Red and green defocus curves and duochrome test in different age groups / Curvas de desenfoque rojo y verde y prueba de duocromo en diferentes grupos de edad

Purpose: To compare the eye defocus curves (DCs) obtained with stimuli on red, green, and white backgrounds and to investigate the applicability of the duochrome test (DT) in different age groups. Methods: 12 elderly (ELD: 59.3 ± 3.9 years) and 8 young (YG: 22.1 ± 1.1 years) subjects were recruited. An optometric assessment with the DT was carried out to obtain the subjective refraction at distance. DCs at distance on green, white, and red backgrounds were measured and the following parameters were deduced: dioptric difference between red-green, green-white, red-white focal positions (minima of the DCs), best corrected visual acuity (BCVA), and widths of the DCs for red, green, and white. Results: The DC difference between the green-white focal positions (mean ± standard deviation) was -0.12±0.17 diopters (D) (ELD, p = 0.012) and -0.11±0.12 D (YG, p = 0.039), while the red-white difference was not statistically significant. The DC red-green difference was 0.20±0.16 D (ELD, p = 0.002) and 0.18±0.18 D (YG, p = 0.008). The ELD BCVA with green background was significantly worse than BCVA with red (p = 0.007) and white (p = 0.007). The mean value of the DC's width in ELD for green (1.01±0.36 D) was higher than for red (0.77±0.21 D) and for white (0.84±0.35 D), but with no statistical significance. Conclusion: Both age groups showed a slight focusing preference for red when using white light. Moreover, ELD showed a worse BCVA with a green compared to a red background. Despite these results deduced by DC analyses, these aspects do not compromise the possibility of using the DT in clinical practice both in the young and in the elderly. Furthermore, the difference of about 0.20 D between red-green DC in both groups confirms the clinical appropriateness of the widespread use of 0.25 D step as the standard minimum difference in power between correcting lenses.(AU)

In-vitro dehydration kinetics coefficient of Kalifilcon A and other contact lens materials.

In contact lens (CL) wear, dehydration needs to be tailored to avoid dryness and related symptoms. In this view, this work aims to assess and compare the in-vitro dehydration kinetics of five CL materials, including the newly developed Kalifilcon A CL. At 36 °C and 60% relative humidity, the in-vitro dehydration kinetics of the different CLs were compared using a gravimetric method. CLs were analyzed either after a rinse of a few seconds in preservative-free saline solution or after a 24-h incubation in the same solution. A model based on the Fick diffusion equation was employed to deduce a water kinetics coefficient, providing insights into water diffusion within the polymeric matrix. The study reveals that all materials exhibit a non-Fickian dehydration behavior, with significant differences in dehydration kinetics coefficients and dehydration rate slopes. Etafilcon A and Omafilcon A, both hydrogel CLs, exhibit a similar behavior, different compared to the pattern shown by Senofilcon A and Delefilcon A, silicone-hydrogel CLs. Notably, Kalifilcon A, despite being a silicone-hydrogel, displays a hydration behavior reminiscent of hydrogel CLs.

Cortical dynamics in visual areas induced by the first use of multifocal contact lenses in presbyopes.

A common non-spectacle strategy to correct presbyopia is to provide simultaneous images with multifocal optical designs. Understanding the neuroadaptation mechanisms behind multifocal devices usage would have important clinical implications, such as predicting whether patients will be able to tolerate multifocal optics. The aim of this study was to evaluate the brain correlates during the initial wear of multifocal contact lenses (CLs) using high-density visual evoked potential (VEP) measures. Fifteen presbyopes (mean age 51.8 ±â€¯2.6 years) who had previously not used multifocal CLs were enrolled. VEP measures were achieved while participants looked at arrays of 0.5 logMAR Sloan letters in three different optical conditions arranged with CLs: monofocal condition with the optical power appropriate for the distance viewing; multifocal correction with medium addition; and multifocal correction with low addition. An ANOVA for repeated measures showed that the amplitude of the C1 and N1 components significantly dropped with both multifocal low and medium addition CL conditions compared to monofocal CLs. The P1 and P2 components showed opposite behavior with an increase in amplitudes for multifocal compared to monofocal conditions. VEP data indicated that multifocal presbyopia corrections produce a loss of feedforward activity in the primary visual cortex that is compensated by extra feedback activity in extrastriate areas only, in both early and late visual processing.

