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.

The measurement of corneal sensation allows clinicians to assess the status of corneal innervation and serves as a crucial indicator of corneal disease and eye health. Many devices are available to assess corneal sensation, including the Cochet-Bonnet aesthesiometer, the Belmonte Aesthesiometer, the Swiss Liquid Jet Aesthesiometer, and the newly introduced Corneal Esthesiometer Brill. Increasing the clinical use of in vivo confocal microscopy and optical coherence tomography will allow for greater insight into the diagnosis, classification, and monitoring of ocular surface diseases such as neurotrophic keratopathy; however, formal esthesiometric measurement remains necessary to assess the functional status of corneal nerves. These aesthesiometers vary widely in their mode of corneal stimulus generation and their relative accessibility, precision, and ease of clinical use. The development of future devices to optimize these characteristics, as well as further comparative studies between device types should enable more accurate and precise diagnosis and treatment of corneal innervation deficits. The purpose of this narrative review is to describe the advancements in the use of aesthesiometers since their introduction to clinical practice, compare currently available devices for assessing corneal innervation and their relative limitations, and discuss how the assessment of corneal innervation is crucial to understanding and treating pathologies of the ocular surface.

BACKGROUND: Ultrasound cycloplasty is a noninvasive surgery used to reduce intraocular pressure in patients with glaucoma, with fewer severe complications. This report presents several cases of iris neovascularization and neurotrophic keratopathy following ultrasound cycloplasty.
METHODS: Six patients diagnosed with refractory glaucoma underwent ultrasound cycloplasty at our clinic. Three cases developed iris neovascularization at postoperative day 3, week 2 and week 4 respectively, with intraocular pressure ranging from 12 to 24 mmHg. The other three cases developed neurotrophic keratopathy at postoperative week 3, week 6 and week 8 which completely healed within 60 days.
CONCLUSIONS: Iris neovascularization and neurotrophic keratopathy can be triggered after ultrasound cycloplasty, which are uncommon and self-limited but potentially vision-threatening. Preoperative risk assessment and regular postoperative follow-up are recommended to manage complications effectively.

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.

OBJECTIVE: To evaluate the prognostic ability of non-contact esthesiometry corneal and lid margin sensitivity measurements in detecting symptoms and signs of dry eye disease, as defined by the global consensus TFOS DEWS II criteria.
METHODS: A total of 87 community residents (58 females; mean ± SD age, 53 ± 16 years) were recruited in an investigator-masked, prospective, prognostic accuracy study. Dry eye symptomology, tear film parameters, and ocular surface characteristics were evaluated in a single clinical session, and non-contact esthesiometry corneal and lid margin sensitivity measurements performed by an independent masked assessor.
RESULTS: Overall, 49 (56%) participants fulfilled the TFOS DEWS II criteria for dry eye disease, while 57 (66%) exhibited clinical symptoms, and 67 (77%) had positive signs. The prognostic abilities of corneal and lid margin sensitivity measurements were significantly greater than chance for the detection dry eye signs (both p ≤ 0.03), but not for symptoms or overall disease diagnosis (all p > 0.10). The Youden-optimal prognostic cut-offs for corneal and lid margin sensitivity thresholds were both ≥0.8 mbar for the detection of clinical dry eye signs. Lid margin sensitivity demonstrated marginally higher predictive performance than corneal sensitivity (C-statistic, 0.688 versus 0.658), and was significantly correlated with tear film stability, corneal, conjunctival and lid wiper staining (all p < 0.05).
CONCLUSIONS: Corneal and lid margin sensitivity demonstrated moderate prognostic utility for detecting clinical dry eye signs. Future research is warranted to investigate the utility of incorporating non-contact esthesiometry in the workup for dry eye disease and neurotrophic keratopathy.

Neurotrophic keratopathy (NK) is a challenging disease with the reduced innervation to the cornea. To establish a genetic and stable mouse model of NK, we utilized the TRPV1-DTR mice with intraperitoneal injection of diphtheria toxin (DT) to selectively eliminate TRPV1 neurons. After DT administration, the mice exhibited robust ablation of TRPV1 neurons in the trigeminal ganglion, accompanied with reduced corneal sensation and nerve density, as well as the decreased calcitonin-gene-related peptide (CGRP) and substance P levels. According to disease progression of TRPV1 neuronal ablation, tear secretion was reduced from day 3, which followed by corneal epithelial punctate lesions from day 7. From day 11 to day 16, the mice exhibited persistent corneal epithelial defects and stromal edema. By day 21, corneal ulceration and stromal melting were observed with the abundant inflammatory cell infiltration, corneal neovascularization, and enhanced cell apoptosis. Moreover, subconjunctival injection of CGRP delayed the NK progression with the characteristics of reduced severe corneal epithelial lesions and corneal inflammation. In addition, the impairments of conjunctival goblet cells, lacrimal gland, and meibomian gland were identified by the diminished expression of MUC5AC, AQP5, and PPARγ, respectively. Therefore, these results suggest that the TRPV1-DTR mice may serve as a reliable animal model for the research of NK pathogenesis.

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.

