bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of optical defocus on colour perception
Authors: Sehlapelo R. R. , Oduntan A. O.
Published: October 2016

Daily experience shows that colour  of a very distant object cannot be accurately determined.  It is assumed that visual acuity (VA) loss is one of the factors at play in this case.  The effects of reduced VA as a result of refractive error or optical defocus on colour vision have not been examined.  Such study willdictate the need or otherwise for optical correction before assessment of colour vision.  The purpose of this study therefore, was to investigate the effects of optical defocus on colour vision in individuals with normal colour vision.  Twenty nine young adult subjects (11 male and 18 females) were included in this study. Their ages ranged from 11 to 29 years with a mean of 22.1 ± 3.4 years.  All subjects had VA of 6/6 or better and normal colour vision.  The colour vision was evaluated with the Farnsworth panel D-15 (desaturated). Each subject was optically defocused to VA of 6/24, 6/60 and 1/60(6/360) at 6 meters respectively and colour vision was assessed at each reduced VA.  At VA of 6/24, colour vision was not affected in all subjects. When the VA was reduced to 6/60, however, 15 (51%) of the subjects failed the colour vision test. When the VA was further reduced to 1/60 by optical defocus, 24 (83%) of the subjects failed the colour vision test.  It was concluded that optical defocus and reduced VA can adversely affect colour vision test findings. While VA reduction to 6/24 may not affect the colour vision results, VA of 6/60 can.  It is therefore, recommended that in clinical colour vision  testing and colour vision screening, VA should first be assessed andcompensated, especially if uncorrected VA is 6/24 or worse.
From the Editor’s Desk
Authors: Office Editorial
Published: October 2016

No abstract available
Perceptions, expectations, apprehensions and realities of graduating South African optometry students (PEAR study, 2006)
Authors: Oduntan A. O. , Louw A. , Moodley V. R. , Richter M. , Von Poser P.
Published: October 2016

The objective of this study was to establish the perceptions, expectations, apprehensions and realities of South Africa optometry students completing their undergraduate studies in 2006. Copies of a questionnaire containing relevant information were distributed to all graduating students at the four Universities offering Optometry. The responses were coded and analyzed. The respondents (N=143), representing 77% of the graduating students included 27.3% males and 72.7% females, aged 20 to 37 years (mean = 23.34 ± 2.75). About a third (32.9%) of the respondents considered opening their own practice as the best way of entering into practice. Also, this mode of practice was considered as providing the greatest fulfilment for their personal (60.8%) and professional (53.8%) goals as well as offering long  term financial security (43.7%). Many (56.6%) have secured employment before graduation. Upon graduation, 43.4% would like to join a franchise.  Many (79.7%) felt that Government was not offering sufficient opportunities for optometrists. The majority, (70.6%) felt that the South African optometry profession is fastly becoming saturated and this was of great concern to many (31.5%). About half, (50.3%) have plans to go overseas to practice and the most common destinations were the UK (36.1%) and Australia (15%).  The mean minimum monthly salary expected as new graduates was between R9 500 and R11 500 in the public and private sectors respectively. On a response scale, the future of optometry in South Africa was scored as 6.59 ± 1.92. Findings in this study may be useful to all stake holders in optometric education in South Africa, as they may reflect the future of the optometry profession in the country.
Night vision of the post-LASIK myope
Authors: Hansraj R.
Published: October 2016

Purpose: Poor night vision has been reported as one of the side-effects of LASIK,  however, this area has not been widely studied.  This study therefore set out to assess and quantify the visual status of the post-LASIK patient in dim illumination as an indication of visual performance at night.  This was achieved by assessing the night vision threshold, glare vision threshold and glare recovery time.Setting: The study was carried out in Durban, Kwazulu-Natal in South Africa.Method: This study used the Night Sight Meter for assessment of the night vision thresholds, glare vision thresholds and glare  recovery times of individuals who had had LASIK at least one year before commencement of the study.  The inclusion criteria were post-surgical interval following LASIK of at least one year and willingness to participate in the study.  The exclusion criteria included previous ocular surgery other than LASIK, current ocular disease and any systemic illnesses.   One hundred subjects were selected from participating ophthalmologists’ records, using convenience sampling, at different post-operative periods that ranged from 12 to 57 months.  Other refractive findings taken included post-LASIK visual acuity measured using the Snellen Visual Acuity chart and post-LASIK refractive error, measured with the standard subjective refraction tests which included duochrome, Jackson crossed-cylinder and Humphrey’s Immediate Contrast test, which are used for comparison in this study.Results: Post-operatively, the majority of the eyes (89.2%) were classified as having ‘poor’ night vision thresholds.  A similar trend was observed in the case of the glare vision thresholds as 84.7% of the eyes fell into the classification of below average.  The degree of pre-operative myopia appears to have an effect on the post-LASIK night vision and glare  thresholds.  Only glare recovery  time was not affected as 51.2% of the subjects displayed good recovery times.Conclusion: This study suggests that the post-LASIK myope has difficulty with night vision due to poornight vision and glare vision thresholds which are linked to the higher aberrations and intraocular scatterresulting from LASIK.   As macular integrity is not affected in the LASIK patient, the glare recovery timeappears to be within normal limits.
A look at important issues regarding safe orthokeratology
Authors: Chetty E. , Jackson S. , Mitton C. , Phillips T. K
Published: October 2016

