Subretinal drusenoid deposits, age-related macular degeneration, and cardiovascular disease

Decades of studies on age-related macular degeneration (AMD), cardiovascular disease and stroke have not found consistent associations between AMD and systemic vascular disease. This study suggests that there is in fact no general relationship, but instead a strong, specific association between only the subretinal drusenoid deposit (SDD) phenotype of AMD on retinal imaging and certain co-existent vascular diseases that are high risk for compromised cardiac output or internal carotid artery stenosis. Future screening initiatives for these high -risk vascular diseases (HRVDs) with fast, inexpensive retinal imaging could make a significant contribution to public health and save lives. Likewise, screening patients with known HRVDs for unrecognized AMD of the SDD form could enable needed treatment and save vision.

Changes in drusen-associated autofluorescence over time observed by fluorescence lifetime imaging ophthalmoscopy in age-related macular degeneration

PURPOSE

To observe fundus autofluorescence (FAF) lifetimes and peak emission wavelength (PEW) of drusen with respect to the pathology of the overlying RPE in the follow-up of AMD-patients.

METHODS

Forty eyes of 38 patients (age: 75.1 ± 7.1 years) with intermediate AMD were included. FAF lifetimes and PEW were recorded by fluorescence lifetime imaging ophthalmoscopy (FLIO). Twenty-six eyes had a follow-up investigation between months 12 and 36, and 10 at months 37-72. AMD progression was retrieved from color fundus photography (CFP) and OCT. Drusen were classified with respect to changes in the overlying RPE into groups no, questionable or faint, and apparent hyperpigmentation based on CFP.

RESULTS

Among the 210 hyperautofluorescent drusen found at baseline, those with hyperpigmentation had longer lifetimes and shorter PEW than those without. Drusen without hyperpigmentation had shorter lifetimes and PEW than neighboring RPE (all p < 0.001) at baseline, but drusen lifetimes increased, and PEW shortened further over follow-up. Eyes, showing AMD progression, had significantly longer FAF lifetimes at baseline than non-progressing eyes: 282 ± 102 ps versus 245 ± 98 ps, p < 0.001 and 365 ± 44 ps vs. 336 ± 48 ps, p = 0.025 for short and long wavelength FLIO channel, respectively.

CONCLUSIONS

Depending on hyperpigmentation properties, drusen show lifetimes and PEW different from that of adjacent RPE which change over the natural history of AMD. This difference and change, however, might reflect progressive dysmorphia of the RPE rather than representing fluorescence of drusen material itself. Nevertheless, the observed FAF changes could make FLIO a useful tool for the early detection of AMD progression risk.

Fluorescence Lifetime and Spectral Characteristics of Subretinal Drusenoid Deposits and Their Predictive Value for Progression of Age-Related Macular Degeneration

Purpose

To measure fundus autofluorescence (FAF) lifetimes and peak emission wavelengths (PEW) of subretinal drusenoid deposits (SDD) in age-related macular degeneration (AMD) and their development over time.

Methods

Fluorescence lifetime imaging ophthalmoscopy (FLIO) was performed in 30 eyes with optical coherence tomography (OCT)-confirmed early or intermediate AMD and SDD. Contrasts of mean lifetimes in short- (SSC) and long-wavelength channels (LSC), PEW, and relative fluorescence intensity were determined as differences of the respective measures at individual SDD and their environment. Measurements were made at baseline and at follow-up intervals 1 (13-36 months) and 2 (37-72 months), respectively.

Results

Of 423 SDD found at baseline, 259, 47, and 117 were hypoautofluorescent, isoautofluorescent, and hyperautofluorescent, respectively. FAF lifetimes of SDD were significantly longer than those of their environment by 14.5 ps (SSC, 95% confidence interval [CI], 13.3-15.7 ps) and 3.9 ps (LSC, 3.1-4.7 ps). PEW was shorter by 1.53 nm (1.07-1.98 nm, all contrasts P < 0.001) with higher contrasts for hyperfluorescent SDD. Over follow-up, SDD tended to hyperautofluorescence (relative intensities increased by 3.4% [95% CI, 2.9%-4.1%; P < 0.001] in follow-up 2). Hyperautofluorescence was associated with disruption of the ellipsoid zone on OCT. Disease progression to late-stage AMD was associated with higher lifetime contrast in SSC (15.9ps [14.2-17.6 ps] vs. 11.7 ps [9.9-13.5 ps], P < 0.001) at baseline.

Conclusions

SDD show longer FAF lifetimes and shorter PEW than their environments. A high lifetime contrast of SDD in SSC might predict disease progression to late-stage AMD.

Prolonged Lifetimes of Histologic Autofluorescence in Ectopic Retinal Pigment Epithelium in Age-Related Macular Degeneration

Purpose

The purpose of this study was to investigate histologic autofluorescence lifetimes and spectra of retinal pigment epithelium (RPE) on the transition from normal aging to RPE activation and migration in age-related macular degeneration (AMD).

Methods

Autofluorescence lifetimes and spectra of 9 donor eyes were analyzed in cryosections by means of 2-photon excited fluorescence at 960 nm. Spectra were detected at 483 to 665 nm. Lifetimes were measured using time-correlated single photon counting in 2 spectral channels: 500 to 550 nm (short-wavelength spectral channel [SSC]) and 550 to 700 nm (long-wavelength spectral channel [LSC]). Fluorescence decays over time were approximated by a series of three exponential functions. The amplitude-weighted mean fluorescence lifetime was determined. Markers for retinoid activity (RPE65) and immune function (CD68) were immunolocalized in selected neighboring sections.

Results

We identified 9 RPE morphology phenotypes resulting in 399 regions of interest (ROIs) for spectral and 497 ROIs for lifetime measurements. RPE dysmorphia results in a shorter wavelength peak of spectral emission: normal aging versus RPE migrated into the retina (intraELM) = 601.7 (9.5) nm versus 581.6 (7.3) nm, P < 0.001, whereas autofluorescence lifetimes increase: normal aging versus intraELM: SSC 180 (44) picosecond (ps) versus 320 (86) ps, P < 0.001; and LSC 250 (55) ps versus 441 (76) ps, P < 0.001. Ectopic RPE within the neurosensory retina is strongly CD68 positive and RPE65 negative.

Conclusions

In the process of RPE degeneration, comprising different steps of dysmorphia and migration, lengthening of autofluorescence lifetimes and a hypsochromic shift of emission spectra can be observed. These autofluorescence changes might provide early biomarkers for AMD progression and contribute to our understanding of RPE-driven pathology.

Combining fluorescence lifetime with spectral information in fluorescence lifetime imaging ophthalmoscopy (FLIO)

Fluorescence lifetime imaging ophthalmoscopy (FLIO) provides information on fluorescence lifetimes in two spectral channels as well as the peak emission wavelength (PEW) of the fluorescence. Here, we combine these measures in an integral three-dimensional lifetime-PEW metric vector and determine a normal range for this vector from measurements in young healthy subjects. While for these control subjects 97 (±8) % (median (interquartile range)) of all para-macular pixels were covered by this normal vector range, it was 67 (±55) % for the elderly healthy, 38 (±43) % for age-related macular degeneration (AMD)-suspect subjects, and only 6 (±4) % for AMD patients. The vectors were significantly different for retinal pigment epithelium (RPE) lesions in AMD patients from that of non-affected tissue (p < 0.001). Lifetime- PEW plots allowed to identify possibly pathologic fundus areas by fluorescence parameters outside a 95% quantile per subject. In a patient follow-up, changes in fluorescence parameters could be traced in the lifetime-PEW metric, showing their change over disease progression.

