Corneal flap displacement and drift in LASIK: comparison of Hansatome and Automated Corneal Shaper microkeratomes

PURPOSE: To describe and compare the displacement of corneal flaps created during laser in situ keratomileusis (LASIK) procedures performed with two different microkeratomes and analyze parameters (for example, pupil-to-hinge distance, drift during suction) that might affect the flap displacement or be influenced by flap displacement. DESIGN: This work was based on a cross-sectional study design. METHODS: Images copied from video recordings of 206 consecutive LASIK surgeries were analyzed to determine the distance from pupil center to corneal flap hinge (pupil-to-hinge distance), the hinge size, the distance from the center of the pupil to the margins of the flap, and the positions of the suction ring before and after vacuum in corneal flaps created by the Hansatome and the Automated Corneal Shaper (ACS) microkeratomes. Accurate measurements of all these variables could be obtained in 121 eyes (Hansatome: n = 66, right eye (OD) = 27 eyes, left eye (OS) = 39 eyes; ACS: n = 55, OD = 25 eyes, OS = 30 eyes), which were included in the analysis. Formulas were derived to calculate from the measurements the magnitude and direction of the drift of the suction ring during vacuum and the final displacement of the corneal flap. RESULTS: The mean +/- standard deviation (SD) drift of eyes during suction with the Hansatome was 0.27 +/- 0.02 mm and with the ACS was 0.12 +/- 0.02 mm (P <.001). The Hansatome induced, on average, more biased (temporal vs random) drift than did the ACS. The mean final displacement of the center of the flap from the center of the pupil was of equal magnitude for the two instruments (0.37 +/- 0.02 mm and 0.36 +/- 0.02 mm with the Hansatome and ACS, respectively). CONCLUSION: The drift induced by the Hansatome contributes to the horizontal component of the final decentration of the corneal flaps. This tendency for drift and the resultant decrease in pupil-to-hinge distance should be considered to minimize flap displacements during LASIK.     

Human corneal epithelial cell viability and morphology after dilute alcohol exposure

PURPOSE: To determine the effect of dilute alcohol on human corneal epithelial cellular morphology and viability. Dilute alcohol is used for epithelial removal during photorefractive keratectomy (PRK) and laser subepithelial keratomileusis (LASEK). METHODS: Corneal epithelial sheets harvested from human eyes after alcohol application during PRK were examined by light and electron microscopy (specimens I-IV). In addition, tissue cultures of human epithelial sheets were monitored for epithelial migration and attachment (specimens V-VII). To determine the effect of dilute alcohol on epithelial cell viability, simian virus (SV)40-immortalized human corneal epithelial cells were exposed to dilute alcohol in distilled water (EtOH-H2O) or to keratinocyte serum-free medium (EtOH-KSFM) for incubation periods of 20 to 45 seconds and concentrations of 10% to 70%. Cell membrane permeability and intracellular esterase activity were analyzed by calcein-acetoxymethyl ester (AM)/ethidium homodimer assay. TdT-mediated dUTP nick-end labeling (TUNEL) assay was used to detect apoptotic cells at 0, 8,12, 24, and 72 hours. RESULTS: Electron microscopy showed varying degrees of basement membrane alterations after alcohol application, including disruptions, discontinuities, irregularities, and duplication (specimens I-IV). Cellular destruction and vacuolization of basal epithelial cells associated with absent basement membrane were also observed (specimen III). One of three cultured epithelial sheets showed attachment and outgrowth in the tissue culture until day 15 (specimen V). Twenty-second exposure of cultured immortalized human cells to various concentrations of EtOH-H2O showed significant reduction of viable cells when EtOH-H2O concentration exceeded 25% (P = 0.005). Increasing the duration of application of 20% EtOH-H2O beyond 30 seconds resulted in a significant reduction in viable cells (69.69% +/- 16.34% at 30 seconds compared with 2.14% +/- 2.29%, 10.45% +/- 7.11%, and 11.09% +/- 15.73% at 35, 40, and 45 seconds, respectively; P = 0.01). TUNEL assay of cultured human corneal epithelial cells exposed to 20% EtOH-H(2)O for 20 and 40 seconds showed maximal labeling at 24 hours (58.05% +/- 33.10%) and 8 hours (94.12% +/- 1.21%), respectively. Exposure to 20% EtOH-KSFM for 20 and 40 seconds resulted in substantially lower TUNEL positivity (3.51% +/- 0.20% at 24 hours and 7.11% +/- 0.49% at 8 hours). CONCLUSIONS: The viability and electron microscopic findings in the basement membrane zone showed significant variation after treatment of the epithelium in vivo with dilute alcohol. The application of dilute alcohol on the monolayer of cultured corneal epithelial cells resulted in increasing cell death in a dose- and time-dependent manner.     

Contribution of ionotropic glutamate receptors and voltage-dependent calcium channels to the potentiation phenomenon induced by transient pentylenetetrazol in the CA1 region of rat hippocampal slices

The role of ionotropic glutamate receptors and voltage-dependent calcium channels (VDCCs) in potentiation phenomenon and epileptic activity induced by a transient pentylenetetrazol (PTZ) application in the CA1 region of rat hippocampal slices was investigated. Also we examined whether adenosine as an inhibitory neuromodulator would interact with expression of the long-lasting effect of transient PTZ. Population spikes (PS) were recorded in the CA1 cell body layer of the hippocampal slices following stratum radiatum stimulation. Changes in the PS amplitude potentiation and number of extra PS, which induced by transient PTZ were used as indices to quantify the effects of drugs. PS input-output curve was significantly increased 10 min after PTZ application and persisted at least for 60 min after PTZ washout. Polyspikes also appeared, but did not persist. Both ketamine and APV reduced the extent of potentiation of PS amplitude but had no effect on number of extra PS. The selective non-NMDA receptor antagonist CNQX prevented the amplitude potentiation and the generation of extra PS. The blocker of VDCCs, verapamil, prevented the amplitude potentiation and inhibited polyspike activity. Co-application of adenosine and PTZ produced a rapid and reversible decrease in the PS amplitude, but PTZ-induced potentiation phenomenon was observed after washout. It is concluded that ionotropic glutamate receptors as well as VDCCs involve in the PTZ-induced LTP of PS amplitude. PTZ-induced LTP is also insensitive to adenosine. The epileptiform activity induced by a transient PTZ application could be attributed to VDCCs. The polyspikes mediated by VDCCs are dependent on prior activation of AMPA receptors.     

