean = 52.45 ± 3.75 years). The majority (96%) of respondents knew about the existence of two main types of DM and 77% reported having Type 2 DM, 18% reported having Type 1 DM, and only 5% did not know the type of DM that they had. Many respondents thought that hereditary factors (78%), and diet and lifestyle modifications (77%), were important risk factors in the development of DM. Glucose levelcontrol (84%) and duration (85%) were thought as important risk factors for its complications. Although many subjects (66.1%) were aware of the visual threat that DM posed, only 42%, 44% and 53% knew that DM could result in diabetic retinopathy, cataracts and glaucoma respectively. Less than half (48.3%) of the respondents had their last eye examination more than a year and a half ago. A significant proportion (60.8%) reported that the threat to vision was reason enough for them to have regular eye examinations. A large proportion (76%) of respondents reported that they had adequate knowledge of management of DM. Many (81%) of the respondents reported routinely controlling their DM through diet,  65% through exercise, 84% through sugar monitoring and 76% through regular medical examinations. The participants in this study had a significant knowledge of DM and its management. However, their knowledge of ocular effects was limited. These results highlight the need for educational programmes aimed at improving the knowledge of the effects of DM on the eyes including the need for regular eye examinations.
The effect of pinholes of different sizes on visual acuity under different refracting states and ambient lighting conditions*
Authors: Abdul N. , Meyer N. , Van Bosch M. , Van Zyl A. , Viljoen M. , Carlson A. S.
Published: October 2016

Purpose: The purpose of this pilot study was to investigate the effect of different size pinholes on visual acuity (VA) at near (0.4 m) while various factors were altered. The alterations made involved accommodation and illumination.Method: Four subjects were selected and their ages ranged from 7 to 14 years. Subjective refractions were performed and then near visual acuities were measured at 0.4 m under two different lighting conditions (460 lux and 1 lux) by adding stigmatic (or spherical) lenses of positive and negative powers in front of pinholes of diameters 1.5 mm and 2 mm.Results: The results showed that there was an improvement in VA in most, however, the size of the pinhole played a minor role. Low illumination did have a drastic effect on our results not only by decreasing the amount of lenses used for near that gave more positive results, but also when the pinhole was placed in front of the subjects. According to Borish, the pinhole does improve VA by a straight forward process of elimination produced by spherical aberrations of the eye. However, this did not seem to be the case in this study under conditions of low illumination.Conclusion: The pinhole effect offers improvement in VA at near by reducing the amount of blupresented to the retina. This study showed that alsubjects had an improvement in VA of at least twolines in high illumination. Pinhole size did not alte the results sufficiently thus suggesting that a pinhole, no matter the size, should increase the VA. However this was not the case when illumination was decreased.
Pseudo-duplication of the optic nerve head
Authors: Moore L. A.
Published: October 2016

A 25-year-old woman presented for a routine eye examination.  She felt that her distance and near vision was good, but experienced severe frontal headaches when reading or using a VDU (50 cm working distance) for prolonged periods.
A review of the use of Streptozotocin (STZ) in the induction of diabetes in rats and subsequent ocular tissue changes
Authors: Sithole H. L.
Published: October 2016

Streptozotocin is widely used in medical research for treating certain cancers of the Islets of Langerhans and to produce an animal model for type 1 diabetes. A study has revealed that when compared to the control group of rats, those injected with STZ exhibited reduced plasma insulin and elevated blood glucose (p < 0.05 in all cases). The study also found that diabetic rats weighed significantly less than control animals (p < 0.05). In relation to ocular tissues, lacrimal glands from diabetic rats were also found to weigh significantly less  (p < 0.05) than those from the control group. However, no significant changes in the weights of lens, cornea, sclera and retina were observed between diabeticand control animals. Several other studies found that STZ-induced diabetes can be treated by plant extracts which control the blood sugar level as well as improving the lipid profile and ocular complications such as retinopathy. Experiments are usuallyperformed on male or female rats of a specific body weight, usually between 250 and 300 g. Diabetes is induced in rats by intraperitonial injections of streptozotocin (60 mg/ kg) in citrate buffer, pH 6.3.Animals that exhibit glucosuria after 24 hours, test-ed by urine test strips are considered diabetic. Plant extracts (6 mg/100g body weight) are orally administered into the stomach of STZ-diabetic rats every third day at a certain consistent time by means of bulbed steel needle for at least a four week period. This is done to determine the efficacy and potency of the plant extracts on diabetes. Histological and transmission electron microscope (TEM) techniques are used to study the changes in the ocular tissues. The dissected ocular tissues should be dehydrated in graded ethyl alcohol series and embedded in Araldite CY212. Ultra thin sections should be contrasted with uranyl acetate and lead citrate for examination by TEM. Streptozotocin induces diabetes in laboratory animal models for scientific studies and breakthroughs in medicine. The use of STZ and plant extracts may prove to be beneficial in the eye health care profession if considered for the studies of hypoglycemic agents that have the potency to prevent the advancement of diabetic retinopathy in diabetic patients.
Demographic, medical and visual aspects of Dia- betic Retinopathy (DR) and Diabetic Macular Edema (DME) in South African diabetic patients*
Authors: Sukha Anusha Y. , Rubin Alan
Published: October 2016

