The effects of intraocular irrigating solutions on the human corneal endothelium (author's transl)]

Human corneas from enucleated eyes get thicker during perfusion with B.S.S. On the contrary, their thickness decreases when perfused with T.C. Earle solution. Addition of reduced glutathion and adenosine does not change the results obtained with T.C. Earle. Histological study of the endothelium after a 24 hours perfusion demonstrates a better conservation of the cells with T.C. Earle and T.C. Earle glutathion--adenosine than with B.S.S.     

Comparison of the effects of intraocular irrigating solutions on the corneal endothelium in intraocular lens implantation.

We conducted a randomised prospective controlled study to determine the effects of a glucose glutathione bicarbonate solution (BSS Plus) and a citrate acetate bicarbonate solution (S-MA2) on the corneal endothelium in patients undergoing extracapsular cataract extraction with posterior chamber lens implantation. One eye of each patient was randomly assigned to receive BSS Plus, and the other eye to receive S-MA2. BSS Plus caused significantly less corneal swelling on the first postoperative day than did S-MA2. There was no difference between the two solutions in their effect on corneal thickness one week and one month postoperatively. Computer assisted morphometric analysis of wide-field specular microscopic photographs demonstrated minimal changes in endothelial morphological characteristics in the eyes irrigated with BSS Plus. By comparison S-MA2, caused a significant loss of endothelial cells and a marked reduction in the figure coefficient. These results indicated that BSS Plus has a clinical advantage over S-MA2 with respect to the corneal endothelium.     

Comparative toxicity of intraocular irrigating solutions on the corneal endothelium.

Isolated rabbit and human corneas were perfused in vitro with Plasma-lyte 148 solution and with a glutathione bicarbonate Ringer's solution. The corneal swelling rate and ultrastructure were compared to corneas perfused with three commonly used intraocular irrigating solutions. Corneas perfused with Plasma-lyte 148 swelled at a rate of 47 mu/gr and the endothelial cells separated from each other and showed extensive damage after three hours of perfusion. By comparison, corneas perfused with 0.9% NaCl increased in thickness by 98 mu/hr, lactated Ringer's by 39 mu/hr, balanced salt solution by 24 mu/hr, and glutathione bicarbonate Ringer's solution by 4 mu/hr. These results indicate that endothelial cell damage and increased corneal thickness observed during perfusion was related to the incomplete composition of 0.9% NaCl, Plasma-lyte 148, and lactated Ringer's and that endothelial cell damage can be prevented if the intraocular irrigating solution contains concentrations of inorganic and organic constituents that are similar to those in aqueous humor.     

Effects of intraocular irrigating solutions on the corneal endothelium after in vivo anterior chamber irrigation

We used wide-field specular microscopy and corneal pachymetry to evaluate the effect of anterior chamber irrigation with BSS and BSS Plus on the corneal endothelium of cats. Endothelial changes were quantitated by computerized morphometric analysis of individual cells. After short-term (15 and 30 minutes) and long-term (one and two hours) irrigation, endothelial cell density remained unchanged. Corneal thickness increased significantly in the BSS group after one hour of irrigation. BSS Plus caused minimal changes in endothelial morphologic characteristics regardless of the irrigation time. By comparison, BSS caused a significant increase in the coefficient of variation of cell area (polymegethism) and a decrease in the percentage of hexagonal cells (pleomorphism). These changes were more prominent after prolonged irrigation. The morphologic changes caused by BSS irrigation are indicative of a stressed endothelial monolayer that may be more susceptible to additional surgical trauma.     

Effects of air and irrigating solutions on the corneal endothelium

It is well established that the corneal endothelium reflects the trauma it experiences by changing its morphological appearance. We have studied the effect of mild trauma to the rabbit endothelium by replacing the aqueous humor with air. After either 2 or 4 h, the air was removed and then replaced with either physiological saline or balanced salt solution (BSS). Specular microscopy was then performed for 1 week to observe endothelial changes. Various transient morphological changes observed during this period included many nonhexagonal cells, enlarged cells, and clusters of small cells. The changes produced were more dramatic for the saline replacement group than the BSS replacement group, indicating that the recovery process of the endothelium following this mild trauma depends on the material used to replace the air. The air appears to sensitize the endothelium to subsequent insult. This model can perhaps be used to evaluate the relative safety of the various solutions that are used in the anterior chamber during ocular surgery.     

