Chul Hong

Reduction in intraocular pressure after laser in situ keratomileusis.

Purpose: To investigate whether intraocular pressure (IOP) measured on the nasal side is affected after laser in situ keratomileusis (LASIK). Setting: The Glaucoma Service, Dr. Hongs Eye Clinic, Seoul, Korea. Methods: In 83 patients, IOP was prospectively measured with the Goldmann tonometer at the central (Tcenter) and nasal (Tnasal) areas of the cornea before and after LASIK. The Tcenter and Tnasal IOP between baseline and 1, 3, and 6 months postoperatively was compared. The correlation between ablation depth, amount of treatment, refractive change, and change in central corneal thickness and Tcenter change was evaluated. Results: Six months after LASIK, Tcenter IOP decreased 3.9 mm Hg (25.2%) and Tnasal IOP decreased 2.0 mm Hg (12.7%) (P < .001, P = .02, respectively). The Tnasal measurement was 1.8 mm Hg higher than the Tcenter measurement (P < .001). Significant correlation between each corneal parameter and the Tcenter reduction at 1 month did not continue to 6 months (P gt; .05). Conclusion: At each follow‐up, Tnasal IOP was statistically lower than at baseline, although the reduction was not as great as that of Tcenter IOP. A 2 to 3 mm Hg drop in Tnasal up to 6 months after LASIK should be expected. An alternative would be to measure IOP with the Tono‐Pen® on the nasal side to fit the tip to the relatively unchanged nasal side of the cornea.

A partial assumed strain formulation for triangular solid shell element

Abstract An assumed strain formulation is based on the Hellinger–Reissner variational principle with two unknown fields; assumed displacements and independently assumed strains. It is effective to alleviate locking without triggering undesirable spurious kinematic modes if proper assumed strain field is carefully selected in the formulation. Since C 0 continuity does not require strains continuous across the element boundaries, the assumed strain field can be eliminated at an element level. However, elimination of the assumed strain field requires more operations including matrix inverse, where matrix size depends on the number of assumed strain parameters, at each element to obtain an element stiffness matrix. Therefore, small number of assumed strain parameters saves computation time. In this study a triangular solid element based on a partial assumed strain formulation is presented. The assumed strain field is divided into in-plane part and transverse part in the formulation. The transverse part of the assumed strain field is independently assumed to alleviate transverse shear locking. However, the in-plane part of the assumed strain field is replaced by displacement-dependent strain, which reduces the number of assumed strain parameters. Since the number of assumed strain parameters of the formulation is smaller than the conventional assumed strain formulation, the present formulation saves computation time for constructing stiffness matrix without sacrificing accuracy.

Effects of postoperative mitomycin C on glaucoma filtration surgery in rabbits treated preoperatively with antiglaucoma medications

In a rabbit model, we evaluated the effects of topically applied postoperative mitomycin C (MMC) on the success rate of glaucoma filtration surgery in animals treated preoperatively with pilocarpine hydrochloride 4% and levobunolol hydrochloride (Betagan) for 16 weeks. Full-thickness filtration surgery was performed with a single 5-minute intraoperative exposure to a sponge soaked with 0.4 mg/mL MMC of one eye in nine rabbits in one group (group A) and to both eyes in 13 rabbits in a second group (group B). In addition, one eye of each rabbit in group B received a daily drop of 0.4 mg/mL MMC for 13 days after the operation. All of the eyes were then followed for 80 days. The intraoperatively applied MMC enhanced the success rate of the filtration surgery in the group A eyes. However, the eyes that also received postoperative drops of MMC (group B) had longer periods of reduced intraocular pressure (IOP) (P [chi-squared = 5.94] < .025), fewer bleb failures (P [chi-squared = 8.09] < .005), and more complications than the eyes that received only intraoperative MMC.