Corneal Neurotization: A Review of Pathophysiology and Outcomes

Corneal Neurotization, Recent Progress, and Future Perspectives

Neurotrophic keratopathy (NK) is a rare degenerative disease caused by impairment of the trigeminal nerve, leading to corneal anesthesia, epithelial breakdown, and progressive vision loss. Conventional treatments primarily focus on symptom management and the prevention of complications, but they do not address the underlying nerve dysfunction. Corneal neurotization (NT) has emerged as a promising surgical intervention aimed at restoring corneal sensation and improving ocular surface homeostasis. This review evaluates the outcomes of corneal neurotization in patients with NK and compares the effectiveness of direct (DNT) and indirect (INT) techniques. Studies have reported significant improvements in corneal sensitivity, with success rates ranging from 60.7% to 100% (mean: 90%). Most patients experienced recovery of corneal sensation, as measured by the Cochet-Bonnet aesthesiometer, with no significant differences in outcomes between DNT and INT. Indirect neurotization using a sural nerve graft was the most commonly employed technique (63% of cases), while the use of acellular allografts demonstrated comparable efficacy and simplified the procedure. Postoperative corneal sensitivity increased significantly, from a preoperative average of 2.717 mm to 36.01 mm, with reinnervation typically occurring within 4-6 months and peaking at 12 months. In vivo confocal microscopy confirmed the presence of nerve regeneration. Neurotization was found to be safe, with minimal donor-site complications, which generally resolved within one year. Although the procedure improves corneal sensation and tear film stability, visual acuity outcomes remain variable due to pre-existing corneal damage. Early intervention is, therefore, recommended to prevent irreversible scarring. However, the number of patients undergoing the procedure remains limited, making it difficult to draw definitive conclusions. Most available studies consist of small case series. Further research with larger sample sizes is needed to refine surgical techniques and optimize patient selection, thereby improving outcomes in the management of NK.

Corneal neurotization for the treatment of neurotrophic keratopathy

PURPOSE OF REVIEW

Corneal neurotization, a surgical technique that restores corneal sensation by transferring a healthy sensory nerve to the neurotrophic cornea, has emerged as a treatment of moderate to severe neurotrophic keratopathy. This review provides an overview of the indications, surgical techniques, and outcomes of corneal neurotization.

RECENT FINDINGS

Corneal neurotization can be performed via direct nerve transfer or indirect nerve grafting, with comparable long-term outcomes. Advances such as minimally invasive and endoscopic techniques, nerve allografts, and alternative donor nerves have expanded its accessibility. Studies show significant improvements in corneal sensation, epithelial integrity, and ocular surface health, with younger patients achieving faster and more complete recovery. The procedure has demonstrated efficacy across diverse neurotrophic keratopathy etiologies and is increasingly considered earlier in disease progression.

SUMMARY

Corneal neurotization offers a promising, long-term solution for neurotrophic keratopathy by addressing the root cause of corneal anesthesia.

A Narrative Medicine Approach to Navigating Barriers to the Diagnosis of Pediatric Neurotrophic Keratopathy

OBJECTIVE

Neurotrophic keratopathy (NK) is a rare disease characterized by the loss of corneal innervation and increased vulnerability to injury. The diagnosis and treatment of NK can be challenging for pediatric patients and their caregivers. This study explores the experiences of caregivers navigating the diagnostic and treatment journey of pediatric patients with neurotrophic keratopathy.

DESIGN

This study is a qualitative study using semi-structured interviews.

SUBJECTS

Ten caregivers of pediatric patients with NK who had undergone corneal neurotization (CN) surgery.

METHODS

Caregivers were interviewed about their experiences related to the diagnostic process, treatment challenges, lifestyle changes, and the impact of CN surgery. Interviews were recorded, transcribed, and analyzed using an inductive-deductive approach to identify recurring themes.

MAIN OUTCOMES

Caregiver experiences and perceptions of diagnostic delays, information-seeking behaviors, lifestyle changes, and the effects of CN surgery on corneal health and quality of life.

RESULTS

Five key themes emerged from the analysis: (1) Delays in diagnosis due to insufficient specialist knowledge; (2) Caregivers' proactive efforts in seeking information; (3) Substantial lifestyle changes required by NK; (4) The impact of CN surgery on corneal health and quality of life; and (5) Variability in healthcare experiences, highlighting the need for effective communication. Caregivers expressed frustration with diagnostic delays and highlighted their reliance on external support networks.

CONCLUSIONS

This study illustrates the need for enhanced awareness among clinicians about NK and the benefits of narrative medicine in fostering caregiver-provider relationships. The challenges reported by families navigating NK inform strategies that may improve diagnosis and treatment of NK.

Long-Term Evaluation of Patients with Neurotrophic Keratopathy Undergoing Staged Keratoplasty After Corneal Neurotization

PURPOSE

Corneal neurotization (CN) is a novel, potentially curative surgical procedure for the treatment of neurothophic keratopathy (NK). Patients with severe NK can present with corneal opacification requiring optical keratoplasty, which would likely fail without a proper trophic support of corneal nerves in the recipient cornea.

METHODS

This is a pilot study on 4 patients undergoing keratoplasty after CN. Pre- and postoperative data at 12, 24 months and at the last follow-up were collected for the examination of (i) best corrected visual acuity (BCVA), (ii) slit lamp examination and photograph acquisition with and without fluorescein staining, (iii) corneal aesthesiometry, (iv) in vivo confocal microscopy of the central cornea. Neurophysiological study of the corneal reflex before corneal graft and at last follow up was performed.

