摘要:

This study examines corneal ablations produced by the neodymium doped yttrium-lithium-fluoride (Nd:YLF) picosecond laser. The laser delivers a 1-KHz, 40-ps pulsed, 1,053-nm wavelength beam (with energy measured in microjoules) to a 15-$mUm diameter spot size. The ablation mechanism is by plasma formation, which generates acoustic shock waves. Using enucleated rabbit (n = 25) and human donor eyes (n = 29), corneas were examined after tissue ablation at energies ranging from 40 to 300 $mUJ per pulse with various programmed ablation depths and patterns. The histologic data were collected using light microscopy and transmission electron microscopy. The tissue effects and Nd:YLF laser functions studied were ablation thresholds, cutting ability, programmed ablation depth accuracy, and acute endothelial effects. Our study showed histologic ablation thresholds for the following human corneal layers: epithelium = 7.15 ± 0.05 × 1011W/cm2(34.1 ± 8.1 J/cm2per pulse, 50 $mUJ per pulse); Bowman's layer = 1.33 ± 0.29 × 1012W/cm2(58.5 ± 3.3 J/cm2per pulse, 100–110 $mUJ per pulse); stroma and endothelium = 7.10 ± 1011W/cm2(28.4 J/cm2per pulse, 50 $mUJ per pulse). Depth of corneal ablation was found to be directly related to energy and independent of programmed ablation depth. This study shows the endothelial loss in rabbit corneas by energy beams (50 $mUJ per pulse) focused 100 $mUm from this layer.

ISSN:0277-3740    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

This study examines the structural changes in cornea resulting from plasma formation and propagated acoustic shock waves produced by the neodymium doped yttrium-lithium-fluoride (Nd:YLF) picosecond laser. Human donor eyes and enucleated rabbit eyes were subjected to various ablation patterns at energies ranging from 40 to 300 $mUJ per pulse. Two distinctly different patterns were produced depending on the location of initial plasma formation. Plasmas initiated at the corneal surface produced smooth, straight-edged ablations of corneal tissue that consisted of collagen fibril fragmentation, fibril organizational disruption, and possible thermal effect observed along the lateral borders and wound apex. The extent of lateral damage was directly related to the energy applied. The range of acute collagen disorganization observed at the ablation edge in rabbit corneas at various pulsed energies was as follows: 50 $mUJ = 1.0–12 $mUm, 150 $mUJ = 3.8–12.5 $mUm, 250 $mUJ = 6.2–23.7 $mUm, and 300 $mUJ = 7.5–45.0 $mUm. Plasma formation initiated within the stroma at or above threshold energies (50–150 $mUJ per pulse) produced an inter- or intralamellar separation effect with little evidence of ablation or collagen fibril fragmentation. Intrastromal plasmas generated from higher energies (200–300 $mUJ per pulse) produced tissue ablation, along with ablation or disruption of tissue anterior to the intrastromal target area.

ISSN:0277-3740    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

The purpose of this study was to determine whether the DNA of mitotic cells in the corneal and conjunctival epithelium can be labeled with 5-bromo-2-deoxyuridine (BrdU) immunostaining. Both corneas of four New Zealand white rabbits were deepithelialized in the center and the regenerated epithelium was evaluated for mitosis at 1, 3, 6, and 10 days. Unwounded corneas of three rabbits were labeled for baseline measurements. We administered the marker intravenously to all seven rabbits 15 h before scheduled killing. Immediately after killing, all of the globes were enucleated and histologic sections were prepared. In unwounded corneas, labeled cells were quantitated and the fraction of mitotic cells in the center of the cornea, in the periphery of the cornea, and in the conjunctiva were compared. In deepithelialized corneas, increase in mitosis in the central epithelium was quantitated. All of the unwounded eyes showed mitosis in the basal layer of both the corneal and conjunctival epithelium. In the center of the cornea 4.1 ± 2.9% of the epithelial cells were labeled, in the corneal periphery 4.3 ± 1.7% of the cells were labeled, and in the conjunctiva 4.1 ± 1.9% of the epithelial cells were labeled, with a p value ranging from 0.84 to 0.99. In wounded corneas, when compared with cell counts in unwounded eyes, 52.6% of the epithelial cells were in mitosis on day 3, 13.9% were in mitosis on day 6, and by day 10 baseline values of 4.2% were obtained. We conclude that BrdU immunostaining is a safe, efficient, and less costly alternative to autoradiography for visualization of dividing corneal and conjunctival epithelium.

