The transparent outer layer of the eye, known as the cornea, has a vital function inbending and directing light onto the retina, which is essential for achieving clear vision. Current methods of correcting refractive errors that are becoming increasingly popular include LASIK and PRK surgeries; however, these invasive techniques come with downsides as well such as permanent thinning of the cornea. This thesis proposes the use of a non-invasive technique called electromechanical reshaping (EMR) that can be applied to the cornea to induce curvature change. EMR was performed on New Zealand white rabbit globes using a concave platinum lens as the working electrode in a 3-electrode setup. The primary outcomes to be measured include the aforementioned curvature change of the cornea and the change in distribution of collagen orientation: to observe such changes the advanced imaging modalities of optical coherence tomography (OCT) and second harmonic generation (SHG) have been employed. The curvature data can be analyzed through a developed MATLAB approach that reconstructs the 3D surface of the cornea from 2D cross-sectional OCT images and sphere-fits the surface to extract the radius of curvature. The collagen structural change can be analyzed in FIJI software using OrientationJ to quantify the orientation of collagen fibers. These methods serve as a sound quantitative way to analyze the outcomes of EMR. This thesis found that the mean curvature increased from 5193.73 µm ± 597.09 µm to 5429.16 µm ± 736.08 µm following EMR application. Regarding collagen structural change, most of the eyes did not show a statistically significant difference following EMR application. Due to experimental error because of the lack of standardization of pressure, however, the corneal curvature did not consistently increase and the corneas did not resemble the radius of curvature of the platinum lens used in EMR (7.486 mm). Future directions include standardization of the pressure applied on the cornea by the platinum lens, simultaneous OCT imaging during EMR application, seeing if corneas post-EMR retain curvature changes, and transitioning to applying EMR on eyes intact in New Zealand white rabbit heads.

Comparison of Nasal Obstruction Symptom Evaluation Scale with a Septoplasty Deformity Grading System for the Evaluation of Nasal Obstruction

By

Jeffrey Tan Gu

Master of Science in Biomedical and Translational Science

University of California, Irvine, 2017

Dr. Brian J.F. Wong, Chair

Background: Nasal airway obstruction (NAO) is among the most common chronic complaints of patients seen in otolaryngology practices. The evaluation of NAO consists of a combination of objective and subjective assessments. Among the subjective assessments, the Nasal Obstruction Severity Evaluation (NOSE) survey has become among the most widely used measures of symptom severity. A variety of objective measures have been studied, however there is much controversy preventing wider adoption of objective measures for NAO due to lack of correlation with subjective measures. Among the current septal deformity classification systems, there is a lack of precision in anatomic localization of defects and grading of deformities.

Aims: This study seeks to develop and validate a septal deformity grading system (SDG) that accounts for anatomic location and grading of deformity severity.

Methods: Retrospective cohort study of patients with nasal obstruction presenting to the UCIMC. Subjects were given pre- and post-operative NOSE questionnaires and were evaluated by a facial plastic surgeon using our SDG system. Validity and reliability analyses were conducted on the SDG results. Statistical analyses were conducted on SDG and NOSE data to assess and compare instruments. A composite SDG score was created by weighting each variable by its factor loading from PCA. SDG, and NOSE scores were divided into high and low groups using the 75th and 25th percentiles respectively.

Results: 95 patients met inclusion criteria. 52 patients had a complete set of pre- and post-operative NOSE, and SDG questionnaires. Four constructs were identified on the SDG questionnaire using PCA. Cronbach’s coefficient was ≥0.7 for SDG and pre- and post-operative NOSE scores within our study population. There was a significant difference in pre- and post-op NOSE scores (Z score -6.88, p<0.001). Correlations between NOSE and SDG scores were not statistically significant, and convergent construct validity was not achieved. Subgroup analyses determined a significant difference in primary vs revision operations (p<0.001), history vs no history of nasal trauma and nasal/septal surgery (p=0.025, and 0.003 respectively) between composite score groups. A series of univariate logistic regression models determined the odds of having revision operation to be 72.4% higher given a high composite SDG score than low composite SDG score (p=0.018). The odds of having a history of nasal trauma were 8 times higher for high SDG scores than low SDG scores (p=0.014), and odds of having a history of nasal/septal surgery were 94.4% higher for low composite SDG scores than high composite SDG scores. Comparisons between SDG, pre-and post-operative NOSE scores determined significant differences between primary and revision operations, as well as between patients with and without a history of nasal trauma, and prior nasal/septal surgery.

Conclusions: We have developed a septal deformity grading system that improves upon currently available septal deformity classification systems by addressing the challenge of providing a reliable and consistent method for surgeons to characterize septal deviations for preoperative or postoperative evaluation. Our septal deformity grading scores provide anatomic information on the severity of nasal septal deformities, and may be valuable when used in conjunction with subjective data gathered from the NOSE questionnaire.