RESULTS

Four female patients (47.25 ± 5.06 y.o.) underwent keratoplasty after CN (3 penetrating keratoplasty, 1 deep anterior lamellar keratoplasty). The mean interval between CN and keratoplasty was 22 (± 12) months. The mean graft survival time was 42 (± 25) months. Graft follow-up ranged from 72 to 132 months. At the final follow-up, BCVA was improved in 2 out of 4 patients. The mean corneal sensitivity was 11.9 ± 8.3 mm at last follow-up. In vivo confocal microscopy confirmed the presence of functioning nerves at the last follow-up in all patients. NK-related complications occurred in 3 eyes (2 persistent epithelial defect, 1 corneal melting). The former complication was successfully treated by autologous serum eye drops while the latter required repeated keratoplasty.

CONCLUSIONS

Keratoplasty is a viable strategy to improve visual acuity in patients with corneal opacity who underwent CN for the treatment of NK. Even in the presence of functioning corneal nerves before keratoplasty, surgeons should be aware of the increased rate of NK-related complications that could require the need for repeated procedure.

Corneal Neurotization for Neurotrophic Keratopathy: A Multicenter Experience

PURPOSE

Corneal neurotization is an emerging technique that offers potential for visual rehabilitation in neurotrophic keratopathy. This study reports on a multicenter experience and outcomes for both direct and indirect methods of corneal neurotization.

METHODS

Retrospective case series. Sixteen patients with neurotrophic keratopathy who underwent corneal neurotization across 5 centers in Australia and Israel were identified for inclusion. Corneal neurotization was performed via direct neurotization from the ipsilateral or contralateral supraorbital/supratrochlear nerve or by the use of an interpositional sural nerve graft. Change in corneal sensitivity (measured in millimeters by the Cochet-Bonnet aesthesiometer), visual acuity, and corneal health.

RESULTS

Over a mean follow-up period of 31.3 months (range: 3 months-8 years), mean corneal sensitivity improved from 3.6 mm (range: 0-25 mm) to 25.3 mm (range: 0-57 mm). Visual acuity improved on average from 20/380 to 20/260. Twelve of 16 patients (75.0%) improved in at least 2 out of the 3 main outcome measures. Nine patients (56.3%) showed an improvement in visual acuity; 13 (81.3%) showed an improvement in average corneal sensitivity; and 11 (68.8%) showed an improvement in corneal health. There were no intraoperative or postoperative complications.

CONCLUSIONS

Corneal neurotization is an emerging surgical treatment option for the management of neurotrophic keratopathy. With appropriate case selection, outcomes are favorable and complication rates are low, for a condition that is otherwise challenging to manage. Patients with severe neurotrophic keratopathy should be considered for this surgical treatment option.

Current perspectives and concerns in corneal neurotization

This study aimed to comprehensively explore the intricacies of corneal neurotization (CN) and the nuanced factors that set it apart from routine clinical practice, exerting a substantial influence on its success. A symbiotic relationship is evident between corneal innervation and ocular surface health. The loss of corneal innervation results in a potentially challenging corneal condition known as neurotrophic keratopathy (NK). The majority of treatments are primarily focused on preventing epithelial breakdown rather than addressing the underlying pathogenesis. Consequently, to address the impaired corneal sensation (underlying etiology), a novel surgical approach has emerged, namely CN, which involves transferring healthy sensory nerve axons to the affected cornea. This review offers valuable insights into the existing body of supporting evidence for CN, meticulously examining clinical studies, case reports, and experimental findings. The aim is to enhance our understanding of the effectiveness and potential outcomes associated with this innovative surgical technique. The exploration of innovative therapeutic avenues holds promise for revolutionizing the management of NK, offering a potentially permanent solution to a condition once deemed incurable and severely debilitating.

Single-Stage Bilateral Corneal Neurotization for Neurotrophic Keratopathy in Stüve-Wiedemann Syndrome: A Case Report and Literature Review

The authors report the surgical management and outcomes of neurotrophic keratopathy in two patients with Stüve-Weidemann syndrome who underwent single-stage bilateral corneal neurotization. Both patients experienced improvement in corneal sensation based on Cochet-Bonnet aesthesiometry measurements or cotton tip testing in addition to clinical improvement in ocular surface health. [J Pediatr Ophthalmol Strabismus. 2024;61(5):e54-e58.].

Corneal Neurotization: Essentials for The Facial Paralysis Surgeon

Deficits in corneal innervation lead to neurotrophic keratopathy (NK). NK is frequently associated with facial palsy, and corneal damage can be accelerated by facial palsy deficits. Corneal nerves are important regulators of limbal stem cells, which play a critical role in epithelial maintenance and healing. Nonsurgical treatments of NK have undergone recent innovation, and growth factors implicated in corneal epithelial renewal are a promising therapeutic avenue. However, surgical intervention with corneal neurotization (CN) remains the only definitive treatment of NK. CN involves the transfer of unaffected sensory donor nerve branches to the affected cornea, and a variety of donor nerves and approaches have been described. CN can be performed in a direct or indirect manner; employ the supraorbital, supratrochlear, infraorbital, or great auricular nerves; and utilize autograft, allograft, or nerve transfer alone. Unfortunately, comparative studies of these factors are limited due to the procedure's novelty and varied recovery timelines after CN. Regardless of the chosen approach, CN has been shown to be a safe and effective procedure to restore corneal sensation and improve visual acuity in patients with NK.