Optic disc blood perfusion and oxygenation in glaucoma

Purpose

To investigate the haemoglobin concentration and oxygenation in the optic disc in glaucoma patients vs. controls.

Methods

Thirty-one eyes of primary open angle glaucoma patients (mean age: 64.9 ± 2.1 years) and 31 eyes of 31 healthy controls (65.5 ± 2.0 years) were included. Perimetry, optical coherence tomography (OCT), and OCT angiography were performed. Multispectral imaging was used to record the optic disc reflectance at wavelengths 522 nm, 548 nm, 555 nm, 586 nm, and 610 nm, and haemoglobin concentration and oxygenation (SO₂) were calculated from these measures. This was done in the rest and under stimulation of neuronal activity by flicker light.

Results

The haemoglobin concentration was significantly lower (p < 0.001) in the rim (40.0 ± 6.3) and the excavation (35.7 ± 8.0) of the glaucoma patients’ discs than in controls (45.7 ± 7.5). SO₂ was not different in general, but lower in a subgroup of 18 glaucoma patients with ischaemic disc rims than in non-ischaemic ones (median 26.8%, interquartile range (IQR): 29.5% vs. 51.9%, IQR 32.0%, p = 0.02) as well as in controls (41.0%, IQR 30.6%, p = 0.01). Flicker light stimulation significantly increased the haemoglobin concentration in the controls (+ 1.3 ± 3.6, p = 0.048) as well as in the rim of glaucoma discs (+ 2.6 ± 5.0, p = 0.006) and SO₂ in the controls only (+ 15.4 ± 23.6%, p = 0.001). The haemoglobin concentration was significantly correlated with the perimetric mean defect, retinal nerve fibre layer (RNFL) thickness and para-papillary perfusion density.

Conclusions

The optic disc haemoglobin concentration and oxygenation are quantifiable from multispectral imaging and reduced in glaucoma. The correlation of haemoglobin concentration with perfusion density, RNFL thickness and visual field loss indicates its implication in glaucoma pathology.

Spectral and lifetime resolution of fundus autofluorescence in advanced age-related macular degeneration revealing different signal sources

PURPOSE

To determine the fundus autofluorescence (FAF) lifetimes and spectral characteristics of individual drusen and hyperpigmentation independent of those with retinal pigment epithelium (RPE) in geographic atrophy (GA) areas in late-stage age-related macular degeneration (AMD).

METHODS

Three consecutive patients with complete RPE and outer retinal atrophy (cRORA) exhibiting drusen that were calcified or associated with hyperpigmentation were investigated with multimodal non-invasive ophthalmic imaging including colour fundus photography (CFP), optical coherence tomography (OCT), near-infrared reflectance (NIR), blue FAF and fluorescence lifetime imaging ophthalmoscopy (FLIO). Fluorescence lifetimes were measured in two spectral channels (short-wavelength spectral channel (SSC): 500-560 nm and long-wavelength spectral channel (LSC): 560-720 nm).

RESULTS

Drusen lacking RPE coverage, as confirmed by CFP and OCT, had longer FAF lifetimes than surrounding cRORA by 127 ± 66 ps (SSC) and 113 ± 48 ps (LSC, both p = 0.008 in Wilcoxon test, N = 9) and by 209 ± 100 ps (SSC) and 121 ± 56 ps (LSC, p < 0.001, N = 14) in two patients. Hyperpigmentation in CFP in a third patient shows strong FAF with prolonged lifetimes. In the SSC, persistent FAF was found inside cRORA. A crescent-shaped hyperfluorescence in an area of continuous RPE but lacking outer retina was seen in one eye with a history of anti-VEGF treatment.

CONCLUSIONS

Short-wavelength fluorescence in cRORA points to fluorophores beyond RPE organelles. Fluorescence properties of drusen within cRORA differ from in vivo drusen covered by RPE. These limited findings from three patients give new insight into the sources of FAF that can be further elucidated in larger cohorts.

Spectral fundus autofluorescence peak emission wavelength in ageing and AMD

PURPOSE

To investigate the spectral characteristics of fundus autofluorescence (FAF) in AMD patients and controls.

METHODS

Fundus autofluorescence spectral characteristics was described by the peak emission wavelength (PEW) of the spectra. Peak emission wavelength (PEW) was derived from the ratio of FAF recordings in two spectral channels at 500-560 nm and 560-720 nm by fluorescence lifetime imaging ophthalmoscopy. The ratio of FAF intensity in both channels was related to PEW by a calibration procedure. Peak emission wavelength (PEW) measurements were done in 44 young (mean age: 24.0 ± 3.8 years) and 18 elderly (mean age: 67.5 ± 10.2 years) healthy subjects as well as 63 patients with AMD (mean age: 74.0 ± 7.3 years) in each pixel of a 30° imaging field. The values were averaged over the central area, the inner and the outer ring of the ETDRS grid.

RESULTS

There was no significant difference between PEW in young and elderly controls. However, PEW was significantly shorter in AMD patients (ETDRS grid centre: 571 ± 26 nm versus 599 ± 17 nm for elderly controls, inner ring: 596 ± 17 nm versus 611 ± 11 nm, outer ring: 602 ± 16 nm versus 614 ± 11 nm). After a mean follow-up time of 50.8 ± 10.8 months, the PEW in the patients decreased significantly by 9 ± 19 nm in the inner ring of the grid. Patients, showing progression to atrophic AMD in the follow up, had significantly (p ≤ 0.018) shorter PEW at baseline than non-progressing patients.

CONCLUSIONS

Peak emission wavelength (PEW) is related to AMD pathology and might be a diagnostic marker in AMD. Possibly, a short PEW can predict progression to retinal and/or pigment epithelium atrophy.

Progressive Dysmorphia of Retinal Pigment Epithelium in Age-Related Macular Degeneration Investigated by Fluorescence Lifetime Imaging

Purpose

The purpose of this study was to observe changes of the retinal pigment epithelium (RPE) on the transition from dysmorphia to atrophy in age-related macular degeneration (AMD) by fluorescence lifetime imaging ophthalmoscopy (FLIO).

Methods

Multimodal imaging including color fundus photography (CFP), optical coherence tomography (OCT), fundus autofluorescence (FAF) imaging, and FLIO was performed in 40 eyes of 37 patients with intermediate AMD and no evidence for geographic atrophy or macular neovascularization (mean age = 74.2 ± 7.0 years). Twenty-three eyes were followed for 28.3 ± 18.3 months. Seven eyes had a second follow-up after 46.6 ± 9.0 months. Thickened RPE on OCT, hyperpigmentation on CFP, hyper-reflective foci (HRF) on OCT, attributed to single or clustered intraretinal RPE, were identified. Fluorescence lifetimes in two spectral channels (short-wavelength spectral channel [SSC] = 500–560 nm, long-wavelength spectral channel [LSC] = 560–720 nm) as well as emission spectrum intensity ratio (ESIR) of the lesions were measured by FLIO.

Results

As hyperpigmented areas form and RPE migrates into the retina, FAF lifetimes lengthen and ESRI of RPE cells increase. Thickened RPE showed lifetimes of 256 ± 49 ps (SSC) and 336 ± 35 ps (LSC) and an ESIR of 0.552 ± 0.079. For hyperpigmentation, these values were 317 ± 68 ps (p < 0.001), 377 ± 56 ps (P < 0.001), and 0.609 ± 0.081 (P = 0.001), respectively, and for HRF 337 ± 79 ps (P < 0.001), 414 ± 50 ps (P < 0.001), and 0.654 ± 0.075 (P < 0.001).