No abstract available
A review of fixation disparity
Authors: Chetty E. , Jackson S. , Mitton C. , Phillips T. K.
Published: October 2016

No abstract available
The metric geometric mean transference and the problem of the average eye
Authors: Harris W. F.
Published: October 2016

An average refractive error is readily obtained as an arithmetic average of refractive errors.  But how does one characterize the first-order optical character of an average eye?  Solutions have been offered including via the exponential-mean-log transference.  The exponential-mean-log transference ap-pears to work well in practice but there is the niggling problem that the method does not work with all optical systems.  Ideally one would like to be able to calculate an average for eyes in exactly the same way for all optical systems. This paper examines the potential of a relatively newly described mean, the metric geometric mean of positive definite (and, therefore, symmetric) matrices.  We extend the definition of the metric geometric mean to matrices that are not symmetric and then apply it to ray transferences of optical systems.  The metric geometric mean of two transferences is shown to satisfy the requirement that symplecticity be pre-served.  Numerical examples show that the mean seems to give a reasonable average for two eyes.  Unfortunately, however, what seem reasonable generalizations to the mean of more than two eyes turn out not to be satisfactory in general.  These generalizations do work well for thin systems.  One concludes that, unless other generalizations can be found, the metric geometric mean suffers from more disadvantages than the exponential-mean-logarithm and has no advantages over it.
The ray transference of a reversed optical system
Authors: Harris W. F.
Published: October 2016

The optical character of an optical system is changed if the system is reversed.  This is as true of eyes as it is of telescopes.  In vision light traverses the eye from cornea to retina; in ophthalmoscopy the practitioner views the retina via light traversing the eye in the reverse direction.  The purpose of this paper is to determine the relationship of the optical character of the reversed system to that of the system itself. The result is in terms of the ray transference of the system.  Since the ray transference gives a complete characterization of the first-order optics of a system the analysis is complete in this sense as well.  Explicit expressions are also presented for the effect of reversal on the six fundamental first-order optical properties of the system.
Foci in ray pencils of general divergency
Authors: Harris W. F. , Van Gool R. D.
Published: October 2016

In generalized optical systems, that is, in systems which may contain thin refracting elements of asymmetric dioptric power, pencils of rays may exhibit phenomena that cannot occur in conventional optical systems.  In conventional optical systems astigmatic pencils have two principal meridians that are necessarily orthogonal; in generalized systems the principal meridians can be at any angle.  In fact in generalized systems a pencil may have only one principal meridian or even none at all.  In contrast to the line foci in the conventional interval of Sturm line foci in generalized systems may be at any angle and there may be only one line focus or no line foci.  A conventional cylindrical pencil has a single line focus at a finite distance but it can be regarded as having a second line focus at infinity.  Only in generalized systems is a single line focus possible without a second at infinity or anywhere else.  The purpose of this paper is to illustrate the types of pencils possible in generalized systems.  Particular attention is paid to the effect of including an antisymmetric component in the divergency of the pencil.
A correlational study of systemic blood pressure and intraocular pressure in a young South African adult population*
Authors: Sithole H. L. , Arbee T. , Nxumalo N. , Tshatsha N. D. , Perumal K. , Ali Z Mohamed , Souza T.
Published: October 2016

Increased blood pressure (BP) and raised intraocular pressure (IOP) are probably both common oc-currences among the South African population. If left untreated both conditions have detrimentalcomplications. Previous cross-sectional studies suggested BP was positively related to IOP. This study therefore sets out to determine in a young South African adult population the correlation between systemic BP and IOP.  Systemic BP was measured using an electronic sphygmomanometer and IOP using a Goldman applanation tonometer. For all subjects, two averages were obtained fromthree measurements each of BP and IOP. Other clinical procedures such as uncompensated visual acuity (VA), pinhole and direct ophthalmoscopy were done to exclude underlying factors possiblyaffecting either BP or IOP before the commencement of the investigation. Two hundred (N = 200)subjects were included in the study and their ages ranged from 18 to 30 years with a mean of 21 ± 3.9 years. The correlation coefficients between average IOP and average systolic or diastolic BP respectively were 0.67 and 0.55. These weak positivecorrelations suggested that with an increase in BP there is a corresponding increase in IOP. Also, similar correlation between IOP and BP was found toexist amongst both males and females with systolic BP having a greater effect. This study validates theimportance of evaluating either systemic BP or IOP amongst all patients seen by primary eye-care practitioners, and that such evaluations should form part of daily routine patient examination.
Symplecticity and relationships among the fundamental properties in linear optics
Authors: Harris W. F.
Published: October 2016

Because of symplecticity the four   fundamental first-order optical properties of an optical system are not independent.  Relationships among them reduce the number of degrees of freedom of a system’s   transference from 16 to 10.  There are many such relationships, they are not easy to remember, they take many forms and they are often needed in derivations.  The purpose of this paper is to provide in one place a comprehensive collection of those that have proved useful in linear optics generally and in the context of the eye particularly.  The paper also offers aids to memorizing some of the results, derives most of them and along the way introducesthe basic notions underlying symplecticity.  The relationship to another important class of matrices, the Hamiltonian matrices, is discussed together with their potential role in statistical analysis of the eye.  Augmented symplectic matrices are also defined and their relationship to augmented Hamiltonian matrices described.  An appendix gives numerical examples of symplectic and Hamiltonian matrices and shows how they may be recognized and constructed.  (S Afr Optom 2010 69(1) 3-13)
Optometric education at Westville: past, present and future
Authors: Mashige K. P.
Published: October 2016

