Sjogren’s syndrome (SS) is a systemic autoimmune disease that presents to eye care practitioners with the hallmark symptom of “dry eye.” Stratifying dry eye patients as Sjogren’s positive or negative is a critical differential diagnosis, as SS patients have numerous systemic complications and a forty times greater risk of developing lymphoma. As such, management of this relatively common dry eye sub-population requires specialized care. Since a firm diagnosis requires testing that is both invasive and expensive, patients should be protected from these tests if they are not warranted. In this thesis, studies were therefore undertaken to determine if SS dry eye could be differentiated from other forms of dry eye using two methods: 1) standard clinical tests used in a multi-disciplinary Sjogren’s syndrome clinic and 2) subsequent biological evaluation of collected tear samples and cells from the ocular surface. The former would allow eye care practitioners to conduct appropriate tests and pose suitable questions to ifferentiate these subgroups, and the latter might serve in the future as a relatively non-invasive quantitative means of differentiating such groups through biomarkers.

Introduction: Tear film osmolality is a product of the varying concentrations of dissolved solutes (proteins, lipids and mucins) in the tear fluid. Research suggests that a hyperosmotic tear film is a trait common to all forms of dry eye, and it may be the driving force causing the discomfort, ocular surface damage and inflammation found in both evaporative and tear deficient forms of dry eye disease. Tear film osmolality has been proposed to be the “gold standard” diagnostic test for the evaluation of dry eye disease, as a distinct separation between tear film osmolalities in normal and dry-eyed (aqueous deficient or evaporative) populations has become evident. Historically, tear film osmolality could only be measured in a laboratory setting and required a highly skilled technician to use the instrumentation. The recent development of easy-to-use, small volume osmometers has made it possible for tear film osmolality to be measured clinically. As these instruments are quite new, there has been very little research completed with them. Therefore, a series of studies was conducted to investigate the utility of one of these new osmometers – the Advanced Instruments Model 3100 Nanolitre Osmometer. The specific aims of each chapter were: - Chapter 3: To determine if the Advanced Instruments Model 3100 Nanolitre Osmometer was capable of quantitatively measuring tear film osmolality in a normal population, using 0.5μL tear samples. - Chapter 4: Previous studies have shown the Advanced Instruments Model 3100 Nanolitre Osmometer not significantly different from another commercially available osmometer (Wescor Vapor Pressure Osmometer) for the measurement of human tears. This chapter examined the repeatability of the new instrument over multiple measurements on the same sample and over multiple days. - Chapter 5: To determine if tear film osmolality values varied significantly over the course of a normal working day in a population that was primarily free from symptoms of dry eye. - Chapter 6: To investigate the relationships between tear film osmolality and other commonly used clinical tests for dry eye disease. The clinical tests examined included various questionnaires designed to assess patient symptoms (Single Item Dry Eye Questionnaire (SIDEQ), the Ocular Surface Disease Index (OSDI), and the McMonnies Dry Eye Questionnaire (MMDEQ) and a linear analogue comfort scale (LACS)), a non-invasive tear break-up time test (NIBUT), and examination of ocular surface redness and tear ferning (TF). Secondarily to determine if the other clinical tests demonstrated significant diurnal variations over the course of a normal working day. - Chapter 7: To measure tear film osmolality in a population with mild to moderate symptoms of dry eye disease, and to compare this value with the osmolality of a population of age-matched controls without the disease. Secondarily, to investigate the relationship between tear film osmolality and patient comfort in a population with mild to moderate symptoms of dry eye disease. Methods: - Chapter 3: Tears were collected from 40 volunteer participants with a capillary tube. Some participants were non-contact lens wearers (Non-CL), while others wore either soft or rigid contact lenses (CL). Tear film osmolality was measured with the Advanced Instruments Model 3100 Nanolitre Osmometer. - Chapter 4: Tears were collected from 10 volunteer participants using two different collection techniques. Collections were repeated on three separate days (6 study visits total); three osmolality measurements per collection were taken using the Advanced Instruments Model 3100 Nanolitre osmometer. - Chapter 5: Tears were collected from 40 volunteer participants in two separate studies (n=80 in total). Tears were collected with a capillary tube three times a day (morning, mid-day and afternoon), on two separate days (6 study visits total). Tear film osmolality