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Biomedical subjects

G Trabucchi

Publications and source records attributed to G Trabucchi.

35 records · Page 2Linked to original sources
PubMed1992

Interactions between light and vitreous fluid substitutes.

To determine the interactions between light and vitreous fluid substitutes, we studied the absorption and fluorescence properties of the following fluids that are commonly used in vitreoretinal surgery: Ringer's solution, balanced salt citrate-buffered solution, balanced salt bicarbonate-buffered solution, hydroxypropyl methylcellulose ophthalmic solution, hyaluronate sodium, perfluorocarbons, silicone oil, and fluorosilicone oil. The absorption spectra for all the fluids peaked in the UV-C (reference range <280 nm) and UV-B (reference range from 315 to 280 nm) regions of the spectrum, with little or no absorption in the visible region of the spectrum (from 400 to 700 nm). Emission of almost all of the fluids occurred mainly in the 300- to 360-nm region, with fairly low-quantum efficiency. The limited light absorption properties of the fluids calls for caution during transpupillary and intraocular laser photocoagulation to avoid excessive retinal damage, mainly when the laser power is increased during treatment. Transmission of incoherent light (environmental and ophthalmic artificial light) through highly transparent vitreous fluid substitutes may lead in time to dangerous light exposure, particularly in aphakic eyes. The emitted fluorescence in these fluids generates a minimal risk of long-term damage.

Absorption↗
PubMed1992

Can the diode laser (810 nm) effectively produce chorioretinal adhesion?

In this study, argon green (514 nm), krypton red (647 nm), and diode (810 nm) lasers were used to produce transpupillary photocoagulations on rabbit chorioretina to simulate a retinal buckle treatment. To evaluate the efficacy of the diode laser in creating a retinopexy effect, the morphologic aspects of the acute lesions and scar development were compared. The study of the acute lesions revealed that the chorioretinal thermal damage produced by the argon green laser involved all the retinal layers and the retinal pigment epithelium. The use of the krypton red and the diode lasers resulted in deeper chorioretinal thermal damage. Two months after the treatments, all the lesions resulted in adhesive chorioretinal pigmented scars. However, the diode lesions produced a deeper scar, characterized by marked chorioretinal atrophy.

Animals↗
PubMed1991

Diode laser compared with argon laser for trabeculoplasty.

A randomized prospective study on two groups of ten patients compared the efficacy of diode laser and argon laser trabeculoplasty. In the diode laser group the intraocular pressure was 23.0 +/- 3.97 mm Hg before the treatment, 20.2 +/- 4.49 mm Hg at two hours, 16.3 +/- 3.13 at six months, and 16.9 +/- 2.80 mm Hg at one year. The differences from baseline were statistically significant at six months (P = .0001) and at one year (P = .0001) but not at two hours. In the argon laser group the intraocular pressure was 23.4 +/- 3.6 mm Hg before the treatment, 22.7 +/- 4.35 mm Hg at two hours, and 17.6 +/- 4.53 mm Hg at six months. One patient had uncontrolled mean high intraocular pressure and underwent surgery. In the nine patients who completed the study the intraocular pressure at one year was 16.7 +/- 3.00 mm Hg. The differences from baseline were significant at six months (N = 10; P = .0001) and 12 months (N = 9; P = .0001) but not at two hours. Differences between the two groups were not significant at two hours, six months, and one year. Laser trabeculoplasty may be effectively with a diode laser.

Aged↗
PubMed1991

Study of laser damage to injection-molded diffractive intraocular lenses.

A study of the probability of damage induced in two implant quality injection-molded diffractive intraocular lenses by a commercial Q-switched Nd:YAG laser is presented. The damage thresholds of the diffractive intraocular lenses (0.10 mJ at 10% probability, 0.24 mJ at 50% probability, and 0.90 mJ at 99% probability) did not differ significantly from those of other poly(methyl methacrylate) lenses manufactured with the same technology. These low values (compared to those of other lens types) suggest that care should be taken during laser capsulotomy in eyes implanted with refractive lenses, with special attention given to power losses at the target site due to diffraction effects.

