Impact of a nucleopolyhedrovirus bioinsecticide and selected synthetic insecticides on the abundance of insect natural enemies on maize in southern Mexico.

The impact of commonly used organophosphate (chlorpyrifos, methamidophos), carbamate (carbaryl), and pyrethroid (cypermethrin) insecticides on insect natural enemies was compared with that of a nucleopolyhedrovirus (Baculoviridae) of Spodoptera frugiperda (J. E. Smith) (Lepidoptera Noctuidae) in maize grown in southern Mexico. Analyses of the SELECTV and Koppert Side Effects (IOBC) databases on the impact of synthetic insecticides on arthropod natural enemies were used to predict approximately 75-90% natural enemy mortality after application, whereas the bioinsecticide was predicted to have no effect. Three field trails were performed in mid- and late-whorl stage maize planted during the growing season in Chiapas State, Mexico. Synthetic insecticides were applied at product label recommended rates using a manual knapsack sprayer fitted with a cone nozzle. The biological pesticide was applied at a rate of 3 x 10(12) occlusion bodies (OBs)/ha using identical equipment. Pesticide impacts on arthropods on maize plants were quantified at intervals between 1 and 22 d postapplication. The biological insecticide based on S. frugiperda nucleopolyhedrovirus had no adverse effect on insect natural enemies or other nontarget insect populations. Applications of the carbamate, pyrethroid, and organophosphate insecticides all resulted in reduced abundance of insect natural enemies, but for a relatively short period (8-15 d). Pesticide applications made to late-whorl stage maize resulted in lesser reductions in natural enemy populations than applications made at the mid-whorl stage, probably because of a greater abundance of physical refuges and reduced spray penetration of late-whorl maize.

Stability after laser in situ keratomileusis in moderately and extremely myopic eyes.

OBJECTIVE: To evaluate the stability, mechanism, and degree of regression following laser in situ keratomileusis (LASIK) in cases with moderate to extreme myopia after 2 years of follow-up. SETTING: Single-center clinical trial. METHODS: Fifty-two eyes of 38 patients were enrolled in the study. One year follow-up was available for 47 eyes of 35 patients and 2 year follow-up for 39 eyes of 27 patients. Eyes were divided into 2 groups based on the level of preoperative myopia: Group 1, moderate to high myopia > or =15.0 diopters (D) (range -7.0 to -15.0 D, n = 24); Group 2, extreme myopia >15.0 D (range -15.3 to -25.8 D, n = 15). Laser in situ keratomileusis was performed using the Chiron Automated Corneal Shaper(R) microkeratome and the Summit OmniMed excimer laser. Manifest spherical equivalent, mean central keratometry, and central corneal thickness (CCT) were measured preoperatively and 12 and 24 months postoperatively. RESULTS: Group 1 exhibited a mild myopic shift (mean -0.07 +/- 0.28 D; P >.2) and a mild increase in keratometry (mean 0.05 +/- 0.46 D; P >.6), with an accompanying increase in CCT (mean 7.5 +/- 12.2 microm; (P =.006) at 24 months. Group 2 displayed a significant myopic shift (mean -0.7 +/- 0.7 D; P =.001) and a significant increase in keratometry (mean 0.4 +/- 0.5 D; P =.01), with a mild increase in CCT (mean 2.4 +/- 9.7 microm; P =.35) at 24 months. Corneal ectasia was evident in 1 eye in the extreme myopia group. CONCLUSION: The refractive effect of myopic LASIK up to -15.0 D remained reasonably stable during the second postoperative year. Significant regression of the refractive effect occurred in eyes with higher levels of myopia (>15.0 D), with the risk of progressive ectasia. Extreme caution is recommended when myopic LASIK is performed in eyes with higher levels of myopia.

Laser in situ keratomileusis for myopia of -1.50 to -6.00 diopters.

PURPOSE: To evaluate the results of laser in situ keratomileusis (LASIK) for the correction of low and moderate myopia and astigmatism using the Nidek EC-5000 excimer laser with a modified algorithm. METHODS: Three hundred and ninety-six eyes of 257 patients with myopia ranging from -1.50 to -6.00 D and astigmatism of no more than 4.00 D were included. Manifest spherical equivalent refraction, uncorrected and spectacle-corrected visual acuity were assessed at 1 month (357 eyes, 90%), 3 months (220 eyes, 56%), and 6 months (168 eyes, 42%) after LASIK. RESULTS: Mean preoperative spherical equivalent refraction was -3.60 +/- 1.27 D and mean cylinder was -1.01 +/- 1.08 D. Mean postoperative spherical equivalent refraction was -0.12 +/- 0.31 D and mean cylinder was -0.19 +/- 0.33 D. At 6 months follow-up, 158 eyes (94%) had a mean postoperative spherical equivalent refraction within +/- 0.50 D of emmetropia; 168 eyes (100%) were within +/- 1.00 D. Uncorrected visual acuity was 20/20 or better in 81% (136 eyes) and 20/40 or better in 100%. Two eyes (1.2%) lost 1 line of spectacle-corrected visual acuity due to a decentered ablation. No eye lost 2 or more lines of spectacle-corrected visual acuity. CONCLUSION: Our modified LASIK algorithm with the Nidek EC-5000 excimer laser resulted in safe and predictable outcomes for treatment of low and moderate amounts of myopia and astigmatism.

Laser in situ keratomileusis for simple myopic, mixed, and simple hyperopic astigmatism.

PURPOSE: To summarize initial results of astigmatic laser in situ keratomileusis (LASIK) for 41 eyes of 26 patients using the EC-5000 Nidek system and assess its safety, efficacy and predictability. METHODS: The EC-5000 Nidek excimer laser was used to correct simple myopic, mixed, and simple hyperopic astigmatism with manifest cylinder from 2.00 to 6.50 D. Ablation zone diameters were 6.5 mm (steep meridian ablation) to 7.5 mm (flat meridian ablation) with a repetition rate of 40-41 Hz. In eyes with simple myopic and mixed astigmatism, ablation was performed in both meridians; in eyes with simple hyperopic astigmatism, ablation was performed in the flat meridian alone. Follow-up was 3 months in all eyes. RESULTS: Uncorrected visual acuity was 20/40 or better in 85% of the eyes. Uncorrected visual acuity was equal to the preoperative spectacle-corrected visual acuity in 63% of the eyes. Intended cylinder correction was within 1.00 D in 95% of eyes. No eyes lost lines of spectacle-corrected visual acuity. CONCLUSION: LASIK using the EC-5000 excimer laser appears to effective in the treatment of simple myopic, mixed, and simple hyperopic astigmatism, with favorable results as compared to those previously described for astigmatic keratotomy.