was measured with the Advanced Instruments Model 3100 Nanolitre Osmometer. - Chapter 6: Clinical tests were administered and tear samples were collected using a capillary tube from 40 volunteer participants. Measurements were taken three times a day (morning, mid-day and afternoon), on two separate days (6 study visits total). Tear film osmolality was measured with the Advanced Instruments Model 3100 Nanolitre Osmometer. - Chapter 7: Participants were classified as either having dry eye disease (DE) or not having dry eye disease (NDE) based on a clinical examination that included a case history, phenol red thread test and biomicroscopy (white light and sodium fluorescein assessment). Tear samples were then collected from all participants using a capillary tube and tear film osmolality was measured with the Advanced Instruments Model 3100 Nanolitre Osmometer. Participants also completed the SIDEQ, the OSDI, and the MMDEQ. Results: - Chapter 3: The mean tear film osmolality of the population was 298.7±11.4mOsm/Kg. CL wear (soft or rigid) did not appear to have a significant effect on tear film osmolality (CL: 298.5±11.2mOsm/Kg vs. Non-CL: 298.9±11.5mOsm/Kg), although this study was not designed to specifically look at the effects of contact lens wear on tear film osmolality. - Chapter 4: There was reasonably good concordance between measurements of tear film osmolality taken with the Advanced Instruments Model 3100 Nanolitre Osmometer (intraclass correlations range from 0.6497 (F= 0.0582) to 0.9550 (F = 0.5893)). Repeatability appeared to be affected by significant changes in ambient humidity (>10% per day). Concordance was similar with both sampling techniques. - Chapter 5: In the first study, no significant diurnal change in tear film osmolality was found (p>0.05), although a significant difference in measurements taken on Day 1 compared to Day 2 was found (p=0.040). When the first and last 10 participants enrolled were compared, the difference between days was present in the first 10 participants, but not in the last 10; it is likely that the investigator underwent a learning process during the period of the study, and that reflex tearing occurred more often in the early portion of the study compared with the latter portion. In the second study, no significant diurnal change in tear film osmolality was found (p>0.05) and no significant difference in measurements taken on Day 1 compared to Day 2 was found (p>0.05). When tear film osmolality was compared with the number of hours participants were awake, no significant correlation was found (r = 0.07044). - Chapter 6: Significant correlations were not found between tear film osmolality and SIDEQ (r = 0.1347), OSDI (r = 0.0331), MMDEQ (r = 0.2727), LACS (r = -0.1622), NIBUT (r = -0.2280), subjectively graded redness (r=-0.2280), or objectively measured redness (r = 0.1233). A weakly significant correlation was found between TF and tear film osmolality (r = 0.3978). None of the clinical measures (LACS, NIBUT, subjective or objective redness or TF) varied significantly over the course of the day. - Chapter 7: Tear film osmolality was higher in both the right (DE = 311.1±12.4mOsm/Kg, NDE = 306.2±11.2mOsm/Kg) and left eyes (DE = 313.2±11.9mOsm/Kg, NDE = 304.0±7.5mOsm/Kg) of participants, but the difference was only statistically significant in the left eye. Tear film osmolality did not correlate significantly with DE patient symptoms using any of the questionnaires (SIDEQ, OSDI, MMDEQ). Conclusions: - Chapter 3: The Advanced Instruments Model 3100 Nanolitre Osmometer appeared to be capable of measuring tear film osmolality in a normal population. Our population mean was slightly lower than what is reported to be normal (305mOsm/Kg), but it still fell within the range of values reported as normal (297 – 318mOsm/Kg). - Chapter 4: The Advanced Instruments Model 3100 Nanolitre Osmometer demonstrated reasonably good repeatability for the measurement of human tear samples. Unfortunately, the instrumentation appeared to be affected by dramatic weather changes. Maintaining the instrument in a humidity controlled environment may resolve this problem. - Chapter 5: Tear film osmolality did not appear to vary significantly over a normal working day. Inducing reflex tearing, perhaps with an unskilled investigator collecting the tears, can be a significant source of error (as demonstrated in the first study). - Chapter 6: Tear film osmolality did not correlate well with other clinical instruments designed to assess either patient symptoms or signs of dry eye disease in a normal population. Tear film osmolality and tear ferning did demonstrate a weakly significant positive correlation. None of the clinical measures assessed demonstrated a significant diurnal variation over the course of a normal working day. - Chapter 7: Tear film osmolality appeared to be higher in participants with mild to moderate symptoms of dry eye when compared with age matched, asymptomatic controls. Tear film osmolality did not correlate well with patient symptoms in a population of mild to moderate severe dry eyed individuals.

