Cellular responses to changes in pressure are implicated in numerous disease processes. In glaucoma apoptosis of retinal ganglion cells (RGCs) is associated with elevated intra-ocular pressure (IOP), however the exact cellular basis of this link remains unclear. This research aimed to examine the direct response of neuronal cells to elevated hydrostatic pressure in terms of apoptosis. We developed an in vitro model consisting of a pressure chamber to adjust ambient hydrostatic pressure, a source of neuronal cells and methods to measure apoptosis in these cells. The neural cells examined were primary retinal cultures, four neuronal cell lines (B35, PC12, C17, NT2), and the RGC-5 cell line. Pressure conditions selected were within physiological limits; 100 mmHg above atmospheric pressure (as seen clinically in severe acute glaucoma) and extended in RGC-5 neurons to 30 mmHg (chronic glaucoma) and 15 mmHg (normal IOP). Apoptosis was detected by cell morphology and specific immunochemical markers: TUNEL and Annexin V. Caspase-3 activation, a known pathway of apoptosis, was also investigated in RGC-5 neurons. These fluorescent markers were detected and quantified by automated Laser Scanning Cytometry. Negative controls were treated identically except for the application of pressure, while positive controls were generated by treatment with a known apoptotic stimulus. The results showed that neurons responded to elevated hydrostatic pressure directly and that an apoptotic process was induced. There was a greater level of apoptosis in pressurised cells compared to the negative controls. This apoptotic effect at high pressures was seen in primary rat retinal cultures and in both undifferentiated (B35, C17, NT2, RGC-5) and differentiated (PC12, RGC-5) neuronal cell lines. RGC-5 neurons showed a graded response, proportionate to the level of pressure elevation, representative of the severity of analogous clinical settings (acute, chronic glaucoma & normal). RGC-5 neurons also showed increased activation of Capsase-3. Thus this pathway may play a role in pressure induced apoptosis. Our findings indicate that pressure alone may act as a stimulus for apoptosis in neuronal cells. We suggest the possibility of novel mechanisms of pressure related mechanotransduction and cell death, relevant to the pathogenesis of glaucoma.

Objective: To examine the changes of visual field and retinal nerve fiber layer (RNFL) measurements and the risk of glaucoma progression before and after taking off intraocular pressure (IOP) lowering medication in Chinese patients with ocular hypertension. Design: Prospective study. Participants: 106 ocular hypertension patients (4 were excluded because there was no 1 year follow up examination). Method: All patients underwent visual field testing by Humphrey Field Analyser and Retinal Nerve Fiber Layer (RNFL) thickness measurement by a spectral-domain optical coherence tomography. Eyes without glaucomatous visual field defect and had an IOP ?30mmHg were instructed to stop taking IOP lowering medication and measurements of IOP, visual field and RNFL measurements were taken. Changes in the visual field mean deviation, average, superior and inferior RNFL thickness and the risk of developing glaucoma between the baseline and follow-up examinations were compared between the groups with and without stopping IOP lowering medications. Logistic regression was used to analyze the association between corneal hysteresis, ocular pulse amplitude and the onset of glaucoma. Results: There were 73 patients with IOP lowering medications taken off and 29 with continued medications. No significant differences were found in the changes of visual field mean deviation, average RNFL thickness and the risk of glaucoma progression (P=0.92, P=0.81, P=0.35, respectively) between the groups. Ocular pulse amplitude was a significant predictor of glaucoma development by functional (-0.61, P=0.047) and structural criteria (-0.74, P=0.024). Conclusion: There were no functional and structural changes in patients with ocular hypertension after stopping IOP lowering medications in one year. Low ocular pulse amplitude could be a predictive factor for the conversion from ocular hypertension to glaucoma. Clinicians should not prescribe IOP-lowering medication simply base on high IOP. / published_or_final_version / Medicine / Master / Master of Medical Sciences

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Diss. (sammanfattning) Umeå : Univ., 2006. / Härtill 5 uppsatser.

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Man, Xiaofei. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 138-162). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese.