This article presents historical information, current activities and future plans with regards to optometric education at the Department of Optometry, Westville campus of the University of Kwa-Zulu-Natal (UKZN) in Durban. The Department, established in 1979 under the political dispensation of apartheid was intended to cater to the needs of Indian students but now admits students of all races. Also, it has been developing in every aspect of optometric education, staffing and facilities. The undergraduate optometric curriculum at the Department has expanded tremendously over the years and there are now master and doctoral programmes. The number of full-time academic staff has increased from four in 1980 to eleven in 2009. The undergraduate student enrolment has increased from twelve in 1980 to one hundred and sixty in 2009. Research activities and publication output have increased over the years. Community engagement activities have been expanded to meet the needs of the community. Also, physical and training facilities have improved over the years to meet the increasing number of students. The content of this article will be of interest to alumni, current and future students and staff of the Department as well as other stakeholders in the optometric profession and education.(S Afr Optom 2010 69(1) 14-20)
Tear biochemistry: a review
Authors: Gillan W. D. H.
Published: October 2016

no abstract available
Special rays and structures in general optical systems: generalized magnifications associated with the fundamental properties
Authors: Harris W. F.
Published: October 2016

In aprevious study special rays and structures, including nodal, principal and focal rays and structures, were defined in terms of generalized magnification of reduced inclination of rays across thesystem.  The mathematical structure of the transference, however, suggests that there are another three possible approaches.  These involve generalized magnification of transverse position of rays across the system and two cross-magnifications, one of reduced inclination to transverse position and the other of transverse position to reduced inclination. The purpose of this paper is to develop these otherapproaches.  Nodal, principal and focal rays and structures, and, indeed, all special rays and structures, are defined in each of these approaches.  Equations relating the four types of generalized magnification are derived.  The approaches described here may have application in contexts where transverse position is of interest.  In an appendix the generalized magnifications are calculated for nodal rays across a particular model eye. (S Afr Optom 2010 69(2) 51-57)
Visual factors and dyslexia: A research review
Authors: Wajuihian S. O. , Naidoo K. S.
Published: October 2016

Eye care professionals have long been involved with vision and learning, and receive referrals from teachers, psychologists and other professionals who seek advice about whether vision problems may contribute to, or be responsible for, poor academic performance.  This is particularly the case when dealing with the relationship between vision and dyslexia, which has been a subject of controversy in optometric, ophthalmologic, educational and psychological literature. Ophthalmologists and optometrists in particular, hold different views on the association of dyslexia and vision, and there has been much debate regarding any causal relationship between them.  The results of studies that investigated the vision functions in dyslexic populations remain inconclusive.  This review is intended to provide an overview of studies to date and makes recommendation to guide future research.  (S AfrOptom 2010 69(2) 58-68)
Night vision and glare vision thresholds and recovery time in myopic and hyperopic eyes
Authors: Mashige K. P.
Published: October 2016

The purpose of this study was to compare night vision and glare vision thresholds and recovery times in myopic and hyperopic eyes. Using a Night Sight Meter, these three parameters were measured in 44 myopic and 44 hyperopic eyes of Black male subjects age-matched 20.8 years ± 1.67 and 21.6 years ± 1.05 old respectively and compared. Thresholds were measured first by assessing the eye’s ability to see under conditions of low illumination and in the presence of a glare source. Glare recovery time was determined by measuring the minimum time neededto adjust to low levels of light illumination after exposure to a glare stimulus. Descriptive, two-sample t-test and Pearson correlation statistics were used to analyze and compare the sets of data from the two groups. The mean refractive error in the myopic eyes was –2.15 D ± 1.41 (range = –0.50 D to –4.50 D) and 1.76 D ± 1.22 (range = 0.50 D to 4.00 D) in the hyperopic group. The mean night vision thresholds for the myopic eyes was 32 cd/m2 ± 4.69 (range = 23 cd/m2 to 42 cd/m2) and 28.97 cd/m2 ± 4.90 (range = 18 cd/m2 to 37 cd/m2) for hyperopic eyes. The difference between the mean night vision thresholds of the myopic and hyperopic eyes wasstatistically significant (p < 0.05). For glare vision threshold, the mean for myopic eyes was 64 cd/m2 ± 5.81 (range = 53 cd/m2 to 78 cd/m2), while the mean for hyperopic eyes was 44.84 cd/m2 ± 5.69 (range = 32 cd/m2 to 59 cd/m2). Also, the difference between the mean glare vision thresholds of the myopic and hyperopic eyes was statistically significant (p < 0.05). The recovery times ranged from 0.45 s to 3.10 s for the myopic eyes and 0.30 s to 2.25 s for the hyperopic eyes. The mean glare recovery time for the myopic eyes (mean = 1.41 s ± 0.77) was significantly longer (p < 0.05) than the times for hyperopic eyes (mean = 1.04 s ± 0.65). There was a significant positive correlation between recovery times and the magnitude of myopia (r = 0.93, p < 0.05) while the relationship between recovery times and the magnitude of hyperopia was significantly negatively correlated (r = –0.76,  p < 0.05). These findings suggest that myopic persons would have more difficulty seeing under conditions of low illumination and in the presence of glare than hyperopic eyes. This could probably be due to aberrations resulting from larger pupils in the myopic eyes. (S Afr Optom 2010 69(3) 132-139)
Review of photokeratitis: Corneal response to ultraviolet radiation (UVR) exposure*
Authors: Moore L A. , Hussey M. , Ferreira J. T. , Wu B.
Published: October 2016