Conclusions

In the process of RPE degeneration, comprising different steps of dysmorphia, hyperpigmentation, and migration, lengthening of FAF lifetimes and a hypsochromic shift of emission spectra can be observed by FLIO. Thus, FLIO might provide early biomarkers for AMD progression and contribute to our understanding of RPE pathology.

Inverted V-shaped extracapsular stabilisation technique and arthroscopic findings in six dogs with medial shoulder instability

OBJECTIVES

The aim of this case series was to report arthroscopic findings and to evaluate clinical outcomes of dogs treated with an inverted V-shaped extracapsular stabilisation technique without additional external coaptation for medial shoulder instability.

MATERIAL AND METHODS

Medical records of dogs with medial shoulder instability that underwent arthroscopy and an inverted V-shaped extracapsular stabilisation technique were retrospectively reviewed. Extracapsular stabilisation was performed in all dogs using screws and spiked washers as anchor points for the coated polyester prosthetic ligament. No additional external coaptation was used in any dog. A minimum 18-month follow-up period was required for study inclusion. Complications and long-term outcomes were recorded.

RESULTS

The subscapularis tendon and medial glenohumeral ligament were the structures most commonly affected. All dogs had pathological cartilage fibrillations. Implants were successfully placed in all dogs. Implant loosening was recorded in two out of six dogs on recheck but no revision surgery was performed. Function at the time of last clinical follow-up (median, 28 months, range 18 to 33 months) was full in four out of six and acceptable in two out of six dogs.

CLINICAL SIGNIFICANCE

Surgical treatment of medial shoulder instability using the novel inverted V-shaped extracapsular stabilisation technique was successful. Potential complications such as implant loosening may occur. Despite the limited number of cases, the present study suggests that additional postoperative external coaptation may not be necessary for successful management of dogs with medial shoulder instability.

Fluorescence Lifetimes and Spectra of RPE and Sub-RPE Deposits in Histology of Control and AMD Eyes

Purpose

To investigate fluorescence lifetimes as well as spectral characteristics of drusen and RPE autofluorescence in AMD.

Methods

Fluorescence lifetimes and spectra of five eyes with AMD and nine control eyes were analyzed in cryosections by means of two-photon excited fluorescence at 960 nm. Spectra were detected at 490 to 647 nm. Lifetimes were measured using time-correlated single photon counting in two spectral channels: 500 to 550 nm and 550 to 700 nm. Fluorescence decays over time were approximated by a series of three exponential functions. The amplitude-weighted mean fluorescence lifetime was determined.

Results

We identified 196 sub-RPE deposits (AMD, n = 76; control, n = 120) and recorded 241 RPE sites. The peak emission wavelength of sub-RPE deposits was significantly green shifted compared with RPE (peak at 570 nm vs. 610 nm), but did not differ between AMD and control donors. Sub-RPE deposits showed considerably longer mean fluorescence lifetimes than RPE (ch1, 581 ± 163 ps vs. 177 ± 25 ps; ch2, 541 ± 125 ps vs. 285 ± 31 ps; P < 0.001). Sub-RPE deposits found in AMD eyes had longer lifetimes than deposits of controls (ch1, 650 ± 167 ps vs. 537 ± 145 ps; ch2, 600 ± 125 ps vs. 504 ± 111 ps; P < 0.001). In AMD eyes, sub-RPE deposits showed a more homogenous autofluorescence distribution and more deposits were larger than 63 µm than in control eyes.

Conclusions

Ex vivo fluorescence imaging of sub-RPE deposits in cross-sections enables the separation of their autofluorescence from that of over- or underlying structures. Our analysis showed considerable variability of sub-RPE deposit lifetimes but not spectra. This indicates that sub-RPE deposits either consist of a variety of different fluorophores or expose the same fluorophores to different microenvironments.

Enterokolitis als Ursache eines akuten unerwarteten Todes eines Orang-Utans in Zoohaltung

Es wird von einem 13 Jahre alt gewordenen weiblichen Orang-Utan berichtet, der 4 Tage vor dem Tod an einer akuten Enterokolitis erkrankte. Die tierärztliche Ultraschalluntersuchung einen Tag vor dem Tod erbrachte den Nachweis von vermehrter Flüssigkeit im Zäkum und einer abschnittsweise verdickten Kolonwand. Nach dem für die Veterinärmediziner und die Zoomitarbeiter unerwarteten Todeseintritt erfolgte eine Obduktion durch Rechtsmediziner der Universitätsmedizin Rostock mit Unterstützung von Ärzten weiterer Fachrichtungen. Dabei wurde als Todesursache eine akute Escherichia-coli-Enterokolitis mit massiver Blutung in den Darm festgestellt. Begünstigend oder ursächlich für die letale Enterokolitis dürften wahrscheinlich zahlreiche rezidivierende Durchfallerkrankungen in der Anamnese des Orang-Utans als Folge eines Verweigerns des Stillens durch die Mutter nach der Geburt gewesen sein.

Enrichment and characterization of extracellular vesicles from ex vivo one-sided human placenta perfusion

PROBLEM

Extracellular vesicles (EVs) released by the placenta are packed with biological information and play a major role in fetomaternal communication. Here, we describe a comprehensive set-up for the enrichment and characterization of EVs from human placenta perfusion and their application in further assays.

METHOD OF STUDY

Human term placentas were used for 3 h ex vivo one-sided perfusions to simulate the intervillous circulation. Thereafter, populations of small (sEVs) and large EV (lEVs) were enriched from placental perfusate via serial ultracentrifugation. Following, EV populations were characterized regarding their size, protein concentration, RNA levels, expression of surface markers as well as their uptake and miRNA transfer to recipient cells.

RESULTS

The sEV and lEV fractions from an entire perfusate yielded, respectively, 294 ± 32 µg and 525 ± 96 µg of protein equivalents and 2.6 ± 0.5 µg and 3.6 ± 0.9 µg of RNA. The sEV fraction had a mean diameter of 117 ± 47 nm, and the lEV fraction presented 236 ± 54 nm. CD63 was strongly detected by dot blot in sEVs, whereas only traces of this marker were found in lEVs. Both EV fractions were positive for the trophoblast marker PLAP (placental alkaline phosphatase) and annexin A1. EV internalization in immune cells was visualized by confocal microscopy, and the transfer of placental miRNAs was detected by quantitative real-time PCR (qPCR).

CONCLUSIONS

Enriched EV populations showed characteristic features of sEVs and lEVs. EV uptake and transfer of miRNAs to recipient cells demonstrated their functional integrity. Therefore, we advocate the ex vivo one-sided placenta perfusion as a robust approach for the collection of placental EVs.

Comparison of algorithms to suppress artifacts from the natural lens in fluorescence lifetime imaging ophthalmoscopy (FLIO)

Fluorescence lifetime imaging ophthalmoscopy (FLIO) has developed as a new diagnostic tool in ophthalmology. FLIO measurements are taken from 30° retinal fields in two spectral channels (short spectral channel (SSC): 498-560 nm, long spectral channel (LSC): 560-720 nm). Because of the layered structure of the eye, the detected signal is an interaction of the fluorescence decay of the anterior part and of the fundus. By comparing FLIO measurements before and after cataract surgery, the impact of the natural lens was proven, despite the application of a confocal laser scanning (cSLO) technique. The goal of this work was to determine the best algorithmic solution to isolate the sole fundus fluorescence lifetime from the measured signal, suppressing artifacts from the natural lens. Three principles based on a tri-exponential model were investigated: a tailfit, a layer-based approach with a temporally shifted component, and the inclusion of a separately measured fluorescence decay of the natural lens. The mean fluorescence lifetime τ_m,12 is calculated using only the shortest and the intermediate exponential component. τ_m,all is calculated using all three exponential components. The results of tri-exponential tailfit after cataract surgery were considered as a reference, because the implanted artificial lens can be assumed as non-fluorescent. In SSC, the best accordance of τ_m,all of the reference was determined with τ_m,12 of the tailfit before surgery. If high-quality natural lens measurements are available, the correspondence of τ_m,12 is best with τ_m,all of the reference. In LSC, there is a good accordance for all models between τ_m,12 before and after surgery. To study the pure fundus fluorescence decay in eyes with natural lenses, we advise to utilize fluorescence lifetime τ_m,12 of a triple-exponential tailfit, as it corresponds well with the mean fluorescence lifetime τ_m,all of eyes with fluorescence-less artificial intraocular lenses.

