Purpose: To determine whether semi-scleral contact lenses (sSCL) can be appropriately fitted using corneal sagittal depth measurements, and to determine the impact of fit on visual acuity, effect of time on topographic corneal clearance and comfort ratings. Method: Three sSCL (Jupiter 15mm; Essilor) were fit to 20 subjects who had previous diagnoses of KC (n=18) or PMD (n=2). The fitting of the sSCL were based on the CSD measured with the Visante™ OCT at a 15mm chord on the horizontal meridian. To select the sSCL from the diagnostic trial lens set, values of 325 (lens 1), 375 (lens 2) and 425 (lens 3) μm were randomly added in sequence to the CSD. Subjects were allowed to wear each of the sSCL for 1hour. After this time, the central corneal clearance (CCC) was assessed using an UL-OCT, high contrast visual acuity (HCVA) and low contrast visual acuity (LCVA) were measured using a LogMAR VA chart and comfort ratings were obtained using a comfort rating scale (0-100). Results: The mean CSD in the horizontal meridian was 3.78±0.53 (range: 3.33-4.17) mm at a 15mm chord. The mean CCC was 190±100, 360±120 and 450±170 µm for each lens respectively (p=0.001). The mean CCC loss was 30.00±40.00, 30±60.00 and 40.00±50 µm for each lens respectively (p>0.05). The mean HCVA for lenses 1, 2 and 3 were 0.05±0.12, 0.07±0.11 and 0.11±0.08 respectively, which were significantly different (p=0.02). Tukey post hoc analysis demonstrated that this difference was only significant between lenses 1 and 3 (p=0.01). Similar findings were found for LCVA. The overall comfort rating for all three sSCL was 77.7±10.6. The comfort ratings for lenses 1, 2 and 3 were 74.9±9.2, 79.7 ±11.6 and 78.6±10.8 respectively. These differences were not significantly different (p=0.24). Conclusion: Evaluation of CSD can be used effectively to select which sSCL to fit on the eye. The results of this study suggest that lens 2 (adding 375 μm to the CSD) gave the best combination of VA and comfort ratings. However, evaluation of the fluorescein pattern must be balanced with the VA and comfort ratings for successful fitting of sSCL in a clinical setting. There was also a likelihood of topographic corneal loss after 1 hour of sSCL wear; however, this may vary depending on many factors such as scleral zone and its relationship with the scleral conjunctiva. Eyelid force, design of the contact lens and other unknown factors may play a part in the contact lens settling time and amount.

Purpose: To determine whether semi-scleral contact lenses (sSCL) can be appropriately fitted using corneal sagittal depth measurements, and to determine the impact of fit on visual acuity, effect of time on topographic corneal clearance and comfort ratings. Method: Three sSCL (Jupiter 15mm; Essilor) were fit to 20 subjects who had previous diagnoses of KC (n=18) or PMD (n=2). The fitting of the sSCL were based on the CSD measured with the Visante™ OCT at a 15mm chord on the horizontal meridian. To select the sSCL from the diagnostic trial lens set, values of 325 (lens 1), 375 (lens 2) and 425 (lens 3) μm were randomly added in sequence to the CSD. Subjects were allowed to wear each of the sSCL for 1hour. After this time, the central corneal clearance (CCC) was assessed using an UL-OCT, high contrast visual acuity (HCVA) and low contrast visual acuity (LCVA) were measured using a LogMAR VA chart and comfort ratings were obtained using a comfort rating scale (0-100). Results: The mean CSD in the horizontal meridian was 3.78±0.53 (range: 3.33-4.17) mm at a 15mm chord. The mean CCC was 190±100, 360±120 and 450±170 µm for each lens respectively (p=0.001). The mean CCC loss was 30.00±40.00, 30±60.00 and 40.00±50 µm for each lens respectively (p>0.05). The mean HCVA for lenses 1, 2 and 3 were 0.05±0.12, 0.07±0.11 and 0.11±0.08 respectively, which were significantly different (p=0.02). Tukey post hoc analysis demonstrated that this difference was only significant between lenses 1 and 3 (p=0.01). Similar findings were found for LCVA. The overall comfort rating for all three sSCL was 77.7±10.6. The comfort ratings for lenses 1, 2 and 3 were 74.9±9.2, 79.7 ±11.6 and 78.6±10.8 respectively. These differences were not significantly different (p=0.24). Conclusion: Evaluation of CSD can be used effectively to select which sSCL to fit on the eye. The results of this study suggest that lens 2 (adding 375 μm to the CSD) gave the best combination of VA and comfort ratings. However, evaluation of the fluorescein pattern must be balanced with the VA and comfort ratings for successful fitting of sSCL in a clinical setting. There was also a likelihood of topographic corneal loss after 1 hour of sSCL wear; however, this may vary depending on many factors such as scleral zone and its relationship with the scleral conjunctiva. Eyelid force, design of the contact lens and other unknown factors may play a part in the contact lens settling time and amount.

