Judie F. Charlton

Ocular disposition of nanoencapsulated acyclovir and ganciclovir via intravitreal injection in rabbit's eye

AbstractGanciclovir nanoparticles were prepared using biodegradable polymers to evaluate a possible treatment for cytomegalovirus (CMV) retinitis. Bovine serum albumin (BSA), polyethylcyanoacrylate (PEC), and chitosan were utilized as drug carriers. The three products were evaluated for drug-loading capacity, particle size, and drug release. Spherical nanoparticles ranging between 0.3 and 1.2 μm in diameter were obtained, with those of PEC being the smallest. Loading capacity was in the range of 62.5–66.9%. Drug release studies revealed decreasing release rates in the following order: BSA > PEC ≥ chitosan. PEC nanoparticles containing ganciclovir (measured spectrophotometrically) and radioactive acyclovir (measured by liquid scintillation) showed essentially the same release patterns. The PEC nanoparticles containing [3H]acyclovir and ganciclovir together were selected for in vivo drug level studies. Following an intravitreal injection in rabbit eyes, drug levels in different eye tissues were used to comp...

TEAR HYPEROSMOLARITY IN RENAL DIALYSIS PATIENTS ASYMPTOMATIC FOR DRY EYE

Renal dialysis patients have hyperosmolar bodily fluids due to high urea levels, and accordingly their tears should be hyperosmolar. Tear hyperosmolarity is a sensitive and specific test for dry eye. The purpose of this study was to determine whether renal dialysis patients have hyperosmolar tears and dry eye. Ten renal dialysis patients completed the McMonnies and Ho dry eye questionnaire and underwent tear osmolarity testing before dialysis. Serum osmolarity was calculated from serum sodium, potassium, and blood urea nitrogen levels. Half of the subjects also participated in tear osmolarity testing after dialysis and underwent an eye examination that included rose bengal and fluorescein staining, Schirmers testing, and tear break-up time testing. All of the subjects had both hyperosmolar serum and tears, and tear osmolarities were positive for dry eye in all subjects. However, none of the subjects tested positively for dry eye with the questionnaire. The subjects had some physical findings consistent with dry eye, and Schirmers testing showed decreased tear production. Renal dialysis patients are a population that have hyperosmolar tears yet remain asymptomatic for dry eye. Urea has been used for years as a dermatologic treatment for dry skin. The high levels of urea in the tears of dialysis patients may protect them from developing dry eye. Tear hyperosmolarity due specifically to ionized solutes such as sodium and potassium is probably more pathogenic in causing dry eye than is hyperosmolarity in general. Nevertheless, tear osmolarity testing should not be used as a dry eye monitor in renal failure patients.

The "lost lens": a new surgical technique using the Machemer lens.

We describe a method of removing a posteriorly dislocated lens involving the use of a Machemer lens to visualize displaced lens remnants. Following core vitrectomy, the lens remnants are brought anteriorly and then removed by phacoemulsification. Lens implantation may then be performed with sulcus fixation. Eight of 10 patients in which this technique was used achieved 20/40 or better visual acuity.

Detecting glaucomatous damage: evaluation with contrast independent tasks

Several studies have indicated that contrast-dependent tasks, such as detecting threshold stimuli, may be more effective in discriminating glaucoma from normal groups if external noise is added to the stimulus. We sought to determine if the same were true for contrast-independent tasks. Subjects were 15 patients with glaucoma and a group of 20 normals with the same mean age. We employed two contrast-independent tasks, orientation defined texture and dot numerosity discrimination. The stimulus was presented on a computer controlled video monitor. One side of the display contained a standard and the other contained a non-standard target. For each task, noise was added by perturbing the main feature of the display, dot number or line orientation, by a Gaussian distribution truncated at 2 standard deviation units. There were four noise levels for each task. Subjects viewed the stimulus display and made a spatial two-alternative forced choice judgment. Subjects judged the side of the orientation texture which contained a sub-region with a different angle and the side of the dot figures which had the larger number of dots. Glaucoma patients performed more poorly than normals in discriminating the orientation texture (p < 0.05) and in judging dot numerosity (p < 0.05). This was true even in the absence of added external noise. Adding external noise did not increase the differences between glaucoma patients and normals. Unlike contrast-dependent tasks in which the differences between normal and glaucoma patients are increased when external noise is added, contrast-independent tasks show maximal differentiation between the two groups without added noise. Tasks such as texture discrimination and dot numerosity may be useful in detecting glaucoma.