Retinal Laser Treatment Research Articles

Variability of thermal subthreshold retinal laser treatment plans

To investigate the variability in subthreshold laser treatment plans for patients with diabetic macular edema or central serous chorioretinopathy. Diagnostic images from 20 patients were utilized, and 25 retina specialists generated subthreshold treatment plans along with a self-rated experience level. Evaluation comprised of i) Area Variability (AV): quantifies the consensus regarding the covered area and is the difference between the areas planned by 75% and 25% of the participants ii) mean Centroid Distance (CD): level of agreement on the localization of a treatment. Subgroup analysis investigated the impact of participants’ experience levels, utilizing the Mann-Whitney-Wilcoxon test. The predominant plan style is a targeted treatment approach (92%) and avoidance of subfoveal region (89%). Mean CD is 71.0 ± 37.5 pixels (≈half disc diameter) and mean AV is 9.8%±8.9%. A slight difference is observed between the 50-75% areas, but a notable distinction exists between the 25-50% areas. Subgroup analysis revealed CD and AV value of 75.9 pixels and 24% in the lower experience level group as opposed to 55.9 pixels and 8.6% in the higher experience level group. There is significant variability in treatment planning which reduces with increased experience of retina specialists. While consensus is observed around focal points, differences in the surrounding extents persist.

Model Predictive Temperature Control for Retinal Laser Treatments.

Manual, individual adjustment of the laser power in retinal laser therapies is time-consuming, is inaccurate with respect to uniform effects, and can only prevent over- or undertreatment to a limited extent. Automatic closed-loop temperature control allows for similar temperatures at each irradiated spot despite varying absorption. This is of crucial importance for subdamaging hyperthermal treatments with no visible effects and the safety of photocoagulation with short irradiation times. The aim of this work is to perform extensive experiments on porcine eye explants to demonstrate the benefits of automatic control in retinal laser treatments. To ensure a safe and reliable temperature rise, we utilize a model predictive controller. For model predictive control, the current state and the spot-dependent absorption coefficients are estimated by an extended Kalman filter (EKF). Therein, optoacoustic measurements are used to determine the temperature rise at the irradiated areas in real time. We use fluorescence vitality stains to measure the lesion size and validate the proposed control strategy. By comparing the lesion size with temperature values for cell death, we found that the EKF accurately estimates the peak temperature. Furthermore, the proposed closed-loop control scheme works reliably with regard to similar lesion sizes despite varying absorption with a smaller spread in lesion size compared to open-loop control. Our closed-loop control approach enables a safe subdamaging treatment and lowers the risk for over- and undertreatment for mild coagulations in retinal laser therapies. We demonstrate that modern control strategies have the potential to improve retinal laser treatments for several diseases.

Detection sensitivity of fluorescence lifetime imaging ophthalmoscopy for laser-induced selective damage of retinal pigment epithelium

PurposeTo investigate the sensitivity of fluorescence lifetime imaging ophthalmoscopy (FLIO) to detect retinal laser spots by comparative analysis with other imaging modalities.MethodsA diode laser with a wavelength of 514 nm was applied with pulse durations of 5.2, 12, 20, and 50 µs. The laser pulse energy was increased so that the visibility of the laser spot by slit-lamp fundus examination (SL) under the irradiator’s observation covers from the subvisible to visible range immediately after irradiation. The irradiated areas were then examined by fundus color photography (FC), optical coherence tomography (OCT), fundus autofluorescence (AF), FLIO, and fluorescein angiography (FA). The visibility of a total of over 2200 laser spots was evaluated by two independent researchers, and effective dose (ED) 50 laser pulse energy values were calculated for each imaging modality and compared.ResultsAmong examined modalities, FA showed the lowest mean of ED50 energy value and SL the highest, that is, they had the highest and lowest sensitivity to detect retinal pigment epithalium (RPE)-selective laser spots, respectively. FLIO also detected spots significantly more sensitively than SL at most laser pulse durations and was not significantly inferior to FA. AF was also often more sensitive than SL, but the difference was slightly less significant than FLIO.ConclusionConsidering its high sensitivity in detecting laser spots and previously reported potential of indicating local wound healing and metabolic changes around laser spots, FLIO may be useful as a non-invasive monitoring tool during and after minimally invasive retinal laser treatment.

