Incidence and causes of retreatments after monovision induced by LASIK in myopic patients without a previous trial of contact lens induced monovision

PURPOSE

To evaluate the incidence and causes of the need for retreatment after LASIK-induced monovision in patients with myopia and presbyopia without a previous trial of contact lens induced monovision.

DESIGN

Retrospective, observational study.

METHODS

We retrospectively studied 914 eyes of 457 consecutive myopic patients with presbyopia scheduled for LASIK-induced monovision (nondominant eye corrected for near). The dominant eye was identified by the finger pointing test and the treatment plan for the nondominant eye ranged from -0.50 to -1.50 diopters based on an age-related nomogram. We evaluated the incidence of enhancements and the causes at 6 months postoperatively. Patients were divided into three groups based on age to evaluate possible differences in the reasons for retreatment among the age groups.

RESULTS

The global enhancement rate was 15,8% (144/914 eyes). The incidence of retreatment was significantly higher in the dominant eye (8,6%) than in the nondominant eye (7,1%) (P = .01). The enhancement rate in the nondominant eye were conversion to full distance (8,8% of patients), induction of more monovision (3,2% of patients) and reduction of anisometropia (1,1% of patients). More young patients (aged 40-45 years) wanted to reverse the procedure.

CONCLUSIONS

LASIK-induced monovision is a valid option for myopic patients with presbyopia, with a relatively low incidence of enhancements. The low retreatment rate to reverse monovision is a good index of patient tolerance and satisfaction with the results of the procedure. For this reason, a preoperative trial of monovision with contact lenses should not be mandatory before LASIK.

[Cardiovascular effects of aqueous extracts of the leaves of Clusia coclensis (Guttiferae)]

Aqueous extracts of the leaves of Clusia coclensis, (Guttiferae) injected intravenously to 42 normal Sprague-Dawley rats and to 42 Spontaneous Hypertensive rats, in 7 different doses, induced a rapid and transitory decrease in blood pressure and heart frequency. The magnitude of blood pressure decrease was dose-dependent. The effect was statistically significant (p < or = 0.01), probably due to sympathetic stimuli.

[Pharmacologic activity of the aqueous wood extract from Quassia amara (Simarubaceae) on albino rats and mice]

All the assays were done with an aqueous preparation of dry wood from Quassia amara (Simarubaceae). For the hippocratic assay, 12 female SDN rats were used, with an average weight of 144 g and separated in three groups of four individuals each. The dose used were 500 mg/kg and 1,000 mg/kg and the control group received 0.5 ml of distilled water. The extract administration and the observation of the animals were done daily during nine days. Acute toxicity of the preparation was studied with 25 male NGP mice with an average weight of 20.13 g, in groups of five individuals per dose. The oral administration was carry out with the following doses: 250, 500, 750 and 1,000 mg/kg, the control group received 0.5 ml of distilled water. No sign of acute toxicity was observed at any dose. For the toxicity analysis via intraperitoneal injection 15 male NGP mice were assigned to five groups (5 animals each) with doses of 500 and 1,000 mg/kg and a control group with 0.5 ml of distilled water. The group with the dose of 500 mg/kg, presented acute toxicity signs with a 24 hr recovery, and the 1,000 mg/kg dose was lethal to a 100% within 24 hr. The measuring of the peristaltic activity (movement of the intestinal content) were performed on 30 NGP male mice with an average weight of 22 g assigned to three groups of ten individuals each. One dose of 500 mg/kg and 1,000 mg/kg were orally administrated to each experimental group and 0.5 ml of distilled water to the control group. The marker used was activated carbon, orally supplied to every mice 30 min after the administration of the aqueous extract. The animals are decapitated and the measurement of the carbon motion in the small intestine was done after 30 min. Both dose increased the intestinal movement compared to the control group, but only the 1,000 mg/kg dose showed a statistically significant difference (p < or = 0.05).

Evaluation of the quality of the water in El Hondo natural park located in the east of Spain

The purpose of the present work was to evaluate the quality of the water in El Hondo Park, an important wetland located in the east of Spain (province of Alicante) and included on the Ramsar List. The influence of the input of pollutants was assessed over a 14-month period in order to propose remedial action. Three different sources of waters were studied: irrigation water, brackish water and reservoir water. The irrigation water was found to have a high value of conductivity with high concentrations of Cl-, SO(4)2-, Na+ and K+ due to the influence of the brackish water. The concentration of organic matter given as CODT (total chemical oxygen demand) was found to be in the range of 70-600 mg/L of CODT, which was comparable to low-middle strength wastewater. A high concentration of Chlorophyll (a) was found in samples of reservoir water and the eutrophication of this water was thus observed. A high linear relationship was found among CODT, CODF (filtered COD) and BOD5; among electrical conductivity (E.C.), Cl-, SO4(-2), Na+, K+, Ca2+ and Mg2+ and among pH, CO3H- and CO(3)2- in all the samples evaluated. Taking this fact into consideration, a simplified water quality index (WQI) was calculated. Using this parameter, the quality of the water from different sources and its variation during the period evaluated was determined to be at a maximum during the months of December to February, which coincided with the period of high precipitations and low temperature. The highest values of this parameter were found in the samples corresponding to the reservoir water while the lowest values were found in the samples of the brackish water. By determination of the WQI, the influence of the brackish water on the quality of water for irrigation and reservoir waters was confirmed.

Generation of sub-microsecond quasi-unipolar pressure pulses

We present a method to generate sub-microsecond quasi-unipolar pressure pulses. Our approach is based on the laser irradiation of a thin copper wire submerged in water. The acoustic waveforms were recorded using two different, well characterized, wideband detection techniques: piezoelectric and optical interferometry. The results show that the irradiated target behaves as an omnidirectional source. Moreover, the peak pulse pressure linearly depends on the laser fluence and the source size. From the results, we propose an empirical equation for the spatial and temporal profile of the pressure pulse. The method has several advantages: ease of implementation, high repeatability, wide ultrasonic bandwidth and quasi-unipolar time profile. These features lead to potential applications of this acoustic source in ultrasonic characterization such as transducer systems, materials or passive devices.

A method for the calibration of wideband ultrasonic sensors for optoacoustics

A method for calibration of ultrasonic sensors for optoacoustics that provides both frequency response and sensitivity is presented. In order to obtain the bandwidth and the frequency response of an uncalibrated sensor, a point source with broadband spectra generated by a laser-induced bubble on a copper wire submerged in water is employed. On the other hand, the sensitivity measurement relies on the spatial symmetry of the pressure pulse and on a calibrated transducer. Therefore, two sensors are employed to detect the pressure pulse at the same distance from the source. The symmetry of the acoustic field that arrives at both transducers is adjusted and verified by means of an optical interferometer that provides a null signal when the copper wire is placed at the right position. The method is tested on the characterization of a thin-film polymeric piezoelectric transducer with a cylindrical focused shape.