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

Evolution of therapeutic strategy based on oxidant-antioxidant balance for fuchs endothelial corneal dystrophy

Fuchs endothelial corneal dystrophy (FECD) stands as the most prevalent primary corneal endothelial dystrophy worldwide, posing a significant risk to corneal homeostasis and clarity. Corneal endothelial cells exhibit susceptibility to oxidative stress, suggesting a nuanced relationship between oxidant-antioxidant imbalance and FECD pathogenesis, irrespective of FECD genotype. Given the constrained availability of corneal transplants, exploration into non-surgical interventions becomes crucial. This encompasses traditional antioxidants, small molecule compounds, biologics, and diverse non-drug therapies, such as gene-related therapy, hydrogen therapy and near infrared light therapy. This review concentrates on elucidating the mechanisms behind oxidant-antioxidant imbalance and the evolution of strategies to restore oxidant-antioxidant balance in FECD. It provides a comprehensive overview of both conventional and emerging therapeutic approaches, offering valuable insights for the advancement of non-surgical treatment modalities. The findings herein might establish a robust foundation for future research and the therapeutic strategy of FECD.

Comparison of ultrasound energy consumption between low-energy femtosecond laser-assisted cataract surgery and conventional phacoemulsification cataract surgery in patients with different cataract densities

PURPOSE

Femtosecond laser-assisted cataract surgery (FLACS)'s effect on reducing ultrasound energy, accumulated with cumulative dispersed energy (CDE) units, still remains controversial. This study aims to evaluate the effect of low-energy FLACS on CDE with that of conventional phacoemulsification surgery (CPS) in different cataract densities from multiple surgeons.

METHODS

It was a retrospective case-control study. Total 629 eyes receiving either low-energy FLACS (performed with Ziemer LDV Z8 platform) or CPS were divided into two groups according to preoperative grading of Lens Opacity Classification System III (LOCSIII): milder and harder cataract group. The mean CDE were compared in different cataract densities and surgeons. A linear regression analysis was performed to evaluate the effect of using low-energy FLACS on CDE in harder cataract cases.

RESULTS

We found overall CDE had no significant difference between two surgeries. However, low-energy FLACS led to a significantly lower CDE in patients with harder cataracts than CPS (18.47 ± 4.32 vs. 12.96 ± 2.34; p < 0.001). Similar results were observed in the three surgeon subgroups and in linear regression analysis and no significant difference of the effect accounting for surgeons. Moreover, low-energy FLACS results in a reduction of energy consumption comparing to CPS and has endothelial sparring effect in patients with harder cataracts.

CONCLUSIONS

The reduced energy consumption was observed by using low-energy FLACS irrespective of surgeons' experience or the approaches adopted in patients with harder cataracts. Therefore, we can have more confidence to suggest this innovative platform to the patients in such cases.

Effect of simulated lenticular debris on corneal endothelial cells: experimental study in rabbit eyes

PURPOSE

To evaluate mechanical damage of simulated lenticular debris on corneal endothelial cells during phacoemulsification.

SETTING

University setting, Salt Lake City, Utah.

DESIGN

Experimental study.

METHODS

12 New Zealand rabbits underwent bilateral surgery. After incision, 10 1.0 mm beads were injected into the anterior chamber of test eyes to simulate lenticular debris. A balanced salt solution was injected into the contralateral eyes with the same injector. The Intrepid Balanced Tip of the Centurion Ozil handpiece was inserted into the anterior chamber, and 60% torsional ultrasound was applied for 20 seconds with 50 mL/min flow, 70 mm Hg intraocular pressure, and 600 mm Hg vacuum. Cumulative dissipated energy (CDE) was noted. After euthanasia and enucleation, the corneas were removed, stained with trypan blue/alizarin red, and photographed in a standardized manner (×400 photographs from 5 specific areas and 1 overview photograph from each corneal button). The ImageJ program was used to evaluate cell damage and loss in the photographs.

RESULTS

CDE was 4.64 ± 0.19 for test eyes with beads and 4.66 ± 0.17 for control eyes without beads ( P = .58). The percentage of intact cells was statistically higher in the control group ( P = .0005), whereas the percentages of damaged and lost cells were statistically higher in the test group ( P = .0010 and .0005, respectively). This was observed in the analysis of the ×400 photographs and overview photographs.

CONCLUSIONS

This study suggests that lenticular debris swirling around the anterior chamber may cause significant damage to the corneal endothelium, providing further insight on mechanisms of damage during phacoemulsification.

Successful Phakic Intraocular Lens Implantation with the Usage of Topical Ascorbic Acid in Patient with Reduced Corneal Endothelial Cell Density

We aimed to describe the use of topical ascorbic acid (AA) in a patient with reduced endothelial cells density (ECD) who was scheduled for phakic intraocular lens (pIOL) implantation. A 28-year-old woman presenting with dry eye and reduced ECD would like to have her high myopia (spherical equivalence >−15.0 D) corrected. The procedure of laser refractive surgery or even pIOL was not indicated for the reduced ECD of 1865/mm2 in the right eye and 2188/mm2 in the left eye, as well as level 3 dry eye. Fortunately, the ECD increased to 3144/mm2 in the right eye and 2538/mm2 in the left eye after topical AA was prescribed for one year preoperatively and one month postoperatively, with concomitant improvement of dry eye to level 1. Finally, bilateral pIOL implantation was performed smoothly and no sign of corneal decompensation was found postoperatively. Three months postoperatively, the ECD showed a satisfactory level of 2983/mm2 in the right eye and 3003/mm2 in the left eye. In conclusion, topical AA instillation might increase and maintain the density of central human corneal endothelial cells (HCECs) even after pIOL implantation.

