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After three successive treatments with oxamniquine the continuing elimination of Schistosoma mansoni eggs was observed in patients, who came from various regions of Brazil, with different clinical forms of schistosomiasis. The objective of the present study was to determine the experimental behaviour of five different S. mansoni isolates in Swiss Webster mice that were submitted to treatment with the same drug. The experimental group with failure of treatment showed higher mean number of surviving male worms when it was compared to the group without failure of treatment. These date suggest the possibility of resistance to oxamniquine.

Purpose: To analyze the learning curve for state-of-the-art phacoemulsification performed by residents., Setting: Department of Ophthalmology, Hospital de Clinicas José de San Martin, University of Buenos Aires, Buenos Aires, Argentina., Methods: The records of patients having phacoemulsification performed by residents from June 1996 to January 1998 were reviewed for preoperative and postoperative best corrected visual acuities and the occurrence of complications. The phacoemulsification technique used for the first 35 surgeries of each resident was compared with that of their last 35 surgeries., Results: The records showed 249 cases of phacoemulsification by residents. Mean preoperative best corrected visual acuity was 0.19 +/- 0.19 (SD). One month postoperatively, it was 0.86 +/- 0.2. Nuclear fracture was performed in a mean of 28.33 +/- 5.0 of the first 35 surgeries by each resident, whereas chopping techniques were used in a mean of 23.33 +/- 1.5 of the last 35 cases. Vitreous loss occurred in 2.8% of cases., Conclusion: Residents learned cracking and chopping phacoemulsification techniques safely with satisfactory outcomes.

Purpose: To analyze the effectiveness of laser in situ keratomileusis (LASIK) and arcuate keratotomy (AK) to treat simple myopic, compound myopic, and mixed astigmatism., Setting: Instituto de la Visión, Buenos Aires, Argentina., Methods: This retrospective nonrandomized study comprised 821 cases treated with LASIK and 46 cases treated with AK. Patients were divided into 4 groups, which had the following preoperative cylinder corrections: simple myopic astigmatism (Group 1) (LASIK: n = 76, -3.91 diopters [D] +/- 1.29 [SD]; AK: n = 5, -3.85 +/- 0.65 D); compound myopic astigmatism up to 2.00 D (Group 2) (LASIK: n = 401, -1.69 +/- 0.76 D; AK: n = 14, -1.48 +/- 0.41 D); compound myopic astigmatism over 2.00 D (Group 3) (LASIK: n = 253, -3.61 +/- 0.89 D; AK: n = 16, -3.09 +/- 0.84 D); mixed astigmatism (Group 4) (LASIK: n = 91, +3.65 +/- 1.62 D; AK: n = 11, 4.39 +/- 0.92 D)., Results: Six months postoperatively, the cylinder's vector-corrected change was as follows: Group 1, LASIK 3.75 +/- 1.08 D, AK 3.16 +/- 0.84 D; Group 2, LASIK 1.55 +/- 1.12 D, AK 1.34 +/- 0.44 D; Group 3, LASIK 3.39 +/- 0.98 D, AK 2.70 +/- 1.21 D; Group 4, LASIK 3.77 +/- 1.43 D, AK 3.75 +/- 0.89 D. Respective mean uncorrected visual acuities in each group were as follows: Group 1, 0.71 +/- 0.12 and 0.60 +/- 0.12; Group 2, 0.83 +/- 0.12 and 0.78 +/- 0.24; Group 3, 0.78 +/- 0.18 and 0.48 +/- 0.24; Group 4, 0.69 +/- 0.21 and 0.55 +/- 0.18., Conclusions: The vector-corrected change and visual acuity achieved with LASIK were better, although not significantly, than those attained with AK except for the UCVA obtained with LASIK in eyes with compound myopic astigmatism over 2.00 D. Both methods proved to be safe.

Purpose: To evaluate the results of laser in situ keratomileusis (LASIK) to treat hyperopia., Setting: Instituto de la Vision, Buenos Aires, Argentina., Methods: This nonrandomized study comprised 679 eyes of 321 patients having LASIK. Patients were divided into three groups based on preoperative spherical equivalent: Group A (low hyperopia, 2.00 diopters [D] or less); Group B (moderate hyperopia, between 2.00 and 3.00 D); Group C (high hyperopia, more than 3.00 D). The following were measured postoperatively: uncorrected visual acuity (UCVA); best spectacle-corrected visual acuity (BSCVA); refraction (evolution and distribution); lines of visual acuity gained and lost. Follow-up was 1 month in 79.4% of cases, 3 months in 75.5%, 6 months in 68.5% and 1 year in 38.3%., Results: Six months after LASIK. 100% of cases in Group A, 95.3% in Group B, and 71.4% in Group C were within +/- 1.00 D of emmetropia; UCVA was 20/40 or better in 94.1, 100, and 87.8%, respectively. The percentage losing or gaining 0 +/- 1 line of BSCVA was 100, 97.6, and 100, respectively., Conclusions: Laser in situ keratomileusis was predictable and safe in the treatment of low and moderate hyperopia.

