Bullous keratopathy as a complication of trabeculectomy with mitomycin C

Clinical Factors Impacting Outcomes From Failed Trabeculectomy Leading to Glaucoma Drainage Device Implantation and Subsequent Penetrating Keratoplasty

PRCIS

We evaluated the factors that impacted time from glaucoma drainage implant (GDI) surgery to penetrating keratoplasty (PK) in eyes with previously clear corneas (ie, GDI-first sequence), and that specifically underwent a trabeculectomy before GDI surgery for intraocular pressure (IOP) control.

PURPOSE

To describe through an event-triggered data collection method the clinical course and the long-term outcomes of 2 procedures that are commonly performed sequentially in complex clinical situations: GDI surgery and PK. The study investigates the clinical factors associated with the progression to PK and determines the GDI success rate and graft survival.

METHODS

A single, tertiary-care center retrospective interventional cases series including patients with a sequential history of trabeculectomy, GDI surgery, and PK from 1999 to 2009. Outcome measures included IOP, visual acuity, graft failure, GDI failure, and time from GDI to PK.

RESULTS

Of the eyes, 56% had primary open angle glaucoma. The time from the last trabeculectomy to GDI was 66.5 ± 66.7 months. Of the eyes, 84% received a Baerveldt GDI. Time from GDI to PK was 36.4 ± 28.4 months. IOP at the time of PK was between 5 mm Hg and 21 mm Hg in 90% of eyes. At the last follow-up, 48% of grafts were clear. At 5 years post-PK, 33% of corneal grafts remained clear, whereas 81% of tubes remained functional.

CONCLUSIONS

Nearly half of the corneal grafts are clear at the last long-term follow-up. Graft failure occurs at a higher rate than tube failure suggesting that IOP control is only one and possibly not the most important factor in graft survival in eyes with prior glaucoma surgery.

Effects of topical docosahexaenoic acid on postoperative fibrosis in an animal model of glaucoma filtration surgery

PURPOSE

The aim of this study was to evaluate docosahexaenoic acid (DHA) as a potential antifibrotic agent after glaucoma filtration surgery (GFS) in rats.

METHODS

A total of 36 10-week-old Brown Norway rats underwent GFS. Animals were equally divided into three groups: a control group, a DHA group and a mitomycin C (MMC) group. Intraocular pressure (IOP) was measured using a dynamic rebound tonometer, and a photograph of the surgical site was taken on days 1, 3, 7, 10, 14 and 17. The incorporation of DHA into fibroblasts was evaluated by gas chromatography. The expression of alfa-smooth muscle actin (α-SMA) and Smad proteins was assessed by Western blotting.

RESULTS

IOP decreased after surgery in animals from the three groups on day 1 after surgery. Over time, IOP remained lower in the DHA and MMC groups than in the control group (median [interquartile range] 8.0 [7.0-8.0] and 8.0 [7.3-8.0] mmHg vs. 9.0 [8.0-9.0] mmHg, respectively; p < 0.001). Bleb area in the DHA and MMC groups remained larger than that of the control group from day 7 to day 14 (3.9 [2.9-5.2] and 3.5 [2.3-4.4] mm² vs. 2.3 [2.0-2.8] mm² , respectively; p = 0.0021). We did not observe any change in DHA concentrations in the fibroblasts of the DHA group compared with the other groups.

CONCLUSION

The impact of DHA on IOP and bleb area was similar to that of MMC. The mechanisms of action of DHA in rat eye fibroblasts deserve further investigation.

Changes in corneal endothelial cell density after initial Ex-PRESS drainage device implantation and its relating factors over 3 years

BACKGROUND/OBJECTIVES

To investigate changes in corneal endothelial cell density (CECD) after initial Ex-PRESS surgery in Japanese patients with open-angle glaucoma (OAG) followed-up for 36 months.

SUBJECTS/METHODS

Corneal specular microscopy was used to examine preoperative and postoperative (3, 6, 12, 24 and 36 months) CECD and CECD changes were analysed. Kaplan-Meier survival curve was used to examine CECD maintained at 95% level, and Cox proportional hazards model was used to detect the risk factors for CECD loss. Intraocular pressure (IOP) changes during the course were also examined.