Factors impacting cumulative dissipated energy levels and postoperative visual acuity outcome in cataract surgery

Purpose

To determine factors impacting cumulative dissipated energy (CDE) and postoperative best-corrected visual acuity (BCVA) in phacoemulsification.

Design

Review of 1102 cases at University of California, San Francisco (UCSF) and at Zhongshan Ophthalmic Center (ZOC), China.

Subjects

Patients who underwent cataract surgery at UCSF 03/2014–03/2019 and at ZOC 10/2018–05/2019.

Methods

Patient demographics, medical history, routine ocular examination, and surgical information, including disassembly method, complications, and surgeon training level were recorded. Univariable and multivariable regression models were used to determine factors associated with CDE and good postoperative BCVA (20/40 or better) at 1 month.

Outcome measures

CDE, postoperative BCVA.

Results

In multivariable analysis, patient age at time of surgery, diabetes, degree of nuclear sclerosis (NS), white-to-white corneal diameter, disassembly method, preoperative BCVA, surgeon training level, and surgical center were significantly associated with CDE. Log₁₀CDE increased by 0.20–0.31 for patient age ≥ 70 years, by 0.07 if the patient had diabetes, by 0.12–0.41 for NS grade ≥ 2, by 0.48 per 10 mm increase in white-to-white corneal diameter, by 0.34–0.47 for disassembly method other than non-stop chop, by 0.16 per unit increase in preoperative logMAR BCVA, and by > 0.09 when phacoemulsification was performed by residents early in their training. Log₁₀CDE was 0.33 higher at UCSF than ZOC. In multivariable analysis, worse baseline visual acuity and age above 90 years at time of surgery decreased the odds of good BCVA (OR = 0.26 per unit increase in preoperative logMAR BCVA; OR = 0.12 for age > 90); comorbid retinal issues decreased the odds of good postoperative BCVA (OR = 0.13–0.39); greater anterior chamber depth (ACD) or shorter axial length (AL), increased the odds of good postoperative outcome (OR = 2.64 per 1 mm increase ACD, OR = 0.84 per 1 mm increase AL).

Conclusions

Cataract grade determined by slit lamp exam and, for the first time, older patient age, were noted to be important predictors of high CDE. CDE was not a risk factor for postoperative BCVA measured at postoperative 1 month. When surgery was performed by trainees under supervision, lower training level was associated with higher CDE, but not with worse postoperative BCVA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-021-02205-w.

The effect of phacoemulsification fluid flow on the corneal endothelium: An experimental study in rabbit eyes

PURPOSE

To quantify the damage to the corneal endothelium from the flow of balanced salt solution during phacoemulsification.

SETTING

John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA.

DESIGN

Experimental Study.

METHODS

Twelve New Zealand white rabbits received bilateral surgery. Six eyes served as controls with no irrigation (incision only). In 18 eyes, the Intrepid Balanced tip of the Centurion (Alcon) Ozil handpiece was inserted into the anterior chamber for continuous irrigation at 50mL/minute with either 250 mL or 500 mL of balanced salt solution (BSS). After euthanasia and enucleation, the corneas were removed, stained with trypan blue/alizarin red, and photographed in a standardized manner (X400 photographs from 5 specific areas, and 1 overview photograph from each corneal button). The ImageJ program was used to evaluate cell damage and loss in the photographs obtained from each cornea.

RESULTS

Analysis of the X400 photographs showed no statistical differences between control, 250 mL, and 500 mL groups in the percentage of intact, damaged, or lost cells (P= 0.896, 0.851, and 0.972 respectively). For the overview photos, the differences in areas of intact and damaged cells among the groups were statistically significant, likely due to the peripheral areas of damage related to touches between the phaco tip and the endothelium during irrigation.

CONCLUSION

The volume of BSS flow alone does not appear to be a major contributing source of endothelial cell damage and loss, providing further insight on mechanisms of corneal endothelium damage during phacoemulsification.