Comparing automated and manual assessments of tear break-up time using different non-invasive devices and a fluorescein procedure.

To evaluate the agreement and repeatability of an automated topography-based method for non-invasive break-up time (NIBUT) analyses in comparison with two other NIBUT procedures, the fluorescein procedure (fBUT), and with the manual assessment with the same device. In the first experiment, a semi-randomised crossover study was performed on forty-three participants (23.1 ± 2.1 years). NIBUT measurements were collected in a randomised order, in both eyes of participants with EasyTear View + (Easytear, Rovereto), Polaris, and Sirius + (CSO, Firenze). Then a fBUT was collected. The overall measurement procedure was repeated in a further session (retest) on the same day. In a second experiment, a retrospective randomised crossover study was performed on eighty-five NIBUT videos previously recorded by the Sirius+. Two observers assessed manually the videos and the NIBUTs were compared with the automatic ones. In the first experiment, ANOVA showed a significant difference between the four measures in both eyes (p < 0.001). Significant differences were found in the paired comparisons between each NIBUT procedure and fBUT (Wicoxon; p < 0.05). Sirius+ resulted in agreement only with Polaris in the left eye. Correlations between all NIBUT procedures resulted in statistical significance in both eyes. All procedures showed very good test-rest reliability. In the second experiment, a significant correlation between automated and manual NIBUT was found, but also a significant statistical difference between the two measurements, although clinically negligible (0.3 s). The investigated NIBUT devices perform differently from each other (and from fBUT), so they cannot be considered interchangeable. The automated measure of NIBUT with Sirius+ has a negligible clinical difference compared to manual assessment on the same device.

Red and green defocus curves and duochrome test in different age groups.

PURPOSE: To compare the eye defocus curves (DCs) obtained with stimuli on red, green, and white backgrounds and to investigate the applicability of the duochrome test (DT) in different age groups. METHODS: 12 elderly (ELD: 59.3 ± 3.9 years) and 8 young (YG: 22.1 ± 1.1 years) subjects were recruited. An optometric assessment with the DT was carried out to obtain the subjective refraction at distance. DCs at distance on green, white, and red backgrounds were measured and the following parameters were deduced: dioptric difference between red-green, green-white, red-white focal positions (minima of the DCs), best corrected visual acuity (BCVA), and widths of the DCs for red, green, and white. RESULTS: The DC difference between the green-white focal positions (mean ± standard deviation) was -0.12±0.17 diopters (D) (ELD, p = 0.012) and -0.11±0.12 D (YG, p = 0.039), while the red-white difference was not statistically significant. The DC red-green difference was 0.20±0.16 D (ELD, p = 0.002) and 0.18±0.18 D (YG, p = 0.008). The ELD BCVA with green background was significantly worse than BCVA with red (p = 0.007) and white (p = 0.007). The mean value of the DC's width in ELD for green (1.01±0.36 D) was higher than for red (0.77±0.21 D) and for white (0.84±0.35 D), but with no statistical significance. CONCLUSION: Both age groups showed a slight focusing preference for red when using white light. Moreover, ELD showed a worse BCVA with a green compared to a red background. Despite these results deduced by DC analyses, these aspects do not compromise the possibility of using the DT in clinical practice both in the young and in the elderly. Furthermore, the difference of about 0.20 D between red-green DC in both groups confirms the clinical appropriateness of the widespread use of 0.25 D step as the standard minimum difference in power between correcting lenses.

Translation and validation of convergence insufficiency symptom survey to Italian: Psychometric results

Purpose This study aimed to translate the Convergence Insufficiency Symptom Survey (CISS) into the Italian language and assess psychometric properties of the translated questionnaire (CISS_I). Methods The CISS_I was arranged according to guidelines for a comprehensive multistep methodologic process for translating, adapting, and validating psychometric instruments in health care research. The CISS_I questionnaire was administered to 103 volunteers (21.8 ± 2.2 years), students in higher education, at two different times. A complete optometric evaluation was performed including subjective refraction, best corrected visual acuity, near point of convergence, prism fusional ranges to blur, diplopia and recovery, TNO stereo test and prism cover test for measurement of heterophoria. Results The performance of the CISS_I in terms of validity showed some points of weakness. Sensitivity was 42%, specificity was 74%, positive predictive value was 27% and negative predictive value was 85%. The area under the ROC curve was 0.672. On the contrary, the results showed good internal consistency of the CISS_I (Cronbach's alpha - α=0.89) and good test-retest reliability (ICC = 0.92). Rasch analysis showed good model fit (all items, except one, with infit and outfit mean square between 0.7 and 1.3), good measurement precision (person separation = 2.66) and good targeting –0,81 logits but also some evidence of multidimensionality. Conclusions The CISS_I showed some point of weakness in terms of validity but also good psychometric properties and has been shown to be applicable to an Italian speaking population to quantify the visual discomfort associated with near vision in higher education students. The results show that high CISS_I score is not necessarily linked to convergence insufficiency, while low scores can exclude the presence of this anomaly...(AU)