Retinal biomarkers in vascular occlusion

Objective: To clarify the diagnostic and prognostic values of the biomarkers detected by multimodal imaging procedures as coloured fundus imaging, fluorescein angiography, near infra‐red imaging, fundus Autofluorescence, SD‐OCT, and OCT angiography to predict the prognosis and the response to therapy in retinal vascular occlusions (artery or vein).Recently, there has been an interest in determining the prognostic value of changes on optical coherence tomography (OCT) in retinal vein occlusion as it allows both quantitative and qualitative analysis of imaging biomarkers such as central retinal thickness, choroidal thickness, intraretinal hyper‐reflective foci (HRF), disorganization of the inner retinal layers (DRIL), external limiting membrane (ELM) disruption, ellipsoid zone (EZ) disruption. Also classifying the intraretinal edema if sponge‐like or cystoid or serous retinal detachment (and detecting its height). Also signs of ischemia can be detected such as prominent middle limiting membrane (p‐MLM), paracentral acute middle maculopathy (PAMM), as well as hyperreflectivity of the inner retinal layers (HIRL) which is commonly seen in cases of acute retinal artery occlusion. Internal limiting membrane detachment (ILMD) which is a novel biomarker that can be detected in some cases of acute CRAO.OCT Angiography has added more information about the assessment of microvascular alterations, especially vessel density in the deep retinal vascular plexus, the foveal avascular zone and of areas with no capillary perfusion. Biomarkers of ultra‐widefield angiography, such as peripheral ischemia (ischemic index) and neovascularization are essential for retinal laser treatment decision.Finally, FAF has been a very useful tool in monitoring the disease progression and response to treatment.The speaker will present examples of multimodal imaging of different retinal biomarkers in retinal vascular occlusion that help in predicting the prognosis.

Классификации периферических дистрофий сетчатки

Purpose. To analyze the existing classifications of peripheral retinal dystrophies. Material and methods. While writing a literature review, a search was made for data from domestic and foreign literature, mostly in the last 20 years. The search was carried out using the following keywords: «peripheral retinal dystrophies», «retinal detachment», «laser coagulation», «lattice degeneration». In total, 20 articles were selected that relate to the topic of this literature review. Results. Retinal detachment is a severe pathology leading to a significant reduction or loss of vision. Peripheral retinal dystrophies play a leading role in the development of retinal detachment. The leading role in the development of rhegmatogenous forms of peripheral degenerations is assigned to changes in the vitreous body with a traction effect on the retina. The question of the incidence of retinal detachment in its dystrophies remains debatable. In publications, we came across a large number of classifications of peripheral retinal dystrophies, covering from 8 to 20 different clinical forms. The question of which retinal dystrophies are predisposing or not predisposing to retinal detachment remains open. Visualization of the vitreoretinal interface in peripheral degenerations is relevant for determining treatment tactics. Optical coherence tomography is highly informative in the early diagnosis of the traction component, visualization of retinal tears and detachment, and determination of indications for laser coagulation of the retina. Conclusion. Retinal detachment is a severe pathology leading to a significant reduction or loss of vision. Peripheral retinal dystrophies play a leading role in the development of retinal detachment. The question of the incidence of retinal detachment in its dystrophies remains debatable. The issue of creating a working classification that reflects the morphology of the degenerative process and indications for laser treatment remains relevant. Key words: peripheral retinal dystrophy, retinal detachment, retinal laser treatment, lattice degeneration

Lasers in Medicine: The Changing Role of Therapeutic Laser-Induced Retinal Damage—From de rigeuer to Nevermore