The effect of a new intraocular irrigating solution containing dextran on rabbit corneal endothelium

This study investigated the effect of a balanced salt solution for intraocular irrigation containing 2% dextran 40. The effect of this solution was compared to that of a normal saline solution (0.9%) and balanced salt solution (Alcon). Following incubation of rabbit corneas for up to 72 h at 4 degrees C, the incubated corneas were studied by staining with Nitroblue Tetrazolium and by scanning electron microscopy. Insignificant changes occurred during the first 24 h of incubation. However, corneas stored in the dextran containing solution showed slightly smaller endothelial cells with tight junctions after 72 h. Endothelial cells showed progressive membrane rupture and eventual disappearance when incubated in normal saline for over 24 h at 4 degrees C.     

Effect of intraocular irrigating solutions on intracellular membrane potentials and swelling rate of isolated human and rabbit cornea.

Isolated human and rabbit corneas were incubated in glutathione bicarbonate Ringer solution (GBR), balanced salt solution (BSS), or 0.9% NaCl solution. The swelling rate of human corneas was 25.5 micron/hr in GBR and significantly increased to 32.7 in BSS and 66.1 in NaCl. The epithelial intracellular potential of human cornea was constant at about 60 mV up to 5 hr of incubation in GBR and decreased continuously to 40 mV in BSS and NaCl. Endothelial cell potentials were stable for up to 3 hr of incubation in GBR or BSS and decreased from a control value of about 18 mV to 10 mV 2 hr after bathing in NaCl. Qualitatively similar data were obtained in the isolated rabbit cornea. The results demonstrate the advantage of GBR as an intraocular irrigating solution.     

The effects of different intraocular irrigating solutions on the apoptosis of cultured RPE cells

Purpose To investigate the effect on porcine retinal pigment epithelial (RPE) cells of modified intraocular irrigating solutions compared with BSS and BSS plus.Methods Confluent cultures of RPE cells were incubated in experimental intraocular irrigating solutions. The cells were then examined for breakdown of DNA by the TUNEL procedure. Fragmentation of the DNA from cells was also confirmed by flow cytometry.Results Most of the experimentally, treated cells exhibited a shrunken appearance for up to 72 h. There was a steady increase in the number of cells labeled by the TUNEL method in three solutions with time. The data demonstrated that the influence of solutions on the percentage of RPE cell nuclei that gave a clear positive TUNEL stain was, in ascending order: modified solution > BSS > BSS plus. Of the three solutions tested, BSS plus showed least apoptosis.Conclusions It is suggested that BSS plus is less harmful to RPE cells than the other solutions tested. Introduction of other adjunctive solutions of antibiotics, mydriatics, miotics, and steroid, resulting in an altered electrolyte balance, pH, or osmolality in the solution, may compromise the safety and efficacy of a properly formulated and packaged solution.     

Intraocular irrigating solutions and barrier function of retinal pigment epithelium

AIM—To study the effect of intraocular irrigating solutions on the barrier property of the retinal pigment epithelium (RPE).
METHODS—The isolated rabbit RPE-choroid mounted on Ussing-type chambers under short circuit conditions was used. According to a previous study, the inward (from the choroid to the vitreous side) permeability of the tissue to carboxyfluorescein was adopted as a quantitative index of the barrier function of the RPE cells.
RESULTS—Of the three solutions tested, Krebs-Ringer solution, a commercially available glucose glutathione bicarbonate solution (BSS plus), and glucose citrate-acetate bicarbonate solution (Opeguard), BSS plus gave a significantly lower permeability (1.1 × 10^-6 cm/s on average) than Krebs-Ringer solution or Opeguard (1.9 or 1.8 × 10^-6 cm/s on average, respectively) (unpaired t test with Bonferroni's correction, p<0.05). Since the major chemical difference between BSS plus and the other two solutions is the incorporation of oxidised glutathione (GSSG), the effects of GSSG were studied using solutions having an identical composition to BSS plus, but with various concentrations of GSSG. The solution containing 0.3 mM GSSG gave significantly lower permeability than that without GSSG (1.1 × 10^-6 cm/s v 2.0 × 10^-6 cm/s) (unpaired t test with Bonferroni's correction, p<0.05).
CONCLUSION—It was suggested that BSS plus is less harmful to the barrier function of the RPE cells and that GSSG has a beneficial effect on its maintenance.