The impact of uncoordinated growth of the optical components of the eye may stimulate different levels of monochromatic aberrations in the growing eyes of the children. This thesis aimed to examine the impact of age, visual acuity and refractive error on higher order aberrations as well as to determine the relationship between them. Hartman Shack images taken with the Welch Allyn® SureSight Autorefractor were calibrated in order to determine the Zernike coefficients up to the 8th order for a pupil diameter of 5mm. The MATLAB code proposed by Thibos et al that follows the standard for reporting the optical aberrations of the eye was the basis of code written for this study. Modification was required to suit the specific needs of the Welch Allyn® SureSight Autorefractor. After calibration the lower order aberrations could then be compared with the results from cyclopledged retinoscopy. RMS values of aberrations and Strehl ratios were computed to examine the optical performance of the eye. A total of 834 Hartmann-Shack images of 436 children (mean age 3.94± 0.94 years, range 3 to 6 years) were examined in this study (right eyes 436; left eyes 398).The sample had a mean (± STD) spherical equivalent of 1.19 ± 0.59D, a mean with-the-rule astigmatism (J0) of 0.055 ± 0.22D, and a mean oblique astigmatism (J45) of 0.01±0.14D. Visual acuity varied from 6/6 to 6/18. Moderate mirror symmetry was found between the eyes. Like refractive error, higher order aberrations declined with age in this sample. There was an impact of higher order aberrations on refractive error. Significantly higher ocular aberrations were found in the higher hyperopic group (SE>+2.0D) compared to emmetropic (-0.5<SE<+0.5D) and low hyperopic groups (+0.5<SE<+2.0D). The Strehl ratio was significantly lower in the high hyperopic group. Higher Strehl ratios were observed for better acuity groups but the average Strehl ratios among the different visual acuity groups were not statistically significant. In conclusion, there was an impact of age on the ocular aberrations. A wider range of age from birth to adolescence is required for further investigation. This could be indirectly influenced by the age related changes in refractive error as the correlation between refractive error and the higher order aberrations were significant. This finding also concludes that Strehl Ratio alone is not capable of perfectly describing the visual acuity of the eye; other metrics such as the neural transfer function and neural noise are necessary to describe the resultant visual performance of the eye.

