Topical Insulin-Utility and Results in Refractory Neurotrophic Keratopathy in Stages 2 and 3

The role of topical insulin in ocular surface restoration: A review

Corneal epithelial defects are one of the most common ocular disorders. Restoring corneal integrity is crucial to reduce pain and regain function, but in cases of neurotrophic or desensitized corneas, healing can be significantly delayed. Treating neurotrophic corneas is challenging for ophthalmologists, and surgical intervention is often indicated to manage refractory cases that are unresponsive to medical therapy. Over the last decade, as more expensive therapeutics reach the market, topical insulin has returned to the forefront as an affordable option to improve corneal wound healing. There is still a paucity of data on the use and the efficacy of topical insulin, with no consensus regarding its indications, preparation, or posology. Here we review the literature on topical insulin for corneal and ocular surface pathologies, with a focus on the current evidence, its mechanisms of action, and its safety profile. Additionally, we share our experience in the field and provide a potential framework for future research.

The Utilization of Topical Insulin for Ocular Surface Diseases: A Narrative Review

Various etiologies, including diabetic keratopathy (DK), dry eye disease (DED), and neurotrophic keratopathy (NK), can disrupt corneal homeostasis, exacerbating corneal epithelial defects. Topical insulin has emerged as a promising therapy for promoting corneal wound healing and addressing underlying pathologies. This review systematically evaluates the efficacy of topical insulin across different corneal disorders. A literature review was conducted across the PubMed, Google Scholar, and Scopus research databases. The search resulted in a total of 19 articles, consisting of clinical trials, retrospective studies, and case reports. In DK, topical insulin accelerates corneal wound healing post-vitreoretinal surgery with lower concentrations showing higher outcomes when compared to conventional therapy, possibly due to improved epithelial stem cell migration. In comparison, the dry-eye disease results are inconclusive regarding patient-reported outcomes and corneal staining. For NK, topical insulin accelerates corneal wound healing and restores corneal nerve sensation. Other persistent epithelial defect (PED) etiologies that have been treated with topical insulin are infection, immune-mediated, mechanical and chemical trauma, and chronic ocular surface alterations. Although individual mechanisms for the benefits of topical insulin for each of these etiologies have not been studied, the literature demonstrates that topical insulin is efficacious for PEDs regardless of etiology. Future clinical trials need to be conducted to further evaluate optimal dosing, duration, and use of topical insulin for the restoration of the corneal surface.

Topical insulin in neurotrophic keratopathy after diabetic vitrectomy

To assess the efficacy and safety of topical insulin (TI) for treating neurotrophic keratopathy (NK) within one-month post-diabetic vitrectomy (DV) compared to conventional non-invasive measures, we conducted this retrospective case-control study including all eyes that developed acute NK (stages 2 and 3) following DV between October 2020 and June 2023. The control group included NK cases managed with preservative-free lubricant eye drops and prophylactic topical antibiotics. In contrast, the study group included NK cases treated with TI [1 unit per drop] four times daily, in addition to the previously mentioned treatment. The primary outcome measure was time to epithelial healing. Secondary outcome measures included any adverse effect of TI or the need for amniotic membrane transplantation (AMT). During the study period, 19 patients with a mean age of 49.3 ± 8.6 years received TI versus 18 controls with a mean age of 52.5 ± 10.7 years. Corneal epithelial healing was significantly faster in the TI-treated group compared to controls, with a mean difference of 12.16 days (95% CI 6.1-18.3, P = 0.001). Survival analysis indicated that the insulin-treated group had 0% and 20% of NK stages 2 and 3, respectively, that failed to achieve corneal epithelial healing, compared to 20% and 66.7% for the control group (P < 0.001). In the control group, two eyes required AMT due to progressive thinning. Additionally, three patients in the control group, progressing to stage 3 NK, were switched to TI, achieving healing after a mean of 14 days. No adverse effects were reported in the TI-treated group. Our study suggests that TI can effectively and safely promote the healing of NK after DV.