TFOS Lifestyle: Impact of contact lenses on the ocular surface.

Several lifestyle choices made by contact lens wearers can have adverse consequences on ocular health. These include being non-adherent to contact lens care, sleeping in lenses, ill-advised purchasing options, not seeing an eyecare professional for regular aftercare visits, wearing lenses when feeling unwell, wearing lenses too soon after various forms of ophthalmic surgery, and wearing lenses when engaged in risky behaviors (e.g., when using tobacco, alcohol or recreational drugs). Those with a pre-existing compromised ocular surface may find that contact lens wear exacerbates ocular disease morbidity. Conversely, contact lenses may have various therapeutic benefits. The coronavirus disease-2019 (COVID-19) pandemic impinged upon the lifestyle of contact lens wearers, introducing challenges such as mask-associated dry eye, contact lens discomfort with increased use of digital devices, inadvertent exposure to hand sanitizers, and reduced use of lenses. Wearing contact lenses in challenging environments, such as in the presence of dust and noxious chemicals, or where there is the possibility of ocular trauma (e.g., sport or working with tools) can be problematic, although in some instances lenses can be protective. Contact lenses can be worn for sport, theatre, at high altitude, driving at night, in the military and in space, and special considerations are required when prescribing in such situations to ensure successful outcomes. A systematic review and meta-analysis, incorporated within the review, identified that the influence of lifestyle factors on soft contact lens dropout remains poorly understood, and is an area in need of further research. Overall, this report investigated lifestyle-related choices made by clinicians and contact lens wearers and discovered that when appropriate lifestyle choices are made, contact lens wear can enhance the quality of life of wearers.

Effects of Lens-Induced Astigmatism at Near and Far Distances.

Purpose: To investigate and compare the degradation of visual acuity (VA) in myopic presbyopes due to lens-induced astigmatism at near and at far distance. Patients and Methods: Fourteen corrected myopic presbyopes were recruited. VA (logarithm of the minimum angle of resolution) was measured binocularly for different conditions of lens-induced astigmatism: cylindrical powers of -0.25, -0.50, -0.75, -1.00, -1.50, and -2.00 diopters (and positive spherical power of half the cylindrical power) with two axis orientations (with-the-rule WTR and against-the-rule ATR) were added to their optical correction. Measurements were carried out at far and near distance both in photopic and mesopic conditions, and for high and low contrast (HC/LC) stimuli. The paired Wilcoxon signed-rank statistics test was used to evaluate difference between conditions. Results: The measured VA as a function of the lens-induced astigmatism was described by regression lines in all investigated experimental conditions. The angular coefficients (slopes) of these lines represent the VA degradation, ie, the variation in logMAR corresponding to the addition of 1.00 diopters of cylindrical power. In photopic HC conditions, the VA degradation is significantly more pronounced at far distance than at near distance (0.22±0.06 diopters-1 vs 0.15±0.05 diopters-1, p = 0.0061 in WTR conditions; 0.18±0.06 diopters-1 vs 0.12±0.05 diopters-1, p = 0.0017 in ATR conditions), although VAs at near and at far with zero cylinder were similar (-0.14±0.10 vs -0.14±0.08, p = 0.824). Conclusion: The better tolerance to lens-induced astigmatism blur at near than at far distance in photopic conditions with HC stimuli is tentatively attributed to a possible experience-mediated neural compensation associated to the tendency of the eye toward an inherent astigmatism at near.

Italian translation and validation of the Contact Lens Dry Eye Questionnaire-8 (CLDEQ-8).

