A Critical Overview of the Biological Effects of Mitomycin C Application on the Cornea Following Refractive Surgery

LNP-encapsulated miRNA29b for corneal repair: A novel approach to combat fibrosis

Severe corneal injuries often result in corneal scarring, leading to visual impairment and corneal blindness. Currently, there is a lack of effective anti-corneal fibrosis drugs in clinical practice. MicroRNA-based therapies hold significant potential in combating fibrosis. However, the barrier function of the cornea and the fluid environment of the ocular surface reduce drug permeability and bioavailability, presenting significant challenges for local drug application. This study employs microfluidic technology to encapsulate miRNA29b in lipid nanoparticles (LNP) to create an LNP-miRNA29b delivery system (LNP-mir29b) for treating corneal mechanical injuries. In vitro experiments show that LNP-mir29b significantly inhibits the expression of α-smooth muscle actin (α-SMA) in an induced corneal stromal cell fibrosis model. In vivo experiments using rabbit corneal mechanical injury models indicate that LNP-mir29b effectively reduces fibrosis in the corneal stroma, promotes organized rearrangement of stromal collagen fibers, and decreases the expression of fibrosis-related genes, including Col1A2, Col3A1, Fn, and α-SMA. Additionally, LNP-mir29b accelerates the migration of corneal epithelial cells, promotes wound healing of the epithelium, restores the structural integrity of the corneal epithelium. The LNP system proposed in this study offers a novel approach with anti-fibrotic functionality, providing a new strategy for reducing scarring during the corneal injury repair process.

Drug-free hyaluronic acid-microneedle with unexpected inhibition activity on benzalkonium chloride-induced corneal inflammation and stromal scarring

Topical instilling of commercial artificial tears (cAT, containing 0.1 % hyaluronic acid) is widely employed to alleviate clinical manifestations of mild dry eye disease (DED) by preventing the pathological change of corneal epithelium. However, it showed limited therapy effectiveness on heavy DED which has further involved corneal stroma, due to its low stroma-available for hyaluronic acid (HA) resulting from the barrier of corneal epithelium. The present study developed a new microneedle-dosage form of cAT (cAT-MN). This cAT-MN can overstride the corneal epithelium and act as a long-lasting protective agent. Compared to cAT dosing (4 times/day), cAT-MN with one treatment exerted significantly higher therapeutic effects on curbing benzalkonium chloride (BAC)-induced corneal stroma scaring as well as alleviating the DED symptoms in the first 5-day BAC exposure; whereas, showed limited effects in a 10-day BAC exposure. To expand the therapy effects, MNs containing various amounts of HA were prepared. Thereinto, HA(6 %)-MN recovered corneal damage to healthy levels, which could be attributed to adding stroma-available for HA both by increasing the amounts of HA-delivery and enhancing HA-permeation. This study explores a new drug-free microneedle-dosage form of cAT to cure corneal stroma disorders which has expanded its indication, promising a wide clinical use in ophthalmology.

Multifunctional Mesoporous Titanium Dioxide Nanodrug for Corneal Haze Treatment and Its Mechanism

Preventing and treating corneal haze is essential after corneal surface refractive surgery. However, the high intraocular pressure that results after applying traditional anti-inflammatory corticosteroids has attracted great attention. Therefore, we synthesized a multifunctional nanomedicine (Tet@TiO2) with controlled drug release, inflammation targeting, and good biocompatibility for corneal haze treatment. In this study, we discovered that Tet@TiO2 and tetrandrine (Tet), but not TiO2, displayed a characteristic absorption peak at 282 nm. Three weeks after transepithelial photorefractive keratectomy surgery, the Tet@TiO2 group displayed significant decreases in nuclear volume, corneal cell edema, type I and III collagen fiber expression, normal organelle morphology, and collagen fiber arrangement. Compared with those in the control and TiO2 groups, the α-smooth muscle actin, connective tissue growth factor, and type III collagen fibers in the Tet@TiO2 group decreased more significantly after fluorometholone eye drop and Tet treatment, indicating that Tet@TiO2 can effectively inhibit the expression of these inflammatory factors during corneal haze formation. Moreover, Tet@TiO2 showed good, sustained antibacterial properties. More importantly, we found that Tet@TiO2 could effectively down-regulate the expression of phosphatidylinositol 3-kinase (PI3K), protein kinase B (AKT), and B-cell lymphoma-2 (Bcl-2) and up-regulate the expression of Bcl-2-associated X protein (Bax) by modulating the inflammatory PI3K-AKT-Bax/Bcl-2 signaling pathway after corneal surface refractive surgery to effectively prevent and treat corneal haze by reducing the expression of inflammatory factors.

