Grayscale Units Research Articles

Assessment of corneal backward light scattering in the healthy cornea and factors affecting corneal transparency.

To quantify normative corneal optical density (COD) values of healthy individuals and to investigate alterations in the COD in relation to their ocular and demographic characteristics. Prospective, cross-sectional, and observational. In total, 588 eyes from 588 healthy participants with clear corneas were consecutively enrolled. Corneal densitometry values expressed in standardized grayscale units (GSU) from different corneal layers and zones obtained using the rotating Pentacam Scheimpflug system were analyzed. The mean (SD) COD over the 12-mm diameter area was 14.4 ± 2.74 GSU. A significant positive correlation was found between the participants' age and the total COD (r = 0.756, P < .001). No significant differences were found between males and females with respect to COD (P = .51). No significant correlation was found between the COD measurements and refractive error, pachymetry, and keratometry (P > .05 for all comparisons). On the other hand, COD was negatively correlated with white-to-white (WTW) corneal diameter (r = - 0.415, P < .001). Moreover, the WTW corneal diameter was correlated with the COD in any zone and layer of the cornea (P < .05 for all comparisons). Wide variations in COD can be detected even in corneas deemed clinically clear. Age and corneal diameter that seem to influence corneal transparency should be taken into account when evaluating corneal backscatter.

Corneal Densitometry after Femtosecond Laser-Assisted In Situ Keratomileusis (Fs-LASIK) and Small Incision Lenticule Extraction (SMILE)

ABSTRACTPurpose: To compare corneal densitometry values after Femtosecond Laser-Assisted In Situ Keratomileusis (Fs-LASIK) and Small Incision Lenticule Extraction (SMILE) using Scheimpflug Imaging.Methods: Our retrospective clinical trial included a total of 146 eyes where 57 eyes underwent Fs-LASIK and 89 eyes underwent SMILE. Examinations with a Pentacam Scheimpflug device (Oculus, Wetzlar, Germany) were performed before surgery, 1 week, 1 month, 3 months, 6 months, and 1 year after surgery. Detailed data of all four concentric optical zones were acquired – central 0–2 mm, 2–6 mm, 6–10 mm and 10–12 mm. The cornea was divided into anterior 120 µm, middle and posterior 60 µm sections. Values were analyzed during follow-up comparing Fs-LASIK and SMILE.Results: No statistically significant differences in corneal density were detected. The central 0–2 mm anterior area demonstrated a mean 1-year value of 17.99 grayscale units (GSU) ± 0.89 (range 16.60–19.50) after Fs-LASIK versus 17.96 GSU ± 0.98 (range 16.40–20.00) after SMILE. Three months after surgery there was a slight temporary density increase in the 6–10 mm anterior annulus in the LASIK group – 22.19 (SD = 3.99, range: 15.60–30.50) compared to SMILE – 20.39 (SD = 3.79, range 14.70–36.30).Conclusion: There were no statistically significant short or long-term differences in postoperative corneal densitometry after LASIK and SMILE, demonstrating SMILE is not inferior in this regard. Known delayed visual acuity recovery after SMILE in relation to LASIK could not be correlated with changes in corneal density.

Clinical observation on corneal transparency after small incision lenticule extraction surgery

