摘要:

1 year retrospectively. The overall graft survival was 95.3%. The graft was thick in the early postoperative period. It subsequently became thinner, reaching the lowest level 5-9 months postoperatively (mean 0.48 mm, SD 0.04). After this period the corneas gradually became thicker and reached the normal corneal thickness. The extreme thinning of transplanted corneas in the first postoperative year has not been described before. We found a negative correlation between conservation time and thickness 5-9 months postoperatively. We postulate that organ culture may have a high impact on keratocyte function.

ISSN:0277-3740    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

We reviewed the pattern of astigmatism after penetrating keratoplasty and transsclerally sutured posterior chamber lens (TSPCL) placement in 73 patients. Thirty-five patients (48%) had an axis of astigmatism oriented perpendicularly to the haptics of the TSPCL. Twenty-seven patients (37%) had an orientation of astigmatism that was in the same meridian as the haptics of the TSPCL. Eleven patients (15%) had an axis of astigmatism oriented obliquely to the meridian of the haptics of the TSPCL. The distance the haptic fixation sutures were placed behind the limbus appeared to be correlated with the orientation of astigmatism. Patients having the lens fixated within 0.75 mm of the limbus were more likely to have astigmatism oriented perpendicular to the meridian of the haptics of the posterior chamber lens in the early postoperative period. Patients having the lens fixated 2-3 mm posterior to the limbus were more likely to have astigmatism oriented in the same meridian as the haptics of the posterior chamber lens in the early postoperative period. In an eye bank model of TSPCLs during penetrating keratoplasty, the placement of a posterior chamber lens with haptics fixated within 0.75 mm of the limbus significantly widens the recipient bed an average of 0.3 mm in the meridian of the haptics of lens placement (p=0.02). When the posterior chamber lens haptics were fixated 3 mm posterior to the limbus, the recipient bed was significantly narrowed in the meridian of lens placement an average of 0.2 mm (p=0.02). It appears that the TSPCLs may have an effect on early postkeratoplasty astigmatism by distorting the corneal wound at the time of keratoplasty.

ISSN:0277-3740    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

The Janus green photometric technique and the Mosmann's colorimetric MTT-assay to quantify corneal endothelial cytotoxicity were compared. Detergents, studied before by in vitro corneal perfusion, proved to be toxic at the 1% level in the Janus green assay with human corneas and at the 0.4% level in the MTT-assay with bovine endothelial cells. These results correlated well with earlier findings in vitro and in vivo. The use of human corneas reduced the ability of the Janus green photometric technique as a fast screening method because of the heterogeneity and restricted availability of this tissue. With the MTT-assay, large test series could be performed at the same time using cultured cells. Both assays are good tools to screen the cytotoxicity of chemicals and reduce the number of animals needed for endothelial cytotoxicity testing.

ISSN:0277-3740    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

An investigation was made on the possible effects of high levels (450 mg/dl) of glucose on the activities of Na, K-ATPase [E.C. (Enzyme Commission) 3.6.1.37] and Mg- ATPase (E.C. 3.6.1.4) in plasma membrane preparations of bovine corneal endothelial cells grown in tissue culture. The activities of these enzymes were compared with the activities of the same enzymes from cells grown in low or "fasting" levels (90 mg/dl) of glucose. All activities were assayed from cells that were secondary cultures (15-25 days after trypsinization). The results indicated a 76% decrease in activity for Na,K-ATPase (0.04 units in high glucose vs. 0.17 units in low glucose). The activity for Mg-ATPase also decreased by 33% (0.24 units in high glucose vs. 0.36 units in low glucose). A t-test for significance indicated that the loss of activity in both enzymes was highly significant (p<0.001) in the high glucose media. Assays for ATPase activity of plasma membranes were also made directly in high glucose after removal of the membranes from cells grown in low-glucose media. However, those membrane ATPases showed no significant decrease in activity. Tests for DNA damage of cells grown in the presence of high levels of glucose indicated a 15.5% change (decrease) in the amount of double stranded DNA remaining after alkali treatment. This change was highly significant also (p<0.001). These data suggest that the diabetic state may negatively affect membrane- bound ATPases of the corneal endothelium and further point to the possibility of an altered synthetic rate of ATPase polypeptides as a result of DNA damage.

ISSN:0277-3740    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

For the same diamond blade extension, uphill (centripetal) radial keratotomy incision direction achieves greater depth and consequently greater refractive effect than downhill (centrifugal) incisions. To determine which factors may account for this difference, two uphill and two downhill incisions were made with a double-edged diamond blade set to 90% central pachometry in 26 human donor eyes at 15 or 60 mm Hg. Uphill incisions made with the perpendicular blade had greater mean incision depth than downhill incisions made with the oblique blade at 15 mm Hg (83.6 ± 3.9% and 68.2 ± 5.2%) (p<0.0005) and at 60 mm Hg (86.3 ± 3.1% and 79.7 ± 1.7%) (p<0.0005). Uphill and downhill incisions both made with the perpendicular blade had equal depth (85.4 ± 4.9% and 83.7 ± 3.5%) (p>0.1). The perpendicular blade edge created a straight, and the oblique edge an S- or J-shaped, histological incision configuration. Corneal profile pictures taken during each incision showed the knife to tilt opposite of the incision direction and to move at a constant angle to the limbal plane, producing a smaller optical clear zone (OCZ) in the posterior stroma than intended with uphill incisions. Greater refractive effect with uphill incisions may be explained by the perpendicular blade being more effective in incising corneal lamellae, and the creation of a smaller posterior OCZ. Intraocular pressure variations during surgery may affect achieved incision depth of downhill, but not of uphill, incisions.

