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Biomedical subjects

C A Puliafito

Publications and source records attributed to C A Puliafito.

At least 19 recordsLinked to original sources
PubMed1992

Mid-infrared laser ablation of the cornea: a comparative study.

The ablation thresholds and patterns of collateral damage in cornea produced by Er:YAG (2.94 microns) and Er:YSGG (2.79 microns) lasers were measured. Two different pulse durations, 200 microseconds (normal spiking mode) and 100 ns (Q-switched mode), were used at both wavelengths. In the normal spiking mode, damage zones of 16 +/- 2 microns and 39 +/- 7 microns and ablation thresholds of 250 +/- 20 mJ/cm2 and 420 +/- 35 mJ/cm2 were measured at 2.94 microns and 2.79 microns, respectively. In the Q-switched mode, damage zones of 4 +/- 2 microns and ablation thresholds of 150 +/- 10 mJ/cm2 were found irrespective of the laser used. The similarity between the results using the Er:YAG and Er:YSGG lasers in the Q-switched mode suggest that either laser can be used with equal effectiveness for corneal trephination.

Animals↗
PubMed1992

Contact transscleral Nd:YAG laser cyclophotocoagulation. Midterm results.

BACKGROUND: Early reports of both contact and noncontact transscleral Nd:YAG laser cyclophotocoagulation have been encouraging; however, recent evidence indicates a significant incidence of hypotony, visual loss, and phthisis with the noncontact technique with more than 6 months of follow-up. The authors sought to determine the intermediate term effects of contact transscleral Nd:YAG laser cyclophotocoagulation (CYC). METHODS: The authors followed 116 eyes of 114 patients for a minimum of 1 year after treatment of advanced glaucoma with CYC. RESULTS: The mean preoperative intraocular pressure (IOP) of 35.0 +/- 1.0 mmHg decreased to 18.6 +/- 1.1 mmHg (P less than 0.0001) during the average follow-up of 19.0 +/- 0.6 months (range, 12 to 36 months). Intraocular pressure control of 3 to 25 mmHg was achieved in 72%, 3 to 22 mmHg in 65%, and 3 to 19 mmHg in 56% of eyes. Retreatment was required in 31 of the 116 eyes (27%). Intraocular pressure decreased to less than 3 mmHg in 9 eyes and to 0 mmHg in 6 of these 9 eyes. Nineteen eyes, all with initial visual acuity of counting fingers or worse, progressed to no light perception; 17 of 36 eyes (47%) with visual acuity of 20/200 or better lost 2 or more Snellen lines. CONCLUSION: Midterm results of CYC continue to be encouraging but are tempered by a nearly 10% incidence of hypotony or phthisis and the progression of visual loss.

Adolescent↗
PubMed1992

Digital indocyanine-green angiography in chorioretinal disorders.

The authors performed digital indocyanine-green angiography in 37 patients with chorioretinal disorders. Eighteen patients had choroidal neovascularization, 7 patients had atrophic age-related maculopathy, and 12 patients had uncommon choroidal and retinal disorders. A Topcon indocyanine-green camera was integrated with a digital (1024-line resolution) angiography system. Compared with conventional video or photographic indocyanine-green angiography, this technique offers enhanced image resolution, the possibility of direct qualitative comparison with fluorescein angiography, image archiving, hard-copy generation, and tracing capabilities to plan laser treatment strategies and monitor the adequacy of laser therapy after surgery.

Choroid Diseases↗
PubMed1991

Optical coherence tomography.

A technique called optical coherence tomography (OCT) has been developed for noninvasive cross-sectional imaging in biological systems. OCT uses low-coherence interferometry to produce a two-dimensional image of optical scattering from internal tissue microstructures in a way that is analogous to ultrasonic pulse-echo imaging. OCT has longitudinal and lateral spatial resolutions of a few micrometers and can detect reflected signals as small as approximately 10(-10) of the incident optical power. Tomographic imaging is demonstrated in vitro in the peripapillary area of the retina and in the coronary artery, two clinically relevant examples that are representative of transparent and turbid media, respectively.

Coronary Disease↗
PubMed1991

Cystoid macular edema, retinal detachment, and glaucoma after Nd:YAG laser posterior capsulotomy.

A series of 897 Nd:YAG laser posterior capsulotomies were reviewed for the complications of cystoid macular edema, retinal detachment, new onset of glaucoma, and worsened preexisting glaucoma. After Nd:YAG capsulotomy, 11 patients (1.23%; 95% confidence interval, 0.51% to 1.95%) developed cystoid macular edema and eight patients (0.89%; 95% confidence interval, 0.28% to 1.5%) developed a retinal detachment. The new onset of glaucoma was observed in seven patients (0.78%; 95% confidence interval, 0.20% to 1.36%). Five patients (0.56%; 95% confidence interval, 0.07% to 1.05%) with preexisting glaucoma had persistent worsening of their glaucoma. Most patients with a complication had no identifiable risk factors in common. The numbers of laser pulses and energy delivered were not risk factors. Retinal detachment and cystoid macular edema developed most often many months after capsulotomy and many months to years after the cataract surgery. Patients undergoing Nd:YAG laser capsulotomy therefore require ongoing medical observation to detect and treat these serious complications.

Cataract Extraction↗
PubMed1991

Retinal manifestations of neurofibromatosis. Diagnosis and management.