Objective: To evaluate the changes of corneal transparency over the 1-year period after small incision lenticule extraction (SMILE) according to corneal Scheimpflug densitometry. Methods: Prospective cohort study. Fifty-five patients (100 eyes) with myopia (19 male and 36 female, aged 18 to 39 years with average of 24) who underwent SMILE and regular follow-up for at least 1 year at Tianjin Eye Hospital were enrolled. Examinations took place before SMILE and postoperatively at 1 day, 1 week, and 1, 3, 6, and 12 months. The preoperative spherical equivalent of surgical refractive correction was (-5.75±1.64) D. Corneal densitometry (CD) data were calculated automatically by the Pentacam Scheimpflug system and expressed in gray scale units (GSU), from 0 (completely transparent) to 100 (completely opaque). During the analysis of corneal densitometry, the average corneal optical density of three concentric radial zones centered on the apex of the cornea ≤2 mm, >2 mm and ≤6 mm, >6 mm and ≤10 mm diameter) were applied, and three layers were defined according to different corneal depths (the anterior 120 μm as 1st layer, and the posterior 60 μm as 3rd layer, and the center part between them of the cornea as 2nd layer). The automatic release mode was applied in order to avoid operator-induced errors. The preoperative and postoperative values in different corneal layers and different concentric radial zones were compared using Kruskal-Wallis. Results: Ninty-three eyes(93%) of all eyes achieved uncorrected distance visual acuity (UCVA) of 0.8 or better on the first day postoperatively, and 96% (96 of 100 eyes) achieved UCVA of 0.8 or better in the first week postoperatevely, and all eyes 100% (100 of 100 eyes) achieved UCVA 0.8 or better until the end of our follow-up (in 1 year postoperatively). In general, the difference preoperative and postoperative corneal average optical density is of no statistical significance (χ(2)=8.446, P=0.207), specifically, the overall postoperative CD increased in the first week after surgery (1 day to 15.90, 1 week to 15.65), and then decreased to the equivalent of baseline levels and maintained such level until 6 months after surgery (1 month to 15.60; 3 month to 15.50, 6 month to 15.55), though at the 12-month follow-up, densitometry values had spiked significantly again (12 month, 15.90). The difference between the preoperative and postoperative CD values in the central two zones (≤2 mm, >2 mm and ≤6 mm), but not the outer (>6 mm and ≤10 mm), were of statistical significance (χ(2)=61.961, 52.397, P<0.000). When subdivided by corneal layer, significant changes in CD were detected in the anterior 120 μm layer (χ(2)=27.774, P<0.000). The CD increased significantly (i.e., corneal transparency decreased) as compared to the preoperative baseline on the first postoperative day, and lasted through the first week. There were no significant changes in the CD of the central layer (χ(2)=0.918, P=0.986). Significant increases in the posterior 60 μm of the cornea after surgery were found only at the 6-month and 1-year follow-up examinations (χ(2)=17.469, P=0.008). No correlation was found in the preoperative refractive error, ablation depth, postoperative UCVA and the CD. The CD at 6 months was found negatively correlated with SE at 6 months (r=-0.219, P=0.028). Conclusions: SMILE reduced corneal transparency temporarily and primarily within the surgically altered area, however such change has no significant correlation with the ablation depth, SE, and the postoperative UCVA. Transparency recovered within a month, but patients should be monitored for at least 1 year. (Chin J Ophthalmol, 2018, 54: 27-32).

Scheimpflug Densitometry After DMEK Versus DSAEK-Two-Year Outcomes.

To compare the course of Scheimpflug corneal densitometry (CD) after Descemet membrane endothelial keratoplasty (DMEK) versus Descemet stripping automated endothelial keratoplasty (DSAEK). Fifty-four DMEK and 25 DSAEK cases without previous corneal surgery, complicated intraoperative or postoperative course, or vision-limiting ocular comorbidities were included. Pseudophakic eyes of age-matched subjects were recruited as controls (n = 20). Scheimpflug CD of the optically relevant zones (0-2 and 2-6 mm), best-corrected visual acuity (BCVA), endothelial cell density, and central corneal thickness were evaluated preoperatively and at 3, 6, 12, and 24 months postoperatively. CD of the optical zone decreased from 34.4 ± 9.4 grayscale units (GSU) before to 19.2 ± 2.7 GSU at 24 months after DMEK. Respectively, CD decreased from 34.0 ± 13.4 GSU before to 21.2 ± 2.5 GSU at 24 months after DSAEK. Mean central CD in group 3 was 18.1 ± 1.3 GSU. Compared with DSAEK, DMEK cases showed lower central CD at 3 and 6 months (P ≤ 0.012) but not at 12 and 24 months postoperatively. DSAEK showed higher CD values throughout the postoperative period compared with healthy controls (P < 0.001). DMEK showed higher CD compared with controls at 3, 6, and 12 but not at 24 months after surgery (P = 0.152). Postoperative BCVA was significantly better after DMEK for every examination time point. No difference in endothelial cell density was found between DMEK and DSAEK at any time point. DMEK showed lower CD and better BCVA compared with DSAEK in the first 6 postoperative months. Notably, although CD reached similar levels in the midterm after both DMEK and DSAEK, BCVA remained significantly better after DMEK.

Analysis of the modifications of MRI signal of the brachial plexus of rats: Comparative study before and after freezing/thawing

The aim of this study was to compare the MRI signal of the brachial plexus and surrounding muscles before and after freezing/thawing on a murine model. A first MRI going through the brachial plexuses of 5 healthy Wistar rats was performed immediately post-mortem. A second MRI was performed after freezing at -30°C and then thawing at 20°C for 24hours. All MRI images were segmented to make nerve and muscular structures appear and calculate the average intensity of the MRI signal using the program ImageJ. The average nerve and muscular MRI signals were compared before and after freezing/thawing and rated in grayscale units between 0 and 255. The average intensity of the MRI signal of nerve structures was 40.315 grayscale units before freezing and 31.943 after freezing/thawing. The average intensity of the MRI signal of muscular structures was 25.44 grayscale units before freezing and 35.710 after freezing/thawing. Our results have shown that the intensity of the MRI signal of the brachial plexus was higher before freezing/thawing. The intensity of the MRI signal of muscles was lower than the intensity of the brachial plexus before freezing/thawing and higher after freezing/thawing in muscles than in brachial plexus. The MRI could be used in clinical practice to monitor the reinnervation after frozen nerve allografts.

