Corneal Nerve Abnormalities in Painful Dry Eye Disease Patients

Coexistence of neuropathic corneal pain, corneal nerve abnormalities, depression, and low quality of life

PURPOSE

To evaluate the quality of life (QoL), mental health conditions and corneal morphology in neuropathic corneal pain (NCP) subjects without a significant ocular surface disease.

METHODS

A composite questionnaire was administered to 228 consecutive subjects, assessing the pain intensity, duration, and quality using a modified version of the Self-Administered Leeds Assessment of Neuropathic Symptoms and Signs (S-LANSS) and Pain Detect (PD) questionnaires. Subjects diagnosed with possible central NCP and two sub-groups of patients diagnosed with peripheral ocular pain completed an additional battery of mental health questionnaires and were examined by In Vivo Confocal Microscopy (IVCM).

RESULTS

Of the 76 subjects that reported chronic ocular pain (duration >1 month), 53 were classified with probable NCP. Nine subjects without signs that justify the pain and non-responding to topical anaesthesia, were considered affected by central NCP. In these patients, a significant negative correlation was found between the presence pain and the mental component of the QoL (R2 = 0.733), and a positive correlation between the severity of pain the presence post-traumatic stress disorder (R2 = 0.83) and depression (R2 = 0.93). Although neuromas and sprouting had higher frequency in the central NCP group compared the control groups, these differences was not statistically different.

CONCLUSIONS

The assessment of ocular pain characteristics using multiple questionnaires and IVCM may help to recognize differences between nociceptive and neuropathic pain. An association between pain intensity and mental health condition may guide the therapeutical choices.

Clinical associations of corneal neuromas with ocular surface diseases

Corneal neuromas, also termed microneuromas, refer to microscopic, irregularly-shaped enlargements of terminal subbasal nerve endings at sites of nerve damage or injury. The formation of corneal neuromas results from damage to corneal nerves, such as following corneal pathology or corneal or intraocular surgeries. Initially, denervated areas of sensory nerve fibers become invaded by sprouts of intact sensory nerve fibers, and later injured axons regenerate and new sprouts called neuromas develop. In recent years, analysis of corneal nerve abnormalities including corneal neuromas which can be identified using in vivo confocal microscopy, a non-invasive imaging technique with microscopic resolution, has been used to evaluate corneal neuropathy and ocular surface dysfunction. Corneal neuromas have been shown to be associated with clinical symptoms of discomfort and dryness of eyes, and are a promising surrogate biomarker for ocular surface diseases, such as neuropathic corneal pain, dry eye disease, diabetic corneal neuropathy, neurotrophic keratopathy, Sjögren's syndrome, bullous keratopathy, post-refractive surgery, and others. In this review, we have summarized the current literature on the association between these ocular surface diseases and the presentation of corneal microneuromas, as well as elaborated on their pathogenesis, visualization via in vivo confocal microscopy, and utility in monitoring treatment efficacy. As current quantitative analysis on neuromas mainly relies on manual annotation and quantification, which is user-dependent and labor-intensive, future direction includes the development of artificial intelligence software to identify and quantify these potential imaging biomarkers in a more automated and sensitive manner, allowing it to be applied in clinical settings more efficiently. Combining imaging and molecular biomarkers may also help elucidate the associations between corneal neuromas and ocular surface diseases.

Light sheet fluorescence microscopy of cleared human eyes

We provide here a procedure enabling light sheet fluorescence microscopy (LSFM) of entire human eyes after iDISCO + -based clearing (ClearEye) and immunolabeling. Demonstrated here in four eyes, post-processing of LSFM stacks enables three-dimensional (3D) navigation and customized display, including en face viewing of the fundus similarly to clinical imaging, with resolution of retinal capillaries. This method overcomes several limitations of traditional histology of the eyes. Tracing of spatially complex structures such as anterior ciliary vessels and Schlemm's canal was achieved. We conclude that LSFM of immunolabeled human eyes after iDISCO + -based clearing is a powerful tool for 3D histology of large human ocular samples, including entire eyes, which will be useful in both anatomopathology and in research.

Open-Source Automated Segmentation of Neuronal Structures in Corneal Confocal Microscopy Images of the Subbasal Nerve Plexus With Accuracy on Par With Human Segmentation

PURPOSE

The aim of this study was to perform automated segmentation of corneal nerves and other structures in corneal confocal microscopy (CCM) images of the subbasal nerve plexus (SNP) in eyes with ocular surface diseases (OSDs).

METHODS

A deep learning-based 2-stage algorithm was designed to perform segmentation of SNP features. In the first stage, to address applanation artifacts, a generative adversarial network-enabled deep network was constructed to identify 3 neighboring corneal layers on each CCM image: epithelium, SNP, and stroma. This network was trained/validated on 470 images of each layer from 73 individuals. The segmented SNP regions were further classified in the second stage by another deep network as follows: background, nerve, neuroma, and immune cells. Twenty-one-fold cross-validation was used to assess the performance of the overall algorithm on a separate data set of 207 manually segmented SNP images from 43 patients with OSD.