A clinical study on the evolution of patients with schistosomiasis mansoni has been conducted since 1983 at the outpatient clinic of the Infectious and Parasitic Disease Service in the Clementino Fraga Filho University Hospital in Rio de Janeiro, Brazil, comparing prevalence of positive tests for HBsAg, anti-HBsAg, and anti-HBc among patients infected with Schistosoma mansoni coming from various regions of Brazil and with different clinical forms of the disease. A non-significant predominance of HBsAg, anti-HBsAg, and anti-HBc was detected among patients with the hepatosplenic form of schistosomiasis, who presented a more severe clinical evolution with a higher frequency of hematemesis and/or melena, in addition to the development of macronodular cirrhosis and a worse prognosis as compared to patients with the toxemic form, schistosomiasis-infection and the hepatointestinal form.

Purpose: To analyze the results after laser-assisted in situ keratomileusis (LASIK) treatment for positive cylinder at the flattest meridian., Setting: Instituto de la Visión, Buenos Aires, Argentina., Methods: A prospective, nonrandomized study was conducted. Patients were divided into three groups: (1) simple hyperopic astigmatism (SHA); 15 eyes with a mean preoperative cylinder of +3.37 diopters (D) +/- 1.62 (SD); compound hyperopic astigmatism (CHA); 75 eyes with a mean preoperative cylinder of +3.34 +/- 1.39 D; (3) mixed astigmatism (MA); 73 eyes with a mean preoperative cylinder of +3.45 +/- 2.15 D. In all eyes, treatment of the cylinder was performed at the flattest meridian by LASIK using the Chiron-Technolas Keracor 116/117 laser. The following parameters were analyzed over time: uncorrected visual acuity; best corrected visual acuity; correction of the spherical equivalent and the cylinder; lines of visual acuity gained and lost., Results: Six months after the procedure, refractive cylinder was reduced to +0.58 +/- 1.22 D in the SHA group, +0.12 +/- 1.23 D in the CHA group, and -0.11 +/- 1.28 D in the MA group. Uncorrected visual acuities were 20/20 or 20/25 in 66.7, 60.4, and 76.5% of the groups, respectively., Conclusions: Use of the LASIK technique with the Keracor laser to treat positive cylinder at the flattest meridian corrected simple and compound hyperopic astigmatism and mixed astigmatism with good predictability and safety. This treatment has not produced a hyperopic refractive change at the opposite meridian.

The most frequent postoperative complication in extracapsular cataract surgery is opacification of the posterior capsule. The purpose of this study was to correlate the frequency of capsular opacification with each kind of senile cataract. A total of 566 eyes with cataracts were studied. They had been operated on between 1980 and 1990 using the extracapsular, intercapsular, and phacoemulsification techniques. Our results confirm that senile complete cataracts (mature cataracts) had a significantly lower tendency to produce postoperative capsular opacification than other cataract types (nuclear, cortical, posterior subcapsular).

Epithelial cell counting was performed in 47 fragments from lens anterior capsules obtained during extracapsular and intercapsular surgery. Mean cell count was 3,277 cell/mm2; there was no correlation between cell number and age and no significant difference in cell counts between extracapsular and intercapsular surgery. There were, however, significant differences between advanced cataracts and the other cataract types (2,947 vs. 3,356). This may be important in explaining the differences in regenerative opacification of the posterior capsule in the different types of cataracts.

The ultrastructure of trabeculectomy specimens obtained from enucleated eyes was compared to that of 23 similar specimens extracted from glaucomatous eyes. It was thus possible to study the trabecular meshwork from Schwalbe's line to the iris root, the corneal endothelium, the canal of Schlemm, its inner and outer walls, and the collectors. In the glaucomatous specimens it was possible to verify, for the first time, two aspects which show clinical correlation. The first aspect is pseudoexfoliation: we find in the trabecular meshwork two types of deposits in great quantity. One is formed by a dense irregular fibrillar net, with a diameter oscillating betwwwn 600 and 830 A, surrounding the trabeculae; the others are pigment granules. Both fill the intertrabecular spaces. The first type is also observed on the corneal endothelium lining Schwalbe's ring, stressing the visibility of the intercellular spaces. The second aspect is the pectinate ligament (mesodermic remnant) in late-onset congenital glaucoma. Its pattern is characteristically different from that of the corneoscleral meshwork.