Comparison of Sub-Bowman Keratoplasty Laser In situ Keratomileusis Flap Properties between Microkeratome and Femtosecond Laser.

Background:Since thin and high-quality flaps produce more satisfactory surgical outcomes, flaps created by mechanical microkeratomes are more economical as compared with femtosecond lasers, and no Iranian study has concentrated laser in situ keratomileusis (LASIK) flap peculiarities between Moria Sub-Bowman keratoplasty (SBK) microkeratomes and LDV femtoseconds, the present study compares and contrasts them.Materials and Methods:This cross-sectional study was done on all patients who underwent LASIK surgery 1-month before this study. Thirty eyes were divided into per group. Flaps in the first group and second group were created, respectively, using Moria SBK microkeratome and LDV femtosecond laser. The other stages of LASIK were done equally in both groups. One month after surgery, the thickness of flaps was measured by anterior segment optical coherence tomography in five regions of flaps. Corneal anterior density was calculated and recorded 1-month after surgery using pentacam and by employing optical densitometry in a distance in the limit range of 0–6 mm from cornea center. Densitometry measurements were obtained and expressed in standardized grayscale units (GSUs).Results:Postsurgery densitometry results reveal that anterior densities of cornea in limit range of 0–2 mm in groups of LDV femtosecond laser and Moria microkeratome are 21.35 ± 0.87 GSU and 22.85 ± 1.25 GSU, respectively. Accordingly, these two groups are significantly different in this regard (P < 0.001). Moreover, anterior densities of the cornea in the limit range of 2–6 mm in these groups are 19.66 ± 0.99 GSU and 20.73 ± 1.24 GSU, respectively. Accordingly, these two groups are significantly different in this regard (P = 0.04). There is a lower mean of flap thickness in the case of LDV femtosecond laser.Conclusion:Femtosecond laser method is greatly preferred as compared with Moria microkeratome because of greater homogeneity in flap thickness, smaller thickness, and lower density in optical zone.

Primary Outcomes of Accelerated Epithelium-Off Corneal Cross-Linking in Progressive Keratoconus in Children: A 1-Year Prospective Study.

Purpose To evaluate corneal transparency following accelerated collagen cross-linking (ACXL) in pediatric keratoconus. Design A prospective interventional case series. Methods This study included 47 eyes (25 patients), aged 9–14 years, with documented progressive keratoconus. After applying 0.1% riboflavin drops, ACXL was performed. Assessment included corrected distance visual acuity (CDVA), uncorrected visual acuity (UCVA), corneal haze, and corneal densitometry in grayscale units (GSU). Result The mean baseline and corneal densitometry peaked at 3 months post-ACXL while central and posterior densitometry showed a statistically significant increase (P < 0.05) and peaked at 8 months postoperatively. By 12 months, densitometry in all corneal layers (P ≥ 0.99) and concentric zones (P ≥ 0.97) reached near baseline values. Slit-lamp graded haze peaked at 1 month to 1.82 ± 0.65 (P < 0.05) and declined to near baseline at 12 months (0.39 ± 0.58). There was a statistically significant increase in the mean UCVA and CDVA at 12 months. Conclusion Total and anterior corneal densitometry peaked after 3 months, while central and posterior densitometry peaked after 8 months. Maximum haze was at 1 month post-ACXL. All corneal layers, concentric zone densitometry and haze reached near baseline values after 1 year. Scheimpflug densitometry showed weak correlation with CDVA over the 12-month follow-up period (r = −0.193).