Glycemic variability in patients with gastrointestinal cancer: An integrative review

PURPOSE

Glycemic variability is associated with risks for adverse events in patients with cancer. Several studies have evaluated the presence and impact of hyperglycemia and/or hypoglycemia in patients with cancer; however, few studies have evaluated glycemic variability. The purpose of this integrative review of studies in patients with gastrointestinal cancers was to investigate the presence and methods of reporting glycemic variability during and following treatments.

METHODS

A comprehensive review of the literature was conducted. PubMed, CINAHL, EMBASE, and Cochrane databases were searched for publications between 1/1/1969 and 7/24/2019. Studies of patients with gastrointestinal cancer following surgery, during treatment, and <5 years following treatment were included and evaluated by cancer type and method of glucose and glycemic variability measurement.

RESULTS

Among 1526 patients with gastrointestinal cancer across 19 studies, gastric and pancreatic cancers were most prevalent. Timing of glucose testing and methods of analyzing glycemic variability varied. Most analyses used the standard deviation or interquartile range. Glycemic variability was more prevalent among patients with Type 2 Diabetes and among those with pancreatic cancer. In some patients glycemic variability remained notable > one year following surgery despite improvements in glycemic control.

CONCLUSION

Patients with gastrointestinal cancer experience glycemic variability during and up to one year following treatment. There was heterogeneity in methods related to timing of testing and reporting glycemic variability among the 19 studies in this review. Future investigations need to identify the presence and define the methods of measuring glycemic variability in patients with gastrointestinal cancer.

A comparison of postoperative respiratory complications associated with the use of desflurane and sevoflurane: a single-centre cohort study

Sevoflurane and desflurane are the most commonly used volatile anaesthetics for maintenance of anaesthesia. In this study, we aimed to evaluate the relationship between choice of volatile anaesthetic and early postoperative respiratory complications, and to address a critical knowledge gap in safety outcomes between these two commonly used agents. We performed a retrospective analysis of adult (non-cardiac surgery) patients who received sevoflurane or desflurane for the maintenance of general anaesthesia at our institution between 2005 and 2018. We evaluated the association between desflurane exposure (when compared with sevoflurane) and the primary outcome of postoperative respiratory complications, defined by early post-extubation desaturation (S_p O₂  < 90%) or re-intubation within 7 days postoperatively. Multivariable regression analyses were performed and adjusted for confounding factors, including patient, anaesthetic and surgical factors. Propensity matched, interaction and sub-group analyses were performed to assess outcomes in high-risk groups: morbidly obese (BMI > 35 kg.m^-2 ); elderly (age > 65 years); and high risk of respiratory complications as well as the primary outcome at 24 h. Desflurane was used for 23,830 patients and sevoflurane for 84,608 patients. Patients exposed to desflurane did not demonstrate a reduced risk of postoperative respiratory complications when compared with sevoflurane (adjusted odds ratio 0.99, 95%CI 0.94-1.04, p = 0.598). These findings were consistent across all sub-groups of high-risk patients and in the propensity score matched cohort. In summary, desflurane use was not associated with reduced postoperative respiratory complications when compared with sevoflurane. In the context of environmental and cost concerns with volatile anaesthetic agents, our study provides important data to support organisational decisions regarding the use of desflurane.

Influence of Lens Fluorescence on Fluorescence Lifetime Imaging Ophthalmoscopy (FLIO) Fundus Imaging and Strategies for Its Compensation

Purpose

To explore the contribution of crystalline lens fluorescence to fluorescence lifetimes measured with fluorescence lifetime imaging ophthalmoscopy (FLIO) and to propose a computational model to reduce the lens influence.

Methods

FLIO, which detects autofluorescence decay over time in a short-wavelength spectral channel (SSC, 498–560 nm) and a long-wavelength spectral channel (LSC, 560–720 nm), was performed on 32 patients before and after cataract extraction. The mean autofluorescence lifetime (τ_m) of the fundus was determined from a three-exponential fit of the postoperative fluorescence decays. The preoperative measurements were fit with series of exponential functions in which one fluorescence component was time-shifted in order to represent lens fluorescence.

Results

Postoperatively, τ_m was 185 ± 22 ps in the SSC and 209 ± 34 ps in the LSC at the posterior pole. These values were best reproduced by fitting the postoperative measurements with a three-exponential model with a time-shifted third fluorescence component (SSC, 203 ± 45 ps; LSC, 215 ± 29 ps), whereas disregarding time-shifted lens fluorescence resulted in significantly (P < 0.001) longer τ_m values (SSC, 474 ± 206 ps; LSC, 215 ± 29 ps). The fluorescence of the cataract lens contributed to the total fluorescence by 54.2 ± 10.6% (SSC) and 29.5 ± 9.9% (LSC).

Conclusions

Cataract lens fluorescence greatly alters fluorescence lifetimes measured at the fundus by FLIO, resulting in an overestimation of the lifetimes; however, this may be compensated for considerably by taking lens influence into account in the fitting model.

Translational Relevance

This study investigates cataract fluorescence in FLIO and a mathematical model for compensation of this influence.

THU0478 IS NEUROPATHIC PAIN IN INFLAMMATORY RHEUMATIC DISORDERS AN UNDERESTIMATED PROBLEM? RESULTS FROM THE GERMAN PAINDETECT DATABASE

Background:

The aim of the study was to investigate the impact and relevance of neuropathic pain in inflammatory rheumatic disorders (IRD) and osteoarthritis (OA).

Objectives:

Pain is one of the main symptoms in patients with IRD and OA. To enhance a mechanistic based treatment of pain the differentiation between nociceptive and neuropathic pain via screening tools (e.g. painDETECT questionaire) might possibly be helpful. The goal of the study was to investigate (1) if neuropathic pain is a significant burden for patients with IRD and (2) if pain patterns differs from degenerative joint diseases such as OA in over 9.000 patients in each group.

Methods:

painDETECT is a questionnaire that has been evaluated and used in numerous clinical trials to detect neuropathic pain in various diseases. The collected data is centrally managed and evaluated. In total (end of 2019) 395.984 patients have been documented. Out of the painDETECT database 9256 patients with IRD and 9436 patients with OA were extracted, analyzed and compared on their neuropathic pain pattern (screening was performed using the painDETECT-questionaire., PDQ). Secondary parameters were: intensity of pain, functional status, depression, chronicity and sleep disorder. Patients had been recruited from general practitioners (GPs), Rheumatologists, Orthopedics and Neurologists from 862 office-based physicians into the painDETECT-database. This project is an open label registry study in Germany.

Results:

The median PDQ-score of patients with inflammatory rheumatic disorders adds up to 14,2 (1-38) and of OA patients to 13,8. 28.7% of inflammatory rheumatic disorders and 27.2% of OA-patients showed signs for neuropathic pain by positive PDQ. The difference was according to this high patient numbers statistically significant (P=0.0015). VAS-Score, Depressions-Score, Chronicity -Score and Functional -Score showed no clinically relevant differences between these two groups.