Neurotrophic keratopathy: Clinical presentation and outcomes in 354 eyes in a community-based population

PURPOSE

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.

Viral Keratitis, Surgical Intervention in Viral Keratitis, Challenges in Diagnosis and Treatment of Viral Keratitis, HSV, HZV

Viral keratitis is a significant cause of ocular morbidity and visual impairment worldwide. In recent years, there has been a growing understanding of the pathogenesis, clinical manifestations, and diagnostic modalities for viral keratitis. The most common viral pathogens associated with this condition are adenovirus, herpes simplex (HSV), and varicella-zoster virus (VZV). However, emerging viruses such as cytomegalovirus (CMV), Epstein-Barr virus (EBV), and Vaccinia virus can also cause keratitis. Non-surgical interventions are the mainstay of treatment for viral keratitis. Antiviral agents such as Acyclovir, Ganciclovir, and trifluridine have effectively reduced viral replication and improved clinical outcomes. Additionally, adjunctive measures such as lubrication, corticosteroids, and immunomodulatory agents have alleviated symptoms by reducing inflammation and facilitating tissue repair. Despite these conservative approaches, some cases of viral keratitis may progress to severe forms, leading to corneal scarring, thinning, or perforation. In such instances, surgical intervention becomes necessary to restore corneal integrity and visual function. This review article aims to provide an overview of the current perspectives and surgical interventions in managing viral keratitis. The choice of surgical technique depends on the extent and severity of corneal involvement. As highlighted in this article, on-going research and advancements in surgical interventions hold promise for further improving outcomes in patients with viral keratitis.

Clinical outcomes of corneal neurotization using sural nerve graft in neurotrophic keratopathy

OBJECTIVE

To evaluate the efficacy of corneal neurotisation using sural nerve graft coaptation of the contralateral supratrochlear nerve in unilateral neurotrophic keratopathy and corneal anesthesia. Corneal neuralization has emerged as a potential option in the treatment of neurotropic keratopathy, however not free from the predicament. We evaluated the long-term outcome of corneal neurotisation in the treatment of unresponsive unilateral neurotropic keratopathy using surgical variations to mimic and expedient the surgical procedure.

METHODS

A Prospective interventional study involving patients with unilateral neurotrophic keratopathy (NK) who did not respond to medical measures was conducted. The study parameters evaluated were best-corrected visual acuity improvement, ocular surface evaluation parameters [tear break-up time (TBUT), Schirmer's 1, and ocular surface staining scores (corneal and conjunctival staining)], central corneal sensation (Cochet Bonnet esthesiometer), sub-basal nerve fiber length (SBNFL), and sub-basal nerve fiber density (SBNFD) determined by central confocal microscopy at recruitment and during follow-up at 1-month, 3-month, 6-month, 9-month and 12-month respectively, following corneal neurotization.

RESULTS

Eleven eyes of 11 patients with unilateral neurotrophic keratopathy (NK) who underwent corneal neurotisation were studied. The mean follow-up was 10.09±2.31months (range, 6-12). Mean best corrected visual acuity in log MAR at baseline, 1.35±0.52 improved significantly to 1.06±0.76 (P = 0.012) at 3 months and continued to 0.55±0.60 (P = 0.027) at 12 months. There was a significant reduction in NK grade severity and improvement in the ocular surface as early as 1 month, and central corneal sensations (P = 0.024) as soon as 3 months. Mean corneal SBNF improved from 3.12±1.84 mm/mm2 to 4.49±1.88 at 1 month (P = 0.008), 13.31±3.61 mm/mm2 (P = 0.028) at 12 months. Mean central corneal SBNFD evident at 6 months was 1.83±2.54no/mm2 (P = 0.018) and 4.90±3.12no/mm2 (P = 0.028) at 12 months.

CONCLUSION

This study substantiates the routine practice of corneal neurotisation by simplifying the intricacies observed during the procedure.

Neurotrophic keratopathy: An updated understanding

PURPOSE

To propose an updated definition and staging system for neurotrophic keratopathy (NK) and provide consensus on diagnosis and treatment.

METHODS

A study group was convened to review the data pertinent to NK using a modified nominal group process. They proposed an updated definition for NK and a new 6-step staging system (Neurotrophic Keratopathy Study Group [NKSG] Classification) that can be used in conjunction with the different treatment options available currently or in the future.

RESULTS

NK is defined as the dysfunction of corneal innervation that results in dysregulation of corneal and/or cellular function. It is characterized by loss of corneal sensation and neuronal homeostasis, leading to eventual corneal epithelial breakdown and ultimately keratolysis if untreated. The NKSG classification emphasizes verifying corneal sensation early and distinguishes different epithelial and stromal aspects of NK with the following stages: stage 1 (altered sensation without keratopathy), stage 2 (epitheliopathy/punctate epithelial keratopathy [PEK] without stromal haze), stage 3 (persistent/recurrent epithelial defects without stromal haze), stage 4 (epitheliopathy/PEK or persistent/recurrent epithelial defects with stromal haze), stage 5 (persistent/recurrent epithelial defect with corneal ulceration), and stage 6 (corneal perforation). Treatment consists of a variety of modalities (both indirect and direct).

