Update on corneal neurotisation

Neurotrophic keratopathy: General features and new therapies

Neurotrophic keratopathy is an uncommon degenerative corneal disorder characterized by compromised corneal sensory innervation resulting in the formation of epithelial defects and nonhealing corneal ulcers. Various treatment modalities are available to stabilize disease progression, improve patient well-being, and prevent vision loss. For eligible patients, medical and surgical reinnervation have emerged as pioneering therapies, holding promise for better management. We present a comprehensive review of the disorder, providing an update relevant to ophthalmologists on pathogenesis, diagnosis, treatment options, and novel therapies targeting pathophysiological pathways.

Corneal Neurotization for Neurotrophic Keratopathy: A Multicentre 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.

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.

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.

Surgical management of infectious keratitis

The successful management of infectious keratitis is usually achieved with a combination of tools for accurate diagnosis and targeted timely antimicrobial therapy. An armamentarium of surgical interventions is available in the acute stage which can be resorted to in a step wise manner or in combination guided by the response to treatment. Simple surgical modalities can facilitate accurate diagnosis e.g. corneal biopsy and alcohol delamination. Surgery to promote epithelial healing can vary from tarsorrhaphy, amniotic membrane transplantation or conjunctival flaps depending on the extent of infection, visual prognosis, availability of tissue and surgeon's experience. Collagen crosslinking has been increasingly utilized with successful results to strengthen the cornea and reduce the infective load consequently the need for further elaborate surgical interventions. It has shown encouraging results specially in superficial bacterial and fungal keratitis but for deeper infections, viral and acanthamoeba keratitis, its use remains questionable. When globe integrity is compromised, corneal gluing is the most commonly used procedure to seal small perforations. In larger perforations/fulminant infections a tectonic/therapeutic graft is advisable. Partial thickness grafts are increasingly popular to treat superficial infection or internally tamponade perforations. Peripheral therapeutic grafts face challenges with potential requirement for a manually fashioned graft, and increased risk of rejection due to proximity to the limbal vessels. Late stage visual rehabilitation is likely to require further surgical interventions after complete resolution of infection and inflammation. A preliminary assessment of corneal sensation and integrity of the ocular surface are key for any successful surgical intervention to restore vision.

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.

Minimally invasive corneal neurotization for neurotrophic keratopathy: The potential effect of age, denervation chronicity and lesion location

Purpose

Neurotrophic keratopathy (NK) is an uncommon but challenging clinical condition characterized by altered corneal nerves and sensation leading to corneal damage. Corneal neurotization, a surgical technique that aims to "re-innervate" the cornea, has gained increasing popularity in view of the potential to permanently improve or even restore the normal corneal sensation. In this study, we aimed to report the outcomes of two cases of NK that underwent indirect minimally invasive corneal neurotization (MICN) with a sural nerve autograft, and to provide plausible explanations for the observed clinical outcomes.

Observations

This was an interventional case series of two patients who underwent MICN for severe unilateral NK. The MICN technique was adapted from the technique originally described by Elbaz et al., in 2014. Clinical severity of NK was graded according to Mackie's grading system. Corneal sensation was measured using the Cochet-Bonnet esthesiometer (0-60mm) and corneal nerves were examined using in vivo confocal microscopy (IVCM) with Heidelberg HRT3 Rostock Corneal Module. Patient 1 was a 70-year-old man with a right grade III NK following trigeminal nerve decompression for trigeminal neuralgia. Patient 2 was a 62-year-old man with a left grade II NK following a left-sided acoustic neuroma resection. The denervation time was 23 years for both patients. Following the MICN surgery, none of the patients achieved sustained improvement in the corneal sensation (though patient 1 achieved a transient improvement in central corneal sensation to 20mm at 4 months' postoperative before returning to 0mm at 6 months' postoperative). IVCM did not reveal any changes in the corneal nerve density and morphology post-MICN.

Conclusions and Importance

Based on our observations and the literature, we postulate that long denervation time, proximal injury to the trigeminal nerve and older patient age may serve as poor prognostic factors for MICN. As CN is being increasingly adopted in clinical practice for treating NK, understanding of these potential factors will facilitate better risk-benefit stratification and patient counselling. Future larger studies are required to elucidate these findings.