Conclusion:

Nearly one third of patients with IRD as well as patients with OA showed neuropathic pain components by using PDQ. Despite increasingly better disease control through more effective therapies, pain still remains a major burden for many patients and has a profound impact on their quality of life. The present data indicate a surprisingly high symptoms of neuropathic pain even in IRD patients and should be considered in the management of our patients. A new documentation system for Rheumatologists (RheumaAssist) could help to address these questions.

Percentage of PDQ-categories (negative/unclear/positive) for patients with inflammatory rheumatic disorders (IRD) or Arthrosis (OA)

Acknowledgments:

This investigation was supported within a grant of Pfizer Deutschland GmbH.

Disclosure of Interests: :

Philipp Sewerin Grant/research support from: AbbVie Deutschland GmbH & Co. KG

Bristol-Myers Squibb Celgene GmbH

Lilly Deutschland GmbH

Novartis Pharma GmbH Pfizer Deutschland GmbH

Rheumazentrum Rhein-Ruhr, Consultant of: AMGEN GmbH AbbVie Deutschland GmbH & Co. KG Biogen GmbHBristol-Myers Squibb Celgene GmbH Chugai Pharma arketing Ltd. / Chugai Europe GmbHHexal Pharma Janssen-CilagGmbH Johnson & Johnson Deutschland GmbHLilly Deutschland GmbH / Lilly Europe / Lilly Global Novartis Pharma GmbH Pfizer Deutschland GmbH Roche Pharma Rheumazentrum Rhein-Ruhr Sanofi-Genzyme Deutschland GmbH Swedish Orphan Biovitrum GmbH UCB Pharma GmbH, Speakers bureau: AMGEN GmbH AbbVie Deutschland GmbH & Co. KG Biogen GmbHBristol-Myers Squibb Celgene GmbH Chugai Pharma arketing Ltd. / Chugai Europe GmbHHexal Pharma Janssen-CilagGmbH Johnson & Johnson Deutschland GmbHLilly Deutschland GmbH / Lilly Europe / Lilly Global Novartis Pharma GmbH Pfizer Deutschland GmbH Roche Pharma Rheumazentrum Rhein-Ruhr Sanofi-Genzyme Deutschland GmbH Swedish Orphan Biovitrum GmbH UCB Pharma GmbH, Rainer Freynhagen Consultant of: AOP Orphan Pharma, Grünenthal, Lilly, Merck, Mitsubishi Tanabe Pharma, Pfizer, Scilex Pharmaceutics

, Speakers bureau: AOP Orphan Pharma, Grünenthal, Lilly, Merck, Mitsubishi Tanabe Pharma, Pfizer, Scilex Pharmaceutics

, Thomas Tölle Consultant of: AOP Orphan, Almiral Hermal, Bionest Partners, Benkitt Renkiser, Grünenthal, Hexal, Indivior, Kaia Health, Lilly, Medscape Mundipharma, MSD, Novartis, Pfizer, Recordati Pharma, Sanofi-Aventis, and TAD Pharma, Speakers bureau: AOP Orphan, Almiral Hermal, Bionest Partners, Benkitt Renkiser, Grünenthal, Hexal, Indivior, Kaia Health, Lilly, Medscape Mundipharma, MSD, Novartis, Pfizer, Recordati Pharma, Sanofi-Aventis, and TAD Pharma, Michael Hammer Consultant of: Abbvie, Pfizer, Medac and Janssen, Speakers bureau: Abbvie, Pfizer, Medac and Janssen, Christoph Baerwald Consultant of: CGB received speaker or consulting fees from AbbVie, Paid instructor for: CGB received speaker or consulting fees from AbbVie, Speakers bureau: CGB received speaker or consulting fees from AbbVie, Jochen Walter Consultant of: Pfizer, Speakers bureau: AbbVie, Frauenhofer Institut, Gilead, Janssen-Cilag, Medac, Novartis, Pfizer, Ralf Schröder Shareholder of: Pfizer Pharma GmbH, Employee of: Pfizer Pharma GmbH, Matthias Schneider Grant/research support from: GSK, UCB, Abbvie, Consultant of: Abbvie, Alexion, Astra Zeneca, BMS, Boehringer Ingelheim, Gilead, Lilly, Sanofi, UCB, Speakers bureau: Abbvie, Astra Zeneca, BMS, Chugai, GSK, Lilly, Pfizer, Sanofi, Ralf Baron Consultant of: RB received speaker or consulting fees from AbbVie, Paid instructor for: RB received speaker or consulting fees from AbbVie, Speakers bureau: RB received speaker or consulting fees from AbbVie

Fundus Autofluorescence Lifetimes and Spectral Features of Soft Drusen and Hyperpigmentation in Age-Related Macular Degeneration

Purpose

To investigate the autofluorescence lifetimes as well as spectral characteristics of soft drusen and retinal hyperpigmentation in age-related macular degeneration (AMD).

Methods

Forty-three eyes with nonexudative AMD were included in this study. Fluorescence lifetime imaging ophthalmoscopy (FLIO), which detects autofluorescence decay over time in the short (SSC) and long (LSC) wavelength channel, was performed. The mean autofluorescence lifetime (τ_m) and the spectral ratio (sr) of autofluorescence emission in the SSC and LSC were recorded and analyzed. In total, 2760 soft drusen and 265 hyperpigmented areas were identified from color fundus photographs and spectral domain optical coherence tomography (SD-OCT) images and superimposed onto their respective AF images. τ_m and sr of these lesions were compared with fundus areas without drusen. For clearly hyperfluorescent drusen, the local differences compared to fundus areas without drusen were determined for lifetimes and sr.

Results

Hyperpigmentation showed significantly longer τ_m (SSC: 341 ± 81 vs. 289 ± 70 ps, P < 0.001; LSC: 406 ± 42 vs. 343 ± 42 ps, P < 0.001) and higher sr (0.621 ± 0.077 vs. 0.539 ± 0.083, P < 0.001) compared to fundus areas without hyperpigmentation or drusen. No significant difference in τ_m was found between soft drusen and fundus areas without drusen. However, the sr was significantly higher in soft drusen (0.555 ± 0.077 vs. 0.539 ± 0.081, P < 0.0005). Hyperfluorescent drusen showed longer τ_m than surrounding fundus areas without drusen (SSC: 18 ± 42 ps, P = 0.074; LSC: 16 ± 29 ps, P = 0.020).

Conclusions

FLIO can quantitatively characterize the autofluorescence of the fundus, drusen, and hyperpigmentation in AMD.

Translational Relevance

The experimental FLIO technique was applied in a clinical investigation. As FLIO yields information on molecular changes in AMD, it might support future diagnostics.

Simplified approach to least-square fitting of fluorescence lifetime ophthalmoscopy (FLIO) data by fixating lifetimes

Fluorescence lifetime imaging ophthalmoscopy (FLIO) is a new imaging modality in ophthalmology. For clinical investigations, the amplitude-weighted mean of two or three lifetime components is usually analyzed. In this study, we investigated the effects of fixation of lifetime components. This resulted in slightly higher fit errors but mean lifetimes were highly correlated to those from fits with variable individual lifetimes. Furthermore, this approach resulted in a similarly good discrimination of diabetic retinopathy patients from controls, a reduction of the computational workload, a de-noising of the mean lifetime images and allows higher local resolution. Thus, fixation of lifetimes in the fit of FLIO data could be superior for clinical routine analysis of FLIO data.

