Short-term changes in the morphology of posterior capsule opacification

Glutaredoxin 1 protects lens epithelial cells from epithelial-mesenchymal transition by preventing casein kinase 1α S-glutathionylation during posterior capsular opacification

Oxidative stress drives protein S-glutathionylation, which regulates the structure and function of target proteins and is implicated in the pathogenesis of many diseases. Glutaredoxin 1 (Grx1), a cytoplasmic deglutathionylating enzyme, maintains a reducing environment within the cell under various conditions by reversing S-glutathionylation. Grx1 performs a wide range of antioxidant activities in the lens and prevents protein-thiol mixed disulfide accumulation, reducing protein-protein aggregation, insolubilization, and apoptosis of lens epithelial cells. Oxidative stress is related to epithelial-mesenchymal transition (EMT) during posterior capsular opacification (PCO). However, whether Grx1-regulated protein S-glutathionylation plays an essential role in PCO remains unclear. In this study, we revealed that Grx1 expression was decreased in mice following cataract surgery. Furthermore, the absence of Grx1 elevated oxidative stress and protein S-glutathionylation and aggravated EMT in both in vitro and in vivo models. Concurrently, these results could be reversed by Grx1 overexpression. Notably, liquid chromatography-tandem mass spectrometry results showed that casein kinase 1α (CK1α) was susceptible to S-glutathionylation under oxidative stress, and CK1α S-glutathionylation (CK1α-SSG) was mediated at Cys249. The absence of Grx1 upregulated CK1α-SSG, subsequently decreasing the CK1α-induced phosphorylation of β-catenin at Ser45. The consequential downregulation of degradative β-catenin and upregulation of its nuclear translocation activated the Wnt/β-catenin signaling pathway and aggravated EMT. In conclusion, the downregulated expression of Grx1 in mice following cataract surgery aggravated EMT by upregulating the extent of CK1α-SSG. To the best of our knowledge, our study is the first to report how S-glutathionylation regulates CK1α activity under oxidative stress.

Moderate oxidative stress promotes epithelial-mesenchymal transition in the lens epithelial cells via the TGF-β/Smad and Wnt/β-catenin pathways

The epithelial-mesenchymal transition (EMT) plays a significant role in fibrosis and migration of lens epithelial cells (LECs), and eventually induces posterior capsule opacification (PCO). In the past, it was generally believed that the TGF-β/Smad pathway regulates lens EMT. A recent study found that attenuated glutathione level promotes LECs EMT via the Wnt/β-catenin pathway, which suggests a more complex pathogenesis of PCO. To test the hypothesis, we used the mouse cataract surgery PCO model and tested both canonical Wnt/β-catenin and TGF-β/Smad signaling pathways. The results showed that both TGF-β/Smad and Wnt/β-catenin pathways were activated during the lens capsule fibrosis. Compared with the freshly isolated posterior capsule, the expression level of phosphorylated Smad2 was highest at day3 and then slightly decreased, but the expression level of Wnt10a gradually increased from day0 to day7. It shows that these two pathways are involved in the lens epithelium's fibrotic process and may play different roles in different periods. Subsequently, we established oxidative stress-induced EMT model in primary porcine lens epithelial cells and found that both the TGF-β/Smad and Wnt/β-catenin pathways were activated. Further study suggests that block Wnt/β-catenin pathway using XAV939 alone or block TGF-β/Smad pathway using LY2109761 could partially block pLECs fibrosis, but blocking Wnt/β-catenin and TGF-β/Smad pathway using combined XAV939 and LY2109761 could completely block pLECs fibrosis. In conclusion, this study demonstrates that both TGF-β/Smad and canonical Wnt/β-catenin pathways play a significant role in regulating epithelial-mesenchymal transformation of lens epithelial cells but might be in a different stage.

