Minimally Invasive Corneal Neurotization With Acellular Nerve Allograft: Surgical Technique and Clinical Outcomes

Corneal Neurotization: Paving the Path to Reinnervation

Neurotrophic keratopathy (NK), a degenerative corneal disease characterized by the loss of innervation to the cornea, has historically required long-term supportive treatment with a poor prognosis for rehabilitation. Corneal neurotization restores corneal sensation, permanently addressing the underlying pathophysiology of NK. Surgical approaches to corneal neurotization are expanding and undergoing refinement as more centers perform this intervention. This article describes the indications, surgical approaches, outcomes, and future directions of corneal neurotization.

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.

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.

Insights on the Choice and Preparation of the Donor Nerve in Corneal Neurotization for Neurotrophic Keratopathy: A Narrative Review

The article introduces neurotrophic keratopathy (NK), a condition resulting from corneal denervation due to various causes of trigeminal nerve dysfunctions. Surgical techniques for corneal neurotization (CN) have evolved, aiming to restore corneal sensitivity. Initially proposed in 1972, modern approaches offer less invasive options. CN can be performed through a direct approach (DCN) directly suturing a sensitive nerve to the affected cornea or indirectly (ICN) through a nerve auto/allograft. Surgical success relies on meticulous donor nerve selection and preparation, often involving multidisciplinary teams. A PubMed research and review of the relevant literature was conducted regarding the surgical approach, emphasizing surgical techniques and the choice of the donor nerve. The latter considers factors like sensory integrity and proximity to the cornea. The most used are the contralateral or ipsilateral supratrochlear (STN), and the supraorbital (SON) and great auricular (GAN) nerves. Regarding the choice of grafts, the most used in the literature are the sural (SN), the lateral antebrachial cutaneous nerve (LABCN), and the GAN nerves. Another promising option is represented by allografts (acellularized nerves from cadavers). The significance of sensory recovery and factors influencing surgical outcomes, including nerve caliber matching and axonal regeneration, are discussed. Future directions emphasize less invasive techniques and the potential of acellular nerve allografts. In conclusion, CN represents a promising avenue in the treatment of NK, offering tailored approaches based on patient history and surgical expertise, with new emerging techniques warranting further exploration through basic science refinements and clinical trials.

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.

Corneal Neurotization: Preoperative Patient Workup and Surgical Decision-making

Background

The use of sensory nerve transfers to the anesthetic cornea has transformed the treatment of neurotrophic keratopathy by restoring ocular surface sensation and activating dysfunctional epithelial repair mechanisms. However, despite numerous reports on surgical techniques, there is a scarcity of information on the interdisciplinary management, preoperative assessment, and surgical decision-making, which are equally critical to treatment success.

Methods

This Special Topic presents a standardized, interdisciplinary preoperative workup based on our 10-year experience with corneal neurotization in 32 eyes of patients with neurotrophic keratopathy.

Results

Our assessment includes a medical history review, ophthalmic evaluation, and systematic facial sensory donor nerve mapping for light touch and pain modalities. This approach enables evidence-based patient selection, optimal surgery timing, and suitable donor nerve identification, including backup options.

Conclusions

Based on a decade-long experience, this special topic highlights the importance of interdisciplinary collaboration and provides a practical roadmap for optimizing patient selection and surgical decision-making in patients undergoing corneal neurotization.

Corneal Neurotization—Indications, Surgical Techniques and Outcomes

Corneal neurotization is a promising surgical approach for the treatment of moderate to severe neurotrophic keratopathy. This technique aims to restore corneal sensation by transferring healthy nerves, either directly or via a conduit, to the anesthetic cornea. This review provides a report on the current state of development, evidence, and experience in the field. We summarize the data available from clinical reports and case series, placing an emphasis on the diversity of the surgical techniques reported. While these data are encouraging, they also highlight the need for a consensus in reporting outcomes and highlight how the next step will involve validating putative outcome parameters when researching and reporting corneal neurotization surgery.