Corneal fibrosis: From in vitro models to current and upcoming drug and gene medicines

Fibrotic diseases are characterised by myofibroblast differentiation, uncontrolled pathological extracellular matrix accumulation, tissue contraction, scar formation and, ultimately tissue / organ dysfunction. The cornea, the transparent tissue located on the anterior chamber of the eye, is extremely susceptible to fibrotic diseases, which cause loss of corneal transparency and are often associated with blindness. Although topical corticosteroids and antimetabolites are extensively used in the management of corneal fibrosis, they are associated with glaucoma, cataract formation, corneoscleral melting and infection, imposing the need of far more effective therapies. Herein, we summarise and discuss shortfalls and recent advances in in vitro models (e.g. transforming growth factor-β (TGF-β) / ascorbic acid / interleukin (IL) induced) and drug (e.g. TGF-β inhibitors, epigenetic modulators) and gene (e.g. gene editing, gene silencing) therapeutic strategies in the corneal fibrosis context. Emerging therapeutical agents (e.g. neutralising antibodies, ligand traps, receptor kinase inhibitors, antisense oligonucleotides) that have shown promise in clinical setting but have not yet assessed in corneal fibrosis context are also discussed.

Regenerative Therapy for Corneal Scarring Disorders

The cornea is a transparent and vitally multifaceted component of the eye, playing a pivotal role in vision and ocular health. It has primary refractive and protective functions. Typical corneal dysfunctions include opacities and deformities that result from injuries, infections, or other medical conditions. These can significantly impair vision. The conventional challenges in managing corneal ailments include the limited regenerative capacity (except corneal epithelium), immune response after donor tissue transplantation, a risk of long-term graft rejection, and the global shortage of transplantable donor materials. This review delves into the intricate composition of the cornea, the landscape of corneal regeneration, and the multifaceted repercussions of scar-related pathologies. It will elucidate the etiology and types of dysfunctions, assess current treatments and their limitations, and explore the potential of regenerative therapy that has emerged in both in vivo and clinical trials. This review will shed light on existing gaps in corneal disorder management and discuss the feasibility and challenges of advancing regenerative therapies for corneal stromal scarring.

Pirfenidone: A Promising Drug in Ocular Therapeutics

Pirfenidone, initially indicated for lung fibrosis, has gone beyond its original purpose, and shown promise in eye care. This detailed review tracks its evolution from lung treatment to aiding eye healing as evidenced by published literature. Pirfenidone's multifaceted attributes extend to mitigating corneal fibrosis, inflammation, and trauma. Through rigorous investigations, its efficacy emerges in diabetic retinopathy, macular degeneration, and postoperative glaucoma interventions. As an unheralded protagonist, pirfenidone reshapes ocular care paradigms, inviting renewed research opportunities.

Molecular and Cellular Mechanisms of Corneal Scarring and Advances in Therapy

On the basis of WHO global blindness data, it may be stated that 23 million people globally suffer from unilateral corneal blindness, while 4 [...].

Laser in situ keratomileusis and surface ablation in pregnancy

PURPOSE

Although corneal refractive surgery is contraindicated during pregnancy, some patients are unaware that they are pregnant when they undergo surgery. Our objectives were to determine the functional outcomes of corneal refractive surgery during pregnancy and to compare the results with those of nonpregnant women.

METHODS

We performed a multicenter, retrospective, interventional case series review of patients who were pregnant and who underwent laser in situ keratomileusis (LASIK) or surface ablation (photorefractive keratectomy, PRK) from September 11, 2002 to December 12, 2020 (group 1, n=82 eyes). Patients were included consecutively. Findings were compared with those of nonpregnant women (group 2, n=164 eyes). Functional (visual and refractive) outcomes are described. Follow-up was at least 550 days (control group, median [IQR], 990 days [715-1496]; study group, 895 days [709-1310]). The setting was Clínica Baviera, Spain, (AIER Eye Hospital Group).

RESULTS

A statistically significant difference was found between the groups in terms of efficacy index (EI). No complications of pregnancy or labor were reported. Similarly, a search of medical records revealed no adverse effects in the infants.

CONCLUSIONS

To the best of our knowledge, this is the first case series on pregnancy and refractive surgery. We do not recommend performing LASIK or surface ablation on pregnant women. Our objective in the present study was to present relevant scientific data obtained from women who underwent refractive surgery while unaware that they were pregnant.

