Microscope-integrated optical coherence tomography for in vivo human brain tumor detection with artificial intelligence.

OBJECTIVE: It has been shown that optical coherence tomography (OCT) can identify brain tumor tissue and potentially be used for intraoperative margin diagnostics. However, there is limited evidence on its use in human in vivo settings, particularly in terms of its applicability and accuracy of residual brain tumor detection (RTD). For this reason, a microscope-integrated OCT system was examined to determine in vivo feasibility of RTD after resection with automated scan analysis. METHODS: Healthy and diseased brain was 3D scanned at the resection edge in 18 brain tumor patients and investigated for its informative value in regard to intraoperative tissue classification. Biopsies were taken at these locations and labeled by a neuropathologist for further analysis as ground truth. Optical OCT properties were obtained, compared, and used for separation with machine learning. In addition, two artificial intelligence-assisted methods were utilized for scan classification, and all approaches were examined for RTD accuracy and compared to standard techniques. RESULTS: In vivo OCT tissue scanning was feasible and easily integrable into the surgical workflow. Measured backscattered light signal intensity, signal attenuation, and signal homogeneity were significantly distinctive in the comparison of scanned white matter to increasing levels of scanned tumor infiltration (p < 0.001) and achieved high values of accuracy (85%) for the detection of diseased brain in the tumor margin with support vector machine separation. A neuronal network approach achieved 82% accuracy and an autoencoder approach 85% accuracy in the detection of diseased brain in the tumor margin. Differentiating cortical gray matter from tumor tissue was not technically feasible in vivo. CONCLUSIONS: In vivo OCT scanning of the human brain has been shown to contain significant value for intraoperative RTD, supporting what has previously been discussed for ex vivo OCT brain tumor scanning, with the perspective of complementing current intraoperative methods for this purpose, especially when deciding to withdraw from further resection toward the end of the surgery.

Real-Time Temperature-Controlled Retinal Laser Irradiation in Rabbits.

Purpose: Subdamaging thermal retinal laser therapy has the potential to induce regenerative stimuli in retinal diseases, but validated dosimetry is missing. Real-time optoacoustic temperature determination and control could close this gap. This study investigates a first in vivo application. Methods: Two iterations of a control module that were optically coupled in between a continuous-wave commercial laser source and a commercial slit lamp were evaluated on chinchilla rabbits. The module allows extraction of the temperature rise in real time and can control the power of the therapy laser such that a predefined temperature rise at the retina is quickly achieved and held constant. Irradiations with aim temperatures from 45°C to 69°C were performed on a diameter of 200 µm and a heating time of 100 ms. Results: We analyzed 424 temperature-guided irradiations in nine eyes of five rabbits. The mean difference between the measured and aim temperature was -0.04°C ± 0.98°C. The following ED50 values for visibility thresholds could be determined: 58.6°C for funduscopic visibility, 57.7°C for fluorescein angiography, and 57.0°C for OCT. In all measurements, the correlation of tissue effect was higher to the temperature than to the average heating laser power used. Conclusions: The system was able to reliably perform temperature-guided irradiations, which allowed for better tissue effect control than simple power control. This approach could enhance the accuracy, safety, and reproducibility of thermal stimulating laser therapy. Translational Relevance: This study is a bridge between preclinical ex vivo experiments and a pilot clinical study.

The neurosurgical benefit of contactless in vivo optical coherence tomography regarding residual tumor detection: A clinical study.

Purpose: In brain tumor surgery, it is crucial to achieve complete tumor resection while conserving adjacent noncancerous brain tissue. Several groups have demonstrated that optical coherence tomography (OCT) has the potential of identifying tumorous brain tissue. However, there is little evidence on human in vivo application of this technology, especially regarding applicability and accuracy of residual tumor detection (RTD). In this study, we execute a systematic analysis of a microscope integrated OCT-system for this purpose. Experimental design: Multiple 3-dimensional in vivo OCT-scans were taken at protocol-defined sites at the resection edge in 21 brain tumor patients. The system was evaluated for its intraoperative applicability. Tissue biopsies were obtained at these locations, labeled by a neuropathologist and used as ground truth for further analysis. OCT-scans were visually assessed with a qualitative classifier, optical OCT-properties were obtained and two artificial intelligence (AI)-assisted methods were used for automated scan classification. All approaches were investigated for accuracy of RTD and compared to common techniques. Results: Visual OCT-scan classification correlated well with histopathological findings. Classification with measured OCT image-properties achieved a balanced accuracy of 85%. A neuronal network approach for scan feature recognition achieved 82% and an auto-encoder approach 85% balanced accuracy. Overall applicability showed need for improvement. Conclusion: Contactless in vivo OCT scanning has shown to achieve high values of accuracy for RTD, supporting what has well been described for ex vivo OCT brain tumor scanning, complementing current intraoperative techniques and even exceeding them in accuracy, while not yet in applicability.