CONCLUSIONS

This updated definition and staging system will provide clinicians with the necessary information to diagnose and treat NK at an early stage before it becomes a sight-threatening disorder. It also provides a framework for evaluating current and future treatment options at distinct stages of the disease.

Evaluation of Corneal Nerve Regeneration After Minimally Invasive Corneal Neurotization

PURPOSE

To evaluate the corneal nerve regeneration after minimally invasive corneal neurotization (MICN) and to further clarify the recovery patterns of sensory and trophic functions of the corneal nerves.

DESIGN

A retrospective cohort study based in the Shanghai Ninth People's Hospital.

METHODS

Eighteen patients (18 eyes) who underwent MICN for neurotrophic keratopathy due to intracranial surgery was conducted to analyze their follow-up data at 6, 12, 18, and 24 months after surgery.

RESULTS

At 12 months postoperatively, the growth of the central and peripheral corneal nerve fiber density (CNFD) was 11.47±8.56 and 14.73±8.08 n/mm 2 with subsequent improvement slowing down, and the patient's corneal epithelium defect was healed ahead of the accomplishment of corneal nerve regeneration. The number of dendritic cells also reached its peak. At 18 months postoperatively, the recovery of central and peripheral corneal sensation was 37.22±23.06 mm and 39.38±18.08 mm with no subsequent improvement, and the growth of the central and peripheral corneal nerve branch density (CNBD) was 29.69±11.05 and 43.75±1.41 n/mm 2 , with a positive and significant correlation between corneal sensation and CNBD (at central r =0.632, P <0.005; at peripheral r =0.645, P <0.005). At 24 months postoperatively, mean CNFD, CNBD, and corneal sensation recovered significantly compared with preoperative, but a few patients' corneal sensation recovered insignificantly with good CNFD recovery and poor CNBD recovery.

CONCLUSIONS

After MICN, the trophic function of the corneal nerve recovers before the sensory function, and in particular, the recovery of sensation is based on the coexistence of the corneal nerve trunk and branches.

Bilateral Corneal Neurotization for Ramos-Arroyo Syndrome and Developmental Neurotrophic Keratopathy: Case Report and Literature Review

PURPOSE

The purpose of this study was to report the use of bilateral corneal neurotization for neurotrophic keratitis in the setting of Ramos-Arroyo syndrome.

METHODS

The case report and surgical technique are described in detail in this article, as well as a review of the literature on corneal neurotization for congenital corneal anesthesia.

RESULTS

We report a 17-year-old patient who underwent bilateral corneal neurotization for neurotrophic keratitis secondary to corneal anesthesia in Ramos-Arroyo syndrome. Corneal neurotization was performed with great auricular nerve transfers extended by sural nerve autografts.

CONCLUSIONS

We present the treatment of neurotrophic keratopathy with corneal neurotization in a patient with Ramos-Arroyo syndrome. We describe how bilateral corneal neurotization using the great auricular nerve technique is a safe and effective procedure for patients with congenital/developmental corneal anesthesia.

Minimally invasive, indirect corneal neurotization using an ipsilateral sural nerve graft for early neurotrophic keratopathy

Purpose

Neurotrophic keratopathy is a degenerative disease characterized by damage to the corneal nerves leading to corneal hypoesthesia and anaesthesia. The resultant progressive visual deterioration is refractory to existing conventional treatment options. Corneal neurotization is a novel and effective surgical procedure that directly targets the underlying pathology of nerve loss by stimulating new corneal nerve growth. This study reports the outcomes and the pre- and postoperative in vivo confocal microscopy findings of the first published Australian case of indirect, minimally invasive, corneal neurotization using an ipsilateral sural nerve autograft.

Observations

An 11-year-old boy developed corneal hypoesthesia in the left eye following surgical debulking of a cerebellopontine angle arachnoid cyst. He was diagnosed with Mackie Stage 1 neurotrophic keratopathy. Due to his hypoesthesia, he had developed recurrent microbial keratitis and corneal ulceration secondary to foreign bodies sustained during contact sports. At presentation, he reported photophobia and dry eye symptoms, corrected-distance visual acuity was 6/18, Cochet-Bonnet aesthesiometer demonstrated reduced corneal sensation (5–15mm), Schirmer's I test was 15mm, and in vivo confocal microscopy showed a complete absence of a subepithelial corneal plexus. He underwent indirect, minimally invasive, corneal neurotization using the ipsilateral supratrochlear nerve and a sural nerve autograft. Subjective improvement in corneal sensation was noticed by the patient at 2 months. Objective improvement, measured on Cochet-Bonnet aesthesiometer, was first observed at 6 months with steady stepwise improvement to 20–35mm at 21 months. Importantly, due to the increase in corneal sensation, the patient did not develop any further corneal complications. At 12 months, dry eye symptoms resolved and Schirmer's I test improved to 30mm. At 15 months, corrected-distance visual acuity improved to 6/5 and in vivo confocal microscopy demonstrated evidence of corneal reinnervation with nerves running through the subepithelial space surrounded by healthy and active keratocytes.

Conclusions and importance

Corneal neurotization represents an exciting development in the armamentarium for the treatment of neurotrophic keratopathy and can be considered for younger patients with early-stage disease.