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.

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.

Pillar tarsoconjunctival flap: An alternative approach for the management of refractory corneal ulcer

PURPOSE

To report the effectiveness of the surgical procedure of the tarsoconjunctival flap (FTC) in patients with severe ocular surface impairment refractory to previous conventional treatments.

METHODS

A retrospective, noncomparative, consecutive case series.

RESULTS

Pillar tarsoconjunctival flap (PTCF) was performed in eight eyes of eight patients. Three patients had neurotrophic corneal ulcer (NCU), three had exposure keratopathy and two had corneal melting. Seven of them had satisfactory postoperative results, showing total corneal re-epithelialization that lasted throughout the postoperative follow-up (mean 10.33 ± 2.65 months [SD], range 6 to 12 months). Mean time for the re-epithelization was 11.28 ± 8.97 days [SD] (range 4 to 30 days).

CONCLUSION

This study suggest PTCF is a valid alternative to tarsorrhaphy in cases of persistent epithelial defect (PED) or NCU resistant to conventional treatments. Notwithstanding, prospective comparative trials comparing PTFC with conventional and/or novel therapies in PED or NCU are needed to corroborate these findings.

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.

Current and future therapies for persistent corneal epithelial defects and neurotrophic keratopathy

PURPOSE OF REVIEW

The corneal epithelium is a crucial barrier against pathogens, and when disrupted in the setting of certain underlying risk factors such as neurotrophic keratopathy (NK), may result in persistent epithelial defects (PEDs) of the cornea. Management is challenging and may require a variety of different approaches ranging from conservative medical therapy to surgical intervention. The purpose of this review is to provide an update on current and potential future therapeutic options for PEDs and NK.

RECENT FINDINGS

Recent research has yielded promising results for numerous novel therapies aimed at treating PEDs. Many of these attempt to stimulate healing at the cellular level, via signaling of corneal epithelial differentiation, migration, and proliferation. Considerable advances have also been made regarding medical and surgical promotion of corneal re-innervation and restoration of corneal sensitivity to directly address the underlying NK condition.

SUMMARY

Together with the current well established therapeutic options available for PEDs and NK, growing research on newer alternatives suggest increasing potential for both more effective and more convenient therapies for these difficult situations.

Aftermarket effects of cenegermin for neurotrophic keratopathy in pediatric patients

PURPOSE

Neurotrophic keratopathy (NK) is a rare condition characterized by poor corneal sensation and healing. Cenegermin (topical recombinant nerve growth factor) has gained traction as a medical therapy for NK in recent years, and is FDA-approved for patients over two years old. However, no major trials have demonstrated the drug's efficacy in children. This study reviews the outcomes of cenegermin therapy in a pediatric patient population.

METHODS

Retrospective case series of patients from three tertiary referral institutions who 1) initiated an 8-week course of cenegermin therapy, and 2) were 18 years or less at time of treatment initiation.

RESULTS

Eight pediatric patients, with a total of nine affected eyes, underwent cenegermin therapy. All eight patients had previously trialed other NK-specific treatments, none of which had been entirely successful. Five patients (63%) completed the full eight-week therapy course. Five patients (63%) experienced clinical improvement not attributed to another treatment, through improved corneal ulcer stage (n = 5) and best-corrected visual acuity (n = 2). Clinical improvements persisted through a mean recurrence-free period of 10 months. Adverse effects reported during therapy included ocular pain, difficulty sleeping, and continued corneal thinning.

CONCLUSION

The results provide modest support for the use of cenegermin in pediatric patients with neurotrophic keratopathy. The primary benefit was an improvement in corneal epithelial stability. Clinicians should be aware that pre-existing corneal scarring in NK may significantly limit the ability of cenegermin alone to improve visual acuity, and should closely monitor the corneal epithelial status during therapy in pediatric patients.

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.