Two-Year Course of Corneal Densitometry After Descemet Membrane Endothelial Keratoplasty

To investigate the 2-year course of corneal densitometry following Descemet membrane endothelial keratoplasty (DMEK) for Fuchs endothelial dystrophy (FED). Retrospective, interventional case series. Densitometry values (corneal light backscatter in grayscale units) measured by Scheimpflug-based imaging and clinical records of 160 eyes of 160 patients undergoing DMEK for FED were reviewed. Outcome measures included densitometry data in 4 corneal layers (anterior layer [AL], central layer [CL], posterior layer [PL], and total layer [TL]) and 2 annuli (central annular zone 0-2mm and peripheral zone 2-10mm), central corneal thickness (CCT), best spectacle-corrected visual acuity (BSCVA), and endothelial cell density (ECD) prior to DMEK and at 1, 3, 6, 12, and 24months postoperatively. Corneal densitometry decreased in all 4 layers over 2 years after DMEK surgery. Regarding TL 0-2mm, the reduction of corneal light backscatter was statistically significant for all follow-up time points compared with preoperative values (P < .001) and compared in between follow-up periods (P ≤ .010). Corneal light backscatter reduction was significantly higher in the center (0-2mm) than in the periphery (2-10mm) for all layers at 12 and 24months (P ≤ .002). ECD and CCT did not correlate with corneal densitometry, whereas BSCVA correlated moderately for TL 0-2mm (P= .026; r= 0.449) and TL 2-10mm (P= .001; r= 0.585) at 12months. Corneal light backscatter showed a significant reduction after DMEK surgery in Fuchs endothelial dystrophy over a period of 2 years, more pronounced in the corneal center, apparently in association with visual acuity improvement.

Corneal densitometry and its correlation with age, pachymetry, corneal curvature, and refraction

To determine normative corneal densitometry values in relation to age, sex, refractive error, corneal thickness, and keratometry, measured using the Oculus Pentacam system. Three hundred and thirty-eight healthy subjects (185 men; 153 women) with no corneal disease underwent an exhaustive ocular examination. Corneal densitometry was expressed in standardized grayscale units (GSU). The mean corneal densitometry over the total area was 16.46±1.85 GSU. The Pearson correlation coefficient for total densitometry was r=0.542 (p<0.001). Statistically significant differences were found between men and women for the total area (p=0.006), with readings of 16.22±1.54 GSU and 16.60±1.83 GSU, respectively. When the cornea was divided into layers of different depths, a significant correlation was found for all layers and age: r=0.447 (p<0.001), r=0.563 (p<0.001), and r=0.520 (p<0.001) for the anterior, central, and posterior layers, respectively. However, when the cornea was divided into concentric annuli starting from the center of the cornea, densitometry was strongly correlated only with age in the 6-10-mm annulus (p<0.001). Neither mean keratometry nor spherical equivalent was correlated with corneal densitometry in any zone of the cornea (p>0.05). This is the first report of normative corneal densitometry values in relation to keratometry, corneal thickness, and spherical equivalent measured with the latest Oculus Pentacam software. Corneal densitometry increases with age, but corneal keratometry and refractive parameters do not affect light scattering in the human cornea.

Corneal Scheimpflug Densitometry Following Photorefractive Keratectomy in Myopic Eyes.

To evaluate the modification of corneal optical densitometry following photorefractive keratectomy (PRK) using Scheimpflug topography. Corneal densitometry (0 to 100 grayscale units [GSU]), pachymetry, and keratometry were evaluated using a rotating Scheimpflug camera (Pentacam HR; Oculus Optikgeräte, GmbH, Wetzlar, Germany) at baseline and 1 and 3 months following PRK in myopic patients. Subjective refraction, uncorrected distance visual acuity, corrected distance visual acuity, and corneal haze (0 to 4 on common subjective scale) were evaluated preoperatively at baseline, 1 month, and 3 months. The study included 75 eyes (38 right eyes, 37 left). The preoperative mean spherical equivalent and cylinder were -2.28 ± 1.24 and 0.92 ± 0.65 diopters (D), respectively. Maximal corneal densitometry (central 4 mm) was 27.44 ± 1.93 GSU at baseline. At 1 month postoperatively, corneal haze with a mean clinical grade of 0.54 ± 0.45 (P < .0001) was observed, associated with corneal densitometry increased to 29.69 ± 5.16 GSU (P > .05). At 3 months postoperatively, mean clinical haze decreased to 0.11 ± 0.24 (P < .0001) and was associated with a significant decrease (P < .0001) in maximal densitometry (25.13 ± 3.42 GSU). Corneal densitometry could represent a useful objective measurement of postoperative mild corneal haze and aid in the rating and follow-up of refractive surgery. [J Refract Surg. 2016;32(11):788-791.].