Neurotization of the human cornea - A comprehensive review and an interim report

We present a comprehensive review of existing literature on surgical corneal neurotization (SCN) as a treatment modality for neurotrophic keratopathy (NK) with an interim report of seven cases where SCN was performed using the indirect approach and followed up till 18 months postoperatively to look for improvement in ocular surface, corneal sensations, and nerve regeneration by using in vivo confocal microscopy (IVCM). A literature search was performed for publications with keywords “corneal nerves,” “neurotization,” “esthesiometry,” “corneal anesthesia,” and “neurotrophic keratopathy.” All literature available till December 31, 2020 was reviewed and included to describe NK and its management options, particularly SCN. NK is associated with absent or reduced corneal sensations and is managed using a step-ladder algorithm ranging from medical management for symptomatic relief to surgical corneal neurotization. Both direct and indirect approaches of SCN have a favorable outcome with reduced surgical morbidity in the indirect approach using sural nerve graft. Post neurotization, corneal sensation recovery may take up to 3–6 months, while nerve regeneration on confocal microscopy can take as long as 6 months–1 year.

Corneal Neurotization: A Meta-analysis of Outcomes and Patient Selection Factors

BACKGROUND

Corneal neurotization describes reinnervation of the anesthetic or severely hypoesthetic cornea with a healthy local nerve or graft. Preliminary evidence has shown corneal neurotization to improve corneal sensation, visual acuity, and ocular surface health. Factors that improve patient selection and lead to better neurotization outcomes have yet to be elucidated, limiting ability to optimize perioperative decision-making guidelines.

METHODS

A systematic review with meta-analysis was performed of the MEDLINE and Embase databases using variations of "corneal," "nerve transfer," "neurotization," and "neurotization." The primary outcomes of interest were corrected visual acuity, NK Mackie stage, and central corneal sensation. Regression analyses were performed to identify the effects of surgical technique, duration of denervation, patient age, and etiology of corneal pathology on neurotization outcomes.

RESULTS

Seventeen studies were included. Corneal neurotization resulted in significant improvement in NK Mackie stage (0.84 vs 2.46, P < 0.001), visual acuity (logarithm of minimum angle of resolution scale: 0.98 vs 1.36, P < 0.001), and corneal sensation (44.5 vs 0.7, P < 0.001). Nerve grafting was associated with greater corneal sensation improvement than nerve transfer (47.7 ± 16.0 vs 35.4 ± 18.76, P = 0.03). Denervation duration was predictive of preneurotization visual acuity (logarithm of minimum angle of resolution scale; R2 = 0.25, P = 0.001), and older age (ß = 0.30, P = 0.03) and acquired etiology (ß = 0.30, P = 0.03) were predictive of improved visual acuity.

CONCLUSIONS

Corneal neurotization provides significant clinical improvement in visual acuity, NK Mackie staging, and corneal sensation in patients who experience NK. Both nerve grafting and nerve transfer are likely to yield similar levels of benefit and ideally should be performed early to limit denervation time.

Minimally Invasive Corneal Neurotization Provides Sensory Function, Protects Against Recurrent Ulceration, and Improves Visual Acuity

PURPOSE

To measure sensory recovery after minimally invasive corneal neurotization, and to identify and quantify the extent to which patient and technical factors influence sensory recovery, ulceration rate, and visual outcomes.

DESIGN

Retrospective case series.

METHODS

This study included 23 patients with neurotrophic keratopathy who underwent indirect corneal neurotization. The primary outcome measure was corneal sensitivity with Cochet-Bonnet aesthesiometry (CBA), and the secondary outcome measure was epithelial breakdown.

RESULTS

Over a 7-year period, 28 eyes of 23 patients (mean age, 15.6 ± 13.6 years) were included in the study. The CBA measurements improved from 3.5 ± 9.1 mm at baseline to 44.1 ± 18.2 mm at 24 months after surgery (P < .001). Maximum CBA was reached after 11.1 ± 6.2 months (median, 9 months). Compared to eyes neurotized with a contralateral donor nerve, eyes with an ipsilateral donor nerve achieved a higher mean CBA (36.0 ± 10.9 vs 10.4 ± 14.0 mm, P = .001) at 3 months. Both the number of fascicles (Spearman correlation coefficient, r_s -0.474, P = .11) and insertions (r_s -0.458, P = .014) negatively correlated with the final CBA. Nine eyes (32.1%) experienced at least 1 episode of epithelial breakdown after surgery. Visual acuity improved in the neurotized corneas from logMAR 0.57 ± 0.79 at baseline to 0.39 ± 0.66 at 12 months (P = .043).

CONCLUSIONS

Corneal sensation improves over time after corneal neurotization. There is resultant improvement in visual acuity and protection against epithelial breakdown. It is important to maximize sensory recovery to protect against recurrent ulceration.

Neurotrophic Keratitis in a Pediatric Patient With Goldenhar Syndrome and Trigeminal Aplasia Successfully Treated by Corneal Neurotization

Herein, the authors report an unusual case of a 6-year-old boy with right-sided Goldenhar syndrome and trigeminal nerve aplasia who developed neurotrophic keratopathy (NK). Despite the use of therapeutic contact lenses and multiple temporary tarsorrhaphy, NK worsened showing a central corneal scar, neovascularization, and significant stromal thinning, with risk of corneal perforation. Cochet-Bonnet esthesiometry revealed complete corneal anesthesia. To minimize additional corneal complications, the patient underwent indirect corneal neurotization by a sural nerve autograft anastomosed to the contralateral supratrochlear nerve. At 24-month follow up, no epithelial defects, complications, or recurrence were observed. Significant improvements in corneal sensitivity with esthesiometry score of 20 mm and reflex blinking were achieved. This case highlights corneal anesthesia should be suspected among Goldenhar syndrome ophthalmologic abnormalities and monitored before corneal changes become irreversible. Since corneal neurotization can successfully improve corneal sensation, it could be considered as an early therapeutic option to avoid refractory NK.

