The effects of intravitreal irrigation during vitrectomy on the electroretinogram

The Effect of Vitrectomy Infusion Solutions on Postoperative Electroretinography and Retina Histology

Purpose

A prospective, randomised, masked study comparing three different intraocular infusion solutions used during vitrectomy on postoperative electroretinography (ERG) and retinal histology of rabbit eyes.

Methods materials and animals

Twelve rabbit eyes were used with each group of three intraocular infusion solutions: Lactated Ringers (LR), balanced salt solution (BSS) and balanced salt solution-plus (BSS-Plus).

Results

At 24 hours postoperatively, the ERG values were 36%, 68% and 75% of the normal values for LR, BSS and BSS-Plus, respectively. At 72 hours postoperatively, the ERG values were 50%, 84% and 100% of the normal values for LR, BSS and BSS-Plus, respectively. At 72 hours postoperatively, 3/12, 10/12 and 12/12 of the vitrectomised eyes had regained normal-value ERGs for LR, BSS, and BSS-Plus eyes, respectively. At 1 week postoperatively, 4/12 and 12/12 of LR and BSS eyes, respectively, had normal ERGs. The number of LR eyes regaining normal ERG values was 4/12, 6/12 and 9/12, measured at 1, 4 and 15 weeks postoperatively, respectively.

Retina histology

At 15 weeks follow-up, histopathology was performed on several rabbit eyes. Histological examination of LR-irrigated eyes showed 2/7 normal retinas, whereas 5/7 showed changes that ranged from vacuoles in the inner retina to numerous vacuoles in both the outer and inner retina with disruption of the inner nuclear layer. The histology of BSS-infused and BSS-Plus-infused rabbit eyes was normal.

Conclusion

LR solution, when used during vitrectomy, has a more prolonged negative effect on ERG than BSS and BSS-Plus. Histological changes seen in LR eyes may explain the ERG results.

Melanin Precursor 5,6-Dihydroxyindol: Protective Effects and Cytotoxicity on Retinal Cells in vitro and in vivo

5,6-Dihydroxyindole (DHI) is a melanin pigment precursor with antioxidant properties. In the light of a report about cytotoxicity of DHI, the aim of this study was to assess possible toxic effects of DHI on cells related to the eye, such as human ARPE-19 cells and mouse retinal explants. Moreover, DHI was tested on its effects on retinal function in vivo using electroretinography. We found cytotoxicity of DHI against ARPE-19 cells at 100 μM, but not at 10 μM. 10 μM DHI exhibited a slight, though not significant protective activity against UV-A damage in ARPE-19 cells. We found cytoprotection in cultured mouse retinas by 50 μM DHI or its diacetylated derivative 5,6-diacetoxyindole (DAI), respectively. In ERG measurements in vivo, amplitudes were decreased only slightly by 100 μM DHI compared to saline, whereas a better preservation of amplitudes was visible at 10 μM DHI, in particular with respect to cones. In histological sections, more cones were found at 10 μM DHI than at 100 μM DHI. As a conclusion, DHI shows a slight protective effect at 10 μM both in vitro and in vivo. At 100 μM, it shows a strong cytotoxicity in vitro, which is strongly reduced in vivo.

Bevacizumab (avastin) does not harm retinal function after intravitreal injection as shown by electroretinography in adult mice

PURPOSE

Scavenging of VEGF by specific antibodies is a promising way to treat ocular conditions connected with neovascularization. Intravitreal injections of Avastin (bevacizumab) are performed frequently as a treatment of such conditions. In this study, the authors examine whether the retinal function in wild-type mice is affected by an intravitreal injection of Avastin.

METHODS

Electroretinography was performed in four different experimental groups of wild-type C57BL/6 mice before treatment and 1, 4, 12, and 25 days afterwards. The first group was injected intravitreally with BSS, the second one received injections of a vehicle solution, and the third group was injected with the commercial Avastin solution. In a fourth group, sham surgery was performed. Immunohistochemistry was performed in some eyes to evaluate penetration of the bevacizumab molecule through the retina.