PURPOSE: To translate and validate an Italian version of the CLDEQ-8 (CLDEQ-8_IT). METHODS: The study was carried out in two phases. In the first phase, a cross-cultural adaptation of CLDEQ-8 to Italian was performed by forward and backward translation in sequence. In the second phase, a multi-centre study was conducted for the validation of the questionnaire. Validity CLDEQ-8_IT was evaluated against three gestalt questions: overall opinion of soft contact lenses (CLs), global self-assessments of eye sensitivity and eye dryness. Reliability was evaluated by test-retest assessment in a subgroup of subjects. Finally, the psychometric properties of CLDEQ-8_IT were explored by Rasch analysis. RESULTS: Two hundred and forty soft CL wearers, fluent Italian speakers (73 males and 167 females), between 18 and 70 years of age were enrolled. A significant correlation was found between CLDEQ-8_IT and each of the three Gestalt questions. The cutoff score of 12 points demonstrated the best balance between sensitivity and specificity in differentiating wearers grading their CLs as "Excellent/Very good" from those reporting their overall opinion as "Good/Fair/Poor". The Intraclass Correlation Coefficient between test and retest was 0.88 (95% CI: 0.81-0.92). Finally, infit and outfit statistics using Rasch analysis for the 8 items were in a good range, however Principal Components Analysis revealed a certain degree of multi-dimensionality of the instrument. Also, item 8 analysis could be computed after merging the last two response categories. CONCLUSION: The CLDEQ-8_IT showed very good validity and reliability in measuring symptoms of CL wearers, comparable to the original English language version. A cut-off of 12 was confirmed as yielding the best balance between sensitivity and specificity in detecting CL wearers who could benefit from clinical management of their CL-related symptoms. Collapsing of the response options 5 and 6 in the last item of questionnaire could optimise its functioning.

New Italian version of the Wilkins Rate of Reading Test: Materials for repeated-measure designs in optometry and neuropsychological research.

PURPOSE: To develop a series of equivalent passages of text in Italian, according to the principles of the Wilkins Rate of Reading Test (WRRT), suitable for both clinical examination and scientific research when equivalent stimuli are needed to compare performance in repeated-measure designs. METHOD: Fifteen high-frequency Italian words (matched for grammatical class and length to the English WRRT) were used to generate 15 different 10-line meaningless passages, according to the design principles of the English WRRT. Thirty-two healthy Italian-speaking higher education students read the passages aloud according to a fixed randomisation schedule. Performance was recorded digitally to measure reading speed and accuracy offline. Equivalence between the passages and the practice and fatigue effects for both reading speed and accuracy were examined as well as test-retest reliability. RESULTS: No significant difference in reading speed and accuracy was found between the passages. There was a significant practice effect on reading speed but not accuracy, with the first presented passage read significantly slower than the others. There was no evidence of a fatigue effect. Reading speed, the reference metric for the WRRT, showed good test-retest reliability. CONCLUSIONS: The passages of the Italian version of the WRRT were equivalent to each other. The practice effect suggests that familiarisation with the test (i.e., reading at least one matrix of words) should be carried out before consecutive/repeated reading of different passages for experimental or clinical purposes.

Physical Properties and Interaction With the Ocular Surface of Water-Gradient Contact Lenses.

ABSTRACT: Since the introduction of silicone hydrogel contact lenses, many silicone-hydrogel materials have been produced, including water-gradient contact lenses with a silicone hydrogel core and a thin hydrogel outer layer (e.g., delefilcon A, verofilcon A, and lehfilcon A). Their properties have been investigated in various studies assessing both the chemical-physical characteristics and the comfort, but the overall picture is not always consistent. In this study, water-gradient technology is reviewed by looking at basic physical properties both in vitro and in vivo and at the interaction with the human ocular surface. Surface and bulk dehydration, surface wetting and dewetting, shear stress, interaction with tear components and with other environmental compounds, and comfort are discussed.

Centration assessment of an extended depth of focus contact lens for myopic progression control.