No description available.

Purpose: To examine the variables that influence lipid deposition on conventional and silicone hydrogel contact lens materials and to build a physiologically relevant in vitro model of lipid deposition on contact lenses. Methods: Lipid deposition on contact lens materials can lead to discomfort and vision difficulty for lens wearers. Using a variety of radiochemical experiments and two model lipids (cholesterol and phosphatidylcholine), a number of clinically significant parameters that may influence lipid deposition were examined. • The optimization and characterization of a novel artificial tear solution (ATS) was examined (Chapter 3) • Optimization of an extraction system to remove deposited cholesterol and phosphatidylcholine from various contact lens materials (Chapter 4) • The influence of different tear film components on lipid deposition was researched (Chapter 5) • The efficiency of hydrogen peroxide disinfecting solutions to remove deposited lipid from contact lenses was investigated (Chapter 6) • The effect of intermittent air exposure on lipid deposition was examined through the use of a custom built “model blink cell” (Chapter 7) Results: A novel complex ATS designed for in-vial incubations of contact lens materials was developed. This solution was stable and did not adversely affect the physical parameters of the contact lenses incubated within it. An efficient extraction protocol for deposited cholesterol and phosphatidylcholine was optimized based on chloroform and methanol with the addition of water and acetic acid for phosphatidylcholine extraction. Overall, cholesterol and phosphatidylcholine deposition is cumulative over time and found to deposit in greater masses on silicone-containing hydrogels. Cholesterol and phosphatidylcholine deposition is influenced by the composition of the incubation medium and air exposure which occurs during the inter-blink period. Hydrogen peroxide disinfecting solutions were able to remove only marginal amounts of lipid from the contact lenses, with the surfactant containing solution removing more. Conclusion: This thesis has provided hitherto unavailable information on the way in which lipid interacts with conventional and silicone hydrogel contact lens materials and the in vitro model built here can be utilized in various ways in the future to assess other aspects and variables of lipid and protein deposition on a variety of biomaterials.

The main purpose of this thesis is to create and validate a visual acuity model with experimentally obtained aberrations of human eyes. The other motivation is to come up with a methodology to objectively predict the potential benefits of photorefractive procedures such as customized corrections and presbyopic LASIK treatments. A computational model of visual performance was implemented in MATLAB based on a template matching technique. Normalized correlation was used as a pattern matching algorithm. This simulation describes an ideal observer limited by optics, neural filtering, and neural noise. Experimental data in this analysis were the eye’s visual acuity (VA) and 15 modes of Zernike aberration coefficients obtained from 3 to 6 year old children (N=20; mean age= 4.2; best corrected VA= 0 (in log MAR units)) using the Welch Allyn Suresight instrument. The model inputs were Sloan Letters and the output was VA. The images of Sloan letters were created at LogMAR values from -0.6 to 0.7 in steps of 0.05. Ten different alphabet images, each in ten sizes, were examined in this model. For each simulated observer the results at six noise levels (white Gaussian noise) and three levels of threshold (probability of the correct answer for the visual acuity) were analyzed to estimate the minimum RMS error between the visual acuity of model results and experimental result.