Laser Therapy↗
PubMed1991

Histopathology of continuous wave neodymium: yttrium aluminum garnet and diode laser contact transscleral lesions in rabbit ciliary body. A comparative study.

Neodymium: yttrium aluminum garnet (Nd:YAG) laser transscleral cyclophotocoagulation has been shown to be an effective method of lowering intraocular pressure (IOP). Transmission and absorption features of diode laser radiation (810 nm) make these new laser sources suitable for production of transscleral thermal lesions. The transscleral effects on rabbit ciliary body of Nd:YAG and diode laser wavelengths were compared using a CW Nd:YAG laser and a CW Aluminum Gallium Arsenide diode laser. Both lasers were delivered by silica optic fibers, 600 microns in diameter. Eight rabbits were treated by applying the optic fiber 0.5 mm from limbus while increasing energy values from 0.2-2 J. The lesions produced at equal energy values underwent gross and histologic and ultrastructural comparison. Gross examination revealed threshold lesions at 1 J energy for the Nd:YAG laser and 0.8 J for the diode laser. The diode laser produced transscleral thermal lesions of the rabbit ciliary body comparable to those achieved by the Nd:YAG laser. The histologic and ultrastructural study showed that diode laser radiation produced more remarkable damage to the ciliary pigmented structures, causing deep coagulation necrosis of the pigmented epithelium, wide disorganization of the collagen in the stroma, and intravascular coagulation phenomena in the ciliary vessels. Before the introduction of these new laser sources in clinical transscleral procedures, further investigation is needed to determine optimal energy levels.

Animals↗
PubMed1990

Probe placement and energy levels in continuous wave neodymium-YAG contact transscleral cyclophotocoagulation.

To improve the reliability of the technique, contact transscleral cyclophotocoagulation was performed using a continuous wave neodymium-YAG laser. Radiation was delivered via a fiberoptic system to two human eyes destined for enucleation due to choroidal melanoma. Distances from the corneal limbus to where the fiberoptic probe was placed, perpendicular to the conjunctiva, were varied, as were the energy values. Gross, light microscopic, and scanning electron microscopic examinations revealed that contact probe placement at a distance of 1.5 mm from the corneal limbus with an energy setting of 2 J provided optimum cyclophodestructive results. Slight superficial damage to the sclera was detected, but observations indicated no alterations to the adjacent anatomical structures. To obtain lesions to the ciliary processes in living eyes similar to those previously noted in human cadavers, comparatively lower energy values (2 J) were required. To exploit all the mechanisms that may lead to a decrease in intraocular pressure, precise hitting of the aqueous humor secretory structure may prove to be of primary importance.

Choroid Neoplasms↗
PubMed1990

Comprehensive study of damage to intraocular lenses by single and multiple nanosecond neodymium: YAG laser pulses.

The results of an extensive study of the probability of damage induced in implant quality intraocular lenses (IOLs) by a commercially available nanosecond Nd:YAG photodisruptor are presented. These results were compared with the morphology of damage seen on scanning electron microscopy. The differences in the shape of the damage probability curves derived for the different lens groups demonstrate that a single threshold value does not characterize the threshold for IOL damage. We suggest that a standard method using a clinical photodisruptor be used by all workers to derive these curves for all IOLs in clinical use. The clinical relevance of our findings is emphasized.

Lasers↗
PubMed1989

Contact transscleral irradiation of the human chorioretina with continuous-wave Nd:YAG laser.

