Coefficient of friction of ocular surface lubricants for laser in situ keratomileusis.

PURPOSE: The coefficient of friction was empirically derived for a series of commercially available ophthalmic lubricants having potential use during laser in situ keratomileusis (LASIK). METHODS: Measurements were obtained using a modified tensile testing machine. Solutions tested included the artificial tear supplements Polytears-free, Bion Tears, Genteal, Refresh, Cellufresh, Celluvisc, Theratears, and Viscotears gel; and balanced salt solution (BSS). RESULTS: Viscotears carbomer gel had a significantly lower mean coefficient of friction compared to other ophthalmic lubricants tested (P=.002) and the dry plate (P=.005). Addition of 0.1 ml of BSS to 0.025 ml of Celluvisc significantly reduced the coefficent of friction of Celluvisc (P=.01). Polytears, Bion Tears, Genteal, Refresh, Celluvisc, Theratears, and BSS had coefficients of friction significantly higher than that of the dry plate. CONCLUSION: A range of values were obtained for the coefficient of the ophthalmic lubricants tested. Viscotears gel (0.1 ml), and Celluvisc (0.025 ml) + BSS (0.1 ml) had coefficients of friction significantly lower than that of the dry plate.

Effect of carmellose-based artificial tears on the ocular surface in eyes after laser in situ keratomileusis.

BACKGROUND: Strategies to minimize intraoperative ocular surface disturbance and accelerate postoperative ocular surface recovery are an important consideration to the surgeon. METHODS: Eighteen eyes of 10 patients were randomized to receive intraoperative and postoperative non-preserved balanced salt solution or non-preserved carboxymethylcellulose-based (carmellose) artificial tears. Presence and severity of McMonnies dry eye symptom survey score primary dry eye symptoms, fluorescein break-up time, and rose bengal staining were graded preoperatively and at 1 day, 1 week and 1 month postoperatively. Conjunctival impression cytology of the perilimbal conjunctiva was performed 1 month after surgery to determine goblet cell density. RESULTS: McMonnies dry eye symptoms were reported more frequently for the balanced salt solution group at 1 day, 1 week, and 1 month after surgery. Fluorescein break-up time was significantly greater in the carmellose-based group at 1 day (P < .01), 1 week (P = .04), and 1 month (P < .01) after surgery. The rose bengal staining score was significantly greater at 1 day (P < .01) and 1 week (P < .01) postoperatively for the balanced salt solution group. Mean goblet cell density for the carmellose-based group at 1 month postoperatively was significantly greater than that for the balanced salt solution group (P < .01). CONCLUSIONS: Postoperative and intraoperative use of carmellose-based artificial tears resulted in significantly more rapid recovery of the ocular surface after LASIK when compared to balanced salt solution.

Telemedicine ophthalmology consultation in remote Queensland.

OBJECTIVE: To assess the use of remote telemedicine ophthalmology in patients presenting to an emergency department with acute eye problems. DESIGN: A prospective review from 1 December 1996 to 28 February 1997 of referral patterns and telemedicine consultations, comparing referral patterns with the same period one year before. PARTICIPANTS AND SETTING: 24 patients presenting to the emergency department of a remote base hospital in Queensland with an acute ophthalmological problem requiring a specialist opinion. MAIN OUTCOME MEASURES: Clinical outcomes; use of the Patient Transit Scheme for isolated patients; acceptability to patients and doctors; and ophthalmologists' opinions of the system. RESULTS: No adverse outcomes were identified. Patients transferred for urgent assessment fell from 17 for the corresponding period in the previous year to four during the study period, while respective numbers of patients requiring non-urgent transfers (for surgery or postoperative review) during the same periods were 41 and 30. Both patients and staff (including the ophthalmologists) found the telemedicine facility very acceptable. CONCLUSION: Ophthalmology is well suited to telemedicine for the diagnosis and management of acute conditions and postoperative assessment of patients in remote areas. It offers considerable potential benefits to patients, and enhances the skills of local practitioners.

Fasciola hepatica infection in sheep: changes in liver metabolism.

Several aspects of liver function during infection with Fasciola hepatica were examined in sheep four weeks after infection and compared with the changes observed in infected rats. Previously reported respiratory abnormalities in mitochondria isolated from the left lobe of the liver of infected sheep were characterised further. Evidence is presented that the respiratory lesion is located in the mitochondrial electron transport chain and that the aberrant respiratory behaviour is not associated with an increase in nonesterified fatty acids and the depletion of mitochondrial phospholipids, as is the case in the rat. Microsomal membranes, which have also been shown to be depleted of phospholipids in the fluke-infected rat liver, showed no such changes in the sheep. However, in common with the rat, a substantial loss of cytochrome P450 was recorded in microsomes prepared from the left lobe, and the glycogen content of the left lobe was found to be less than 50 per cent of control values. No change was observed in glucose 6-phosphatase activity. All these changes were localised effects, confined to areas of fluke infiltration.