Topical Insulin for Ocular Surface Disease

Background: Insulin and insulin-like growth factor (IGF)-1 receptors are present in ocular tissues such as corneal epithelium, keratocytes, and conjunctival cells. Insulin plays a crucial role in the growth, differentiation, and proliferation of corneal epithelial cells, as well as in wound healing processes in various tissues. Purpose: This review explores the potential role of topical insulin in the treatment of ocular surface diseases. Specifically, it examines its impact on corneal nerve regeneration, sub-basal plexus corneal nerves, and its application in conditions like corneal epithelial defects, dry eye disease, and diabetic keratopathy. Methods: The review analyzes studies conducted over the past decade that have investigated the use of topical insulin in ocular surface diseases. It focuses on indications, drug preparation methods, side effects, efficacy outcomes, and variations in insulin concentrations and dosages used. Results: While off-label use of topical insulin has shown promising results in refractory corneal epithelial defects, its efficacy in dry eye disease is yet to be demonstrated. Variations in concentrations, dilutions, and dosing guidelines have been reported. However, limited data on ocular penetration, ocular toxicity, and systemic side effects pose challenges to its widespread utility. Conclusion: This review synthesizes findings from ocular investigations on topical insulin to assess its potential applicability in treating ocular surface and corneal diseases. By highlighting indications, preparation methods, side effects, and efficacy outcomes, it aims to provide insights into the current status and future prospects of using topical insulin in ophthalmic practice.

Recent United States Developments in the Pharmacological Treatment of Dry Eye Disease

Dry eye disease (DED) can arise from a variety of factors, including inflammation, meibomian gland dysfunction (MGD), and neurosensory abnormalities. Individuals with DED may exhibit a range of clinical signs, including tear instability, reduced tear production, and epithelial disruption, that are driven by different pathophysiological contributors. Those affected often report a spectrum of pain and visual symptoms that can impact physical and mental aspects of health, placing an overall burden on an individual's well-being. This cumulative impact of DED on an individual's activities and on society underscores the importance of finding diverse and effective management strategies. Such management strategies necessitate an understanding of the underlying pathophysiological mechanisms that contribute to DED in the individual patient. Presently, the majority of approved therapies for DED address T cell-mediated inflammation, with their tolerability and effectiveness varying across different studies. However, there is an emergence of treatments that target additional aspects of the disease, including novel inflammatory pathways, abnormalities of the eyelid margin, and neuronal function. These developments may allow for a more nuanced and precise management strategy for DED. This review highlights the recent pharmacological advancements in DED therapy in the United States. It discusses the mechanisms of action of these new treatments, presents key findings from clinical trials, discusses their current stage of development, and explores their potential applicability to different sub-types of DED. By providing a comprehensive overview of products in development, this review aims to contribute valuable insights to the ongoing efforts in enhancing the therapeutic options available to individuals suffering from DED.

Topical Insulin Eye Drops: Stability and Safety of Two Compounded Formulations for Treating Persistent Corneal Epithelial Defects

Compounded insulin eye drops were prepared at 1 IU/mL from commercially available subcutaneous insulin by dilution in saline solution or artificial tears. Physicochemical characterization and in vitro tolerance testing in human and conjunctival cells were followed by a 28-day short-term stability study under various conditions. The formulations were isotonic (280-300 mOsm/L), had a pH close to neutral (7-8), medium surface-tension values (<56 MN/m-1), and low (≈1 mPa·s) and medium (≈5 mPa·s) viscosities (compounded normal saline solution and artificial tear-based preparation, respectively). These values remained stable for 28 days under refrigeration. Microbiological stability was also excellent. Insulin potency remained in the 90-110% range in the compounded formulations containing normal saline solution when stored at 2-8 °C for 28 days, while it decreased in those based on artificial tears. Although both formulations were well tolerated in vitro, the compounded insulin diluted in a normal saline solution exhibited better cell tolerance. Preliminary data in humans showed that insulin in saline solution was an effective and safe treatment for persistent corneal epithelial defects. Compounded insulin eye drops diluted in normal saline solution could, therefore, constitute an emergent therapy for the treatment of persistent corneal epithelial defects.

Insulin eye drops improve corneal wound healing in STZ-induced diabetic mice by regulating corneal inflammation and neuropeptide release

INTRODUCTION

In recent years, insulin eye drops have attracted increasing attention from researchers and ophthalmologists. The aim of this study was to investigate the efficacy and possible mechanism of action of insulin eye drops in diabetic mice with corneal wounds.

METHODS

A type 1 diabetes model was induced, and a corneal epithelial injury model of 2.5 mm was established. We used corneal fluorescein staining, hematoxylin-eosin (H-E) staining and the Cochet-Bonnet esthesiometer to examine the process of wound healing. Subsequently, the expression levels of Ki-67, IL-1β, β3-tubulin and neuropeptides, including substance P (SP) and calcitonin gene-related peptide (CGRP), were examined at 72 h after corneal injury.

RESULTS

Fluorescein staining demonstrated an acceleration of the recovery of corneal epithelial injury in diabetic mice compared with the saline treatment, which was further evidenced by the overexpression of Ki-67. Moreover, 72 h of insulin application attenuated the expression of inflammatory cytokines and neutrophil infiltration. Remarkably, the results demonstrated that topical insulin treatment enhanced the density of corneal epithelial nerves, as well as neuropeptide SP and CGRP release, in the healing cornea via immunofluorescence staining.