RESULTS

In all four groups, a similar behavior of the ERG parameters could be detected. One day after the injections, the amplitudes showed a clear decrease. Later on, they recovered gradually. No difference could be seen between eyes injected with Avastin or vehicle solution. Bevacizumab immunoreactivity was already present in the whole retina half an hour after the intravitreal injection and was not detectable 25 days later. Moreover, binding of bevacizumab to endogenous mouse VEGF could be shown.

CONCLUSIONS

Based on the electroretinographic findings, the authors conclude that bevacizumab does not have any toxic effects on the mouse retina and its function. The bevacizumab molecule penetrates the retina quickly. Therefore, it can act safely and very quickly, also in deeper retinal layers after its injection.

EFFECT OF OXYGENATED INTRAOCULAR IRRIGATION SOLUTIONS ON THE ELECTRORETINOGRAM AFTER VITRECTOMY

PURPOSE

To investigate the effect of oxygenated intraocular irrigating solutions on electroretinograms (ERGs) for postvitrectomy rabbits.

METHODS

Eight groups of five rabbits each underwent pars plana vitrectomy on the right eye; the left eye of each rabbit served as control. The intraocular irrigating solutions were balanced salt solution (BSS), BSS-plus, BSS + oxygen (BSS + O2), BSS-plus + O2, and combinations of each with the addition of endoillumination (L). All animals were evaluated by single-flash scotopic electroretinography on the operated and nonoperated eyes before surgery and at 1 hour, 1 day, 1 week, and 1 month after surgery by an unmasked observer. The main outcome measures were dark-adapted b-wave amplitudes of operated eye/nonoperated eye ratios. The results for the different groups were compared by analysis of variance.

RESULTS

Mean dark-adapted b-wave amplitudes of operated eye/nonoperated eye ratios +/- SD for BSS-plus and BSS-plus + O2 before surgery and 1 hour, 1 day, 1 week, and 1 month after surgery were 1.01 +/- 0.09, 0.50 +/- 0.11, 0.95 +/- 0.11, 0.97 +/- 0.11, and 0.99 +/- 0.08 and 0.98 +/- 0.08, 0.59 +/- 0.10, 0.92 +/- 0.06, 0.97 +/- 0.08, and 0.97 +/- 0.10, respectively. At both 1 hour and 1 day after surgery, rabbits treated with BSS-plus + O2 had an earlier b-wave return to baseline findings, but the differences were not statistically significant (P > 0.05). Mean dark-adapted b-wave amplitudes of operated eye/nonoperated eye ratios +/- SD for BSS and BSS + O2 before surgery and 1 hour, 1 day, 1 week, and 1 month after surgery were 1.02 +/- 0.10, 0.47 +/- 0.09, 0.77 +/- 0.07, 0.89 +/- 0.07, and 0.89 +/- 0.07 and 1.02 +/- 0.06, 0.62 +/- 0.16, 0.94 +/- 0.09, 0.97 +/- 0.08, and 0.96 +/- 0.06, respectively. One hour and 1 day after surgery, ERG readings for rabbits treated with BSS + O2 exhibited a statistically significantly earlier return of ERG voltage to baseline values compared with both BSS and BSS + L (P = 0.05 and P = 0.02, respectively). One day after surgery, rabbits treated with BSS alone had the lowest ERG ratios. One week and 1 month after surgery, for all solutions tested other than BSS, ERG values were within normal limits.

CONCLUSION

The use of oxygenated solutions appears to affect ERG readings after pars plana vitrectomy. Further studies to evaluate the role of oxygenated solutions in different vitreoretinal surgical procedures are warranted.

