bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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)
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)
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)
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)