CONCLUSIONS

Our results indicated that insulin eye drops may accelerate corneal wound healing and decrease inflammatory responses in diabetic mice by promoting nerve regeneration and increasing levels of neuropeptides SP and CGRP.

The Role of Insulin-like Growth Factor (IGF) System in the Corneal Epithelium Homeostasis-From Limbal Epithelial Stem Cells to Therapeutic Applications

The corneal epithelium, comprising three layers of cells, represents the outermost portion of the eye and functions as a vital protective barrier while concurrently serving as a critical refractive structure. Maintaining its homeostasis involves a complex regenerative process facilitated by the functions of the lacrimal gland, tear film, and corneal nerves. Crucially, limbal epithelial stem cells located in the limbus (transitional zone between the cornea and the conjunctiva) are instrumental for the corneal epithelium integrity by replenishing and renewing cells. Re-epithelialization failure results in persistent defects, often associated with various ocular conditions including diabetic keratopathy. The insulin-like growth factor (IGF) system is a sophisticated network of insulin and other proteins essential for numerous physiological processes. This review examines its role in maintaining the corneal epithelium homeostasis, with a special focus on the interplay with corneal limbal stem cells and the potential therapeutic applications of the system components.

Combined Use of Therapeutic Hyper-CL Soft Contact Lens and Insulin Eye Drops for the Treatment of Recalcitrant Neurotrophic Keratopathy

PURPOSE

The aim of this study was to report the successful clinical outcome of recalcitrant neurotrophic keratopathy (NK) treated with insulin eye drops associated with therapeutic Hyper-CL soft contact lens (CL) (EyeYon Medical, Ness Ziona, Israel).

METHODS

This study is a case report.

RESULTS

A 40-year-old man was referred to our clinic for the management of severe recalcitrant NK developed after surgical and adjuvant radiotherapy treatment of adenoid cystic carcinoma of the nasal cavity with basicranial involvement. The patient presented with severe conjunctival hyperemia, a large (7 × 4 mm) central epithelial defect, corneal opacity and thinning, and deep corneal neovascularization. Unpreserved tear substitutes, vitamin A ointment, punctal plug, bandage CL, and autologous serum had been used for the previous 3 months without success. Patient was prescribed insulin eye drops (1 unit per mL), and therapeutic Hyper-CL soft CL was applied to increase the contact time between insulin eye drops and the corneal surface. Follow-up visits were performed at day 10 (T1) and day 20 (T2). A marked reduction in the epithelial defect size was noted at T1 and complete healing was reached at T2. Simultaneously, conjunctival hyperemia and corneal opacity markedly reduced over time with treatment.

CONCLUSIONS

The combination of insulin eye drops and therapeutic Hyper-CL soft CL was effective in determining healing of recalcitrant NK not responsive to standard treatments and bandage CL. It is unclear whether the positive outcomes were determined by insulin eye drops, Hyper-CL, or the combination of both, and future randomized clinical trials are warranted to determine the contribution of each treatment.

Topical Insulin in Neurotrophic Keratopathy: A Review of Current Understanding of the Mechanism of Action and Therapeutic Approach

Neurotrophic keratopathy is a corneal disease characterized by impaired corneal innervation. It can lead to corneal epithelial defects, ulcerations, and perforations. Topical insulin has been shown to be effective in treating this disorder. Insulin is a growth factor that can promote corneal epithelial cell proliferation and migration. In addition, it can also inhibit corneal epithelial cell apoptosis. Topical insulin has previously been found to enhance corneal wound healing. This article reviews the current understanding of the mechanism of action of topical insulin in the treatment of neurotrophic keratopathy.

Antibody-Drug Conjugates and Ocular Toxicity

Antibody-drug conjugates (ADCs) are a growing class of chemotherapeutic agents for the purpose of treating cancers that often have relapsed or failed first- and second-line treatments. ADCs are composed of extremely potent cytotoxins with a variety of side effects, one of the most significant being ocular toxicity. The available literature describes these toxicities as varying in severity and in incidence, although with disparate methods of evaluation and management. Some of the most common toxicities include microcyst-like epithelial keratopathy and dry eye. We discuss proposed mechanisms of ocular toxicity and describe the reports that mention these toxicities. We focus on ADCs with the most published literature and the most significant effects on ocular tissue. We propose areas for further investigation and possible ideas of future management. We provide a comprehensive look at the reports of ADCs in current literature to better inform clinicians on an expanding drug class.