Capsular fibrosis: a review of prevention methods and management

Opacification of the posterior capsule caused by residual lens epithelial cells (LEC) is still the most frequent long-term complication of cataract surgery. Beside the opacification of the visual axis with posterior capsule opacification (PCO), resulting in a decrease in visual function, fibrotic changes may also have a mechanical effect on intraocular lens (IOL) position such as axial shift, decentration, tilt and capsule striae. In this article, two types of capsular fibrosis are explored, on the one hand the anterior capsule fibrosis and on the other hand PCO. Results from clinical trials concerning their causes, natural course, incidence, influencing factors and possible methods of prophylaxis are presented.

Reduced Glutathione Level Promotes Epithelial-Mesenchymal Transition in Lens Epithelial Cells via a Wnt/β-Catenin-Mediated Pathway: Relevance for Cataract Therapy

The epithelial-mesenchymal transition (EMT) process plays a pivotal role in the pathogenesis of posterior capsular opacification because of remnant lens epithelial cell proliferation, migration, and transformation after cataract surgery. The latter, we hypothesize, may result in posterior capsule wrinkling and opacification because of a profound change in the lens growth environment via a 1000-fold reduction of extracellular glutathione (GSH) levels. To test this hypothesis, we investigated the EMT process in cell culture and GSH biosynthesis deficiency mouse models. Our data indicate a dramatic increase of pro-EMT markers, such as type I collagen, α-smooth muscle actin, vimentin, and fibronectin, under conditions of lens GSH depletion. Further study suggests that decreased GSH triggers the Wnt/β-catenin signal transduction pathway, independent of transforming growth factor-β. Equally important, the antioxidants N-acetyl cysteine and GSH ethyl ester could significantly attenuate the EMT signaling stimulated by decreased GSH levels. These findings were further confirmed by mock cataract surgery in both gamma glutamyl-cysteine ligase, catalytic subunit, and gamma glutamyl-cysteine ligase, modifier subunit, knockout mouse models. Remarkably, increased EMT marker expression, β-catenin activation, and translocation into the nucleus were found in both knockout mice compared with the wild type, and such increased expression could be significantly attenuated by N-acetyl cysteine or GSH ethyl ester treatment. This study, for the first time we believe, links oxidative stress to lens fibrosis and posterior capsular opacification formation via EMT-mediated mechanisms.

Long-term follow-up of posterior capsule opacification after AquaLase and NeoSoniX phacoemulsification

AIM

To compare the degree of posterior capsule opacification (PCO) after AquaLase and NeoSoniX phacoemulsification methods during an 8-year follow-up period using two types of software.

DESIGN

Prospective, randomized clinical trial.

METHODS

AquaLase was used in the right eye and NeoSoniX in the left eye of each patient with bilateral cataract.

RESULTS

Fifty patients were analyzed 1 year, 46 patients 3 years, and 37 patients 8 years after cataract surgery. Mean EPCO 2000 values were for the AquaLase group 0.324 ± 0.305 and for the NeoSoniX group 0.298 ± 0.341 (P = 0.53) 1 year after surgery, for the AquaLase group 0.582 ± 0.506 and for the NeoSoniX group 0.594 ± 0.515 (P = 0.87) 3 years after surgery, and for the AquaLase group 0.648 ± 0.567 and for the NeoSoniX group 0.673 ± 0.542 (P = 0.30) 8 years after surgery. The OSCA results were for the AquaLase group 0.7097 ± 0.3778 and for the NeoSoniX group 0.8584 ± 0.4323 (P = 0.046) 1 year after surgery, for the AquaLase group 0.9667 ± 0.736 and for the NeoSoniX group 0.9540 ± 0.5250 (P = 0.91) 3 years after surgery, and for the AquaLase group 1,035 ± 0,952 and for the NeoSoniX group 1,103 ± 0,741 (P = 0.44) 8 years after surgery.

CONCLUSION

There was minimal PCO difference between these 2 approaches, AquaLase and NeoSoniX. Neither AquaLase nor NeoSoniX technique was able to prevent a natural progression of PCO.