Corneal neurotization in the management of neurotrophic keratopathy: A review of the literature

Neurotrophic keratopathy (NK) is a rare degenerative disease in which damage to the corneal nerves leads to corneal hypoesthesia or anesthesia. Neurotrophic corneal ulcers are notoriously difficult to treat and can lead to blindness. Corneal neurotization (CN) is a recent surgical technique aimed at restoring corneal sensation and may offer a definitive treatment in the wake of NK. Herein, we review the surgical techniques utilized in direct and indirect CN. Technical considerations, outcomes, current limitations and future perspectives are also discussed. This article highlights the key points of this promising procedure and biological aspects that will help provide the best treatment options for patients with severe NK.

A Surgeon's Armamentarium for Ocular Management in Facial Paralysis: A Comprehensive Review

OBJECTIVE

To review the current management paradigm of the eye in patients with facial paralysis.

METHODS

A PubMed and Cochrane search was done with no date restrictions for English-language literature on facial synkinesis. The search terms used were "ocular," "facial," "synkinesis," "palsy," "neurotization," and various combinations of the terms. A total of 65 articles were included.

RESULTS

Facial paralysis may result in devastating ocular sequelae. Therefore, assessment of the eye in facial paralysis is a critical component of patient management. Although the management should be individualized to the patient, the primary objective should include an ophthalmologic evaluation to implement measures to protect the ocular surface and preserve visual acuity. The degree of facial paralysis, lacrimal secretion, corneal sensation, and position of the eyelids should be assessed thoroughly. Patients with the anticipated recovery of facial nerve function may respond to more conservative temporizing measures to protect the ocular surface. Conversely, patients with expected prolonged paralysis should be appropriately identified as they will benefit from surgical reconstruction and rehabilitation of the periorbital complex. The majority of reconstructive measures within a facial surgeon's armamentarium augment coverage of the eye but are unable to restore blink. Eyelid reanimation restores the esthetic proportionality of the eye with blinking and reestablishes protective functions necessary for ocular preservation and function.

CONCLUSIONS

Ocular preservation is the primary priority in the initial management of the patient with facial paralysis. An accurate assessment is a critical component in identifying the type of paralysis and developing an individualized treatment plan.

Donors for nerve transplantation in craniofacial soft tissue injuries

Neural tissue is an important soft tissue; for instance, craniofacial nerves govern several aspects of human behavior, including the expression of speech, emotion transmission, sensation, and motor function. Therefore, nerve repair to promote functional recovery after craniofacial soft tissue injuries is indispensable. However, the repair and regeneration of craniofacial nerves are challenging due to their intricate anatomical and physiological characteristics. Currently, nerve transplantation is an irreplaceable treatment for segmental nerve defects. With the development of emerging technologies, transplantation donors have become more diverse. The present article reviews the traditional and emerging alternative materials aimed at advancing cutting-edge research on craniofacial nerve repair and facilitating the transition from the laboratory to the clinic. It also provides a reference for donor selection for nerve repair after clinical craniofacial soft tissue injuries. We found that autografts are still widely accepted as the first options for segmental nerve defects. However, allogeneic composite functional units have a strong advantage for nerve transplantation for nerve defects accompanied by several tissue damages or loss. As an alternative to autografts, decellularized tissue has attracted increasing attention because of its low immunogenicity. Nerve conduits have been developed from traditional autologous tissue to composite conduits based on various synthetic materials, with developments in tissue engineering technology. Nerve conduits have great potential to replace traditional donors because their structures are more consistent with the physiological microenvironment and show self-regulation performance with improvements in 3D technology. New materials, such as hydrogels and nanomaterials, have attracted increasing attention in the biomedical field. Their biocompatibility and stimuli-responsiveness have been gradually explored by researchers in the regeneration and regulation of neural networks.

Blink Reflex in Neurotrophic Keratopathy: An Electrophysiological Evaluation

PURPOSE

Neurotrophic keratitis (NK) is a rare condition which may result in visual loss. This case review investigates if there may be an association between NK and the blink reflex in the absence of facial nerve palsy and lagophthalmos.

METHODS

This is a retrospective case review of 5 patients with trigeminal nerve damage referred to the oculoplastic department with suspected anesthetic corneae. Information on etiology, symptoms, duration, associated medical conditions, medications, examination findings including Mackie stage of keratopathy, management of keratopathy, and blink electrophysiology results was obtained.