Comparative Treatment Study on Macular Edema Secondary to Branch Retinal Vein Occlusion by Intravitreal Ranibizumab with and without Selective Retina Therapy.

The purpose of this study was to compare the safety and efficacy of selective retina therapy (SRT) combined with the intravitreal injection of ranibizumab (IVR) in patients with macular edema (ME) secondary to branch retinal vein occlusion (BRVO). This trial was a 12-month single-center, randomized, single-masked prospective study. Eligible patients were randomized (1:1) to IVR and SRT (IVR + SRT group), or IVR and sham SRT (IVR + sham group). After the initial IVR, all participants received ME resolution criteria-driven pro re nata treatment. SRT or sham SRT was always applied one day after IVR. The primary outcome measure of this study was the mean change in central macular thickness (CMT) from baseline, and the secondary outcome measures were the mean change in visual acuity from baseline and the number of IVR treatments at a 52-week follow-up. Thirteen patients were in the IVR + SRT group, and 11 were in the IVR + sham group. Compared to the baseline, mean CMT and BCVA improved significantly after 52 weeks in both groups, with no significant difference between the two groups. The mean number of IVR was 2.85 ± 1.52 in the IVR + SRT group and 4.73 ± 2.33 in the IVR + sham group at the 52-week follow-up, with a significant difference between the two groups (p < 0.05). IVR combined with SRT may significantly decrease the number of IVR treatments while maintaining the visual and anatomical improvement effect of IVR monotherapy.

Pulsed thulium laser blood vessel haemostasis as an alternative to bipolar forceps during neurosurgical tumour resection.

Due to wavelength-specific water absorption, infrared lasers like the thulium laser emitting at 1940 nm wavelength proved to be suitable for coagulation in neurosurgery. Commonly bipolar forceps used for intraoperative haemostasis can cause mechanical and thermal tissue damage, whilst thulium laser can provide a tissue-gentle haemostasis through non-contact coagulation. The aim of this work is a less-damaging blood vessel coagulation by pulsed thulium laser radiation in comparison to standard bipolar forceps haemostasis. Ex vivo porcine blood vessels in brain tissue (0.34 ± 0.20 mm diameter) were irradiated in non-contact with a thulium laser in pulsed mode (1940 nm wavelength, 15 W power, 100-500 ms pulse duration), with a CO2 gas flow provided simultaneously at the distal fibre tip (5 L/min). In comparison, a bipolar forceps was used at various power levels (20-60 W). Tissue coagulation and ablation were evaluated by white light images and vessel occlusion was visualised by optical coherence tomography (OCT) B-scans at a wavelength of 1060 nm. Coagulation efficiency was calculated by means of the quotient of the difference between the coagulation and ablation radius to the coagulation radius. Pulsed laser application achieved blood vessel occlusion rate of 92% at low pulse duration of 200 ms with no occurrence of ablation (coagulation efficiency 100%). Bipolar forceps showed an occlusion rate of 100%, however resulted in tissue ablation. Tissue ablation depth with laser application is limited to 40 µm and by a factor of 10 less traumatising than with bipolar forceps. Pulsed thulium laser radiation achieved blood vessel haemostasis up to 0.3 mm in diameter without tissue ablation and has proven to be a tissue-gentle method compared to bipolar forceps.

Assessment of Laser Parameters to Improve Lid Tension-A Proof of Concept towards Lasercanthoplasty.