Abnormal corneal nerve morphology and brain volume in patients with schizophrenia

Neurodevelopmental and neurodegenerative pathology occur in Schizophrenia. This study compared the utility of corneal confocal microscopy (CCM), an ophthalmic imaging technique with MRI brain volumetry in quantifying neuronal pathology and its relationship to cognitive dysfunction and symptom severity in schizophrenia. Thirty-six subjects with schizophrenia and 26 controls underwent assessment of cognitive function, symptom severity, CCM and MRI brain volumetry. Subjects with schizophrenia had lower cognitive function (P ≤ 0.01), corneal nerve fiber density (CNFD), length (CNFL), branch density (CNBD), CNBD:CNFD ratio (P < 0.0001) and cingulate gyrus volume (P < 0.05) but comparable volume of whole brain (P = 0.61), cortical gray matter (P = 0.99), ventricle (P = 0.47), hippocampus (P = 0.10) and amygdala (P = 0.68). Corneal nerve measures and cingulate gyrus volume showed no association with symptom severity (P = 0.35–0.86 and P = 0.50) or cognitive function (P = 0.35–0.86 and P = 0.49). Corneal nerve measures were not associated with metabolic syndrome (P = 0.61–0.64) or diabetes (P = 0.057–0.54). The area under the ROC curve distinguishing subjects with schizophrenia from controls was 88% for CNFL, 84% for CNBD and CNBD:CNFD ratio, 79% for CNFD and 73% for the cingulate gyrus volume. This study has identified a reduction in corneal nerve fibers and cingulate gyrus volume in schizophrenia, but no association with symptom severity or cognitive dysfunction. Corneal nerve loss identified using CCM may act as a rapid non-invasive surrogate marker of neurodegeneration in patients with schizophrenia.

Modified Gundersen Flap Using Inferior Palpebral-Bulbar Conjunctiva

PURPOSE

The purpose of this article was to describe a modification to the traditional Gundersen flap technique that expands eligible eyes to include those with severe conjunctival scarring and to report results from a clinical case.

METHODS

A 68-year-old woman with a history of herpes simplex keratitis, multiple failed penetrating keratoplasties, lagophthalmos, persistent epithelial defect, and low visual potential in the left eye presented for the evaluation of a Gundersen flap. Severe superior bulbar conjunctival scarring precluded a traditional approach. A modified Gundersen flap technique using a contiguous flap of inferior palpebral-bulbar conjunctiva extending from the inferior tarsal border to the limbus was devised and performed.

RESULTS

The modified Gundersen flap technique successfully stabilized the ocular surface, obviating the need for a cosmetically disfiguring permanent tarsorrhaphy or an evisceration.

CONCLUSIONS

This modified Gundersen flap technique expands the indications to eyes with severe conjunctival scarring and can be offered in eyes with previous trabeculectomies, glaucoma drainage implants, and scleral buckles, which were previously excluded from the globe-preserving option.

Corneal Neurotization via Dual Nerve Autografting

Corneal neurotization is a fast-evolving surgical procedure for sensory reinnervation in neurotrophic keratopathy. After neurotization, prior reports document return of corneal sensation on average 8 months after surgery with 38 mm of sensation gain measured via cochet bonnet esthesiometer testing. Here, the authors describe a dual nerve grafting approach via simultaneous parallel sural nerve grafts from both the supratrochelar and supraorbital nerves to the affected contralateral cornea with return of sensation by postoperative week 11.

Clinical Outcomes and Patient Satisfaction After Corneal Neurotization

PURPOSE

The aim of this study was to assess clinical outcomes of corneal neurotization (CN) and determine patient perception of postoperative results.

METHODS

This was a retrospective study involving 29 eyes in 28 patients who underwent CN. Chart review data included demographic and clinical history; ophthalmic examination including visual acuity, ocular surface quality, and corneal sensation; surgical technique; and postoperative course. Subjective self-reported patient outcomes of surgical success were also assessed. Only eyes with at least 6 months of follow-up were included in the statistical analysis.

RESULTS

A total of 24 eyes and 23 patients were included in statistical analyses. The median postoperative follow-up time was 12.2 months (interquartile range 10.9-18.5 mo). Twenty-three eyes (92%) achieved improvement in ocular surface quality. Eleven of 13 (85%) demonstrated healing of persistent epithelial defects at their last follow-up. Patients gained a median of 2.3 cm in Cochet-Bonnet esthesiometry measurements of sensation. No significant difference was found between preoperative and postoperative visual acuity. All 17 patients who provided self-assessment of their surgical outcome indicated they would undergo CN again if given the choice. Most of the patients reported that the postoperative pain was tolerable, with a median pain score of 3.0 on a 10-point scale (interquartile range 0.0-4.0). Sixteen patients (94%) reported full or partial return of skin sensation along the donor nerve distribution.

