Biomedical subjects

F Baccara

Publications and source records attributed to F Baccara.

13 recordsLinked to original sources

PubMed1999

Effect of astigmatism on multifocal intraocular lenses.

PURPOSE: To study the effect of astigmatism on multifocal intraocular lens (MIOL) function. SETTING: Laser Laboratory, Department of Electronics, Electrotechnics and Informatics, University of Trieste, Italy. METHODS: Using an experimental optical system, this study compared the division of a laser beam in the focal spots of 1 monofocal IOL (Pharmacia 722A), 1 bifocal IOL (Pharmacia 811E), and 2 MIOLs (AMO Array MPC25NB and Domilens Progress 1). The model consists of a helium-neon laser and an optical system: a triangular optical bench with a precision collimator, a micropositionable immersion stage to support the IOL, and a digital image-processing system. Astigmatism was induced by interposing a +1.0 diopter (D) cylinder lens between the IOL and the television camera. Astigmatism was corrected by adding a -1.0 D cylinder lens in front of the IOL on the same axis. RESULTS: Astigmatism creates pairs of focal lines, 1 for each focal spot in the IOL. In the multifocal IOL, the posterior focal line of the nearest focus interfered with the anterior line of the next focus. Correcting the astigmatism led to a significant reduction (mean 20%) in light intensity. CONCLUSIONS: Astigmatically neutral surgery or surgical correction of pre-existing astigmatism is essential in MIOL implantation to minimize the decrease in contrast sensitivity.

Astigmatism↗

PubMed1998

Spatial resolution threshold in pseudophakic patients with monofocal and multifocal intraocular lenses.

PURPOSE: To compare the spatial resolution threshold in the central visual field of pseudophakic patients with monofocal and multifocal intraocular lenses (IOLs). SETTING: Eye Clinic, University of Trieste, Italy. METHODS: Twenty phakic normal subjects and four groups of 20 pseudophakic patients each, implanted with refractive and diffractive multifocal IOLs (Domilens Progress 1, AMO Array MPC25NB, or Pharmacia 811X) or with monofocal IOLs (Allergan PC43NB), were studied. The spatial resolution threshold in the central visual field was assessed using high-pass resolution perimetry. Measurements were performed adding spherical correction to test the different foci of the IOL. RESULTS: No significant differences between phakic subjects and pseudophakic patients with monofocal IOLs were found. In distance vision, no significant differences between patients with refractive multifocal IOLs and those with monofocal IOLs were found. The group with the diffractive multifocal IOL showed a significantly higher spatial resolution threshold (P = .003). In intermediate vision, the AMO Array group showed a significantly lower spatial resolution threshold than the other groups (P < .01). The best performance at near distance was in the diffractive group, which was statistically significantly different from the other groups (P < .001). CONCLUSION: In the diffractive group, the high spatial resolution threshold in distance vision could be explained by the lower brightness of the principal focus, related to a different light energy division between the foci. In the Domilens group, the high spatial resolution threshold in near vision could be related to the light energy scattered in a large number of foci.

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PubMed1998

Analysis of light energy distribution by multifocal intraocular lenses through an experimental optical model.

PURPOSE: To analyze and compare the light energy distribution generated by multifocal intraocular lenses (IOLs). SETTING: Laser Laboratory of the Department of Electronics, Electrotechnics and Informatics, University of Trieste, Italy. METHODS: An optic system to examine the division of a laser beam in the various focal spots of multifocal IOLs was developed. The model consists of a helium-neon laser and an optical system: a triangular optical bench with a precision collimator, a micropositionable immersion stage supporting the IOL to be measured, and a digital image-processing system. Four bifocal and three multifocal IOLs were studied. This system is able to expand the distance between foci, leading to a sharper separation of the focal spots. The resolution of the images makes it possible to analyze the distribution of total light energy among the foci. RESULTS: Results showed the variation in light intensity of the focal spots of multifocal and bifocal IOLs, as well as their disposition in the dioptric range. CONCLUSION: Light distribution among various focal distances corresponded to the foci provided by monofocal, bifocal, and multifocal IOLs. The percentage of light energy distribution was related to the importance of each focus.