PURPOSE: To evaluate the accuracy and the inter and intra-observer reliability of the centration assessment of extended depth of focus (EDOF) contact lenses (CL) using corneal topography. METHOD: EDOF soft CLs (Mylo, Mark'Ennovy) were fitted on thirty-three myopic students (25 females), aged 19-28 years (22.7 ± 2.0 years). For any EDOF CL, a topography over the CL and a slit lamp (SL) digital picture were taken in random order. For the topographic images, the position of the EDOF CL centre, with respect to the pupil centre, was detected by two different practitioners (one newly graduated and one with more than 20 years of clinical experience respectively) and repeated after 15 days. This measurement was compared to the one taken through the SL, considered as the gold standard, and assessed using the instrument software. RESULTS: EDOF CLs resulted decentred inferiorly and temporally ranging, in the case of slit lamp assessment, between -0.27 ± 0.19 and 0.22 ± 0.23 mm horizontally and between -0.12 ± 0.31 and -0.17 ± 0.34 mm vertically, for the right and left eye respectively. The accuracy of the topographic assessment in determining EDOF CL centration was found to be very good compared to the SL assessment. No differences were found for the left eye, whereas in the right eye, a less temporally decentred position of the CL was detected by the topographical method (p < 0.05). However, this difference appeared clinically negligible (0.14 ± 0.22 mm). Inter-observer reliability (the differences between the two practitioners in assessing the EDOF centre) resulted significant only for the vertical coordinates of the centre position (p < 0.05). Concerning intra-observer reliability, better coefficient of precision and reliability between measurements within the same session were achieved by the more experienced practitioner, as well as a better level of the intraclass correlation coefficient in test-retest. CONCLUSION: The centration of the EDOF CL investigated in this study can be accurately detected by a corneal topography performed over CLs. Inter-observer reliability resulted good whereas the intra-observer reliability resulted partially affected by the level of clinical experience of the practitioner.

Translation and validation of convergence insufficiency symptom survey to Italian: Psychometric results.

PURPOSE: This study aimed to translate the Convergence Insufficiency Symptom Survey (CISS) into the Italian language and assess psychometric properties of the translated questionnaire (CISS_I). METHODS: The CISS_I was arranged according to guidelines for a comprehensive multistep methodologic process for translating, adapting, and validating psychometric instruments in health care research. The CISS_I questionnaire was administered to 103 volunteers (21.8 ± 2.2 years), students in higher education, at two different times. A complete optometric evaluation was performed including subjective refraction, best corrected visual acuity, near point of convergence, prism fusional ranges to blur, diplopia and recovery, TNO stereo test and prism cover test for measurement of heterophoria. RESULTS: The performance of the CISS_I in terms of validity showed some points of weakness. Sensitivity was 42%, specificity was 74%, positive predictive value was 27% and negative predictive value was 85%. The area under the ROC curve was 0.672. On the contrary, the results showed good internal consistency of the CISS_I (Cronbach's alpha - α=0.89) and good test-retest reliability (ICC = 0.92). Rasch analysis showed good model fit (all items, except one, with infit and outfit mean square between 0.7 and 1.3), good measurement precision (person separation = 2.66) and good targeting -0,81 logits but also some evidence of multidimensionality. CONCLUSIONS: The CISS_I showed some point of weakness in terms of validity but also good psychometric properties and has been shown to be applicable to an Italian speaking population to quantify the visual discomfort associated with near vision in higher education students. The results show that high CISS_I score is not necessarily linked to convergence insufficiency, while low scores can exclude the presence of this anomaly. The CISS_I can help in interpreting and monitoring convergence insufficiency symptoms in already identified subjects, but it is not suitable for screening a general population of young adults.

Contact Lens Wear Induces Alterations of Lactoferrin Functionality in Human Tears.

The tear film is a complex matrix composed of several molecular classes, from small metal ions to macromolecules. Contact lens (CL) wear can affect the protein homeostasis of the tear film, by accumulating deposits on the CL surface and/or altering their structural and functional properties. This work investigates the effect of CL wear on lactoferrin (Lf), one of the most abundant tear proteins, known as an unspecific biomarker of inflammation. Tears from eight volunteers were collected and analyzed after alternated periods of CL wear and without CL. The experimental approach is to probe Lf into unprocessed human tears by the peculiar fluorescence emission originating from complex formation of Lf with terbium (Tb3+) at the iron-binding sites. The experimental data indicate that CL wear does not significantly affect the total amount of Lf. On the other hand, Lf affinity for Tb3+ is reduced upon CL wear, suggesting relevant changes in Lf structure and possible alterations of protein functionality. Future studies based on this approach will help define CL features (material, lens-care solution, wearing time, etc.) with minimal effects on tear protein activity, in order to obtain more biocompatible and comfortable devices.

Viscoelastic properties of the human tear film.