     

Effect of glucose added to intraocular irrigating solutions on the rabbit electroretinogram in vitro

The most adequate concentration of glucose in intraocular irrigating solution for the retina was studied electrophysiologically in the pigmented rabbit in vitro. Comparison of b-wave amplitudes demonstrated that glucose at a concentration of 20 m M/l yielded the highest values. A 40 mM/l glucose solution also increased the b-waves but to a lesser extent than did a solution of 20 mM/l. This result might be due to the detrimental effects of osmolarity. However, under hypoxic conditions the amplitudes of the b-wave obtained with 40 mM/l glucose solution was greater than those with 20 mM/l. It thus appears that slight hyperglycemic concentrations might have favorable effects on the ischemic retina.     

Effects of intraocular irrigating solutions on the spreading of rabbit corneal endothelial cells on extracellular matrices

The effects of four commercially available irrigating solutions on the spreading of rabbit corneal endothelial cells on various extracellular matrices were studied. Cultured rabbit corneal endothelial cells, suspended in one of the following intraocular irrigating solutions, Opeguard MA, BSS, BSS Plus, lactated Ringer solution (Lactec) or physiological saline, were placed on uncoated tissue culture plates or on plates coated with extracellular matrices (fibronectin, laminin, collagen type I, or collagen type IV). The cell area was measured after 45 minutes' incubation. The cells spread on all of the extracellular matrices examined but not on the uncoated tissue culture plates. On the fibronectin or laminin matrix, the cell area was significantly greater with Opeguard MA or BSS Plus. On laminin and collagen type IV, the cell area was the greatest with Opeguard MA. On collagen type I, the cell area was significantly greater with Opeguard MA, BSS, or BSS Plus. These results demonstrated that the rabbit corneal endothelial cells responded to the extracellular matrices, and that Opeguard MA or BSS Plus provided more favorable conditions for the spreading of these cells. These results indicated that both Opeguard MA and BSS Plus might aid the spreading of corneal endothelial cells during wound-healing immediately after intraocular surgery.     

Effect of oxidized glutathione on the barrier function of the corneal endothelium

Effects of glutathione on the corneal endothelium were reexamined. Four kinds of solutions were made: oxidized glutathione (GSSG) was added to a basic solution which does not contain glutathione (GSSG-0) at a concentration of 0.03 mM, 0.3 mM or 3 mM to make GSSG-0.03, GSSG-0.3 or GSSG-3, respectively. Paired rabbit corneas were perfused separately, and the endothelial permeability (Pac) to carboxyfluorescein was determined. Between the paired corneas perfused with GSSG-0 and GSSG-0 or GSSG-0 and GSSG-0.03, there was no significant difference in the Pac. A significant difference in this factor was seen between the paired corneas perfused with GSSG-0 and GSSG-0.3 or GSSG-0 and GSSG-3 (P less than 0.01). The ratio of GSSG-0 to GSSG-0.3 for Pac, 1.18 +/- 0.16, and that of GSSG-0 to GSSG-3, 1.14 +/- 0.07, were significantly greater than the left-right ratio for Pac obtained when the paired corneas were perfused with GSSG-0, 1.01 +/- 0.10 (mean +/- SD, n = 8) (P less than 0.025). The corneal swelling rate (micron/hr) was 7.9 +/- 4.9 for the corneas perfused with GSSG-0 and 8.4 +/- 5.4 (mean +/- SD, n = 6) for those perfused with GSSG-0.3; difference was not significant. Addition of GSSG at a concentration of 0.3 mM or more to the irrigating solution was further beneficial to the corneal endothelial barrier function and a solution containing GSSG may be safer for patients with vulnerable corneas.     