A new technique for Nd:YAG laser posterior capsulotomy

AIM

To investigate the effects of a new opening pattern in neodymium:yttrium-aluminum-garnet (Nd:YAG) laser posterior capsulotomy on visual function.

METHODS

This technique was conducted along a circular pattern. The energy ranged between 0.8 and 1.2 mJ/pulse was consumed and mean total energy levels were 74±21 mJ (mean±standard deviation: SD, from 40 to 167) and laser shots aimed at 150 µm away behind a datum point and went along an imaginary line which extends 0.5 mm inside from optic margin and into the circular en bloc pattern. Vitreous stands were attached with fragment and then they were cut off by the laser after circular application. The circular fragment was completely separated from vitreous, and then this fragment was quickly sunk in intravitreal space.

RESULTS

The follow-up period ranges from at least a week to 40mo, making 15.8mo on average. The procedural outcome showed 96% (74 eyes out of the 77 eyes) enhancement in patients' visual acuity. Cystoid macular edema or retinal detachment was not observed in any of the patients during follow-up periods.

CONCLUSION

This new technique is expected to improve the weaknesses that the conventional procedures have by adding the process to cut off vitreous stands attached with the fragment by the laser to the circular application.

Posterior capsule opacification with 3 intraocular lenses: 12-year prospective study

PURPOSE

To compare posterior capsule opacification (PCO) with 3 intraocular lenses (IOLs) 12 years postoperatively.

SETTING

St. Erik Eye Hospital, Stockholm, Sweden.

DESIGN

Randomized clinical trial.

METHODS

Patients having unilateral standard phacoemulsification were randomized to implantation of a round-edged heparin-surface-modified (HSM) poly(methyl methacrylate) (PMMA) IOL, a round-edged silicone IOL, or a sharp-edged hydrophobic acrylic IOL. The neodymium:YAG (Nd:YAG) capsulotomy rates and timing from surgery were recorded. Survival analysis was used to compare Nd:YAG rates. Retroillumination images were taken to evaluate PCO.

RESULTS

After 12 years, there was no significant difference in the fraction or severity of PCO between the silicone IOL and acrylic IOL. The HSM PMMA IOL had a significantly higher PCO fraction than the silicone IOL (P<.05), but not more than the acrylic IOL. There was no difference in PCO severity between the HSM PMMA IOL and the other 2 IOLs. The silicone IOL had higher median capsulotomy-free survival (>150 months) than the acrylic IOL (108 months) and the HSM PMMA IOL (53 months). Overall survival without Nd:YAG capsulotomy did not differ between the acrylic and silicone IOLs or between the silicone and HSM PMMA IOLs; however, overall survival was significantly better with the acrylic IOL than with the HSM PMMA IOL (P<.001).

CONCLUSIONS

After 12 years, there was no difference in PCO or overall survival without capsulotomy between the acrylic IOL and the silicone IOL. The HSM PMMA IOL had a significantly higher PCO fraction than the silicone IOL and lower overall survival than the acrylic IOL.

Three-year follow-up of posterior capsule opacification after AquaLase and NeoSoniX phacoemulsification

PURPOSE

To prospectively compare the degree of posterior capsule opacification (PCO) after AquaLase and NeoSoniX phacoemulsification methods during the 3-year follow-up period.

DESIGN

Prospective, randomized clinical trial.

METHODS

Setting at the Department of Ophthalmology, University Hospital in Hradec Králové. Patients with bilateral cataract were included. AquaLase was used in the right eye and NeoSoniX in the left eye of each patient. The AcrySof SA60AT intraocular lens (Alcon Laboratories, Fort Worth, Texas, USA) was implanted in all eyes. The Evaluation of Posterior Capsule Opacification (EPCO) 2000 software (Developed by Tetz MR and associates, Berlin, Germany) and the Open-Access Systematic Capsule Assessment (OSCA) system (Devised by Aslam TM, Edinburgh, United Kingdom) were used for PCO assessment 1, 2, and 3 years after cataract surgery.