RESULTS

All 5 patients demonstrated absence of corneal sensation. All patients had preserved facial nerve function with no evidence of lagophthalmos. Keratopathy ranged from Mackie stage 0-2. Management ranged from ocular lubricants to Botulinum-toxin-induced ptosis. Blink studies demonstrated reduction in amplitude as well as increased latency in 2 patients, conferring reduced blink strength. Two patients demonstrated an absent blink reflex on the affected side. One patient had blink latency within the normative range; this patient recovered corneal sensation and was discharged.

CONCLUSIONS

Our finding of reduced amplitude in blink studies offers both a factor in pathogenesis of NK and a potential therapeutic target. Additionally, blink studies may provide prognostic information for recovery and therefore guide management. We suggest performing blink electrophysiology in patients with trigeminal nerve damage to assess nerve function.

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.

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.

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.

Gómez-López-Hernández syndrome: a case report on pediatric neurotrophic corneal ulcers and review of the literature

We present a case of Gómez-López-Hernández syndrome (GLHS), a rare neurocutaneous syndrome, in a 10-month-old girl with neurotrophic keratopathy secondary to trigeminal anesthesia.

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.

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: A Game-Changing Surgical Procedure for Neurotrophic Keratopathy

PURPOSE

The aim of this study is to describe techniques, results, and open issues of corneal neurotization (CN) for the treatment of neurotrophic keratopathy (NK).

METHODS

An overview of the most important studies of CN is provided. The 2 main surgical approaches (namely, direct CN and indirect CN) with specific advantages and disadvantages are described. The results regarding changes of corneal sensitivity and clarity, visual acuity, and in vivo confocal microscopy metrics are summarized. Ex vivo studies with histopathology of the neurotized cornea are reported. Intraoperative and early and late postoperative complications are described along with current open issues to be further clarified.

RESULTS

Corneal sensitivity improves after both direct and indirect CN. Corneal reinnervation allows the healing of NK in almost the totality of the operated eyes, determining a corresponding improvement of corneal clarity and visual acuity. Regeneration of corneal nerve fibers is confirmed by means of either in vivo confocal microscopy or ex vivo histopathology. Few self-limiting complications are reported during the postoperative course. Current open issues concern the identification of the technique of choice, the use of autograft or allograft, and the timing of CN either when performed alone or when combined with other surgeries.

CONCLUSIONS

CN represents a game-changing surgical procedure for NK, which has the potential to restore corneal sensitivity in all stages of the disease regardless of the mechanism of denervation. Further long-term results are needed to confirm its efficacy over time. The design of randomized clinical trials comparing CN with noninterventional therapies could further validate the adoption of this technique.

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.

Clinical and Morphologic Outcomes of Minimally Invasive Direct Corneal Neurotization

PURPOSE

To describe clinical outcomes of a minimally invasive technique for direct corneal neurotization to treat neurotrophic keratopathy.

METHODS

All cases of corneal neurotization for neurotrophic keratopathy performed by a single surgeon using minimally invasive direct corneal neurotization were reviewed. The supraorbital donor nerve was directly transferred to the cornea through an upper eyelid crease incision using either a combination of endoscopic and direct visualization or direct visualization alone. Detailed ocular and adnexal examinations as well as Cochet-Bonnet esthesiometry of the affected cornea were performed. Corneal histopathology and in vivo confocal microscopy after minimally invasive direct corneal neurotization were reviewed in one patient who underwent simultaneous penetrating keratoplasty.

RESULTS

Five consecutive cases in 4 patients were included, with a mean follow up of 15.8 months (range: 11-23 months). Average denervation time was 17.8 months (range: 6-24 months). Baseline corneal conditions were Mackie stage 1 (20%), Mackie stage 2 (40%), and Mackie stage 3 (40%). All patients demonstrated improvements in corneal sensibility and appearance postoperatively. All patients demonstrated stable or improved visual acuity. No patients developed persistent epithelial defects postoperatively, and all achieved return of tactile skin sensation in the donor nerve sensory distribution. In vivo confocal microscopy after minimally invasive direct corneal neurotization and simultaneous penetrating keratoplasty demonstrated regeneration of corneal nerves. Complications included an asymptomatic small bony excrescence lateral to the supraorbital notch in one patient and cataract progression in the patient who underwent penetrating keratoplasty.