For over five decades, laser-induced retinal damage (LIRD) was thought to be the necessary cost of all therapeutic effects of laser treatment for the most important causes of irreversible visual loss, the chronic progressive retinopathies (CPRs). The development of modern retinal laser therapy with the discovery of “low-intensity/high-density subthreshold micropulse” laser (SDM) showed that the supposed need for LIRD represented a case of confusing association with causation. This revealed that LIRD was unnecessary and detrimental to clinical outcomes, and thus, contraindicated as the most severe complication of retinal laser treatment. SDM allowed for an understanding of the mechanism of retinal laser treatment as a physiologic reset effect, triggered by heat-shock protein (HSP) activation upregulating the unfolded protein response and restoring proteostasis by increasing protein repair by 35% in dysfunctional cells via a thermally sensitive conformational change in the K10 step of HSP activation kinetics. Because HSP activation kinetics are catalytic, even low levels (the “reset” threshold) of HSP activation result in a maximal treatment response. SDM and the study of HSP activation kinetics in the retina show that the therapeutic effects of retinal laser treatment can be fully realized without any degree of LIRD. Besides LIRD, all effects of retinal laser treatment are restorative and therapeutic, without any known adverse treatment effects. Without LIRD, the benefits of retinal laser treatment are infinitely renewable and direct treatment of the fovea is possible. Elimination of LIRD from retinal laser treatment has revolutionized the clinical potential of retinal laser treatment to broaden treatment indications to permit, for the first time, effective early and preventive treatment to reduce visual loss from the most frequent causes of irreversible visual loss worldwide, the CPRs.

Role of deferred retinal laser following intravitreal injection of bevacizumab in treatment of severe retinopathy of prematurity.

The purpose is to determine the advantages and role of supplemental deferred retinal laser treatment following intravitreal bevacizumab (IVB) monotherapy in cases of severe retinopathy of prematurity (ROP) requiring treatment. This is a retrospective study involving preterm infants diagnosed with treatment requiring ROP, treated initially with bevacizumab monotherapy who subsequently received deferred laser treatment during the study period from April 2019 to March 2021. Deferred laser treatment was done when recurrence of ROP or plus disease was noted or nonprogression of retinal vasculature was noted on two consecutive examinations over 2 weeks. The main outcomes measured were the ability of the treatment to prevent ROP progression or recurrence and anatomic outcome at the last follow-up visit. Twenty-three eyes of 14 neonates were treated with a deferred laser treatment following the initial intravitreal injection of Bevacizumab. The mean postmenstrual age at which IVB was given was 34+6 ± 1+3 weeks. The mean duration between IVB and retinal laser was 5+3 ± 3+4 weeks. The mean weight at the time of injection was 1317.8 ± 231.8 g. The mean weight of the infants at the time of the laser was 2050 ± 813.9 g. None of the eyes developed recurrence or adverse anatomical outcomes following laser till the last available follow-up. In our small number of subjects, blinding complications of ROP were prevented by using a deferred laser treatment protocol following initial bevacizumab therapy in treatment requiring ROP. It is better suited in cases where compliance for long-term follow-up after bevacizumab therapy cannot be ensured.

LATE CHOROIDAL NEOVASCULAR COMPLICATIONS IN A PATIENT TREATED FOR RETINOBLASTOMA. A CASE REPORT.

Case report of choroidal neovascularization (CNV) detection in patient who was treated for bilateral retinoblastoma in early childhood. Patient at 1.5 years of age treated for endophytic retinoblastoma stage 4 (according to the Reese-Ellsworth classification) bilaterally, with a positive mutation in the Rb1 gene. After undergoing bilateral retinal laser treatment and 6 cycles of systemic chemotherapy, the tumor remained inactive without other complications. At the age of 14, the boy developed visual impairment in his left eye with metamorphosis. Based on a local finding and other auxiliary examinations, he was diagnosed with CNV in the macular area at the interface of the tumor scar and the healthy retina of the left eye. After three applications of anti-VEGF (antibodies blocking vascular endothelial growth factor) substance intravitreally (bevacizumab 1.2 mg), there was a reduction in CNV and also an improvement in visual function.