Current understanding of sensitivity and sensation experienced across the ocular surface remains limited. This project explored the regional variation of corneal sensitivity and transducer function, interaction of sensory and autonomic nerves in the lacrimal functional unit, and the ocular surface sensitivity in Dry Eye and with silicone hydrogel (SH) lens wear. Experiments were undertaken, using Belmonte esthesiometer to deliver pneumatic mechanical, chemical and thermal stimuli and Cochet-Bonnet esthesiometer for tactile stimuli, to the cornea and conjunctiva. Psychophysical methods were used to determine the thresholds of stimulus detection, and the magnitude of sensations to suprathreshold stimulation was estimated assuming Steven’s power law. Additionally, tear secretion in response to corneal sensory input was determined by tear meniscus height measured using Optical Coherence Tomography. Sensitivity to pneumatic cool and mechanical stimuli varied slightly across the cornea while chemical sensitivity was not different between regions. The transducer function was also similar between central and peripheral cornea but different between stimulus modalities. In comparison, the reflex tearing response to suprathreshold stimuli was greater with central corneal stimulation. Also, corneal and conjunctival hypersensitivity was found in the dry eye symptomatic group, and it appeared to be associated with symptom severity, tear film stability and corneal epitheliopathy. Refitting with SH lenses after an initial no-lens interval led to increased conjunctival pneumatic mechanical sensitivity, while corneal tactile sensitivity showed a decrease. In addition, corneal staining induced by certain lens-solution combination appeared to be accompanied by increased corneal and conjunctival sensitivity. In conclusion, the position-invariant corneal sensitivity to pneumatic mechanical, chemical and thermal stimuli suggests that the distribution of human corneal sensory fibres may be more homogeneous than previously hypothesised. The mechanisms mediating the sensory aspect of corneal nociception may be similar across the cornea, while, perhaps due to the importance of the visual axis, the tear reflex response to central and peripheral cornea seems to be driven by different neural circuitry, perhaps at the higher levels of the sensory processing pathway. It appears that alteration in sensory processing of the ocular surface occurs in Dry Eye and accompanies SH lens-solution-induced corneal staining. This altered sensitivity seems to be more prominent in the conjunctiva than in the cornea.

Purpose: To test the hypothesis that the fixational stability (FS) of the amblyopic eye (AME) in strabismics will improve when binocular integration is enhanced through ocular alignment and inter-ocular suppression is attenuated by reducing the contrast to the fellow eye (FFE). Methods: 7 strabismic amblyopes (age: 30.8±9.7 yrs) (5 esotropes and 2 exotrope) (VA: AME=0.50±0.30; FFE=-0.12±0.04) showing clinical characteristics of central suppression were recruited. Suppression was then attenuated by a balance point procedure where the contrast to the FFE was reduced in order to maximize binocular integration during a global motion task (GMT) (Baker, 2007). In one case the balance point could not be determined, and the participant was excluded. Ocular alignment was established with a haploscope. Participants dichoptically viewed similar targets [a cross (2.3°) surrounded by a square (11.3°) visual angle] set at 40cm. Target contrasts presented to each eye were either equal (EQ) or attenuated in the FFE (UNEQ) by an amount defined by the GMT. FS was measured over a 5 min period (Viewpoint® Eye Tracker, Arrington Research) and quantified using bivariate contour ellipse areas (BCEA) in four different binocular conditions; unaligned/EQ, unaligned/UNEQ, aligned/EQ and aligned/UNEQ. FS was also measured in 6 control subjects (Age: 25.3±4 yrs; VA: -0.1±0.08). Results: Alignment of the AME was transient and lasting between 30 to 80 seconds. Accordingly, FS was analyzed over the first 30 seconds using repeated measures ANOVA. Post hoc analysis revealed that for the amblyopic subjects, the FS of the AME was significantly improved in aligned/EQ (p=0.015) and aligned/UNEQ (p=0.001). FS of FFE was not different statistically across conditions. BCEA(FFE) & BCEA(AME) were then averaged for each amblyope in the 4 conditions and compared with normals. This averaged BCEA (reduced FS) was significantly greater (p=0.0205) in amblyopes compared to controls except in the case of alignment coupled with reduced suppression (aligned/UNEQ) (p=0.1232). Conclusion: Fixation stability in the amblyopic eye of strabismics appears to improve directly with the degree of binocular integration. The hypothesis is therefore retained.

