The purpose of this study was a comparison between new and worn siloxane-hydrogel contact lenses in terms of microscopic structure, surface morphology, and loading of hyaluronan. The analyses were performed by scanning electron microscopy, with the support of the freeze-drying technique, and by fluorescence confocal microscopy. Along the depth profile of new lenses, a thin porous top layer was observed, which corresponds to the region of hyaluronan penetration inside well-defined channels. The time evolution was followed from one day to two weeks of daily wear, when a completely different scenario was found. Clear experimental evidence of a buggy surface was observed with several crests and regions of swelling, which could be filled by the hyaluronan solution. The modifications are attributed to the progressive relaxation of the structure of the polymeric network.

Biofluid analysis by optical spectroscopy techniques is attracting considerable interest due to its potential to revolutionize diagnostics and precision medicine, particularly for neurodegenerative diseases. However, the lack of effective biomarkers combined with the unaccomplished identification of convenient biofluids has drastically hampered optical advancements in clinical diagnosis and monitoring of neurodegenerative disorders. Here, we show that vibrational spectroscopy applied to human tears opens a new route, offering a non-invasive, label-free identification of a devastating disease such as amyotrophic lateral sclerosis (ALS). Our proposed approach has been validated using two widespread techniques, namely, Fourier transform infrared (FTIR) and Raman microspectroscopies. In conjunction with multivariate analysis, this vibrational approach made it possible to discriminate between tears from ALS patients and healthy controls (HCs) with high specificity (∼97% and ∼100% for FTIR and Raman spectroscopy, respectively) and sensitivity (∼88% and ∼100% for FTIR and Raman spectroscopy, respectively). Additionally, the investigation of tears allowed us to disclose ALS spectroscopic markers related to protein and lipid alterations, as well as to a reduction of the phenylalanine level, in comparison with HCs. Our findings show that vibrational spectroscopy is a new potential ALS diagnostic approach and indicate that tears are a reliable and non-invasive source of ALS biomarkers.

Objective:Although oculomotor abnormalities (OMAs) are not usually considered prominent features of amyotrophic lateral sclerosis (ALS), they may represent potential clinical markers of neurodegeneration, especially when investigated together with cognitive and behavioral alterations. The aim of our study was to identify patterns of clinically evident OMAs in ALS patients and to correlate such findings with cognitive-behavioral data.Methods: three consecutive, inpatient cohorts of Italian ALS patients and controls were retrospectively evaluated to assess the frequency of OMAs and cognitive-behavioral alterations. The ALS population was divided in a discovery and a replication cohort. Controls included a cohort of cognitively impaired individuals and of patients with Alzheimer’s disease (AD). Subjects underwent bedside eye movement evaluation to determine the presence and pattern of OMAs. Cognitive assessment was performed using a standard neuropsychological battery (discovery ALS cohort, and AD cohort), and the Italian Edinburgh Cognitive and Behavioural ALS Screen – ECAS (replication ALS cohort).Results:We recruited 864 ALS (635 discovery, 229 replication), 798 cognitively unimpaired, and 171 AD subjects. OMAs were detected in 10.5% of our ALS cohort vs 1.6% of cognitively unimpaired controls (p=1.2x10-14) and 11.4% of AD patients (p=ns). The most frequent deficits were smooth pursuit and saccadic abnormalities. OMAs frequency was higher in patients with bulbar onset, prominent upper motor neuron signs, and advanced disease stages. Cognitive dysfunction was significantly more frequent in patients with OMAs in both ALS cohorts (p=1.1x10-25). Furthermore, OMAs significantly correlated with the severity of cognitive impairment and with pathological scores at the ECAS ALS-specific domains. Lastly, OMAs could be observed in 35.0% of cognitively impaired ALS vs 11.4% of AD patients (p=6.4x10-7), suggesting a possible involvement of frontal oculomotor areas in ALS.Discussion:ALS patients showed a range of clinically evident OMAs, and these alterations were significantly correlated with cognitive, but not behavioral, changes. OMAs may be a marker of neurodegeneration and bedside assessment represents a rapid, highly specific tool for detecting cognitive impairment in ALS.