Corneal stromal repair and regeneration

The cornea is a specialized, transparent, avascular, immune-privileged, and heavily innervated tissue that affords 2/3rd of refraction to the eye. Ocular injuries, infections, and genetic factors affect corneal function and cause vision impairment. Presently, a variety of laser/non-laser surgeries, immunosuppressants, and/or corneal transplants are predominantly used to revive sight in human patients. The development of novel, precision-guided, and tissue-targeted non-surgical therapies promoting corneal repair and regeneration based on mechanistic understanding is of paramount importance to reduce the impact of global blindness. Research over the past decade revealed that modulation of pathological signaling pathways and factors by a variety of therapeutic delivery methods effectively treats corneal disorders including corneal scar/haze, inflammation, and angiogenesis in various pre-clinical animal models and are primed for human translation. This review discusses recent advances in the areas of corneal repair, restoration, and regeneration. Herein, we provide an overview of evolving approaches and therapeutic modalities that have shown great promise in reviving corneal transparency and function through the use of small drug molecules, gene therapy, nanomedicine, stem cells, trophic factors, exosomes, stromal equivalents, bioengineered stromal scaffolds, tissue adhesives, and 3D bioprinting.

Andrographolide Inhibits Corneal Fibroblast to Myofibroblast Differentiation In Vitro

Corneal opacification due to fibrosis is a leading cause of blindness worldwide. Fibrosis occurs from many causes including trauma, photorefractive surgery, microbial keratitis (infection of the cornea), and chemical burns, yet there is a paucity of therapeutics to prevent or treat corneal fibrosis. This study aimed to determine if andrographolide, a labdane diterpenoid found in Andrographis paniculate, has anti-fibrotic properties. Furthermore, we evaluated if andrographolide could prevent the differentiation of fibroblasts to myofibroblasts in vitro, given that the transforming growth factor beta-1(TGF-β1) stimulated persistence of myofibroblasts in the cornea is a primary component of fibrosis. We demonstrated that andrographolide inhibited the upregulation of alpha smooth muscle actin (αSMA) mRNA and protein in rabbit corneal fibroblasts (RCFs), thus, demonstrating a reduction in the transdifferentiation of myofibroblasts. Immunofluorescent staining of TGF-β1-stimulated RCFs confirmed a dose-dependent decrease in αSMA expression when treated with andrographolide. Additionally, andrographolide was well tolerated in vivo and had no impact on corneal epithelialization in a rat debridement model. These data support future studies investigating the use of andrographolide as an anti-fibrotic in corneal wound healing.

Corneal fibrosis abrogation by a localized AAV-mediated inhibitor of differentiation 3 (Id3) gene therapy in rabbit eyes in vivo

Previously we found that inhibitor of differentiation 3 (Id3) gene, a transcriptional repressor, efficiently inhibits corneal keratocyte differentiation to myofibroblasts in vitro. This study evaluated the potential of adeno-associated virus 5 (AAV5)-mediated Id3 gene therapy to treat corneal scarring using an established rabbit in vivo disease model. Corneal scarring/fibrosis in rabbit eyes was induced by alkali trauma, and 24 h thereafter corneas were administered with either balanced salt solution AAV5-naked vector, or AAV5-Id3 vector (n = 6/group) via an optimized reported method. Therapeutic effects of AAV5-Id3 gene therapy on corneal pathology and ocular health were evaluated with clinical, histological, and molecular techniques. Localized AAV5-Id3 gene therapy significantly inhibited corneal fibrosis/haze clinically from 2.7 to 0.7 on the Fantes scale in live animals (AAV5-naked versus AAV5-Id3; p < 0.001). Furthermore, AAV5-Id3 treatment significantly reduced profibrotic gene mRNA levels: α-smooth muscle actin (α-SMA) (2.8-fold; p < 0.001), fibronectin (3.2-fold; p < 0.001), collagen I (0.8-fold; p < 0.001), and collagen III (1.4-fold; p < 0.001), as well as protein levels of α-SMA (23.8%; p < 0.001) and collagens (1.8-fold; p < 0.001). The anti-fibrotic activity of AAV5-Id3 is attributed to reduced myofibroblast formation by disrupting the binding of E-box proteins to the promoter of α-SMA, a transforming growth factor-β signaling downstream target gene. In conclusion, these results indicate that localized AAV5-Id3 delivery in stroma caused no clinically relevant ocular symptoms or corneal cellular toxicity in the rabbit eyes.

Effect of Prophylactic Mitomycin C on Corneal Endothelium Following Transepithelial Photorefractive Keratectomy in Myopic Patients

Purpose

This study investigated the effect of prophylactic mitomycin C (MMC) on corneal endothelium to inhibit corneal haze formation post transepithelial photorefractive keratectomy (T-PRK).