ISSN:0277-3740    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Previously we have reported that various pathologic corneas exhibited a "diseased" two-band corneal aldehyde dehydrogenase (ALDH) zymogram after native polyacrylamide gel electrophoresis as compared with the three bands in the normal human cornea. Experimentally, such a "diseased" zymogram pattern could be induced by addition of reduced glutathione (GSH) to the normal corneal epithelial extract. This finding suggests that in vivo the conformation of corneal ALDH may be related to changes in the GSH redox system during the process of corneal diseases. To investigate this hypothesis in keratoconus corneal epithelial extracts and a separate group comprising other corneal disorders, mainly herpes keratitis, we indirectly measured the GSH turnover by assaying the activity of glutathione reductase (GR) which is responsible in producing GSH and glutathione s-transferase (GST), which converts GSH into mercapturic acid. Our results indicate that there is a correlation between the activity of GR and GST in the normal and the separate group of corneal disorders. Because GST is the first enzyme in the mercapturic acid pathway, which detoxifies xenobiotic substrates including aldehydes, as by-products of membrane lipid peroxidation, an elevated GSH turnover might be necessary to counteract oxidative threats. However, no correlation was found between corneal ALDH level with either GR or GST. On the other hand, keratoconus samples demonstrated a distinct enzymatic behavior that was in concordance with our earlier result in the corneal ALDH zymogram after isoelectric focusing. Furthermore, analysis of our several studies tends to support the proposed structural function of ALDH in human cornea.

ISSN:0277-3740    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

This trial was a randomized, double-masked, crossover study during which patients with keratoconjunctivitis sicca underwent 6 weeks of treatment with either cyclosporine 1% ophthalmic ointment or placebo followed by 6 weeks of the alternative treatment. Washout periods using only unpreserved artificial tears preceded both treatment cycles. Twenty-five patients completed the first treatment period, but only eight met entry criteria for period II. Cyclosporine ointment was associated with initial mild to moderate redness, itching, and burning that returned to baseline levels within 1-2 weeks. Rose Bengal results and results of four subjective (patient diary) efficacy parameters favored cyclosporine: foreign body sensation, overall symptoms, hours of symptom control per day, and overall effectiveness. No systemic adverse events or laboratory abnormalities occurred. We conclude that (a) the crossover design is inappropriate for studying this disease; (b) mild to moderate itching, redness, and burning occur initially with cyclosporine administration, although tolerance quickly develops; (c) cyclosporine appears to benefit the ocular surface in keratoconjunctivitis sicca; and (d) further trials in this syndrome are warranted.

ISSN:0277-3740    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Between May 1983 and December 1989, 2,921 donor eyes received by the Minnesota Lions Eye Bank underwent a decontamination protocol using 10% Betadine (1% povidone- iodine) solution. Positive pretreatment limbal cultures were obtained on 52.1% of donor eyes. Posttreatment limbal cultures demonstrated a 76.1% reduction in microbial growth, including an 85.7% reduction in Candida species. Streptococcus species were reduced by 76.7% and coagulase-negative Staphylococcus were reduced by 76.1%. In addition, of 250 donor rims obtained at the time of surgery, two had coagulase-negative. Staphylococcus present that were also present after the decontamination procedure. In no cases did endophthalmitis occur during this study. This study demonstrates that this protocol using 10% Betadine solution is extremely effective in decontaminating donor globes of aerobic bacteria and fungi. However, gentamicin-resistant organisms survived this protocol, emphasizing the need to develop storage media containing a broader-spectrum antibiotic agent than gentamicin.

ISSN:0277-3740    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Shadow photography of shock waves excited by means of a xenon chloride excimer laser was performed to determine the shock wave propagation velocity in air, nitrogen and helium. Energy densities between 500 and 2,000 mJ/ cm2were used to ablate a rotating rubber cylindrical target and porcine corneas. In ablating the rubber cylinder, a shock wave velocity of 3.3 km/s was generated in air and nitrogen at 40 ns; this decreased to 1.4 km/s at 320 ns. When helium was blown on the target, the velocity increased by a factor of approximately two, to 5.9 km/s at 40 ns and 2.7 km/s at 320 ns. We suggest that blowing helium on the surface of the cornea during excimer laser ablation may speed the dissipation of high-energy acoustic waves and gaseous particles, and thus reduce the exposure and transfer of heat energy to the surrounding tissue.

ISSN:0277-3740    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

We developed a simple device to measure the water evaporation from the ocular surface, and we measured the evaporative rate in 18 normal individuals. We compared this to a group of 15 patients with dry eye from low tear production. We found the normal rate of water evaporation from the ocular surface to be 14.7 ± 6.4 x 10-7g/cm2/s or 0.14 ± 0.06 µ/min at 30% relative humidity. For dry eye patients, the rate was significantly increased to 47.6 ± 20.1 X 10-7g/cm2/s or 0.43 ± 0.19 µl/min (p<0.005). Neither group showed any evidence of meibomian gland dysfunction that might have increased evaporation. From these results, we conclude that evaporation is accelerated when tear production decreases and is of sufficient magnitude to exacerbate the dry eye.

ISSN:0277-3740    

出版商:OVID    

年代:1993

数据来源: OVID