Lenses, Intraocular↗

PubMed1997

Postoperative cellular reaction on various intraocular lens materials.

PURPOSE: The presence of cellular deposits on the surface of intraocular lenses (IOLs) is a manifestation of: (1) the breakdown of the blood-aqueous barrier produced by surgery; and (2) foreign body reaction induced by lens implantation. The purpose of this study was to assess the presence of cellular deposits on the surfaces of various IOL materials. METHODS: Fifty patients scheduled for cataract surgery were randomized into five groups of ten patients each and received IOLs of the following materials: conventional polymethylmethacrylate (PMMA), surface-passivated PMMA, heparin-surface modified PMMA, poly-hydroxyethylmethacrylate (HEMA) hydrogel and silicone. Patients were examined at 7 days, 30 days, 90 days, and 180 days after surgery. All eyes were observed first via slit-lamp and then using a contact specular microscope for photographic documentation. RESULTS: Small, spindle-shaped cells were observed on all IOLs in the early postoperative period. Epithelioid cells appeared approximately 30 days after surgery on all PMMA IOLs, but most particularly on conventional PMMA IOLs. No cells were observed on poly-HEMA and silicone IOLs. CONCLUSIONS: The decreased number of epithelioid cells discovered in the early postoperative period may indicate a reduction in the inflammatory process induced by surgery. The permanence of epithelioid cells on IOL surfaces may be a sign of foreign body reaction. The results of this study indicated that poly-HEMA and silicone IOLs showed fewer cellular deposits than PMMA IOLs, suggesting that they may be better tolerated than PMMA IOLs.

Biofilms↗

PubMed1997

Corneal endothelial function after extracapsular cataract extraction and phacoemulsification.

PURPOSE: To compare the morphology and function of the corneal endothelium in the early postoperative period after extracapsular cataract extraction (ECCE) and phacoemulsification. SETTING: University Eye Clinic of Trieste, Italy. METHODS: In this prospective, randomized study of patients scheduled for cataract surgery, 40 patients were divided into two groups of 20 patients each. Group 1 had ECCE and Group 2, phacoemulsification; both had capsular bag intraocular lens (IOL) implantation. Preoperatively and 7 and 30 days postoperatively, a complete ophthalmological examination, endothelial specular microscopy, ultrasonic pachymetry, and anterior segment fluorophotometry were done. Visual acuity, endothelial cell density, cell size variation coefficient, corneal thickness, endothelial permeability coefficient, and endothelial pump function were studied. RESULTS: Visual acuity was better 7 days after phacoemulsification than after ECCE, but no differences were observed after 30 days. No significant differences in postoperative loss of endothelial cells were found between the two groups. Coefficient of variation in size, corneal thickness, and endothelial permeability significantly increased in both groups 7 days postoperatively, but only in the ECCE group 30 days postoperatively; the differences between the two groups were statistically significant. Endothelial pump function significantly increased after 7 days in only the phacoemulsification group. CONCLUSIONS: Functional endothelial failure occurred in the early period after ECCE. Phacoemulsification seemed to minimize postoperative functional damage to the endothelium.

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PubMed1997

Corneal endothelial protection by different viscoelastics during phacoemulsification.

PURPOSE: To evaluate corneal endothelium morphology and function after phacoemulsification using different viscoelastics. SETTING: Eye Clinic, University of Trieste, Italy. METHODS: This prospective, randomized study included results of preoperative and postoperative (7, 30, and 90 days) examinations of 66 patients scheduled for phacoemulsification without ocular pathology; 8 patients were excluded. Patients were randomly assigned to one of four groups based on type of viscoelastic used: 1% sodium hyaluronate (Healon); 1.4% sodium hyaluronate (Healon GV); 4% sodium chondroitin sulfate-3% sodium hyaluronate (Viscoat); 2% hydroxypropyl methylcellulose (Hymecel). Mean cell density and cell size variation coefficient were determined by specular microscopy; central corneal thickness, by ultrasonic pachymetry; and endothelial permeability coefficient and active pump function, by anterior segment fluorophotometry. RESULTS: There were no significant differences in postoperative mean cell loss among the groups. The cell size variation coefficient was altered in all groups 7 days after surgery and was still impaired at 30 days in the Hymecel group. A significant increase in mean corneal thickness, endothelial permeability, and active pump function occurred in the Healon and Hymecel groups 7 days after surgery. These parameters were still altered 30 days after surgery in the Hymecel group. Endothelial functional alterations did not occur in the Healon GV or Viscoat group. CONCLUSION: Viscoat and Healon GV are effective in minimizing functional damage of endothelial structure in the early medium-term postoperative period.