Importance of T-cell-dependent inflammatory reactions in the decline of microsomal cytochrome P450 concentration in the livers of rats infected with Fasciola hepatica.

The concentration of cytochrome P450, measured spectrophotometrically in microsomal preparations from the livers of rats infected with 30 metacercariae of Fasciola hepatica, declined by approximately 50% at 3 weeks post-infection. Treatment of infected rats with the anti-inflammatory agent dexamethasone (2 mg/kg at 48 h intervals for 8 days prior to assay) abolished the decline in P450 content. Assay of P450 in infected congenitally athymic (nude) rats showed normal levels. These results demonstrate that the T-cell-dependent inflammatory response in the liver of the host is a necessary factor in the development of the decline in hepatic P450, which is known to compromise the metabolism of certain drugs in infected hosts.

Aberrant mitochondrial respiration in the livers of rats infected with Fasciola hepatica: the role of elevated non-esterified fatty acids and altered phospholipid composition.

The non-esterified fatty acid (NEFA) content and phospholipid composition of mitochondria isolated from the livers of Wistar rats infected with Fasciola hepatica were examined in relation to the aberrant mitochondrial respiration previously reported [Rule, Behm, and Bygrave (1989) Biochem. J. 260, 517-523]. At 2 weeks post-infection, elevated NEFA levels were associated with uncoupling of mitochondrial respiration that was reversible in vitro by the addition of BSA. State IV respiration rates showed a strong correlation with NEFA content. At 3 weeks post-infection, NEFA content had increased further and uncoupled mitochondria no longer showed any response to BSA. 31P-NMR analyses of cholate extracts of mitochondria from infected livers at 3 weeks post-infection revealed a marked loss of several major phospholipid species with a concomitant increase in catabolic products, particularly glycerophosphocholine and glycerophosphoethanolamine. Similar changes were observed in microsomal extracts. The NEFA content and phospholipid composition of mitochondria isolated from infected, athymic nude rats were not significantly different from uninfected, athymic rats. These findings suggest that uncoupling of liver mitochondria during infection with F. hepatica is the result of phospholipase activation mediated by the immune system of the host.

Characterization of the oligomycin-sensitivity properties of the F1F0-ATPase in mitochondria from rats infected with the liver fluke Fasciola hepatica.

The F1F0-ATPase activity of liver mitochondria isolated from rats infected with Fasciola hepatica at 3 and 4 weeks post-infection showed a marked loss of sensitivity to oligomycin and to N,N'-dicyclohexylcarbodiimide. A loss of sensitivity to diethylstilbestrol was also demonstrated at 4 weeks post-infection. Recovery was apparent in most cases by 6 weeks post-infection. No significant difference in latent ATPase activity was observed between mitochondria from control and infected livers at any stage of the infection. The mitochondria from infected livers were therefore considered to have a full complement of the F1 moiety of the F1F0-ATPase complex. Purification of the mitochondrial ATPase from 4-week infected livers resulted in a very low yield of an oligomycin-insensitive complex. This was due to a failure to enrich specific activity during purification. The evidence presented indicates that infection with Fasciola hepatica gives rise to alterations in the function of the host liver mitochondrial ATPase, namely loss of inhibitor sensitivity and apparent structural alterations of the ATPase complex.

Restoration of mitochondrial energy-linked reactions following dexamethasone treatment of rats infected with the liver fluke Fasciola hepatica.

Mitochondria isolated from male Wistar rats experimentally infected with the common liver fluke, Fasciola hepatica, exhibit loss of respiratory control from 2 weeks post-infection (Rule, et al. (1989) Biochem. J. 260, 517-523). We now report that subcutaneous injections of the anti-inflammatory drug, dexamethasone, during the final week of infection prevented the mitochondrial uncoupling and restored respiratory control almost to the levels of uninfected controls. Further investigations have shown that mitochondria from infected rat livers are unable to synthesize ATP and that abnormal respiration is also evident in hepatocytes isolated from infected rats. These abnormalities were absent when infected rats were treated with dexamethasone. In addition, liver mitochondrial function in infected, congenitally athymic, nude rats (CBH/R nu/nu) was not significantly different from that in uninfected nude or Wistar controls. These results provide evidence that the mitochondrial dysfunction in fascioliasis is host-mediated and that T lymphocytes in particular may be involved.