ABSTRACT Purpose: The primary aim of the study (i.e. Chapter 3) was to compare the magnitude of retinal vascular reactivity in arterioles of varying diameter in healthy, young subjects. The secondary aims were to determine: a) if there are any order effects in terms of provoking vasoconstriction or vasodilation first; and b) the repeatability of the vascular reactivity measurements. An additional aim (i.e. Chapter 4) was to determine the effect of healthy aging on the relationship between retinal vascular reactivity and vessel diameter. Method: The sample comprised 10 healthy, young subjects (mean age 26.5 years, SD 4.04) and 7 healthy, older subjects (mean age 55.43 years, SD 5.41). Each subject from the young age group attended for three sessions. The first session was used to determine eligibility and select hemodynamic measurement sites. At sessions 2 and 3, O2 and CO2 were sequentially administered to the subjects using a face mask and sequential re-breathing circuit (to maintain standardized hyperoxia and hypercapnia). The order of vasoconstriction and vasodilation was varied across sessions 2 and 3. The design of the protocol was simplified for the subjects from the older age group. Each subject from the older group attended for one visit. O2 and CO2 were administered to the subjects using a face mask and sequential re-breathing circuit. The order of gas provocation was varied among the subjects (i.e. hyperoxia or hypercapnia first). For both groups, measurements of vessel diameter, centerline blood velocity and derived blood flow were acquired at each condition (i.e. baseline, during stabilized vasoconstriction, vasodilation, and recovery) at two discrete measurement sites along the supero-temporal arteriole. Results: The results of the repeated measures ANOVA showed a significant difference between the narrow and wide measurement sites for the younger group for flow (p≤ 0.0003) and a significant influence of inspired gas provocation on flow for both protocols (p<0.0001). In addition, the interaction of measurement site and inspired gas provocation was significant (p<0.0001). The magnitude of retinal vascular reactivity showed a significantly greater blood flow response for the wide measurement site (p<0.0001). O2 provocation resulted in vasoconstriction that was still present up to 10 minutes after cessation of the stimulus (order effect of O2; p≤0.046). No such order effect was apparent for CO2 provocation (order effect of CO2; p=0.352). The group mean blood flow Coefficient of Repeatability (COR) for the narrow measurement site was 0.74 µl/min (relative to group mean flow of 4.85 µl/min ± SD 1.31) and for the wide measurement site was 1.49 µl/min (relative to group mean flow of 11.29 µl/min ± SD 3.55). There was no difference between the young and the older age groups in retinal vascular reactivity for both the narrow (two-tailed Student t-test, p=0.8692) and wide (two-tailed Student t-test, p=0.2795) measurement sites. Conclusion: This study demonstrated that the magnitude of retinal vascular reactivity was greater for arteriolar measurement sites with wider baseline vessel diameters. In addition, it demonstrated that hyperoxic provocation resulted in a persistent vasoconstriction up to 10 minutes after cessation of the stimulus. The study demonstrated that the repeatability of retinal blood flow measurements in absolute terms is lower for smaller diameter vessels. Finally, this study also suggests that age does not affect the relationship between retinal vascular reactivity and vessel diameter.

In a teaching clinic, healthcare students and their supervisors talk with their patients in the examination room and they talk about their patients during teaching consultations outside the examination room. Effective doctor-patient communication helps to establish management plans that are appropriate for both doctors and their patients. Amid a pressure to provide more patient-centered care, communicating effectively with older adult patients is particularly crucial because the occurrence of health problems and the likelihood of age-based communication barriers and negative attitudes increase with age. This project is a qualitative, collective case study of eye examinations, case presentations and participant interviews. This study took place in the Primary Care Clinic at the University of Waterloo, School of Optometry. Participants included 8 fourth-year optometry students, 5 supervising optometrists, and 10 patients between 60 and 85 years of age. The study involved audio-recording and analyzing eye examinations of older adult patients, case discussions about these patients, and interviews of older adult patients, optometry students and their optometrist supervisors. Data were analyzed using a constant-comparative approach, consistent with grounded theory. This study identified some of the discursive features of and reflections about patient-centered communication during the talk with and about older adult patients. During the eye examinations, optometry students incorporated five types of verbal communication that were consistent with a patient-centered