M.C. Cheney

Polarimetric imaging and blood vessel quantification

We applied a polarimetric analysis to retinal imaging, to examine the potential improvement in characterizing blood vessels. To minimize the reflection artifact of the superficial wall of the blood vessel, we computed depolarized light images by removing the polarization retaining light reaching the instrument. These depolarized light images were compared to images from the average of all the light. Michelson contrast was computed for the vessel profiles across arteries and veins, and was higher for the depolarized light images. Depolarized light images provide one step towards improving the characterization of retinal blood vessels.

Imaging polarimetry in patients with neovascular age-related macular degeneration

Imaging polarimetry was used to examine different components of neovascular membranes in age-related macular degeneration. Retinal images were acquired with a scanning laser polarimeter. An innovative pseudocolor scale, based on cardinal directions of color, displayed two types of image information: relative phases and magnitudes of birefringence. Membranes had relative phase changes that did not correspond to anatomical structures in reflectance images. Further, membrane borders in depolarized light images had significantly higher contrasts than those in reflectance images. The retinal birefringence in neovascular membranes indicates optical activity consistent with molecular changes rather than merely geometrical changes.

Imaging polarimetry and retinal blood vessel quantification at the epiretinal membrane

We evaluated a polarimetry method to enhance retinal blood vessels masked by the epiretinal membrane. Depolarized light images were computed by removing the polarization retaining light reaching the instrument and were compared with parallel polarized light images, average reflectance images, and the corresponding images at 514 nm. Contrasts were computed for retinal vessel profiles for arteries and veins. Contrasts were higher in the 514 nm images in normal eyes but higher in the depolarized light image in the eyes with epiretinal membranes. Depolarized light images were useful for examining the retinal vasculature in the presence of retinal disease.

Spatial distribution of macular birefringence associated with the Henle fibers

The spatial distribution of macular birefringence was modeled to examine the contribution from the foveal Henle fiber layer, particularly cone axons. The model was tested in 20 normal subjects, age 17-55yr. Phase retardance due to Henle fibers was modeled for rings increasing in radius around the fovea, using a sinewave of two periods (2f). The 2f sinewave amplitude increased linearly with eccentricity for each individual, (p<0.004) in 19 of 20 subjects. A good fit to linearity implies regular cone distribution and radial symmetry, and the uniformly excellent fits indicate no effect of age in our sample. The peak of the 2f sinewave amplitude varied across subjects from 1.06 to 2.46deg. An increasingly eccentric peak with increasing age would indicate a relative decrease of cone axons in the central fovea, but the location of the peak was not associated with age for our sample, which did not include elderly subjects.

Non-paraxial design for a transportable digital retinal imager

The Scanning Laser Digital Camera (SLDC) is an inexpensive, portable slit scanning laser ophthalmoscope prototype for telemedicine. Stock achromatic lenses increase image quality and contrast over previous biconvex lens designs. Test images show increased resolution and contrast, and reduced aberrations. Normal eye images show an increase in retinal image quality.

The Feasibility, Safety, and Efficacy of Using a Wireless Pedometer to Improve the Activity Level in a Cohort of Nurses:

Purpose: This study had two aims: (1) to test the feasibility, safety, and efficacy of using a wireless pedometer in a cohort of nurses; and (2) to understand if wireless pedometer use increased number of steps walked, number of flights of stairs climbed, daily activity level, and improved personal perception of health. Design: This study used a nonexperimental exploratory design to test the feasibility and efficacy of using a wireless pedometer in a cohort of nurses. Pre- and posttest measures captured the number of steps walked, flights of stairs climbed, activity level, and perception of health. Results: Sample characteristics: 27 females, 3 males; 90% non-Hispanic Caucasian, 3% Hispanic; 47% between the ages of 55 and 65 years. Eighty percent of the participants reported that they were caregivers of other people. There was a significant increase from baseline to the end of the study in the following measures: self-perception of steps walked (p < .001), flights of stairs climbed (p < .005), self-perception of daily activity (p < .001), and although there was an improvement in self-perception of health, the change was not significant. Conclusions: The wireless pedometer was a feasible, safe, and efficacious device to use. This study may have implications for interventions aimed at improving caregiver health.

Imaging with polarization analysis in age-related macular degeneration

Using polarization as a means of separating directly backscattered light from multiply scattered light, images were obtained in patients with exudative eye disease. Different image types revealed strikingly different pathological structures, according to layer.

Transportable digital retinal imager

The Laser Scanning Digital Camera is a battery-operated, transportable device similar to a consumer digital camera designed to provide low cost, high contrast, non-invasive, non-mydriatic imaging of retinal trauma and disease. The prototypes use confocal slit scanning via a cube mirror, separate illumination and imaging paths, and a 2-D detector.