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Biomedical subjects

C A Puliafito

Publications and source records attributed to C A Puliafito.

At least 73 records · Page 4Linked to original sources
PubMed1990

Experimental use of semiconductor diode laser in contact transscleral cyclophotocoagulation in rabbits.

Acute and long-term effects of contact transscleral semiconductor diode laser cyclophotocoagulation were studied in rabbits. Immediately following cyclophotocoagulation, light microscopy revealed coagulation necrosis of the ciliary pigmented and nonpigmented epithelia and stroma; destruction increased in relation to power. There was architectural disruption with higher energy levels. The findings with diode and continuous-wave contact neodymium-YAG lasers were similar. In rabbits treated and followed up for 6 weeks there was a decrease in intraocular pressure during the observation period (P less than .05, paired Student's t test). The gross and light microscopic examination revealed focal atrophy and fibrosis of the ciliary processes, with pigment-laden macrophages on the ciliary processes and in the outflow pathways. Higher energy levels caused lens capsule damage and vitritis. The diode laser produced ciliary destruction similar to the continuous-wave contact neodymium-YAG laser in rabbits, with significant intraocular pressure lowering during the 6-week follow-up.

Animals↗
PubMed1990

Immunofluorescence study of corneal wound healing after excimer laser anterior keratectomy in the monkey eye.

We performed anterior keratectomies on six monkey eyes, four by excimer laser large-area ablation at 193 nm and two by mechanical keratectomy. Immunofluorescence was used to study the wound healing response histopathologically. The distribution of fibrinogen, fibronectin, laminin, collagen types III, IV, and VI, and keratan sulfate was determined at postoperative intervals of 24 hours, 6 days, and 1 month. At 24 hours, fibrinogen and fibronectin coated the ablated surface, but corneal epithelial cells had not yet migrated over the wound. By 6 days and persisting at 1 month, an epithelial ingrowth of seven to 10 layers, mild stromal hypercellularity, and new collagen formation were present in the repair region. At 1 month, fibrinogen, fibronectin, laminin, and type III collagen were strongly detected in the repair region. Type VI collagen was present in both normal and healed corneal stroma at all intervals, and type IV collagen was present in Descemet's membrane only. Sulfated keratan sulfate was absent from the newly synthesized collagen stroma at all intervals. Slit-lamp photographs demonstrated corneal haze in the ablation zone in all cases at 24 hours, persisting for 1 month. The fluorescence patterns produced by excimer laser ablation and mechanical keratectomy were qualitatively identical.

Animals↗
PubMed1990

Semiconductor diode laser photocoagulation in retinal vascular disease.

The authors successfully performed clinical transpupillary retinal photocoagulation in 30 eyes of 26 patients with retinal vascular disease using a gallium-aluminium-arsenide (GaAlAs) diode laser emitting at 805 nm. Retinal photocoagulation was performed at treatment powers of 300 to 1300 mW and exposure durations of 0.2 to 0.5 seconds with a 200-microns diameter treatment spot. Patients treated with both diode and argon green lasers required 4.5 +/- 1.8 times greater mean laser energy with diode compared with argon to create ophthalmoscopically similar lesions. Parallel experimental retinal photocoagulation in Chinchilla rabbits required 3.1 +/- 0.9 times more power to create ophthalmoscopically similar lesions with the diode laser than with the argon laser. Intraoperative subretinal hemorrhage occurred rarely in patients with an incidence of 4 (0.44%) of 9021 treatment spots. Patients complained of moderate-to-marked pain in 10 (43%) of 23 treatments initiated under topical anesthesia. A transpupillary diode laser may be used clinically to perform therapeutic retinal photocoagulation.

Adult↗
PubMed1990

Contact transscleral continuous wave neodymium:YAG laser cyclophotocoagulation.

Advanced glaucoma in 140 eyes of 136 patients was treated with contact transscleral continuous wave neodymium:YAG (Nd:YAG) laser cyclophotocoagulation (CYC) with a sapphire-tipped probe. The anterior edge of the probe was placed 0.5 to 1.5 mm posterior to the limbus, using 7 to 9 W of power for 0.7 seconds with 32 to 40 applications, sparing the 3 and 9 o'clock meridians. Patients were studied prospectively. The mean preoperative intraocular pressure (IOP) of 36.7 +/- 0.97 mmHg decreased to 21.2 +/- 0.99 mmHg (P = 0.004) after treatment (mean follow-up, 3.2 +/- 0.35 months) for a mean decrease in IOP of 15.5 +/- 1.21 mmHg and a mean percent decrease of 39%. Forty-one eyes were followed 6 or more months (mean, 6.7 +/- 0.25 months). The CYC reduced IOP to 25 mmHg or less in 71% of eyes, to 22 mmHg or less in 62% of eyes, and to 19 mmHg or less in 49% of eyes. Maximum lowering of IOP occurred 1 week to 1 month after treatment and remained at that level through 6 months of follow-up. Retreatment was required in 11% of patients; only one patient was retreated more than once. Four patients treated with 9 W of power developed IOPs below 5 mmHg; two of these patients had an IOP of 0 mmHg. Other complications of therapy were minimal, and patients had little pain. There was no significant change in visual acuity. Early results of this newly available therapy are encouraging.

Adolescent↗
PubMed1990

High-speed photography of Er: YAG laser ablation in fluid. Implication for laser vitreous surgery.