BACKGROUND: Preliminary clinical work indicates that increasing eyelid tension improves the function of the meibomian glands. The aim of this study was to optimize laser parameters for a minimally invasive laser treatment to increase eyelid tension by coagulation of the lateral tarsal plate and canthus. METHODS: Experiments were performed on a total of 24 porcine lower lids post mortem, with six lids in each group. Three groups were irradiated with an infrared B radiation laser. Laser-induced lower eyelid shortening was measured and the increase in eyelid tension was assessed with a force sensor. A histology was performed to evaluate coagulation size and laser-induced tissue damage. RESULTS: In all three groups, a significant shortening of the eyelids after irradiation was noticed (p < 0.0001). The strongest effect was seen with 1940 nm/1 W/5 s, showing -15.1 ± 3.7% and -2.5 ± 0.6 mm lid shortening. The largest significant increase in eyelid tension was seen after placing the third coagulation. CONCLUSION: Laser coagulation leads to lower eyelid shortening and an increase in lower eyelid tension. The strongest effect with the least tissue damage was shown for laser parameters of 1470 nm/2.5 W/2 s. In vivo studies of this effect have to confirm the efficacy of this concept prior to clinical application.

Differentiation of different stages of brain tumor infiltration using optical coherence tomography: Comparison of two systems and histology.

The discrimination of tumor-infiltrated tissue from non-tumorous brain tissue during neurosurgical tumor excision is a major challenge in neurosurgery. It is critical to achieve full tumor removal since it directly correlates with the survival rate of the patient. Optical coherence tomography (OCT) might be an additional imaging method in the field of neurosurgery that enables the classification of different levels of tumor infiltration and non-tumorous tissue. This work investigated two OCT systems with different imaging wavelengths (930 nm/1310 nm) and different resolutions (axial (air): 4.9 µm/16 µm, lateral: 5.2 µm/22 µm) in their ability to identify different levels of tumor infiltration based on freshly excised ex vivo brain samples. A convolutional neural network was used for the classification. For both systems, the neural network could achieve classification accuracies above 91% for discriminating between healthy white matter and highly tumor infiltrated white matter (tumor infiltration >60%) .This work shows that both OCT systems with different optical properties achieve similar results regarding the identification of different stages of brain tumor infiltration.

Self-Examination Low-Cost Full-Field Optical Coherence Tomography (SELFF-OCT) for neovascular age-related macular degeneration: a cross-sectional diagnostic accuracy study.

OBJECTIVES: Self-Examination Low-Cost Full-Field Optical Coherence Tomography (SELFF-OCT) is a novel OCT technology that was specifically designed for home monitoring of neovascular age-related macular degeneration (AMD). First clinical findings have been reported before. This trial investigates an improved prototype for patients with AMD and focusses on device operability and diagnostic accuracy compared with established spectral-domain OCT (SD-OCT). DESIGN: Prospective single-arm diagnostic accuracy study. SETTING: Tertiary care centre (University Eye Clinic). PARTICIPANTS: 46 patients with age-related macular degeneration. INTERVENTIONS: Patients received short training in device handling and then performed multiple self-scans with the SELFF-OCT according to a predefined protocol. Additionally, all eyes were examined with standard SD-OCT, performed by medical personnel. All images were graded by at least 2 masked investigators in a reading centre. PRIMARY OUTCOME MEASURE: Rate of successful self-measurements. SECONDARY OUTCOME MEASURES: Sensitivity and specificity of SELFF-OCT versus SD-OCT for different biomarkers and necessity for antivascular endothelial growth factor (anti-VEGF) treatment. RESULTS: In 86% of all examined eyes, OCT self-acquisition resulted in interpretable retinal OCT volume scans. In these patients, the sensitivity for detection of anti-VEGF treatment necessity was 0.94 (95% CI 0.79 to 0.99) and specificity 0.95 (95% CI 0.82 to 0.99). CONCLUSIONS: SELFF-OCT was used successfully for retinal self-examination in most patients, and it could become a valuable tool for retinal home monitoring in the future. Improvements are in progress to reduce device size and to improve handling, image quality and success rates. TRIAL REGISTRATION NUMBER: DRKS00013755, CIV-17-12-022384.

Registration of histological brain images onto optical coherence tomography images based on shape information.

