No / To determine the test-retest reliability of the Randot stereoacuity test when used as part of vision screening in schools. METHODS: Randot stereoacuity (graded-circles) and logMAR visual acuity measures were gathered in an unselected sample of 139 children (aged 4-12, mean 8.1+/-2.1 years) in two schools. Randot testing was repeated on two occasions (average interval between successive tests 8 days, range: 1-21 days). Three Randot scores were obtained in 97.8% of children. RESULTS: Randot stereoacuity improved by an average of one plate (ie, one test level) on repeat testing but was little changed when tested on the third occasion. Within-subject variability was up to three test levels on repeat testing. When stereoacuity was categorised as 'fine', 'intermediate' or 'coarse', the greatest variability was found among younger children who exhibited 'intermediate' or 'coarse'/nil stereopsis on initial testing. Whereas 90.8% of children with 'fine' stereopsis (</=50 arc-seconds) on the first test exhibited 'fine' stereopsis on both subsequent tests, only approximately 16% of children with 'intermediate' (>50 but </=140 arc-seconds) or 'coarse'/nil (>/=200 arc-seconds) stereoacuity on initial testing exhibited stable test results on repeat testing. CONCLUSIONS: Children exhibiting abnormal stereoacuity on initial testing are very likely to exhibit a normal result when retested. The value of a single, abnormal Randot graded-circles stereoacuity measure from school screening is therefore questionable.

No / Postural instability in older people is associated with an increased risk of falling. This experiment investigated the effects of different gaze strategies on postural stability in older people, when using distance single-vision compared with multifocal (progressive addition lens and bifocal) spectacles. METHODS: Eighteen healthy older habitual multifocal spectacle-wearers (mean age 72.1 +/- 4.0 years) participated in a randomised, cross-over study. Postural stability during quiet standing was assessed as the root mean square excursion in the centre of pressure (RMS-COP) in the antero-posterior direction. Ground reaction force data were collected (for 30 seconds), while subjects viewed one of two visual targets (one square metre) of different spatial frequencies and contrasts, while wearing either distance single-vision or multifocal (progressive addition and bifocal) spectacles. The visual targets were positioned either ahead at eye-level or on the ground (viewing distance 2.06 metres) and viewed under the following head-gaze conditions; 'head neutral-gaze forward', 'head flexed-gaze down' and 'head neutral-gaze down'. RESULTS: The type of spectacles worn or the target viewed had no significant effect on postural stability but postural stability deteriorated (antero-posterior RMS-COP excursion increased) in the 'head neutral-gaze down' compared with the 'head flexed-gaze down' and 'head neutral-gaze forward' conditions (5.9, 5.5 and 5.0 mm respectively, p < 0.001). CONCLUSIONS: Multifocal use had no effect on standing postural stability. Irrespective of spectacles worn, when fixating a visual target positioned at ground level, postural stability was better in the 'head flexed-gaze down' condition compared with the 'head neutral-gaze down' condition. A useful strategy to reduce falling in the older person might be to advise multifocal and distance single-vision spectacle-wearers to flex their heads rather than just lower their eyes when looking downwards.

本研究嘗試不全以負面假設來看待配戴眼鏡對人臉辨識的影響。吾人將以邊緣偵測圖為基礎，以邊點強度的分析來建立一套定位眼鏡的偵測系統。同時用偵測出的鏡框位置，以邊緣點的強度、密度比較的方式，定位眼睛的位置；並以前述兩套偵測演算，採擷其過程的資訊，進一步地定位鼻子與嘴巴的位置。這些演算形成一個簡易的人臉特徵定位系統，其將可處理配戴眼鏡的人臉；吾人也將進一步地經由其處理過程與結果，分析眼鏡對區域人臉辨識的影響，進而引導出非自然物件可能對人臉辨識的阻礙或輔助。 論文也將以全域比對法中的PCA與ICA演算法作一連串的實驗，剖析眼鏡對於全域辨識的影響；此外，亦用相同的方法來測試非自然物(眼鏡)、光源亮度與人臉角度對於人臉辨識阻礙的程度，以探究是否系統值得花費更大的代價，來移除眼鏡這個被一致認定的人臉辨識障礙，並得以在辨識演算法上獲得更高的效能。 / The objective of this thesis is to investigate the efficacy of face recognition systems when the subjects are wearing glasses. We do not presume that non-facial features such as glasses are nuisances. Instead, we will study whether the inclusion of glasses will have a positive impact on the face detection procedure and how it affects the feature extraction process. We will demonstrate how to use techniques based on local feature analysis to reduce the uncertainties in the matching result due to interferences around the eyes and nose caused by optical glasses. We have also conducted extensive experiments to analyze the effect of glasses on face recognition systems based on global matching strategy. Specifically, we perform both principal component analysis (PCA) and independent component analysis (ICA) on face databases with different percentage of subjects wearing eye glasses. It is concluded that external objects such as glasses will have a negative impact on face recognition using global analysis approaches. However, the adverse influences of illumination and pose are more conspicuous during the recognition process. Therefore, one should take caution when attempting to adapt the global matching scheme to handle the difficulties caused by glasses.