RESULTS

Fifty patients were analyzed 1 year, 47 patients 2 years, and 46 patients 3 years after cataract surgery. Mean EPCO 2000 values were for the AquaLase group 0.324 +/- 0.305 and for the NeoSoniX group 0.298 +/- 0.341 (P = .53) 1 year after surgery, for the AquaLase group 0.429 +/- 0.322 and for the NeoSoniX group 0.478 +/- 0.337 (P = .30) 2 years after surgery, and for the AquaLase group 0.582 +/- 0.506 and for the NeoSoniX group 0.594 +/- 0.515 (P = .87) 3 years after surgery. The OSCA results were for the AquaLase group 0.7097 +/- 0.3778 and for the NeoSoniX group 0.8584 +/- 0.4323 (P = .046) 1 year after surgery, for the AquaLase group 0.7515 +/- 0.4555 and for the NeoSoniX group 0.8103 +/- 0.4498 (P = .44) 2 years after surgery, and for the AquaLase group 0.9667 +/- 0.736 and for the NeoSoniX group 0.9540 +/- 0.5250 (P = .91) 3 years after surgery. Neodymium-yttrium-aluminun-garnet capsulotomy rate for AquaLase vs NeoSoniX was 0:1 eyes 1 year, 1:3 eyes 2 years, and 1:4 eyes 3 years after surgery. No significant difference between those 2 groups was established, except the OSCA outcomes 1 year postoperatively.

CONCLUSION

There was only minimal PCO difference between these 2 approaches, AquaLase and NeoSoniX. Neither AquaLase nor NeoSoniX technique was able to prevent a natural progression of PCO.

Three-hundred-sixty degree barrier effect of a square-edged and an enhanced-edge intraocular lens on centripetal lens epithelial cell migration Two-year results

PURPOSE

To study the 360-degree barrier effect of an intraocular lens (IOL) with a square edge at the optic and an enhanced square edge at the optic-haptic junctions (Rayner 570C C-flex) on centripetal migration of lens epithelial cells (LECs) over a 2-year period.

SETTING

Department of Ophthalmology, Scarborough Hospital, Scarborough, United Kingdom.

METHODS

In a prospective study of 40 consecutive eyes, a C-flex IOL was implanted in the bag after phacoemulsification surgery. Eyes with intraoperative complications, requiring additional procedures, without 360-degree overlap of the optic, or with capsule block syndrome were excluded. Follow-up was at 6, 10, 18, and 24 months. At each visit, high-magnification retroillumination digital photographs were taken using a slitlamp-attached digital camera. The barrier effect to LEC migration across the optic edge and the enhanced square edge at the optic-haptic junction was graded as complete (no epithelial pearls or sheet), partial (few epithelial pearls without sheet), and minimal/none (epithelial sheet behind the IOL optic).

RESULTS

Twenty-four patients came to the final follow-up at 24 months. Fifteen of these eyes (63%) had a complete barrier effect throughout the 360 degrees of the IOL. Three eyes (13%) had a partial barrier effect throughout the 360 degrees of the IOL. Three eyes had a complete optic barrier effect but a partial optic-haptic junction barrier effect. Three eyes had a partial optic barrier effect but a complete optic-haptic junction barrier effect. No eye had epithelial sheets extending behind the optic at any location.

CONCLUSIONS

This study showed the barrier effect of the edge design of the C-flex IOL and the efficacy of the enhanced edge in preventing LEC migration at the optic-haptic junction. The enhanced edge was as effective as a sharp square edge in restricting the LEC migration.

Effect of topical prednisolone and diclofenac on the short-term change in morphology of posterior capsular opacification

PURPOSE

To observe and document the effect of steroidal and nonsteroidal antiinflammatory treatment on the formation of Elschnig pearls.

DESIGN

A prospective, randomized, double blinded, placebo controlled, two-way-cross-over study.

