Modeling of the Parathyroid Hormone Response after Calcium Intake in Healthy Subjects

Plasma ionized calcium (Ca2+) concentrations are tightly regulated in the body and maintained within a narrow range; thus it is challenging to quantify calcium absorption under normal physiologic conditions. This study aimed to develop a mechanistic model for the parathyroid hormone (PTH) response after calcium intake and indirectly compare the difference in oral calcium absorption from PTH responses. PTH and Ca2+ concentrations were collected from 24 subjects from a clinical trial performed to evaluate the safety and calcium absorption of Geumjin Thermal Water in comparison with calcium carbonate tablets in healthy subjects. Indirect response models (NONMEM Ver. 7.2.0) were fitted to observed Ca2+ and PTH data, respectively, in a manner that absorbed but unobserved Ca2+ inhibits the secretion of PTH. Without notable changes in Ca2+ levels, PTH responses were modeled and used as a marker for the extent of calcium absorption.

Limbal Relaxing Incision Combined with Cataract Surgery Reducing Preoperative Corneal Astigmatism

PURPOSE: Corneal astigmatic correction is necessary to improve best uncorrected visual acuity (BUVA) after cataract extraction. The purpose of the study is to know the effect and safety of limbal relaxing incision combined with cataract extraction to reduce preoperative astigmatism in patients whose corneal astigmatism was 1.0 diopter or more. METHODS: Eighten eyes from 16 patients had cataract with corneal astigmatism 1.0 diopter or more. We checked preoperative uncorrected visual acuity (UCVA), autokeratometry, manifest refraction, corneal topography and so on. We phacoemulsified and inserted intraocular lens in the bag. After that, we made limbal relaxing incision at the previously-determined axis with previously-determined length and depth. We followed up them with autokeratometry, manifest refraction and corneal topography at 1week, 4, 8 and 12 weeks after surgery. RESULTS: There was a statistically significant improvement of final UCVA transformed by log MAR (minimum angle of resolution) compared with preoperative UCVA. According the analysis of autokeratometric astigmatism with Naeser's polar value concept, astigmatic polar value (AKP) was 1.37+/-0.53 diopter before surgery, .0.17+/-0.30 diopter at 1week after surgery, .0.07+/-0.36 diopter at 4weeks, .0.13+/-0.30 diopter at 8weeks, .0.07+/-0.38 diopter at 12weeks. Over the whole follow-up period, there was a statistically significant decrease of AKP compared with preoperative one (p=0, 0, 0, 0.001). There was also a statistically significant decrease of AKP measured by manifest refraction compared with preoperative ones (p=0.007, 0.001, 0.002, 0.015). There was a statistically significant decrease of AKP checked by corneal topography compared with preoperative ones (p=0.001, 0, 0, 0.002). CONCLUSIONS: Twelve weeks follow up after cataract extraction with limbal relaxing incision showed a statistically significant improvement of final UCVA compared with preoperative UCVA and reduction of preoperative astigmatism checked by autokeratometry, manifest refraction and corneal topography. Limbal relaxing incision combined with cataract extraction was an effective procedure to reduce preoperative astigmatism.

Long-term Follow-up after Trabeculectomy with Mitomycin c

Intraoperative mitomycin c has been popularized for use as an adjuvant to increase the success rate of trabeculectomy because of its antifibroblastic effects. Basically it has a potent antifibroblastic effect and its use presents many potential problems and side effects. As a result, many surgeons concentrate on method to gain the optimal surgical results with the minimal complications with MMC. But the long-term effects of MMC have not been determined because of its short history of clinical applications. So, we evaluated the surgical results and complications of MMC in a long-term follow-up study (more than 30 months) , which was divided into 4 groups by the use of MMC and the high-risk characteristics. A total of 135 eyes were studied. Each group included: A, 40 eyes; B, 17 eyes; C, 52 eyes; D, 26 eyes. Failed filtering surgery and young age were major factors in high-risk groups. In high-risk groups (A, B), the difference in success rates was statistically significant A(M+), 88.5%; B(M-), 52.9% (p=0.010), but in non-high risk groups (C, D), it was not: C(M+), 75%; D(M-), 76.9% (p=0.852). The difference in isual acuity (more than 3 lines in a snellen chart) between each groups was not shown. And in non-high risk groups (C, D), the difference in the hypotony rate was statistically significant C(M+), 21%; D(M-), 49% (p=0.046), but in high-risk groups, it was not: A(M+), 15%; B(M-), 11% (p=0.748). Regardless of the preoperative IOP level, postoperative IOP was less in cases where MMC was used than in cases where MMC was not used. In conclusion, MMC increased the success rate in high-risk groups but it aggravated complications, especially in non-high risk groups. To get optimal results with minimal complications, discreet use of MMC in selected cases is highly recorninended.

Endoscope Assisted Ophthalmic Microsurgery

We would like to introduce endoscope assisted ophthalmic microsurgery. The endoscope system is made of endoscope body, colored moniter, handpiece. The handpiece consists of a 19G or 20G probe housing a fiber optic cable for the camera of a 380.000 pixel resolution, a fiber optic cable for a xenon light source and a working channel. The endoscope was useful to visualize the areas, such as the peripheral retina, posterior side of iris, that were not readily seen by conventional nor wide angle viewing techniques without indentation. Also it gave us good results in the hard visual field cases of corneal opacification or during fluid-gas exchange. using the endoscope permitted the vitreous base to be accurately observed and managed surgically through good visualization of peripheral retina. Intraocular procedure such as vitrectomy, subretinal fluid drainge, endophotocoahulation was performed easily under the endoscopic view, With the improvement of resolution power of the endoscope and the development of stereovision, the range of clinical usage of this technique will be expanded.

The effect of photorefractive keratectomy in Korea

To assess the predictability and accuracy of photorefractive keratectomy (PRK) in myopia, we reviewed the charts of 182 patients who underwent PRK and were followed up for more than 12 months. The mean visual acuity was improved from 0.11 to 0.80 at 12 months postoperatively, and the mean refraction change shows from -7.94D to -0.89D. 47% of the treated eye achieved final visual acuity of 1.0, and 97% achieved 0.5 or better. In the case of postoperative refraction, 96% of cases who were less than -6 D myopia achieved final refraction within +/- 1D, while 66% of cases who were more than -6 D myopia did. These results suggest that PRK is a safe and predictable procedure in treating mild to moderate myopia.