The development of photokeratitis in response to natural solar ultraviolet radiation (UVR) is prevalent in individuals participating in outdoor recreational activities in environments with high reflective surfaces, such as beach activities, water sports and snow skiing. Eye care practitioners (ECPs) are frequently encouraged by manufacturers and researchers to recommend UVR-blocking eyewear in the form of sunglasses and contact lenses. However, little is known about the precise nature of the corneal tissue response in the development of photokeratitis. This paper reviews the mechanisms responsible for the development of photokeratitis. Clinical signs and symptoms of photokeratitis, UVR corneal threshold and action spectra, corneal cellular changes and ocular protection from corneal UVR exposure are discussed. The content of this article will be useful to ECPs in making appropriate recommendations when prescribing UVR-protec-tive eyewear. (S Afr Optom 2010 69(3) 123-131)
Awareness of the phototoxic effects of sunlight among South African university students
Authors: Oduntan O. A. , Clarke-Farr P. , Hansraj R. , Carlson A.
Published: October 2016

Due tothe depletion of the atmospheric ozone, there is currently a great concern for the phototoxic effects of sunlight on humans worldwide. The purpose of this study was to evaluate the awareness of the phototoxic effects of sunlight among a sample of South African university students.  A questionnaire on awareness of the adverse effects of excessive exposure to sunlight was completed by the participants and findings were analyzed. Ages of the participants (n=1832) ranged from 17 to 55 years (mean = 21.03 ± 3.44) and there were 43.7% males and 56.3% females.  Many, (73.9%) agreedthat excessive exposure to the sun is harmful to health, but only 56.9% could adequately explain how it is harmful to health.  Many, (68.2%) agreed that fair-skinned individuals are more likely to be affected by the sun than dark-skinned ones.  Only 52% reported that childhood exposure to sunlight is more dangerous than adulthood exposure. A few (32.9%) agreed that short term intensive exposure was more dangerous than chronic regular moderate exposures.  Although 72.3% had heard about ultraviolet (UV) radiation, only 47.1% had heard of cataracts and fewer (25.7%) agreed that cataracts can be caused by UVR exposure.  A few (28.7%) had heard of macular degeneration, but only 17.6% agreed that it can be caused by UVR.  Although awareness was good in certain aspects, it was poor in others; suggesting the need for an awareness campaign among South Africans. It is recommended that the awareness campaign should include avoidance of excessive exposure and the use of appropriate protective devices. (S Afr Optom 2010 69(3) 146-151)
The short-term effects of PMMA and RGP contact lens wear on keratometric behaviour: a pilot study*
Authors: Chetty E. , Gillan W. D. H.
Published: October 2016

This article represents the preliminary findings of a larger study that included 24 subjects that were equally divided into three groups, namely, the PMMA (polymethyl methacrylate) group, the RGP(rigid gas permeable) group and the control group. The aim of this study was to establish the short term effects (if any) of PMMA and RGP contact lens wear on keratometric behaviour. A controlsubject was also included in the study to establish a reference fornormal diurnal changes in keratometric behaviour. Fifty successive auto-keratometric measurements were taken before and immediately after three hours of rigid contact lens wear for the first subject in the PMMA group and the first subject in the RGP group (experimental samples). Fifty successive auto-keratometric measurements were also taken on the first subject of the control group before and immediately after three hours of no lens wear (control sample). Data collected were analysed using multivariate statistical methods that in the past have been used infrequently in this area of study. This investigation revealed that, at least in these two randomly selected subjects, rigid contact lens wear appears to  influence keratometric behaviour (PMMA contact lenses more so than RGP contact lenses). (S Afr Optom 2010 69(4) 173-181)
Assessment of the Medmont C100 test for colour vision screening of male Saudi Arabians
Authors: Alotaibi Abdullah Z. , Ikpotokin Emmanuel A. , Oriowo O. Matthew
Published: October 2016