Anti-inflammatory effects of topical ocular MAXIDEX® administration to rabbits following vitrectomy or lensectomy

We conducted a series of surgical studies (n=155) to find out the possible utility of the Dutch Belted rabbits as an ocular test model. Following either vitrectomy (n=59) or lensectomy (n=96) studies using either BSS or BSS Plus, we characterized the corresponding magnitude and duration of inflammatory response of selected endpoints over a one-week period. Preoperative Dutch Belted rabbits served as controls for baseline determination (n=27). Inflammatory endpoints included clinical inflammation, blood aqueous barrier (BAB) changes measured by particle-scatter and fluorophotometry, corneal edema, and prostaglandin-E2 (PGE2). Topical ocular 0.1% dexamethasone (MAXIDEX) served as a positive treatment group. We compared the inflammatory features (treated and untreated) to determine significance. Using either irrigating solution, the endpoints (n=101) were shown increased in both models. While the clinical scores were similar following both types of surgery (ns; p=0.51), the lensectomy study caused a more marked effect on corneal edema (p=0.0004) and PGE2 production (p=0.002) compared with the vitrectomy study. After the lensectomy procedure, BSS Plus (n=52) compared with BSS (n=24) showed a significant improvement (p=0.004) of clinical score during the recovery phase. Further improvement was gained over BSS Plus (n=52) using MAXIDEX treatment. Topical MAXIDEX (lensectomy, n=20/group; vitrectomy, n=12/group) reduced clinical score (p<0.001), decreased BAB breakdown to fluorescein (p<0.01), lessened particle flare (p<0.05), inhibited aqueous PGE2 levels (p<0.001), and reduced corneal edema (p=0.01) in the lensectomy group. The use of the rabbit model offers a convenient test to identify therapeutic agents that could lessen ocular complications after these common ocular surgeries.

The Disposition and Bioavailability of35S-GSH from35S-GSSG in BSS PLUS®in Rabbit Ocular Tissues

The purpose of this study was to evaluate the biodistribution and uptake of 35S-GSH into intraocular tissues following the administration of BSS PLUS containing 35S-GSSG by either an anterior chamber or intravitreal injection. This study evaluated the disposition and uptake of the 35S-radiolabel, the intracellular concentrations of 35S-GSH from extracellular 35S-GSSG, and the percentage of 35S-GSH to the total cellular GSH pool. Glutathione was analyzed by high-performance liquid chromatography (HPLC) using fluorescence detection after derivitizing the thiols in situ with monobromobimane. The effluent from the GSH peak was then collected for measurement of 35S-GSH. After an anterior chamber injection of 35S-BSS PLUS, 35S-radioactivity rapidly disappeared from the aqueous humor between 0.5 and 2 hours; corneal 35S-radioactivity remained constant over time. 35S-GSH was detected in the iris and ciliary body. However, in the cornea, 35S-GSH became the predominant radioactive thiol in the stroma, endothelium, and epithelium; the corneal stroma appeared to be a possible GSH reservoir for the adjacent corneal layers. After an intravitreal injection, 35S-radioactivity slowly decreased in the vitreous humor but was readily taken up by the tissues of the posterior segment, especially the retina and choroid, which showed the greatest concentrations of 35S-GSH of all tissues studied. The data from this study demonstrate that 35S-GSSG in BSS PLUS is metabolized and taken up by ocular cells and that 35S-GSH becomes incorporated into the intracellular GSH pool of ocular tissues.

An in vitro study on the compatibility and precipitation of a combination of ciprofloxacin and vancomycin in human vitreous

AIMS

To investigate the precipitation process of a mixture of vancomycin and ciprofloxacin by equilibrium dialysis and its subsequent effect on the level of available free antibiotics.

METHODS

Concentrations of vancomycin and ciprofloxacin in an equilibrium dialysis chamber were measured during the equilibrium process by high performance liquid chromatography and fluorescence polarisation immunoassay. Normal saline (NS), balanced salt solution plus (BSS Plus), and vitreous were used separately as the medium of dialysis.

RESULTS

Precipitation of ciprofloxacin occurred on incubation at 37 degrees C. It formed precipitate on its own or when mixed with vancomycin in all the three media of NS, BSS Plus, and vitreous. There was more precipitation at higher initial ciprofloxacin concentrations; at 25.0 mg/l about 75% free drug in BSS Plus was lost after 72 hours. The extent of precipitation was similar in both NS and BSS Plus. In the dialysis chambers, 20 mg/l ciprofloxacin dialysed against 125 mg/l vancomycin was reduced to a concentration about 5.0 mg/l after 168 hours. Precipitation of vancomycin was negligible. Ciprofloxacin precipitated in vitreous at body temperature, irrespective of the presence of vancomycin. Even after precipitation, the resultant concentration of ciprofloxacin was still higher than the MIC(90) of the drug against most Gram negative organisms.