Identifying tumour infiltration zones during tumour resection in order to excise as much tumour tissue as possible without damaging healthy brain tissue is still a major challenge in neurosurgery. The detection of tumour infiltrated regions so far requires histological analysis of biopsies taken from at expected tumour boundaries. The gold standard for histological analysis is the staining of thin cut specimen and the evaluation by a neuropathologist. This work presents a way to transfer the histological evaluation of a neuropathologist onto optical coherence tomography (OCT) images. OCT is a method suitable for real timein vivoimaging during neurosurgery however the images require processing for the tumour detection. The method demonstrated here enables the creation of a dataset which will be used for supervised learning in order to provide a better visualization of tumour infiltrated areas for the neurosurgeon. The created dataset contains labelled OCT images from two different OCT-systems (wavelength of 930 nm and 1300 nm). OCT images corresponding to the stained histological images were determined by shaping the sample, a controlled cutting process and a rigid transformation process between the OCT volumes based on their topological information. The histological labels were transferred onto the corresponding OCT images through a non-rigid transformation based on shape context features retrieved from the sample outline in the histological image and the OCT image. The accuracy of the registration was determined to be 200 ± 120µm. The resulting dataset consists of 1248 labelled OCT images for each of the two OCT systems.

Algorithms for optoacoustically controlled selective retina therapy (SRT).

OBJECTIVES: Selective Retina Therapy (SRT) uses microbubble formation (MBF) to target retinal pigment epithelium (RPE) cells selectively while sparing the neural retina and the choroid. Intra- and inter-individual variations of RPE pigmentation makes frequent radiant exposure adaption necessary. Since selective RPE cell disintegration is ophthalmoscopically non-visible, MBF detection techniques are useful to control adequate radiant exposures. It was the purpose of this study to evaluate optoacoustically based MBF detection algorithms. METHODS: Fifteen patients suffering from central serous chorioretinopathy and diabetic macula edema were treated with a SRT laser using a wavelength of 527 nm, a pulse duration of 1.7 µs and a pulse energy ramp (15 pulses, 100 Hz repetition rate). An ultrasonic transducer for MBF detection was embedded in a contact lens. RPE damage was verified with fluorescence angiography. RESULTS: An algorithm to detect MBF as an indicator for RPE cell damage was evaluated. Overall, 4646 irradiations were used for algorithm optimization and testing. The tested algorithms were superior to a baseline model. A sensitivity/specificity pair of 0.96/1 was achieved. The few false algorithmic decisions were caused by unevaluable signals. CONCLUSIONS: The algorithm can be used for guidance or automatization of microbubble related treatments like SRT or selective laser trabeculoplasty (SLT).

Fluorescence Lifetime Changes Induced by Laser Irradiation: A Preclinical Study towards the Evaluation of Retinal Metabolic States.

Fluorescence Lifetime (FLT) of intrinsic fluorophores may alter under the change in metabolic state. In this study, the FLT of rabbit retina was investigated in vivo after laser irradiation using fluorescence lifetime imaging ophthalmoscopy (FLIO). The retina of the Chinchilla bastard rabbits was irradiated with a 514 nm diode laser. FLIO, fundus photography, and optical coherence tomography (OCT) were conducted 30 min and 1 to 3 weeks after treatment. After strong coagulation, the FLT at laser spots was significantly elongated immediately after irradiation, conversely shortened after more than a week. Histological examination showed eosinophilic substance and melanin clumping in subretinal space at the coagulation spots older than one week. The FLT was also elongated right around the coagulation spots, which corresponded to the discontinuous ellipsoid zone (EZ) on OCT. This EZ change was recovered after one week, and the FLT became the same level as the surroundings. In addition, there was a region around the laser spot where the FLT was temporarily shorter than the surrounding area. When weak pulse energy was applied to selectively destroy only the RPE, a shortening of the FLT was observed immediately around the laser spot within one week after irradiation. FLIO could serve as a tool to evaluate the structural and metabolic response of the retina to laser treatments.

Factors affecting resolution of subretinal fluid after selective retina therapy for central serous chorioretinopathy.

The purpose of this study was to investigate the factors of clinical outcome of selective retina therapy (SRT) for central serous chorioretinopathy (CSC). This retrospective study included 77 eyes of 77 patients, who were treated with SRT for CSC and observed at least 6 months after the treatment. SRT laser (527 nm, 1.7 µs, 100 Hz) was used for treatment. The mean best-corrected visual acuity (logMAR), central macular thickness (CMT) and central choroidal thickness were changed from baseline to at 6-months follow-up with significant difference. The multivariate analyses found that the rate of change (reduction) in CMT was associated with focal leakage type on fluorescein angiography (FA) (p = 0.03, coefficient 15.26, 95% confidence interval 1.72-28.79) and larger baseline CMT (p < 0.01, coefficient - 0.13, 95% confidence interval - 0.13 to - 0.05). Complete resolution of subretinal fluid was associated with nonsmoking history (p = 0.03, odds ratio 0.276, 95% confidence interval 0.086-0.887) and focal leakage type on FA (p < 0.01, odds ratio 0.136, 95% confidence interval 0.042-0.437). These results may be useful for predicting the therapeutic effectiveness of SRT.