Purpose: To assess the Medmont C100 test as a colour vision screening tool. Methods: One hundred and seventeen young male adults were screened with the Medmont C100, Ishihara plates, and the screening mode of the Oculus Anomaloscope tests. All subjects were tested under constant room illumination, namely that of a day light fluorescent lamp at 200 lux. Inclusion criteria were visual acuities (VA) of 20/20 or better with or without correction and absence of known ocular pathologies.Aided and unaided visual acuities were measured with the Snellen VA chart. Results: Five out of the117 subjects, were found to have red-green colour vision deficiency (CVD) with Ishihara and anomaloscope tests indicating a 4.7% CVD prevalence, while the Medmont C100 test yielded 33 cases of red-green deficiency indicating CVD prevalence of 28%.  With the Ishihara test, all five subjects were identified as deutans, while the anomaloscope revealed three as deutans and two as protans, and the Medmont C100 test identified all 33 cases as protans. Conclusion:  The Medmont C100 test yielded significantly higher prevalence of protan CVD compared with the Ishihara platesand Anomaloscope tests. These findings suggest that caution should be taken when using Medmont C100 test for colour vision screening as it tends togive more false positive results with bias for protans.  (S Afr Optom 2011 70(1) 14-20)
The KwaZulu-Natal Child Eye Care Programme: Delivering refractive error services to primary school learners
Authors: Mahraj Y. I. , Naidoo K. S. , Dabideen R. , Ramson P.
Published: October 2016

Globally, over 300 million people are estimated to be visually impaired. Uncorrected refractive error is the primary cause of almost half of all visual impairment, resulting in the global economy losing $269 billion in productivity annually. There is a definitive level of urgency in the treatment of refractive error in children as uncorrected refractive error results in the failure of normal visual maturation, termed amblyopia, which cannot be corrected in adult life. In South Africa, the lack of appropriatechild eye care strategies has posed a serious problem to the visual health of children. In 2006, the International Centre for Eye Care Education (ICEE) conducted a situational analysis of child eye care services in the province of KwaZulu-Natal (KZN). The findings of this analysis indicated a dire need for comprehensive services in the province. Stakeholders (the KwaZulu-Natal Department of Healthand the KwaZulu-Natal Department of Education) were advised on the value of a short-term strategy as the underpinning of a long-term sustainable approach. This resulted in the formation of a trialliance to implement the KZN Child Eye Care Programme. Eighty (80) individuals who were previously volunteers for the KZN Department of Health were trained in vision screening. These vi-sion screeners screened 239 606 primary school children from February 2007 to May 2008. Seven percent (15 944) of the children failed the vision screening and were referred for optometric assessments. Of the 15 944 children that failed the vision screening, 10 707 children were examined by optometrists and 1083 were found to have a refractive error and were therefore supplied with spectacles. The study indicates that a short-term programme to address a backlog of services can reach many underserved children. This programme identified many challenges of implementing a vision screening programme such as poor uptake of refractive services by learners in the absence of an appropriate referral system and high attrition of trained vision screeners. (S Afr Optom 2011 70(2) 61-68)
Dyslexia: An overview
Authors: Wajuihian S. O. , Naidoo K. S.
Published: October 2016

Dyslexia is a neuro-developmental disorder characterized by difficulties in learning to read despite conventional instruction, adequate intelligence and a balanced sociocultural background.  Dyslexia is the most common type of learning disorder.  Reading difficulties affect a child’s academic achievement.  As primary eye care practitioners, optometrists have a role in attending to patients who may present with symptoms indicative of dyslexia, therefore an understanding of dyslexia will be beneficial to the optometrist.  This paper presents an overview of dyslexia and discusses its prevalence, aetiology, classifications, neural pathways involved in reading, theories, neuro-imaging techniques and management options. The role of optometry in the multidisciplinary management of dyslexia is discussed.  (S Afr Optom 2011 70(2) 89-98)
Induced astigmatism after cataract surgery - a retrospective analysis of cases from the University of Port Harcourt Teaching Hospital, Nigeria
Authors: Adio A. O. , Aruoto N.
Published: October 2016

Visual rehabilitation after cataract surgery may often be disappointing due to induction of corneal astigmatism following issues in realigning, point to point, the corneal wound margin in the process of surgery despite biometry and use of the appropriateintraocular lens. The purpose of this study is to determine the amount of surgically induced astigmatism after sutured cataract extraction-extracapsular cataract extraction (ECCE) and intracapsular cataract extraction (ICCE) and intraocular lens (IOL)implantation in the University of Port Harcourt Teaching Hospital, Port Harcourt, Nigeria. Folders of all cataract patients operated on in the eye theatre of the aforenamed tertiary facility between2002 and 2006 were considered.  Relevant patient details and intraoperative and postoperative management were examined and reported upon. One hundred and fourteen eyes (114) of one hundred patients who had cataract surgeries done within the five-year period of this study were examined. ECCE + IOL implantation were examined in the period under review. The post-operative refraction objectively and subjectively was retrieved from the records of each patient. The post-operative cylinderpower (total astigmatism) was recorded.Of 114 eyes, only 83 eyes (72.8%) had refraction results postoperatively due to loss of fol-low-up. The total number with astigmatism was 57(68.7%). Forty-two had against-the-rule (73.7%), twelve (21.1%) with-the-rule, while five (0.09%) were oblique. The mean post-operative astigmatism was 1.85 D. The surgically induced corneal astigmatism was highest with ECCE with PCIOL. Astigmatism less than 2 D was highest in this group (ECCE with IOL) while ICCE with ACIOL had the highest number with astigmatism in the range between 2 D and 4 D. The total astigmatism which was mainly with-the-rule (vertical plus cylinder) did not seem to impair severely the post-operative visual acuity of the patients.In conclusion, surgically induced astigmatism affected almost 75% of the patients operated and refracted within the period under review. This can be reduced with better operating skills using small incision suture-less techniques. Existing postoperative astigmatism can be reduced by suture cutting at specific periods particularly if there is follow-up at the critical periods. (S Afr Optom 2011 70(2)75-80)
An introductory review of nuclear magnetic resonance spectroscopy: analysing meibomian secretions
Authors: Gillan W. D. H.
Published: October 2016