CONCLUSIONS

Based on this in vitro study, ciprofloxacin precipitated in vitreous at body temperature, irrespective of the presence of vancomycin or the medium for intravitreal injection. The resultant amount of ciprofloxacin was still higher than the MIC(90) of the drug against most Gram negative organisms after precipitation. The authors suggest ciprofloxacin in place of ceftazidime when used in combination with vancomycin for treatment of infective endophthalmitis.

Morphological changes in the optic disc after vitrectomy and fluid-air exchange

BACKGROUND

Although many investigators have previously reported various ocular complications induced by vitrectomy, little is known about post-operative morphological changes in the optic disc. The purpose of this study is to evaluate the effect of vitrectomy and fluid-air (F-A) exchange on the post-operative morphology of the optic disc.

METHODS

We examined 31 eyes that had undergone vitrectomy for macular holes (22 eyes) or epiretinal membranes (9 eyes). Only the patients with macular holes were treated by fluid-air exchange. Morphological changes in the optic disc were evaluated using the Heidelberg Retina Tomograph.

RESULTS

C/D area ratios significantly decreased for 6 months post-operatively. The rim volumes significantly increased for 1 month following surgery. Cup volumes significantly decreased at 3 months after surgery. No significant change of mean cup depth was observed post-operatively. The eyes that had not been subjected to F-A exchange showed no significant morphological change following surgery. In contrast, the eyes that had undergone F-A exchange showed significant decrease in C/D area ratio and cup volume and an increase in rim volume and mean cup depth for considerable periods following surgery. Any of the patients showed no post-operative visual field loss.

CONCLUSION

Whereas no visual field loss is observed, vitrectomy with F-A exchange induces morphological changes in the optic disc for significant periods following surgery.

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.

The effect of partial vitrectomy on blood-ocular barrier function in the rabbit

PURPOSE

To compare ocular vascular permeability in the rabbit after vitrectomy as assessed by contrast-enhanced magnetic imaging (CE-MRI) and measurements of aqueous and vitreous humor protein concentration.

METHODS

Partial vitrectomies were performed, irrigating with BSS or BSS PLUS. Post-operative vascular leakage was determined by CE-MRI following intravenous administration of gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA). Aqueous and vitreous protein concentrations were quantified by standard biochemical assay. ERG evaluations were performed on postoperative days 1, 3, and 7.

RESULTS

Using BSS as irrigant, breakdown of the inner blood-retinal barrier (BRB) occurred in 4/7 eyes on post-operative day 1. The rate of Gd-DTPA leakage was significantly greater on postoperative day 1 than that in unoperated, control eyes, but declined approximately 50% by day 3. At both time points, outer BRB breakdown was restricted to the sclerotomy wounds. No BRB leakage was detectable in control eyes. Blood-aqueous barrier (BAB) leakage was bilateral on day 1. Significantly greater Gd-DTPA leakage occurred in the operated eye than in the nonsurgical contralateral eye. On day 3, approximately 40% bilateral reduction in leakage indicated resolution of BAB leakage. Notably, Gd-DTPA leakage of the BAB and BRB was significantly reduced in the BSS PLUS treated group. In contrast to MRI assessments, protein concentrations of the aqueous and vitreous in the surgical eye showed no detectable differences between BSS and BSS PLUS. Concurrent with the transient loss of ocular barrier function, ERG responses also declined. However, by day 7 greater than 90% recovery was noted in BSS PLUS treated animals but not in the BSS treatment group.

CONCLUSIONS

CE-MRI is capable of detecting subtle changes in vascular permeability following ocular surgery. Advantages of using BSS PLUS compared to BSS as the irrigating solution can be detected using this technique. BSS PLUS's protection of barrier function is consistent with a rapid recovery in retinal function not observed in BSS treated eyes.