RESULTS

A total of 79 eyes of 79 patients (standalone surgery, 24 cases; combined cataract surgery, 55 cases) were investigated. Preoperative CECD (mean ± SD) was 2521 ± 305 cells/mm² and 2429 ± 366 (P = 0.003, adjusted for Bonferroni correction), 2462 ± 332 (P = 0.002), 2457 ± 317 (P < 0.001), 2433 ± 333 (P < 0.001), and 2387 ± 352 (P < 0.001) at 3, 6, 12, 24 and 36 months, respectively. The decrease rate was calculated as 1.8%/year. Further, 95% maintenance CECD at 36 months was 50.0% (95% confidence interval, 37.1-63.0%). Both univariate and multivariate Cox proportional hazard models showed that a low preoperative CECD was a significant risk factor for CECD loss. Baseline IOP of 19.3 ± 5.8 mmHg decreased at all measurement points (P < 0.001) after surgery.

CONCLUSION

CECD after initial Ex-PRESS surgery in 36 months might not be clinically problematic. However, longer-term follow-up is necessary, and regular CECD measurement should be performed, especially in patients with low CECD.

A Prospective Evaluation of the Effect of Mitomycin-C on Corneal Endothelium after Photorefractive Keratectomy for Myopia Correction

PURPOSE:

The aim of the study was to assess the effect of mitomycin-C (MMC) 0.02% application on corneal endothelium in patients undergoing photorefractive keratectomy (PRK) for the correction of myopia and compound myopic astigmatism.

METHODS:

A prospective observational study including patients with myopia who underwent PRK plus intraoperative application of MMC 0.02%. All patients underwent noncontact specular microscopy preoperatively and 6 months postoperatively. The following parameters were analyzed: mean cell area (MCA), central corneal endothelial cell density (ECD), and coefficient of variation (CV) in cell size.

RESULTS:

One hundred and thirty-nine eyes of 73 patients with a mean age of 24.95 ± 3.23 years were included in the study. Mean baseline preoperative pachymetry was 519.54 ± 28.62 μm. The mean preoperative spherical equivalent was −4.6 ± 2.3D (range from −1D to −10D) which decreased to mean postoperative spherical equivalent of −0.125 ± 0.32D. Mean baseline ECD was 2829.3 ± 188.8 cells/mm², MCA was 354.6 ± 24.9 μm²/cell, CV was 0.35 ± 0.06, and hexagonality was 50.1 ± 6.64. The mean ECD decreased by 43 ± 1.6 cells/mm² which was not statistically significant (P = 0.07). The MCA increased by 5 ± 1.3 μm²/cell, but this was not statistically significant (P = 0.07). However, both the CV and percentage of hexagonal cells showed statistically significant differences in the median values as compared to preoperatively (P < 0.001).

CONCLUSION:

In our study, MMC had no significant effect on corneal endothelial cell counts or MCA. While there were statistically reduced CV and percentage of hexagonal cells, these did not appear to be clinically significant. MMC is safe to use routinely to prevent haze formation in PRK.

Descemet Membrane Endothelial Keratoplasty in Eyes With Chronic Ocular Hypotony Following Glaucoma Surgery

PURPOSE

To assess the outcomes of Descemet membrane endothelial keratoplasty (DMEK) in patients with ocular hypotony after glaucoma surgery.

DESIGN

retrospective case series.

METHODS

Setting: Multicenter retrospective case series.

PATIENTS/INTERVENTION

Hypotonic eyes with prior glaucoma surgery that underwent DMEK between January 2013 and July 2019 in Israel (2 centers) and Canada (1 center).

MAIN OUTCOME MEASURES

Pre/postoperative corrected distance visual acuity, complications, 3- to 6-month endothelial cell loss, and intraocular pressure (IOP).

RESULTS

The study included 11 DMEK procedures performed in 10 eyes of 4 males and 6 females aged 65-84 years. Indications for DMEK included 7 cases of pseudophakic bullous keratopathy, 2 cases of failed DMEK, and 1 case of failed Descemet stripping automated endothelial keratoplasty. All patients had at least 1 previous trabeculectomy operation. One patient had 2 trabeculectomy procedures and 1 tube placement procedure. Two patients had 1 previous trabeculectomy and 1 tube placement procedure. The corrected distance visual acuity improved significantly from 1.52 ± 0.68 logarithm of minimal angle of resolution preoperatively to 0.49 ± 0.32 logarithm of minimal angle of resolution 3 months postoperatively (P < .001). Rebubbling occurred in 3 of 11 procedures (27%). Endothelial cell loss 6-12 months postoperatively was 60% ± 16% (range, 41%-89%). At the last follow-up visit, 6 of 11 (54%) of the grafts were clear. The remaining 5 grafts failed at 1-4 years postoperatively. The preoperative IOP was 5.1 ± 1.6 mm Hg (range, 1-7 mm Hg). In all but one patient, the postoperative IOP did not increase to more than 13 mm Hg. In 2 cases, the IOP decreased from 5 and 7 mm Hg preoperatively to 1 mm Hg 1 year postoperatively.