Effect of preoperative factors on visual acuity, corneal flattening, and corneal haze after accelerated corneal crosslinking

To evaluate the preoperative characteristics that might influence corneal flattening, visual acuity, and corneal haze after accelerated (9mW/cm2) corneal collagen crosslinking (CXL). Ulucanlar Eye Hospital, Ankara, Turkey. Retrospective case series. Accelerated corneal CXL was performed in eyes with progressive keratoconus. Preoperative characteristics included age, sex, uncorrected distance visual acuity and corrected distance visual acuity (CDVA), maximum keratometry (K), corneal thickness, corneal hysteresis, the corneal resistance factor, cone location, and densitometry values. Regression analysis was performed to determine the predictive factors for accelerated corneal CXL outcomes. The study included 162 eyes of 146 patients with a mean age of 19.3years±4.4 (SD). There was 0.20 logMAR improvement in CDVA (P=.011), 1.85 diopter flattening in maximum K(P<.001), and 5.84 grayscale unit increase in densitometry (P<.001) at 1year. Multivariate analysis found that preoperative CDVA was a predictive factor for CDVA improvement (ß coefficient, 0.233; 95% confidence interval [CI], -0.054 to 0.477; P=.003). Preoperative maximum K was a predictive factor for corneal flattening (ß coefficient, 0.506; 95% CI, 0.185 to 0.681; P<.001). Univariate analysis found that preoperative densitometry was a predictive factor for increasing corneal densitometry (ß coefficient, 0.466; 95% CI, -0.122 to 0.683; P=.001) and corneal scar formation (ß coefficient, 0.256; 95% CI, 0.012 to 0.421; P=.041). Patients with a worse preoperative CDVA and higher maximum K were most likely to have improvement after accelerated CXL. Patients with high preoperative densitometry were most likely to have scar formation after the procedure. None of the authors has a financial or proprietary interest in any material or method mentioned.

Corneal Densitometry: A New Technique for Objective Assessment of Corneal Clarity in Pseudoexfoliation Syndrome.

To evaluate the corneal clarity quantitatively by using corneal densitometry in patients with pseudoexfoliation syndrome (PES) and to compare the results with those of healthy control subjects. Corneal densitometry measurement of patients with bilateral PES and healthy control subjects was carried out by Scheimpflug corneal topography (PentacamHR). For densitometry analysis, the 12-mm diameter area of the cornea was subdivided into 4 concentric radial zones (0 to 2, 2 to 6, 6 to 10, 10 to 12 mm) and also into anterior, central, and posterior layers based on corneal depth. Corneal densitometry measurements were expressed in gray scale unit and only the data from the right eyes of subjects were used for statistical analysis. A total of 176 patients [89 with PES (52 male, 37 female) and 87 healthy control subjects (52 male, 35 female)] were enrolled in the study. There was no significant difference between the mean corneal densitometry values at anterior 120 μm, central, and posterior 60 μm of the cornea in all concentric radial zones (P>0.05 for all). Corneal densitometry was positively correlated with age in both groups (r=0.558, P<0.001 in PES; r=0.584, P<0.001 in control group). Corneal densitometry that enables the objective assessment of corneal clarity was found to be similar in patients with bilateral PES and healthy control subjects. It is positively correlated with increasing age in both groups. However, microstructural changes that contribute to the corneal densitometry and the clinical relevance of these findings should be further highlighted in future studies.

Abstract 116: Revascularization but Not Supervised Exercise Therapy Prevents Progression of Fibrosis in the Gastrocnemius of Patients With Peripheral Artery Disease While Improving Limb Function

Introduction: Patients with peripheral artery disease (PAD) develop myofiber degeneration and fibrosis in their ischemic lower extremities, along with limb dysfunction. Walking performance improves with revascularization and exercise therapy, but effects on the myopathy are unknown. We previously showed fibrosis progresses with PAD and positively correlates with expression of vascular transforming growth factor-beta 1 (TGF-β1), a cytokine that stimulates collagen deposition. Hypothesis: We hypothesize that revascularization (RVS) and supervised exercise therapy (EXE) improve limb function in association with improved TGF-β1 dependent fibrosis. Methods: Gastrocnemius biopsies were collected from PAD patients (Fontaine Stage II; N=56) at baseline and 6 months after RVS (N=20), EXE (N=19), or no intervention (CTL; N=17). TGF-β1 expression was measured as grey scale units (gsu) by quantitative fluorescence microscopy of paraffin-embedded gastrocnemius sections. Collagen abundance was measured as optical density by quantitative multi-spectral bright-field microscopy of Masson Trichrome stained paraffin sections. Six Minute Walking Distance (SMWD), in meters, and Peak Walking Time (PWT), in seconds, were determined at baseline and 6 months. Relationships among TGF-β1, collagen, and limb function were assessed. Results: TGF-β1 expression and collagen density increased in CTL and EXE but not RVS patients. SMWD and PWT increased among RVS patients. PWT but not SMWD increased among EXE patients. SMWD and PWT were unchanged among CTL patients. The data are summarized in Table 1. Conclusions: RVS and EXE improved walking performance of patients with PAD, but only RVS prevented progression of fibrosis in the gastrocnemius of these patients. Over the same 6-month period, fibrosis increased in CTL muscle but was not sufficient to alter walking performance. The data suggest that benefits to the PAD leg may be greater with RVS compared to EXE.