ISSN:0277-3740    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

The protective effects of oxidized glutathione (GSSG) and reduced glutathione (GSH) in the irrigating solution based on BSS plus composition (Santen, Osaka, Japan), which is without GSSG (glutathione-free control solution) were compared on rabbit corneal endothelial barrier function. Corneal barrier function was evaluated by determining the effects of GSSG and GSH on carboxyfluorescein permeability (Pac). In a solution containing 0.3 mM GSSG (BSS plus), the Pacwas significantly inferior to that of its paired glutathione-free control solution. With 0.6 mM GSH, the Pacwas not different from that of its paired glutathione-free control solution. The Pacof the endothelium with 0.3 mM GSSG was significantly inferior to that of paired corneas exposed isolated to 0.6 mM GSH. These results show that the barrier function of the rabbit corneal endothelium is better maintained by supplementing the perfusion solution with 0.3 mM GSSG rather than 0.6 mM GSH.

ISSN:0277-3740    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

An open-label study of 20 normal, healthy volunteers was conducted to determine the tear concentrations after topical ocular application of ciprofloxacin 0.3% ophthalmic solution (Ciloxan). Tear samples were collected on Schirmer tear strips at 30 min, 2, 3, and 4 h, and were analyzed for ciprofloxacin using reverse-phase high-performance liquid chromatography. The results of this study showed the mean concentration, 4 h after dosing of ciprofloxacin, to be 16.0 $mUg/ml with 95% confidence limits of 8.15 and 23.79. It is concluded that concentrations of ciprofloxacin in tears were significantly greater than the minimum inhibitory concentrations for 90% of strains tested commonly reported for a majority of potential pathogens (i.e., ≤2 $mU/ml) 4 h after a single application of ciprofloxacin ophthalmic solution 0.3%.

ISSN:0277-3740    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

We evaluated the efficacy of topical ciprofloxacin (3.0 mg/ml) in the treatment of experimental Pseudomonas aeruginosa keratitis in 60 rabbits. We compared ciprofloxacin treatment with double drug therapy consisting of tobramycin (13.6 mg/ml) plus polymyxin B (25,000 U/ml) or carbenicillin (6 mg/L). Two strains of P. aeruginosa were used. One was a strain well characterized for use in experimental Pseudomonas keratitis (ATCC organism 27853); the second was an organism from a patient with a Pseudomonas corneal ulcer. Rabbits were treated for 16 h, after which the corneas were excised, homogenized, and plated serially for residual colony-forming units. Both organisms responded significantly better to topical off-the-shelf ciprofloxacin than to therapy with two conventional antipseudomonal fortified antibiotic drugs (p =s 0.0001).

ISSN:0277-3740    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

We compared measurement of lactoferrin concentration by the Lacto Card solid phase ELIA assay with the Lac-toPlate radial immunodiffusion assay in tears of normal patients and those with keratoconjunctivitis sicca. The Lacto Card, a new lactoferrin assay, allows rapid determination of tear lactoferrin concentration in 10–15 min, a notable improvement over the 3 days required of the Lac-toPlate. There was no statistically significant difference between the accuracy of the two assays in normal patients nor in those patients with a diagnosis of keratoconjunctivitis sicca. Both assays showed a significant decrease in tear lactoferrin concentration in patients with severe keratoconjunctivitis sicca when compared to normal patients. The Lacto Card is a rapid and reliable means of measuring tear lactoferrin concentration in a clinical setting.

