Purpose: To investigate whether retinal thickness varies with refractive error. Also secondary to see if there is any difference in retinal thickness between the right and left eye. Methods: The inclusion criteria for the study was subjects without any pathologies, age between 18-45 and refractive error of maximum +0.75 SER and the myopia had no limit, as well as no astigmatism higher then -1.00D. Subjects, which fitted the inclusion criteria for the study, was shown to the OCT room were retinal thickness measurements were acquired first on the right and then left eye. To get the same reading area, the same setup was used and the fixation point was always centered for each patient. After all subjects had undergone the same method the results were analyzed using t-test and regression analysis. Results: The analysis showed a difference between emmetropic eyes and myopic eyes in the peripheral retinal thickness, having the myopes being significantly thinner. The inter myopic analysis showed no difference in retinal thickness in any of the points. This could however be due to the smaller sample size. The comparison between right and left eye showed a good symmetry between the two eyes both in the emmetropic and the myopic group. Conclusions: From this study we can conclude that the myopic group has a thinner peripheral retinal thickness than the emmetropic group. Central retinal thickness is not significantly different but could be due to the smaller sample size. There is no difference in retinal thickness between right and left eye.

It is well known that the colour preferences of ganglion and LGN cells do not match the four perceptually simple colours red, green blue and yellow. It is also known that although colour perception is distorted in the peripheral visual field, there are four hues that appear stable with eccentricity. These are defined as peripherally invariant hues. Both of these observations must in some way reflect the physiological substrate of neurons at different stages of the primary visual pathway. The experiments described here are aimed at understanding the link between the physiology and the perception of colour by studying the characteristics of peripheral colour visionThe following questions have been addressed; i) to what extent does colour matching rely on the retinal physiological substrate? ii) what is the reason for the discrepancy between invariant and unique green and how is cone contrast linked to this paradox? iii) how are the `special' hues (invariant and unique) related to human evolution? iv) how does peripheral colour vision vary between males and females?An asymmetric colour matching paradigm and a colour naming task have been employed. In the colour matching task, 24 chromatic axes of variable purity are used. Observers match the chromaticity of a 3 degree peripheral spot with that of a 1 degree parafoveal spot. The results are expressed in terms of hue rotation, saturation match and cone contrast. In the colour naming experiment the observers name 40 chromatic axes as either red, blue, green or yellow and colour naming functions are derived. The central maxima of these functions are defined as the unique hues. The results suggest that colour matching and cone opponency reflect the characteristics of the retinal neural network as they exhibit nasal-temporal asymmetries, similar to known physiological asymmetries. Although three of the peripherally invariant hues match the unique counterparts, invariant and unique green are markedly different for all observers. In an important control experiment unique hues are shown to be stable with eccentricity and purity. This confirms that these attributes are not confounding factors for the observed discrepancy between invariant and unique green. Unlike for the other 'special' hues the RMS cone contrast of invariant green differs markedly between parafoveal and peripheral targets. It is likely that the cone contrast remains unchanged only if the stimuli excite the same number of cones. Two invariant and two unique hues (blue and yellow) fall on the daylight locus suggesting that discrimination in these regions of the colour space is strongly influenced by terrestrial illumination. Moreover, the inter-individual variability is found to be minimised around the daylight locus showing that the blue-yellow system is more stable across colour normal populations than the red-green system. A statistically significant difference is demonstrated between the peripheral colour vision of males and females. This may be attributed to the M-cone polymorphism which in addition to X-chromosome inactivation, results in more than three cone types in the female retina.

No description available.

<p>The goal of my Ph.D. thesis is to enhance the visualization of the peripheral retina using wide-field optical coherence tomography (OCT) in a clinical setting.</p><p>OCT has gain widespread adoption in clinical ophthalmology due to its ability to visualize the diseases of the macula and central retina in three-dimensions, however, clinical OCT has a limited field-of-view of 300. There has been increasing interest to obtain high-resolution images outside of this narrow field-of-view, because three-dimensional imaging of the peripheral retina may prove to be important in the early detection of neurodegenerative diseases, such as Alzheimer's and dementia, and the monitoring of known ocular diseases, such as diabetic retinopathy, retinal vein occlusions, and choroid masses.</p><p>Before attempting to build a wide-field OCT system, we need to better understand the peripheral optics of the human eye. Shack-Hartmann wavefront sensors are commonly used tools for measuring the optical imperfections of the eye, but their acquisition speed is limited by their underlying camera hardware. The first aim of my thesis research is to create a fast method of ocular wavefront sensing such that we can measure the wavefront aberrations at numerous points across a wide visual field. In order to address aim one, we will develop a sparse Zernike reconstruction technique (SPARZER) that will enable Shack-Hartmann wavefront sensors to use as little as 1/10th of the data that would normally be required for an accurate wavefront reading. If less data needs to be acquired, then we can increase the speed at which wavefronts can be recorded.</p><p>For my second aim, we will create a sophisticated optical model that reproduces the measured aberrations of the human eye. If we know how the average eye's optics distort light, then we can engineer ophthalmic imaging systems that preemptively cancel inherent ocular aberrations. This invention will help the retinal imaging community to design systems that are capable of acquiring high resolution images across a wide visual field. The proposed model eye is also of interest to the field of vision science as it aids in the study of how anatomy affects visual performance in the peripheral retina.</p><p>Using the optical model from aim two, we will design and reduce to practice a clinical OCT system that is capable of imaging a large (800) field-of-view with enhanced visualization of the peripheral retina. A key aspect of this third and final aim is to make the imaging system compatible with standard clinical practices. To this end, we will incorporate sensorless adaptive optics in order to correct the inter- and intra- patient variability in ophthalmic aberrations. Sensorless adaptive optics will improve both the brightness (signal) and clarity (resolution) of features in the peripheral retina without affecting the size of the imaging system.</p><p>The proposed work should not only be a noteworthy contribution to the ophthalmic and engineering communities, but it should strengthen our existing collaborations with the Duke Eye Center by advancing their capability to diagnose pathologies of the peripheral retinal.</p> / Dissertation