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Biomedical subjects

C Argento

Publications and source records attributed to C Argento.

17 recordsLinked to original sources
PubMed2001

Deep sclerectomy with a collagen implant using the excimer laser.

We describe a new technique of nonpenetrating glaucoma surgery that uses the excimer laser to reduce the risk of perforating the trabeculo-Descemet's membrane. With this technique, the ablation is precise and homogeneous. A collagen device is sutured over the scleral bed to create an outflow pathway for aqueous humor drainage. After a superficial scleral flap is dissected with a diamond knife, the sclera, under direct visualization, is ablated with the excimer laser over Schlemm's canal until aqueous humor percolates through from the anterior chamber. A collagen device is placed over the sclera to allow the aqueous humor to flow from the anterior chamber through the trabeculo-Descemet's membrane. The preliminary results show a drop in intraocular pressure to the middle teens.

Aqueous Humor↗
PubMed2001

Optic capture of the AcrySof intraocular lens in pediatric cataract surgery.

PURPOSE: To assess the results of acrylic intraocular lens (IOL) optic capture in children with cataract. SETTING: Department of Ophthalmology, Hospital de Clínicas José de San Martín, and Instituto de la Vision, School of Medicine, University of Buenos Aires, Argentina. METHODS: Eight children had cataract surgery. After lens and cortex aspiration, an AcrySof (Alcon) IOL was implanted in the bag. A primary posterior capsulorhexis was performed. The optic edges were slipped through the posterior capsule leaflets. Clarity of the visual axis, preoperative and postoperative best corrected visual acuities (BCVAs), and refraction were evaluated. RESULTS: The visual axis remained clear in all cases. No case required a secondary procedure. The mean preoperative BCVA was 0.06 +/- 0.06 (SD). Postoperatively, the mean BCVA was 0.88 +/- 0.11 and the mean spherical equivalent, +0.62 +/- 1.31. The mean follow-up was 28.9 +/- 5.3 months. CONCLUSION: Results show that the optic of an acrylic IOL may be captured through a posterior capsulorhexis in pediatric cataract surgery, combining the advantages of optic capture with a smaller incision and a decreased inflammatory response.

Acrylic Resins↗
PubMed2001

Ciliary body tumor and cataract: local resection combined with phacoemulsification.

A 57-year-old man developed a ciliary body mass, clinically diagnosed as malignant melanoma of the ciliary body, that produced a cataract in the right eye. Treatment was cataract surgery with sclerouvectomy performed simultaneously. Pathohistologic examination revealed an acquired adenoma of the nonpigmented ciliary epithelium. The clinicopathologic features and treatment of this tumor are discussed.

Adenoma↗
PubMed2001

Corneal ectasia after laser in situ keratomileusis.

PURPOSE: To describe 7 patients who developed ectasia following laser in situ kerato-mileusis (LASIK). SETTING: Instituto de la Visión, Buenos Aires, Argentina. METHODS: In this retrospective study of 7 patients, visual acuity, refraction, pachymetry, and corneal topography were examined before and after the refractive procedure and the occurrence of ectasia. RESULTS: Two of the 7 patients required penetrating keratoplasty. Ectasia developed within a mean of 1.02 years +/- 0.31 (SD). The clinical evolution of ectasia and the potential physiopathogenic causes of ectasia are described. CONCLUSION: Ectasia should be considered a potential complication of LASIK that is closely related to corneal thickness, but another variable, the optical zone diameter, should also be considered.

Adult↗
PubMed2001

Customized ablation for asymmetrical corneal astigmatism.

PURPOSE: To evaluate laser in situ keratomileusis (LASIK) cases in which a customized ablation assisted by corneal topography was performed. SETTING: Instituto de la Visión, Buenos Aires, Argentina. METHODS: The study group comprised 23 cases with asymmetrical corneas; 17 had myopia and 6, hyperopia. Visual acuity, spherical equivalent (SE), and cylinder vectorial change measurements, along with keratometry and corneal topography, were performed in all cases preoperatively and postoperatively. RESULTS: In the myopic cases, the mean preoperative SE was -4.92 diopters (D) +/- 2.46 (SD); it was -0.38 +/- 0.66 D after a mean follow-up of 4.41 +/- 2.32 months. In the hyperopic cases, the preoperative SE was +3.54 +/- 1.57 D; it was +0.33 +/- 0.50 D after a mean follow-up of 3.42 +/- 3.23 months. Cylinder vectorial change, visual acuity, and the number of visual acuity lines gained or lost were also evaluated in both groups. CONCLUSION: Although some features of our algorithm for corneal-topography-assisted customized ablations should be modified, the results of our treatment of cases with asymmetrical astigmatism were encouraging.

