Mobilized by Injustice: Criminal Justice Contact, Political Participation and Race

Thesis (Ph.D.)--University of Washington, 2016-06

Cling film as a barrier against CJD in corneal contact A-scan ultrasonography

Purpose: To determine the validity of covering a corneal contact transducer probe with cling film as protection against the transmission of Creutzfeldt-Jakob disease (CJD). Methods: The anterior chamber depth, lens thickness and vitreous chamber depth of the right eyes of 10 subjects was recorded, under cycloplegia, with and without cling film covering over the transducer probe of a Storz Omega Compu-scan Biometric Ruler. Measurements were repeated on two occasions. Results: Cling film covering did not influence bias or repeatability. Although the 95% limits of agreement between measurements made with and without cling film covering tended to exceed the intrasessional repeatability, they did not exceed the intersessional repeatability of measurements taken without cling film. Conclusions: The results support the use of cling film as a disposable covering for corneal contact A-scan ultrasonography to avoid the risk of spreading CJD from one subject to another. © 2003 The College of Optometrists.

Non-invasive phakometric measurement of corneal and crystalline lens alignment in human eyes

We describe a non-invasive phakometric method for determining corneal axis rotation relative to the visual axis (β) together with crystalline lens axis tilt (α) and decentration (d) relative to the corneal axis. This does not require corneal contact A-scan ultrasonography for the measurement of intraocular surface separations. Theoretical inherent errors of the method, evaluated by ray tracing through schematic eyes incorporating the full range of human ocular component variations, were found to be larger than the measurement errors (β < 0.67°, α < 0.72° and d < 0.08 mm) observed in nine human eyes with known ocular component dimensions. Intersubject variations (mean ± S.D.: β = 6.2 ± 3.4° temporal, α = 0.2 ± 1.8° temporal and d = 0.1 ± 0.1 mm temporal) and repeatability (1.96 × S.D. of difference between repeat readings: β ± 2.0°, α ± 1.8° and d ± 0.2 mm) were studied by measuring the left eyes of 45 subjects (aged 18-42 years, 29 females and 16 males, 15 Caucasians, 29 Indian Asians, one African, refractive error range -7.25 to +1.25 D mean spherical equivalent) on two occasions. © 2005 The College of Optometrists.

Ocular changes and other factors relating to two forms of contact lenses:a comparative study

The work utilising a new material for contact lenses has fallen into three parts: Physioloeical considerations: Since the cornea is devoid of blood vessels, its oxygen is derived from the atmosphere. Early hydrophilic gel contact lenses interrupted the flow of oxygen and corneal insult resulted. Three techniques of fenestration were tried to overcome this problem. High speed drilling with 0.1 mm diameter twist drills. was found to be mechanically successful, but under clinical conditions mucous blockage of the fenestrations occurred. An investigation was made into the amount of oxygen arriving at the corneal interface; related to gel lens thickness. The results indicated an improvement in corneal oxygen as lens thickness was reduced. The mechanism is thought to be a form of mechanical pump. A series of clinical studies con:firmed the experimental work; the use of thin lenses removing the symptoms of corneal hypoxia. Design: The parameters of lens back curvature. lens thickness and lens diameter have been isolated and related to three criteria of vision (a) Visual acuity. (b) Visual stability and (c) Induced astigmatism. From the results achieved a revised and basically successful design of lens has been developed. Comparative study: The developed form of lens was compared with traditional lenses in a controlled survey. Twelve factors were assessed over a twenty week period of wear using a total of eighty four patients. The results of this study indicate that whilst the expected changes were noted with the traditional lens wearers, gel lens wearers showed no discernible change in any of the factors measured. ldth the exception of' one parameter. In addition to a description of' the completed l'iork. further investigations are ·sug~ested l'lhich. it is hoped. l'iould further improve the optical performance of gel lenses.

Visual performance and optical quality with soft lenses in keratoconus patients

Purpose: To assess visual performance and ocular aberrations in keratoconic patients using toric soft contact lenses (SCL), rigid-gas-permeable (RGP) contact lenses and spectacle lens correction. Methods: Twenty-two keratoconus patients (16 RGP lens wearers and six spectacle wearers) were fitted with toric SCL. Ocular aberrations were measured with and without the patient's habitual RGP lenses and with the SCL in place. In the spectacle wearers, aberrations were measured with and without the SCL. Visual performance (high- and low-contrast visual acuity) was evaluated with the patient's habitual correction and with the SCL. Results: In the RGP lens wearers both the habitual lenses and the toric SCL significantly reduced coma, trefoil, 3rd-order, 4th-order cylinder and higher-order root-mean-square (RMS) aberrations (p≤0.015). In the spectacle wearers the toric SCL significantly reduced coma, 3rd-order and higher-order RMS aberrations (p≤0.01). The patients' habitual RGP lenses gave better low-contrast acuity (p≤0.006) compared to the toric SCL; however, no significant difference was found between lens types for high-contrast acuity (p=0.10). In the spectacle wearers no significant differences in visual performance measurements were found between the patients' spectacles and the toric SCL (p≥0.06). Conclusion: The results show that RGP lenses provided superior visual performances and greater reduction of 3rd-order aberrations compared to toric SCL in this group of keratoconic patients. In the spectacle-wearing group, visual performance with the toric SCL was found to be comparable to that measured with spectacles. Nevertheless, with the exception of spherical aberration, the toric SCL were successful in significantly reducing uncorrected higher-order aberrations. Ophthalmic & Physiological Optics © 2012 The College of Optometrists.