Investigations on Retinal Pigment Epithelial Damage at Laser Irradiation in the Lower Microsecond Time Regime.

Purpose: New lasers with a continuous wave power exceeding 15 W are currently investigated for retinal therapies, promising highly localized effects at and close to the Retinal Pigment Epithelium (RPE). The goal of this work is to evaluate mechanisms and thresholds for RPE cell damage by means of pulse durations up to 50 µs. Methods: A diode laser with a wavelength of 514 nm, a power of 15 W, and adjustable pulse durations between 2 µs and 50 µs was used. Porcine RPE-choroidal explants (ex vivo) and chinchilla bastard rabbits (in vivo) were irradiated to determine threshold radiant exposures for RPE damage \({\bar H_{Cell}}\) by calcein vitality staining and fluorescence angiography, respectively. Thresholds for microbubble formation (MBF) \({\bar H_{MBF}}\) were evaluated by time-resolved optoacoustics. Exemplary histologies support the findings. Results: \({\bar H_{{{MBF}}}}\) is significantly higher than \({\bar H_{Cell}}\) at pulse durations ≥ 5 µs (P < 0.05) ex vivo, while at 2 µs, no statistically significant difference was found. The ratios between \({\bar H_{{{MBF}}}}\) and \({\bar H_{Cell}}\) increase with pulse duration from 1.07 to 1.48 ex vivo and 1.1 to 1.6 in vivo, for 5.2 and 50 µs. Conclusions: Cellular damage with and without MBF related disintegration are both present and very likely to play a role for pulse durations ≥ 5 µs. With the lower µs pulses, selective RPE disruption might be possible, while higher values allow achieving spatially limited thermal effects without MBF. However, both modi require a very accurate real-time dosing control in order to avoid extended retinal disintegration in this power range.

Self-examination low-cost full-field OCT (SELFF-OCT) for patients with various macular diseases.

PURPOSE: The treatment guidelines for many macular diseases rely on frequent monitoring with optical coherence tomography (OCT). However, the burden of frequent disease control leads to low therapy adherence in real life. OCT home monitoring would address this issue but requires an inexpensive and self-operable device. With self-examination low-cost full-field OCT (SELFF-OCT), our group has introduced a novel technology that may fulfill both requirements. In this pilot study, we report the initial experiences with a clinical prototype. METHODS: Fifty-one patients with different macular diseases were recruited in a cross-sectional study. The most common diseases were age-related macular degeneration (AMD; 39/51), diabetic macular edema (DME; 6/51), and retinal vein occlusion (RVO; 3/51). Patients received a short training in device usage and then performed multiple self-scans with the SELFF-OCT device. For comparison, scans with a standard clinical spectral domain (SD-)OCT were taken. RESULTS: After a brief training, 77% of the patients were able to successfully acquire images that were clinically gradable. No significant influence on success could be found for age (p = 0.08) or BCVA (p = 0.97). Relevant disease biomarkers in the most common retinal diseases could be detected. CONCLUSIONS: SELFF-OCT was used successfully for retinal self-examination and in the future could be used for retinal home monitoring. Future improvements in technology are expected to improve success rates and image quality. TRIAL REGISTRATION: The Trial was registered in the German Trial Register under the number DRKS00013755 on 14.03.2018.

Selective retina therapy (SRT) for macular serous retinal detachment associated with tilted disc syndrome.

