Yvonne Wang

Corneal Nerve Structure and Function After Long-Term Wear of Fluid-Filled Scleral Lens

Purpose: The aim of this study was to determine whether long-term wear of a fluid-filled scleral lens alters basal tear production, corneal sensation, corneal nerve density, and corneal nerve morphology in 2 disease categories. Methods: Patients recruited from the Prosthetic Replacement of the Ocular Surface Ecosystem (PROSE) treatment program at the Weill Cornell Medical College were categorized into 2 groups: distorted corneas (DC) or ocular surface disease (OSD). We measured tear production, central corneal sensation, subbasal nerve density and tortuosity, and stromal nerve thickness before and after long-term wear of the prosthetic device used in PROSE treatment, defined as at least 60 days of wear for a minimum of 8 hours a day. Results: Twenty patients were included in the study. After long-term wear of the prosthetic device, tear production decreased in patients with DC (21.2 ± 8.5 to 10.4 ± 4.6 mm; P < 0.0001) but did not change in patients with OSD (7.5 ± 5.2 to 8.7 ± 7.2 mm; P = 0.71). Corneal sensation increased in the DC group (45.6 ± 9.2 to 55.0 ± 5.6 mm; P < 0.05). There was no significant change in sensation in patients with OSD (45.0 ± 8.7 to 49.1 ± 14.8 mm; P = 0.37). Subbasal nerve density, subbasal nerve tortuosity, and stromal nerve thickness remained unchanged in both DC and OSD groups after long-term wear (P > 0.05). Conclusions: Patients with DC had significantly reduced basal tear production and increased corneal sensation after long-term wear of the scleral lens, but patients with OSD did not show any changes in tear production or corneal sensation.

Diffusivity measurements in polymers: III. Quartz crystal microbalance techniques

A quartz crystal microbalance (QCM) system has been designed and constructed in order to measure the diffusion rates of several different casting solvents in a photoresist film. The QCM employs an oscillating quartz crystal that is coated with a photoresist film. Changes in mass caused by sorption or desorption of the casting solvent are detected as changes in the resonant frequency of the crystal. One advantage of the QCM is the high sensitivity with which this device can make weight measurements. The sensitivity is on the order of nanograms. This accuracy, along with the ease of data analysis, makes the QCM a particularly attractive apparatus for diffusion measurements. The QCM system consists of a piezoelectric crystal, a frequency counter, an oscillator unit, a detector, and a recorder. During the experiment, the shift in resonant frequency of the crystal with time is monitored, and the diffusion coefficient is extracted by using the method described by Crank. A related QCM technique has been used to study the dissolution kinetics of photoresists. The QCM system has been employed to measure the diffusion coefficients of common casting solvents in novolac films as a function of temperature. Acid diffusion in poly(hydroxystyrene) was also studied by this method.

Thick polysilicon surface-micromachined optically sensed accelerometer

An accelerometer based on optical intensity modulation has been designed and fabricated using thick-polysilicon (12 micrometer) surface-micromachining technology. A layer of polysilicon is surface micromachined to form a grating connected to springs, which are anchored on the silicon substrate. A layer of metal is evaporated on the top of the entire device making the suspended grating opaque as well as the regions on the substrate that are exposed by the grating. This leaves the areas directly beneath the grating shadowed from incident light. In the unperturbed state, the light that shines on the device is completely reflected by the metal on top of the entire device. When the grating moves under the influence of acceleration, the areas which are not covered by the metal are then exposed and the amount of light passing through the substrate increases. The optical intensity variation translates to the acceleration experienced by the grating proof mass. Twelve micrometer thick polysilicon surface micromachining was developed to improve the performance of the device. The films mechanical qualities, internal stain, stress gradient and surface roughness have been characterized. This optical accelerometer has a sensitivity of 70 milli-g with 0.5-micron movement.

Dermatomyositis-Related Nonischemic Central Retinal Vein Occlusion.

A 25-year-old woman with dermatomyositis suffered a right central retinal vein occlusion (CRVO) with visual acuity of 20/40. Examination of the right eye showed vitreous cells, suggesting inflammation of the central retinal vein leading to a CRVO as the presumed mechanism. She was admitted to hospital, and extensive evaluation was negative. She was maintained on corticosteroids to manage her dermatomyositis. One month later, she had macular edema and elevated intraocular pressure. Both resolved with dorzolamide, timolol, and intravitreal bevacizumab, and vision returned to 20/20 in the right eye.