Accommodation in young adults wearing multifocal soft contact lenses under long- and short- wavelength lighting

Purpose: Several studies have suggested accommodative lags may serve as a stimulus for myopic growth, and while a blurred foveal image is believed to the main stimulus for accommodation, spectral composition of the retinal image is also believed to influence accommodative accuracy. Of particular interest is how altering spectral lighting conditions influences accommodation in the presence of soft multifocal contact lenses, which are currently being used off-label for myopia control. Methods: Accommodative responses were assessed using a Grand Seiko WAM-5500 autorefractor for four target distances: 25, 33, 50, and 100cm for 30 young adult subjects (14 myopic, 16 emmetropic; mean refractive errors (±SD, D) -4.22±2.04 and -0.15±0.67 respectively). Measurements were obtained with four different soft contact lenses, Single vision distance (SVD), Single vision near (SVN), Centre-Near (CN) and Centre-Distance (CD) (+1.50 add), and three different lighting conditions: red (peak λ 632nm), blue (peak λ 460nm), and white (peak λ 560nm). Corrections for chromatic differences in refraction were made prior to calculating accommodative errors. Results: The size of accommodative errors was significantly affected by lens design (p<0.001), lighting (p=0.027), and target distance (p=0.009). Mean accommodative errors were significantly larger with the SV lenses compared to the CD and CN designs (p<0.001). Errors were also significantly larger under blue light compared to white (p=0.004) and a significant interaction noted between lens design and lighting (p<0.001). Blue light generally decreased accommodative lags and increased accommodative leads relative to white and red light, the opposite was true of red light (p≤0.001). Lens design also significantly influenced direction of accommodative error (i.e. lag or lead) (p<0.001). Interactions with or between refractive groups were not found to be statistically significant for either the magnitude or direction of accommodative error (p>0.05 for all). Conclusions: Accuracy of accommodation is affected by both lens design and by wavelength of lighting. These accommodative lag data lend some support to recent speculation about the potential therapeutic value of lighting with a spectral bias towards blue during near work for myopia, although such treatment effects are likely to be more subtle under broad compared to the narrow spectrum lighting conditions used here.

In vitro and in vivo delivery of the secretagogue diadenosine tetraphosphate from conventional and silicone hydrogel soft contact lenses

Purpose To evaluate the possible use of soft contact lenses (CL) to improve the secretagogue role of diadenosine tetraphosphate (Ap4A) promoting tear secretion. Methods Two conventional hydrogel CL (Omafilcon A and Ocufilcon D) and two silicone hydrogel (SiH) CL (Comfilcon A and Balafilcon A) were used. Ap4A was loaded into the lenses by soaking in a 1 mM Ap4A solution during 12 h. In vitro experiments were performed by placing the lenses in multi-wells during 2 h containing 1 ml of ultrapure water. 100 μl aliquots were taken at time zero and every minute for the first 10 min, and then every 15 min. In vivo experiments were performed in New Zealand rabbits and both the dinucleotide release from SiH and tear secretion were measured by means of Schirmer strips and high-pressure liquid chromatography (HPLC) analysis. Results Ap4A in vitro release experiments in hydrogel CL presented a release time 50 (RT50) of 3.9 ± 0.2 min and 3.1 ± 0.1 min for the non-ionic and the ionic CL, respectively. SiH CL released also Ap4A with RT50 values of 5.1 ± 0.1 min for the non-ionic and 2.7 ± 0.1 min for the ionic CL. In vivo experiments with SiH CL showed RT50 values of 9.3 ± 0.2 min and 8.5 ± 0.2 min for the non-ionic and the ionic respectively. The non-ionic lens Ap4A release was able to induce tear secretion above baseline tear levels for almost 360 min. Conclusion The delivery of Ap4A is slower and the effect lasts longer with non-ionic lenses than ionic lenses.

An investigation of contact transmission of methicillin-resistant staphylococcus aureus

Hand hygiene is critical in the healthcare setting and it is believed that methicillin-resistant Staphylococcus aureus (MRSA), for example, is transmitted from patient to patient largely via the hands of health professionals. A study has been carried out at a large teaching hospital to estimate how often the gloves of a healthcare worker are contaminated with MRSA after contact with a colonized patient. The effectiveness of handwashing procedures to decontaminate the health professionals' hands was also investigated, together with how well different healthcare professional groups complied with handwashing procedures. The study showed that about 17% (9–25%) of contacts between a healthcare worker and a MRSA-colonized patient results in transmission of MRSA from a patient to the gloves of a healthcare worker. Different health professional groups have different rates of compliance with infection control procedures. Non-contact staff (cleaners, food services) had the shortest handwashing times. In this study, glove use compliance rates were 75% or above in all healthcare worker groups except doctors whose compliance was only 27%.