Comparison of intraocular irrigating solutions in pars plana vitrectomy

Oxidative Stress and Antioxidant-Based Interventional Medicine in Ophthalmology

The different anatomical compartments of the eye are highly subjected to reactive oxygen species (ROS) generation due to internal factors, such as metabolic high oxygen consumption, as well as environmental factors, including UV light. An antioxidant defense system is endowed in the eye tissues to regulate ROS quantity and activity. When this homeostatic system is overwhelmed, oxidative stress occurs, causing cellular damage, chronic inflammation, and tissue degeneration. It also plays a significant role in the development and progression of various ocular diseases. Understanding the mechanisms underlying oxidative stress in ocular conditions is thus crucial for the development of effective prevention and treatment strategies. To track marketed products based on antioxidant substances as active ingredients, the databases of the European Medicines Agency and the U.S. Food and Drug Administration were consulted. Only a limited number of items were identified, which were either used as therapeutic treatment or during ocular surgery, including antioxidants, synthetical derivatives, or pro-drugs designed to enhance tissue permeation and activity. This review aims to provide an overview of the primary ocular pathologies associated with oxidative stress and of the available pharmacological interventions centered around antioxidant molecules. Such insights are essential for advancing the development of effective prevention and novel treatment approaches.

Complications in Retinal Surgery: A Review of Corneal Changes Following Vitreoretinal Procedures

Purpose:

The purpose of this article is to discuss the early- and late-onset corneal complications that can occur following vitreoretinal surgery.

Methods:

A systematic review of the literature was conducted using PubMed and Google Scholar databases. Articles detailing the clinical findings and the associations between surgical techniques, irrigating solutions, and microsurgical instruments used for vitreoretinal surgery and postoperative corneal complications were included in this review.

Results:

Vitreoretinal surgery can be associated with corneal complications such as persistent corneal epithelial defects, neurotrophic keratopathy, band keratopathy, ocular surface disruption, and endothelial cell damage. Risk factors for the development of cornea complications after posterior segment surgery include history of uncontrolled diabetes mellitus, aphakia or pseudophakia, disrupted anterior lens capsule integrity, use of irrigating solutions without appropriate buffers, use of contact viewing lenses intraoperatively, intraocular gases or silicone oil after vitrectomy, and prolonged duration of surgery.

Conclusions:

Corneal complications secondary to vitreoretinal surgery are multifactorial, but more commonly arise in diabetic patients, those with preexisting ocular comorbidities, and under certain surgical-related conditions. Special pre-, peri-, and postoperative considerations, with a focus on early identification and management of risk factors, are required to help decrease the incidence of corneal complications.

Evaluation of corneal endothelial cell damage after vitreoretinal surgery: comparison of different endotamponades

PURPOSE

We evaluated corneal endothelial cell (EC) damage after vitreoretinal surgery and compared the results using different tamponades.

MATERIALS AND METHODS

This prospective controlled study included 45 eyes of 45 patients (24 females, 21 males) who underwent pars plana vitrectomy with gas (sulphur hexafluoride, SF6, 20%) or silicone oil (SO) tamponade. Patients were assigned to one of the three groups: group 1 (phakic, 20% SF6 gas), group 2 (pseudophakic, 20% SF6 gas), and group 3 (phakic, SO). Mean endothelial cell density (MCD), mean cell area (MCA), coefficient of variation in cell size (CV), and percentage of hexagonal cells (HC) values were measured using a non-contact specular microscope (SP-2000P; Topcon, Japan) at baseline and at 3 months after surgery. The fellow eye of each patient was used as a control.

RESULTS

Group 2, which had the lowest baseline MCD and MCA values, was found to be different than groups 1 and 3 (P=0.028 and 0.022, respectively). At 3 months postoperatively, all groups showed significantly lower MCD, HC and CV values than at baseline (all P<0.05). The mean changes in MCD at 3 months after surgery were 3.8±2.8% (mean±SD), 8.0±7.5%, and 4.6±5.4% in groups 1-3, respectively. The mean MCD changes in the fellow eyes were 0.31±1.41% in group 1, -0.63±1.90% in group 2, and 0.14±0.52 in group 3 at 3 months postoperatively (P>0.05 for all).

CONCLUSIONS

Our findings revealed that corneal EC damage may occur after vitreoretinal surgery with gas or SO tamponade. Eyes that had undergone previous cataract surgery were more vulnerable to EC loss than phakic eyes, supporting the protective effect of an intact lens.

Corneal endothelial cell density after vitrectomy with silicone oil for complex retinal detachments

PURPOSE

To evaluate the endothelial cell density changes in eyes with silicone oil tamponade after vitrectomy for complex rhegmatogenous retinal detachment.

METHODS

A prospective controlled study with 81 eyes with complex rhegmatogenous retinal detachment undergoing vitrectomy and silicone oil tamponade. Fellow eyes that fulfilled specific inclusion criteria served as controls. Endothelial cell density (in cells per square millimeter), coefficient of variance (standard deviation per mean cell area × 100), percentage of hexagonal cells, and corneal thickness were documented preoperatively and compared with values obtained at 3, 6, and 12 months postoperatively. For the purpose of the study analysis, all study eyes were divided into 5 groups, according to their lens status during the follow-up.

RESULTS

High endothelial cell density loss was found in Group 3, (eyes that underwent an additional phacoemulsification procedure) and Group 4 (eyes that underwent lens and/or intraocular lens removal during the follow-up) at 12 months with a mean cell loss of 19% and 39%, respectively (P < 0.001).