Comparison of cumulative dispersed energy between conventional phacoemulsification and femtosecond laser-assisted cataract surgery with two different lens fragmentation patterns

The purpose of the study is to compare the total ultrasound power used between eyes undergoing different lens fragmentation patterns of femtosecond laser-assisted cataract surgery (FLACS) and conventional phacoemulsification surgery (CPS). A total of 506 patient eyes underwent preoperative grading of lens opacity using the Lens Opacity Classification System III (LOCSIII). The eyes were divided into two subgroups: subgroup 1 had a LOCSIII grade of 1-3, and subgroup 2 had a LOCSIII grade of 4-6. The eyes underwent FLACS (LenSx) for clear corneal wound, capsulotomy, and lens fragmentation. Either a grid pattern or radial pattern was used for lens fragmentation. The eyes received one of the following three treatments: (1) CPS without femtosecond laser assistant, (2) FLACS with a grid pattern (FGP) lens fragment, or (3) FLACS with a quadrant pattern (FQP) lens fragment. The mean cumulative dispersed energy (CDE) for each subgroup and treatment was evaluated. The mean CDE was lower in the two FLACS groups (1.21±1.91 in FGP and 1.22±1.92 in FQP) than that in the CPG group (2.67±2.84). In subgroup 1, CDE was higher in the CPG group (1.54±1.18) as compared with the FLACS groups (0.16±0.31 in FGP and 0.74±1.17 in FQP; P<0.001). In subgroup 2, CDE was higher in the CPG (6.47±3.46) as compared with the FLACS groups (2.74±2.21 in FGP and 5.34±2.17 in FQP; P<0.001). CDE was lower in the two FLACS groups than that in the CPS group, and CDE was the lowest with FGP in both subgroups 1 and 2.

Tumor necrosis factor-alpha and interferon-gamma induce inflammasome-mediated corneal endothelial cell death

PURPOSE

Chronic corneal endothelial cell (CEC) loss results in corneal edema and vision loss in conditions such as pseudophakic bullous keratopathy (PBK), Fuchs' dystrophy, and corneal graft failure. Low CEC density has been associated with an elevation of intraocular pro-inflammatory cytokines such as tumor necrosis factor (TNF)-α and interferon (INF)-γ. These cytokines are capable of triggering pyroptosis, a programmed cell death mechanism mediated by the inflammasome, prompting the activation of the pro-inflammatory cytokine interleukin (IL)-1β, the perpetuation of inflammation, and subsequent damage of corneal endothelial tissue. Therefore, the purpose of this study was to determine the deleterious contribution of the inflammasome and pyroptosis to CEC loss.

METHODS

CECs from human donor corneas were treated ex vivo with TNF-α and IFN-γ for 48 h. Levels of caspase-1 and IL-1β were then assayed by ELISA, and the expression of caspase-1 and gasdermin-D (GSDM-D) were confirmed by immunofluorescence. Endothelial cell damage was analyzed by a lactate dehydrogenase (LDH) release assay, and oxidative stress was determined by measuring the levels of reactive oxygen species (ROS) in the culture media.

RESULTS

Inflammasome activation and oxidative stress were elevated in CECs following exposure to TNF-α and IFN-γ, which resulted in cell death by pyroptosis as determined by LDH release which was inhibited by the caspase-1 inhibitor Ac-YVAD-cmk.

CONCLUSION

CEC death is induced by the pro-inflammatory cytokines TNF-α and IFN-γ, which contribute to inflammasome activation. Moreover, the inflammasome is a promising therapeutic target for the treatment of chronic CEC loss.

Clinical Comparison of the Performance of Two Marketed Ophthalmic Viscoelastic Devices (OVDs): The Bacterially Derived Healon PRO OVD and Animal-Derived Healon OVD

This clinical investigation compared the clinical performance of two marketed ophthalmic viscoelastic devices (OVDs): the bacterially derived Healon PRO OVD (test) and the animal-derived Healon OVD (control) under normal use conditions during cataract removal and lens implantation. This prospective, multicenter, randomized, parallel, participant/evaluator masked, postmarket investigation enrolled 139 subjects (170 eyes), 116 (143 eyes) of which were treated (73 test; 70 control group). Both test and control OVDs were used, at a minimum, to inflate the anterior chamber and protect the endothelium prior to cataract extraction according to the standard procedure. The surgeon completed a postsurgery OVD clinical performance questionnaire, and intraocular pressure (IOP) was measured before surgery and at the 1 day postoperative visit with Goldmann applanation tonometry. Any IOP measurement of 30 mmHg or higher was considered a “spike” and recorded as a study-specific, serious adverse event. The bacterially derived Healon PRO OVD was found to be statistically noninferior to the overall clinical performance of the animal-derived Healon OVD control; thus, the primary hypothesis was satisfied. There were no statistically significant differences between OVD groups for any of the additional endpoints relating to IOP changes or to safety, thus satisfying additional hypotheses. The Healon PRO OVD showed statistically significant improvements in surgeon ratings for ease of injectability, transparency/visibility, and ease of IOL placement. The safety profile was also similar between OVD groups with regards to serious and/or device-related adverse events, as well as medical and lens findings. The results of this clinical investigation support the safety and effectiveness of the bacterially derived, currently marketed Healon PRO OVD and indicate that the intraocular surgical performance was similar between the two OVDs.