CONCLUSION

DMEK is a valid procedure for the treatment of corneal edema in hypotonic eyes after glaucoma procedures. These eyes benefit from improvement in vision after DMEK.

Retrospective analysis of the comparison between carbon dioxide laser-assisted deep sclerectomy combined with phacoemulsification and conventional trabeculectomy with phacoemulsification

Purpose:

To compare outcomes of laser assisted deep sclerectomy (LADS) and conventional trabeculectomy both combined with phacoemulsification.

Methods:

We divided 36 eyes into 2 groups, one group with LADS and the other Trabeculectomy. Patients were measured post operatively at 1, 3, 6, 9 months, 1, 2, 3 years for intraocular pressure (IOP), best corrected visual acuity (BCVA) and number of medications.

Results:

In the trabeculectomy group, after 3 year follow up, IOP was 14.67 ± 3.14, 15.27 ± 4.28 and 17.00 ± 7.79, BCVA improved to 0.17 ± 0.18, 0.24 ± 0.20 and 0.24 ± 0.27 and number of medications reduced to 0.6 ± 0.6, 1.1 ± 1.2, and 1.5 ± 1.5. Complete success rate after 3 years was 100%, 80.0% & 80.0% and Qualified success rate was 100%, 88.9% & 88.9%. In the LADS group, after 3 years follow up, IOP was 14.11 ± 3.91, 16.07 ± 5.51, 15.80 ± 6.07, BCVA improved to 0.13 ± 0.11, 0.10 ± 0.15, 0.11 ± 0.13 and medications reduced to 1 ± 1.1, 1.5 ± 1.0 and 1.8 ± 1.0. Complete success after 3 years was 85.7%, 57.1% & 57.1% whereas qualified success was 92.3%, 84.6% & 84.6%.

Conclusion:

Main limitations of our study were small sample size and lack of prospective comparison. However we were able to perfom the surgery comfortably due to the relatively shorter learning curve compared to conventional NPDS.

EX-PRESS Glaucoma Filtration Device: Management of Complications

The EX-PRESS glaucoma filtration device appears to be an effective addition to our options to treat refractory glaucoma. The possibility to create a sclerostomy without tissue excision provides a safe and reliable outflow pathway for aqueous that is standard in size, reducing much of the variability associated with a surgical procedure. Prospective randomized studies comparing EX-PRESS implantation with trabeculectomy show encouraging results. However, complications usually encountered in filtration surgery have been reported, and EX-PRESS implantation can also lead to specific device-related complications. This article reviews the most common complications associated with this procedure.

CO2 laser-assisted sclerectomy surgery compared with trabeculectomy in primary open-angle glaucoma and exfoliative glaucoma. A 1-year follow-up

PURPOSE

To report on the efficacy and safety of CO₂ laser-assisted sclerectomy surgery (CLASS) compared with trabeculectomy in primary open-angle glaucoma and exfoliative glaucoma.

METHODS

One hundred and thirty-one patients underwent CLASS (66 patients) or trabeculectomy (65 patients) and were followed up for 12 months. 'Complete success' was defined as intraocular pressure (IOP) between 10 and 18 mmHg and reduced by at least 30% from the baseline without medications, while 'qualified success' was compliant with the above criteria with or without the medications.

RESULTS

Comparing CLASS with trabeculectomy at 1 year, the mean IOP reduction rate was 32.6 ± 10.8% versus 40.6 ± 15.9% (p < 0.001) and the average use of medications was 1.4 ± 1.4 versus 0.7 ± 1.1 (p < 0.05). At 12 months, the complete success rate was 35% for CLASS versus 60% for trabeculectomy (p < 0.01), while the qualified success rate was 74% versus 75%, respectively, with no significant difference in qualified success rate between the groups at any time-point (p > 0.05). Compared with CLASS, patients after trabeculectomy developed a higher rate of early complications (9.1% versus 29.2%, p = 0.004), higher endothelial cell density (ECD) loss (1.4 ± 1.4% versus 6.5 ± 4.8%, p < 0.001), higher astigmatism (0.0 ± 0.1 versus 0.1 ± 0.2, p < 0.001) and significant visual acuity deterioration (0.1 ± 0.1; range 0-2 lines versus 0.4 ± 0.6; range 0-3 lines, p = 0.016).