Neurotrophic Keratopathy in Pediatric Patients

Purpose: This review provides an overview of the causes and treatment of neurotrophic keratopathy in the pediatric population.Methods: A thorough review of the current literature discussing neurotrophic keratopathy was conducted then summarized.Results:Fourty-nine papers were reviewed. Congenital and acquired causes of neurotrophic keratopathy exist in the pediatric population. Both medical and surgical approaches to treatment have been trialed, albeit to a limited extent, in pediatric patients. Conservative treatment includes topical lubrication and antibiotics to prevent concurrent infectious ulcer formation. Various neurotrophic factors have been trialed in the form of serum drops to restore corneal sensation when conservative measures fail. Surgically, different corneal neurotization techniques have been developed whereby a donor nerve is routed to the anesthetized cornea to restore innervation and sensation. Conclusions: Advances in the treatment of neurotrophic keratopathy have made corneal reinnervation and restoration of vision more easily attainable in pediatric patients.

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.

The surgical management of extra-cranial trigeminal nerve palsies: A retrospective case series

OBJECTIVES

To assess for functional improvement in outcomes following supermicrosurgical restoration across a cohort of patients with a spectrum of trigeminal nerve disorders.

PATIENTS & METHODS

In a retrospective case series over three years (2016-18), twenty patients were included in a cohort of trigeminal nerve palsy patients. Eleven patients with corneal anaesthesia underwent corneal neurotisation procedures and were followed up using Cochet-Bonnet aesthesiometry. Six patients with sensory trigeminal nerve injuries had direct nerve coaptation and neuroma excision. Three patients with trigeminal motor nerve palsies were followed up with photography for contour improvement.

RESULTS

Regarding corneal neurotisation, there was evidence of significant improvement in protective corneal sensation and also blinking frequency. Regarding facial sensory disturbances, all patients had full resolution of painful trigeminal neuroma symptoms. In two cases of iatrogenic trigeminal motor palsies with contour defects, adipo-fascial variants of the superficial circumflex iliac artery (SCIP) free flap achieved excellent restoration of facial contour in lieu of facial lipofilling. In another case of a necrotising infection of the head and neck with loss of all masticatory muscles, a free functional muscle using a chimaeric vastus lateralis-ALT flap was used to restore masticatory and facial movement in a single stage procedure.

CONCLUSION

Using combinations and permutations of current surgical techniques, it is possible to successfully restore both form and function for patients with sensory as well as motor trigeminal nerve palsies. This sets a precedent for the expansion of cranial nerve surgery as an evolving sub-speciality.

In Vivo and Ex Vivo Comprehensive Evaluation of Corneal Reinnervation in Eyes Neurotized With Contralateral Supratrochlear and Supraorbital Nerves

PURPOSE

To use an automated morphometric analysis system of in vivo confocal microscopy (IVCM) images for evaluating reinnervation occurring at the subbasal nerve plexus (SNP) after direct corneal neurotization (DCN) and to further report neurophysiological and histopathological findings.

METHODS

Prospective interventional case series including 3 eyes with neurotrophic keratitis that underwent DCN. Deep anterior lamellar keratoplasty was performed 18 months after DCN in patient 1. The following evaluations were performed before and at 3, 6, and 12 months after DCN: clinical evolution of keratitis; corneal sensitivity; IVCM images of the SNP analyzed with "ACCMetrics;" neurophysiological study of corneal reflex. Protein gene product 9.5 immunofluorescence staining assay and transmission electron microscopy were conducted on the neurotized button excised during deep anterior lamellar keratoplasty.

RESULTS

Complete healing was obtained in all patients by 3 months postoperatively. Corneal sensitivity was absent preoperatively in all eyes and improved after surgery, reaching an average value of 30 mm 1 year postoperatively. The corneal SNP was not visible at IVCM in any of the cases preoperatively and became visible by 3 months postoperatively, showing IVCM metrics comparable to normal contralateral eyes at 1 year. In all cases, neurophysiological evaluation showed a partial recovery of the electrical activity of the cornea. In patient 1, protein gene product (PGP) 9.5 staining of neurotized cornea showed nerve fascicles at the SNP, whereas transmission electron microscopy showed amyelinic nerve axons and nerve endings.

CONCLUSIONS

The corneal SNP exhibited IVCM metrics comparable to the normal contralateral eye 1 year after DCN. Ex vivo histopathological assessment of neurotized corneas confirmed the presence of nerves with normal ultrastructure.