Contact lens success is primarily driven by comfort of the lens in eye. Over the years, many modifications have been made to the lens surface and bulk material to improve comfort of the lens, however 50% of contact lens wearers still report dry eye symptoms while wearing their lenses. Wettability of the lens material plays a large role in lens comfort, primarily due to its influence in tear film stability. In vitro wettability of contact lenses has typically been assessed by measuring the water contact angle on the lens surface. Currently there are three techniques to measure the in vitro wettability of contact lenses, the sessile drop technique, captive bubble technique, and the Wilhelmy balance method. To date, there is much published on assessing wettability using the sessile drop and captive bubble technique, however there is no data published looking at the in vitro wettability of hydrogel contact lenses measured by the Wilhelmy balance method. Accumulation and deposition of tear components on the lens surface can also affect lens performance, by altering the wettability of the lens surface and causing lens spoilage. The majority of in vitro studies looking at deposition of tear components on the lens surface dope the lenses in tear solutions for a set period of time. None of these studies have investigated the impact of exposing the lenses to tear solutions, then exposing them to the air and then back into the tear solution, which mimics the process during blinking. In Chapter 2, an evaluation of the influence of lens preparation on the wettability of contact lenses measured by the sessile drop technique was conducted. The wettability of 6 silicone hydrogel and one conventional lens material was assessed. Lenses were blot dried on either a microfiber cloth or lens paper for different drying periods and contact angles were measured using the sessile drop technique. There were large variations in results using the microfiber cloth after all drying periods, but there was little variation in results after lenses were blot dried on lens paper for approximately 20 seconds. Thus, it was determined that for future contact angle analysis using the sessile drop technique that lenses should be blot dried for roughly 20 seconds on lens paper. This method was used consistently for the rest of the experiments in which the sessile drop technique was used to measure contact angles. The remainder of Chapter 2 compared the contact angles of different lens materials measured by the sessile drop technique and Wilhelmy balance method. The wettability of five different silicone hydrogel lens materials was assessed directly out-of-blister and after a 48 hour soak in saline. There were significant differences in contact angles for the lens materials between the two techniques. There were also significant differences in contact angles directly out-of-blister and after the 48 hour soak. Results from this study suggested that different methods of measuring wettability can produce different results and that blister pack solutions can alter the wettability of lens materials. Chapter 3 measured the physical properties of blister pack solutions of silicone hydrogel lenses. The pH, osmolality, surface tension, and viscosity of the blister solutions for 9 silicone hydrogel lenses, 2 conventional lenses, and 2 saline solutions were measured. The osmolality of the blister solutions followed a trend, in that blister solutions manufactured by the same company had the same osmolality. Products produced by Johnson & Johnson had the highest osmolality. Blister solutions that contained additional wetting agents had higher viscosities compared to blister solutions without added wetting agents. The main conclusion from this study was that adding wetting agents to blister solutions could alter the physical properties of the blister solutions. The purpose of Chapter 4 was to measure the physical properties of the blister pack solutions of daily disposable lenses and to evaluate the wettability of the lens materials and substantivity of the blister solutions, using a method in which lenses were cycled through 5 minute soaks in saline to mimic blinking. Five daily disposable lens materials were evaluated, one of which was shipped in a blister solution with added surfactants and wetting agents. The wettability of the lenses was assessed using the sessile drop technique and Wilhelmy balance method. The lens with the modified blister solution had a lower surface tension and higher viscosity compared to all the other blister solutions. The same trend in osmolalties as those reported in Chapter 3, were found with blister solutions made by the same manufacturer having the same osmolality. The wettability varied across lens materials. Overall, the lens material with the added components to the blister solution had the lowest contact angle. Chapter 5 investigated the deposition of tear components onto the surface of conventional and silicone hydrogel lens materials and looked at the impact of this on changes in wettability. Three lens materials used in Chapter 4 were exposed to a saline solution, lysozyme solution, and a complex tear solution for 5 minutes, 1 hour, 4 hours, and 8 hours. The wettability was assessed after each time point using the sessile drop and Wilhelmy balance methods. There was little to no deposition on the lens materials that had the highest in vitro CAs in Chapter 4, exemplified by no change in wettability after being soaked in the lysozyme and complex tear solutions. There was deposition on the lens materials with the lowest CAs in Chapter 4, exemplified