Quadriceps Muscle Quality Does Not Reflect Self-report Or Muscle Function In Individuals With Acl Reconstruction

Chronic quadriceps dysfunction following anterior cruciate ligament reconstruction (ACLR) leads to disability and has been implicated as a risk factor for knee osteoarthritis (OA). However, the most appropriate quadriceps function assessment for identifying individuals at heightened risk of OA and disability is unclear. Quadriceps muscle quality (QMQ) assessed via ultrasound imaging is associated with quadriceps strength and functional ability in the elderly, but has yet to be evaluated following ACLR. PURPOSE: To compare QMQ between limbs and evaluate relationships between QMQ, quadriceps function, and self-report function in individuals with ACLR. METHODS: Twenty-six individuals with unilateral ACLR (73% females; age = 23 ± 3 yr; time since ACLR = 56 ± 45 months; International Knee Documentation Committee Index [IKDC] = 87 ± 9) volunteered for this study. QMQ was calculated as the echo intensity of cross-sectional ultrasound images of the rectus femoris (RF) and vastus lateralis (VL), and averaged as a composite quadriceps value. Isometric (peak torque and rate of torque development) and isokinetic (peak torque and power at 180°/s) quadriceps function was assessed in the ACLR limb and normalized to body mass. QMQ was compared between limbs via paired t-tests, and relationships between QMQ, quadriceps function, and self-report function (IKDC) were evaluated via Pearson correlations. RESULTS: QMQ did not differ between limbs for the RF (arbitrary grayscale units: 110 ± 8 vs. 110 ± 7, p = 0.472), VL (112 ± 9 vs. 113 ± 9, p = 0.203), or quadriceps composite (111 ± 8 vs. 112 ± 7, p = 0.326), and was not correlated with any quadriceps function index (r = -0.283 - 0.122, p > 0.05). IKDC was not correlated with QMQ of the VL (r = -0.093, p = 0.332) or quadriceps composite (r = -0.242, p = 0.127), but poorer RF QMQ was associated with poorer self-report function (r = -0.376, p = 0.035). CONCLUSIONS: Poor QMQ of the RF is indicative of poor self-report function, but QMQ does not differ between limbs and is not associated with quadriceps function in individuals with ACLR. These data suggest that QMQ has limited clinical application for identifying individuals at heightened risk of OA and disability following ACLR. Previous reports of associations between QMQ and muscle function in elderly subjects likely reflect age-related sarcopenia.

Abstract 13651: Angiotensin-Converting Enzyme Inhibitors Preserve Limb Function and Decrease Myofibrosis and Oxidative Damage in the Calf Muscle of Patients With Peripheral Artery Disease

Introduction: A six-month treatment with the Angiotensin-Converting Enzyme Inhibitor (ACEI) Ramipril improved the walking ability of Peripheral Artery Disease (PAD) patients, but the mechanism remains unknown. ACEI have been shown to reduce fibrosis in heart and kidney and improve arterial compliance. We have identified a myopathy in calf muscles of PAD patients, characterized by fibrosis and increased TGF-β1 produced exclusively in smooth muscle cells (SMC) of microvessels. These events were linked to myofiber oxidative damage and reduced myofiber cross-sectional area. Hypothesis: The myopathy of PAD patients taking ACEI is improved compared to patients who are not taking ACEI and this improvement is associated with improved walking ability. Methods: Calf muscle biopsies, from PAD patients (Fontaine Stage II) taking ACEI (ACEI+) and those who were not (ACEI-), were fixed, embedded in paraffin, sectioned at 4 microns and slide mounted. Oxidative damage (carbonyl groups) (N=13 for ACEI- and 22 for ACEI+) and TGF-β1 (N=13 for ACEI- and 20 for ACEI+) were analyzed by quantitative fluorescence microscopy and expressed as grey scale units (gsu). Myofiber cross-sectional area was determined from fluorescence-labeled sarcolemma. Fibrosis was determined as collagen density (gsu) by multi-spectral analysis of slide specimens (N=13 for ACEI- and 20 for ACEI+) stained with Mason Trichrome. Limb function was assessed by the six-minute walking distance (N=28 for ACEI- and 20 for ACEI+). Results: Compared to ACEI- patients, ACEI+ patients had reduced TGF-β1 (4.25 gsu +/- 0.69 vs. 1.51 gsu +/- 0.23; p = 0.001) and decreased collagen density (2067 gsu +/- 88 vs. 1671 gsu +/- 51; p &lt; 0.001). Carbonyl adducts were reduced in myofibers of ACEI+ compared to ACEI- patients (1584 gsu +/- 55 vs. 1779 gsu +/- 58; p = 0.019) and myofiber cross sectional area was increased (4629 μm2 +/- 285 vs. 3816 μm2 +/- 267; p = 0.023). Six-minute walking distance was greater in ACEI+ compared to ACEI- patients (333 m +/- 20 vs. 266 m +/- 16; p = 0.011). Conclusions: Improved walking distance of PAD patients taking ACEI is associated with improved calf muscle myopathy, determined as reduced TGF-β1 production, collagen density, and myofiber oxidative damage, and increased myofiber cross-sectional area.