Chemical eye injury: pathophysiology, assessment and management

Chemical eye injury (CEI) is an acute emergency which can threaten sight and life. These commonly occur at home or the workplace with the former being generally mild and the latter more severe and bilateral. Major workplace accidents involve other parts of the body and can be associated with inhalation or ingestion of the chemical. Alkali injuries cause damage by saponification of tissue and deeper penetration as a consequence. Acid injuries cause rapid coagulation of tissue, which impedes penetration and limits damage. Irritants such as alcohols, cause superficial epithelial denudation. Severe chemical insult can affect all anterior segment structures causing iris, pupil and lens abnormalities. Eye pressure is variably affected and can be low or high or start as one and rapidly change to the other. Chorioretinal changes in the form of vasculopathy are seen and ascribed to be secondary to anterior segment inflammation rather than due to the direct effect of CEI. Final outcome related to structure and function is determined by the injurious agent, duration of exposure, nature of treatment and the rapidity with which it is instituted. Prevention of further damage by profuse and prolonged eye wash, after ascertaining pH of both eyes, together with exploration and removal of all particulate matter, is the key. Other management principles include a complete and thorough assessment, control of inflammation, facilitation of healing and prevention and management of sequelae and complications. Intraocular pressure is often forgotten and must be assessed and managed. Management often requires a multidisciplinary approach.

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.

In Vivo Evaluation of Corneal Nerves and Epithelial Healing After Treatment With Recombinant Nerve Growth Factor for Neurotrophic Keratopathy

PURPOSE

To evaluate the renewal of corneal nerve structure and function in patients with neurotrophic keratopathy (NK) treated with recombinant human nerve growth factor (rhNGF) eye drops.

DESIGN

Prospective, interventional, before-and-after case series.

METHODS

This study included 18 patients with NK with a persistent epithelial defect or corneal ulcer, treated with topical rhNGF, and age-matched healthy controls. Patients underwent clinical examination with corneal fluorescein staining, Schirmer 1 tear test, assessment of corneal sensitivity with the Cochet-Bonnet esthesiometer, and morphologic examination of the nerves by in vivo confocal microscopy (IVCM) at baseline and at 4 and 8 weeks of treatment. IVCM analysis was used to assess corneal sub-basal nerve density, number of nerve branches, and the diameter of nerve fibers.

RESULTS

A complete resolution of the epithelial defect was observed in all patients within 8 weeks. Schirmer 1 test showed a significant improvement of tear film secretion. Change from baseline in corneal sensation was significant (P < .001) but did not approach that of healthy controls. After 8 weeks of treatment, there was a significant increase in the mean nerve density in affected eyes as compared to baseline (P = .007) as well as in the number of nerve branches (P = .008) and nerve fiber diameter (P = .007).

CONCLUSIONS

Topical treatment with rhNGF was effective in promoting complete corneal healing of persistent epithelial defects and corneal ulcers in patients with NK. This was associated with an improvement of corneal sensitivity and an increase of sub-basal nerve density, diameter, and number of nerve branches, indicating improvement in structure and function of corneal nerves.

Corneal neurotization

PURPOSE OF REVIEW

Neurotrophic keratopathy is a devastating corneal condition that can lead to ocular morbidity and blindness. Current medical and surgical treatments poorly tackle the essential problem of corneal aesthesia and hence fail to provide a permanent cure. Recent advances in corneal neurotization techniques have shown promise to restore corneal nerves in neurotrophic keratopathy. This article aims at reviewing the current surgical advances, along with the current thoughts and evidence available for corneal nerve regeneration.

RECENT FINDINGS

Corneal neurotization was first introduced in 2009 by Terzis et al., but recently picked up more interest since 2014. Direct and indirect neurotization are being developed, and different nerves (sural nerve, great auricular nerve) have been explored for interposition between frontal nerve branches and the cornea. New endoscopic techniques are introduced for less invasive approaches. On the corneal front, confocal microscopy and esthesiometry studies have established that the regeneration of the corneal nerves is happening 6 months after the procedure.

SUMMARY

Neurotization is a budding revolutionary technique that shows promise of cure for neurotrophic corneas, but at this stage, it is still reasonably invasive and still reserved for selected patients.