Objective: To investigate some of the demographic, medical, and visual aspects of diabetic retinopathy (DR) and diabetic macula edema (DME) in diabetics attending an urban clinic in Johannesburg, Gauteng.Design: In this cross-sectional study, 202 diabetic patients were recruited. Demographic variables included age, gender, race, age of diagnosis, duration of diabetes mellitus (DM), and social habits. Medical variables included systemic conditions present, blood pressures, body mass indices (BMI), lipid profiles, glycerated haemoglobin (HbA1c), and other biochemical data. Visual variables included distance, pinhole and near visual acuities, contrast visual acuities (CVA), refractive status, colour vision, central visual field evaluation with the Amsler grid, intraocular pressures (IOP), fundus photography and administration of the Impact of Visual Impairment (IVI) questionnaire. All variables were compared between diabetic subjects with and with-out DR and DME in both right and left eyes.Results: Overall prevalence of DR was 22.8% and DME 12.5%. In DR subjects, significant results indicated that Whites were more likely to present with DR (p = 0.002). Subjects with DR had a higher mean duration of DM (p = 0.002) and a higher mean diastolic blood pressure (p = 0.035). Autorefraction suggested that more myopia and less astigmatism might be associated with DR. A higher mean CVA at the 2.5% level in DR was significant in both the right eyes (p = 0.042) and left eyes (p = 0.035). These subjects also reported a higher mean IVI score in the consumer and social interaction domain (p = 0.032). Similarly, DME subjects displayed a higher mean duration of DM (p = 0.042) and a higher mean diastolic blood pressure (p = 0.048). A higher mean CVA was associated at both the 10% level: right eyes (p = 0.021); and left eyes (p = 0.046), and at the 2.5% level: right eyes (p = 0.033) and left eyes (p = 0.045). A higher mean IVI score in leisure and work (p = 0.026), consumer and social interactions (p = 0.01) and emotional re-action to vision loss (p = 0.018) was reported in subjects with DME.Conclusion: This study has identified possible demographic, medical and visual risk factors of DR and DME in South African diabetic patients.
Ray pencils of general divergency
Authors: Harris W. F.
Published: October 2016

That a thin refracting element can have a dioptric power which is asymmetric immediately raises questions at the fundamentals of linear optics.  In optometry the important concept of vergence, in particular, depends on the concept of a pencil of rays which in turn depends on the existence of a focus.  But systems that contain refracting elements of asymmetric power may have no focus at all.  Thus the existence of thin systems with asym-metric power forces one to go back to basics and redevelop a linear optics from scratch that is sufficiently general to be able to accommodate suchsystems.  This paper offers an axiomatic approach to such a generalized linear optics.  The paper makes use of two axioms: (i) a ray in a homogeneous medium is a segment of a straight line, and (ii) at an interface between two homogeneous media a ray refracts according to Snell’s equation.  The familiar paraxial assumption of linear optics is also made.  From the axioms a pencil of rays at a transverse plane T in a homogeneous medium is defined formally (Definition 1) as an equivalence relation with no necessary association with a focus.  At T the reduced inclination of a ray in a pencil is an af-fine function of its transverse position.  If the pencilis centred the function is linear.  The multiplying factor M, called the divergency of the pencil at T, is a real  2 2×  matrix.  Equations are derived for the change of divergency across thin systems and homogeneous gaps.  Although divergency is un-defined at refracting surfaces and focal planes the pencil of rays is defined at every transverse plane ina system (Definition 2).  The eigenstructure gives aprincipal meridional representation of divergency;and divergency can be decomposed into four natural components.  Depending on its divergency a pencil in a homogeneous gap may have exactly one point focus, one line focus, two line foci or no foci.Equations are presented for the position of a focusand of its orientation in the case of a line focus.  All possible cases are examined.  The equations allow matrix step-along procedures for optical systems in general including those with elements that haveasymmetric power.  The negative of the divergencyis the (generalized) vergence of the pencil.
A small-sample survey of dry eye symptoms using the Ocular Surface Disease Index
Authors: Gillan W. D. H.
Published: October 2016