Topical Ascorbic Acid Ameliorates Oxidative Stress-Induced Corneal Endothelial Damage via Suppression of Apoptosis and Autophagic Flux Blockage

Compromised pumping function of the corneal endothelium, due to loss of endothelial cells, results in corneal edema and subsequent visual problems. Clinically and experimentally, oxidative stress may cause corneal endothelial decompensation after phacoemulsification. Additionally, in vitro and animal studies have demonstrated the protective effects of intraoperative infusion of ascorbic acid (AA). Here, we established a paraquat-induced cell damage model, in which paraquat induced reactive oxygen species (ROS) production and apoptosis in the B4G12 and ARPE-19 cell lines. We demonstrate that oxidative stress triggered autophagic flux blockage in corneal endothelial cells and that addition of AA ameliorated such oxidative damage. We also demonstrate the downregulation of Akt phosphorylation in response to oxidative stress. Pretreatment with ascorbic acid reduced the downregulation of Akt phosphorylation, while inhibition of the PI3K/Akt pathway attenuated the protective effects of AA. Further, we establish an in vivo rabbit model of corneal endothelial damage, in which an intracameral infusion of paraquat caused corneal opacity. Administration of AA via topical application increased its concentration in the corneal stroma and reduced oxidative stress in the corneal endothelium, thereby promoting corneal clarity. Our findings indicate a perioperative strategy of topical AA administration to prevent oxidative stress-induced damage, particularly for those with vulnerable corneal endothelia.

Perioperative topical ascorbic acid for the prevention of phacoemulsification-related corneal endothelial damage: Two case reports and review of literature

BACKGROUND

The current case report describes successful phacoemulsification with the aid of perioperative topical ascorbic acid (AA) in two patients with corneal endothelial disorders to prevent postoperative corneal endothelial decompensation.

CASE SUMMARY

Two eyes of two patients underwent phacoemulsification with pre-existing corneal endothelial disorders including Fuchs corneal endothelial dystrophy (Patient 1) and endotheliitis (Patient 2). Topical AA was applied to both patients at least one month before and after with a frequency of four times per day. After the surgery, both eyes improved best-corrected visual acuity (BCVA) and there was limited human corneal endothelial cell loss without signs of corneal endothelial decompensation, such as deteriorated BCVA or persistent corneal edema during the follow-up of at least two years.

CONCLUSION

Perioperative administration of topical AA may be an alternative therapy to the triple procedure in patients expecting to undergo cataract surgery.

Comparison of surgical parameters using different lens fragmentation patterns in eyes undergoing laser-assisted cataract surgery

PURPOSE

To compare surgical parameters among eyes undergoing laser-assisted cataract surgery (LACS) using different lens fragmentation patterns (LFP).

METHODS

Prospective, randomized, unmasked clinical trial. One-hundred eyes underwent LACS and were randomly assigned to 1 of 3 LFP treatment groups: (1) laser capsulotomy only; no lens fragmentation (NLF) (n = 34); (2) three-plane chop (TPC) (n = 33); and, (3) pie-cut pattern (PCP) fragmentation (n = 33). Prechop phacoemulsification (PHACO) was performed on all eyes using the same femtosecond (FS) laser and active-fluidics PHACO machine.

MAIN OUTCOME MEASURES

FS laser dock time (s), PHACO time (s), PHACO power (%), cumulative dissipated energy (CDE) (%-s), irrigating fluid volume, and operative time.

RESULTS

The 3 treatment groups were comparable in terms of patient age (P = 0.164) and nuclear density (P = 0.669). FS dock time was higher in the PCP group (184.18 ± 25.86) compared to the TPC (145.09 ± 14.15) group (P < 0.001). PHACO time was significantly shorter in the PCP (23.19 ± 17.20 s) compared to TPC (35.27 ± 17.70) and NLF (46.15 ± 23.72) groups (P < 0.001). PHACO power was lower in the PCP (11.81 ± 3.71) compared to the NLF (14.41 ± 1.88) and TPC (14.04 ± 2.46) groups (P < 0.001). CDE was lower in the PCP (2.85 ± 2.32) compared to NLF (6.55 ± 3.32) and TPC (6.55 ± 5.45) groups (P < 0.001). Fluid volumes and operative times were similar.

CONCLUSION

LFP can influence PHACO surgical parameters. Extensive fragmentation patterns such as PCP appear to lower PHACO time, power, and CDE and may potentially reduce the risk of PHACO related complications.

Reduced aqueous humour ascorbic-acid concentration in women with smaller anterior chamber depth

Short anterior chamber depth (ACD) is considered a risk factor of endothelial-cell loss after phacoemulsification. However, whether it is an independent risk factor or not remains controversial. We investigated the relationship between ascorbic acid (AA) concentrations in the aqueous humour (AqH) and ACD. We analysed 165 AqH samples of 97 patients (42 men and 55 women) who underwent small incision cataract surgery. AqH and plasma AA concentrations were measured using a high-performance liquid chromatography - electrochemical detection method. Patient characteristics were compared between and within the sexes. As a result, age and ACD were significantly correlated with AqH AA concentrations (r = −0.206, P = 0.045; r = 0.339, P < 0.001) only in women. Moreover, plasma AA concentrations were significantly correlated with AqH AA concentrations (r = 0.420, P < 0.001; r = 0.316, P = 0.002) both in men and women. After adjusting for confounding factors (age and plasma AA concentrations), ACD was significantly and positively correlated with AqH AA concentrations (partial.r = 0.275, P = 0.009) only in women. In conclusion, AqH AA concentrations were reduced in women with smaller ACD. This may suggest that women with short ACD could be more susceptible to oxidative damage.