BACKGROUND: Cenegermin is approved for treatment of neurotrophic keratopathy (NK) and has been studied in patients with stage 2 or 3 NK. This study evaluated the efficacy and safety of cenegermin in adults with stage 1 NK.
METHODS: This was a phase IV, multicenter, prospective, open-label, uncontrolled trial. Adults with stage 1 NK (Mackie criteria) and decreased corneal sensitivity (≤ 4 cm) received 1 drop of cenegermin 20 mcg/ml in the affected eye(s) 6 times/day for 8 weeks with a 24-week follow-up.
RESULTS: Of 37 patients, corneal epithelial healing was observed in 84.8% (95% confidence interval [CI] 68.1-94.9%; P < 0.001) at week 8; 95.2% (95% CI 76.2-99.9%; P < 0.001) of those patients remained healed at the end of the 24-week follow-up (week 32). At week 8, 91.2% (95% CI 76.3-98.1%; P < 0.001) of patients experienced improved corneal sensitivity; this improvement was observed in 82.1% (95% CI 63.1-93.9%; P < 0.001) of patients at week 32. Mean best-corrected distance visual acuity change from baseline at week 8 was - 0.10 logMAR (standard deviation [SD], 0.15; 95% CI - 0.16 to - 0.05; P < 0.001) and at week 32 was - 0.05 logMAR (SD, 0.16; 95% CI - 0.11 to 0.01; P = 0.122). At weeks 8 and 32, 15.2% (95% CI 5.1-31.9%; P < 0.001) and 10.7% (95% CI 2.3-28.2%; P < 0.001) of patients, respectively, had a 15-letter gain from baseline. At least one adverse event (AE) was reported by 73.0% and 45.7% of patients during the treatment and follow-up periods, respectively. The most common treatment-related, treatment-emergent AEs were eye pain (37.8%), blurred vision (10.8%), and eyelid pain (8.1%); these were mostly mild or moderate and were only reported during the treatment period.
CONCLUSIONS: These results support the potential use of cenegermin for treating patients with stage 1 NK, and future confirmatory studies would be beneficial to elaborate on these findings.
BACKGROUND: DEFENDO; NCT04485546.

OBJECTIVE: To describe the frequency, clinical presentation, and outcomes of neurotrophic keratopathy (NK).
METHODS: Retrospective cohort study of Kaiser Permanente Northern California patients diagnosed with NK using ICD-10 code H16.23X from October 1, 2016 through May 31, 2021 was conducted. The electronic medical record was used to obtain demographic information, systemic and ocular comorbidities, corrected distance visual acuity (CDVA), Mackie stage, laterality, etiology, complications, interventions, and medications. The data were analyzed using cross-tabulations.
RESULTS: 354 eyes in 322 patients presented with an initial or recurrent episode of NK. 9.9% had bilateral NK, 40% were 75 years and older, and 55% were women. Baseline vision was worse than 20/100 in 47.5%. Mackie staging was stage 1 in 37.3%, stage 2 in 32.5%, and stage 3 in 30.2%. Herpetic causes comprised 34.9%, followed by diabetes (12.4%), ocular surgery (10.4%), and central nervous system etiologies (9.0%). Topical antibiotics (74.5%), steroids (54.0%), autologous serum tears (46.0%), and oral antivirals (43.8%) were the most used treatments. There were 8 eyes with perforation, 4 endophthalmitis, and 3 evisceration/enucleations. An increased difference of approximately 0.1 logMAR in CDVA in the affected eye compared with the unaffected eye over one year was not statistically significant. Clinic utilization for stage 2 (average visits per month, 3.2) and stage 3 (5.0) NK gradually decreased over 6 months.
CONCLUSIONS: Summary of the current management, outcomes, and healthcare utilization of NK provides valuable benchmarks in assessing the disease burden in the community and for further development of novel therapies.

BACKGROUND: Neurotrophic keratopathy (NK) is a rare degenerative ocular disease that can be difficult to treat. There were no effective resolutive treatments for severe NK caused by ocular graft-versus-host disease (oGVHD) along with virus infection. To address this question, we designed a prospective cohort study to evaluate the efficacy and safety of topical recombinant human nerve growth factor (rhNGF) in patients with recalcitrant NK of oGVHD and viral infection.
METHODS: This prospective cohort study enrolled patients with recalcitrant NK diagnosed with oGVHD and treated with rhNGF. Clinical evaluations included the range of epithelial defects, best corrected visual acuity, intraocular pressure, slit-lamp examination, and corneal fluorescein staining. Examinations of the central corneal thickness, corneal sensitivity, and nerve fiber regeneration were performed at each visit at 4, 8, 12, 20 weeks and 6 months, respectively, after initiating rhNGF treatment.
RESULTS: All enrolled patients were diagnosed with NK at stage 2 (7 eyes, 63.6%) or stage 3 (4 eyes, 36.4%) and responded to rhNGF treatment. Five of 11 (45.5%) and 9 of 11 eyes (81.8%) achieved complete corneal epithelial healing after 4 and 8 weeks, respectively. All 11 eyes (100%) achieved complete corneal healing after 12 weeks. There was also a significant reduction in the corneal ulcer area during each visit (P < 0.001), as well as in the corneal fluorescein staining score (P < 0.010). There was a significant improvement in corneal sensation when compared to the baseline (P < 0.050).
CONCLUSIONS: Topical treatment with rhNGF effectively promoted the complete corneal healing of persistent epithelial defects and corneal ulcers in patients with recalcitrant NK in oGVHD and viral infection.