No abstract available
Pursuit eye movements: A review
Authors: Hansraj R.
Published: October 2016

No abstract available
Short-term variation in ocular anterior chamber angle using Scheimpflug photography
Authors: Rubin A.
Published: October 2016

Purpose: To investigate short-term variation of ocular Anterior Chamber Angle (ACA) within and across the different meridians of young, healthy eyes.Method: Scheimpflug photography (via an  Oculus Pentacam) was used to repeatedly measure the anterior segment of the right eyes of three young females, all aged 22 years.  For each individual, ten consecutive maps were determined over a short time period and each map contained information for the chamber angles of different meridians across the eye involved, roughly at 70 intervals.  Each meridian in an eye was thus measured 10 times in total permitting analysis of short-term variation both within and across the meridians concerned.  Parametric and non-parametric statistical methods used to understand short-term variation of ACA included meridional plots of medians andlower and upper quartiles (Q1 and Q3) and various polar plots (of raw observations, of means and 95%confidence regions, and of standard deviations).Results: Over, at least, short periods of time, Scheimpflug photography provided fairly repeatable results for ACA both within and across the meridians of the eyes involved.  However, occasionally outliers increased variability for some meridians.  While short-term variation within meridians was relatively small assuming exclusion of a limitednumber of outliers, variation across the meridians of specific eyes was greater (probably relating to the usual anatomical structure of eyes with ACA in the inferior quadrants being mostly larger than that for the superior quadrants).  Friedman ANOVA confirmed for each of the three eyes concerned thamedian ACA was significantly different across thvarious meridians.Conclusion: Scheimpflug photography allows for comprehensive, non-invasive and rapid measurement of ACA through 3600.  Repeatability of measurements appears satisfactory over the short-term, despite potential limitations relating to this photo-graphic method for measuring ACA.  The holistic and quantitative approach to ACA used here may be useful also in diabetic, neoplastic or other disease of the anterior segment of the eye.  This methodology could provide better understanding of the potential risk for acute or chronic angle-closure glaucoma through more complete evaluation of ACA.  The methods also could be usefully applied to measurement of ACA using techniques such as anterior segment optical coherence tomography or ultrasound biomicroscopy. (S Afr Optom 2010 69(1) 35-47)
Optical lenses and magnification in archery*
Authors: Strydom B. , Ferreira J. T.
Published: October 2016

The use of optical lenses to increase or magnify a target of concern is commonly used in compound bow archery.  The principles and factors that may influence the use of these lenses may, however, not be fully understood by archers.  Two types of lens systems, the one-lens system and the two-lens system, as described by the authors, may be used. Different factors such as the draw length of the archer,the ametropic condition of the archer, depth of field, depth of focus, age, accommodation, the power of F1 and F2 (see Figures 1 and 2 in the paper) and the distance the lens is placed from the archer may influence the results of the lens used by the archer. (S Afr Optom 2010 69(1) 29-34)
The short-term effects of PMMA contact lens wear on keratometric behaviour: results for a single keratoconic cornea*
Authors: Chetty E. , Gillan W. D. H.
Published: October 2016

Keratometric behaviour is a multifaceted issue that many researchers have investigated for years. Many internal and external influences can have an effect on the cornea’s keratometric behaviour. This investigation forms a small part of a larger study that aims at determining the effects that rigid contact lenses might have on keratometric behaviour. This pilot study examined the keratometric behaviour of a single, mildly keratoconic cornea that was fitted with a polymethyl methacrylate (PMMA) contact lens. Sixty successive auto-keratometric measurements were taken immediately before and immediately after three hours of contact lens wear. The data obtained was transformed to dioptric power matrices and were analysed using multivariate statistical methods. This study showed that, at least in one keratoconic cornea, there appeared to be a statistically significant change in corneal curvature under the influence of a PMMA contact lens. The contact lens had also appeared to decrease variation in corneal curvature. There was no control study done on this eye therefore the effects of diurnal variation, if any, could not be established. (S Afr Optom 2010 69(2) 69-76)
Optometric practices and practitioners in KwaZulu-Natal, South Africa*
Authors: Mashige K. P. , Naidoo K. S.
Published: October 2016