Effects of intracameral ascorbic acid on the corneal endothelium of dogs undergoing phacoemulsification

OBJECTIVE

Cataracts are the most common ocular disorder in dogs. Phacoemulsification is the preferred treatment method among ophthalmologists, but the cellularity of the endothelium must be considered for its success, as endothelial lesions may produce permanent corneal decompensation. The objective of this study was to evaluate the effects of intracameral ascorbic acid, a known antioxidant, on the corneal endothelium of dogs undergoing phacoemulsification.

ANIMAL STUDIED

In all, 40 eyes from 20 dogs, males and females from 7 to 12 years of age, were assessed for mature cataracts.

PROCEDURES

Two groups were formed (n = 20): Group 1 (G1) received a balanced salt solution (BSS), whereas Group 2 (G2) received sterile ascorbic acid diluted in a BSS, at a final concentration of 0.001 m ascorbic acid. The corneal endothelium was assessed via non-contact specular microscopy at multiple time points before and after phacoemulsification. Cell density (cells/mm² ) and area (mm² ), corneal thickness (mm), hexagonality, and the coefficient of variation of cell size were all assessed. P values equal to or less than 0.05 were considered significant.

RESULTS

With respect to the density of endothelial cells, both groups showed losses, but they were less severe in G2. There were no differences in corneal thickness. Hexagonality decreased significantly in the postoperative period in G1. Also in G1, the coefficient of variation of cell size increased significantly.

CONCLUSION

According to the results obtained, ascorbic acid minimizes cellular losses in the corneal endothelium.

Hydrogen prevents corneal endothelial damage in phacoemulsification cataract surgery

In phacoemulsification, ultrasound induces hydroxyl radical (·OH) formation, damaging corneal endothelium. Whether H2 can prevent such oxidative damage in phacoemulsification was examined by in vitro and in vivo studies. H2 was dissolved in a commercial irrigating solution. The effects of H2 against ·OH generation were first confirmed in vitro by electron-spin resonance (ESR) and hydroxyphenyl fluorescein (HPF). ESR showed a significantly decreased signal magnitude, and fluorescence intensity by oxidized HPF was significantly less in the H2-dissolved solution. The effects of H2 in phacoemulsification were evaluated in rabbits, comparing H2-dissolved and control solutions. Five hours after the procedure, the whole cornea was excised and subjected to image analysis for corneal edema, real-time semiquantitative PCR (qPCR) for heme oxygenase (HO)-1, catalase (CAT), superoxide dismutase 1 (SOD1), and SOD2 mRNA, and immunohistochemistry. Corneal edema was significantly less and the increases in anti-oxidative HO-1, CAT and SOD2 mRNA expressions were significantly suppressed in the H2 group. In addition, corneal endothelial cell expressions of two oxidative stress markers, 4-HNE and 8-OHdG, were significantly lower in the H2 group. In conclusion, H2 dissolved in the ocular irrigating solution protected corneal endothelial cells from phacoemulsification-induced oxidative stress and damage.

A clinical comparison of safety and efficacy in phacoemulsification with versus without ophthalmic viscoelastic device

PURPOSE

To evaluate in a comparative manner the safety and efficacy of 1.0% sodium-Hyaluronate used during capsulorhexis and intraocular lens (IOL) implantation in phacoemulsification surgery.

MATERIALS AND METHODS

1.0% sodium-Hyaluronate, which is commonly used as one of the ophthalmic viscoelastic devices, was compared to intraocular irrigating solution, which can bring up these effects. In addition, the effect of both methods on occurring corneal endothelial cell (CEC) loss was investigated.

RESULTS

Each group comprised 19 eyes. The mean preoperative CEC density was 2525.68 ± 181.85 in Group H and 2514.16 ± 174.59 in Group V; no statistically significant difference was found between the groups (p > 0.05). Preoperative and postoperative first and twelfth week CEC densities were 2438.21 ± 198.12 (p < 0.001) and 2390.74 ± 202.31, respectively, in group H (p < 0.001). Preoperative and postoperative first and twelfth week CEC densities were 2415.32 ± 197.24 (p < 0.001) and 2353.47 ± 212.69 in group V (p < 0.001). Compared with preoperative values, decrease in CEC density on the postoperative first and twelfth weeks was not statistically significant in either group (p > 0.05).

CONCLUSION

Although it was found that there was no statistically difference in terms of preventing CEC loss between 1.0% sodium-Hyaluronate and the irrigation method during phacoemulsification, it was observed clinically that 1.0% sodium-hyaluronate can make the procedure easy, safer, very helpful, especially for understanding phacoemulsification.