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M.Phil. (Optometry) / The primary aim of this research was to investigate whether the Icare® rebound tonometer may be used in place of the Goldmann tonometer to obtain accurate and reliable intraocular pressure measurements on a sample of the general population seeking eye care, in a South African context. Due to the portability of the Icare®, lack of dependency on other instrumentation and power source, together with the ease of use with minimal training, and without the use of topical anaesthetic favourable results of the instrument may lead to its widespread use. This could aid in earlier diagnosis of glaucoma where intraocular pressure remains the only modifiable risk factor. In the South African context, where a high prevalence of undiagnosed primary open angle glaucoma has been found, access and accuracy of intraocular pressure measurement could save and extend functional vision in this country. Patients presenting at the Department of Optometry for routine eye examinations were selected utilizing convenience sampling. The right and left eyes of 113 patients were assessed using both the Icare® TA01i and the Goldman applanation tonometer by independent examiners for each method, all readings of intraocular pressure with the Goldman being taken by the same experienced examiner. The age of the patients ranged from 20 to 89 years with a mean age 50.29 ±20.97 years. Using the Oculus Pachycam® when it became available, central corneal thickness was obtained on 71 patients (142 eyes). Analysis of data using descriptive statistics from SPSS (Statistical Programs for the Social Sciences) was performed in addition to the Bland-Altman method of comparative analysis for sets of data of corrected and uncorrected measurements between the instruments...

D.Phil. / That the eye is essentially a first-order optical instrument is evidenced by the success Gaussian optics has met with in optometry and ophthalmology. An unfortunate consequence of this approach is that a brief review of the literature on the topic of intraocular lens power calculation gives one the impression that the character of such a lens is described fully by its dioptric power. This is not so. Indeed, the idea that a thin refracting interface can somehow embody the optical character of the thick intraocular lens can, and in many ways has, limited the scope of intraocular lens power formula. The purpose of this dissertation is to apply the methods of linear algebra to the investigation of the first-order optical character of the stigmatic and astigmatic pseudophakic eye. This work attempts to lay a solid foundation for the study of the pseudophakic eye in the context of first-order astigmatic optics. While the majority of concepts and results of this dissertation are directly applicable to the study of the pseudophakic eye, an attempt has been made to ensure that the methods outlined in this work may be applied to the study of optical systems in the broader context of first-order optics. Central to this work are the members of the non-abelian symplectic group Sp(2n) under the operation of conventional matrix multiplication. The elements are evendimensional, non-singular symplectic matrices with unit determinant which are referred to here as ray transferences. These matrices act on the members of even-dimensional vector spaces so as to preserve a particular skew-symmetric, non-degenerate bilinear pairing referred to as the symplectic form. The laws that govern the operation of these matrices, the three symplectic relations, flow naturally from the structure of the symplectic group. From the ray transference four 2„e 2 fundamental properties of an optical system may be defined, the dilation A , the disjugacy B , the divergence C and the divarication D. A number of additional optical properties can be derived from the fundamental properties. Examples of derived properties include the dioptric power F , the negative of the divergence C and refractive state 0 F . The ray transference is used here in the derivation of a set of new intraocular lens formulae for the pseudophakic eye. These formulae are entirely general, working equally well in both stigmatic and astigmatic pseudophakic eyes in which additional (possibly astigmatic) intraocular devices may already be present. Formulae for both distant and near objects are provided. The constraints under which the divergence of a thick (possibly bitoric) intraocular lens is conserved despite changes in the lens are investigated. Furthermore, the constraints under which the refractive state of the pseudophakic is conserved in spite of changes in the thick intraocular lens are investigated. We find that there exist an infinite number of thick intraocular lenses that will produce a given refractive outcome, say emmetropia, in the pseudophakic eye. The basic theory of matrix differentiation with respect to a scalar variable is utilized in the study of the changes in the optical character of the pseudophakic eye following axial translation of a variety of intraocular lens systems. A novel method of representing the changes in the stigmatic and antistigmatic properties of refraction on account of axial translation and rotation of a toric intraocular lens in the astigmatic eye is presented and numerical examples are provided. The analysis permits the calculation of the ideal axial lens position and orientation in the astigmatic pseudophakic eye. Such methods will prove increasingly important in refractive data analysis, particularly in light of the development of continuously adjustable intraocular devices. / Prof. W.F. Harris