Adult↗
PubMed2001

Arterial narrowing as a predictive factor in glaucoma.

PURPOSE: To evaluate whether retinal arteriolar widths change in normal patients and in different glaucoma types. We measured the arteriolar width at the merge in the optic nerve (MD), at the edge of the optic nerve (ED) and at the peripapillary area (1 disc diameter distance) (disc distance D). HRT software 1.11, Interactive Means program was used. One hundred forty three eyes of seventy-two patients divided in four subgroups normal, low-tension glaucoma (LTG), primary open angle glaucoma (POAG) and ocular hypertensive (OH). No statistically significant was found in each studied group. The normal patients showed no changes in the retinal arteriolar width compared with all the glaucoma groups.

Glaucoma, Open-Angle↗
PubMed2000

Contrast sensitivity assessment using the visual performance tester.

The visual performance tester (VPT), a device that uses patient response time as a variable to assess visual power, is described. Results in 126 emmetropic eyes that had not had surgery are presented. The VPT provides more complete and accurate information about visual performance than the standard visual acuity examination because the device considers all variables involved in visual function results.

Contrast Sensitivity↗
PubMed1999

Laser in situ keratomileusis versus arcuate keratotomy to treat astigmatism.

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.

Astigmatism↗
PubMed1997

An Intersurface Stress Tensor

Distributed forces resulting from molecular interactions between macroscopic bodies are usually concentrated near surfaces. A new formulation has been developed that replaces these distributed body forces by effective surface tractions and is not limited by the geometrical restrictions of Derjaguin's approximation. It offers great computational simplification over the use of the body-force distribution. The body-force distribution is integrated and partitioned to various surface elements. The resulting expressions for surface traction involve a second-order tensor termed the intersurface stress tensor. It is a symmetric tensor defined for any body in terms of the intermolecular potential and the shape of the body. It acts much like the internal stress tensor; the surface traction vector on a surface introduced into its field is the inner product of the tensor and the surface normal. The new surface formulation reduces to Derjaguin's approximation for the case of a half-space with a plane surface. Properties of the new tensor are explored. Actual components are derived for several geometries.

Journal Article↗
PubMed1992

Incidence of postoperative posterior capsular opacification with types of senile cataracts.

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).

Adult↗
PubMed1990

Study of the lens epithelial cell density in cataractous eyes operated on with extracapsular and intercapsular techniques.

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.

Adolescent↗
PubMed1977

Scanning electron microscopy of the trabecular meshwork in normal and glucomatous eyes.

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.

Cornea↗
PubMedDate not supplied

Smoothness of ablation on acrylic by four different excimer lasers.

PURPOSE: There are many different excimer laser devices available for photoablative refractive surgery. Smoothness of ablation may vary with different excimer lasers systems. METHODS: Ablations were performed on polymethylmethacrylate (PMMA) plates of 8 x 4 x 0.5 cm, with four different excimer lasers: VISX-Star, Coherent Schwind Keratom I/II, Chiron Technolas Keracor 117C (Plano Scan), and the Nidek EC-5000, to determine and compare the homogeneity and smoothness of the surface. Ten -3.00 D samples, ten -6.00 D samples, and ten -9.00 D samples were ablated with each laser. The PMMA discs were examined with optical microscopy, documented by photographs, and each sample was measured quantitatively using a Hommel-Werkel rugosimeter. We used the same PMMA material throughout. RESULTS: Statistically significant differences in smoothness were found between the Chiron Technolas 117C and the VISX-Star, Nidek and VISX-Star, and Coherent Schwind and VISX-Star in the homogeneities achieved by ablating -3.00 D. Ablations of -6.00 D resulted in homogeneities that were statistically significantly different: Chiron Technolas 117C with the other three devices, the Nidek EC-5000 with the VISX-Star, and the Coherent-Schwind with the VISX-Star. In the ablations for -9.00 D, statistically significant differences in homogeneity were found between the Chiron Technolas 117C and Nidek, between the Chiron and VISX-Star, between the Coherent Schwind and VISX-Star, and between the Nidek and VISX-Star. The laser with the scanning spot system was smoother. CONCLUSION: Scanning spot technology produced smooth ablations even up to -9.00 D.

Lasers, Excimer↗