Environmental light and endogenous antioxidants as the main determinants of non-cancer ocular diseases

The human eye is constantly exposed to sunlight and artificial lighting. Exogenous sources of reactive oxygen species (ROS) such as UV light, visible light, ionizing radiation, chemotherapeutics, and environmental toxins contribute to oxidative damage in ocular tissues. Long-term exposure to these insults places the aging eye at considerable risk for pathological consequences of oxidative stress. Furthermore, in eye tissues, mitochondria are an important endogenous source of ROS. Over time, all ocular structures, from the tear film to the retina, undergo oxidative stress, and therefore, the antioxidant defenses of each tissue assume the role of a safeguard against degenerative ocular pathologies. The ocular surface and cornea protect the other ocular tissues and are significantly exposed to oxidative stress of environmental origin. Overwhelming of antioxidant defenses in these tissues clinically manifests as pathologies including pterygium, corneal dystrophies, and endothelial Fuch's dystrophy. The crystalline lens is highly susceptible to oxidative damage in aging because its cells and their intracellular proteins are not turned over or replaced, thus providing the basis for cataractogenesis. The trabecular meshwork, which is the anterior chamber tissue devoted to aqueous humor drainage, has a particular susceptibility to mitochondrial oxidative injury that affects its endothelium and leads to an intraocular pressure increase that marks the beginning of glaucoma. Photo-oxidative stress can cause acute or chronic retinal damage. The pathogenesis of age-related macular degeneration involves oxidative stress and death of the retinal pigment epithelium followed by death of the overlying photoreceptors. Accordingly, converging evidence indicates that mutagenic mechanisms of environmental and endogenous sources play a fundamental pathogenic role in degenerative eye diseases.

Preclinical safety and stability study of a next generation telescope prosthesis for end-stage macular degeneration

BACKGROUND

To assess the surgical procedure, safety and stability of a next generation injectable telescope prosthesis in a rabbit model.

METHODS

After removal of the crystalline lenses of eight New Zealand White rabbits, the next generation device was randomly implanted in one eye, and the available telescope prosthesis (Normal device) was implanted in the fellow eye. Operative parameters (incision, capsulorrhexis size and operative time), intraoperative and postoperative complications rates, endothelial cell density changes and the distance between the corneal endothelium and the telescope (central clearance distance) were measured and compared between the groups.

RESULTS

Incision size and capsulorrhexis size were smaller, and operative time was shorter in the next generation group in comparison with the Normal group. No difference was found in the intraoperative and postoperative complication rates between the groups. Endothelial cell density loss observed in the next generation group was less than the loss in the Normal group, but the difference was not significant statistically. The central clearance distance was significantly larger in the next generation group in comparison with the Normal group (P = 0.001).

CONCLUSIONS

The next generation telescope was implanted through a smaller incision, with a shorter surgical time and a larger central clearance distance in the rabbit eyes, in comparison with the Normal group. The next generation device may allow reduced trauma to the corneal endothelium, better control during surgery and induce less astigmatism while preserving the optical advantages of the Food and Drug Administration-approved telescope prosthesis.

Outcomes of cataract surgery in eyes with a low corneal endothelial cell density

PURPOSE

To evaluate the surgical outcomes of cataract surgery in eyes with a low preoperative corneal endothelial cell density (ECD) and analyze factors affecting the prognosis.

SETTING

Tokyo Dental College, Ichikawa General Hospital, Chiba, Japan.

DESIGN

Noncomparative case series.

METHODS

Eyes with a preoperative ECD of less than 1000 cells/mm(2) that had cataract surgery between 2006 and 2010 were identified. Standard phacoemulsification with intraocular lenses was performed using the soft-shell technique. The rate of endothelial cell loss, incidence of bullous keratopathy, and risk factors were retrospectively assessed.

RESULTS

Sixty-one eyes (53 patients) with a low preoperative ECD were identified. Preoperative diagnoses or factors regarded as causing endothelial cell loss included Fuchs dystrophy (20 eyes), laser iridotomy (16 eyes), keratoplasty (10 eyes), traumatic injury (3 eyes), trabeculectomy (3 eyes), corneal endotheliitis (2 eyes), and other (7 eyes). The corrected distance visual acuity improved from 0.59 ± 0.49 logMAR preoperatively to 0.32 ± 0.48 logMAR postoperatively (P<.001). The mean ECD was 693 ± 172 cells/mm(2) and 611 ± 203 cells/mm(2), respectively (P=.001). The mean rate of endothelial cell loss was 11.5% ± 23.4%. Greater ECD loss was associated with a shorter axial length (AL) (<23.0 mm) and diabetes mellitus. Bullous keratopathy developed in 9 eyes (14.8%) and was associated with posterior capsule rupture.

CONCLUSIONS

The results suggest that modern techniques for cataract surgery provide excellent visual rehabilitation in many patients with a low preoperative ECD. Shorter AL, diabetes mellitus, and posterior capsule rupture were risk factors for greater ECD loss and bullous keratopathy.

Protective effect of different ophthalmic viscosurgical devices on corneal endothelium during severe phacoemulsification model in rabbits

BACKGROUND AND OBJECTIVE

To evaluate the protective effect of different ophthalmic viscosurgical devices (OVDs) on corneal endothelial cells against relatively severe phacoemulsification damage in a rabbit model.