CONCLUSION

An intact natural or artificial lens-iris diaphragm may provide a protective barrier against corneal endothelial cell damage from long-term silicone oil tamponade.

Risk factors for redetachment and worse visual outcome after silicone oil removal in eyes with complicated retinal detachment

PURPOSE

The goal of this study was to identify risk factors for redetachment and/or a worse visual outcome after silicone oil removal (SOR) for complicated retinal detachment.

METHODS

The authors retrospectively analyzed 287 consecutive eyes with SOR between January 1999 and December 2003.

RESULTS

Anatomic success after SOR was achieved in 81% of the eyes. The overall anatomic success at the end of follow-up was 94%. Postoperative ocular hypertension was found in 8% of the eyes, hypotony in 6% of the eyes, and keratopathy in 29% of the eyes. After SOR 43% of the eyes had an improvement in visual acuity of at least two Snellen lines. After multivariate analysis, male sex, the presence of preoperative rubeosis, and proliferative diabetic retinopathy (PDR) were found to be risk factors for recurrent retinal detachment. Male sex, preoperative visual acuity of <0.1 Snellen lines, PDR, the performance of three more operations, any size of retinectomy, and hypotony were found to be associated with a poor visual outcome of Snellen visual acuity <0.1.

CONCLUSIONS

Retinal detachment after SOR in the current unselected series of eyes occurred in approximately 20%, which is comparable to the Silicone Oil Study reports, published approximately 20 years ago. However, preoperative selection was then made, and less than 50% of the silicone oil-filled eyes had SOR. The higher overall anatomic success in the current study may be due to improved vitreoretinal surgical techniques.

Protective effect of free-radical scavengers on corneal endothelial damage in phacoemulsification

PURPOSE

To examine the role of the water-soluble antioxidants glutathione and ascorbic acid in the irrigating solution on corneal endothelial cells following exposure to high-intensity ultrasound energy.

SETTING

Goldschleger Eye Research Institute, Sheba Medical Center, Tel-Aviv University, Tel Aviv, Israel.

METHODS

Thirty-two rabbit eyes were subjected to prolonged exposure to the phacoemulsification device in the anterior chamber. The eyes were divided into 4 groups that differed only in the composition of the irrigating solution applied to the eyes: balanced salt solution (BSS) BSS Plus BSS containing additional soluble components including glutathione, BSS with 10(-3) M of oxidized glutathione (GSSG), and BSS with 10(-2) M of ascorbic acid. Specular microscopy was performed preoperatively and 1 week after surgery.

RESULTS

The BSS group exhibited the highest endothelial cell loss (19.3%), followed by the BSS Plus group (10.6%), the GSSG group (5.2%), and the ascorbic acid group (0.9%). An overall difference was found between the groups (F = 11.046, P<.0001), and all groups demonstrated a statistically significant difference from the control BSS group (P<.02, P = .001, and P<.0001, respectively).

CONCLUSIONS

Damage to the cornea is largely due to the free radicals generated by high-intensity ultrasound energy during phacoemulsification. Adding the antioxidants ascorbic acid and GSSG to the irrigation solution significantly reduced the endothelial corneal cell damage. Ascorbic acid in the concentration of 10(-2) M had the highest protective effect; thus, it should be evaluated for clinical use.

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.

The effect of elective phacofragmentation on central corneal thickness in the dog

OBJECTIVE

To characterize the short- and intermediate-term effects of elective phacofragmentation on central corneal thickness (CCT) in the dog.

METHODS

Forty-three dogs (66 eyes) undergoing elective phacofragmentation cataract surgery over an 8-month period at a single private ophthalmology referral clinic were enrolled in the study. Central corneal thickness was measured by ultrasonic pachymetry just prior to surgery, 1 day following surgery, 1 week postoperatively, 1 month postoperatively, and more than 2 months postoperatively. Statistical comparisons were made using descriptive and inferential statistical methods with a level of significance set at P < 0.05.

RESULTS

The initial mean CCT of 611 microm increased dramatically to 741 microm 1 day postphacofragmentation. Mean CCT remained slightly elevated (666 microm) at 1 week postoperatively, but became indistinguishable from preoperative measurements by 1 month postsurgery (626 microm) and remained so at the > 2-month time period (618 microm). The change over time and trends remained statistically significant and remarkably similar, even when adjusted separately for age, gender, surgeon status, diabetic status, cataract type, and total surgery time (all P < 0.0001). Corneas of diabetic dogs were thicker than those of nondiabetic dogs at all time periods, and the overall effect of diabetic status was significant (P = 0.016). There was a sharper increase from the preoperative to 1-day postoperative CCT in the diabetic group compared to the nondiabetic group. The mean CCT of the pseudophakic group took longer to return to baseline than the aphakic group. The mean CCT of the foldable intraocular lens (IOL) group took longer to return to baseline than both the rigid IOL and aphakic groups. Dogs with documented in-hospital postoperative intraocular pressure spikes (> 25 mmHg) developed a greater 1-day postsurgical increase in CCT. It appears that there was a sharper decrease in mean CCT from 1 month to more than 2 months postoperatively in the postoperative hypertension group.

CONCLUSIONS

Elective phacofragmentation cataract surgery results in an increase in CCT in dogs, but this increase is transient. Particular care may be indicated to protect the endothelium of diabetic patients undergoing phacofragmentation. These data do not clearly support an advantage of the small-incision cataract surgery made possible by the use of foldable IOLs.

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.