Methods

A total of 120 eyes of 60 patients with low, moderate, and high myopia were subjected to T-PRK with intraoperative application of MMC (0.02%) for 30-50s. Patients' files were categorized into three groups according to ablation depths (if ≥100 µm) during T-PRK as follows: (1) Group A - low myopia without MMC, (2) Group B - low myopia with MMC, and (3) Group C - moderate/high myopia with MMC. Preoperative/surgical parameters and refractive outcomes were documented. Cell density (CD), number of cells (NUM), coefficient of variation, central corneal thickness (CCT), hexagonality (HEX/6A), average cell area (AVG), and its standard deviation (SD) were evaluated using specular microscopy preoperatively and postoperatively.

Results

Overall, 119 out of 120 eyes showed significant prevention of corneal haze. Groups A and C showed no significant changes in endothelial CD and NUM. Group B showed a non-significant reduction in CD. However, all three groups showed significant variations in HEX/6A, CCT, AVG, and SD.

Conclusion

The MMC application did not significantly affect corneal endothelial density or number and can be used safely and effectively to prevent corneal haze following T-PRK in myopia.

RecA and RecB: probing complexes of DNA repair proteins with mitomycin C in live Escherichia coli with single-molecule sensitivity

The RecA protein and RecBCD complex are key bacterial components for the maintenance and repair of DNA. RecBCD is a helicase-nuclease that uses homologous recombination to resolve double-stranded DNA breaks. It also facilitates coating of single-stranded DNA with RecA to form RecA filaments, a vital step in the double-stranded break DNA repair pathway. However, questions remain about the mechanistic roles of RecA and RecBCD in live cells. Here, we use millisecond super-resolved fluorescence microscopy to pinpoint the spatial localization of fluorescent reporters of RecA or RecB at physiological levels of expression in individual live Escherichia coli cells. By introducing the DNA cross-linker mitomycin C, we induce DNA damage and quantify the resulting steady state changes in stoichiometry, cellular protein copy number and molecular mobilities of RecA and RecB. We find that both proteins accumulate in molecular hotspots to effect repair, resulting in RecA stoichiometries equivalent to several hundred molecules that assemble largely in dimeric subunits before DNA damage, but form periodic subunits of approximately 3-4 molecules within mature filaments of several thousand molecules. Unexpectedly, we find that the physiologically predominant forms of RecB are not only rapidly diffusing monomers, but slowly diffusing dimers.

Potential Ophthalmological Side Effects Induced by Anti-Neoplastic Regimens for the Treatment of Genitourinary Cancers: A Review

The outcomes of patients with genitourinary (GU) cancers have been steadily improving in recent years. Novel therapies have entered our armamentarium, while several other regimens are currently being studied in clinical trials. This recent explosion of new agents has improved patient survival and the quality of life for patients, but has also significantly increased the frequency of several side effects. The current review will focus on the potential ocular adverse reactions of GU neoplastic treatments. The broad spectrum of manifestations of ocular toxicity underscores the uniqueness and complexity of the anatomic, physiologic, and metabolic features of the human eye. Most side effects are mild in severity and transient, but some can be severe, disabling, and irreversible. Clinicians should be aware of complications that might be vision threatening and impact the patient's quality of life. In this review, we focused on the ocular toxicity of the antineoplastic regimens that are currently used for the treatment of GU, including prostate cancer, bladder cancer, renal cell carcinoma, testicular cancer, pheochromocytoma, adrenocortical carcinoma, and penile cancer.

Neuroimmune crosstalk in the cornea: The role of immune cells in corneal nerve maintenance during homeostasis and inflammation

In the cornea, resident immune cells are in close proximity to sensory nerves, consistent with their important roles in the maintenance of nerves in both homeostasis and inflammation. Using in vivo confocal microscopy in humans, and ex vivo immunostaining and fluorescent reporter mice to visualize corneal sensory nerves and immune cells, remarkable progress has been made to advance our understanding of the physical and functional interactions between corneal nerves and immune cells. In this review, we summarize and discuss recent studies relating to corneal immune cells and sensory nerves, and their interactions in health and disease. In particular, we consider how disrupted corneal nerve axons can induce immune cell activity, including in dendritic cells, macrophages and other infiltrating cells, directly and/or indirectly by releasing neuropeptides such as substance P and calcitonin gene-related peptide. We summarize growing evidence that the role of corneal intraepithelial immune cells is likely different in corneal wound healing versus other inflammatory-dominated conditions. The role of different types of macrophages is also discussed, including how stromal macrophages with anti-inflammatory phenotypes communicate with corneal nerves to provide neuroprotection, while macrophages with pro-inflammatory phenotypes, along with other infiltrating cells including neutrophils and CD4⁺ T cells, can be inhibitory to corneal re-innervation. Finally, this review considers the bidirectional interactions between corneal immune cells and corneal nerves, and how leveraging this interaction could represent a potential therapeutic approach for corneal neuropathy.