Comparative study of vitrectomy for dropped nucleus with and without the use of perfluorocarbon liquid. Clinical, electrophysiological and visual field outcomes

PURPOSE

To compare pars plana vitrectomy for dropped nucleus with and without perfluorocarbon liquid.

METHODS

24 eyes with dropped nucleus were randomized to undergo PPV with perfluorodecalin, (study, n=12) and without it (control, n=12). Visual acuity, IOP, visual evoked response and electroretinography were noted at study entry and up to 3 months after PPV. Humphrey perimetry was done at 3 months.

RESULTS

Final visual acuity was >20/60 in 75% of study eyes and 41.6% of controls. The two groups were statistically comparable with regard to the above parameters before PPV and during follow-up. The timing of vitrectomy did not significantly influence the final visual acuity. A higher rate of complications was seen in the control group.

CONCLUSIONS

Perfluorodecalin facilitated the procedure and possibly minimized complications, and was found to be safe for intraoperative use in terms of recovery of visual acuity, stable ERG and VER, and normal visual fields.

Electroretinographic changes in eyes with idiopathic macular hole treated by vitrectomy

We recorded full-field electroretinograms before and after vitrectomy in 18 eyes of 18 patients with idiopathic macular hole. The results were compared between affected and fellow eyes in the preoperative and early (within 10 days) and late (3 to 6 months) postoperative periods. No significant changes between affected and control eyes were found in the amplitude of the rod electroretinogram, mixed cone-rod electroretinogram, cone electroretinogram a- and b-waves or 30-Hz flicker electroretinogram in all stages of the study. The peak implicit times of the cone electroretinogram (a- and b-wave) and dark- and light- adapted oscillatory potential (O1-O4), however, were delayed. Also, the amplitude of the oscillatory potentials (O1+O2+O3+O4) was significantly reduced in the early postoperative period. By the late period, all of these changes had resolved. We concluded that electrophysiologic changes were derived from a transitory dysfunction of the inner retina. The possible causes of the electroretinographic changes would include mechanical trauma of the surgery, intravitreous air tamponade or the changes in vitreous electrolytes after surgery. Oscillatory potentials were more sensitive than a- and b-waves in eliciting dysfunction of the inner retina in operate on eyes.

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 x 10(-6) cm/s on average) than Krebs-Ringer solution or Opeguard (1.9 or 1.8 x 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 x 10(-6) cm/s v 2.0 x 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.

A comparative study of intraocular irrigating solutions: effects on electroretinography readings during closed vitrectomy in humans

The effects of intraocular irrigating solutions on electroretinography have been extensively studied in animal models, but effects on human electroretinography have not been reported. This study examined the effects of two commercially available irrigating solutions, S-MA2 (Opeguard MA) and DE-057 (BBS-Plus) on 30-Hz flicker electroretinography during closed vitrectomy in humans. Eight eyes of 8 patients were examined. All patients underwent a simple vitrectomy without treatment of proliferative membrane. For 30-Hz flicker electroretinography recording, a contact lens with a built-in light-emitting diode was sterilized and used as both a stimulus source and a recording electrode. Replacing S-MA2 with DE-057 decreased the electroretinography amplitude from 55.8 +/- 15.2 to 45.5 +/- 13.2 microV (mean +/- SEM). Changing the irrigation solution from DE-057 back to S-MA2 increased the amplitude from 45.5 +/- 13.2 to 59.9 +/- 17.3 microV. However, these changes were not statistically significant. Replacing S-MA2 with DE-057 significantly increased the peak time from 50.1 +/- 1.5 to 57.6 +/- 1.3 msec (p < 0.001). This change was reversible; after changing from DE-057 back to S-MA2, the peak time of flicker electroretinography significantly decreased from 57.6 +/- 1.3 to 49.0 +/- 2.1 msec (p < 0.01). Thus intraoperative 30-Hz electroretinography showed delayed peak time during irrigation with DE-057, as compared with S-MA2. The lower potassium concentration and higher glucose concentration of S-MA2, as compared with DE-057, may be the cause of such electroretinography changes.