Model predictive control for retinal laser treatment at 1 kHz

Abstract Laser photocoagulation is a technique applied in the treatment of retinal disease, which is often done manually or using simple control schemes. We pursue an optimization-based approach, namely Model Predictive Control (MPC), to enforce bounds on the peak temperature and, thus, to ensure safety during the medical treatment procedure – despite the spot-dependent absorption of the tissue. The desired laser repetition rate of 1 kHz is renders the requirements on the computation time of the MPC feedback a major challenge. We present a tailored MPC scheme using parametric model reduction, an extended Kalman filter for the parameter and state estimation, and suitably tuned stage costs and verify its applicability both in simulation and experiments with porcine eyes. Moreover, we give some insight on the implementation specifically tailored for fast numerical computations.

Decision-making support system for the personalization of retinal laser treatment in diabetic retinopathy

In this work, we propose a decision-making support system for automatically mapping an effective photocoagulation pattern for the laser treatment of diabetic retinopathy. The purpose of research to create automated personalization of diabetic macular edema laser treatment. The results are based on analysis of large semi-structured data, methods and algorithms for fundus image processing. The technology improves the quality of retina laser coagulation in the treatment of diabetic macular edema, which is one of the main reasons for pronounced vision decrease. The proposed technology includes original solutions to establish an optimal localization of multitude burns by determining zones exposed to laser. It also includes the recognition of large amount of unstructured data on the anatomical and pathological locations' structures in the area of edema and data optical coherent tomography. As a result, a uniform laser application on the pigment epithelium of the affected retina is ensured. It will increase the treatment safety and its effectiveness, thus avoiding the use of more expensive treatment methods. Assessment of retinal lesions volume and quality will allow predicting the laser photocoagulation results and will contribute to the improvement of laser surgeon's skills. The architecture of a software complex comprises a number of modules, including image processing methods, algorithms for photocoagulation pattern mapping, and intelligent analysis methods.

Parameter estimation and model reduction for model predictive control in retinal laser treatment

Laser photocoagulation is one of the most frequently used treatment approaches for retinal diseases such as diabetic retinopathy and macular edema. The use of model-based control, such as Model Predictive Control (MPC), enhances a safe and effective treatment by guaranteeing temperature bounds. In general, real-time requirements for model-based control designs are not met since the temperature distribution in the eye fundus is governed by a heat equation with a nonlinear parameter dependency. This issue is circumvented by representing the model by a lower-dimensional system which well-approximates the original model, including the parametric dependency. We combine a global-basis approach with the discrete empirical interpolation method, tailor its hyperparameters to laser photocoagulation, and show its superiority in comparison to a recently proposed method based on Taylor-series approximation. Its effectiveness is measured in computation time for MPC. We further present a case study to estimate the range of absorption parameters in porcine eyes, and by means of a theoretical and numerical sensitivity analysis we show that the sensitivity of the temperature increase is higher with respect to the absorption coefficient of the retinal pigment epithelium (RPE) than of the choroid’s.

Telomeres do not always shorten over time in individuals with type 1 diabetes

AimsWe aimed to determine how white blood cell (WBC) telomeres and telomere length change over time are associated with health status in type 1 diabetes. MethodsRelative telomere length (rTL) was measured in WBC DNA from two time-points (median 6.8 years apart) in 618 individuals from the Finnish Diabetic Nephropathy Study by quantitative PCR, with interassay CV ≤ 4%. ResultsBaseline rTL correlated inversely with age and was shorter in men. Individuals in the shortest vs. longest rTL tertile had adverse cardiometabolic profiles, worse renal function, and were prescribed more antihypertensive and lipid-lowering drugs. While overall rTL tended to decrease during the median 6.8-years of follow-up, telomeres shortened in 55.3% of subjects, lengthened in 40.0%, and did not change in 4.7%. Baseline rTL correlated inversely with rTL change. Telomere lengthening was associated with higher HDL-Cholesterol (HDL-C), HDL-C/ApoA1, and with antihypertensive drug and (inversely) with lipid-lowering drug commencement during follow-up. Correlates of rTL percentage change per-annum (adjusted model) were baseline BMI, eGFR, previous retinal laser treatment, HDL-C, and HDL-C/ApoA1. ConclusionsTelomere length measurements may facilitate the treatment and monitoring of the health status of individuals with type 1 diabetes.