Abstract 40: Increased Expression of Transforming Growth Factor-Beta 1 in the Gastrocnemius of Patients with Peripheral Artery Disease is a Localized Response in the Ischemic Muscle

Introduction: Patients with peripheral artery disease (PAD) develop a myopathy in their ischemic lower extremities, which is characterized by myofiber degeneration and myofibrosis. We previously showed that increased expression of transforming growth factor-beta 1 (TGF-β1), which stimulates collagen deposition, is associated with increased fibrosis in PAD gastrocnemius. Expression was localized to the microvasculature, suggesting that elevated TGF-β1 may be a systemic condition rather than a local response in PAD patients. Hypothesis: We hypothesize that increased expression of TGF-β1 in PAD gastrocnemius is a localized response in the ischemic muscle, which contributes to the myofibrosis of PAD. To test this hypothesis, we evaluated TGF-β1 expression and collagen deposition in the gastrocnemius of the diseased and contralateral legs of patients with unilateral PAD. Methods: Gastrocnemius biopsies were collected from both limbs of PAD patients with unilateral disease (n=10). Muscle homogenates were analyzed by qPCR for TGF-β1 transcripts expressed as fold change in relation to myosin heavy chain. TGF-β1 in paraffin-embedded gastrocnemius sections was labeled for fluorescence analysis and expression measured as grey scale units (gsu) by quantitative fluorescence microscopy. Sections were stained by Masson Trichrome and collagen density was measured by spectral analysis. Results: TGF-β1 transcripts were increased in the diseased compared to contralateral muscle (mean +/- s.e.; 4.65 +/- 0.95 vs. 0.61 +/- 0.15; p = 0.007) as was TGF-β1 protein expression (919 +/- 169 gsu vs. 593 gsu +/- 115; p = 0.013). Increased TGF-β1 expression was accompanied by increased collagen deposition in the diseased versus contralateral muscle (2162 gsu +/- 99 vs. 1739 gsu +/- 73; p = 0.007). Conclusions: TGF-β1 expression in PAD gastrocnemius does not represent a systemic condition that may interact with local ischemic events and thereby contribute to PAD myopathy. Instead, it is an integral and localized response in ischemic muscle, which stimulates fibrosis in the diseased muscle. Consequently, successful intervention in the fibrotic response of PAD muscle may be dependent on addressing tissue hypoxia or metabolic shifts associated with ischemia.

Improved Potentiometric and Optic Sensitivity of Polyaniline Film to Dissolved Oxygen by Incorporating Iron-Porphyrin

Polyaniline (PAn) films can be used in an electrochemical and optical combination system to amplify the optical signal for dissolved oxygen (DO) detection. To further improve the sensitivity of PAn film to DO, an oxygen-sensitive molecule, Fe(III) meso-tetera (4-sulfonatophenyl) porphyrin (FeTSPP) is incorporated into PAn during the film generation. Results show that, after incorporating FeTSPP into the PAn matrix, both optical and potentiometric responses to DO are improved. The optimal optical signal is obtained under the application of −2.5 μA to the modified electrode. Under this applied current, both optical and potentiometric signals show linear relations with the DO concentration within the range of 0.00–4.63 mg L−1, and the sensitivities for optical and potentiometric signals are 4.18 grayscale units mg−1 L and 13.39 mV mg−1 L, respectively.

Treatment Effect and Corneal Light Scattering With 2 Corneal Cross-linking Protocols: A Randomized Clinical Trial.