Five patients presented with vision-threatening retinal tumors and systemic signs of neurofibromatosis, including neurofibromatosis type 1 (four patients) and familial cafe-au-lait spots (one patient). These tumors included large retinal astrocytic hamartomas, multiple retinal capillary hemangiomas, and combined hamartomas of the retina and retinal pigment epithelium, which resulted in rubeotic glaucoma, vitreous hemorrhage, and retinal detachment. Surgical therapy included retinal cryopexy, xenon and argon photocoagulation, scleral buckling, and pars plana vitrectomy with excisional retinal biopsy. Retinal tumors may result in marked visual loss in patients with neurofibromatosis, and vitreoretinal surgery may restore useful vision in some of these patients.

Adolescent↗
PubMed1991

A comparative study of masking fluids for excimer laser phototherapeutic keratectomy.

Several fluids of different viscosity were used to mask deeper tissues while exposing protruding irregularities during therapeutic keratectomy of an irregular anterior corneal surface with the 193-nm argon fluoride excimer laser. A model of an irregular anterior corneal surface was developed in deepithelialized calf eyes using grade 8-0 sandpaper. Therapeutic keratectomy was then performed on 28 eyes at a fluence of 180 mJ/cm2, a repetition rate of 10 Hz, and 500 pulses per eye. Solutions of 0.3% hydroxypropylmethylcellulose 2910 and a 0.1% dextran 70 solution, 1% carboxymethylcellulose sodium solution, or 0.9% saline solution were applied to the corneal surface of 21 eyes. Seven control eyes underwent ablation without the addition of fluid. Scanning electron microscopy demonstrated that corneas treated with dextran 70 had the least surface irregularity, and those treated with carboxymethylcellulose or saline solution had intermediate surface irregularity. Corneas that were ablated without additional fluid had the greatest surface irregularity. The application of a moderately viscous solution during therapeutic excimer laser keratectomy enhances the smoothing effect of surface ablation.

Animals↗
PubMed1991

Energy levels and probe placement in contact transscleral semiconductor diode laser cyclophotocoagulation in human cadaver eyes.

We investigated the effects of semiconductor diode laser contact transscleral cyclophotocoagulation in human cadaver eyes by gross examination, light microscopy, and scanning electron microscopy to determine optimum clinical treatment parameters. Irradiation was performed using a continuous-wave semiconductor diode laser with a fiber-optic probe. At 1.0 to 1.25 mm posterior to the limbus, spots were centered on the pars plicata by gross examination. Exposures of less than 2 J produced no visible damage. A 2- to 3-J exposure produced mild whitening of the ciliary processes, while 4- to 5-J exposures created more intense whitening of the pars plicata. Energies higher than 5 J frequently produced explosive tissue damage. Light microscopy of tissue treated with 1.8 to 6 J at 1.0 to 1.25 mm posterior to the limbus revealed coagulation necrosis of the nonpigmented and pigmented epithelium, with evidence of thermal coagulation of the ciliary stroma and stromal vasculature. Coagulation necrosis was more intense with longer exposure times. We found the optimum parameters for contact transscleral diode laser cyclophotocoagulation in cadaver eyes to be 3 to 4.5 J of energy delivered with the anterior edge of the probe 1.0 to 1.25 mm posterior to the limbus.

Ciliary Body↗
PubMed1991

Holmium-YAG laser surgery on experimental vitreous membranes.

We used a pulsed holmium-YAG laser that emitted in the midinfrared (2.12 microns) to cut experimental vitreous membranes in rabbits via an intraocular fiberoptic delivery system. Thirty-five membranes were treated at distances of 0.5 to 3.8 mm from the retina. All of the membranes that were treated were transected or partially cut. In cases that were treated with the optical fiber encased in a retinal-shielding pick, membranes could be readily transected without retinal injury. Laser vitreous membrane cutting may offer the advantage of near-tractionless membrane segmentation. The combination of a moderately strong target tissue absorption and the ready availability of commercial optical fibers for transmission of 2.12-microns laser energy suggests that the holmium-YAG laser merits further investigation for this application.

Animals↗
PubMed1991

Micron-resolution ranging of cornea anterior chamber by optical reflectometry.

Noncontact, high resolution measurements of anterior eye structures using optical coherence domain reflectometry are described. Distances between intraocular structures are measured by directing a beam of short coherence length light onto the eye and performing an interferometric measurement on the optical group delay of reflected signals. Measurements of corneal thickness, corneal excision depth, and anterior chamber depth are demonstrated in vitro, and the location of tissue boundaries is resolved to within +/- 2 microns. The full-width-half-maximum longitudinal resolution is 10 microns. Sensitivities to reflected signals as small as 10(-10) of the incident power are achieved by heterodyne detection.

Animals↗
PubMed1991

Phthalocyanine photodynamic therapy of experimental iris neovascularization.

Photodynamic therapy using chloroaluminum sulfonated phthalocyanine (CASPc) effectively closed experimental iris neovascularization induced in 6 eyes of cynomolgus monkeys by argon laser retinal vein occlusion. Neovascularization was followed by iris photography, fluorescein angiography, and histopathologic examination by light and electron microscopy. Intravenous injection of CASPc followed by irradiation with 675 nm light damaged endothelial cells and pericytes, leading to exposure of the basal lamina and thrombotic occlusion of the blood vessels. Surrounding tissue appeared preserved without evidence of thermal damage. Resorption of occluded vessels by macrophages began 2 to 3 days after photodynamic therapy. Neovascularization reappeared 7 days after photodynamic therapy, probably representing growth of new vessels. Photodynamic therapy with CASPc may be a useful adjunct in the treatment of iris neovascularization. The model is useful in elucidating the ultrastructural changes observed after photodynamic therapy using phthalocyanines.

Aluminum↗
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↗