When considering eye blinking from a tribological perspective, tear viscosity is expected to play a fundamental role. The application of rheological techniques to describe the tear film dates back to the late 1980s, but there has been a continuous need of reappraisal due to new findings in tear film biochemistry and to the development of new methods of physico-chemical characterization. This review provides an overview on tear rheological behavior by analyzing the peer-reviewed literature on this topic. Specifically, examples of in-vitro and in-vivo viscosity measurements are detailed, highlighting experimental criticalities and the need of a standard convention for rheological techniques to compare data across different studies, of analyses on tears of single individuals even within the limits of the low volume available, and of a further development of in-vivo techniques. Then, the controversial role of specific tear components on viscosity is discussed, together with the alterations associated to dry eye disease and contact lens wear. Finally, an updated focus is reported on the viscosity of artificial tears formulations.

In vitro affinity for nicotine of soft contact lenses of different materials.

Smoking is a risk factor for the development of microbial keratitis and corneal infiltrates in contact lens (CL) wearers. It is still unknown if this risk is directly associated with the presence of nicotine in the eye and if adherence of nicotine on the CL can enhance these effects. A better understanding of the interaction between nicotine and CL materials could offer insights to explain this risk associated with smoking. The aim of this work was to compare the affinity of nicotine to different soft CL materials. CLs from FDA groups I, II, IV, and V were incubated in a 2-mM nicotine solution for 24 h and then in a 0.9% saline solution for the next 24 h. The amount of absorbed and released nicotine per CL was deduced as a function of time (t) by ultraviolet (UV) spectrophotometry and normalised to the mass of the hydrated CL. The data were described by the equation y = b -a t-1, where a and b are constants, and b represents the mass reached at the plateau after ~ 10 min of exposure. Groups IV and V displayed the highest (0.80 ± 0.09 µg) and lowest (0.27 ± 0.08 µg) nicotine absorption per mg of hydrated CL, respectively. The CL affinity for nicotine could be ascribed to the interaction between the positive charge of nicotine pyrrolidine nitrogen and the negative charges of the CLs, especially for the ionic IV group.

Mass spectrometry-based tear proteomics for noninvasive biomarker discovery.

The lacrimal film has attracted increasing interest in the last decades as a potential source of biomarkers of physiopathological states, due to its accessibility, moderate complexity, and responsiveness to ocular and systemic diseases. High-performance liquid chromatography-mass spectrometry (LC-MS) has led to effective approaches to tear proteomics, despite the intrinsic limitations in sample amounts. This review focuses on the recent progress in strategy and technology, with an emphasis on the potential for personalized medicine. After an introduction on lacrimal-film composition, examples of applications to biomarker discovery are discussed, comparing approaches based on pooled-sample and single-tear analysis. Then, the most critical steps of the experimental pipeline, that is, tear collection, sample fractionation, and LC-MS implementation, are discussed with reference to proteome-coverage optimization. Advantages and challenges of the alternative procedures are highlighted. Despite the still limited number of studies, tear quantitative proteomics, including single-tear investigation, could offer unique contributions to the identification of low-invasiveness, sustained-accessibility biomarkers, and to the development of personalized approaches to therapy and diagnosis.

Tear-Based Vibrational Spectroscopy Applied to Amyotrophic Lateral Sclerosis.

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.

Single-Tear Proteomics: A Feasible Approach to Precision Medicine.

Lacrimal fluid is an attractive source of noninvasive biomarkers, the main limitation being the small sample amounts typically collected. Advanced analytical methods to allow for proteomics profiling from a few microliters are needed to develop innovative biomarkers, with attractive perspectives of applications to precision medicine. This work describes an effective, analytical pipeline for single-tear analysis by ultrahigh-resolution, shotgun proteomics from 23 healthy human volunteers, leading to high-confidence identification of a total of 890 proteins. Highly reproducible quantification was achieved by either peak intensity, peak area, or spectral counting. Hierarchical clustering revealed a stratification of females vs. males that did not emerge from previous studies on pooled samples. Two subjects were monitored weekly over 3 weeks. The samples clustered by withdrawal time of day (morning vs. afternoon) but not by follow-up week, with elevated levels of components of the immune system in the morning samples. This study demonstrates feasibility of single-tear quantitative proteomics, envisaging contributions of this unconventional body fluid to individualized approaches in biomedicine.