Bleaching effects and fluorescence lifetime imaging ophthalmoscopy

This study investigates the influence of photopigment bleaching on autofluorescence lifetimes in the fundus in 21 young healthy volunteers. Three measurements of 30° retinal fields in two spectral channels (SSC: 498-560 nm, LSC: 560-720 nm) were obtained for each volunteer using fluorescence lifetime imaging ophthalmoscopy (FLIO). After dark-adaptation by wearing a custom-made lightproof mask for 30 minutes, the first FLIO-measurement was recorded (dark-adapted state). Subsequently, the eye was bleached for 1 minute (luminance: 3200 cd/m²), followed by a second FLIO-measurement (bleached state). Following an additional 10 minute dark adaptation using the mask, a final FLIO-measurement was recorded (recovered state). Average values of the fluorescence lifetimes were calculated from within different areas of a standardized early treatment diabetic retinopathy study (ETDRS) grid (central area, inner and outer rings). The acquisition time in the bleached state was significantly shortened by approximately 20%. The SSC did not show any significant changes in fluorescence lifetimes with photopigment bleaching, only the LSC showed small but significant bleaching-related changes in the fluorescence lifetimes τ₁ and τ₂ from all regions, as well as the mean fluorescence lifetime in the central area. The fluorescence lifetime differences caused by bleaching were by far less significant than pathological changes caused by eye diseases. The magnitudes of fluorescence lifetime changes are <10% and do not interfere with healthy or disease related FLIO patterns. Thus, we conclude that bleaching is not a relevant confounder in current clinical applications of FLIO.

Review of clinical approaches in fluorescence lifetime imaging ophthalmoscopy (Erratum)

This erratum corrects an error in "Review of clinical approaches in fluorescence lifetime imaging ophthalmoscopy".

Review of clinical approaches in fluorescence lifetime imaging ophthalmoscopy

Autofluorescence-based imaging techniques have become very important in the ophthalmological field. Being noninvasive and very sensitive, they are broadly used in clinical routines. Conventional autofluorescence intensity imaging is largely influenced by the strong fluorescence of lipofuscin, a fluorophore that can be found at the level of the retinal pigment epithelium. However, different endogenous retinal fluorophores can be altered in various diseases. Fluorescence lifetime imaging ophthalmoscopy (FLIO) is an imaging modality to investigate the autofluorescence of the human fundus in vivo. It expands the level of information, as an addition to investigating the fluorescence intensity, and autofluorescence lifetimes are captured. The Heidelberg Engineering Spectralis-based fluorescence lifetime imaging ophthalmoscope is used to investigate a 30-deg retinal field centered at the fovea. It detects FAF decays in short [498 to 560 nm, short spectral channel (SSC) and long (560 to 720 nm, long spectral channel (LSC)] spectral channels, the mean fluorescence lifetimes (τm) are calculated using bi- or triexponential approaches. These are meant to be relatively independent of the fluorophore's intensity; therefore, fluorophores with less intense fluorescence can be detected. As an example, FLIO detects the fluorescence of macular pigment, retinal carotenoids that help protect the human fundus from light damages. Furthermore, FLIO is able to detect changes related to various retinal diseases, such as age-related macular degeneration, albinism, Alzheimer's disease, diabetic retinopathy, macular telangiectasia type 2, retinitis pigmentosa, and Stargardt disease. Some of these changes can already be found in healthy eyes and may indicate a risk to developing such diseases. Other changes in already affected eyes seem to indicate disease progression. This review article focuses on providing detailed information on the clinical findings of FLIO. This technique detects not only structural changes at very early stages but also metabolic and disease-related alterations. Therefore, it is a very promising tool that might soon be used for early diagnostics.

Fundus autofluorescence beyond lipofuscin: lesson learned from ex vivo fluorescence lifetime imaging in porcine eyes

Fundus autofluorescence (FAF) imaging is a well-established method in ophthalmology; however, the fluorophores involved need more clarification. The FAF lifetimes of 20 post mortem porcine eyes were measured in two spectral channels using fluorescence lifetime imaging ophthalmoscopy (FLIO) and compared with clinical data from 44 healthy young subjects. The FAF intensity ratio of the short and the long wavelength emission (spectral ratio) was determined. Ex vivo porcine fundus fluorescence emission is generally less intense than that seen in human eyes. The porcine retina showed significantly (p<0.05) longer lifetimes than the retinal pigment epithelium (RPE): 584 ± 128 ps vs. 121 ± 55 ps 498-560 nm, 240 ± 42 ps vs. 125 ± 20 ps at 560-720 nm. Furthermore, the lifetimes of the porcine RPE were significantly shorter (121 ± 55 ps and 125 ± 20 ps) than those measured from human fundus in vivo (162 ± 14 ps and 179 ± 13 ps, respectively). The fluorescence emission of porcine retina was shifted towards a shorter wavelength compared to that of RPE and human FAF. This data shows the considerable contribution of fluorophores in the neural retina to total FAF intensity in porcine eyes.

Characterization of Retinitis Pigmentosa Using Fluorescence Lifetime Imaging Ophthalmoscopy (FLIO)

PURPOSE

We investigated fundus autofluorescence (FAF) lifetimes in patients with retinitis pigmentosa (RP) using fluorescence lifetime imaging ophthalmoscopy (FLIO).

METHODS

A total of 33 patients (mean age, 40.0 ± 17.0 years) with RP and an age-matched healthy group were included. The Heidelberg FLIO was used to detect FAF decays in short (SSC; 498-560 nm) and long (LSC; 560-720 nm) spectral channels. We investigated a 30° retinal field and calculated the amplitude-weighted mean fluorescence lifetime (τm). Additionally, macular pigment measurements, macular optical coherence tomography (OCT) scans, fundus photographs, visual fields, and fluorescein angiograms were recorded. Genetic studies were performed on nearly all patients.

RESULTS

In RP, FLIO shows a typical pattern of prolonged τm in atrophic regions in the outer macula (SSC, 419 ± 195 ps; LSC, 401 ± 111 ps). Within the relatively preserved retina in the macular region, ring-shaped patterns were found, most distinctive in patients with autosomal dominant RP inheritance. Mean FAF lifetimes were shortened in rings in the LSC. Central areas remained relatively unaffected.

CONCLUSIONS

FLIO uniquely presents a distinct and specific signature in eyes affected with RP. The ring patterns show variations that indicate genetically determined pathologic processes. Shortening of FAF lifetimes in the LSC may indicate disease progression, as was previously demonstrated for Stargardt disease. Therefore, FLIO might be able to indicate disease progression in RP as well.

TRANSLATIONAL RELEVANCE

Hyperfluorescent FLIO rings with short FAF lifetimes may provide insight into the pathophysiologic disease status of RP-affected retinas potentially providing a more detailed assessment of disease progression.

Fluorescence Lifetime Imaging Ophthalmoscopy (FLIO) of Macular Pigment

Purpose

To describe different patterns of macular pigment (MP) seen in fluorescence lifetime imaging ophthalmoscopy (FLIO) and to analyze ex vivo fluorescence characteristics of carotenoids.

Methods

A total of 31 eyes of young healthy subjects, 4 eyes from patients with albinism, 36 eyes with macular telangiectasia type 2 (MacTel), 24 eyes with retinitis pigmentosa, and 1 eye with a macular hole were included in this clinic-based, cross-sectional study. All subjects underwent Heidelberg Engineering FLIO and MP measurements (dual-wavelength autofluorescence). Fundus autofluorescence (FAF) lifetimes of a 30° retinal field were detected in two spectral channels (SSC: 498-560 nm; LSC: 560-720 nm), and amplitude-weighted mean fluorescence lifetimes (τm) were calculated. Additionally, autofluorescence lifetimes of known dilutions of lutein and zeaxanthin were measured in a cuvette in free- and protein-associated states.