No abstract available
Utilization of eye care services by elderly persons in the northern Ethekwini district of Kwa-Zulu-Natal province, South Africa
Authors: Mashige K. P. , Martin C.
Published: October 2016

Although most of the causes of visual impairment and blindness in the developing world are treatable, many people do not receive eye care attention. The appropriate use of eye care services is a key factor to reducing visual impairment and blindness in any community. However, eye care services are not always provided, accessible or utilized and do not always meet the needs of specific groups; one such group is older adults. The purpose of this study was to evaluate the use of eye care services in adults aged 60 years and older living in the eThekwini district of KwaZulu-Natal, South Africa. Information regarding the use of eye care services was collected from 1008 participants through a questionnaire interview using items derived from the World Health Organization multi-country World Health Survey administered by trained field workers. The participants included 77.3% females and 22.7% males. Their mean age was 68.9 ± 7.4 years (range = 60 to 103 years). Less than half (38.7%) of the participants thought that they should have their eyes tested every year. Although many (57.4%) knew where to go to get treatment for eye problems or to have their eyes tested, a significant proportion (42.5%) did not know. Almost a third (32.8%) felt that they need to get treatment for an eye problem or to have their eyes tested. Less than one third(25.2%) indicated that they last visited a health facility for an eye test 2-5 years ago. Above one third (38.3%) reported that they were told they could not see at distance, 22% reported that theywere told that they had reduced capacity to see at near, while 23.4% and 9.2% respectively were told they had had eye infections or cataracts. Of these, 59.7% stated that new glasses were recom-mended to them as treatment, 22.7% were recommended eye drops and 7.8% had cataract surgery recommended. Most (80.5%) reported that they received the recommended treatment while 19.5% reported that they did not. Of those who reported not receiving the treatment, 36.4% stated that it was due to inability to afford the treatment recommended while 29.1% stated that they were unable to get the treatment due to long waiting times.The majority of participants (86.9%) agreed that the treatment they received solved their eye problems. Knowledge about regular eye examinations and available eye care services was poor amongparticipants in this study. This suggests the need for awareness campaigns and early intervention programmes. Furthermore, cost of services had a significant influence on the affordability of eye care services among participants. (S Afr Optom 2011
Induced prismatic effects due to poorly fitting spectacle frames
Authors: Moodley V. R. , Kadwa F. , Nxumalo B. , Penciliah S. , Ramkalam B. , Zama A.
Published: October 2016

To provide patients with the best vision possible practitioners undertake comprehensive visual examinations and optical dispensing procedures.  Ensuring proper frame alignment is an important part of the spectacle dispensing process.  Ideally,for maximum optical benefit, patients should look through the optical centers of their lenses.  Rays entering a lens at any point other than the optical center will be deviated as long as the lens has power, thus inducing prismatic effects.  These prismatic effects may lead to visual complaints such as asthenopia,blurry vision and headaches.  The aim of the study was to investigate the prevalence of induced prismatic effects due to poorly fitting spectacle frames.  A sample of 100 spectacle wearing subjects was selected as participants.  Questionnaires were completed and any symptoms experienced recorded.  The habitual spectacle position in the primary position of gaze was noted, pupil and optical centers marked and where relevant, induced prism was calculated.  Data was analysed using the ANOVA Kruskal-Wallis and Mann-Whitney tests.  On initial observation of frame position, about45% of subjects were wearing their spectacles incorrectly.  A comparison of the marked pupil centers in primary gaze and optical centers revealed that 100% of participants were found to not be looking through the optical centers of their lenses.  Fifty one percent were within horizontal and 3.12% within vertical ANSI tolerances.  Symp-toms were reported by 50% of subjects experiencing base-out, 0% base-in and 47% vertical induced prismatic effects.  However, no correlation existed between those subjects experiencing induced prism and symptoms reported.  Prism adaptation may account for some participants being asymptomatic.  Sixty three percent of subjects were not aware of the importance of properly fitted spectacle frames.  Proper optical dispensing with associated patient education is necessary to achieve optimal optical benefits of spectacles and careful attention should be given to this aspect by practitioners.  It is recommended that patients return periodically to their optometrists to have the frame alignment assessed and the fit modified if necessary. (S Afr Optom 2011 70(4) 168-174)
Aperture referral in dioptric systems with stigmatic elements
Authors: Harris W. F.
Published: October 2016

A previous paper develops the general theory of aperture referral in linear optics and shows how several ostensibly distinct concepts, including the blur patch on the retina, the effective cornealpatch, the projective field and the field of view, are now unified as particular applications of the general theory.  The theory allows for astigmatism and heterocentricity.  Symplecticity and the generality of the approach, however, make it difficult to gain insight and mean that the material is not accessible to readers unfamiliar with matrices and linear algebra. The purpose of this paper is to examine whatis, perhaps, the most important special case, that in which astigmatism is ignored.  Symplecticity and, hence, the mathematics become greatly simplified. The mathematics reduces largely to elementary vector algebra and, in some places, simple scalar algebra and yet retains the mathematical form of the general approach.  As a result the paper allows insight into and provides a stepping stone to the general theory.  Under referral an aperture under-goes simple scalar magnification and transverse translation.  The paper pays particular attention to referral to transverse planes in the neighbourhood of a focal point where the magnification may be positive, zero or negative.  Circular apertures are treated as special cases of elliptical apertures and the meaning of referred apertures of negative radius is explained briefly. (S Afr Optom 2012 71(1) 3-11)
Familial Exudative Vitreoretinopathy (FEVR)
Authors: Sardiwalla Z. , Ebrahim H. , Sukati V. N.
Published: October 2016