Late contralateral recurrence of retinal detachment in incontinentia pigmenti: A case report

BACKGROUNDIncontinentia pigmenti (IP) is a rare X-linked genetic disease. It mainly manifests as skin lesions and causes problems in the eyes, teeth, bones, and central nervous system. Of the various ocular manifestations, the most severe with difficult recovery is retinal detachment (RD). Here, we report an unusual case of bilateral asymmetrical RD. CASE SUMMARYWe present the case of an 11-year-old Chinese girl with IP who complained of sudden blurring of vision in the left eye. At that time, she had been blind in her right eye for 4 years. RD with traction was observed in both eyes. A massive retinal proliferative membrane, exudation, and hemorrhage were seen in the left eye. We performed vitrectomy in her left eye. Her visual acuity recovered to 20/50, and her retina had flattened within 2 d after surgery. During the 3-mo follow-up, we performed retinal laser treatment of the non-perfused retinal area in her left eye. Eventually, her visual acuity returned to 20/32, and no new retinal abnormalities developed. CONCLUSIONIn patients with IP with fundal abnormalities in one eye, it is important to focus on the rate of fundal change in the other eye. RD in its early stages can be effectively treated with timely vitrectomy and laser photocoagulation.

Центральная серозная хориоретинопатия: навигационное лечение NAVILAS 577S

Central serous chorioretinopathy (CSC) is a common retinal disease whose etiology and pathogenesis remain largely ambiguous. Subthreshold micropulsed laser (SMILV) treatment has been intensively used for the treatment of CSC over the last decade. Purpose. To develop a method for the treatment of macular edema in CSC by subthreshold micropulse laser exposure on the Navilas 577s navigation laser system. Material and methods. The study included 65 subjects (65 eyes), 32 to 54 years of age, with acute and chronic CSC. All patients underwent standard ophthalmological examination and additional examinations including: optical coherence tomography (OCT) Topcon DRI OCT Triton and OCT-A, Maia microperimetry, autofluorescence of the eye with Zeiss Clarus 500 wide angle imaging system. Treatment was performed by SMILV using Navilas 577s system in patients with acute and chronic forms. Results. The main criteria for the effectiveness of the treatment were: an increase in maximum corrected visual acuity (BCVA), a decrease in neuroepithelial detachment (ONE) and its attachment speed, a decrease in retinal thickness and an improvement in photosensitivity (SF). Conclusion. In the treatment of CSC, preference is given to SMILV exposure, which has a physiotherapeutic effect without visible damage to the retina. The Navilas 577s navigation laser system achieves the highest precision and efficiency in retinal laser treatment, while significantly reducing procedure time and patient discomfort. Keywords: central serous chorioretopathy (CSC), subthreshold micropulse laser exposure (SML), neuroepithelial detachment, Navilas 577s.

Mélanome choroïdien: gare aux formes asymptomatiques et atypiques!

We report the case of a 60-year-old patient with a history of barrage laser for undocumented retinal detachment in the left eye presenting with myodesopsias. Assessment showed corrected visual acuity 10/10 OU. Funduscopic examination of the left eye showed the typical effects of retinal laser treatment with very peripheral nasal double-bump achromatic lesion (A,C). Orbit MRI objectified the presence of intraocular nasal mass located between the supero and infero-inner quadrants, measuring 8x3 mm, with hyposignal on T2- weighted images, intensively and homogeneously enhanced after injection of gadolinium (D). This mass suggested the diagnosis of left choroidal melanoma. Assessment did not objectify any locoregional and distant spread. Given the anterior involvement and the small size of the tumor, the patient was referred for iodine-125 brachytherapy. Choroidal melanoma is the most common intraocular tumor in adults. The severity of this cancer is associated with a risk of metastases. Treatment is based on the size and location of the tumor, visual acuity in the affected eye and in the contralateral eye, patient’s general condition but also patient’s preferences. Therapy also depends on the therapeutic armamentarium. Iodine-125 brachytherapy is an attractive and more widely accepted technique for treating small anterior choroidal melanoma, despite the risk of local complications.