PURPOSE: Tilted disc syndrome (TDS) may be associated with a macular serous retinal detachment (MSRD). However, ideal therapy for this complication is still unestablished yet to date. The purpose of this study is to investigate the effect of selective retina therapy (SRT) for MSRD associated with TDS. METHODS: This retrospective study included 11 eyes of 10 patients (1 male and 9 females), who were treated with SRT for MSRD associated with TDS, and observed at least 12 months after treatment. The mean age was 56 years old (range 44-66). An SRT laser (527 nm, 1.7 µs, 100 Hz; Medical Laser Center Lübeck, Germany) was used for treatment. The changes of best-corrected visual acuity (BCVA), central macular thickness (CMT), and central choroidal thickness (CCT) were examined. Subfoveal curve height (SFCH) was calculated at baseline. RESULTS: The mean follow-up period was 24.4 months (range 12-48 months). The mean BCVA (logMAR), CMT, and CCT changed from 0.03 ± 0.10, 324 ± 82 µm, and 194 ± 68 µm preoperatively to 0.07 ± 0.17, 274 ± 94 µm, and 188 ± 65 µm at final follow-up, respectively, with significant difference on CMT (BCVA: p = 0.44, CMT: p < 0.05, CCT: p = 0.21). The MSRD disappeared in 6 eyes (55%) and the average number of SRT irradiations until resolution of MSRD was 2.6 times (range 1-5 times). There was no significant association between SFCH and resolution of MSRD (p = 0.19). CONCLUSIONS: SRT may promote absorption of MSRD and maintenance of BCVA for TDS. Randomized and prospective clinical studies are needed to evaluate the effectiveness of SRT for MSRD associated with TDS.

An Intraoral OCT Probe to Enhanced Detection of Approximal Carious Lesions and Assessment of Restorations.

Caries, the world's most common chronic disease, remains a major cause of invasive restorative dental treatment. To take advantage of the diagnostic potential of optical coherence tomography (OCT) in contemporary dental prevention and treatment, an intraorally applicable spectral-domain OCT probe has been developed based on an OCT hand-held scanner equipped with a rigid 90°-optics endoscope. The probe was verified in vitro. In vivo, all tooth surfaces could be imaged with the OCT probe, except the vestibular surfaces of third molars and the proximal surface sections of molars within a "blind spot" at a distance greater than 2.5 mm from the tooth surface. Proximal surfaces of 64 posterior teeth of four volunteers were assessed by intraoral OCT, visual-tactile inspection, bitewing radiography and fiber-optic transillumination. The agreement in detecting healthy and carious surfaces varied greatly between OCT and established methods (18.2-94.7%), whereby the established methods could always be supplemented by OCT. Direct and indirect composite and ceramic restorations with inherent imperfections and failures of the tooth-restoration bond were imaged and qualitatively evaluated. The intraoral OCT probe proved to be a powerful technological approach for the non-invasive imaging of healthy and carious hard tooth tissues and gingiva as well as tooth-colored restorations.

Selective retina therapy for subretinal fluid associated with choroidal nevus.

PURPOSE: To report a case of a patient with subretinal fluid (SRF) associated with choroidal nevus (CN), who was treated with selective retina therapy (SRT) and ultimately achieved resolution of the SRF. OBSERVATIONS: A 41-year-old man with SRF associated with CN in his right eye (RE) underwent ophthalmologic evaluation, including optic coherence tomography, fluorescein angiography (FA) and indocyanine green angiography. The best corrected visual acuity (BCVA) converted to the logarithm of the minimum angle of resolution (logMAR) was 0.00 in the RE. SRT (532 nm, 1.7 µs pulse duration, 30 pulses in 100Hz; Medical Laser Center Lübeck) was performed with the laser spots equally distributed across the FA leakage area. Until 20 months SRT was repeated several times because the SRF decreased every time in response to SRT, but was not completely resolved and sometimes increased with time. After performing 6 times of SRT session, leakage on FA stopped at 21 months follow-up and SRF was resolved at 31 months. At 60 months after the first SRT, there were no signs of malignant transformation, no SRF, and the BCVA in the RE was 0.22. CONCLUSIONS AND IMPORTANCE: SRT seems to be a useful treatment and proper clinical studies are necessary to establish the best treatment protocol for SRF associated with CN.

Predictive factors of outcome of selective retina therapy for diabetic macular edema.

