Indications for Q-switched and mode-locked Nd: YAG lasers in vitreoretinal pathology.

The indications for two types of pulsed Nd: YAG lasers in the treatment of vitreous pathology are reviewed. A series of 94 eyes from 93 patients were treated with the mode-locked system and 72 eyes from 71 patients were treated with the Q-switched system. A classification of vitreous pathology with prognostic value for the efficacy of treatment of both lasers is established. For the Q-switched laser the range of indications in the posterior pole is larger and fewer sessions are needed; however, complications are more frequent than with the mode-locked laser. This difference is due to the higher energy needed with the Q-switched laser to treat more severe vitreous pathology.

Gamma-aminobutyric acid (GABA) immunocytochemistry of laser coagulations in the rabbit retina.

Rabbit retinas were treated with laser coagulations of low intensity, using five different wavelengths. After coagulation (1, 4 and 28 days), the retinas were stained for GABA, using a direct biotin-avidin-horseradish peroxidase immunocytochemical method. These time intervals were chosen with regard to the existing knowledge of retinal repair. The staining for GABA was increased in the inner plexiform layer at the centre of the lesions at days 1 and 4 after coagulation. At the margins of the lesions, cells in the ganglion cell layer showed strong staining and cells in the amacrine cell layer showed cuffing, independent of the wavelength used. On day 28, a regression of the hyperstaining was noted. Some possible pathophysiological mechanisms are discussed.

The effect of wavelength on glial fibrillary acidic protein immunoreactivity in laser-induced lesions in rabbit retina.

Rabbit retinas were treated with low-intensity laser coagulation at five different wavelengths. Using an indirect immunocytochemical method, the retinas were stained for glial fibrillary acidic protein (GFAP) at 2, 4, 21 and 32 days after coagulation such that we could follow GFAP expression in the Müller cells during retinal repair. GFAP-positive staining was found in the end feet of the Müller cells at 2 days after laser coagulation. GFAP immunoreactivity was observed throughout the Müller cells, surrounding the central necrotic tissue, at days 4, 21 and 32 after laser coagulation. Scar tissue in the subretinal space at days 21 and 32, which was more pronounced for the longer wavelengths produced by the Krypton and Nd-YAG lasers, also showed GFAP immunoreactivity. The Müller cells remained GFAP-immunoreactive for at least 32 days after laser coagulation.

[Tolosa-Hunt syndrome: current clinical and electrophysiologic evaluation]. / Le syndrome de Tolosa-Hunt: évaluation actuelle clinique et électrophysiologique.

Three patients with Tolosa-Hunt syndrome were reported. All clinical investigations were negative in two of them, apart from the orbital venography, which showed on the affected side, an obstruction of the superior ophthalmic vein in its third segment. In the third case, early subclinical optic nerve involvement were demonstrated and followed up by visual evoked responses to checker-board pattern stimuli.

[Efficacy of treatments in experimental toxoplasmosis]. / Etude de l'efficacité des traitements dans la toxoplasmose expérimentale.

Experimental study of the intraocular penetration of six drugs with therapeutic effect on toxoplasma. A direct and an indirect method are used. The penetration of six drugs administered sub-conjunctival, retrobulbar and intramuscular in one shot is measured in the anterior chamber, the vitreous and the retina-choroid of a healthy rabbit eye. The best results are obtained for: spiramycin, trimethoprim-sulfamethoxazole and clindamycin. The therapeutic efficiency of four drugs on infected rabbit eyes with toxoplasma are studied using an indirect method: pyrimethamine and especially doxycycline have a positive effect.

Nd-YAG laser treatment in preretinal macular fibrosis.

Three eyes with preretinal macular fibrosis (PMF) were treated with the Q-switched Nd-YAG laser. The PMF was idiopathic in two eyes and associated with a vitreous hemorrhage, due to ocular trauma, in the third eye. The three eyes had in common a partial posterior vitreous detachment with vitreous traction on the macula. The Nd-YAG laser beam was focused on the detached posterior hyaloid in front of the macular region. Some holes were made in this membrane or in the adjacent collapsed vitreous cortex. Treatment increased the visual acuity in the three eyes; the vitreous remained partially detached in the two eyes with idiopathic PMF and detached completely in the eye with the secondary PMF. The disentanglement of the fovelar area was revealed by the unfolded appearance of the retinal vessels on fluoangiography.

Neodymium YAG laser effects on rabbit lenses. A scanning electron microscopic investigation using Q-switched and mode-locked lasers.

The immediate and long-term effects of Q-switched and mode-locked neodymium (Nd) yttrium-aluminum-garnet (YAG) lasers on the fine structure of lens fibers were studied with stereomicroscopic and scanning electron microscopic methods. This study shows that both laser systems produced very restricted lesions that, at a 1-h survival time, were characterized by an empty central hole surrounded by a thin amorphous wall. Fibers adjacent to the hole looked normal, apart from some compression in the immediate vicinity of the hole. At medium and long-term survival times the empty bubbles now appeared to be filled with a crystal-clear amorphous mass. The wall surrounding the empty lesions had disappeared, and at medium survival times adjacent fibers incidentally showed fiber alterations like local swellings and microplicae. At 180 days the fibers surrounding the central mass showed numerous swellings, microplicae and confluence of fibers. These fiber alterations are also seen in different types of cataracts. Thus, short-pulsed laser lesions may act as cataractogenic centers.

[Argon laser treatment of the iris: an experimental study (author's transl)]. / Behandlung der Iris mit Argonlaserstrahlen. Experimentelle Studien.

Description of various affections of the iris which may be treated with argon-laser. The problem of the laser iridectomy in the treatment of glaucoma is illustrated by a histologic study of the evolution of the lesions up to four months after coagulation of rabbit's iris.