No abstract available
The perception amongst a population of high school students in South Africa about ocular manifestations of HIV/AIDS*
Authors: Melwa I. T. , Oduntan O. A.
Published: October 2016

HIV and AIDS can result in visual impairment, therefore it is important that those who have or atrisk of contracting the disease have a basic knowledge of its ocular manifestations, so that they may seek eye care early. This study assessed the per-ceptions of a sample of senior high school students at the Capricorn district, Limpopo Province, South Africa about the ocular manifestations of HIV/AIDS and its management. Questionnaires were distributed to the students in their classrooms after school hours and upon completion were collected the same day. Data analysis revealed that 27.8% of the participants agreed that HIV/AIDS can affect the eyes. Another 27.8% responded that HIV/AIDS could cause dry eyes. Less than a third (31.4%) indicated that the disease could cause red eyes, 31.5% and 38.1% respectively indicated that HIV/AIDS could cause cancer of the eyelids and the eyeball.  About half of the respondents (52%) agreed that the disease could cause swollen eyelids; while about 46% agreed that vision loss or blindness could occur in HIV/AIDS.  Many (65.6%) indicated that an ophthalmologist or an optometrist should be consulted for HIV/AIDS-related eye problems and only 16.5% reported that traditional healers could be consulted. Perception about the ocular manifestations of HIV and AIDS is poor among the participants, suggesting a need for awareness campaigns and education.  (S Afr Optom 2012 71(3) 117-122)
A comparative study of central corneal thickness (CCT) and intraocular pressure (IOP) in University of KwaZulu-Natal students of Black and Indian ethnicity*
Authors: Sardiwalla Z. , Moodley D. , Ndawonde T. , Madikizela A. , Ngobese N. , Thobela N.
Published: October 2016

Thisstudy compared central corneal thickness (CCT) and intraocular pressure (IOP) of Black and Indian students from the University of Kwa-Zulu-Natal. Two hundred (100 Black and 100 Indi-an) participants of both genders aged 18-25 years (mean and standard deviation; 20.1±1.6 years) participated in this study. CCT and IOP were measured for the right eye of each participant using a Tono-Pachymeter (NT530P) and a Goldmann applanation tonometer (GAT) respectively. Data was analyzed with descriptive, t-test and Pearson’s cor-relation statistics. In the total sample (N = 200), the mean CCT value was 519.5 ± 38.6 μm and CCT was higher in the Indians (526.5 ± 37.2 µm) than in the Blacks (512.4 ± 38.9 µm) (p = 0.01).  Also, it was higher in the females (522.3 µm) than in males (516.7 µm), but the difference was insignificant (p = 0.07). The mean CCT was higher in the Indian males (520.1 µm) than in the Black males (513.2 µm), but the difference was insignificant (p=0.39).  However, it was significantly higher in the Indian females (533 µm) than in the Black females (511.6 µm) (p = 0.003). In the total sample, the mean IOP was 14.6 mmHg and IOP was greater in Indiansthan Blacks (mean = 15.3 ± 2.9 mmHg and 13.8 ± 2.6 mmHg respectively) (p = 0.01). Also, the mean IOP (N = 200) value was slightly higher in the females (14.7 mmHg) than in males (14.5 mmHg) (p = 0.51). The mean IOP was higher in the Indian males (15.0 mmHg) than in the Black males (14.0 mmHg) (p = 0.07) and the mean IOP value was higher in the Indian females (15.7 mmHg) than in the Black females (13.6 mmHg) (p < 0.001). The higher mean IOP value in the Indian than Black participants was attributed to the higher mean CCT values. A positive, but inconsistent association between CCT and IOP was found in this study, the coefficient in the total sample (r = 0.382, p = 0.000), in the Blacks (r = 0.196, p = 0.05) and in Indians (r = 0.498, p = 0.000). A national population study comparing CCT and IOP in the various South African ethnic groups is recommended. Cognizance of these differences should be taken in the diagnoses of glaucoma in these ethnic groups. (S Afr Optom 2012 71(4) 171-177)
Time-domain versus spectral-domain optical coherence tomography: Findings in acute central serous chorioretinopathy*
Authors: Selver O. B. , Aslankara H. , Oner F. H. , Saatci A. O.
Published: October 2016