model: Patient Agenda, Social Talk, Analogies, Patient Agency, and Health Promotion & Prevention. Although these successful attempts to incorporate patient-centered communication strategies were evident in the talk with patients, optometry students routinely engaged in seven other verbal strategies that challenged this patient-centered ethos: Closed-Ended Questions, Biomedical and Technical Language, Patient as a Problem, Unacknowledged Patient Voice, Patient Understanding, Doc Talk, and Caregiver Agency. Two types of discursive strategies related to patient-centered care were identified in the talk about older adult patients during novice case presentations: Voice of Optometry and Voice of Patient. The Voice of Optometry incorporated field-sanctioned language strategies including three subcategories: Biomedical, Technical and Judgment. In contrast, the Voice of Patient represented various levels of patient agency: Passive Recipient, Negotiated Agency and Patient Agency. According to their interviews, optometry students received limited explicit training, in both classroom and clinic instruction, on how to talk with and about patients. During their interviews, optometry students and their supervisors made clear distinctions between patient–centered and doctor-centered care. Most of the students and supervisors believed that the optometry profession and the optometry school promoted patient-centered care. Elements of patient voice were represented in the eye examinations, the case presentations and the post-examination patient interviews. During novice case presentations patient voice was often fragmented into sound bytes of the original patient statements or translated into field-sanctioned language. Although many instances of patient education and counselling were evident throughout the eye exams, limited discussion occurred in the novice case presentations between students and their instructors about what to say to patients, In addition, the majority of topics addressed during educational and counselling moments were not discussed during the novice case presentations. Additionally, post-examination patient recall regarding education and counselling was generally limited. Throughout this study, talk about age appeared in four ways: 1) caregivers used age to make clinical decisions during case presentations, 2) caregivers referenced age during counseling and education to explain eye and vision changes, 3) patients commented on the impact of age on themselves, and 4) caregivers spoke about how they considered age when speaking to their patients. While the caregivers generally valued a patient-centered approach, the talk with and about patients was skewed towards strategies that may limit the ability to support this ethos. It is questionable what audience (i.e. patient or supervisor) optometry students value and how this affects their ability to adopt patient-centered communication strategies. Findings from this study suggest that caregivers and their patients might benefit from some changes in the way patient-centered practice is taught and practiced in this optometry teaching clinic. As a greater understanding develops of the strategies of and challenges to patient-centered practices in optometry, it is my hope that optometry training programs as well as optometry professional organizations will further embrace patient-centered practices.

Introduction Menopause which is defined as a permanent physiological, or natural, cessation of menstrual cycle, plays an important role in the development of ocular surface dryness symptoms and there is an increased prevalence of dry eye in women, especially those aged over 50. Despite the high prevalence of dry eye in post-menopausal women (PMW), very few studies have been undertaken to understand dry eye disease in a group of PMW who are not on Hormone Replacement Therapy (HRT). Studies in the past on PMW have primarily focused on the relationship between HRT and dry eye. Hence, a series of studies were undertaken to understand the clinical aspects of dry eye and their relationship to a variety of tear film components, in a group of PMW with and without symptoms of dry eye. The specific aims of each chapter were as follows: • Chapter 4: To characterize symptoms of dry eye using questionnaires, namely Ocular Surface Disease Index Questionnaire© (OSDI) and the Indiana Dry Eye Questionnaire (DEQ). • Chapter 5: To characterize clinical signs and symptoms in participants who present with and without symptoms of dry eye. • Chapter 6: To compare tear osmolality and ferning patterns in participants with and without dry eye symptoms. • Chapter 7: To investigate the potential relationship between subjective symptoms and clinical signs with tear film lipocalin and lysozyme concentrations in participants with and without dry eye symptoms. • Chapter 8: To optimize a technique for the isolation of total RNA (ribo nucleic acid) and total protein derived from conjunctival epithelial cells collected via conjunctival impression cytology (CIC). • Chapter 9: To quantify the expression of MUC1 (mucin1) and MUC16 (mucin16) mRNA and protein