We describe and evaluate a complementary method to indirectly quantify the treatment effect of corneal cross-linking (CXL). Additional methods to indirectly quantify the treatment effect of CXL are needed. To assess the spatial distribution and the time course of the increased corneal densitometry (corneal light backscatter) seen after CXL with riboflavin and UV-A irradiation. Open-label randomized clinical trial of 43 patients (60 eyes) who were 18 to 28 years of age and had progressive keratoconus and a plan to be treated with CXL at Umeå University Hospital, Umeå, Sweden. The patients were randomized to receive conventional CXL (n = 30) using the Dresden protocol or CXL with mechanical compression of the cornea using a flat rigid contact lens sutured to the cornea during the treatment (CRXL) (n = 30). All participants were followed up during a 6-month period from October 13, 2009, through May 31, 2012. Corneal cross-linking according to the Dresden protocol or CRXL. Change in corneal densitometry after CXL and CRXL for keratoconus. Of the original 60 eyes included, 4 had incomplete data. A densitometry increase was seen after both treatments that was deeper and more pronounced in the CXL group (difference between the groups at 1 month in the center layer, zone 0-2 mm, 5.02 grayscale units [GSU], 95% CI, 2.92-7.12 GSU; P < .001). This increase diminished with time but was still noticeable at 6 months (difference between the groups at 6 months in the center layer, zone 0-2 mm, 3.47 GSU; 95% CI, 1.72-5.23 GSU; P < .001) and was proportional to the reduction in corneal steepness (R = -0.45 and -0.56 for CXL and CRXL, respectively). The degree of corneal light backscatter relates to the reduction in corneal steepness after cross-linking and may become a relevant complement to other methods in evaluating the cross-linking effect, for example, when comparing different treatment regimens. clinicaltrials.gov Identifier: NCT02425150.

Lung ultrasound in the critically ill.

Lung ultrasound, which allows a bedside visualization of the lungs, is increasingly used in critical care. This review aims at highlighting a simple approach to this new discipline. The 10 basic signs are the bat sign (indicating pleural line), lung sliding (yielding the seashore sign), the A line (horizontal artifact), the quad and sinusoid sign indicating pleural effusion regardless of its echogenicity, the tissue-like and shred sign indicating lung consolidation, the B line and lung rockets (artifacts indicating interstitial syndrome), abolished lung sliding with the stratosphere sign, suggesting pneumothorax, and the lung point, indicating pneumothorax. All these disorders were assessed using computed tomography (CT) as a gold standard with sensitivity and specificity ranging from 90 to 100%, allowing us to consider ultrasound as a reasonable bedside gold standard in the critically ill. We use a simple gray-scale unit (without Doppler) with a microconvex probe. Lung ultrasound can be used for diagnosing acute respiratory failure (BLUE protocol), managing acute circulatory failure (Fluid Administration Limited by Lung Sonography protocol), and decreasing the use of radiograph or CT (the Lung Ultrasound in the Critically Ill Favoring Limitation of Radiation project). This can be extended from sophisticated ICUs to more austere settings, from neonates to bariatric adults without adaptation, trauma and several other disciplines (anesthesiology, emergency medicine, pulmonology, etc.). http://links.lww.com/COCC/A8.

Normative Values for Corneal Densitometry Analysis by Scheimpflug Optical Assessment

To describe the normative data for corneal Scheimpflug densitometry based on a cohort of normal participants. A total of 445 healthy participants were recruited for assessment (794 eyes). Left and right eyes were considered separately. All participants were assessed using the corneal densitometry analysis add-on to the standard software of the Oculus Pentacam. Densitometry measurements were obtained and expressed in standardized grayscale units (GSU). All participants were Caucasian; 42% were male and 58% were female. The mean age was 48.0 ± 15.3 years (range, 20.2-84.2 years). Mean corneal densitometry over the 12-mm-diameter area was 19.74 ± 3.89 GSU. When divided by radial zone, densitometry values were lowest in the central zone (16.76 ± 1.87 GSU) and highest in the periphery (27.36 ± 7.47 GSU). There was no difference between central zone and the surrounding 2- to 6-mm annulus (P > 0.05), though the 6- to 10-mm and the 10- to 12-mm zones displayed higher densitometry values (P < 0.001). When divided by depth, the anterior layer displayed the highest densitometry reading of 25.81 ± 5.14 GSU, which was significantly higher than that of both the central (P < 0.001) and the posterior layers (P < 0.001). Changes in corneal densitometry were correlated with age, though not within the central 6-mm-diameter ring. No sex difference was seen within the cohort. This add-on to the standard imaging software allows rapid and objective assessment of the corneal densitometry. We provide normative data that may be used as a reference facilitating research and complementing clinical examination.