Neurotrophic Keratopathy: Current Perspectives

Evaluating the efficacy and safety of therapeutic interventions for corneal neuropathy: A systematic review

Corneal neuropathy involves corneal nerve damage that disrupts ocular surface integrity, negatively impacting quality-of-life from pain and impaired vision. Any ocular or systemic condition that damages the trigeminal nerve can lead to corneal neuropathy. However, the condition currently does not have standardized diagnostic criteria or treatment protocols. The primary aim of this systematic review was to evaluate the efficacy and safety of interventions for treating corneal neuropathy. Randomized controlled trials (RCTs) that investigated corneal neuropathy treatments were eligible if the intervention(s) was compared to a placebo or active comparator. Comprehensive searches were conducted in Ovid MEDLINE, Ovid Embase and clinical trial registries from inception to July 2022. The Cochrane Risk-of-Bias 2 tool was used to assess study methodological quality. Certainty of the body of evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Overall, 20 RCTs were included. Evaluated interventions comprised regenerative therapies (n = 6 studies), dietary supplements (n = 4), anti-glycemic agents (n = 3), combination therapy (n = 3), supportive therapies (n = 2) and systemic pain pharmacotherapies (n = 2). Nine RCTs were judged at high risk of bias for most outcomes. Definitions for corneal neuropathy in the populations varied substantially across studies, consistent with lack of consensus on diagnostic criteria. A diverse range of outcomes were quantified, likely reflecting absence of an agreed core outcome set. There was insufficient evidence to draw definitive conclusions on the efficacy or safety of any intervention. There was low or very low certainty evidence for several neuroregenerative agents and dietary supplements for improving corneal nerve fiber length in corneal neuropathy due to dry eye disease and diabetes. Low or very low certainty evidence was found for neuroregenerative therapies and dietary supplements not altering corneal immune cell density. This review identifies a need to standardize the clinical definition of corneal neuropathy and define a minimum set of core outcome measures. Together, this will provide a foundation for improved phenotyping of clinical populations in studies, and improve the capacity to synthesize data to inform evidence-based care. Protocol registration: PROSPERO ID: CRD42022348475.

Associated Neurotrophic Keratopathy in Complex Regional Pain Syndrome

PURPOSE

To report a case of neurotrophic keratopathy (NK) in a patient with complex regional pain syndrome (CRPS) with ipsilateral facial involvement.

METHODS

Case report.

RESULTS

An 18-year old woman with a 5-year history of CRPS type I, a systemic disorder with a neuropathic component with associated limb and right facial involvement, presented with an insidious onset of blurred vision and pain in the right eye. Ocular examination revealed decreased corneal sensation, as measured by Cochet-Bonnet testing, associated with recurrent epithelial defects and whorl-like superficial corneal epitheliopathy. NK was suspected and confirmed by in vivo confocal microscopy (IVCM), which revealed rarefaction of the subbasal nerve plexus in the affected eye. To enhance corneal nerve health, plasma rich in growth factors drops were used. Persistence of NK prompted a superficial keratectomy with placement of an amniotic membrane graft and a course of cenegermin 0.002% (Oxervate; Dompé Farmaceutici SpA, Italy) in the postoperative period. This combination therapy resulted in successful epithelial closure and vision improvement after 8 weeks of therapy with no recurrence of disease for 11 months. Importantly, at that final visit, IVCM demonstrated growth of corneal nerves for the first time in this patient.

CONCLUSIONS

This is the first case report of NK occurring in the context of CRPS, a neuropathy with ipsilateral facial pain involvement. IVCM was important in the diagnosis of NK, which responded successfully to ocular surface treatments focused on nerve health stimulation that ultimately resulted in corneal nerve growth.

Neurotrophic keratopathy and refractive surgery

PURPOSE OF REVIEW

Corneal nerve function is an important consideration for the refractive surgeon. In patients without a history of neuropathy, refractive surgery can lead to destruction of corneal nerves and may predispose to keratopathy. The purpose of this review is to provide an update on the effect of refractive surgery on corneal nerve function and the potential for an increased risk of neurotrophic keratopathy development.