and to investigate the potential relationship between mucin expression and tear film breakup time in a group of participants with and without dry eye symptoms. Methods • Chapter 4: Participants were categorized as being symptomatic or asymptomatic of dry eye based on their response to the OSDI questionnaire. These results were then compared to the DEQ, which has questions related to the frequency of ocular surface symptoms and their diurnal intensity. • Chapter 5: Non invasive tear breakup time (NITBUT) was evaluated using the ALCON Eyemap®. Tear volume was assessed using the Phenol Red Thread (PRT) test and bulbar conjunctival hyperemia was measured using objective (SpectraScan PR650© Spectrophotometer) and subjective (slit lamp) methods. • Chapter 6: Tears were collected via capillary tube. A freezing point depression osmometer was used to measure the osmolality of the tear film. The tear ferning test was performed and evaluated for the quality of ferning, based on the Rolando grading system. • Chapter 7: Tears were collected via capillary tube and an eye wash method. Tear lysozyme and lipocalin concentrations were determined via Western blotting. • Chapter 8: CIC was collected using either Millipore (MP) or Poly Ether Sulfone (PES) membranes. RNA and protein isolation was performed using two different RNA isolation techniques. Two methods of protein isolation from CIC discs were evaluated. RT-PCR of mRNA for MUC1 and western blotting of lipoxygenase type 2 protein (LOX2) was performed to confirm the collection of intact RNA and total protein respectively. • Chapter 9: Tears were collected via capillary tube and an eye wash method. CIC was collected using MP membrane. Expression of MUC1 and MUC16 mRNA was assessed via real time PCR. Expression of both membrane-bound and soluble MUC1 and MUC16 were quantified via Western blotting. Results • Chapter 4: The OSDI total score and sub scores for the Non Dry Eye (NDE) and Dry Eye (DE) groups were significantly different (NDE =7.43 ± 7.71 vs DE = 24.87 ± 13.89; p<0.001). The DEQ scores showed that the DE group exhibited a higher frequency and intensity of symptoms than the NDE group, which worsened as the day progressed (p<0.001). • Chapter 5: The DE group exhibited a significantly shorter NITBUT (5.3 ± 1.7 vs 7.0 ± 2.7 secs; p=0.0012). Tear volume was significantly lower for the DE group (19.3 ± 5.1mm vs. 16.3 ± 5.6mm; p=0.031). Bulbar hyperemia was significantly higher in the DE group for both objective (u’ = 0.285 ± 0.006 vs. 0.282 ± 0.006; p=0.005) and subjective techniques (48.4 ± 10.0 vs 40.6 ± 10.4; p=0.0011). • Chapter 6: Osmolality values in DE individuals were significantly higher than the NDE (328.1 ± 20.8 vs. 315.1 ± 11.3 mOsm/kg; p = 0.02). There was a significant difference between the DE and NDE participants for the ferning patterns (p = 0.019). No significant correlation between tear osmolality and tear ferning was noted (DE: r = 0.12; p > 0.05, NDE: r = -0.17; p > 0.05). • Chapter 7: No difference in tear lysozyme or lipocalin concentration was found between DE and NDE groups, irrespective of tear collection method. Method of collection significantly influenced absolute concentrations (p<0.008). • Chapter 8: There was no significant difference between the two procedures used to isolate RNA and protein from CIC membranes (p>0.05). Total RNA yield was greater with the MP membrane. The mean yield of protein extracted from MP membrane using the two protein isolation techniques also did not show a significant difference. • Chapter 9: No difference was found in the expression of either MUC1 or MUC16 protein or mRNA expression between symptomatic DE and NDE (p>0.05). Weak correlations were found between the NITBUT values compared with either soluble or membrane bound MUC1 and MUC16 expression. Conclusions • Chapter 4: Questionnaires are useful tools to symptomatically divide participants into dry eyed and non dry eyed candidates. However, the questionnaire used to categorise patients can impact on the outcome variables determined. • Chapter 5: Post-menopausal women with dry eye symptoms demonstrate shorter NITBUT, lower tear volume and increased bulbar conjunctival hyperemia than those who have no symptoms. • Chapter 6: Tear osmolality in DE is higher than in NDE. There is a tendency towards less ferning in persons over 50 years of age, regardless of their symptoms. • Chapter 7: Comparison of clinical data with lipocalin and lysozyme concentrations failed to reveal statistically significant correlations. The concentration of either protein was not associated with tear stability or secretion. • Chapter 8: The total RNA yield was greater with the MP membrane. RNeasy Mini (RN) (Qiagen) method is recommended due to enhanced speed as well as on-column isolation and DNase digestion capabilities. CIC with MP membranes followed by immediate freezing and then extraction and processing facilitates the collection of total protein from human conjunctival cells. • Chapter 9: No difference was found in the expression of either MUC1 or MUC16 protein or mRNA expression between symptomatic PMW and asymptomatic controls.