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PubMed1994

Heparin-surface-modified intraocular lens implantation in eyes with pseudoexfoliation syndrome.

Eyes with pseudoexfoliation syndrome have a greater risk of intraoperative and postoperative complications. Clinical and histopathological studies indicate that heparin-surface-modified intraocular lenses (HSM IOLs) can reduce postoperative anterior segment inflammation. Our study evaluated the blood-aqueous barrier permeability in eyes with pseudoexfoliation syndrome and implanted with an HSM IOL. We examined two groups of 20 patients, one comprising patients with pseudoexfoliation syndrome and one a sex- and age-matched control group with senile cataracts. Each group was divided into two subgroups of ten patients each. In one subgroup, an HSM IOL was implanted; in the other, a conventional poly(methyl methacrylate) IOL. We performed a complete ophthalmologic examination and iris angiography preoperatively and at 30, 90, and 180 days after surgery. Fluorophotometry was performed at the 90-day and 180-day postoperative examinations. The patients with pseudoexfoliation syndrome had a higher blood-aqueous barrier permeability than did the control group. Permeability decreased significantly three and six months after surgery, especially in the HSM IOL group.

Aged↗

PubMed1994

[Functional evaluation of a new type of intraocular lens: Domilens type PROGRESS 1].

This study presents the first clinical and functional results on the implantation of a new multifocal IOL model, the Domilens type PROGRESS 1. A group of 20 patients underwent extracapsular extraction of cataract with continuous circular capsulorhexis and IOL implantation in the capsular bag. In 65% of the cases, final visual acuity from a far distance proved to be greater than or equal to 8/10 without correction, while visual acuity from a short distance was J2 without the need of additional lenses. BAT identified a decrease in visual acuity of 0.01 Snellen lines at a medium lighting level and 0.05 at the maximum level. The perimetric results obtained with the C 30-2 threshold programme of the Humphrey field analyzer showed a foveal sensitivity threshold of 32.5 dB +/- 9.25 dB and a mean defect of -2.22 dB +/- 2.90 dB. The Vistech VCTS 6500 underlined a decrease in the sensitivity to space frequency contrast of 6.0 c/d versus a control group of patients with monofocal IOL (P < 0.05). This reduction involved a wider range of space frequencies (3.0, 6.0, 12.0 c/d) in comparison with a group of phakic subjects (P < 0.05). With the on-off PEV patterns, a slight decrease in contrast sensitivity threshold was found versus patients with monofocal IOL statistically non significant (P > 0.05). At a medium space frequency of 2.33 c/d, a decrease in contrast sensitivity versus phakic subjects (P < 0.05) was observed. Depth of focus went from infinite to 19 cm. from the eye.

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PubMed1993

Contrast sensitivity in multifocal intraocular lenses.

Contrast sensitivity was measured in two groups of 20 patients each implanted with refractive and diffractive multifocal intraocular lenses and in two control groups of 20 patients each--the first group implanted with a monofocal IOL and the second phakic subjects. All cases had a postoperative follow-up of at least one year and a corrected visual acuity of 20/20- or better. We used two psychophysical tests, Pelli Robson test chart and Vistech 6500 test chart, and an objective test, visual evoked potentials (VEPs). There were no statistically significant differences in contrast sensitivity in the psychophysical tests between the two groups implanted with multifocal IOLs. The situation was different, however, when they were compared with the control group with monofocal IOLs and the group with phakic eyes: the Pelli-Robson test results were not significantly different, but the Vistech 6500 test showed a significant reduction in contrast sensitivity in both groups. The pattern VEPs objective test confirmed these results: no differences were noted between the two different multifocal IOLs, while there was a drop in contrast sensitivity when their results were compared with those of the control groups; the intermediate frequencies were particularly affected by this phenomenon. The contrast sensitivity in patients with multifocal IOLs is reduced despite high visual acuity and this can affect the quality of vision.