Effects of PhXA41, a prostaglandin analogue, and PGF2 alpha on the corneal and intraretinal d.c. electroretinogram (ERG) of the albino rabbit eye

PhXA41, a prostaglandin F2 alpha analogue, is a new drug alternative for medical treatment of glaucoma. From earlier studies, it is known that certain prostaglandins (pgs) exert an influence on the d.c. electroretinogram (ERG). In the present study, possible effects of intraocular perfusion with PhXA41 (free acid) or PGF2 alpha on the rabbit retina and retinal pigment epithelium (RPE) were evaluated. Unilateral vitrectomy was performed and a continuous intraocular perfusion was established, in which a reference solution was alternated with the test solution. In part one of the experiments, the corneal d.c. ERG and the standing potential of the eye (SP) were recorded from both eyes. In part two, vitreal and intraretinal d.c. ERG were recorded in the vitrectomized eye. PhXA41 and PGF2 alpha produced similar effects, i.e. a significant and reversible c-wave increase at concentrations of 1-10 micrograms/ml. No influence was found in the concentration interval 10-100 ng/ml. There were no changes in a- and b-wave amplitudes at any of the concentrations tested. At a concentration of 10 micrograms/ml, the SP increased significantly. The intraretinal d.c. ERG showed a large reduction of slow PIII accompanied by a small change in transepithelial potential (TEP). Theoretically, a vitreous concentration of less than 1 ng/ml may be reached after topical application. This concentration level does not influence the d.c. ERG in this animal model. At higher concentrations, a significant and reversible c-wave increase seemed to be generated mainly in the inner retina by a reduction of slow PIII generated in the Müller cells. The effect of PhXA41 appears to be mediated by an FP receptor.

Intraocular irrigating solutions. A randomized clinical trial of balanced salt solution plus and dextrose bicarbonate lactated Ringer's solution

BACKGROUND

Two intraocular irrigating solutions which differ principally by the presence of oxidized glutathione were compared in this randomized, masked, prospective study to discern differences in preservation of endothelial cell size.

METHODS

Sixty-four patients undergoing extracapsular cataract extractions were randomized between two irrigating solution groups, Balanced Salt Solution (BSS) Plus (n = 30) and dextrose bicarbonate lactated Ringer's solution (n = 34). Preoperative and postoperative endothelial specular photomicrographs were analyzed for cell size and hexagonality, and the two groups were compared using repeated measures analysis of variance.

RESULTS

Fifty-eight subjects (91%) completed the 2-month study. Change in cell size for the BSS Plus group (n = 28) (mean +/- standard error, 29.4 +/- 12.3 microns2) was not significantly different from the dextrose bicarbonate lactated Ringer's solution group (n = 30) (27.5 +/- 12.9 microns2) (P = 0.92). Groups did not differ significantly in percent hexagonality (P = 0.57) or in the variability of cell size (P = 0.61).

CONCLUSION

The presence of glutathione in BSS Plus and other minor electrolyte differences between the solutions is not more advantageous with regard to endothelial cell size than dextrose bicarbonate lactated Ringer's solution for standard extracapsular cataract surgery. Cost per 500-microliters bottle of BSS plus is $62 compared with $9.80 for dextrose bicarbonate lactated Ringer's solution.