CONCLUSIONS

CN provides improvement in corneal health and sensibility, with high patient satisfaction and minimal postoperative pain and morbidity.

Expert consensus on the identification, diagnosis, and treatment of neurotrophic keratopathy

Background

Neurotrophic keratopathy (NK) is a relatively uncommon, underdiagnosed degenerative corneal disease that is caused by damage to the ophthalmic branch of the trigeminal nerve by conditions such as herpes simplex or zoster keratitis, intracranial space-occupying lesions, diabetes, or neurosurgical procedures. Over time, epithelial breakdown, corneal ulceration, corneal melting (thinning), perforation, and loss of vision may occur. The best opportunity to reverse ocular surface damage is in the earliest stage of NK. However, patients typically experience few symptoms and diagnosis is often delayed. Increased awareness of the causes of NK, consensus on when and how to screen for NK, and recommendations for how to treat NK are needed.

Methods

An 11-member expert panel used a validated methodology (a RAND/UCLA modified Delphi panel) to develop consensus on when to screen for and how best to diagnose and treat NK. Clinicians reviewed literature on the diagnosis and management of NK then rated a detailed set of 735 scenarios. In 646 scenarios, panelists rated whether a test of corneal sensitivity was warranted; in 20 scenarios, they considered the adequacy of specific tests and examinations to diagnose and stage NK; and in 69 scenarios, they rated the appropriateness of treatments for NK. Panelist ratings were used to develop clinical recommendations.

Results

There was agreement on 94% of scenarios. Based on this consensus, we present distinct circumstances when we strongly recommend or may consider a test for corneal sensitivity. We also present recommendations on the diagnostic tests to be performed in patients in whom NK is suspected and treatment options for NK.

Conclusions

These expert recommendations should be validated with clinical data. The recommendations represent the consensus of experts, are informed by published literature and experience, and may improve outcomes by helping improve diagnosis and treatment of patients with NK.

Herpes Zoster: A Brief Definitive Review

ABSTRACT

This brief definitive review of herpes zoster (HZ) will cover the current state of knowledge and questions that remain to be answered regarding HZ in general and HZ ophthalmicus in particular. A question-and-answer format will be used to address various important topics related to this common and serious disease. Questions to be addressed relate to common misconceptions, contagiousness of infection, unknowns regarding pathogenesis, rising incidence, risk factors and complications, relationship with temporal arteritis, vaccination, and current and future antiviral treatment. In addition, the importance of the Zoster Eye Disease Study to determine the efficacy of suppressive valacyclovir treatment in preventing complications of HZ ophthalmicus and the need to support enrollment will be discussed.

Corneal and Facial Sensory Neurotization in Trigeminal Anesthesia

Trigeminal anesthesia may yield blindness and facial disfigurement, secondary to neurotrophic keratopathy and trigeminal trophic syndrome. This article summarizes contemporary medical and emerging surgical approaches for the therapeutic management of this rare and devastating disease state.

Seeing through the evidence for corneal neurotization

PURPOSE OF REVIEW

Trigeminal anesthesia causes neurotrophic keratopathy, which may yield facial disfigurement and corneal blindness.

RECENT FINDINGS

We summarize approaches and evidence for corneal neurotization.

SUMMARY

Regional sensory nerve transfer appears safe and effective for therapeutic management of neurotrophic keratopathy. Prospective randomized clinical trials are necessary to confirm the utility of corneal neurotization.

Assessment of Tactile Sensitivity Threshold Using Cochet-Bonnet Esthesiometer and Semmes-Weinstein Monofilaments and Their Use in Corneal Neurotization

PURPOSE

Although the Cochet-Bonnet esthesiometer (CBE) measures corneal sensitivity, it has heretofore only been tested on the index pulp. Tactile skin sensitivity thresholds are measured with Semmes-Weinstein monofilaments (SWM). This study measured skin sensitivity thresholds in healthy individuals using CBE and SWM, and compared both instruments in territories involved in corneal neurotization.

METHODS

Overall, 27 healthy individuals were tested by a single examiner at 9 territories on the face, neck, forearm, and leg, using 20-thread SWM and CBE with a diameter of 0.12 mm. Both sides were tested. Thresholds were compared for both instruments and between the different territories using Bayesian methods.

RESULTS

Mean sensitivity levels for SWM ranged from 0.010 to 1.128 g, while mean sensitivity levels for CBE ranged from 0.006 to 0.122 g. Thresholds measured with SWM were significantly higher than with CBE. Both instruments demonstrated higher thresholds in the leg territory than the forearm. However, the forearm presented higher thresholds than the head territories. No significant differences were found between the head territories themselves. Overall, right-side territories exhibited lower thresholds than left-side territories.

CONCLUSIONS

We have reported the first mapping of skin sensitivity thresholds using CBE. Thresholds measured with CBE and SWM were coherent. The use of CBE on the skin is particularly relevant to the field of corneal neurotization.

Corneal neurotization for neurotrophic keratopathy: Review of surgical techniques and outcomes

Neurotrophic keratopathy is a degenerative disease in which damage to the corneal nerves leads to corneal hypoesthesia. Injuries to neurotrophic corneas are notoriously difficult to treat and have traditionally been approached with supportive management. However, recent progress in the field of corneal neurotization has given new direction for addressing nerve loss directly by stimulating new nerve growth onto the cornea from nearby sensory nerves transferred to the perilimbal region. Herein, we review the surgical techniques utilized in corneal neurotization, including direct transfers and the use of nerve grafts. Considerations in surgical approach, as well as factors that influence prognosis and outcomes of the surgical intervention are also discussed.