Towards temperature controlled retinal laser treatment with a single laser at 10 kHz repetition rate

Abstract Laser photocoagulation is one of the most frequently used treatment approaches in ophthalmology for a variety of retinal diseases. Depending on indication, treatment intensity varies from application of specific micro injuries down to gentle temperature increases without inducing cell damage. Especially for the latter, proper energy dosing is still a challenging issue, which mostly relies on the physician’s experience. Pulsed laser photoacoustic temperature measurement has already proven its ability for automated irradiation control during laser treatment but suffers from a comparatively high instrumental effort due to combination with a conventional continuous wave treatment laser. In this paper, a simplified setup with a single pulsed laser at 10 kHz repetition rate is presented. The setup combines the instrumentation for treatment as well as temperature measurement and control in a single device. In order to compare the solely pulsed heating with continuous wave (cw) tissue heating, pulse energies of 4 µJ were applied with a repetition rate of 1 kHz to probe the temperature rise, respectively. With the same average laser power of 60 mW an almost identical temporal temperature course was retrieved in both irradiation modes as expected. The ability to reach and maintain a chosen aim temperature of 41 °C is demonstrated by means of model predictive control (MPC) and extended Kalman filtering at a the measurement rate of 250 Hz with an accuracy of less than ±0.1 °C. A major advantage of optimization-based control techniques like MPC is their capability of rigorously ensuring constraints, e.g., temperature limits, and thus, realizing a more reliable and secure temperature control during retinal laser irradiation.

Situational analysis of diabetic retinopathy treatment Services in Ghana

BackgroundAlthough the equitable distribution of diabetic retinopathy (DR) services across Ghana remains paramount, there is currently a poor understanding of nationwide DR treatment services. This study aims to conduct a situation analysis of DR treatment services in Ghana and provide evidence on the breadth, coverage, workload, and gaps in service delivery for DR treatment.MethodsA cross-sectional study was designed to identify health facilities which treat DR in Ghana from June 2018 to August 2018. Data were obtained from the facilities using a semi-structured questionnaire which included questions identifying human resources involved in DR treatment, location of health facilities with laser, vitreoretinal surgery and Anti–vascular endothelial growth factor therapy (Anti-VEGF) for DR treatment, service utilisation and workload at these facilities, and the average price of DR treatment in these facilities.ResultsFourteen facilities offer DR treatment in Ghana; four in the public sector, seven in the private sector and three in the Christian Health Association of Ghana (CHAG) centres. There was a huge disparity in the distribution of facilities offering DR services, the eye care cadre, workload, and DR treatment service (retinal laser, Anti-VEGF, and vitreoretinal surgery). The retinal laser treatment price was independent of all variables (facility type, settings, regions, and National Health Insurance Scheme coverage). However, settings (p = 0.028) and geographical regions (p = 0.010) were significantly associated with anti-VEGF treatment price per eye.ConclusionOur results suggest a disproportionate distribution of DR services in Ghana. Hence, there should be a strategic development and implementation of an eye care plan to ensure the widespread provision of DR services to the disadvantaged population as we aim towards a disadvantaged population as we aim towards a universal health coverage.

Remnant cholesterol predicts progression of diabetic nephropathy and retinopathy in type 1 diabetes.