This paper presents findings of a survey of optometric practices and practitioners in the KwaZulu-Natal (KZN) province. Questions on demographics of practitioners, equipment, clinical practice andbusiness profile were included in the questionnaire. Also, issues that have the potential to impact on optometric practices were contained in the questionnaire and these include medical aid, advertising, continuous professional development (CPD) and emigration. Of the 117 completed questionnaires, 55% were from females and 45% were from male practitioners. The respondents included 55% Indians, 27% Whites, 17% Blacks and 1% Coloureds. The majority of practices were located in urban areas (90%) and rural areas (10%), and were mostly independent (67%) and franchises (33%). Only a minority of the practices had major diagnostic equipment such as visual field analysers (33%) and corneal topographers (7%). A significant proportion of the practitioners reported not routinely performing non-contact tonometry (45%) and slit lamp examination (41%) respectively. The majority (95%) rated patient’s needs as a very important factor in their decision to prescribe an optical device. A significant proportion (38%) of the practices had annual patient bases of above 33 000, with 35% having an average of 51-100 new patients per month. A few (5%) practices reported gross monthly turnovers of above R400 000, and 27% reported turnovers of less than R60 000. Many (89%) derived 41% and above of their total revenue from spectacle lens sales and 11% derived 41% and above from contact lens sales. The majority (92%) of practices were contracted to over 60% of the medical aid schemes. Many (68%) reported that they were not negatively affected by medical aid fraud committed by their colleagues, however, a significant proportion (32%) reported the converse. More than half (54%) of the practitioners reported that they used the print media
Refractive error in school children in Agona Swedru, Ghana
Authors: Ovenseri-Ogbomo G. O. , Assien R.
Published: October 2016

Uncorrected refractive errors remains a public health problem among different population groups. Among schoolchildren, uncorrected refractive errors have a considerable impact on learning andacademic achievement especially in underserved and under-resourced communities. A school based cross-sectional study was carriedout to estimate the prevalence and distribution of refractive error among schoolchildren in the Agona Swedru municipality of Central Region of Ghana. 637 schoolchildren aged 11-18 years old were randomly selected for the study. Non-cycloplegic refraction was performed on each child who failed the reading test. Hyperopia was defined as spherical power of ≥ + 0.75 D, myopia as ≤ – 0.50 D and astigmatism as a cylindrical power of ≤ – 0.50 D. Of the children examined, only 13.3% had previously had an eye examination.Visual impairment (VA of 6/12 or worse in the better eye) was present in 4.5% of the children examined. Of those who failed the reading test, 85.9% had refractive error. The prevalence of hyperopia, myopia and astigmatism was 5.0%, 1.7% and 6.6% respectively. The study concludes that uncorrected refractive error is a common cause of visual impairment among schoolchildren in the municipality. A low uptake of eye care is also noted in the study. The study therefore recommends that the education authority in collaboration with the District Health Directorate institute appropriate measures to ensure compulsory eye examination for schoolchildren in the Agona Swedru district. (S Afr Optom 2010 69(2) 86-92)
Optical axes of catadioptric systems including visual, Purkinje and other nonvisual systems of a heterocentric astigmatic eye
Authors: Harris W. F.
Published: October 2016

For a dioptric system with elements which may be heterocentric and astigmatic an optical axis has been defined to be a straight line along which a ray both enters and emerges from the system.  Previous work shows that the dioptric system may or may not have an optical axis and that, if it does have one, then that optical axis may or may not be unique.  Formulae were derived for the locations of any optical axes.  The purpose of this paper is to extend those results to allow for reflecting surfaces in the system in addition to refracting elements.  Thus the paper locates any optical axes in catadioptric systems (including dioptric systems as a special case).  The reflecting surfaces may be astigmatic and decentred or tilted.  The theory is illustrated by means of numerical examples.  The locations of the optical axes are calculated for seven optical systems associated with a particular heterocentric astigmatic model eye.  The optical systems are the visual system, the four Purkinje systems and two other nonvisual systems of the eye.  The Purkinje systems each have an infinity of optical axes whereas the other nonvisual systems, and the visual system, each have a unique optical axis. (S Afr Optom 2010 69(3) 152-160)
Generalized magnification in visual optics. Part 1: Magnification as linear transformation
Authors: Harris W. F.
Published: October 2016