Dual-response electrochemical electrode for sensitive monitoring of topotecan and mitomycin as anticancer drugs in real samples

This research paper employed an innovative electrochemical electrode to simultaneously determine topotecan (TPT) and mitomycin (MMC) as anticancer agents. For this purpose, a novel nanocomposite was synthesized using a hydrothermal procedure. The nanocomposites were characterized using FTIR, STEM, FESEM, mapping analysis, EDX, and XRD methods. The novelty of this work is the successful synthesis of Fe₃O₄ decorated on the surface of CuCo₂S₄ (Fe₃O₄@CuCo₂S₄) nanocomposites showed two separate anodic peaks at 0.8 V for TPT and 1.0 V for MMC with potential separation of 0.2 V. This was enough for the simultaneous electrochemical determination of topotecan and mitomycin on a glassy carbon electrode (GCE), simultaneously. At optimized conditions, the developed electrode exhibited linear responses with TPT and MMC concentration in the ranges of 0.01-0.89 and 0.89-8.95 μM for topotecan and 0.1-19.53 μM for mitomycin. The detection limits were observed as 6.94 nM and 80.00 nM for topotecan and mitomycin, respectively. The fabricated Fe₃O₄@CuCo₂S₄/GCE showed high sensitivity, long-term stability, and repeatability towards the sensing of TPT and MMC simultaneously and can be utilized in real samples. The obtained results confirmed that the fabricated Fe₃O₄@CuCo₂S₄/GCE nanocomposites can be utilize in the simultaneous electrochemical determination of topotecan and mitomycin in real samples.

Effect of mitomycin-C on corneal endothelial cell parameters after refractive surface ablation procedures

Background

The effect of mitomycin-C (MMC) on the reduction of endothelial cell count in the cornea remains controversial. We aimed to evaluate the effect of MMC on corneal endothelial cell parameters after refractive surface ablation procedures, including photorefractive keratectomy (PRK) and laser epithelial keratomileusis (LASEK).

Methods

In this interventional, comparative, follow-up study, 342 eyes of 171 patients were followed up for 6 months. Patients undergoing PRK or LASEK were included and were divided into two groups: group one (188 eyes of 94 patients) with an ablation depth of ≥ 65 µm and who received intraoperative 0.02% MMC for 30 s, and group two (154 eyes of 77 patients) with an ablation depth of < 65 µm and who received balanced salt solution for 30 s. Changes in endothelial cell density (ECD), central corneal thickness (CCT), coefficient of variation (CV), and hexagonality values were compared between the groups at 3 and 6 months after surgery.

Results

The mean (standard deviaiton [SD]) age of the patients was 28.11 (6.56) years. The mean (SD) ECD did not change significantly in either group between the baseline and at 3 and 6 months postoperatively. The baseline mean ECD was significantly higher in group one than that in group two (P < 0.001) and remained so at 3 (P = 0.002) and 6 months (P = 0.022) postoperatively. The baseline hexagonality value was lower in group one (P = 0.173), with a gradual decrease during the postoperative follow-up as compared with that in group two (P = 0.016 and 0.001 at 3 and 6 months postoperatively, respectively). Group one had a significantly lower CCT at 3 and 6 months postoperatively (both P < 0.001) and a higher mean CV (3 months: P = 0.028; 6 months: P = 0.328).

Conclusions

A single intraoperative application of MMC for 30 s as prophylaxis for corneal haze development during refractive surface ablation procedures had no significant effect on ECD up to 6 months postoperatively. Future studies with a contralateral-eye design (to neutralize factors specific to the individual patient), a larger sample size, and longer follow-up are necessary to confirm or disprove our observations.