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PubMed1993

Long-term results with Iogel IOLs.

130 single piece hydrogel Iogel intraocular lenses (IOL) were implanted in the capsular bag after planned extracapsular cataract extraction. Anterior capsulotomy was performed by capsulorhexis in 59 patients while the envelope technique was used in 71 cases. The mean follow-up was 22 months and the average visual acuity was more than 8/10 in 78.5% of cases. In the capsulorhexis group a higher percentage of IOL was placed right into the capsular bag. No significant inflammatory and noninflammatory postoperative complications occurred. Lens decentration, observed in 5 cases, was due to asymmetric lens placement with one flange in the bag and the other in the ciliary sulcus. In both groups endothelial cell loss was about 7%. Results of the study indicate the safety and the efficacy of the Iogel lens as an intraocular implant. To prevent postoperative decentration and deformation of the IOL unnecessary intraocular manipulation and 'in-out' positioning should be avoided.

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PubMed1992

Refractive bifocal intraocular lens and pupillary diameter.

To assess the relationship between pupillary diameter and focusing for distance and near vision with the refractive bifocal intraocular lens (IOL), we studied visual acuity for far and near distance, near point, and depth of focus with normal pupillary movements and after pharmacological miosis and mydriasis (pilocarpine 2% and phenylephrine 10% eyedrops, respectively) in 20 patients implanted with an IOLAB refractive bifocal IOL. Pharmacological miosis and mydriasis did not change far and near visual acuity values from the values with normal pupillary diameter. After pharmacological miosis, the near point position and the width of the depth of focus were unchanged. After pharmacological mydriasis, near point distance was unchanged but depth of focus dropped in a statistically significant manner (P < .01). We concluded that the pupillary diameter alone cannot produce distance or near vision focusing. The choice depends on the brain's preference. Pupillary diameter increases the quality of vision through the blur circles mechanism.

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PubMed1990

Apparent accommodation in pseudophakic eyes.

The so-called apparent accommodation has been measured in patients implanted with anterior chamber, iris support and posterior chamber IOLs. The data have been related to pupillary diameter and anterior chamber depth in order to explain the actual possibility of a near vision with optical correction only for distance.

Accommodation, Ocular↗

PubMedDate not supplied

Capsulorhexis size and posterior capsule opacification.

PURPOSE: Posterior capsule opacification (PCO) after intraocular lens (IOL) implantation has a multifactored pathogenesis. Capsulorhexis and capsular bag implantation of a one-piece, biconvex poly(methyl methacrylate) (PMMA) IOL are likely to reduce the PCO incidence. This study was performed to determine whether an ideal capsulorhexis size able to reduce PCO incidence exists. METHODS: A retrospective study of 107 patients who had extracapsular cataract extraction with capsulorhexis and capsular bag IOL implantation was carried out. The PCO site (central, paracentral, and peripheral) and degree (mild, moderate, and severe) were evaluated in relation to the capsulorhexis edge location relative to the IOL optic. Slitlamp biomicroscopy and photography and examination with a three-mirror Goldmann lens were performed. Patients were divided into three groups. Group 1: capsulorhexis free edge located on the IOL optic for 360 degrees; Group 2: capsulorhexis free edge located asymmetrically on and peripherally to the IOL optic; Group 3: capsulorhexis free edge located peripherally to IOL optic for 360 degrees. Each group was divided into two subgroups; one received polyHema IOLs and the second, PMMA IOLs. RESULTS: In Groups 1 and 2, the capsular transparency was higher than in Group 3 (P < .04). Central opacification percentage was lower in Group 1 than in Groups 2 and 3 (P < .04). No statistically significant differences between the polyHema and the PMMA subgroups were seen. CONCLUSIONS: Capsulorhexis with a slightly smaller diameter than the IOL optic appears to be better than a large-size capsulorhexis in reducing the incidence of PCO.

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