The mechanism of Er:YAG laser-induced long-range damage in intraocular surgery was investigated using high-speed photography. A short pulse of 2.94-microns radiation delivered by an optical fiber into an aqueous medium causes rapid localized heating and vaporization and creates a bubble at the tip of the fiber. The size of the bubble depends on the pulse energy and is about 1 mm at 1 mJ. The shape of the bubble has multiple lobes, which can be attributed to the spiky output of the laser pulse. The expanding bubble can cause thermal and mechanical damage to tissues. In addition, laser spikes propagating through the bubble can strike and damage tissue on the distal side of the bubble. In both mechanisms the damage zone approximates the bubble size and can be greater than 1 mm, ie, 1000 times the steady-state absorption length of water at 2.94 microns. The authors discuss ways to reduce the damage zone by bubble confinement.

Hot Temperature↗
PubMed1989

Nd:YAG laser photodisruption of hemorrhagic detachment of the internal limiting membrane.

We used a Q-switched Nd:YAG laser to create an opening in the internal limiting membrane in three eyes with hemorrhagic detachment of the internal limiting membrane. In all instances, after membranotomy blood was rapidly cleared from the preretinal space resulting in prompt improvement in visual acuity. No retinal injury was observed. Nd:YAG laser photodisruption may be useful in the treatment of some cases of subinternal limiting hemorrhages.

Adult↗
PubMed1989

A new model of experimental choroidal neovascularization in the rat.

Choroidal neovascularization in rat eyes was induced by krypton laser photocoagulation. Lesions were studied weekly by ophthalmoscopy, fundus photography, and fluorescein angiography. Morphologic correlation was provided by serial sectioning of lesions for light and transmission electron microscopy. In addition, vascular casts were prepared for scanning electron microscopy. Choroidal neovascularization occurred in 25 (60%) of 42 lesions, as evidenced by growth of capillaries through breaks in Bruch's membrane. In addition, 24 (28%) of 86 lesions studied by fluorescein angiography demonstrated leakage. This study provides the most complete angiographic, histologic, and ultrastructural documentation of experimental choroidal neovascularization in the rat. This model may be useful for in vivo studies of choroidal angiogenesis and its modulation via drug therapy.

Animals↗
PubMed1989

Erbium-YAG laser surgery on experimental vitreous membranes.

We used a pulsed erbium-YAG laser emitting in the midinfrared region (2.94 microns) to cut experimental vitreous membranes in rabbits via an intraocular fiberoptic delivery system. Thirty-four membranes were cut at distances of 500 to 3600 microns from the retina. All 34 of the membranes treated were effectively cut. Sixteen cases had no evidence of retinal injury, including one in which the membrane was only 800 microns from the retina. Retinal injuries in the remaining cases consisted of small (less than 300 microns) retinal burns and hemorrhages. In 94% of the cases with retinal injury, the fiberoptic was within 2000 microns of the retina. We conclude that a pulsed erbium-YAG laser allows near tractionless cutting of vitreous membranes and may have potential for clinical use if further studies show it to be efficacious and safe near the retina.

Animals↗
PubMed1989

Corneal ablation by nanosecond, picosecond, and femtosecond lasers at 532 and 625 nm.

We produced corneal excisions with nanosecond (ns)-, picosecond-, and femtosecond (fs)-pulsed lasers at visible wavelengths. The threshold energy for ablation was proportional to the square root of the pulse duration and varied from 2.5 microjoules (microJ) at 100 fs to 500 microJ at 8 ns. Excisions made with picosecond and femtosecond lasers was ultrastructurally superior to those made with nanosecond lasers and, at pulse energies near threshold, showed almost as little tissue damage as excisions made with excimer lasers at 193 nm. We conclude that ultrashort-pulsed lasers at visible and near-infrared wavelengths are a possible alternative to excimer lasers for corneal surgery and might have advantages over conventional ophthalmic neodymium-YAG lasers for some intraocular applications.

Animals↗
PubMed1989

Photodynamic therapy for experimental intraocular melanoma using chloroaluminum sulfonated phthalocyanine.

Chloroaluminum sulfonated phthalocyanine (CASPc), a novel photosensitizing dye, was evaluated for treatment of experimental intraocular melanoma in 33 rabbit eyes. An argon ion pumped dye laser, operating at an emission of 675 nm, was used in a nonthermal mode to irradiate iris tumors in rabbits 24 hours after they received in intravenous dye injection (23 eyes). The effects of laser irradiation alone and dye alone were examined in ten control eyes. A threshold tumoricidal dose was established for photodynamic therapy with CASPc and laser irradiation. Vascular occlusion was produced in a well-circumscribed area corresponding to the boundaries of laser irradiation after CASPc injection. Tumors successfully treated with CASPc and laser irradiation were arrested in growth and exhibited no viable tumor cells on histologic examination. Control tumors continued rapid growth, unaffected by dye or laser. Our data indicate that CASPc demonstrates a strong photosensitizing effect on both tumor and normal tissue. These results suggest that CASPc is a potential photosensitizing compound that may be useful in the treatment of choroidal melanoma.

Animals↗
PubMed1989

Picosecond optical breakdown: tissue effects and reduction of collateral damage.

The effects of picosecond laser-induced optical breakdown on tissue were investigated using high-intensity 40 ps Nd:YAG laser pulses at 1.06 microns. Tissue damage was evaluated using the corneal endothelium in vitro as a model system. Systematic studies were performed to determine the scaling of the tissue damage and damage range with pulse energy. For suprathreshold lesions, the radius of the damage zone varies as the cube root of the pulse energy, in agreement with simple physical scaling laws. A minimum damage range of less than 100 microns was observed for pulse energies of 8 muJ. Damage morphology was investigated by scanning electron microscopy. Three different damage patterns were observed; cell damage, cell removal, and rupture of Descemet's membrane. Different irradiation geometries were used to study damage mediated by either the shock wave or the cavitation bubble. Comparative studies using 10 ns pulses demonstrated that picosecond pulses yielded a significant reduction in collateral tissue damage.

Animals↗