New Horizons in Ocular Surface and Dry Eye Evaluation

Abstract

Although considered to be the most important of all the human senses, the delicate nature of the human eye gives rise to many potential defects that could impact the quality of sight and if left untreated eventually lead to permanent vision loss. Scientists and engineers have studied human vision with a desire to better understand and diagnose conditions that may compromise sight. With the never-ending advancement of technology, new avenues of exploration are continually becoming available which can offer the potential for reduced invasiveness whilst extracting even greater diagnosis fidelity. Nevertheless, even with new technological possibilities, many potential solutions are not suited to day to day clinical environments and may be cost prohibitive or simply unreasonably complex to perform. In many cases subjective observation techniques introduced over a century ago still find favour today and may be preferred over newer methods due to large accessibility and low training requirements. This thesis is an exploration of cutting-edge technical approaches and developments with the intention of applying them in an original yet rational fashion to achieve mainstream use in real day to day clinical settings for the provision of superior dry eye diagnosis capabilities. The following research will be focused on identifying anterior eye conditions, in particular dry eye which is growing in prevalence and affecting younger age groups. Rather than restricted, in depth focus on a particular technique, this work will consider several unique approaches and lay a strong argument for their viability and subsequent clinical testing in separate, future work. Chapter 2 focuses on improving the commonly used technique of sodium fluorescein viewing with custom created blue excitation and yellow emission filters. Although such subjective fluorescein observation techniques have existed for many years, the custom filters offer a large improvement in viewing performance, filter efficiency and slit lamp hands free usage, and are ready to scale to production with 1,000 units already manufactured and a further 16,000 units on order. Chapter 3 describes research on determining the thickness and degradation of the transparent tear film over the course of a blinking cycle. To date, many attempted measures have produced results with an accepted value in the region of 5 μm. Tear dynamics; refresh, spreading and degradation behaviours are key in providing insight into the stability and premature breakdown leading to dry eye disease, all of which are demonstrated as possible with confocal and interferometric technologies being examined and an average tear film thickness value 3.28 μm and degradation rate of 0.048 ± 0.034 μm-2 being achieved. Lastly, chapter 4 introduces a new anterior eye assessment instrument based on the technique of persistence of vision that is capable of enhancing the ability to detect tear film break up time in a new low cost, non- invasive device. A plethora of additional anterior eye examinations such as corneal topography and slit lamp viewing capabilities are also made possible with this new projection method. The POV scope is a distinctive new approach to anterior eye viewing and gives the ability to capture high resolution, high contrast images that in the near future may be coupled to a machine learning platform to provide a clear diagnosis for common conditions including the multifactorial and inconsistent signs and symptoms of dry eye disease.