CONCLUSION

Although CLASS shows a less potent hypotensive effect, it is similar to trabeculectomy in the qualified success rate and offers the reduction in medications up to 12 months. With a more attractive complications profile, CLASS may be an alternative to trabeculectomy, especially at the earlier glaucoma stage and in patients with a low ECD.

Progressive idiopathic unilateral corneal endothelial failure of unknown aetiology in phakic eyes

AIM

To describe a cohort of patients with irreversible unilateral bullous keratopathy (BK) of undetermined aetiology.

METHOD

Retrospective, single-centre case series in a tertiary corneal referral centre.

RESULTS

Eleven consecutive patients (nine females; mean age 71.7 years) presented from 1999 to 2009 with acute onset unilateral visual loss. At presentation, the best-corrected visual acuity of the affected eyes was 6/9 or worse with mean central corneal thickness (CCT) of 684 (SD 66) μm. Specular microscopy was not possible in the affected eyes. There was no other ocular pathology in the affected eye. The fellow eye remained normal throughout the study (mean endothelial cell density (ECD) of 1980 (SD 736) cells/mm² and CCT of 536 (SD 34) μm). Topical steroid, antiviral treatments (both topical and systemic) or a combination of both did not yield any improvement. After a mean follow-up of 82.2 months, eight eyes had penetrating keratoplasty (PK). One required two regrafts. Histology showed typical BK features, with endothelial cell (EC) loss and thickened Descemet's membrane (DM). Transmission electron microscopy revealed DM abnormalities in a non-consistent pattern, featuring variable collagen deposition posterior to the non-banded zone. The ECs were degenerated, reduced or absent. Neither viruses nor pseudoexfoliation material was identified.

CONCLUSION

While medical treatment is not beneficial, PK appears to offer good results. Non-guttate Fuchs' corneal endothelial dystrophy merits consideration but it would be unusual to see an exclusively unilateral presentation. DM thickening is reflective of a chronic EC loss but the cause of this loss remains elusive.

Current Perspectives on the Use of Anti-VEGF Drugs as Adjuvant Therapy in Glaucoma

The approval of one of the first anti-vascular endothelial growth factor (VEGF) agents for the treatment of neovascular age-related macular degeneration one decade ago marked the beginning of a new era in the management of several sight-threatening retinal diseases. Since then, emerging evidence has demonstrated the utility of these therapies for the treatment of other ocular conditions characterized by elevated VEGF levels. In this article we review current perspectives on the use of anti-VEGF drugs as adjuvant therapy in the management of neovascular glaucoma (NVG). The use of anti-VEGFs for modifying wound healing in glaucoma filtration surgery (GFS) is also reviewed. Selected studies investigating the use of anti-VEGF agents or antimetabolites in GFS or the management of NVG have demonstrated that these agents can improve surgical outcomes. However, anti-VEGF agents have yet to demonstrate specific advantages over the more established agents commonly used today. Further studies are needed to evaluate the duration of action, dosing intervals, and toxicity profile of these treatments.

Safety and Efficacy of Collagen Matrix Implantation in Infantile Glaucoma

Purpose

To evaluate the preliminary results of biodegradable collagen matrix implant (Ologen) designed to improve outcome in patients with infantile glaucoma undergoing combined trabeculotomy and trabeculectomy.

Methods

A biodegradable collagen matrix (OculusGen) was placed in the subconjunctival space, partially over the scleral flap and the sclera in 20 eyes of 11 patients with infantile glaucoma who underwent combined trabeculotomy and trabeculectomy. Patients were examined preoperatively and on the first postoperative day with multiple postoperative follow-up visits within 12 months after surgery. Examination included measurements of intraocular pressure (IOP), corneal diameter, and axial length, bleb evaluation, and funduscopy. Ultrasound biomicroscopy of bleb (bleb presence, wall reflectivity, and scleral route visibility) was done at 1, 3, and 6 months and the last follow-up visit. Any complication was recorded. Data analysis was performed using paired-samples t test.