We performed contact transscleral chorioretinal photocoagulations with a continuous-wave Nd:YAG laser on two human eyes affected by choroidal melanomas. An optical-fiber system without any focalization tip was used to deliver the laser energy by placing the fiber in contact with the sclera in the position corresponding to the chorioretinal area to be photocoagulated. With a power of 4 W and an exposure time of 0.5 s, frank white coagulations were obtained. Histological and ultrastructural examination evidenced that the choroidal pigment and the retinal pigment epithelium were the target structures of the radiation. No substantial alterations of the sclera were noted while a good adhesion between the retina and the pigment epithelium cells was observed. The results obtained show that transscleral contact lasers may be safely used in the treatment of some pathologies of the ocular fundus.

Choroid↗
PubMed1989

Histopathology of diode and argon laser lesions in rabbit retina. A comparative study.

Argon lasers are the most frequently used laser source for retinal photocoagulation. These are expensive, bulky and low-efficiency devices. In contrast, diode semiconductor lasers have a number of characteristics that make them attractive for medical application: compact size, high electrical-to-optical efficiency, and long operating lifetime. Comparable irradiance lesions (about 120 Wcm2), ophthalmoscopically similar to those obtained therapeutically in humans, were obtained by a diode and an argon laser. Twenty-four hours after the treatment, a study of these lesions was made by light and electron microscopy. Argon irradiations resulted in damage to both the inner and the outer retinal layers, while the diode laser radiation produced damage to the outer retina and choroid. A sufficient diode laser light passed into the choroid to induce small vessel occlusions and/or edema. The histological characteristics of the lesions produced by the two lasers suggest the use of the diode lasers, as well as argon lasers, in the treatment of retinal and subretinal pathologies.

Animals↗
PubMed1989

Contact transscleral cyclophotocoagulation with Nd:YAG laser in uncontrolled glaucoma.

To evaluate the effectiveness of contact delivery systems, we treated 23 eyes with uncontrolled intraocular pressure using a continuous wave Nd:YAG laser delivered by a fiber optic. With the fiber's tip perpendicular to the surface of the conjunctiva, 1.5 mm from the corneal limbus, we applied 16 laser spots of 2 J/second energy. Patients were followed for at least 6 months (mean, 8.6 +/- 2.4 months). The mean pressure decreased from a pretreatment value of 43.7 mm Hg to a posttreatment value of 24.7 mm Hg (P = 0.000). A total of 66.6% of the treated eyes achieved a pressure on last follow-up visit of 25 mm Hg or less. Pain decreased in all the patients treated (P less than .005). Complications were minimal.

Evaluation Studies as Topic↗
PubMed1987

Transscleral contact cyclophotocoagulation with Nd:YAG laser CW: experimental study on rabbit eyes.

The authors suggest a new type of transscleral cyclophotocoagulation by using the Nd:YAG laser. This was done by bringing fibre optics into contact with the sclera. The study illustrates the macroscopic, histologic and scanning electron microscopic changes produced on the ciliary body of rabbit eyes with this technique. The actual possibility and the future prospect of applying this method to the human eye still remain to be investigated.

Animals↗
PubMedDate not supplied

Contact transscleral cyclophotocoagulation with diode laser in refractory glaucoma.

OBJECTIVE: To evaluate the clinical effectiveness of contact transscleral cyclophotocoagulation (CTCP) with diode laser. DESIGN AND PATIENTS: Forty-eight seeing eyes and 20 blind and painful eyes of 68 patients suffering from refractory glaucoma were treated using a diode laser (EOS3000, Laser Science) coupled with a 400-microns optic fiber ending in a 3-mm focusing tip. Sixteen to twenty 3.9-J (2.6 W x 1.5 to 2.5 s) laser spots were placed over 360 degrees, 1.5 mm from the corneolimbal junction. RESULTS: In the seeing-eye group, the follow-up was 20.7 +/- 8.14 months, pre- and posttreatment IOPs were 37.1 +/- 11.27 and 19.5 +/- 8.73 mmHg respectively (p < 0.0001), and success (IOP > 2 and < or = 21 mmHg) was 70.8%. No significant visual acuity change was found in the successful eyes, whereas a significant visual acuity reduction was found in the unsuccessful cases (p = 0.03). In the blind-eye group, the follow-up was 20.5 +/- 8.54 months, pre- and post-treatment IOPs were 50.7 +/- 15.05 and 20.6 +/- 13.99 mmHg respectively (p < 0.0001), and success (remission of pain) was 100%. As for complications, one seeing eye developed a spontaneously-resolved vitreous hemorrhage and one seeing and one blind eye became hypotonic, though no phthysis was observed. No conjunctival or lens damage was detected, and no scleral thinning was revealed by ultrasound biomicroscopy. No case of sympathetic ophthalmia was found. CONCLUSIONS: Diode laser can be successfully employed for CTCP in refractory glaucoma.