by a significant increase in wettability after being soaked in the lysozyme and complex tear solutions. Results indicate that there is some deposition onto one lens material, as shown by the change in wettability of the lens surface. These results were further used to validate a method used in Chapter 6. The experiment conducted in Chapter 6 was similar to the experiment in Chapter 5, except that the lenses were not soaked in the three solutions but rather exposed to the solutions in a “model blink cell”. The model blink cell moves lenses in and out of solution at a set time interval, in an attempt to mimic blinking. The interval was set so the lenses would be placed for 1 second in solution and 5 seconds exposed to the air. The same lens materials used in Chapter 5 were used in for this experiment. The lenses were exposed to a saline solution, lysozyme solution and complex tear solution for 5 minutes, 1 hour, 4 hours, and 8 hours. Much like in Chapter 5, deposition on the lens materials was determined by a change in the lens wettability. There were differences in the results of this chapter and that of Chapter 5, with deposition occurring on two of the lens materials rather than just one. This result indicates that the drying of the lens surface for 5 seconds out of solution has an effect on the deposition of tear components on certain lens materials. Thus, the model blink cell may be a useful tool for future deposition studies. Overall this thesis demonstrated that preparation of the lens material can cause variation in contact angles. Different methods of measuring in vitro wettability of contact lenses can produce different results and thus the method used to assess wettability should always be stated. The physical properties of blister pack solutions can change with added wetting agents and surfactants, and components from blister solutions can alter the initial wettability of contact lenses. In vitro deposition of proteins onto the lens surface can vary with techniques, and finally, deposition of tear components onto the surface of contact lenses can alter the lens wettability.

The main purpose of this thesis is to create and validate a visual acuity model with experimentally obtained aberrations of human eyes. The other motivation is to come up with a methodology to objectively predict the potential benefits of photorefractive procedures such as customized corrections and presbyopic LASIK treatments. A computational model of visual performance was implemented in MATLAB based on a template matching technique. Normalized correlation was used as a pattern matching algorithm. This simulation describes an ideal observer limited by optics, neural filtering, and neural noise. Experimental data in this analysis were the eye’s visual acuity (VA) and 15 modes of Zernike aberration coefficients obtained from 3 to 6 year old children (N=20; mean age= 4.2; best corrected VA= 0 (in log MAR units)) using the Welch Allyn Suresight instrument. The model inputs were Sloan Letters and the output was VA. The images of Sloan letters were created at LogMAR values from -0.6 to 0.7 in steps of 0.05. Ten different alphabet images, each in ten sizes, were examined in this model. For each simulated observer the results at six noise levels (white Gaussian noise) and three levels of threshold (probability of the correct answer for the visual acuity) were analyzed to estimate the minimum RMS error between the visual acuity of model results and experimental result.

Contact lens success is primarily driven by comfort of the lens in eye. Over the years, many modifications have been made to the lens surface and bulk material to improve comfort of the lens, however 50% of contact lens wearers still report dry eye symptoms while wearing their lenses. Wettability of the lens material plays a large role in lens comfort, primarily due to its influence in tear film stability. In vitro wettability of contact lenses has typically been assessed by measuring the water contact angle on the lens surface. Currently there are three techniques to measure the in vitro wettability of contact lenses, the sessile drop technique, captive bubble technique, and the Wilhelmy balance method. To date, there is much published on assessing wettability using the sessile drop and captive bubble technique, however there is no data published looking at the in vitro wettability of hydrogel contact lenses measured by the Wilhelmy balance method. Accumulation and deposition of tear components on the lens surface can also affect lens performance, by altering the wettability of the lens surface and causing lens spoilage. The majority of in vitro studies looking at deposition of tear components on the lens surface dope the lenses in tear solutions for a set period of time. None of these studies have investigated the impact of exposing the lenses to tear solutions, then exposing them to the air and then back into the tear solution, which mimics the process during blinking. In Chapter 2, an evaluation of the influence of lens preparation on the wettability of contact lenses measured by the sessile drop technique was conducted. The wettability of 6 silicone hydrogel and one conventional lens material was assessed. Lenses were blot dried on either a microfiber cloth or lens paper for different drying periods and contact angles were measured using the sessile drop technique. There were large variations in results using the microfiber cloth after all drying periods, but there was little variation in results after lenses were blot dried on lens paper for approximately 20 seconds. Thus, it was