In Gaussian optics magnification is a scalar; the interpretation is obvious.  In linear optics, the simplest optics of astigmatic systems, the generalization is a  2 2×  real matrix and, in general, is much harder to interpret.  This generalized magnification may imply magnification in the familiar sense that differs from one meridian to another, shear distortion, rotation, reflection, inversion, magnification in the familiar sense or combinations of these effects.  The purpose of this paper is to illustrate generalized magnification and to provide a comprehensive interpretation.  Because the treatment is abstract it can be applied to blur and size magnification and to any magnification that can be represented by a  2 X 2  matrix. (S Afr Optom 2010 69(3) 109-122)
Tear secretion and tear film stability in Nigerians with non-insulin dependent diabetes mellitus
Authors: Idu F. K. , Orge E.
Published: October 2016

It has been reported that many diabetic patients complain of dry eye symptoms. Thus this study was aimed at investigating tear secretion and tear film stability in patients with non-insulin dependent diabetes mellitus (NIDDM). Eighty (80) subjects within the age range of 50-60 years with mean age of 55 ± 3.42 years were recruited for this study.They comprised of 40 NIDDM patients (19 males and 21 females) and 40 age and gender matched controls (18 males and 22 females) without diabetes. Schirmer test and invasive tear break up time(TBUT) were used to determine tear secretion and tear film stability respectively. Results showed an apparent reduction in both total and basal tear secretions for the NIDDM patients compared with that for control subjects. However this reduction was not statistically significant with the unpaired t-test. (p > 0.05). Unpaired t-test revealed a statistically significant reduction in TBUT of the NID-DM group compared with control subjects. Cor-relation analysis revealed a negative correlation between fasting blood sugar (FBS) levels and both basal and total tear secretions. (r = −0.51, p < 0.05) and (r = −0.54 p < 0.05) respectively. There was also a negative correlation between FBS and TBUT (r = −0.34 p = 0.03). The student t-test showed no influence of gender on both tear secretions and TBUT for NIDDM patients and controls. This study shows that both tear secretion and tear film stability are affected by NIDDM, and concurs with the findings that diabetic patients often complain of dry eye symptoms. (S Afr Optom 2010 69(3) 140-145)
Eye health promotion in the South African primary health care system*
Authors: Sithole H. L. , Oduntan O. A.
Published: October 2016

Objective: There is currently very little or no research being done in South Africa on eye health promotion. Also, there is no evidence of any existing eye health promotion policy in the South African primary health care system. The purpose of this paper therefore is to highlight the lack of an integrated eye health promotion policy in the South African primary health care system.Approach: A literature review of research databases was conducted to identify research done in the previous years pertinent to eye health promotion in South Africa. Also, documents were requested from the South African National Department of Health to ascertain claims of any existing guidelines on eye care. It was found that these documents included the national guidelines on prevention of blindness, refractive error screening for persons 60 years and older, cataract surgery in South Africa, management and control of eye conditions at primary level.Although there is currently no integrated eye health promotion policy in South Africa, the fragmented national guidelines represent the existing policies on eye health promotion.  The custodians of these policies are the eye care coordinators located in each of the nine provinces.Conclusion: Although there are eye care coordinators in each province, there is no evidence of any eye health promotion activities being done in those provinces. Also, only one province out of nine has dedicated health promotion personnel that are not only focusing on eye health matters. This greatly compromises the initiatives of eliminating avoidable blindness. It is therefore recommended that an integrated eye health promotion model be developed so that it may form part of the South African primary health care system. (S Afr Optom 201069(4) 200-206)
Graphical construction of cardinal points from the transference
Authors: Harris W. F.
Published: October 2016

Usually nodal, principal and focal points are defined independently and thought of as distinct structures with no simple relationship among them.  By adopting a holistic approach, in which these threetypes of cardinal points are treated as particular cases of a larger class of special points, this paper develops a method of constructing the locations of the cardinal points of a system graphically directly from the transference.  The method provides a useful way of visualising the relationship of the locations of the cardinal points and of how they are affected by changes in the system or when a second optical system is placed in front of the first.  Thepaper illustrates the graphical procedure by apply-ing it in several situations of interest in optometryand ophthalmology, including the effect of a contact lens or refractive surgery on a reduced eye and the effect of accommodation, a spectacle lens and an afocal telescope on the Gullstrand-Emsleyschematic eye. (S Afr Optom 2011 70(1) 3-13)