MATERIALS AND METHODS

Twenty-four rabbit eyes were randomly assigned to four similar groups: in three groups the aqueous humor was completely replaced by Visiol (TRB CHEMEDICA, München, Germany), Biolon (Bio-Technology General Ltd., Kiryat Malachi, Israel), and Viscoat (Alcon, Puurs, Belgium) and in the control group no OVD was applied. Endothelial cell counts were performed prior to initiating the study. All eyes were exposed to continuous 5 minutes of phacoemulsification. Endothelial cell counts were repeated 4 days postoperatively.

RESULTS

Viscoat showed the highest endothelial cell loss (30%), followed by Biolon (25%), Visiol (22%), and the control group (19%). None of the differences between the groups were found to be statistically significant, although they were within each group (P = .028).

CONCLUSION

None of the tested OVDs demonstrated protective effect on corneal endothelial cells in comparison to the control group. This model was found to be too aggressive for the demonstration of the protective effect of different OVDs even for hard cataract.

Evaluation of phacoemulsification-induced oxidative stress and damage of cultured human corneal endothelial cells in different solutions using redox fluorometry microscopy

PURPOSE

To describe the basic concept of redox fluorometry microscopy and investigate its efficacy in evaluating the state of cultured human corneal endothelial cells in different solutions when ultrasonic energy was applied in vitro.

METHODS

Human corneal endothelial cells from human donor tissue not suitable for transplantation were cultured. A phacoemulsification probe with a 30° round, 1.1-mm TurboSonics(®) ABS™ Tip (Alcon, Fort Worth, Texas) was introduced into culture dishes filled with balanced salt solution (BSS) and BSS plus (Alcon, Fort Worth, Texas). Cellular autofluorescence images were obtained using a Zeiss inverted microscope. The redox fluorometric ratio, which can be related to cellular metabolism, mitochondrial distribution patterns, which can shift in reaction to environmental changes, and cell size were analysed with a software program.

RESULTS

Human corneal endothelial cells exposed to increasing phacoemulsification times and ultrasonic energy displayed dose-dependent decreases in redox ratios. At a lower ultrasonic power and time, BSS plus showed significantly less change in redox ratio than BSS and control (p < 0.05, Mann-Whitney test). As ultrasonic power and time increased, BSS plus had no more significance.

CONCLUSION

Redox fluorometry, with further technological improvement, might be an interesting and potentially useful tool for evaluation of phacoemulsification-induced corneal endothelial damage and screening of protective agents in vitro.

Quantification of hydroxyl radical produced during phacoemulsification

PURPOSE

To quantitate hydroxyl radicals produced during phacoemulsification with various irrigating solutions and conditions used in cataract surgery.

SETTING

Chemistry and Biochemistry Department, Utah State University, Logan, Utah, USA.

METHODS

All experiments were performed using an Infiniti Vision System phacoemulsifier with irrigation and aspiration. Hydroxyl radicals were quantitated using electron spin resonance spectroscopy and a spectrophotometric assay for malondialdehyde, which is formed by the oxidation of deoxyribose by the hydroxyl radical.

RESULTS

Hydroxyl radical production increased during longitudinal-stroking phacoemulsification as power levels were increased in a nonlinear, nonexponential fashion. The detection of hydroxyl radical was reduced in irrigating solutions containing organic molecules (eg, citrate, acetate, glutathione, dextrose) and further reduced in Navstel, an irrigating solution containing a viscosity-modifying agent, hydroxypropyl methylcellulose.

CONCLUSIONS

Hydroxyl radicals produced in settings representative of those used in phacoemulsification cataract surgery were quantitated using the deoxyribose method. Hydroxyl radical production was dependent on the level of ultrasound power applied and the irrigating solution used. Oxidative stress on the eye during phacoemulsification may be minimized by using irrigating solutions that contain organic molecules, including the viscosity-modifying agent hydroxypropyl methylcellulose, that can compete for reaction with hydroxyl radicals.

Comparison between Ringer's lactate and balanced salt solution on postoperative outcomes after phacoemulsfication: a randomized clinical trial

Aim:

To compare the effects of balanced salt solution (BSS) and Ringer's lactate (RL) on corneal thickness, endothelial morphology, and postoperative anterior chamber inflammation in eyes undergoing phacoemulsification.

Setting:

Iladevi cataract and IOL research center, Ahmedabad, India.

Materials and Methods:

This prospective randomized study comprised 90 consecutive patients with age-related cataract who were randomly assigned to either Group 1 (n = 45) with BSS or Group 2 (n = 45) with RL. Observations made included measurement of central corneal thickness (CCT), presence of anterior chamber flare and cells, endothelial cell loss, and change in coefficient of variation (CV). Data was analyzed using Mann Whitney test and test of proportion.

Results:

Mean increase in CCT on postoperative Day 1 was 58 µm and 97 µm in Groups 1 and 2 respectively (P = 0.01). Increase in CCT at one month was 10µm and 11µm in Groups 1 and 2 respectively (P = 0.99); increase in CCT at three months was 3 µm and 6 µm in Groups 1 and 2 respectively (P = 0.86). Number of eyes with flare grades in a range of 0 to 3 was statistically higher in Group 2 on postoperative Day 1 (P = 0.004, 0.016, <0.001, 0.047 for Grade 0, 1, 2 and 3 respectively). Number of eyes with cells of Grade 3 on first postoperative day was significantly higher in Group 2 as compared to Group 1 (P = 0.004). Three months postoperatively, endothelial cell loss was 5.5% and 7.8% in Groups 1 and 2 (P = 0.21) and change in CV was 3 and 5.4 in Groups 1 and 2 (P = 0.20) respectively.