Effects of irrigation solutions on corneal endothelial function

Rabbit corneas were perfused in vitro with an irrigation solution for 90 minutes. This was followed by 6 hours of perfusion with tissue culture medium TC199 during which endothelial function was assessed by monitoring rates of swelling during a period of perfusion in the absence of bicarbonate ions, and subsequent rates of thinning when bicarbonate ions were restored to the perfusate. Corneal thickness (measured with an ultrasonic pachymeter) immediately following excision was 401 microns (SD 19, n = 23). During the 90 minute perfusion at 35 degrees C, corneas exposed to balanced salt solution (BSS), Hartmann's solution or 0.9% NaCl (all initially at room temperature) swelled, respectively, at 14 (SD 2.3, n = 4), 11 (SD 2.6, n = 4), and 70 (SD 4.3, n = 4) microns/h. Cold Hartmann's solution (initially at 4 degrees C) caused corneas to swell at 9 (SD 2.3, n = 4) microns/h. On the other hand, corneas perfused with BSS Plus thinned at 9 (SD 3.4, n = 4) microns/h and TC199 with Earle's salts had little effect on thickness. Rates of swelling and thinning during the following assessment perfusion showed no apparent effects of prior exposure to any of the irrigation solutions on the barrier properties or pump function of the endothelium. Despite this, the increased thickness of corneas exposed initially to BSS, cold Hartmann's solution, or 0.9% NaCl was not fully reversed, even by the end of the 6 hour assessment perfusion. In contrast, the swelling observed in corneas exposed to Hartmann's solution at room temperature was reversed and these corneas had returned to their normal thickness by the end of the assessment period. All corneas, even those exposed to 0.9% NaCl, had an intact endothelial mosaic with no evidence of damage or cell loss, although morphological differences in cell shape and the appearance of cell borders were evident compared with freshly isolated cornea.

Clinical and histologic effects of extreme intraocular hypothermia

Rabbit eyes in which vitrectomy was performed underwent three hours of hypothermic perfusion with either 22 C or 2 C lactated Ringer's solution. Clinical, electroretinographic, fluorescein angiographic, histologic, and ultrastructural examinations were performed. No changes were noted in eyes cooled with 22 C fluid. Reversible lens opacities, equivocal electroretinographic changes, and subclinical retinal detachments were found in the eyes cooled with 2 C fluid. Extreme cooling of eyes is not advisable, although temperatures of 22 C are well tolerated.

Response of Müller cells following experimental lensectomy-vitrectomy

We used morphological, biochemical and immunohistochemical methods to assess the response of Müller cells after experimental lensectomy-vitrectomy in rabbits. We observed widened intercellular spaces between the Müller cells and nerve fibers of ganglion cells, and increased electron opacity in the Müller cells of eyes injected with silicone oil. No apparent morphological changes were detected in the Müller cells of air-injected eyes. The specific and total activities of Müller cell-marker enzymes (glucose 6-phosphatase and glutamine synthetase) showed an initial increase, followed by a decrease. Glial fibrillary acidic protein immunoreactivity was not found in the Müller cells of the normal rabbit retina but was exhibited after surgery. Our results showed that markers of Müller cells associated with glycogenolysis and/or gluconeogenesis, glutamate-glutamine cycle and cytoskeletal protein metabolism were affected by the experimental lensectomy-vitrectomy.

Comparison of intraocular solutions on glycolysis and levels of ATP and glutathione in the retina

The effects of several intraocular irrigating solutions on the rate of glycolysis and the levels of ATP and glutathione in the isolated rat retina were investigated. The media were HCO3-Ringer, balanced salt solution (BSS) (to which 5 mM glucose was added), and BSS PLUS. There were no significant differences in the metabolic activities and metabolite levels in retinas incubated with either HCO3-Ringer or BSS PLUS. Retinas incubated with BSS PLUS had higher rates of aerobic and anaerobic glycolysis and more ATP than did retinas incubated with BSS. There were no significant differences, however, in the glutathione content of retinas incubated with BSS PLUS and BSS. These results show that retinal energy metabolism is maintained better with BSS PLUS because this irrigating solution contains glucose and bicarbonate.

Role of the intraocular irrigating solutions in the pathogenesis of the postvitrectomy retinal edema

Alterations in the vitreo-retinal barrier can modify the exchange of water taking place between the retina and the vitreous body and cause retinal edema to develop. To verify this fact, albino rabbits were subjected to vitrectomies perfusing various intraocular irrigating solutions for various durations. The following conclusions were drawn from these experiments: Ringer's Lactate and physiological saline solutions are more edematogenous than BSS plus; the induced edema is more severe, the longer the perfusion. We have also confirmed that this edema is inhibited by topically administered indomethacin, which proves that in the rupture of blood-retinal barriers during the vitrectomy, prostaglandins play an important role.