Results

Mean patient age was 5.7 ± 5.69 months. Mean duration of follow-up was 10.05 ± 1.15 months. Mean preoperative IOP was 25.9 ± 3.08 mm Hg with 1.75 ± 0.55 IOP-lowering medications and mean final postoperative IOP was 17.7 ± 3.51 mm Hg with 0.55 ± 0.69 IOP-lowering medications. Overall success at last follow-up was 80%. None of the patients experienced systemic or ocular complication related to OculusGen. By the 6th month, complete Ologen degradation was evident in all cases.

Conclusions

The short-term preliminary results of this study indicate that the combined trabeculotomy and trabeculectomy with Ologen implantation could potentially provide a safe and effective procedure in the infantile age group but longer duration of follow-up in larger number of patients is needed.

Effect of Mitomycin-C Augmented Trabeculectomy on Corneal Endothelial Cells

Purpose:

To evaluate the effect of mitomycin-C (MMC) on corneal endothelial cell density (ECD) and morphology after trabeculectomy.

Methods:

In this prospective comparative case series, 31 eyes with glaucoma underwent trabeculectomy with (group I), or without (group II) MMC. Specular microscopy was performed pre-, and postoperatively at months 1 and 3. Outcome measures included central corneal endothelial cell count and coefficient of variation (CV) of cell size.

Results:

Overall, mean preoperative ECD was 2,135.8 ± 397.6 cells/mm²; corresponding values at postoperative months 1 and 3 were 2,019.6 ± 447.2 cells/mm², and 1,991.4 ± 425.5 cells/mm², respectively (P > 0.05). Cell loss from month 1 to 3 was 1.3 % (P > 0.05). Subgroup analysis showed significant differences in endothelial cell loss at month 1 (P = 0.048) and month 3 (P = 0.014) between the MMC and control groups with no significant difference between the two groups in terms of cell loss from months 1 to 3, postoperatively (P = 0.968). Overall, mean pre-and postoperative CVs at months 1 and 3 were 27.38 ± 4.55, 27.96 ± 4.26, and 28.35 ± 4.47, respectively, with no significant difference between the two groups (P > 0.05). There was no correlation between preoperative central endothelial cell density (CECD) and MMC related cell loss.

Conclusion:

MMC application in trabeculectomy seems to cause a small but significant corneal endothelial loss. Most of the damage occurs intraoperatively, or in the early postoperative period, however progressive endothelial cell loss is not a major concern.

Corneal decompensation following filtering surgery with the Ex-PRESS(®) mini glaucoma shunt device

PURPOSE

To report a case of corneal decompensation due to the Ex-PRESS(®) mini glaucoma shunt device (Ex-PRESS).

PATIENT AND METHODS

A 75-year-old man had pseudoexfoliation glaucoma in his right eye. He underwent filtration surgery with Ex-PRESS. His intraocular pressure was 7 mmHg after 9 months.

RESULTS

We observed partial decompensation of the corneal endothelium adjacent to the filtering bleb. Specular microscopy revealed a marked decrease in the endothelial cell density at the center of the cornea.

CONCLUSION

Anterior segment optical coherence tomography is very useful for evaluating corneal edema and the position of Ex-PRESS. It is important to follow up with an examination of the corneal endothelial cells.

Deep sclerectomy with bevacizumab and mitomycin C: a comparative study

PURPOSE

To assess the comparative efficacy and safety of primary deep sclerectomy (DS) augmented with subconjunctival Bevacizumab and intraoperative Mitomycin C (MMC).

METHODS

Retrospective, comparative case-control series of consecutive primary DS between January 2008 and December 2010. Seventy-five eyes of 73 patients were included, with 32 eyes in the MMC and 43 in the Bevacizumab group. MMC (0.2 mg/mL for 2 min) was applied subconjunctivally before scleral flap dissection. Bevacizumab (2.5 mg in 0.1 mL) was injected subconjunctivally at the end of surgery. Complete success was intraocular pressure (IOP) <19 mm Hg and a 20% decrease from baseline with no postoperative medications.