Results

MP shows a significant inverse correlation to foveal FAF lifetimes measured with FLIO (SSC: r = -0.608; P < 0.001). Different distribution patterns can be assigned to specific disease-related changes. Two patients with albinism, who did not have MP, were found to be missing short FAF lifetimes. In solvent, lutein and zeaxanthin show very short autofluorescence lifetimes (∼50-60 ps; SSC), as do their respective binding proteins (∼40-50 ps; SSC). When combining carotenoids with their specific binding proteins, the decay times shift to longer means (∼70-90 ps; SSC).

Conclusions

This study expands upon previous findings of an impact of MP on short FAF lifetimes by describing ex vivo autofluorescence lifetimes of carotenoids and different in vivo autofluorescence patterns that can be associated with certain diseases.

Monitoring foveal sparing in geographic atrophy with fluorescence lifetime imaging ophthalmoscopy - a novel approach

PURPOSE

To investigate fundus autofluorescence (FAF) lifetimes in geographic atrophy (GA) with a focus on macular pigment (MP) and foveal sparing.

METHODS

The study included 35 eyes from 28 patients (mean age 79.2 ± 8.0 years) with GA. A 30° retinal field, centred at the macula, was investigated using fluorescence lifetime imaging ophthalmoscopy (FLIO). The FLIO technology is based on a Heidelberg Engineering Spectralis system. Decays of FAF were detected in a short (498-560 nm, SSC) and long (560-720 nm, LSC) spectral channel. The mean fluorescence lifetime, τ_m , was calculated from a three-exponential approximation of the FAF decays. Macular optical coherence tomography (OCT) scans as well as fundus photography were recorded.

RESULTS

Review of FLIO data reveals specific patterns of significantly prolonged τ_m in regions of GA (SSC 616 ± 343 ps, LSC 615 ± 154 ps) as compared to non-atrophic regions. Large τ_m differences between the fovea and atrophic areas correlate with better visual acuity (VA). Shorter τ_m at the fovea than within other non-atrophic regions indicates sparing, which was identified in 16 eyes. Seventy per cent of patients treated with lutein supplementation showed foveal sparing, whereas the rate among non-supplemented patients was 22%.

CONCLUSION

Using FLIO, we present a novel way to detect foveal sparing, investigate MP, and analyse variability of τ_m in different foveal regions (including the prognostic valuable border region) in GA. These findings support the potential utility of FLIO in monitoring disease progression. The findings also highlight the possibly protective effect of lutein supplementation, with implication in recording the presence and distributional pattern of MP.

Monitoring foveal sparing in geographic atrophy with fluorescence lifetime imaging ophthalmoscopy - a novel approach

PURPOSE

To investigate fundus autofluorescence (FAF) lifetimes in geographic atrophy (GA) with a focus on macular pigment (MP) and foveal sparing.

METHODS

The study included 35 eyes from 28 patients (mean age 79.2 ± 8.0 years) with GA. A 30° retinal field, centred at the macula, was investigated using fluorescence lifetime imaging ophthalmoscopy (FLIO). The FLIO technology is based on a Heidelberg Engineering Spectralis system. Decays of FAF were detected in a short (498-560 nm, SSC) and long (560-720 nm, LSC) spectral channel. The mean fluorescence lifetime, τ_m , was calculated from a three-exponential approximation of the FAF decays. Macular optical coherence tomography (OCT) scans as well as fundus photography were recorded.

RESULTS

Review of FLIO data reveals specific patterns of significantly prolonged τ_m in regions of GA (SSC 616 ± 343 ps, LSC 615 ± 154 ps) as compared to non-atrophic regions. Large τ_m differences between the fovea and atrophic areas correlate with better visual acuity (VA). Shorter τ_m at the fovea than within other non-atrophic regions indicates sparing, which was identified in 16 eyes. Seventy per cent of patients treated with lutein supplementation showed foveal sparing, whereas the rate among non-supplemented patients was 22%.

CONCLUSION

Using FLIO, we present a novel way to detect foveal sparing, investigate MP, and analyse variability of τ_m in different foveal regions (including the prognostic valuable border region) in GA. These findings support the potential utility of FLIO in monitoring disease progression. The findings also highlight the possibly protective effect of lutein supplementation, with implication in recording the presence and distributional pattern of MP.

Patterns of Fundus Autofluorescence Lifetimes In Eyes of Individuals With Nonexudative Age-Related Macular Degeneration

Purpose

To investigate fundus autofluorescence (FAF) lifetimes in patients with nonexudative AMD.

Methods

A total of 150 eyes of 110 patients (mean age: 73.2 ± 10.7 years) with nonexudative AMD, as well as a healthy group of 57 eyes in 38 subjects (mean age: 66.5 ± 8.7 years), were included. Investigations were conducted at the University Eye Clinic in Jena, Germany, as well as the Moran Eye Center in Salt Lake City, Utah, USA, using the Heidelberg Engineering Spectralis-based fluorescence lifetime imaging ophthalmoscope (FLIO). A 30° retinal field centered at the fovea was investigated. FAF decays were detected in short (498-560 nm) and long (560-720 nm, LSC) spectral channels. The mean fluorescence lifetimes (τm) were calculated. Optical coherence tomography scans and fundus photographs were also recorded.

Results

In patients with nonexudative AMD, FLIO shows a ring-shaped pattern of prolonged τm in the LSC. This pattern occurs in all patients with AMD (including very early stages) and in one-third of the healthy controls. FAF lifetimes were longer with more advanced stages. The presence of drusen is associated with prolonged τm when compared with the healthy fundus, but drusen identification is difficult with FLIO only.

Conclusions

FLIO detects a clear pattern of changes within the fundus, which appears to be AMD-associated. These changes are already visible in early AMD stages and not masked by the presence of other coexisting retinal diseases. These findings may be useful for the early diagnosis of AMD and to distinguish AMD from other retinal diseases.

Fluorescence Lifetime Imaging Ophthalmoscopy: A Novel Way to Assess Macular Telangiectasia Type 2

Purpose

Macular Telangiectasia Type 2 (MacTel) is an uncommon, late-onset complex retinal disease that leads to central vision loss. No causative gene(s) have been identified so far, resulting in a challenging clinical diagnostic dilemma because retinal changes of early stages are often subtle. The objective of this study was to investigate the benefit of fluorescence lifetime imaging ophthalmoscopy (FLIO) for retinal imaging in patients with MacTel.

Design

Cross-sectional study from a tertiary-care retinal referral practice.

Subjects and Controls

42 eyes of 21 patients (mean age 60.5±13.3 years) with MacTel as well as an age-matched healthy control group (42 eyes of 25 subjects, mean age 60.8±13.4 years).

Methods

A 30° retinal field centered at the fovea was investigated using FLIO. This camera is based on a Heidelberg Engineering Spectralis system. Fundus autofluorescence (FAF) decays were detected in short (498-560 nm, SSC) and long (560-720 nm, LSC) spectral channels. The mean fluorescence lifetime, τ_m, was calculated from a 3-exponential approximation of the FAF decays. For MacTel patients, macular pigment (MP), OCT, blue light reflectance, fluorescein angiography, as well as fundus photography, were also recorded.

Main Outcome Measures

Mean FAF lifetime (τ_m) images.