Conclusion:

BSS offers a significant advantage over RL in terms of increase in corneal thickness and postoperative inflammation on the first postoperative day in patients undergoing phacoemulsification.

Presoaking donor corneas reduces graft detachment rates in descemet stripping endothelial keratoplasty

PURPOSE

To present a novel method of reducing rates of graft detachment, the most common postoperative complication of Descemet stripping endothelial keratoplasty (DSEK).

DESIGN

Retrospective, interventional case series.

METHODS

Eighty-three consecutive patients undergoing DSEK for endothelial dystrophy were studied. DSEK was performed in 103 eyes by 2 surgeons (J.D.G. and W.J.S.) at one institution before (n = 83) and after (n = 20) presoaking donor grafts in balanced salt solution (BSS) Plus (Alcon, Fort Worth, Texas, USA). No significant change in the frequency of using other techniques was made during this time. Incidents of tissue detachment after surgery were recorded.

RESULTS

Of 83 consecutive DSEK procedures carried out before presoaking the donor tissue in BSS Plus, detachment occurred in 25 (30%). After presoaking, the detachment rate was reduced significantly to 0 (0%) of 20 (P = .0019).

CONCLUSIONS

Patients undergoing DSEK experienced a significant decrease in rates of graft detachment after adoption of this new technique. The results suggest that presoaking donor tissue in BSS Plus lowers the detachment rate of DSEK grafts.

Cytoprotective role of mitogen-activated protein kinase phosphatase-1 in light-damaged human retinal pigment epithelial cells

The role of the mitogen-activated protein (MAP) kinase phosphatases (MKPs) in light-damaged cells is unclear. Therefore we investigated the involvement of MKP-1 in the regulation of apoptosis and cell survival mediated by MAP kinase pathways in light-damaged human retinal pigment epithelial cells (ARPE-19). Light dose-dependent changes in the expression of MKP-1 and in the phosphorylation status of the MAP kinases, c-Jun-N-terminal kinase (JNK) and p38 were demonstrated. Low light doses up to 2 J cm(-2) led to an upregulation of MKP-1 which resulted in the prevention of cell death by inactivating JNK kinase. However, higher light doses (> or =3 J cm(-2)) significantly reduced MKP-1 protein expression and subsequently led to an increased JNK kinase activity followed by a significant increase in cell death. JNK kinase inactivation by the JNK inhibitor SP600125 significantly reduced light-induced cell death, suggesting that the cytoprotective properties of MKP-1 are mediated mainly by the JNK MAP kinase pathway. Physiological concentrations of ascorbic acid or taurine were seen to prevent apoptosis and cell death in light-damaged ARPE-19 cells by reducing oxidative stress within cells, thus maintaining MKP-1 at high levels, leading to an inactivation of the JNK kinase pathway which resulted in an increased cell viability.

Soft-shell technique using Viscoat and Healon 5: a prospective, randomized comparison between a dispersive-viscoadaptive and a dispersive-cohesive soft-shell technique

PURPOSE

To compare the efficacy of the dispersive-viscoadaptive soft-shell technique using Viscoat and Healon 5 to the dispersive-cohesive soft-shell technique in reducing corneal endothelial cell damage during cataract surgery.

METHODS

In this prospective randomized study, 207 eyes of 171 cataract patients underwent phacoemulsification using the dispersive-viscoadaptive soft-shell technique (V-group, 102 eyes) with Viscoat and Healon5 or the dispersive-cohesive soft-shell technique (C-group, 105 eyes) with Viscoat and a cohesive agent (Opegan-Hi). Each group was divided into two subgroups depending on the amount of ultrasound (%Min) used during phacoemulsification. Corneal endothelial cell density was examined preoperatively and 3 months postoperatively. The endothelial cell loss was compared between the two groups, and also between the subgroups.

RESULTS

The mean endothelial cell loss 3 months after surgery was 8.4 +/- 5.6% standard deviation (SD) in the V-group and 8.2 +/- 6.2% in the C-group (P = 0.787). In the subgroups with ultrasound of 10 %Min or less, the mean endothelial cell loss 3 months after surgery was 6.6 +/- 4.6% in the V-group and 5.5 +/- 5.0% in the C-group (P = 0.104). In the subgroups with ultrasound of over 10 %Min, this value was 10.6 +/- 6.3% in the V-group and 11.9 +/- 5.7% in the C-group (P = 0.413). The correlation coefficient of the endothelial cell loss rate and %Min was 0.245 (P = 0.0129) in the V-group and 0.501 (P < 0.0001) in the C-group.

CONCLUSION

The dispersive-viscoadaptive soft-shell technique is as effective as the dispersive-cohesive soft-shell technique in protecting corneal endothelial cells during phacoemulsification regardless of the amount of ultrasound energy used.