Accuracy of a New Noninvasive Automatic Ocular Surface Analyzer for the Diagnosis of Dry Eye Disease-Two-Gate Design Using Healthy Controls.

PURPOSE: The purpose of this study was to assess the diagnostic performance of measurements from a new noninvasive, automated ocular surface analyzer (IDRA) in the diagnosis of dry eye disease (DED). METHODS: We prospectively identified patients with and without DED using best practice methods. Subsequently, all participants underwent IDRA analysis, consisting of 5 components: noninvasive tear film break-up time, tear meniscus height, lipid layer interferometry, eye blink quality, and infrared meibography. The manufacturer provides cutoff values for a pathologic result for each of these components. Using a stepwise augmentation multivariate logistic regression model, we identified the components with the strongest association for the presence of DED. For the 3 components with the strongest association (interferometry, tear meniscus, and infrared meibography), we calculated the probability of DED. RESULTS: We enrolled 40 patients (80 eyes) with DED (mean age 60.5 years; women 78.3%) and 35 healthy subjects (70 eyes, mean age 31.1 years; women 21.7%). The IDRA had an area under the curve of 0.868 (95% confidence interval: 0.809-0.927) to detect DED. A normal (≥80) interferometry combined with a normal (>0.22) tear meniscus and a normal (≤40) infrared meibography was associated with an estimated probability of 18% for the presence of DED, whereas the estimated probability of DED was as high as 96% when all 3 findings were pathologic. CONCLUSIONS: The results of IDRA showed a positive concordance with routine clinical diagnostic tests. The new analyzer is an easy-to-access diagnostic tool to rule out the presence of DED in the extramural setting and to guide a timely DED treatment.

Distribution of preoperative angle alpha and angle kappa values in patients undergoing multifocal refractive lens surgery based on a positive contact lens test.

PURPOSE: To assess the preoperative objective angle alpha and angle kappa measurements of patients deciding to undergo multifocal refractive lens surgery based on a subjective positive multifocal contact lens test (MCLT). METHODS: Retrospective, consecutive case series. Alpha and kappa angles were measured using the iTrace aberrometer. All patients also performed a 1-week MCLT. Only patients with a positive MCLT underwent surgery. Visual outcome (UCVA) was obtained in the 1-year follow-up. We assessed the preoperative distribution of angle values within MCLT positive and negative patient groups. RESULTS: Two hundred seventeen eyes (111 patients) were included. Mean age was 56.4 years (SD 5.6) and 46.9% were female. In 71 eyes (38 patients), MCLT was positive. Of them, 12 eyes (17%) had an angle alpha and angle kappa ≥ 0.5mm. Of 146 eyes (73 patients) who refrained from surgery due to a negative MCLT, 71 eyes (48.6%) had both angles small (<0.5mm). In the 1-year follow-up, UCVA improved by 0.68 logMAR (SD 0.51; p<0.001) from baseline. Eyes with both small angle alpha and kappa sizes improved by 0.78 logMAR (SD 0.56), as did eyes with high (≥0.5mm) angle sizes (0.82 logMAR (SD 0.53). UCVA of eyes (n=24) with high alpha but low kappa sizes improved less (-0.31 logMAR (SD 0.13; p=0.019)). CONCLUSION: Four out of five patients with a positive MCLT also had correspondingly small angle values. One-half of patients with low preoperative angle values refrained from surgery due to a negative MCLT result. One-year visual acuity improvement was substantial and independent from angle sizes.

Cold evoked potentials: Acquisition from cervical dermatomes.

INTRODUCTION: Cold evoked potentials (CEPs) represent a novel technique to assess the integrity of cold-specific pathways within the somatosensory system. So far an objective assessment of these pathways has not been implemented into the clinical routine. Specifically, CEPs may help to elucidate the pathophysiological underpinnings of altered cold processing in neurological diseases. OBJECTIVE: To test feasibility and test-retest reliability of CEPs within two cervical dermatomes, including recording sites in glabrous and hairy skin, in order to facilitate the transition into clinical practice. METHODS: Twenty healthy subjects received 15 cold stimuli applied by a thermode either at the hand dorsum (C6 dermatome, hairy skin), the shoulder (C4 dermatome, hairy skin) or the thenar eminence (C6 dermatome, glabrous skin). Stimuli were applied from a baseline temperature of 30°C down to a destination temperature of 25°C at a rate of 20°C/s. N2 latencies and N2P2 amplitudes were recorded at the vertex using a surface electroencephalogram and test-retest statistics were calculated. RESULTS: Slight, innocuous cooling (Δ5°C) from a baseline temperature of 30°C elicited a brief percept of cooling and generated a vertex potential (N2P2) in most subjects. The latency of the vertex response is consistent with A-delta fiber activation. Based on test-retest analyses (i.e., intraclass correlation coefficients (ICCs) and Bland-Altman analyses) reliability is best within the C4 dermatome and for stimulation of hairy skin. ICCs display fair to substantial (ICCs from 0.51-0.81) reliability for amplitudes across all stimulation sites, possibly due to floor effects. CEPs latencies, however, were only poorly reliable (ICCs from -0.13 to 0.31). CONCLUSION: The acquisition of CEPs from cervical dermatomes is feasible. Since involvement of cold-specific pathways is relevant for several pathologies in clinical neurology, the application of CEPs may complement existing techniques like contact heat and laser stimulation in the assessment of peripheral and central nervous system disorders. Future studies employing different stimulation paradigms using faster cooling are warranted in order to improve the signal-to-noise ratio.

Normative data for the segmental acquisition of contact heat evoked potentials in cervical dermatomes.

Contact heat evoked potentials (CHEPs) represent a neurophysiological approach to assess conduction in the spinothalamic tract. The aim of this study was to establish normative values of CHEPs acquired from cervical dermatomes (C4, C6, C8) and examine the potential confounds of age, sex, and height. 101 (49 male) healthy subjects of three different age groups (18-40, 41-60, and 61-80 years) were recruited. Normal (NB, 35-52 °C) followed by increased (IB, 42-52 °C) baseline stimulation protocols were employed to record CHEPs. Multi-variate linear models were used to investigate the effect of age, sex, and height on the CHEPs parameters (i.e., N2 latency, N2P2 amplitude, rating of perceived intensity). Compared to NB, IB stimulation reduced latency jitter within subjects, yielding larger N2P2 amplitudes, and decreased inter-subject N2 latency variability. Age was associated with reduced N2P2 amplitude and prolonged N2 latency. After controlling for height, male subjects had significantly longer N2 latencies than females during IB stimulation. The study provides normative CHEPs data in a large cohort of healthy subjects from segmentally examined cervical dermatomes. Age and sex were identified as important factors contributing to N2 latency and N2P2 amplitude. The normative data will improve the diagnosis of spinal cord pathologies.