Aims: To evaluate the optic coherence tomographic (OCT) features in acute central serous chorioretinopathy (ACSC) with time-domain or spectral-domain OCT at Dokuz Eylul University, Department of Ophthalmology, Izmir, Turkey.Subjects and Methods: Clinical data from the Department of Ophthalmology (of Dokuz Eylul University) including fluorescein angiography (FA) and OCT findings of 39 eyes of 34 patients with ACSC were retrospectively analyzed. Eleven eyes (Ntd =11) were examined with time-domain (Stratus OCT 3, Version 4.0) and 28 eyes (Nsd =28) with spectral-domain OCT (Heidelberg HRA2 Spectralis).Results: Of the sample of 34, twenty-four patients (70.6%) were men and 10 women (29.4%). FA demonstrated smokestack type hyperfluorescence in five eyes (12.8%), a round ink blot type hyperfluorescence in 32 eyes (82.1%) and diffuse leak-age in two (5.1%) eyes. Twenty-five eyes (64.1%) had only one leakage site, five eyes (12.8%) hadtwo leakage sites and nine eyes (23.1%) had three or more leakage sites. Detachment of the neurosensory retina was detected in 37 eyes (94.9%, 11 eyes with Stratus OCT and 26 eyes with Spectral OCT). Pigment epithelial detachment (PED) was detected in nine eyes (23.1%, one eye with Stratus OCT and eight eyes with Spectral OCT). Protrusion of the RPE layer was detected in 10 eyes (25.6%, all eyes with Spectral OCT). Both fibrinous exudates and bridging between the neurosensory retina and PED was detected with Spectral OCT in four eyes (10.2%). Retinal dipping was detected with Spectral OCT in two eyes (5.1%).Conclusion: Spectral-domain OCT seems to yield more information and depicts RPE layer protrusion, fibrinous exudates and bridging better when compared to conventional time-domain OCT.  (S Afr Optom 2012 71(4) 166-170)
Repeatability and reproducibility of Tearlab measurements
Authors: Gillan W. D. H.
Published: October 2016

It is well established that the diagnosis of dry eye is difficult. Tear osmolarity is considered by some to be the only metric of dry eye that is repeatable with some claiming that osmolarity is the best diagnostic metric for dry eye. A recently developed system, the Tearlab osmolarity system, is now available that can give a measure of tear osmolarity in less than 60 seconds. It is important that any new instrument be evaluated for its repeatability and reproducibility. The aim of this study was to investigate the repeatability and reproducibility of the Tearlab system by taking multiple, successive measurements of osmolarity of a manufacturer supplied calibration/test solution. The results of this investigation show that the Tearlab osmolarity system provides reasonably accurate, repeatable and reproducible measurements of tear osmolarity.  (S Afr Optom 2013 72(1) 19-24)
Pupillary axis of a heterocentric astigmatic eye
Authors: Harris W. F.
Published: October 2016

The pupillary axis of the eye is a clinically useful concept usually defined as the line through the centre of the entrance pupil that is perpendicular to the cornea. However if the cornea is astigmaticthen, strictly speaking, the entrance pupil is blurred and the pupillary axis is not well defined.  A modified definition is offered in this paper: the pupillary axis is the infinite straight line containing the incident segment of the ray that passes through the centre of the (actual) pupil and is perpendicular to the first surface of the eye.  The definition holds for the naked eye and for an eye with an implant in the anterior chamber.  It also holds for the com-pound system of eye and optical instrument such as a contact lens in front of it if the first surface is interpreted as the first surface of the compound system and the pupil as the limiting aperture of the compound system.  Linear optics is applied to obtain a formula for the position and inclination of the pupillary axis at incidence onto the system; the refracting surfaces may be heterocentric and astigmatic.  The formula allows one to examine the sensitivity of the pupillary axis to displacement of the pupil and any other changes in the anterior eye.  Strictly the pupillary axis depends on the frequency of light but examples show that the dependence is probably negligible.  The vectorized generalization of what is sometimes called angle lambda is easily calculated from the inclination of the pupillary axis and the line of sight. (S Afr Optom 2013 72(1) 3-10)
Perceptions and opinions of graduating South African optometry students on the proposed community service
Authors: Mashige K. P. , Oduntan O. A. , Rampersad N.
Published: October 2016

Community service (CS) was introduced inSouth Africa in an attempt to address the shortageand maldistribution of health care professionalswithin the public sector. The Professional Board forOptometry and Dispensing Opticians (PBODO)has approved legislation for the introductionof CS for graduating optometry students. This study examined the perceptions and opinionsof graduating optometry students regarding the proposed CS. A mixed-method design(questionnaires and interviews) was used. Bothapproaches yielded similar results. The quantitativecomponent included 119 participants, aged between 20 and 35 years (mean age and standard deviation;22.8 ± 2.3 years). There were 43.2% Blacks, 28.5%Whites, 19.1% Indians and 9.2% Coloureds. The qualitative part included fourteen participantsfrom the Optometry Department of the University of KwaZulu-Natal. The major themes emergingfrom the questions concerning the participants’ perceived advantages and benefits of CS were (i) it would improve the eye care service delivery to disadvantaged communities; (ii) it would improve the technical and clinical skills of the graduating optometrists and (iii) it would enhance their confidence, personal and social skills. Some of the perceived drawbacks cited by the participants about such service included poor remuneration and concerns about personal safety, transport and accommodation. The findings of this study suggest that graduating optometry students acknowledge the importance of CS in improving access of many South Africans to quality eye care. In order to maximise the full benefits of CS, all stakeholders need to address the highlighted concerns of the participants. (S Afr Optom 2013 72(1) 11-18)