Wavefront-guided (WFG) laser in situ keratomileusis (LASIK) differs from conventional surgery by applying a refined algorithm for tissue removal, based on information from preoperative wavefront aberration data. Since the introduction of this technology, there have been few investigations comprehensively reporting outcomes, particularly for hyperopic treatments. This thesis aimed to determine the impact of myopic and hyperopic WFG LASIK on visual acuity, contrast sensitivity, higher order aberrations and subjective ratings, as well as determine the relationship between these outcome measures. Bilateral WFG LASIK was performed on 324 myopic eyes (162 subjects) and 62 hyperopic eyes (31 subjects). High contrast (HC) and low contrast (LC) best-corrected visual acuity (BCVA) and contrast sensitivity were assessed using ETDRS charts and vertical sinusoidal gratings, respectively. Higher order ocular aberrations were measured using a Shack-Hartmann wavefront sensor and analyzed across a 5.0 mm pupil. Subjective ratings were assessed using a closed-ended categorical questionnaire. Assessments were conducted prior to surgery and at three and six months postoperatively. WFG LASIK had minimal impact on BCVA and contrast sensitivity; however there was an impact on the magnitude and profile of higher order aberrations, which differed between the myopic and hyperopic groups. There was a greater increase in higher order aberrations for the hyperopic group, who also had a tendency to have lower visual outcomes and worse subjective ratings. Despite these results, there were no associations between subjective ratings and higher order aberrations, LC BCVA or contrast sensitivity for both groups and a clear understanding of the relationship between these outcome measures was not apparent. Factor analysis revealed a variety of factors that contributed to the outcome measures for this data set, with the three main factors being: subjective ratings, vision and optical quality. In conclusion, WFG LASIK had excellent outcomes in terms of visual acuity, contrast sensitivity, and subjective ratings, despite an increase in higher order aberrations compared with those found prior to surgery. Hyperopic outcomes were slightly worse than myopic outcomes. Further investigation is required to determine the impact of higher order aberrations on visual acuity, contrast sensitivity and subjective ratings, as well as the relationship between these measures.

Flicker defined form (FDF) is a temporally-dependent illusion created by the counterphase flicker of randomly positioned element dots, that preferentially stimulates the magnocellular system. Previous studies have found improvement with peripheral presentation, a resistance to blur and a dependence on high temporal frequencies. (Quaid & Flanagan, 2005a; Quaid & Flanagan, 2005b). Although it is seemingly very different from most luminance defined, static stimuli, it is still unknown in what ways it differs. The current study aimed to determine how FDF varies or is similar to static, luminance defined stimuli. Current results showed that FDF could be matched to particular spatial frequencies, and improved with increasing background structure and area. Shapes could be discriminated from each other and recognized. These results suggest that although FDF is dependent on motion pathways for temporal dynamic perception, it could also benefit from the input of form perception pathways, depending on the cues present in the stimulus (e.g. background structure, area). Results also showed that FDF does not benefit from Gestalt rules of contour closure, unlike some static stimuli, although related studies have shown that FDF could still be detected in spite of blur. These studies suggest that FDF appears to rely on motion perception pathways, areas such as MT, but is easier to perceive at times due to overlap in function with shape perception pathways, areas such as IT. As such FDF shares many characteristics with other motion-defined-form stimuli, but uniquely shares aspects of form vision.