determined that for future contact angle analysis using the sessile drop technique that lenses should be blot dried for roughly 20 seconds on lens paper. This method was used consistently for the rest of the experiments in which the sessile drop technique was used to measure contact angles. The remainder of Chapter 2 compared the contact angles of different lens materials measured by the sessile drop technique and Wilhelmy balance method. The wettability of five different silicone hydrogel lens materials was assessed directly out-of-blister and after a 48 hour soak in saline. There were significant differences in contact angles for the lens materials between the two techniques. There were also significant differences in contact angles directly out-of-blister and after the 48 hour soak. Results from this study suggested that different methods of measuring wettability can produce different results and that blister pack solutions can alter the wettability of lens materials. Chapter 3 measured the physical properties of blister pack solutions of silicone hydrogel lenses. The pH, osmolality, surface tension, and viscosity of the blister solutions for 9 silicone hydrogel lenses, 2 conventional lenses, and 2 saline solutions were measured. The osmolality of the blister solutions followed a trend, in that blister solutions manufactured by the same company had the same osmolality. Products produced by Johnson & Johnson had the highest osmolality. Blister solutions that contained additional wetting agents had higher viscosities compared to blister solutions without added wetting agents. The main conclusion from this study was that adding wetting agents to blister solutions could alter the physical properties of the blister solutions. The purpose of Chapter 4 was to measure the physical properties of the blister pack solutions of daily disposable lenses and to evaluate the wettability of the lens materials and substantivity of the blister solutions, using a method in which lenses were cycled through 5 minute soaks in saline to mimic blinking. Five daily disposable lens materials were evaluated, one of which was shipped in a blister solution with added surfactants and wetting agents. The wettability of the lenses was assessed using the sessile drop technique and Wilhelmy balance method. The lens with the modified blister solution had a lower surface tension and higher viscosity compared to all the other blister solutions. The same trend in osmolalties as those reported in Chapter 3, were found with blister solutions made by the same manufacturer having the same osmolality. The wettability varied across lens materials. Overall, the lens material with the added components to the blister solution had the lowest contact angle. Chapter 5 investigated the deposition of tear components onto the surface of conventional and silicone hydrogel lens materials and looked at the impact of this on changes in wettability. Three lens materials used in Chapter 4 were exposed to a saline solution, lysozyme solution, and a complex tear solution for 5 minutes, 1 hour, 4 hours, and 8 hours. The wettability was assessed after each time point using the sessile drop and Wilhelmy balance methods. There was little to no deposition on the lens materials that had the highest in vitro CAs in Chapter 4, exemplified by no change in wettability after being soaked in the lysozyme and complex tear solutions. There was deposition on the lens materials with the lowest CAs in Chapter 4, exemplified by a significant increase in wettability after being soaked in the lysozyme and complex tear solutions. Results indicate that there is some deposition onto one lens material, as shown by the change in wettability of the lens surface. These results were further used to validate a method used in Chapter 6. The experiment conducted in Chapter 6 was similar to the experiment in Chapter 5, except that the lenses were not soaked in the three solutions but rather exposed to the solutions in a “model blink cell”. The model blink cell moves lenses in and out of solution at a set time interval, in an attempt to mimic blinking. The interval was set so the lenses would be placed for 1 second in solution and 5 seconds exposed to the air. The same lens materials used in Chapter 5 were used in for this experiment. The lenses were exposed to a saline solution, lysozyme solution and complex tear solution for 5 minutes, 1 hour, 4 hours, and 8 hours. Much like in Chapter 5, deposition on the lens materials was determined by a change in the lens wettability. There were differences in the results of this chapter and that of Chapter 5, with deposition occurring on two of the lens materials rather than just one. This result indicates that the drying of the lens surface for 5 seconds out of solution has an effect on the deposition of tear components on certain lens materials. Thus, the model blink cell may be a useful tool for future deposition studies. Overall this thesis demonstrated that preparation of the lens material can cause variation in contact angles. Different methods of measuring in vitro wettability of contact lenses can produce different results and thus the method used to assess wettability should always be stated. The physical properties of blister pack solutions can change with added wetting agents and surfactants, and components from blister solutions can alter the initial wettability of contact lenses. In vitro deposition of proteins onto the lens surface can vary with techniques, and finally, deposition of tear components onto the surface of contact lenses can alter the lens wettability.