RESULTS

There were no significant baseline differences between the groups. Follow-up after DS was 33.3 ± 6.1 months for the Bevacizumab and 35.0 ± 10.2 months for the MMC group (P=0.34). Complete success rates were 90.7% [95% confidence interval (CI), 82.4%-99.8%] and 87.5% (95% CI, 76.8%-99.7%) at 1 year and 76.5% (95% CI, 64.8%-90.4%) and 74.4% (95% CI, 60.5%-91.4%) at 2 years after DS in the Bevacizumab and MMC groups, respectively (P=0.52). There was no statistical difference in mean IOPs between the groups at all specified time intervals up to 2 years (P=0.28). At last follow-up 2 (6.2%) of the MMC and 2 (4.7%) eyes of Bevacizumab group were on medications to control IOP. Eighteen eyes had complications, 9 (20.9%) in Bevacizumab and 9 (28.1%) in the MMC group (P=0.8).

CONCLUSION

Subconjunctival Bevacizumab with primary DS appears to be as efficacious as MMC augmentation with no additional side effects.

Comparison of the use of 5-fluorouracil and bevacizumab in primary trabeculectomy: results at 1 year

BACKGROUND

The present study compared the effects of adjuvant bevacizumab and 5-fluorouracil on the efficacy and safety of trabeculectomy.

DESIGN

A nonrandomized, prospective, interventional case study.

PARTICIPANTS

A total of 62 patients in two groups undergoing primary trabeculectomy.

METHODS

In Group 1 (21 primary open-angle glaucoma, nine pseudoexfoliative glaucoma), trabeculectomy was performed with an adjuvant 5% solution of 5-fluorouracil administered for 4 min, intraoperatively. In Group 2 (21 primary open-angle glaucoma, 11 pseudoexfoliative glaucoma), trabeculectomy was enhanced with 1.25 mg of bevacizumab applied subconjunctivally immediately before and after surgery and again 1 and 7 days after surgery.

MAIN OUTCOME MEASURES

Intraocular pressure, best corrected visual acuity, visual field index, bleb morphology, cornel endothelial cell count.

RESULTS

Mean intraocular pressure was 28.0 ± 8.0 mmHg before 5-fluorouracil-augmented trabeculectomy and 27.8 ± 9.5 mmHg before bevacizumab-augmented trabeculectomy. After 12 months, mean intraocular pressure was 13.6 ± 4.4 mmHg in the 5-fluorouracil group and 14.7 ± 4.7 mmHg in the bevacizumab group. A 30% reduction of initial intraocular pressure was attained in 86.7% of patients in the 5-fluorouracil group and 78.1% of patients in the bevacizumab group at the end of follow up. No significant differences were noted between the two studied groups with respect to corneal endothelial density, visual field indices and postoperative complications.

CONCLUSIONS

The 12-month intraocular pressure results showed no significant differences between the two groups of patients after bevacizumab or 5-fluorouracil to augment trabeculectomy. However, to obtain successful intraocular pressure control more patients in bevacizumab group needed medical therapy.

Effects of mitomycin C on corneal endothelial cell counts in pterygium surgery: role of application location

PURPOSE

To evaluate changes in corneal endothelial cell counts after pterygium surgery with application of mitomycin C (MMC) either on the perilimbal sclera or in the subconjunctival space.

DESIGN

Prospective, randomized interventional study.

METHODS

Fifty-six eyes of 56 patients with primary pterygium underwent excision followed by removal of subconjunctival fibrovascular tissue, 0.02% MMC application, and amniotic membrane transplantation. These were stratified randomly into 2 groups. In 1 group (n = 28), MMC was applied on the perilimbal bare sclera (sclera group), and in other group (n = 28), MMC was applied under conjunctiva, where subconjunctival fibrovascular tissue was removed (subconjunctiva group). Based on severity of pterygium fleshiness, MMC was used for 1, 3, or 5 minutes in 8, 13, and 7 eyes, respectively, in the sclera group and in 9, 13, and 6 eyes, respectively, in the subconjunctiva group. Central corneal endothelial cell counts were evaluated before and during 6 months of follow-up after surgery.

RESULTS

Mean preoperative endothelial cell count was 2810 ± 278 cells/mm(2) in the sclera group and 2857 ± 332 cells/mm(2) in the subconjunctiva group. Mean endothelial cell losses in sclera and subconjunctiva groups were 9.7% and 9.0% at 1 week, 6.5% and 6.5% at 1 month, 4.0% and 5.0% at 3 months, and 3.4% and 4.8% at 6 months, respectively, with no statistically significant difference between the 2 groups. Longer durations of MMC application were associated with significantly greater endothelial losses in both groups.

CONCLUSIONS

Regardless of application location, MMC use during pterygium surgery can cause a significant decrease in central endothelial cell count.

