Biomedical subjects

C W Yau

Publications and source records attributed to C W Yau.

8 recordsLinked to original sources

PubMed1993

Apoplectic optochiasmal syndrome due to intrinsic cavernous hemangioma. Case report.

A 42-year-old man suffered from acute evolving visual loss after drinking alcohol. Consecutive visual field changes suggested a mass within the left optic nerve extending its compression across the chiasm and encroaching on the left optic tract. Computed tomography scanning and magnetic resonance imaging confirmed the presence of an overt hemorrhage, a real apoplectic event of cavernous hemangioma. Cavernous hemangiomas located within the intracranial optic nerve are few. Occult hemorrhage within the confines of the intrinsic vascular tumor resulted in acute visual changes in most reported cases. Overt hemorrhage with blood extravasation beyond the original confines of the intrinsic optochiasmal tumor are rarely reported in the literature. Herein, we report one such case. The clinical course and the predisposing factors are also discussed.

Adult↗

PubMed1991

Kahn's wire passer used in medial canthal tendon fixation.

The history of fixation of the medial canthal structures is one of gradual improvement in instrumentation and technique. Today, open reduction and internal fixation remain the mainstay of treatment for the medial canthal structures. With regard to the internal fixation method, we have developed a wire passer that can facilitate wire fixation of the delicate medial canthal tendon. We present two cases that manifest abnormalities of the medial canthal tendon. Both were corrected successfully with this wire passer.

Adult↗

PubMed1986

Ocular concentration of gentamicin after penetrating keratoplasty.

To determine if the storage of corneal tissue in a preserving medium containing gentamicin results in therapeutically effective concentrations of antibiotics in the ocular tissues after penetrating keratoplasty, we stored rabbit donor corneas in McCarey-Kaufman medium containing 100 micrograms of gentamicin per milliliter for three days before surgery. Gentamicin concentrations were determined by agar-diffusion bioassay in ocular tissues one, two, three, four, and six hours after surgery. On the average, the concentration of antibiotic one hour after surgery was 8.8 micrograms of gentamicin per gram of donor cornea, 6.25 micrograms of gentamicin per milliliter of iris, and 2.8 micrograms of gentamicin per milliliter of aqueous humor. The minimal inhibitory concentration for sensitive strains of Pseudomonas aeruginosa is 1.6 micrograms of gentamicin per milliliter of medium. Thus, gentamicin levels sufficient to inhibit the growth of sensitive bacteria were still present in the donor cornea three hours and in the iris two hours after penetrating keratoplasty. By six hours, only trace amounts of gentamicin were found in the donor cornea and aqueous humor. The presence of gentamicin in ocular tissues after penetrating keratoplasty appears to prolong the antibacterial effect of the preserving medium, and to provide tissue concentrations of antibiotic effective against intraoperative contamination.

Animals↗

PubMed1986

Antibacterial effect of donor corneas stored in gentamicin-enriched McCarey-Kaufman medium.

Penetrating keratoplasty was performed on five pairs of rabbit eyes; one eye of each animal received a donor cornea stored in McCarey-Kaufman (M-K) medium containing gentamicin, and the contralateral eye received a donor cornea stored in M-K medium without gentamicin. At the end of surgery, dilutions of Pseudomonas aeruginosa were introduced into the anterior chamber of both eyes. The eyes receiving gentamicin-enriched corneas showed mild to moderate infection; the contralateral eyes showed significantly more severe infection. The results indicated that donor corneas stored in gentamicin-enriched M-K medium inhibit the growth of bacteria acquired at the time of surgery and thus may improve the safety of such transplantation procedures.

Animals↗

PubMed1986

A medium-term corneal preserving medium (K-Sol).

A new corneal preserving solution, K-Sol, was prepared by combining TC 199, 100 mg/L of gentamicin sulfate, 0.025M HEPES buffer to a pH of 7.4, and various concentrations (2.0%; 2.25%; 2.5%) of chondroitin sulfate to a final osmolality of 310 mOsm. Rabbit corneas stored at 4 degrees C for 12 days in each solution, as well as fresh controls, were used for penetrating keratoplasty. Three weeks later, one graft in the 2.0% group was opacified; the rest were clear and showed minimal thickening. There were no significant differences between controls in terms of pachymetry and endothelial cell loss. This study supports the finding that K-Sol with 2.5% chondroitin sulfate is a simple, effective, medium-term preserving solution for donor tissue for penetrating keratoplasty in rabbits.

Animals↗

PubMed1986

The effect of changes in intraocular pressure on corneal curvature after radial keratotomy in the rabbit eye.

Standard radial keratotomy was performed in both eyes of 18 rabbits. Intraocular pressure (IOP) was raised by injection of saline solution into the vitreous cavity at different times after surgery: 8 eyes at one, two, and six weeks and 12 eyes at four months. Keratometric readings at 10, 20, 40, 60, and 80 mmHg were recorded by three independent observers in a masked fashion. The same procedure was performed in eight eyes that had no surgery, as controls. Increments in IOP correlated with significant reductions in corneal power at all times after surgery and for all IOP values in the operated eyes. No changes were observed in the control eyes. The results indicate that variations in IOP, even within physiological limits, may cause changes in corneal curvature after radial keratotomy, and that patients with wide fluctuations in IOP could present a higher risk for postoperative fluctuation in visual acuity after this refractive procedure.

Animals↗

PubMed1986

Comparison of K-Sol and M-K medium for cornea storage: results of penetrating keratoplasty in rabbits.

Five pairs of rabbit corneas were stored for two weeks at 4 degrees C, one of each pair in K-Sol medium, and one in McCarey-/Kaufman (M-K) medium. After transplantation all penetrating keratoplasty grafts became clear and thin. Endothelial cell loss was significantly less in the K-Sol stored corneas. Another five pairs of corneas were stored for two weeks in K-Sol or three days in M-K medium. After penetrating keratoplasty there were no significant differences in clarity, thickness, or endothelial cell loss. The results indicate that K-Sol provides satisfactory medium-term corneal storage compared with short-term storage in M-K medium at refrigerator temperatures.

Animals↗

PubMed1986

The effect of collagen cross-linkage inhibitors on rabbit corneas after radial keratotomy.

The inhibition of collagen cross-linkage by beta-aminopropionitrile (BAPN) and D-penicillamine was tested in an attempt to enhance the myopic correction achieved by radial keratotomy. Two groups of six rabbits each underwent radial keratotomy in both eyes; one eye of each rabbit was treated with BAPN (33% in white petrolatum) or D-penicillamine (1.5 M in sterile water) three times a day for 6 weeks, while the other eye received only vehicle. In spite of previous reports of positive results with BAPN, neither BAPN nor penicillamine was found to affect keratometry readings or corneal topography after radial keratotomy. Our results suggest that factors other than collagen cross-linkage exert major influences in determining the outcome of this refractive procedure.

Aminopropionitrile↗