Results

FLIO of MacTel patients shows a unique pattern of prolonged τ_m at the temporal side of the fovea in patients with MacTel in the "MacTel area" within 5-6° of the foveal center. In early stages, this region appears crescent-shaped, while advanced stages show a ring-like pattern. This pattern corresponds well with other imaging modalities and gives an especially high contrast of the affected region even in minimally affected individuals. Additionally, FLIO provides a novel means to monitor the abnormal MP distribution. In one case, FLIO showed changes suggestive of MacTel within a clinically normal parent of two MacTel patients.

Conclusions

FLIO detects retinal changes in patients with MacTel with high contrast, presenting a distinctive signature that is a characteristic finding of the disease. The non-invasive properties of this novel imaging modality provide a valuable addition to clinical assessment of early changes in the disease that could lead to more accurate diagnosis of MacTel.

Hydrogen peroxide modulates energy metabolism and oxidative stress in cultures of permanent human Müller cells MIO-M1

In this study the influence of hydrogen peroxide (H₂ O₂ ) on the redox state, NADH protein binding, and mitochondrial membrane potential in Müller cells is investigated. Cultures of permanent human Müller cells MIO-M1 were exposed to H₂ O₂ in 75 µM and 150 µM concentration for two hours. Fluorescence emission spectra and lifetimes were measured by two-photon microscopy (excitation wavelength: 740 nm) at the mitochondria which were identified in the microscopic images by their fluorescence properties (spectra and intensity). Two hours of H₂ O₂ exposure did not impair viability of MIO-M1 cells in culture. Whereas the ratio of flavine- to NADH fluorescence intensity did not change under either H₂ O₂ concentration, the mean lifetime was significantly different between controls, not exposed to H₂ O₂ , and the 150 µM H₂ O₂ exposure (972 ± 63 ps vs. 1152 ± 64 ps, p = 0.014). One hour after cessation of the H₂ O₂ exposure, the value retuned to that of the control (983 ± 36 ps). A hyperpolarization of the mitochondrial membrane under 150 µM H₂ O₂ was found. These findings suggest a shift form free to protein-bound NADH in mitochondria as well as a hyperpolarization of their inner membrane which could be related to an impairment of Müller cell function despite their preserved viability. Exposure of human Müller cells to hydrogen peroxide for two hours results in a reversible change of protein binding of mitochondrial NADH upon unchanged redox ratio. The mitochondrial membrane potential is increased during exposure.

Fluorescence lifetime imaging ophthalmoscopy

Imaging techniques based on retinal autofluorescence have found broad applications in ophthalmology because they are extremely sensitive and noninvasive. Conventional fundus autofluorescence imaging measures fluorescence intensity of endogenous retinal fluorophores. It mainly derives its signal from lipofuscin at the level of the retinal pigment epithelium. Fundus autofluorescence, however, can not only be characterized by the spatial distribution of the fluorescence intensity or emission spectrum, but also by a characteristic fluorescence lifetime function. The fluorescence lifetime is the average amount of time a fluorophore remains in the excited state following excitation. Fluorescence lifetime imaging ophthalmoscopy (FLIO) is an emerging imaging modality for in vivo measurement of lifetimes of endogenous retinal fluorophores. Recent reports in this field have contributed to our understanding of the pathophysiology of various macular and retinal diseases. Within this review, the basic concept of fluorescence lifetime imaging is provided. It includes technical background information and correlation with in vitro measurements of individual retinal metabolites. In a second part, clinical applications of fluorescence lifetime imaging and fluorescence lifetime features of selected retinal diseases such as Stargardt disease, age-related macular degeneration, choroideremia, central serous chorioretinopathy, macular holes, diabetic retinopathy, and retinal artery occlusion are discussed. Potential areas of use for fluorescence lifetime imaging ophthalmoscopy will be outlined at the end of this review.

Monitoring macular pigment changes in macular holes using fluorescence lifetime imaging ophthalmoscopy

PURPOSE

To investigate the impact of macular pigment (MP) on fundus autofluorescence (FAF) lifetimes in vivo by characterizing full-thickness idiopathic macular holes (MH) and macular pseudo-holes (MPH).

METHODS

A total of 37 patients with MH and 52 with MPH were included. Using the fluorescence lifetime imaging ophthalmoscope (FLIO), based on a Heidelberg Engineering Spectralis system, a 30° retinal field was investigated. FAF decays were detected in a short (498-560 nm; ch1) and long (560-720 nm; ch2) wavelength channel. τ_m , the mean fluorescence lifetime, was calculated from a three-exponential approximation of the FAF decays. Macular coherence tomography scans were recorded, and macular pigment's optical density (MPOD) was measured (one-wavelength reflectometry). Two MH subgroups were analysed according to the presence or absence of an operculum above the MH. A total of 17 healthy fellow eyes were included. A longitudinal FAF decay examination was conducted in nine patients, which were followed up after surgery and showed a closed MH.

RESULTS

In MH without opercula, significant τ_m differences (p < 0.001) were found between the hole area (MHa) and surrounding areas (MHb) (ch1: MHa 238 ± 64 ps, MHb 181 ± 78 ps; ch2: MHa 275 ± 49 ps, MHb 223 ± 48 ps), as well as between MHa and healthy eyes or closed MH. Shorter τ_m , adjacent to the hole, can be assigned to areas with equivalently higher MPOD. Opercula containing MP also show short τ_m . In MPH, the intactness of the Hele fibre layer is associated with shortest τ_m .

CONCLUSIONS

Shortest τ_m originates from MP-containing retinal layers, especially from the Henle fibre layer. Fluorescence lifetime imaging ophthalmoscope (FLIO) provides information on the MP distribution, the pathogenesis and topology of MH. Macular pigment (MP) fluorescence may provide a biomarker for monitoring pathological changes in retinal diseases.

Monitoring macular pigment changes in macular holes using fluorescence lifetime imaging ophthalmoscopy

PURPOSE

To investigate the impact of macular pigment (MP) on fundus autofluorescence (FAF) lifetimes in vivo by characterizing full-thickness idiopathic macular holes (MH) and macular pseudo-holes (MPH).

METHODS

A total of 37 patients with MH and 52 with MPH were included. Using the fluorescence lifetime imaging ophthalmoscope (FLIO), based on a Heidelberg Engineering Spectralis system, a 30° retinal field was investigated. FAF decays were detected in a short (498-560 nm; ch1) and long (560-720 nm; ch2) wavelength channel. τ_m , the mean fluorescence lifetime, was calculated from a three-exponential approximation of the FAF decays. Macular coherence tomography scans were recorded, and macular pigment's optical density (MPOD) was measured (one-wavelength reflectometry). Two MH subgroups were analysed according to the presence or absence of an operculum above the MH. A total of 17 healthy fellow eyes were included. A longitudinal FAF decay examination was conducted in nine patients, which were followed up after surgery and showed a closed MH.

RESULTS

In MH without opercula, significant τ_m differences (p < 0.001) were found between the hole area (MHa) and surrounding areas (MHb) (ch1: MHa 238 ± 64 ps, MHb 181 ± 78 ps; ch2: MHa 275 ± 49 ps, MHb 223 ± 48 ps), as well as between MHa and healthy eyes or closed MH. Shorter τ_m , adjacent to the hole, can be assigned to areas with equivalently higher MPOD. Opercula containing MP also show short τ_m . In MPH, the intactness of the Hele fibre layer is associated with shortest τ_m .

CONCLUSIONS

Shortest τ_m originates from MP-containing retinal layers, especially from the Henle fibre layer. Fluorescence lifetime imaging ophthalmoscope (FLIO) provides information on the MP distribution, the pathogenesis and topology of MH. Macular pigment (MP) fluorescence may provide a biomarker for monitoring pathological changes in retinal diseases.