Impact on the corneal endothelium of mitomycin C during photorefractive keratectomy

PURPOSE

This brief review examines both basic science and clinical studies to evaluate the potential impact on the health of the corneal endothelium of mitomycin C (MMC) usage during photorefractive keratectomy (PRK).

METHODS

The mechanism of action and consequences of MMC are reviewed within the context of in vitro, animal, and clinical studies and a hypothesis of how this vital cell layer responds to MMC at both the cellular and clinical levels is formed.

RESULTS

Seven basic science studies were reviewed demonstrating significant MMC toxicity to corneal endothelial cells. Of the five clinical studies reviewed, three demonstrated no effect on corneal endothelial density, whereas two studies found significant cell loss after MMC usage.

CONCLUSIONS

Although all of the basic science studies reviewed highlight the toxicity of MMC on the corneal endothelium, current clinical studies are less conclusive. Given the corneal penetration of MMC and the fragile nature of the corneal endothelium, additional follow-up studies are needed to determine the long-term impact of MMC usage during PRK on the corneal endothelium.

Mitomycin C in corneal refractive surgery

Mitomycin C has played a deciding role in the current revival of excimer laser surface ablation techniques. We review the literature regarding mechanism of action of mitomycin C, histological effects on the cornea, and indications, dose, exposure time, and toxicity of mitomycin C in corneal refractive surgery. Mitomycin C is an alkylating agent with cytotoxic and antiproliferative effects that reduces the myofibroblast repopulation after laser surface ablation and, therefore, reduces the risk of postoperative corneal haze. It is used prophylactically to avoid haze after primary surface ablation and therapeutically to treat pre-existing haze. There is no definite evidence that establishes an exact diopter limit or ablation depth at which to apply prophylactic mitomycin C. It is usually applied at a concentration of 0.2mg/ml (0.02%) for 12 to 120 seconds over the ablated stroma, although some studies suggest that lower concentrations (0.01%, 0.002%) could also be effective in preventing haze when treating low to moderate myopia. This dose of mitomycin C has not been associated with any clinically relevant epithelial corneal toxicity. Its effect on the endothelium is more controversial: two studies report a decrease in endothelial cell density, but the majority of reports suggest that the endothelium is not altered. Regarding mitomycin C's effect on keratocyte population, although animal studies report keratocyte depletion after its use, longer follow-up suggested that the initial keratocyte depletion does not persist over time.

DNA cross-linking, double-strand breaks, and apoptosis in corneal endothelial cells after a single exposure to mitomycin C

PURPOSE

To investigate the cellular effects of mitomycin C (MMC) treatment on corneal endothelial (CE) cells at clinically relevant applications and dosages.

METHODS

Radial and posterior diffusion of MMC was determined by an Escherichia coli growth inhibition bioassay. A modified version of the comet assay (single cell gel electrophoresis) was used to detect DNA cross-linking. Immunostaining detected the nuclear phosphorylated histone variant H2AX (gamma-H2AX) indicating DNA double-strand breaks. Apoptosis in MMC-treated cells was detected with annexin V staining.

RESULTS

Topical application of 0.02% MMC to intact goat globes resulted in MMC in the CE at 0.37 microg/mL and produced a significant increase in CE DNA cross-linking with as little as 6 seconds of topical MMC treatment. DNA cross-linking was also demonstrated in cultured CE cells by using MMC exposures similar to those detected in CE of intact eyes. Such MMC treatment of CE produced elevated and persistent gamma-H2AX-positive cells indicative of DNA double-strand breaks. Similarly, there was an increase in the proportion of apoptotic CE cells, evidenced by positive annexin V staining.

CONCLUSIONS

The results demonstrate that exposure to MMC at times and concentrations commonly used in refractive surgery produces cross-linking of corneal endothelial DNA, persistent DNA damage, and endothelial death via apoptosis. Current practices of MMC application during refractive surgeries may increase the potential for long-term and permanent deleterious effects on the health of the corneal endothelium.

Transmission electron microscopy of the rabbit posterior capsule irrigated with thapsigargin and 5-fluorouracil in a sealed-capsule irrigation device

PURPOSE

To investigate, by transmission electron microscopy (TEM), the effect on the posterior capsule of a young rabbit eye of 5-fluorouracil (5-FU) or thapsigargin in a sealed-capsule irrigation device.

SETTING

St Erik's Eye Hospital, Stockholm, Sweden.