The corneal epithelium is a vital tissue which must retain its integrity to preserve vision and protect against harmful bacterial infections and other insults. Corneal disease represents the second most common cause of world blindness after cataract.1 Examination of this tissue is therefore important in any ophthalmic routine, and in particular in contact lens practice where an increased number of factors, such as lens material, lens fit, care solution and contamination may directly affect its integrity. The ocular surface cell collection apparatus (OSCCA) allows safe and efficacious collection of human corneal epithelial cells2 and may provide the ability to examine cytological changes to the human cornea during lens wear. The overall objective of this project was to demonstrate the efficacy and reliability of the OSCCA as a tool to collect human corneal epithelial cells and examine cytological changes to the human cornea. This was achieved by characterizing the phenotype and viability status of cells collected from the ocular surface using the OSCCA and by comparing the obtained results with samples collected using other non-invasive techniques. There was a high level of uncertainty whether or not the cells collected were in fact corneal or conjunctival epithelial cells. Chapter 2 and 3 showed the Hoechst and PI were not optimal stains to measure the viability status of cells collected with the OSCCA because there was an unanticipated overlap of the fluorescence from PI+ nucleated cells into the blue spectrum and the Hoechst stained both live and dead cells. Chapter 4 looked at other cytological stains and concluded that the LIVE⁄DEAD® Viability⁄Cytotoxicity Kit (calcein AM/ethidium homodimer-1) was the most appropriate stain to use with the OSCCA collected cells due to the lack of overlap between stains. Chapter 3 showed that cells that stained with sodium fluorescein stained with only Hoechst and not PI. Since Hoechst stains live and early apoptotic cells and PI stains cells that are late stage apoptotic, necrotic and dead cells, we can conclude that sodium fluorescein stains live and early apoptotic cells. Similarly in chapter 5 it was found that cells that stained with sodium fluorescein stained exclusively with calcein blue AM and not ethidium homodimer-1.

The corneal epithelium is a vital tissue which must retain its integrity to preserve vision and protect against harmful bacterial infections and other insults. Corneal disease represents the second most common cause of world blindness after cataract.1 Examination of this tissue is therefore important in any ophthalmic routine, and in particular in contact lens practice where an increased number of factors, such as lens material, lens fit, care solution and contamination may directly affect its integrity. The ocular surface cell collection apparatus (OSCCA) allows safe and efficacious collection of human corneal epithelial cells2 and may provide the ability to examine cytological changes to the human cornea during lens wear. The overall objective of this project was to demonstrate the efficacy and reliability of the OSCCA as a tool to collect human corneal epithelial cells and examine cytological changes to the human cornea. This was achieved by characterizing the phenotype and viability status of cells collected from the ocular surface using the OSCCA and by comparing the obtained results with samples collected using other non-invasive techniques. There was a high level of uncertainty whether or not the cells collected were in fact corneal or conjunctival epithelial cells. Chapter 2 and 3 showed the Hoechst and PI were not optimal stains to measure the viability status of cells collected with the OSCCA because there was an unanticipated overlap of the fluorescence from PI+ nucleated cells into the blue spectrum and the Hoechst stained both live and dead cells. Chapter 4 looked at other cytological stains and concluded that the LIVE⁄DEAD® Viability⁄Cytotoxicity Kit (calcein AM/ethidium homodimer-1) was the most appropriate stain to use with the OSCCA collected cells due to the lack of overlap between stains. Chapter 3 showed that cells that stained with sodium fluorescein stained with only Hoechst and not PI. Since Hoechst stains live and early apoptotic cells and PI stains cells that are late stage apoptotic, necrotic and dead cells, we can conclude that sodium fluorescein stains live and early apoptotic cells. Similarly in chapter 5 it was found that cells that stained with sodium fluorescein stained exclusively with calcein blue AM and not ethidium homodimer-1.