Severe cholestatic hepatitis caused by thiazolidinediones: risks associated with substituting rosiglitazone for troglitazone

Troglitazone maleate (Rezulin) has been associated with severe hepatotoxicity, which led to its withdrawal from the U.S. market in March 2000. Rosiglitazone maleate (Avandia) is being marketed as a safe alternative in the treatment of type 2 diabetes mellitus. We report a case of severe thiazolidinedione-induced cholestatic hepatitis in a 56-year-old female patient at a university hospital who was given rosiglitazone, 8 mg/day, after she developed milder hepatotoxicity while taking troglitazone. Rosiglitazone was discontinued, and the patient was treated with prednisone, azathioprine, and ursodiol. Clinical evaluation and liver biopsy were performed and liver function tests were monitored. After being switched from troglitazone to rosiglitazone the patient developed a severe cholestatic hepatitis with marked jaundice and moderate increases in serum alkaline phosphatase and -glutamyltranspeptidase but only mild increases in serum aminotransferases. Discontinuation of rosiglitazone and treatment with prednisone, azathioprine, and ursodiol led to improvement, albeit with residual injury, dropout of intrahepatic bile ducts, and persisting elevations of serum alkaline phosphatase. Rosiglitazone is not always a safe alternative in patients who have had hepatotoxicity to troglitazone. It is important to monitor the serum alkaline phosphatase in addition to the serum aminotransferases in patients taking thiazolidinediones.     

Delayed onset of uveitis in TINU syndrome

We report here the clinical features and outcomes of two patients who presented idiopathic tubulo-interstitial nephritis and uveitis syndrome (TINU syndrome) with ocular disease following the onset of nephropathy. The initial symptoms were renal impairment with asthenia, anorexia and weight loss. An increase in urinary beta2-microglobulin was noticed at the initial checkup in both patients. Renal biopsies showed interstitial cellular infiltration without granulomas or tubular atrophy. No glomerular and vascular alterations were seen and immunofluorescent staining was uniformly negative. Systemic steroid therapy was given and renal function returned to normal within three months. Anterior uveitis occurred in both patients eight months later and responded well to local steroid therapy. Renal involvement in TINU syndrome mostly has a favorable outcome. Despite the possibility of spontaneous regression, systemic steroids may be beneficial in reducing the development of interstitial fibrosis.     

Association of first-trimester maternal lipid profiles and triglyceride-glucose index with the risk of gestational diabetes mellitus and large for gestational age newborn

Objective: To evaluate the association of maternal first-trimester plasma lipid profiles, fasting plasma glucose (FPG), and triglyceride (TyG) index with the risk of gestational diabetes mellitus (GDM) and large for gestational age (LGA) infant in Iranian mothers.

Methods: Nine hundred and fifty-four healthy pregnant women were prospectively followed till after delivery. Maternal fasting lipids and glucose concentration were measured at nine-week gestation on average. We used generalized linear models to calculate the relative risks and 95% confidence intervals.

Results: The incidence of GDM and LGA infants among our participants was 18.4% and 26.1%, respectively. There was a significant correlation between the increase in FPG, triglyceride, TG/HDL-C ratio, as well as TyG index with the risk of GDM and LGA infant. After adjusting for potential confounders, the relative risk of GDM in women in the top tertile of FPG, triglyceride (TG), triglyceride/high-density lipoprotein-cholesterol (TG/HDL-C) and TyG index was 4.2-, 4.2-, 3.9-, and 4.9-folds of its risk in women in the bottom tertile, respectively. Also after adjusting for GDM, the relative risk of LGA infants in women in the top tertile of FPG, TG, TG/HDL-C ratio and TyG index was 3.9-, 4.3-, 4.8-, and 5.3-folds of its risk in women in the bottom tertile, respectively.

Conclusions: Based on our findings, TyG index is more robust early predictors of GDM and LGA in Iranian women.     

The use of ketamine for abdominal tubal ligation

A study was made of ketamine hydrochloride's effectiveness in decreasing viseral pain in 50 patients undergoing postpartum abdominal tubal ligation, a procedure involving visceral pain but not requiring muscular relaxation. Patients were pre-medicated and ketamine was administered (10 mg/ml intravenously) until the patient no longer responded to surgical stimulae. The majority of patients (39) required 1 mg/kg of ketamine for induction and repeated doses of 20 mg each, every 5 minutes, for maintenance (31 patients). Analgesic effectiveness was judged on the following basis: Good - no movement or phonation during surgery (74 percent); Fair - slight limb movement or occasional phonation (20 percent); Poor - gross movement or loud phonation (6 percent). On the average blood pressure rose 14 percent, heart rate 21 percent, and respiratory rate 34 percent. Some dizziness was experienced by all patients. Alveolar-arterial oxygen difference was increased in several cases; possibly due to increase in right-to-left pulmonary blood shunt. Ketamine was found to be an adequate anaesthetic in 94% of patients with administered doses well below recommended amounts.