PURPOSE: To investigate the predictive factors of clinical outcome of selective retina therapy (SRT) for diabetic macular edema (DME). METHODS: This retrospective study included 22 eyes of 22 patients (15 males and 7 females), who were treated with SRT for DME at the Department of Ophthalmology of Osaka City University Hospital and observed at least 6 months after the treatment. The mean age was 64 years (range 40-81). Thirteen of the 22 eyes (59%) had a treatment history other than SRT before. SRT laser (527 nm, 1.7 µs, 100 Hz) was used for treatment. Changes in the best-corrected visual acuity (BCVA) (logMAR) and central macular thickness (CMT) in optical coherence tomography were examined at baseline, 3-month follow-up, and 6-month follow-up. Factors associated with the rate of change in CMT at 3 and 6 months after SRT were examined. RESULTS: The mean BCVA (logMAR) was 0.26 ± 0.31, 0.22 ± 0.27 and 0.23 ± 0.29 at baseline, 3 months and 6 months, respectively (p = 0.15 at 3 months, 0.40 at 6 months; compared to baseline). The mean CMT was 502 ± 163, 493 ± 204, and 416 ± 185 µm at baseline, 3 months, and 6 months, respectively (p = 0.69 at 3 months, 0.01 at 6 months; compared to baseline). The multivariate analysis found a significant negative association with previous macular photocoagulation (p = 0.03) at 3 months and a positive association with a history of insulin use (p = 0.02) and previous panretinal photocoagulation (p = 0.03) at 6 months after SRT. CONCLUSION: The CMT was significantly decreased at 6 months after SRT in DME. The history of insulin use and panretinal photocoagulation may positively and the history of macular photocoagulation may negatively affect the outcome of SRT, which must be considered when determining the therapeutic indications for SRT.

Fluorescence Lifetime Imaging Ophthalmoscopy of the Retinal Pigment Epithelium During Wound Healing After Laser Irradiation.

PURPOSE: To investigate the change in fluorescence lifetime of retinal pigment epithelium (RPE) after laser irradiation by using an organ culture model. METHODS: Porcine RPE-choroid-sclera explants were irradiated with selective retina treatment laser (wavelength: 527 nm, beam diameter: 200 µm, energy: 80-150 µJ). At 24 and 72 hours after irradiation, the mean fluorescence lifetime (τm ) was measured with fluorescence lifetime imaging ophthalmoscopy (FLIO) (excitation wavelength: 473 nm, emission: short spectral channel: 498-560 nm, long spectral channel: 560-720 nm). For every laser spot, central damaged zone (zone 1: 120 × 120 µm), area including wound rim (280 × 280 µm except zone 1), and environmental zone (440 × 440 µm except zone 1 and 2) were analyzed. Peripheral zone at a distance from laser spots longer than 2000 µm was examined for comparison. Cell viability was evaluated with calcein-acetoxymethyl ester and morphology with fluorescence microscopy for filamentous-actin. RESULTS: The RPE defect after selective retina treatment was mostly closed within 72 hours. FLIO clearly demarcated the irradiated region, with prolonged τm at the center of the defect decreasing with eccentricity. In short spectral channel, but not in long spectral channel, τm in the environmental zone after 72 hours was still significantly longer than in the peripheral zone. CONCLUSIONS: FLIO may clearly demarcate the RPE defect, demonstrate its closure, and, moreover, indicate the induced metabolic changes of surrounding cells during wound healing. TRANSLATIONAL RELEVANCE: This ex vivo study showed that FLIO may be used to evaluate the extent and quality of restoration of the damaged RPE and to detect its metabolic change in human fundus noninvasively.

Real-time optoacoustic temperature determination on cell cultures during heat exposure: a feasibility study.

Objective/Purpose: In order to study the effects of hyperthermia and other temperature-related effects on cells and tissues, determining the precise time/temperature course is crucial. Here we present a non-contact optoacoustic technique, which provides temperatures during heating of cultured cells with scalable temporal and spatial resolution. METHODS: A thulium laser (1.94 µm) with a maximum power of 15 W quickly and efficiently heats cells in a culture dish because of low penetration depth (1/e penetration depths of 78 µm) of the radiation in water. A repetitively Q-switched holmium laser (2.1 µm) is used simultaneously to probe temperatures at different locations in the dish by using the photoacoustic effect. Due to thermoelastic expansion of water, pressure waves are emitted and measured with an ultrasonic hydrophone at the side of the dish. The amplitudes of the waves are temperature dependent and can be used to calculate the temperature/time course at any location of probing. RESULTS: We measured temperatures of up to 55 °C with a heating power of 6 W after 10 s, and subsequent lateral temperature profiles over time. Within this profile, temperature fluctuations were found, likely owing to thermal convection and water circulation. By using cultured retinal pigment epithelial cells, it is shown that the probe laser pulses alone cause no biological damage, while immediate cell damage occurs when heating for 10 s at temperatures exceeding 45 °C. CONCLUSIONS: This method shows great potential not only as a noninvasive, non-contact method to determine temperature/time responses of cells in culture, but also for complex tissue and other materials.