Nd:YAG fourth harmonic (266-nm) generation for corneal reshaping procedure: An ex-vivo experimental study

Corneal reshaping is a common medical procedure utilized for the correction of different vision disorders relying on the ablation effect of the UV pulsed lasers, especially excimer lasers (ArF) at 193 nm. This wavelength is preferred in such medical procedures since laser radiation at 193 nm exhibits an optimum absorption by corneal tissue. However, it is also significantly absorbed by the water content of the cornea resulting in an unpredictability in the clinical results, as well as the high service and operation cost of the commercial ArF excimer laser device. Consequently, other types of solid-state UV pulsed lasers have been introduced. The present work investigates the ablation effect of solid-state laser at 266 nm in order to be utilized in corneal reshaping procedures. Different number of pulses has been applied to Polymethyl Methacrylate (PMMA) and ex-vivo rabbit cornea to evaluate the ablation effect of the produced laser radiation. PMMA target experienced ellipse-like ablated areas with a conical shape in the depth. The results revealed an almost constant ablation area regardless the number of laser pulses, which indicates the stability of the produced laser beam, whereas the ablation depth increases only with increasing the number of laser pulses. Examination of the ex-vivo cornea showed a significant tissue undulation, minimal thermal damage, and relatively smooth ablation surfaces. Accordingly, the obtained 266-nm laser specifications provide promising alternative to the traditional 193-nm excimer laser in corneal reshaping procedure.

Immune responses to injury and their links to eye disease

The eye is regarded as an immune privileged site. Since the presence of a vasculature would impair vision, the vasculature of the eye is located outside of the central light path. As a result, many regions of the eye evolved mechanisms to deliver immune cells to sites of dysgenesis, injury, or in response to the many age-related pathologies. While the purpose of these immune responses is reparative or protective, cytokines released by immune cells compromise visual acuity by inducing inflammation and fibrosis. The response to traumatic or pathological injury is distinct in different regions of the eye. Age-related diseases impact both the anterior and posterior segment and lead to reduced quality of life and blindness. Here we focus attention on the role that inflammation and fibrosis play in the progression of age-related pathologies of the cornea and the lens as well as in glaucoma, the formation of epiretinal membranes, and in proliferative vitreoretinopathy.

Mitomycin C for the prevention of corneal haze in photorefractive keratectomy: a meta-analysis and trial sequential analysis

PURPOSE

To evaluate the anti-haze effect and visual outcome after intraoperative mitomycin C (MMC) use during photorefractive keratectomy (PRK) in myopia or myopic astigmatism patients.

METHODS

We searched in PubMed, EMBASE, Cochrane Library and Google Scholar comprehensively to obtain studies comparing the clinical effects after PRK with and without MMC published until February 2020. Meta-analysis of primary outcome (corneal haze rate) and secondary outcomes [predictability, efficacy, safety and corneal endothelial cell density (ECD)] were conducted. We used trial sequential analysis (TSA) in an effort to collect firm evidence supporting our conclusion.

RESULTS

Of the included 11 randomized controlled trials, five cohort and one case-control studies, 3536 eyes (2232 and 1304 in the MMC and control groups, respectively) were enrolled for meta-analysis. The TSA disclosed strong evidence of decline in corneal haze rate in the MMC group compared with that of the control group. In the subgroup analysis of duration, MMC seemed to reduce corneal haze rate in early-onset and late-onset haze. Predictability of refraction and visual acuity were greater in the MMC groups, not significantly though. The proportion of patients losing at least two lines of best corrected visual acuity postoperatively in the MMC groups was lower than that in the control groups. The corneal postoperative ECD showed no significant difference between the MMC and control groups.

CONCLUSION

Our meta-analysis revealed that MMC is an important anti-haze agent in PRK for reducing both early- and late-onset haze and can also help improving predictability of refraction and subjective postoperative visual acuity.

Effect of Bandage Contact Lens Exchange on Pain and Healing After Photorefractive Keratectomy-A Randomized Control Trial

OBJECTIVE

To evaluate the corneal re-epithelialization and patient-perceived pain after bandage contact lens (BCL) exchange on day one, after photorefractive keratectomy (PRK).

METHODS

A randomized controlled trial, of all patients who underwent bilateral transepithelial-PRK (trans-PRK) or bilateral alcohol debridement and PRK (A-PRK), between March and October 2019. One eye of each patient was randomly assigned to BCL exchange on the first postoperative day (exchange group) and the BCL was not exchanged in the fellow eye (control group). Patients were evaluated daily until healing was complete. At each visit, the corneal epithelial defect was measured, and a questionnaire was used to assess pain, photophobia, and excessive tearing. P<0.05 was statistically significant.