RESULTS

For the background, nerve, neuroma, and immune cell classes, the Dice similarity coefficients of the proposed automatic method were 0.992, 0.814, 0.748, and 0.736, respectively. The performance metrics for automatic segmentations were statistically better or equal as compared to human segmentation. In addition, the resulting clinical metrics had good to excellent intraclass correlation coefficients between automatic and human segmentations.

CONCLUSIONS

The proposed automatic method can reliably segment potential CCM biomarkers of OSD onset and progression with accuracy on par with human gradings in real clinical data, which frequently exhibited image acquisition artifacts. To facilitate future studies on OSD, we made our data set and algorithms freely available online as an open-source software package.

Topical Omega-3 Fatty Acids Eyedrops in the Treatment of Dry Eye and Ocular Surface Disease: A Systematic Review

Dry eye is a common inflammatory condition of the ocular surface. While oral omega-3 supplementation for its treatment has been extensively studied, recent large-scale studies have cast doubt on their efficacy. However, efficacy of topical omega-3 has yet to be reviewed. We performed a systematic search of PubMed, Embase, and Cochrane databases for all studies evaluating topical omega-3 in dry eye. Five human and five animal studies were included. Of the five human studies, two were on dry eye disease (DED), one was on contact lens discomfort, and two were on patients undergoing corneal collagen crosslinking. In humans, there is promising evidence for improved ocular surface staining and tear break-up time compared to controls, equivocal evidence for improvements to ocular surface symptoms and meibomian gland dysfunction, and no effect on increasing tear production. Data from animal models largely agree with these findings, and further reveal decreased inflammatory cytokines and monocyte infiltration. Our review suggests that topical omega-3 is a promising treatment for dry eye, but also points to the paucity of evidence in this field. Further trials in humans are required to characterize effects of topical omega-3 and optimize its dosage.

Corneal Nerve Changes Observed by In Vivo Confocal Microscopy in Patients Receiving Oxaliplatin for Colorectal Cancer: The COCO Study

An objective method of early identification of people at risk of chemotherapy-induced peripheral neuropathy is needed to minimize long-term toxicity and maximize dose intensity. The aims of the study were to observe corneal nerve microstructure and corneal sensitivity changes and peripheral neuropathy in patients receiving oxaliplatin, and to determine its association with corneal parameters at different stages of treatment and assess utility as non-invasive markers to detect and monitor peripheral neuropathy. Twenty-three patients scheduled to receive oxaliplatin chemotherapy with intravenous 5-FU for gastro-intestinal cancer were recruited and followed up with for 12 months. Ocular examinations including corneal and retinal evaluations, alongside peripheral neuropathy assessment, were performed. The corneal nerve density did not show significant change after chemotherapy when measured with a widely used semi-automated program or an automated analysis technique. Macula and optic nerve function did not change during or after oxaliplatin chemotherapy. However, the corneal nerve density modestly correlated with clinical peripheral neuropathy after 20 weeks of chemotherapy (r = 0.61, p = 0.01) when peripheral neuropathy is typical most profound, and corneal nerve sensitivity correlated with neuropathy at 12 (r = 0.55, p = 0.01) and 20 weeks (r = 0.64, p = 0.006). In conclusion, corneal changes detected on confocal microscopy show moderate association with peripheral neuropathy, indicating their potential to identify the development of oxaliplatin-induced peripheral neuropathy. However, further studies are required to confirm these findings.

Differences of Anxiety and Depression in Dry Eye Disease Patients According to Age Groups

This study aimed to investigate the association between dry eye disease (DED) and DED-related anxiety and depression tendencies, as well as the risk factors for anxiety and depression in patients with DED of different age groups. This was a cross-sectional study involving 160 patients with DED and 80 healthy individuals aged 20-65 years. All participants completed the investigation of the demographic characteristics, the Hospital Anxiety Depression Scale (HADS), the Ocular Surface Disease Index (OSDI) questionnaire, the Standard Patient Evaluation of Eye Dryness (SPEED) questionnaire, and underwent objective clinical eye examinations. In patients aged 20-40 years, anxiety and depression scores were correlated with OSDI, sleep disorders, and Best Corrected Visual Acuity (BCVA). In patients with DED aged 41-65 years, anxiety scores were correlated with sleep disorders, the level of DED impact on life and work, and the severity of DED. Depression scores were correlated with sleep disorders and the severity of DED. The results indicated that the tendency for anxiety and depression was closely associated with DED and sleep disorders. Moreover, the factors affecting anxiety and depression in patients varied with age.