Corneal Neurotization for Postherpetic Neurotrophic Keratopathy: Initial Experience and Clinical Outcomes

PURPOSE

To assess early outcomes of corneal neurotization for postherpetic neurotrophic keratopathy (NK).

METHODS

Retrospective analysis of patients who underwent corneal neurotization for postherpetic NK by a single experienced oculoplastic surgeon was performed. Collected data included stage and etiology of NK as well as comorbidities, prior treatment history, neurotization technique, donor nerve site, preoperative and postoperative examination findings (i.e., ocular surface quality, corneal clarity, corneal sensation by Cochet-Bonnet esthesiometry, and visual acuity [VA]), and follow-up duration. Differences between preoperative and postoperative values were analyzed by Wilcoxon signed-rank test.

RESULTS

Of 23 adult patients who underwent corneal neurotization, 3 (13%) had history of herpes simplex keratitis and/or endotheliitis, and 4 (17%) had history of herpes zoster ophthalmicus. One patient with herpes zoster ophthalmicus was excluded due to inadequate follow-up duration. Of the 6 patients included in the study, 3 (50%) had Mackie stage 1 disease, 1 (17%) had stage 2, and 2 (33%) had stage 3 with impending perforation, but all had markedly diminished corneal sensation, with a median denervation time of 11.8 months (interquartile range [IQR] 9.4-29.2 months). Following neurotization, median corneal sensation improved significantly from 1.6 cm (interquartile range 0.0-1.9 cm) to 3.6 cm (IQR 3.0-5.6 cm, p = 0.028), with 1 patient achieving full sensation by postoperative month 5. All patients with a persistent epithelial defect preoperatively showed complete corneal healing by their last follow-up visit. VA also improved postoperatively in all patients (p = 0.028). Median follow-up duration was 11.3 months (interquartile range 9.6-17.9 months).

CONCLUSIONS

Corneal neurotization can successfully reinnervate corneas previously devitalized by herpetic disease and halt the progressive nature of postherpetic NK. If utilized appropriately and early in the disease process, neurotization may reduce morbidity and maximize visual potential in postherpetic NK.

Outcomes of corneal neurotisation using processed nerve allografts: a multicentre case series

Background

Corneal neurotisation is a rapidly evolving procedure treating neurotrophic keratopathy. The variety of surgical techniques used and corresponding outcomes after corneal neurotisation are not well understood. This study describes the techniques and outcomes in the largest case series of corneal neurotisation using processed nerve allografts to date.

Methods

This is a retrospective case series of patients who underwent corneal neurotisation with human cadaveric processed nerve allografts. All patients had preoperative and postoperative description of best corrected visual acuity and measurement of corneal sensation. Comparative studies after stratification of techniques were performed.

Results

A total of 17 patients were identified. The cause of corneal anaesthesia was prior infection in eight cases, trigeminal nerve palsy in eight cases and ocular trauma in one case. There were no intraoperative or postoperative complications. Following neurotisation surgery, the time to first gain of corneal sensation and maximal gain of sensation occurred at a mean of 3.7 months (range 1–8 months) and 6.6 months (range 3–15 months), respectively. The mean preoperative and postoperative corneal sensation as measured by Cochet-Bonnet aesthesiometry was 0.36 cm (range 0–3.2 cm) and 4.42 cm (range 0–6 cm), respectively (p<0.01). Visual acuity was unchanged after neurotisation. There were no statistical differences in outcomes based on end-to-end versus end-to-side coaptations, donor nerve selection or laterality of donor nerve.

Conclusion

Corneal neurotisation with processed nerve allografts is a safe and effective procedure. This study provides further evidence for the use of processed nerve allografts for corneal neurotisation.

Corneal Neurotization and Novel Medical Therapies for Neurotrophic Keratopathy

Purpose of Review

Neurotrophic keratopathy (NK) is a degenerative corneal disease characterized by decreased corneal sensibility and impaired corneal healing. In this article, we review surgical techniques for corneal neurotization (CN) and novel medical therapies for the treatment of NK.

Recent Findings

In recent decades, there has been a paradigm shift in the treatment strategies for NK. New minimally invasive direct and indirect CN approaches have demonstrated efficacy at improving best-corrected visual acuity and central corneal sensation while decreasing surgical morbidity. In addition, several targeted medical therapies, such as recombinant human nerve growth factor (rhNGF), regenerating agents (RGTA), and nicergoline, have shown promise in improving corneal epithelial healing. Of these options, cenegermin (Oxervate®, Dompé), a topical biologic medication, has emerged as an approved medical treatment for moderate to severe NK.

Summary

NK is a challenging condition caused by alterations in corneal nerves, leading to impairment in sensory and trophic function with subsequent breakdown of the cornea. Conventional therapy for NK depends on the severity of disease and focuses primarily on protecting the ocular surface. In recent years, numerous CN techniques and novel medical treatments have been developed that aim to restore proper corneal innervation and promote ocular surface healing. Further studies are needed to better understand the long-term efficacy of these treatment options, their target populations, and the potential synergistic efficacy of combined medical and surgical treatments.