RESULTS

The study sample was comprised of 56 patients (mean age 27.2±5.7 years). Trans-PRK was performed in 20 (34.5%) and A-PRK in 36 (64.3%) patients. At day 3, 40 (71.4%) eyes of the exchange group healed completely compared with 38 (67.9%) eyes of the control group (P=0.5). At day-1 follow-up, the pain score was 1.87±1.4 in the exchange group and 2.29±1.3 in the control group (P=0.009). The mean pain score was 1.58±1.4 among patients who underwent A-PRK and 2.35±1.2 among patients operated by trans-PRK (P=0.04).

CONCLUSION

The epithelial healing did not vary when BCL was exchanged one day after refractive surgery. However, postoperative pain score after PRK was lower at day 1, when the BCL was exchanged. Compared with A-PRK, trans-PRK group demonstrated a higher pain score in the early postoperative phase.

Iatrogenic Ocular Surface Diseases Occurring during and/or after Different Treatments for Ocular Tumours

Simple Summary

The ocular surface represents a finely regulated system that allows the protection of the eye. It can be affected by therapies used for the treatment of various intraocular tumours, particularly conjunctival cancers and uveal melanoma. In these conditions, treatments are chosen according to the characteristics of the lesion, and include a combination of selective surgery, anticancer eye drops, and/or radiotherapy delivered through different mechanisms. Possible side effects affecting the ocular surface range from transient dry eye or keratitis up to more severe complications such as corneal melting and perforation. These complications deserve careful evaluation for the risk of permanent sight-threatening sequelae. Physicians involved in the management of patients affected by ocular tumours should be aware of this risk in order to reach an early diagnosis and promptly set up an adequate treatment. The present review summarizes acute and chronic complications affecting the ocular surface following different therapies for the treatment of conjunctival cancers and uveal melanoma, and also reports clinical cases of representative patients who experienced these complications.

Abstract

The ocular surface represents a finely regulated system that allows the protection of the eye. It is particularly susceptible to different treatments for intraocular tumours, such as uveal melanoma and conjunctival cancers. Traditionally, the management of ocular tumours depends on the characteristics of the lesion, and is based on a combination of selective surgery, topical chemotherapy, and/or radiotherapy delivered through different mechanisms (e.g., charged-particle radiotherapy or brachytherapy). Possible complications involving the ocular surface range from transient dry eye disease or keratitis up to corneal melting and perforation, which in any case deserve careful evaluation for the risk of permanent sigh-threatening complications. Clinicians involved in the management of these patients must be aware of this risk, in order to reach an early diagnosis and promptly set up an adequate treatment. The present review of the literature will summarize acute and chronic complications affecting the ocular surface following different therapies for the treatment of ocular tumours.

Safety and efficacy of combination of suberoylamilide hydroxyamic acid and mitomycin C in reducing pro-fibrotic changes in human corneal epithelial cells

Corneal haze post refractive surgery is prevented by mitomycin c (MMC) treatment though it can lead to corneal endothelial damage, persistent epithelial defects and necrosis of cells. Suberanilohydroxamic acid (SAHA) however has been proposed to prevent corneal haze without any adverse effects. For clinical application we have investigated the short and long term outcome of cells exposed to SAHA. Human donor cornea, cultured limbal epithelial cells, corneal rims and lenticules were incubated with SAHA and MMC. The cells/tissue was then analyzed by RT-qPCR, immunofluorescence and western blot for markers of apoptosis and fibrosis. The results reveal that short term exposure of SAHA and SAHA + MMC reduced apoptosis levels and increased αSMA expression compared to those treated with MMC. Epithelial cells derived from cultured corneal rim that were incubated with the MMC, SAHA or MMC + SAHA revealed enhanced apoptosis, reduced levels of CK3/CK12, ∆NP63 and COL4A compared to other treatments. In SAHA treated lenticules TGFβ induced fibrosis was reduced. The results imply that MMC treatment for corneal haze has both short term and long term adverse effects on cells and the cellular properties. However, a combinatorial treatment of SAHA + MMC prevents expression of corneal fibrotic markers without causing any adverse effect on cellular properties.

Dependence of the heating effect on tissue absorption coefficient during corneal reshaping using different UV lasers: A numerical study

Corneal reshaping using laser ablation effect is a well-known ophthalmologic operation implemented to correct many vision disorders. UV pulsed lasers are utilized in this surgery due to their high absorption in corneal tissue without affecting the other parts of the eye. Ideally ablation may not be associated with heat transport, since high temperature is the enemy of soft tissues. However, the thermal effect of this procedure can cause tissue damage if the temperature rises above the safety level without appropriate handling. In the present study, we try to find the trade-off between efficient ablation and minimal temperature rise. So the thermal effect on the corneal tissue after applying five UV wavelengths; 193, 210, 213, 223 and 248 nm has been simulated and investigated by solving Penne's bio-heat transfer equation using the finite element method. A 3D model of the human cornea is constructed using COMSOL Multiphysics computer software and the temperature rise is determined at the end of the laser pulse. The same spot size and pulse duration are used for each wavelength. While the absorption coefficient of the corneal tissue is the only variable as it is a wavelength dependent. The proposed results show that, the heating effect is directly proportional to the absorption coefficient. The highest recorded temperature was 259 °C at 193 nm, while, the minimum value was (70.1 °C) recorded at 248 nm at which the cornea has the lowest absorption coefficient.