BSS Plus: a potential irrigating solution for neurosurgery

BSS Plus is a pH-stable balanced salt solution similar to glutathione bicarbonate Ringer's solution. Extensively used in ophthalmology, it is of potential value in neurosurgery. In comparative tests of its effectiveness, 28 cats underwent bilateral irrigation of the surface of the cerebral cortex with normal saline on one side and BSS Plus on the other. After 2 hours, a marked decrease was seen in the surface pH of the hemisphere irrigated with normal saline but not of the hemisphere treated with BSS Plus. Blood-brain barrier changes (measured with Evans blue dye techniques) were more evident following saline irrigation. Somatosensory evoked potentials and cerebral blood flow were not significantly altered. Conventional light microscopy using three standard stains did not reveal a significant difference. Transmission electron microscopy studies were performed in 14 animals and scanning electron microscopy in six. In five animals both transmission and scanning electron microscopy studies were conducted after irrigation with both agents without a cottonoid cover and with immediate harvest of superficial layers from the living brain and immersion-fixation in glutaraldehyde. Tissue preservation was superior on the BSS Plus side in all studies. This agent may represent an improved irrigation solution for neurosurgery, but further studies are required.

Electroretinographic studies following vitrectomy and intraocular silicone oil injection

Vitrectomy was performed bilaterally in pigmented rabbits and followed by silicone oil injection in one eye only. Electroretinographic studies were performed preoperatively and at selected postoperative intervals. In the early postoperative period both eyes showed an initial reduction in a and b wave amplitudes, followed by a return to baseline values. The amplitudes were symmetrically and equally affected. Sequential studies over a 20-month period showed no deterioration in electroretinographic response in eyes with and without silicone oil injection.

The effect of intraocular irrigating solutions on lens clarity in normal and diabetic rabbits

We conducted a series of experiments on normal and diabetic rabbits to evaluate the effect of intraocular irrigating solutions on the lens. Lenticular clarity was studied in vivo in eyes undergoing vitreous cavity perfusions with various irrigating solutions. The clarity of isolated lenses incubated in these same solutions was also evaluated. In order to quantitate the cataractous changes observed, we measured the uptake of inulin (tagged with radioactive carbon) by isolated lenses. We found that balanced salt solution (BSS) and BSS Plus maintain excellent lens clarity in normal rabbits; that diabetic lenses are more likely to develop opacification than normal lenses, becoming cataractous when exposed to BSS Plus; and that adding supplemental glucose to BSS Plus allows this solution to maintain excellent lens clarity in diabetic rabbits.

Effects of intraocular irrigating solutions on the electroretinographic b-wave

We studied the effects of physiologic saline, lactated Ringer's solution, and BSS (balanced salt solution) on the electroretinogram of the rabbit in vitro. The b-wave amplitudes decreased when the retina was incubated in lactated Ringer's solution or BSS. These amplitudes recovered to 60% to 70% of the original level when the retina was re-immersed in the control medium. With physiologic saline, the b-wave amplitude recovered only to about 30% after 20 minutes of incubation, and recovery was nil after 60 minutes of incubation time. Extended contact with physiologic saline produced permanent damage to the retina. Bicarbonate ion and glucose were shown to be essential for maintaining the ERG amplitude.

Safety evaluation of BSS plus in pediatric intraocular surgery

An open-label study was conducted to determine the safety of a new intraocular irrigating solution, BSS Plus, when used during pediatric ophthalmic surgery. BBS Plus is a modified glutathione-bicarbonate-Ringer's solution which contains the necessary ions, buffers, and substrates for maintenance of normal cellular metabolism, function, and structural integrity when used as a perfusate during ophthalmic surgical procedures. At three centers, 30 patients undergoing lens aspiration or anterior segment reconstruction using vitrectomy instrumentation were enrolled in this study. Transient postoperative increases in intracellular pressure and internal or external ocular inflammatory signs were seen which were consistent with the trauma produced by the surgical procedure. The solution was judged to be safe when used in these surgical indications.