Objetivos: Avaliar o desempenho visual(DV), por meio da AV logMAR de alto contraste, sensibilidade ao contaste(SC) e análise de frentes de onda(AFO), em míopes, com óculos e três LCG. Métodos: Estudo clínico e prospectivo, em 40 indivíduos míopes(-1,00D e -4,50D). Exames: AV logMAR de alto contraste, avaliação de SC e AFO. Resultados: A AFO detectou diferença na aberração de terceira ordem sem e com as LCG.. Em relação ao nível trifoil houve diferença entre com e sem LCG. Conclusões: Na avaliação do DV com óculos e com LCG, a AFO é uma medida mais sensível da função visual que a AV LogMAR de alto contraste e a SC. / Objective: to evaluate the visual performance(VP) by Visual acuity(VA)Logmar of high contrast, sensibility of contrast(SC) and wavefront (WF) in myopic patients correct with spectacles and 3 SCL Methods: prospective clinical trial was performed in 40 myopic patients(-1,00 D and -4,50 D). Exams: VA, WF and CS. Results: The WF analysis detected a significant difference in a third order aberration with and without SCL. There was significant difference related to trefoil coefficient in VP between with and without SCL. Conclusion: In VP evaluation with spectacles and SCL the wavefront analysis was more sensible measure of VP when compared with high contrast VA Logmar and CS.

Objetivos: Avaliar o desempenho visual(DV), por meio da AV logMAR de alto contraste, sensibilidade ao contaste(SC) e análise de frentes de onda(AFO), em míopes, com óculos e três LCG. Métodos: Estudo clínico e prospectivo, em 40 indivíduos míopes(-1,00D e -4,50D). Exames: AV logMAR de alto contraste, avaliação de SC e AFO. Resultados: A AFO detectou diferença na aberração de terceira ordem sem e com as LCG.. Em relação ao nível trifoil houve diferença entre com e sem LCG. Conclusões: Na avaliação do DV com óculos e com LCG, a AFO é uma medida mais sensível da função visual que a AV LogMAR de alto contraste e a SC. / Objective: to evaluate the visual performance(VP) by Visual acuity(VA)Logmar of high contrast, sensibility of contrast(SC) and wavefront (WF) in myopic patients correct with spectacles and 3 SCL Methods: prospective clinical trial was performed in 40 myopic patients(-1,00 D and -4,50 D). Exams: VA, WF and CS. Results: The WF analysis detected a significant difference in a third order aberration with and without SCL. There was significant difference related to trefoil coefficient in VP between with and without SCL. Conclusion: In VP evaluation with spectacles and SCL the wavefront analysis was more sensible measure of VP when compared with high contrast VA Logmar and CS.

This is a study on the prevalence of refractive errors and patients requiring refractive services at 15 eye clinics in the Amathole, Chris Hani, Joe Gqabi and OR Tambo District Municipalities of the Eastern Cape. This is an area characterised by extreme poverty where the cost of an eye examination and prescription spectacles remains financially unobtainable for most. Optometry services are provided mainly by private optometrists who service the small proportion of the population that can afford them. Adults and children remain house bound or are labelled as dull and unproductive simply because they don’t have access to an eye examination and a pair of spectacles. Purpose The purpose of the study is to identify patients with refractive errors and those requiring refractive services at the 15 eye clinics in the Eastern Cape. Another purpose is to describe the refractive services that are available to patients attending health facilities, where the eye clinics are conducted. Lastly, the purpose is to explore the possibility of nurses providing refractive services independently or under the supervision of optometrists to supplement the lack to refracting and dispensing services. Study Method A quantitative and qualitative non-experimental descriptive design was used. Research involved the analysis of Vision Care’s eye clinic records collected from 15 eye clinics from January 2010-June 2010. Semi-structured interviews were conducted with 30 nurses working at the 15 health facilities where the eye clinics were conducted using purposive sampling. The quantitative data was analysed using excel spreadsheets and graphs and qualitative data was analysed using coding and categorizing methods. Conclusion According to Vision Care’s data of the patients assessed, 19.2 percent had a refractive error and 54 percent of the patients required refractive services. It is estimated that 71.41 percent of the patients had a refractive error according to the optometrist. Although there were some organisations active in the eradication of cataracts, there was little healthcare available in the form of refraction services. xiv Patients needed to travel an average of 63.8kms to access refraction services against the backdrop of poor roads, poverty and unemployment. 28 out of 30 nurses either ‘strongly agreed’ or ‘agreed’ that nurses could be trained to perform refractions and dispense spectacles. 29 out of 30 nurses thought that this would have a positive impact on eye care. Further research is necessary to assess the feasibility of implementing a nurse operated refractive program and whether it should be within their scope of practice to refract and dispense spectacles.