Clinical outcomes of transepithelial photorefractive keratectomy versus femtosecond laser assisted keratomileusis for correction of high myopia in South Egyptian population

AIM

To evaluate the safety and efficacy of transepithelial photorefractive keratectomy (t-PRK) with adjuvant mitomycin C (MMC) versus femtosecond laser assisted keratomileusis (Femto-LASIK) in correction of high myopia.

METHODS

Prospective randomized comparative study including 156 eyes of 156 patients with high myopia and a spherical equivalent refraction (SER) <-6.00 D. They were divided randomly into two groups: Group A included 72 eyes treated with t-PRK with adjuvant MMC and Group B included 84 eyes treated with Femto-LASIK. Visual acuity, SER, corneal topography, pachymetry and keratometry were assessed for 12mo postoperatively.

RESULTS

The preoperative mean SER was -8.86±1.81 and -9.25±1.70 D in t-PRK MMC group and Femto-LASIK respectively (P=0.99) which improved to -0.65±0.43 D and -0.69±0.50 D at 12mo follow up. Mean SER remained stable during the 12mo of follow-up, with no statistically significant difference between the two groups (P=0.64). In t-PRK MMC group, only six eyes needed retreatment after six months of follow up. And two eyes showed haze (one reversible haze grade 2, while the other had dense irreversible haze grade 4).

CONCLUSION

t-PRK MMC provides safe and satisfactory visual outcomes and acceptable risk as Femto-LASIK in patients with high myopia.

Identification of novel predictive factors for post surgical corneal haze

Molecular factors altered in corneas that develop haze post refractive surgery have been described, but pre-existing factors that predispose clinically normal corneas to aberrant fibrosis post surgery and the role of the corneal epithelium remains unknown. We analyzed the global gene expression in epithelium collected intraoperatively from subjects undergoing photorefractive keratectomy. Subjects were grouped into those that developed haze 12 months post surgery (n = 6 eyes; haze predisposed) and those that did not develop haze in a similar follow up duration (n = 11 eyes; controls). Ontological analysis of 1100 upregulated and 1780 downregulated genes in the haze predisposed group revealed alterations in pathways associated with inflammation, wnt signaling, oxidative stress, nerve functions and extra cellular matrix remodeling. Novel factors such as PREX1, WNT3A, SOX17, GABRA1and PXDN were found to be significantly altered in haze predisposed subjects and those with active haze(n = 3), indicating their pro-fibrotic role. PREX1 was significantly upregulated in haze predisposed subjects. Ectopic expression of PREX1 in cultured human corneal epithelial cells enhanced their rate of wound healing while its ablation using shRNA reduced healing compared to matched controls. Recombinant TGFβ treatment in PREX1 overexpressing corneal cells led to enhanced αSMA expression and Vimentin phosphorylation while the converse was true for shPREX1 expressing cells. Our data identify a few novel factors in the corneal epithelium that may define a patient’s risk to developing post refractive corneal haze.

Transient Mitomycin C-treatment of human corneal epithelial cells and fibroblasts alters cell migration, cytokine secretion, and matrix accumulation

A single application of Mitomycin C (MMC) is used clinically in ophthalmology to reduce scarring and enhance wound resolution after surgery. Here we show in vitro that a 3-hour MMC treatment of primary and telomerase immortalized human corneal limbal epithelial (HCLE) cells impacts their migration and adhesion. Transient MMC treatment induces HCLE expression of senescence associated secretory factors, cytokine secretion, and deposition of laminin 332 for several days. Transient MMC treatment also reduces migration and deposition of transforming growth factor-β1 (TGFβ1)-stimulated collagen by corneal fibroblasts. Using conditioned media from control and MMC treated cells, we demonstrate that factors secreted by MMC-treated corneal epithelial cells attenuate collagen deposition by HCFs whereas those secreted by MMC-treated HCFs do not. These studies are the first to probe the roles played by corneal epithelial cells in reducing collagen deposition by corneal fibroblasts in response to MMC.