We aimed to assess whether remnant cholesterol concentration and variability predict the progression of diabetic nephropathy (DN) and severe diabetic retinopathy (SDR) in type 1 diabetes. This observational prospective study covered 5150 FinnDiane Study participants. Remnant cholesterol was calculated as total cholesterol - LDL cholesterol - HDL cholesterol and variability as the coefficient of variation. DN category was based on consensus albuminuria reference limits and the progression status was confirmed from medical files. SDR was defined as retinal laser treatment. For 1338 individuals, the severity of diabetic retinopathy (DR) was graded using the ETDRS classification protocol. Median (IQR) follow-up time was 8.0 (4.9-13.7) years for DN and 14.3 (10.4-16.3) for SDR. Remnant cholesterol (mmolL-1 ) was higher with increasing baseline DN category (P<0.001). A difference was also seen comparing non-progressors (0.41 [0.32-0.55]) with progressors (0.55 [0.40-0.85]), P<0.001. In a Cox regression analysis, remnant cholesterol predicted DN progression, independently of diabetes duration, sex, HbA1c , systolic blood pressure, smoking, BMI, estimated glucose disposal rate and estimated glomerular filtration rate (HR: 1.51 [1.27-1.79]). Remnant cholesterol was also higher in those who developed SDR (0.47 [0.36-0.66]) than those who did not (0.40 [0.32-0.53]), P<0.001, and the concentration increased stepwise with increasing DR severity (P<0.001). Regarding SDR, the HR for remnant cholesterol was 1.52 (1.26-1.83) with the most stringent adjustment. However, remnant cholesterol variability was not independently associated with the outcomes. Remnant cholesterol concentration, but not variability, predicts DN progression and development of SDR. However, it remains to be elucidated whether the associations are causal or not.

Visual outcomes and complications following one-way air-fluid exchange technique for vitreous hemorrhage post vitrectomy in proliferative diabetic retinopathy patients

BackgroundTo evaluate the efficacy and outcomes of one-way surgical technique for the treatment of vitreous hemorrhage post vitrectomy on proliferative diabetic retinopathy (PDR) patients.MethodsThis retrospective case series include 47 PDR patients who had vitrectomy with balanced saline solution tamponade and have developed vitreous hemorrhage without significant absorption. The one-way air-fluid exchange procedure which involves the application of a 0.22-μm pore size filter to exchange about 4.5–5.5 ml of fluid with a 10 ml syringe was performed on 47 patients (47 eyes). Post procedure, additional treatments were administered when needed. Best corrected visual acuity (BCVA), occurrence of intra-procedural and post-procedural complications were recorded and analyzed.ResultsA total of 47 eyes of 47 PDR patients with a mean age of 50.8 ± 12.0 years were reviewed. Because of vitreous hemorrhage or tractional retinal detachment of PDR, all 47 eyes underwent vitrectomy with balanced saline solution tamponade prior to the exchange procedure. Four patients (8.51%) and 43 patients (91.5%) were diagnosed with type 1 diabetes mellitus (T1DM), or type 2 diabetes mellitus (T2DM), respectively. All 47 eyes were given the one-way air-fluid exchange procedure in the treatment room. Forty-two cases (89.4%) needed the air-fluid exchange procedure only once, 4 cases (8.51%) underwent the procedure twice, and 1 case (2.13%) was given the procedure three times, followed by additional retinal photocoagulation and one intravitreal injection of Conbercept. In addition to the procedure, no further treatment was needed for 5 eyes (10.6%) while additional retinal laser treatment was provided for 41 eyes (87.2%). The BCVA at the final follow-up was significantly improved from the initial acuity baseline in all cases. No complications were observed during the follow-ups.ConclusionThis one-way air-fluid exchange procedure can effectively exchange the vitreous hemorrhage and improve visual acuity of PDR patients who develop vitreous rehemorrhage post vitrectomy without obvious complications.

State and parameter estimation for model-based retinal laser treatment

Abstract We present an approach for state and parameter estimation in retinal laser treatment by a novel setup where both measurement and heating is performed by a single laser. In this medical application, the temperature that is induced by the laser in the patient’s eye is critical for a successful and safe treatment. To this end, we pursue a model-based approach using a model given by a heat diffusion equation on a cylindrical domain, where the source term is given by the absorbed laser power. The model is parametric in the sense that it involves an absorption coefficient, which depends on the treatment spot and plays a central role in the input-output behavior of the system. After discretization, we apply a particularly suited parametric model order reduction to ensure real-time tractability while retaining parameter dependence. We augment known state estimation techniques, i.e., extended Kalman filtering and moving horizon estimation, with parameter estimation to estimate the absorption coefficient and the current state of the system. Eventually, we show first results for simulated and experimental data from porcine eyes. We find that, regarding convergence speed, the moving horizon estimation slightly outperforms the extended Kalman filter on measurement data in terms of parameter and state estimation, however, on simulated data the results are very similar.