Effects of glucose and fructose added to the intraocular irrigating solutions on the rabbit ERG in vitro

The addition of various concentrations of glucose to intraocular irrigating solutions for the retina was studied electrophysiologically using an in vitro eye-cup in the pigmented rabbit. Comparison of b-wave amplitudes demonstrated that, glucose at a concentration of 20 mM/l yielded the highest values. With this concentration, the b-wave amplitude was markedly enhanced to 250% at 90 minutes. With 5 mM/l glucose (normogycemic) solutions, the b-waves were decreased to below 20% at 60 minutes. A 40 mM/l glucose solution also increased the b-waves but to a lesser extent than 20 mM/l. These results might be due to the detrimental effects of osmolarity. However, under hypoxic conditions the amplitudes of b-waves obtained with 40 mM/l glucose solutions were greater than those with 20 mM/l glucose solutions. The addition of 10 mM/l fructose to the control solution had no remarkable effects suggesting that fructose is not a direct energy source for the in vitro retina.     

Sided effects of bicarbonate on rabbit corneal endothelium in vitro

Stroma-endothelium preparations from albino rabbits were studied either in a specular microscope (and measurements made of corneal thinning under silicone oil) or mounted between two half-chambers (to permit direct measurement of endothelial fluid pump activity). Preparations were first equilibrated with bicarbonate-Ringer solutions (supplemented with glucose, adenosine and glutathione and equilibrated with 5% CO₂-air). If the preparations were equilibrated with a low (2 mM) level of bicarbonate on the stromal side and variable levels (2 to 50 mM) of bicarbonate on the endothelial side, corneal thinning increased with bicarbonate concentration while fluid pump was found to be constant from 2 to 35 mM bicarbonate. In contrast, if the preparations were equilibrated with a low (2 mM) bicarbonate level on the endothelial side and 2 to 50 mM bicarbonate on the stromal aspect, corneal thinning did not occur but fluid pump declined gradually as a function of stromal bicarbonate levels. These results contrast sharply with the significant corneal thinning and fluid pump that can be measured if both sides of the preparations are equilibrated with 35 mM bicarbonate. These results further emphasise that bicarbonate ions do not simply serve to drive an endothelium-sited fluid pump in the mammalian cornea.     

In vitro compatibility study of cephalosporin with intraocular irrigating solutions and intracameral medications

Background: To study the compatibility of cephalosporins with intraocular irrigating solutions and intracameral medications commonly used in cataract surgery. Design: The was an in vitro experiment conducted in the Research Laboratory of the Department of Microbiology, the Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong. Samples: Three cephalosporins – cefazolin, cefuroxime and ceftazidime – were separately diluted and mixed with irrigating solutions and intracameral medications to form 192 samples and 12 control solutions. Methods: The cephalosporins were dissolved in normal saline and further diluted to the concentration of 1 mg in 0.1 mL with normal saline, Ringer's solution, balanced salt solution and fortified balanced salt solutions. These were mixed with balanced salt solutions or fortified balanced salt solutions, with adrenaline, acetylcholine or carbachol and kept at 37°C for 2 h. The concentrations of free cephalosporins were measured with rapid high‐performance liquid chromatography at baseline (0 h) and at 2 h. Main Outcome Measures: Free concentrations of cephalosporins at 2 h were compared with mean baseline (0 h) value. A difference of 3 standard deviations or more was considered statistically significant. Results: At 2 h there was a significant drop in the cefuroxime concentration in preparations in which cefuroxime was diluted with normal saline (P < 0.01). In all preparations, the final concentrations of cephalosporins were higher than the minimal inhibitory concentrations (MIC₉₀) for microbials commonly isolated from the external eye. Conclusion: Cefazolin, cefuroxime and ceftazidime were compatible with irrigating solutions and intracameral medications commonly used in cataract surgery.     

Comparison of the effect of polymethylmethacrylate and silicone intraocular lenses on rabbit corneal endothelium in vitro

An in vitro comparison of corneal endothelial damage caused by polymethylmethacrylate and by silicone intraocular lenses was made. Endothelial damage was assessed by vital staining of corneal endothelium immediately following direct contact with an intraocular lens. Silicone lenses produced less damage than polymethylmethacrylate lenses. The difference could be attributed to a specific type of damage-membrane stripping-seen only after contact with polymethylmethacrylate lenses.