Healing of Chemical Injury-Related Persistent Corneal Epithelial Defects With Topical Insulin

PURPOSE

The purpose of this study was to evaluate the effectiveness of insulin eye drops for treating refractory persistent epithelial defects (PEDs).

METHODS

A prospective, single-center, case series was performed from March 2020 to September 2021. All patients were prescribed insulin eye drops for refractory PEDs that failed on maximum standard medical treatment (including serum eye drops). The drops were used 4 times/day. Patients were followed up at 2 weekly intervals with full slitlamp examination and serial anterior segment photography. The primary end point was resolution of the epithelial defect.

RESULTS

Eleven eyes of 10 patients were treated with insulin eye drops. The mean age of the cohort was 45.4 + 25 years with a mean follow-up of 195.7 + 114.3 days after re-epithelization. The most common causative condition was chemical injury (n = 5, 60%). Mean baseline PED defect was 41.3 + 55.2 mm 2 . Nine of 11 eyes (82%) fully re-epithelized within a mean time of 62.3 + 34.6 days (range 14-112). In 2 patients who did not achieve re-epithelization, one had a reduction in size from 12.25 mm 2 to 4.5 mm 2 and the other had no response. No recurrence in defect was observed in the group that had fully re-epithelized.

CONCLUSIONS

This study showed that the use of topical insulin eye drops led to a successful resolution of PED in 9 of 11 cases. We demonstrate the use of insulin for closure of PEDs in chemical eye injury. Larger controlled studies are required to further evaluate this novel therapy.

Effectiveness of topical insulin for the treatment of surface corneal pathologies

The Purpose is to identify, through a systematic literature review, the current evidence regarding the effectiveness of topical insulin treatment in ocular surface pathologies. A literature search was implemented in Medline (Pubmed), Embase and Web Of Science medical indexing databases by using keywords such as "insulin" AND "cornea" OR "corneal" OR "dry eye" in published papers in English or Spanish within the last eleven years (2011-2022). Nine papers were identified with 180 participants from the United States, Spain, Ireland, Canada, Portugal and Malaysia, with persistent refractory epithelial defects and secondary to vitrectomy, whose extension of the lesion was from 3,75mm² to 65.47mm². The preparation was dissolved with artificial tears and the insulin concentration ranged from 1 IU/ml to 100 IU/ml. In all cases, the resolution of the clinical picture was complete with a healing time from 2.5 days to 60.9 days, the latter being a secondary case to a difficult-to-control caustic burn. Topical insulin has been effective for the treatment of persistent epithelial defects. The intermediate action and low concentrations showed a shorter resolution time in neurotrophic ulcers and induced during vitreoretinal surgery.

Indications and Results of Emergency Penetrating Keratoplasty With Simultaneous Cataract Surgery ("Triple-PKP à Chaud")

PURPOSE

The purpose of this study was to analyze the indications and clinical results of emergency penetrating keratoplasty with simultaneous cataract surgery ("Triple-PKP à chaud").

METHODS

This study included all subjects who underwent Triple-PKP à chaud between 2006 and 2020 at the Department of Ophthalmology, Saarland University Medical Center, Homburg/Saar in Germany. Data obtained from patient records were retrospectively analyzed.

RESULTS

Triple-PKP à chaud was successfully performed in 27 of 29 eyes with a mean age of 66.0 ± 19.9 years. Previous surgery was performed in 20 eyes (69.0%), most frequently amniotic membrane transplantation in 11 eyes (37.9%) and previous keratoplasty in 9 eyes (31.0%). The most common indication was infectious keratitis (62.1%). In 27 subjects (93.1%), capsulorhexis was performed using the open-sky technique. The most frequent intraoperative complication was positive vitreous pressure (24.1%). In 2 eyes (6.9%), no intraocular lens implantation was performed because of posterior capsule rupture. The preoperative uncorrected visual acuity improved from 2.2 ± 0.6 logMAR (range = 3.0-0.7 logMAR) to 1.3 ± 0.7 logMAR (range = 3.0-0.18 logMAR) postoperatively ( P < 0.001). Common postoperative complications were suture loosening (44.4%) and corneal epithelial defects (33.3%). Repeat keratoplasty was necessary in 14 eyes (51.9%), including 9 eyes (64.2%) within 12 months postoperatively. The mean graft survival was 12.2 ± 17.9 months (range = 1-69 mo).

CONCLUSIONS

Triple-PKP is also feasible in emergency conditions. Nevertheless, the surgery is associated with an increased risk of intraoperative and postoperative complications. Combined surgery should, therefore, only be performed in severely diseased eyes with progressed stage of cataract.