RECENT FINDINGS

Recent studies have reinforced that refractive surgery can cause anatomical and functional changes in corneal nerve function. Among the most commonly performed refractive surgery procedures are Laser Assisted In-situ Keratomileusis, Photorefractive Keratectomy, and Small Incision Lenticule Extraction. Due to differences in technique, these procedures can have varying effects on corneal nerve structure. Using in vivo confocal microscopy, postrefractive patients were found to have decreased total nerve density when compared with controls in the immediate postoperative period. In some studies, patients have been shown to undergo re-innervation and regain significant amounts of nerve function. The majority of studies have found that despite decreased nerve cell density, long-term outcomes of refractive surgery patients are generally favorable. However, loss of corneal nerve function can lead to a variety of serious effects ranging from dry eye disease, corneal hypoesthesia/anesthesia, neuropathic pain, to neurotrophic keratopathy and ulceration in the rare cases.

SUMMARY

Neurotrophic keratopathy is a rare occurrence after keratorefractive surgery and is largely due to damage to corneal nerves. Proper patient selection and counseling are essential to decrease the risk of development of this devastating complication.

The cornea IV immunology, infection, neovascularization, and surgery chapter 1: Corneal immunology

PURPOSE

of Review: This review offers an informed and up-to-date insight on the immune profile of the cornea and the factors that govern the regulation of such a unique immune environment.

SUMMARY

The cornea is a unique tissue that performs the specialized task of allowing light to penetrate for visual interpretation. To accomplish this, the ocular surface requires a distinct immune environment that is achieved through unique structural, cellular and molecular factors. Not only must the cornea be able to fend off invasive infectious agents but also control the inflammatory response as to avoid collateral, and potentially blinding damage; particularly of post-mitotic cells such as the corneal endothelium. To combat infections, both innate and adaptive arms of the inflammatory immune response are at play in the cornea. Dendritic cells play a critical role in coordinating both these responses in order to fend off infections. On the other side of the spectrum, the ocular surface is also endowed with a variety of anatomic and physiologic components that aid in regulating the immune response to prevent excessive, potentially damaging, inflammation. This attenuation of the immune response is termed immune privilege. The balance between pro and anti-inflammatory reactions is key for preservation of the functional integrity of the cornea.

RECENT FINDINGS

The understanding of the molecular and cellular factors governing corneal immunology and its response to antigens is a growing field. Dendritic cells in the normal cornea play a crucial role in combating infections and coordinating the inflammatory arms of the immune response, particularly through coordination with T-helper cells. The role of neuropeptides is recently becoming more highlighted with different factors working on both sides of the inflammatory balance.

High Molecular Weight Hyaluronan Promotes Corneal Nerve Growth in Severe Dry Eyes

The purpose of this study was to investigate the effect of high molecular weight hyaluronan (HMWHA) eye drops on subbasal corneal nerves in patients suffering from severe dry eye disease (DED) and to evaluate the damage of subbasal corneal nerves associated with severe DED. Designed as an international, multicenter study, 16 patients with symptoms of at least an Ocular Surface Disease Index (OSDI) score of 33, and corneal fluorescein staining (CFS) of at least Oxford grade 3, were included and randomized into two study arms. The control group continued to use their individual optimum artificial tears over the study period of eight weeks; in the verum group, the artificial tears were substituted by eye drops containing 0.15% HMWHA. At the baseline visit, and after eight weeks, the subbasal nerve plexus of 16 patients were assessed by confocal laser scanning microscopy (CSLM). The images were submitted to a masked reading center for evaluation. Results showed a significant increase of total nerve fiber lengths (CNFL) in the HMWHA group (p = 0.030) when compared to the control group, where the total subbasal CNFL did not significantly change from baseline to week 8. We concluded that in severe DED patients, HMWHA from topically applied eye drops could cross the epithelial barrier and reach the subbasal nerve plexus, where it exercised a trophic effect.