METHODS

Clear lens extraction was performed unilaterally in eight 4-week-old rabbits. A sealed-capsule irrigation device was irrigated for 2 min with 20 ml of one of the following: balanced salt solution (BSS; n=2), thapsigargin 300 muM (n=2), 5-FU 50 mg/ml (n=2), or 5-FU 25 mg/ml (n=2). The substances were washed out for 10 s with BSS. The eyes were left aphakic. Six weeks postoperatively, the animals were killed, and the posterior capsule was extracted and fixed for TEM. As a control, we also evaluated the capsules from the two fellow eyes in the BSS group that did not undergo surgery.

RESULTS

The ultrastructure of the posterior capsule in eyes irrigated with 5-FU or thapsigargin did not differ from that in the eyes irrigated with BSS or in the eyes that did not have surgery. The membranes had the same ultrastructure with thin collagen fibres on the anterior and posterior face of the posterior capsule and an amorphic matrix.

CONCLUSION

Thapsigargin or 5-FU used in a sealed-capsule irrigation device does not seem to harm the posterior capsule, which appeared similar to when the capsule is irrigated with BSS.

Focal corneal decompensation after filtering surgery with mitomycin C

PURPOSE

To report a case with focal corneal decompensation after filtering surgery with inadvertent inadequate irrigation of mitomycin C (MMC).

METHODS

Case report and review of literature.

RESULTS

A 25-year-old man first referred with the complaint of photophobia. His ocular examinations revealed diffuse keratic precipitates and many iris nodules in both eyes. The primary diagnosis was idiopathic bilateral granulomatous anterior uveitis. The intraocular pressure (IOP) gradually increased in the left eye and was not controlled with a prescription of topical antiglaucoma medications. As the disease progressed, the left eye underwent filtering surgery with MMC 0.02%. The postoperative period was uneventful, and the anterior chamber was deep after surgery. The IOP was controlled without medications; however; the inferior third of the cornea was edematous because of severe endothelial dysfunction.

CONCLUSIONS

Inadequate irrigation of MMC during filtering surgery can cause focal corneal decompensation.

Effect of mitomycin-C on the corneal endothelium during excimer laser surface ablation

PURPOSE

To study the effects of mitomycin-C (MMC) on the corneal endothelium after surface ablation.

METHODS

This prospective observer-masked study comprised 40 consecutive patients (80 eyes) scheduled to have laser-assisted subepithelial keratectomy (LASEK) to correct myopia. The patients were divided into 2 groups. Group 1 included 32 eyes in which the ablation depth was 50 mum or less and that received no MMC. Group 2 included 48 eyes in which the ablation depth exceeded 50 mum and were treated with intraoperative MMC 0.02% for 30 seconds over the ablated zone. Preoperatively and 3 months postoperatively, 3 photographs of the central cornea of each eye were obtained using specular microscopy. A masked observer evaluated the endothelial cell density and compared the results between groups and the preoperative versus the postoperative results within the same group.

RESULTS

The mean patient age was 31.5 years +/- 4.6 (SD) in Group 1 and 33.2 +/- 7.9 years in Group 2 (P = .3). Within-group comparison between the preoperative and postoperative endothelial cell density values showed a statistically significant increase in both groups. The mean values in Group 1 were 2462.5 +/- 226.8 cells/mm(2) preoperatively and 2562.5 +/- 258.7 cells/mm(2) postoperatively (P = .0001). The means in Group 2 were 2466.6 +/- 294.1 cells/mm(2) and 2525 +/- 312.5 cells/mm(2), respectively (P = .0008). The differences in endothelial cell counts between Group 1 and Group 2 preoperatively and postoperatively were not statistically significant (P = .9 and P =.5, respectively).

CONCLUSION

A single intraoperative application of MMC 0.02% for 30 seconds after laser surface ablation did not seem to cause a substantial change in corneal endothelial cell density.

Uses and complications of mitomycin C in ophthalmology

Mitomycin C is a chemotherapeutic agent that acts by inhibiting DNA synthesis. Its use and application in ophthalmology has been increasing in recent years because of its modulatory effects on wound healing. Current applications include pterygium surgery, glaucoma surgery, corneal refractive surgery, cicatricial eye disease, conjunctival neoplasia and allergic eye disease. Although it has been used successfully in these conditions, it has also been associated with significant complications. This article reviews the current trends and uses of mitomycin C in the eye and its reported complications.