Anterior Eye Segment↗
PubMedDate not supplied

Indocyanine green angiography (ICGA) in pathological myopia.

One hundred and fifty patients (300 eyes), mean age 49 +/- 15 years, with degenerative myopia underwent fluorescein and indocyanine green angiography (ICGA). Fluorescence of choroidal neovascularization (CNV) on ICGA was less evident than with fluorescein angiography (FA). FA revealed CNV in 98 eyes; ICGA showed CNV with different angiographic patterns in 82 eyes. ICGA permitted CNV diagnosis when retinal hemorrhages were present. ICGA allowed a more precise evaluation of lacquer cracks which appeared more numerous than the ones identified by FA. ICGA visualized the retrobulbar vasculature. This study shows that ICGA has a useful role for diagnosing and managing pathological myopia.

Adult↗
PubMedDate not supplied

Diode and Nd:YAG laser contact transscleral cyclophotocoagulation in a human eye: a comparative histopathologic study of the lesions produced using a new fiber optic probe.

We compared the contact cyclodestructive effects (both gross and histologic) achieved with diode and Nd:YAG laser wavelengths (810 and 1064 nm, respectively), using equivalent energy doses, released by means of a new optical delivery system in a human eye that was soon to be enucleated because of a choroidal melanoma. For both lasers, a fiber optic system (400 microns) with a focusing microlens placed at the end of the fiber was used. The center of the beam was placed 1.5 mm from the corneoscleral limbus. At medium (5.2 to 6.6 J) and higher (7.8 J) energy levels, the cyclodestructive thermal damage produced by the diode laser appeared more widespread than that created by the Nd:YAG laser. At lower levels (3.6 to 3.9 J), both laser treatments produced similar lesions. The new delivery system proved to be safe and effective in achieving the desired cyclodestructive effects at both wavelengths.

Choroid Neoplasms↗
PubMedDate not supplied

The erodible mask in photorefractive keratectomy for myopia and astigmatism.

This paper reports a new approach for performing photorefractive keratectomy (PRK) that uses an erodible mask to control shape transfer processes. The advantages of this technique, when compared to conventional PRK performed with mechanical diaphragm, are 1) the possibility of transferring almost any shape onto corneal surface; 2) a smoother corneal surface following photoablation; 3) easier eye fixation; and 4) a controlled humidified environment over ablation zone. We report our experimental study on scanning electron microscopy of polymethylmethacrylate (PMMA) plates ablated using conventional technique versus erodible mask technique; the results showed a smoother surface in the PMMA plate ablated using the erodible mask. We also report our preliminary clinical results of four eyes treated for the correction of myopia combined with astigmatism. Myopia ranged from -2.00 to -10.00 D, and astigmatism ranged from -1.50 to -2.50 D. Three months after surgery, all four eyes were within +/- 1.00 D of myopic attempted correction, but astigmatism was completely corrected only in one eye. No complications or scarring have been reported. We believe the erodible mask could be effective in the correction of myopia and myopic astigmatism, but further improvements are necessary to allow easier alignment of the mask over the eye. All commonly available excimer laser devices produce photorefractive keratectomy as a concentric ablation of the corneal stroma, deeper in the center than in the peripheral part; this is produced by means of an iris or diaphragm which, depending on the type of laser, progressively opens or closes, allowing a greater laser beam delivery in the center.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