ISSN:0277-3740    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Posterior polymorphous corneal dystrophy (PPD) is a rare bilateral, autosomal-dominant disease. The presence of the epitheliumlike endothelium and the thickening of Descemet's membrane by the posterior collagenous layer (PCL) has been reported in the majority of published cases. Reepithelialization of the posterior cornea in donor tissue has been reported only once. Therefore, to examine this process we examined, by light and electron microscopy, three corneal buttons (an original and two subsequent keratoplasties after 3 and 4 years, respectively) from the left eye of a patient with bilateral disease. Our study showed a repopulation of the posterior surface of the donor corneas by the host epitheliumlike endothelium, which was of identical morphology in each case. In contrast to the previously published work, a posterior collagenous layer in the failed grafts was absent from the axial cornea, where the epitheliumlike endothelium was in direct contact with donor Descemet's membrane. A PCL at the periphery in the failed transplants was of the fibrocellular type and differed from the fibrillar PCL in the first keratoplasty specimen. The fibroblastlike cells within the fibrocellular PCL were distinct from the underlying epithelial-like cells and contained numerous tertiary phagolysosomes. We suggest that the major contributor to the fibrocellular PCL in the repeat keratoplasties was a fibrous ingrowth from the host/graft junction and not the epitheliumlike endothelium. It appears that the synthetic capacity of the epitheliumlike endothelium was similar to that of the normal epithelium and was much lower than that of normal native endothelium.

ISSN:0277-3740    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Previously, we demonstrated that HPMPC, a new, broad-spectrum antiviral agent, inhibited adenovirus type 5 in the New Zealand (NZ) rabbit ocular model (Cornea 1992; 11:529–33). Historically, no antiviral agent has been demonstrated to be effective against both herpes simplex virus type 1 (HSV-1) and adenovirus eye infections in an experimental animal model. In this study, we compared topical 0.2% HPMPC to 1% trifluridine and vehicle control in the NZ rabbit HSV-1 keratitis model. Using a double-masked, two-eye design, NZ rabbits were inoculated in both eyes with HSV-1 W strain (105pfu/eye), and dendritic keratitis and HSV-1 ocular titers were measured serially. Compared with the control group, both topical 0.2% HPMPC and 1% trifluridine significantly reduced healing time of HSV-1 dendritic keratitis, lowered HSV-1 ocular titers on days 3 through 11, and shortened duration of HSV-1 shedding in the tear film. For all outcome parameters measured, topical 0.2% HPMPC was as effective as 1% trifluridine. A new concept of a broad-spectrum topical antiviral agent was shown to be effective against HSV-1 in an NZ rabbit keratitis model, and further development toward clinical application appears desirable.

ISSN:0277-3740    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

The efficacy of corneal transplantation in infants with corneal opacity secondary to congenital glaucoma has not been established. We retrospectively reviewed our results of nine penetrating keratoplasties performed on eight eyes of six infants who had multiple risk factors for poor prognosis: age <2 years at the time of grafting; uncontrolled glaucoma in four eyes; concurrent lensectomy, retinal, or glaucoma surgery in five eyes; aphakia in five eyes; and an acute perforation in one eye. Six of the nine grafts (67%) remained clear during a mean follow-up of 24 months (30 months in eyes with clear grafts). Development of ambulatory vision or better occurred in six of eight (75%) eyes after corneal transplantation and treatment of refractive errors and amblyopia. Graft failure occurred in three eyes—two from corneal decompensation, and one from homograft rejection. Complications included one total retinal detachment, one case of Streptococcus pneumoniae keratitis, and three cases that lost intraocular pressure control, requiring further glaucoma surgery. We conclude that useful vision can be achieved after penetrating keratoplasty even in some high-risk infants with congenital glaucoma.

ISSN:0277-3740    

出版商:OVID    

年代:1994

数据来源: OVID