This thesis has investigated nearwork-induced transient myopia and accommodation responses in relation to refractive stability, multichromatic stimuli and orthokeratology. Five individual studies have been carried out. Initially an investigation into the temporal and dioptric aspects of nearwork-induced transient myopia was undertaken, suggesting that increased task duration does not increase the level, or slow the regression of post-task NITM, however an increase in the dioptric demand of the task does. In the second study, a longitudinal myopia progression study, these findings were related to short term myopia progression. The third investigation demonstrates the feasibility of measuring the biometric correlates of nearwork-induced transient myopia using a low coherence reflectometry device (LenStar, Haag Streit Koeniz, Switzerland). Fourthly, a comparison of the differences between static and dynamic accommodative responses, microfluctuations and nearwork-induced transient myopia produced when viewing a black/white target as oppose to a red/blue target has suggested the possibility of four accommodative responses to this multichromatic stimulus. Further investigation will be necessary to investigate if any of these response types are related to myopia progression. 2 The final study investigates the effect of two different designs of orthokeratology contact lenses (C5 and polynomial) on visual function. It appears to be the case that although the polynomial lens design has a larger refractive effect than the C5 lens it reduces both high and low contrast corrected visual acuity to a greater extent. The higher the baseline mean spherical equivalent refractive error the larger the detrimental effect.

This thesis has investigated nearwork-induced transient myopia and accommodation responses in relation to refractive stability, multichromatic stimuli and orthokeratology. Five individual studies have been carried out. Initially an investigation into the temporal and dioptric aspects of nearwork-induced transient myopia was undertaken, suggesting that increased task duration does not increase the level, or slow the regression of post-task NITM, however an increase in the dioptric demand of the task does. In the second study, a longitudinal myopia progression study, these findings were related to short term myopia progression. The third investigation demonstrates the feasibility of measuring the biometric correlates of nearwork-induced transient myopia using a low coherence reflectometry device (LenStar, Haag Streit Koeniz, Switzerland). Fourthly, a comparison of the differences between static and dynamic accommodative responses, microfluctuations and nearwork-induced transient myopia produced when viewing a black/white target as oppose to a red/blue target has suggested the possibility of four accommodative responses to this multichromatic stimulus. Further investigation will be necessary to investigate if any of these response types are related to myopia progression. 2 The final study investigates the effect of two different designs of orthokeratology contact lenses (C5 and polynomial) on visual function. It appears to be the case that although the polynomial lens design has a larger refractive effect than the C5 lens it reduces both high and low contrast corrected visual acuity to a greater extent. The higher the baseline mean spherical equivalent refractive error the larger the detrimental effect. / College of Optometrists

Cataract surgery is the most commonly performed surgery within the UK with 400,000 surgeries performed each year. Currently no guidelines exist for clinicians regarding target refraction discussions, spectacle provision post-operatively and driving advice following surgery. The PhD aimed to start the process of developing pre- and post-operative management guidelines for patients developed by both optometrists and ophthalmologists which could then be disseminated to both professions in the hope of improving the overall outcome of surgery. The current literature highlighted target refraction discussions were lacking or non-existent which left some myopes dissatisfied after surgery due to an emmetropic target refraction leaving them unable to read without glasses as they did prior to surgery. Target refraction discussions were found to be linked with years of experience and this needs further exposure in continuing professional development. Post-operative driving advice was found to be inconsistent and vary between practitioners and between optometry and ophthalmology. Advice was found to vary from driving “immediately” following surgery up to 6 weeks post-operatively. Re-analysis of (de Juan et al. 2013) data during our systematic review and meta-analysis found refraction to be stable 1-2 weeks following surgery for 93% of patients. It was found a large change between pre- and post-surgery cylindrical power/axis may be an indicator that refractive stability has not occurred. Although this study had limitations it confirmed refraction is stable sooner than the current guidelines of 4-6 weeks. Finally, we used a Delphi process to develop refractive management guidelines with a total of fifteen recommendations finalised.