CONCLUSIONS

Minimally invasive direct corneal neurotization is a safe and effective treatment of neurotrophic keratopathy.

Corneal Neurotization in the Setting of Facial Paralysis: A Comprehensive Review of Surgical Techniques

ABSTRACT

Neurotrophic keratopathy is characterized by decreased corneal sensitivity, decreased reflex tearing, and poor corneal healing resulting in corneal injury. Without proper sensory innervation, the cornea undergoes continuous epithelial injury, ulceration, infection and eventually results in vision loss. In situations where patients have concomitant facial paralysis, such as after resection of a large vestibular schwannoma, the ocular health is further impaired by paralytic lagophthalmos with decreased eye closure and blink reflex, decreased tearing, and potential lower eyelid malposition. In patients with a dual nerve injury, the ocular surface is in significant danger, as there is increased environmental exposure in conjunction with the inability to sense damage when it occurs. Immediate recognition and care of the eye are critical for maintaining ocular health and preventing irreversible vision loss. The first modern corneal neurotization procedure was described in 2009. The ultimate goal in corneal neurotization is to establish sub-basal plexus regeneration via transferring a healthy nerve to the corneo-limbal region. Corneal neurotization can be achieved either via a direct transfer of healthy nerve (direct approach) or via nerve graft interpositions (indirect approach). This is an emerging concept in the treatment of neurotrophic/exposure keratitis and over the past decade multiple direct and indirect approaches have been described in the attempt to restore corneal sensation and to prevent the devastating outcomes of neurotrophic keratitis. Knowledge of these techniques, their advantages, and disadvantages is required for proper management of patients suffering from neurotrophic keratitis in the setting of facial paralysis.

CORNEAL NEUROTIZATION IN A PATIENT WITH SEVERE NEUROTROPHIC KERATOPATHY. CASE REPORT

PURPOSE

Neurotrophic keratopathy (NK) is a degenerative corneal disease caused by damage to the trigeminal innervation due to a decrease in corneal sensitivity or complete anaesthesia. Impaired corneal innervation leads to morphological and metabolic disorders of the epithelium. In addition, it also leads to the development of recurrent or persistent epithelial defects in corneal ulcers, which may progress to stromal lysis and corneal perforation. One possible solution for severe NK is reinnervation of the anaesthetic cornea (corneal neurotization) using the supraorbital nerve and an autologous sensory nerve graft (indirect neurotization). This article presents the results of corneal neurotization in a young male patient with persistent epithelial defects and corneal ulcers due to corneal denervation.

RESULTS

A 22-year-old man with a history of neurosurgery for astrocytoma of the cerebellum and trunk on the right side at the age of 2 years, was observed for postoperative paresis of the right facial nerve with lagophthalmos in his childhood. The presence of asymptomatic dysfunction of the right trigeminal nerve was also noted. At the age of 22 years, after right eyeball contusion, the vision of the right eye decreased and a persistent epithelial defect developed, followed by corneal ulceration. Due to the exhaustion of therapeutic options in a young patient with corneal anaesthesia, the cornea was reinnervated via the contralateral supraorbital nerve using an autologous sural nerve graft. Five months after the surgery, the sensitivity of the cornea of the right eye began to recover. After amniotic membrane transplantation, the extensive epithelial defect healed, and the opaque corneal stroma gradually cleared up.

CONCLUSION

The reinnervation of the anaesthetic cornea (corneal neurotization) using the supraorbital nerve and the autologous sensory nerve graft represents a new solution for severe NK treatment. The severe corneal condition in our patient healed after the surgery.

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.

[Neurotization of the cornea as pathogenically targeted method of treating neurotrophic keratitis in patients with facial paralysis]

Combined lesions of the facial and trigeminal cranial nerves are typical after neurosurgical treatment. Violation of the innervation of orbicularis muscle leads to inability to completely close the eyelids, while denervation of the cornea is often manifested as a long-term ongoing and recurring neurotrophic keratitis. The restoration of corneal innervation is a pathogenetically targeted treatment for this pathology. For this purpose, neurotrophic keratitis could be reversed via the method of corneal neurotization using contralateral n. ophthalmicus. The presented clinical case demonstrates the results of the first operation of neurotization of the cornea in a patient with combined lesions of the facial and trigeminal nerves.

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.