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Biomedical subjects

M Verdi

Publications and source records attributed to M Verdi.

9 recordsLinked to original sources
PubMed1996

Study of photoablation of rabbit corneas by Er:YAG laser.

BACKGROUND AND OBJECTIVE: This work studied the ablation mechanisms of rabbit corneas by the Erbium:YAG laser. The occurrence of thermal and mechanical damages in the tissue as a function of the laser fluence was also investigated. STUDY DESIGN/MATERIALS AND METHODS: The experiments were performed both on enucleated eyes and in vivo. An ultrafast imaging technique was used to investigate the dynamic evolution of the ablation. The treated samples underwent histological and ultrastructural study. RESULTS: A single high fluence laser shot led to the complete removal of the epithelium by a photomechanical effect. In eyes whose epithelium was manually removed, high fluence pulses resulted in evident tears in the stroma, whereas low fluence pulses led to few microns deep incisions, characterized by limited mechanical and thermal damages. CONCLUSION: The photomechanical action plays a significant role in the ablation of the cornea by Erbium laser. Precise control of the fluence is required to avoid cracking phenomena in the stroma.

Aluminum Silicates↗
PubMed1996

Indocyanine green and fluorescein angiography of surgically excised macular choroidal neovascularizations: correlations with histopathologic and ultrastructural findings.

BACKGROUND: Informations are expected from the histopathological study of surgically excised choroidal neovascular membranes (CNMs), particularly in relation to the angiographic aspects of vascular architecture. METHODS: Fluorescein and indocyanine green (ICG) angiograms were studied together with the histopathological features of 12 surgically excised subfoveal CNMs in eyes affected by age-related macular degeneration (ARMD). RESULTS: Instead of the early and delayed diffuse hyperfluorescence secondary to CNMs observed on fluorescein angiography (seven were well defined, five scar evolved), ICG revealed (a) very early hypofluorescence of the membrane bulk over the fluorescence of the outer choroidal vascular bed and (b) late hyperfluorescence gradually increasing and partially defining the border of membranes. CNMs with well-defined hyperfluorescent aspects were characterized by fibrovascular bulk lined on one side by retinal pigment epithelium. Fibrosis reaction predominated over the vascular components in scar-evolved membranes. CONCLUSIONS: Fluorescein and ICG angiographic differences in the appearance of CNMs could depend on (a) the morphological structure and size of the CNM (b) its location within the chorioretinal layers and (c) different molecular characteristics of the dyes used.

Aged↗
PubMed1994

Endophotocoagulation through perfluorodecalin in rabbit eyes.

Retinal laser endophotocoagulation through perfluorodecalin was studied in six eyes of three Dutch-belted rabbits after vitrectomy. Both the energy density threshold (EDT/50) and the energy threshold necessary to obtain a therapeutic lesion were evaluated. Both argon and semiconductor diode laser endophotocoagulators were used. The amount of laser power energy and the histology of chorioretinal lesions were similar when photocoagulating through perfluorodecalin, compared to photocoagulation through balanced salt citrate-buffered solution. This experimental study indicates that no extra care is necessary when retinal endophotocoagulation is performed through perfluorodecalin, as long as circular spots are obtained and energy is delivered symmetrically to the target site.

Animals↗
PubMed1994

Corneal nerve damage and regeneration after excimer laser photokeratectomy in rabbit eyes.

PURPOSE: To investigate corneal nerve damage and its subsequent regeneration after excimer laser photokeratectomy in rabbit eyes. METHODS: Corneal photokeratectomy was performed on the right eyes of 34 pigmented rabbits, while the left eyes were used as a control. A Summit UV 200 excimer laser (Summit Technology, Waltham, MA) was used to produce a 100 microns depth phototherapeutic keratectomy (4.5 mm diameter). The rabbits were killed at 0, 1, 2, 3, 4, 5, 7, 8, 10, 15, and 20 days and 1, 2, 3, and 4 months after treatment. Corneal nerve regeneration was investigated using a monoclonal antibody directed against a 150 kD subunit of neurofilaments, in combination with acetylcholinesterase staining. RESULTS: At time 0, the subepithelial plexus had disappeared completely from the photoablated area. One day after treatment, some regenerating nerves sprouting within the treated area were visualized by a monoclonal antibody directed against a 150 kD subunit of neurofilaments. Acetylcholinesterase staining was detectable 7 days later. One month after surgery the subepithelial plexus had already reappeared, but was morphologically disorganized. Four months after treatment, the newly formed subepithelial plexus had considerably thickened in comparison with that of the control eye. CONCLUSIONS: This study shows that corneal nerve regeneration after excimer laser photoablation in rabbit eyes, although more intense, is similar to that produced after other surgical procedures involving the epithelium and the anterior stroma or one of the two.

Acetylcholinesterase↗
PubMed1985

Teaching job independence and flexibility to mentally retarded students through the use of a self-control package.

We examined mentally retarded individuals' use of picture cues and self-monitoring to initiate a series of tasks of varying type and order. Four severely to moderately retarded high school students participating in a vocational training program were trained to use a picture-cue system. The system consisted of photographs of vocational tasks that were inserted in the assigned order in a photoalbum sheet; self-management was accomplished by marking off each photo after its corresponding task was completed. Students were assigned seven tasks from a pool of 13 each day. Results indicated that the students quickly learned to use the picture-cue system to change tasks throughout their workday without trainer prompts and that performance was maintained as trainer feedback and presence were decreased. At the end of the study, two students who were exposed to novel photographs were able to initiate independently after only minimal training, suggesting that the use of the picture-cue system had become a generalized skill.

Adolescent↗
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↗