METHODS

Thirty-nine eyes of 32 patients with pronounced, regeneratory posterior capsule opacification (PCO) were included. The patients were treated topically with prednisolone and diclofenac (verum) or with lubricating eye drops (placebo) four times daily for one week. After a wash-out period of two weeks the patients received the contrary treatment also four times daily for one week. Digital retroillumination images were taken at day one, three, five, eight, and 15 of each medication period. The changes in the size of 4,675 Elschnig pearls were analyzed.

RESULTS

The mean cumulative area of all marked pearls/eye and follow-up was 1.2 mm(2) (range: 0.1 mm(2) to 3.2 mm(2)). The mean pearl size was 12,809 microm(2) (range: 60 microm(2) to 1.08 x 10(6) microm(2)). Between the follow-up examinations, 1,274 pearls disappeared (mean: 33 pearls/eye, range: five to 69 pearls; 27%) and 777 newly formed pearls appeared (mean: 20 pearls/eye, range: three to 53 pearls; 20%). There was no statistically significant difference in pearl size change and in number of disappeared and newly appeared pearls between the verum and the placebo treatments.

CONCLUSIONS

Topical prednisolone and diclofenac do not influence the short-term change of Elschnig pearls. Elschnig pearls disappear and appear within days. The degree of progression and regression varies greatly among eyes.

Daily changes in the morphology of Elschnig pearls

PURPOSE

To observe and document the daily changes in the morphology of Elschnig pearls.

DESIGN

A prospective cohort study.

METHODS

Twenty-nine pseudophakic eyes with pronounced, regeneratory posterior capsule opacification (PCO) were included in this prospective study. Retroillumination images were taken at days 0, 1, 2, and 14. A square grid was laid over the images. Increase, decrease, appearance, and disappearance of pearls between the follow-up images were quantified.

RESULTS

A total of 1371 areas (mean: 53/eye) of 26 eyes were analyzed between days 0 and 1 and 1 and 2, and 896 areas (50/eye) of 18 eyes between days 0 and 14. Between days 0 and 1, days 1 and 2, and days 0 and 14, we observed "no change" in pearl size in 72%, 77%, and 32%, a "minor increase" in 16%, 14%, and 10%, a "major increase" in 4%, 3%, and 42%, a "minor decrease" in 14%, 11%, and 11%, and a "major decrease" in 4%, 3%, and 37%, respectively. Appearance of newly formed pearls was found in 1%, 1%, and 9% and disappearance of pearls in 1%, 1%, and 5%, respectively.

CONCLUSIONS

Significant changes in the morphology of Elschnig pearls were observed within time intervals of only 24 hours. Appearance and disappearance of pearls, as well as progression and regression of pearls within these short intervals illustrate the dynamic behavior of regeneratory PCO. These findings may contribute to a better understanding of PCO and have implications on pharmaceutical interventions for PCO.

Posterior capsule opacification

PURPOSE OF REVIEW

This paper assesses the factors that contribute to the formation of an effective capsular bend as a deterrent to posterior capsule opacification. Its goal is to assist the practicing ophthalmologist in separating current understanding of this process from various working models previously proposed.

RECENT FINDINGS

While a square-edge design appreciably improves resistance to posterior capsule opacification, significant factors remain under the control of the surgeon. These factors combine to form the physical and psychological barrier of a capsular bend. Innovative digital imaging has shown lens epithelial cell migration, allowing for a more rapid assessment of posterior capsule opacification resistance. A three-piece intraocular lens allows for full 360 degree capsular bend formation surrounding the optic edge; some single-piece designs may inhibit capsular bend formation. Decreasing, but not eliminating, the surviving lens epithelial cell population may diminish capsular bend strength, which may decrease resistance to posterior capsule opacification in the face of a regenerating cortex. All demographic features of clear/refractive lens exchange suggest higher rates of posterior capsule opacification than with standard cataract surgery.

SUMMARY

The quality of capsular bend formation will determine how resistant an intraocular lens will be to posterior capsule opacification as a consequence of regenerating cortex. As refractive lens exchange and new accommodating intraocular lens designs become more popular, the problems of regenerating cortex will increase in magnitude.