Ocular oxygenation and the treatment of diabetic retinopathy

Morphology, Fundus Autofluorescence, and Retinal Sensitivity of Photocoagulated Lesions in Proliferative Diabetic Retinopathy

Purpose

To evaluate the relationships among morphology, fundus autofluorescence (FAF), and retinal sensitivity of photocoagulated lesions more than 1 year after panretinal photocoagulation in patients with proliferative diabetic retinopathy and good vision.

Methods

This retrospective cohort study included patients with proliferative diabetic retinopathy who had undergone panretinal photocoagulation more than 1 year ago. The photocoagulated lesions were classified according to FAF levels: group A, no FAF; group B, diffuse FAF; group C, white-dotted centers with diffuse FAF; group D, white-dotted centers without FAF; and group E, controls. The main outcome measures were FAF, retinal sensitivity, and morphology of the photocoagulated lesions.

Results

The median sensitivity values and number of photocoagulated lesions in groups A (n = 37), B (n = 39), C (n = 4), D (n = 15), and E (n = 39) were 0 dB, 18.0 dB, 13.9 dB, 0.3 dB, and 21.5 dB, respectively. EZ lines were absent in 93.5%, 18.1%, 50%, 93.3%, and 0% of lesions in groups A, B, C, D, and E, respectively. The inner retinal layer was damaged in 45.2%, 3.0%, 50%, 73.3%, and 0% lesions in groups A, B, C, D, and E, respectively. Statistically significant between-group differences were observed in the retinal sensitivities of the photocoagulated lesions, presence of EZ lines, and damage to the inner retinal layer (p < 0.05).

Conclusions

The photoreceptors in most photocoagulated lesions with diffuse FAF retain their morphology and function.

Translational Relevance

Using fundus autofluorescence, the damage to photoreceptors after panretinal photocoagulation in patients with diabetes can be estimated in a noninvasive manner. This process can help in determining the need for additional panretinal photocoagulation.

Optical coherence tomography in the management of diabetic macular oedema

Diabetic macular oedema (DMO) is the major cause of visual impairment in people with diabetes. Optical coherence tomography (OCT) is now the most widely used modality to assess presence and severity of DMO. DMO is currently broadly classified based on the involvement to the central 1 mm of the macula into non-centre or centre involved DMO (CI-DMO) and DMO can occur with or without visual acuity (VA) loss. This classification forms the basis of management strategies of DMO. Despite years of research on quantitative and qualitative DMO related features assessed by OCT, these do not fully inform physicians of the prognosis and severity of DMO relative to visual function. Having said that, recent research on novel OCT biomarkers development and re-defined classification of DMO show better correlation with visual function and treatment response. This review summarises the current evidence of the association of OCT biomarkers in DMO management and its potential clinical importance in predicting VA and anatomical treatment response. The review also discusses some future directions in this field, such as the use of artificial intelligence to quantify and monitor OCT biomarkers and retinal fluid and identify phenotypes of DMO, and the need for standardisation and classification of OCT biomarkers to use in future clinical trials and clinical practice settings as prognostic markers and secondary treatment outcome measures in the management of DMO.

Microinvasive pars plana vitrectomy combined with internal limiting membrane peeling versus anti-VEGF intravitreal injection for treatment-naïve diabetic macular edema (VVV-DME study): study protocol for a randomized controlled trial

BACKGROUND

Diabetic macular edema (DME) is the main cause of vision loss in diabetic patients. Currently, anti-vascular endothelial growth factor (VEGF) intravitreal injection stands as the first-line therapy for DME. However, some patients exhibit insufficient response to anti-VEGF agents and often require multiple injections, imposing psychological and economic burdens. While microinvasive pars plana vitrectomy (PPV) has been shown to be safe and effective in treating refractory DME, scant research has explored its application to treatment-naïve DME. The purpose of this study is to determine whether early PPV combined with internal limiting membrane (ILM) peeling can lessen the therapeutic burden of DME patients, prevent vision loss, and maintain long-term stabilization of diabetic retinopathy.

METHODS

This is a single-center, prospective, parallel-group, non-inferiority randomized controlled trial involving 102 DME participants. Participants will be randomly assigned to either the study group (PPV combined with ILM peeling) or the control group (conbercept intravitreal injection (IVC)) at a 1:1 ratio, with a scheduled follow-up at 12 months post-operation. Comparative analysis of results between the two groups will be conducted at months 1, 3, 6, and 12 after the intervention. The primary outcomes involve evaluating the changes in central subfield thickness (CST) and best corrected visual acuity (BCVA). The secondary outcomes include assessment of optical coherence tomography (OCT) and OCT angiography (OCTA) biomarkers, re-treatment and adverse events rates, diabetic retinopathy (DR) development, cost-effectiveness analysis, and vision-related quality of life (VRQL).

DISCUSSION

Some patients do not respond well to anti-VEGF drugs and repeated intravitreal injections increase the treatment burden for patients. The VVV study aims to explore whether PPV combined with ILM peeling could become an initial treatment option for treatment-naïve DME patients.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05728476. Registered on 15 February 2023.

Quantitative Evaluation of Fundus Autofluorescence in Laser Photocoagulation Scars for Diabetic Retinopathy: Conventional vs. Short-Pulse Laser

Short-pulse laser is popular for its advantages like less pain. However, its effectiveness is still debated. The aim of this study was to compare fundus autofluorescence (FAF) luminosity changes of laser photocoagulation scars between the conventional laser (0.2 s) and the short-pulse laser (0.02 s) for diabetic retinopathy. Conventional and short-pulse laser photocoagulations were performed in six and seven eyes, respectively. FAF images were captured at 1, 3, 6, 12, and 18 months after the treatments. To evaluate FAF, individual gray-scale values of the laser scars adjacent to the retinal arcade vessels were recorded; then, the mean gray values of the scars were divided by the luminosity of arcade vein. The average luminosity ratio of laser scars at 1, 3, 6, 12, and 18 months were 1.51 ± 0.17, 1.26 ± 0.07, 1.21 ± 0.03, 0.95 ± 0.11, and 0.89 ± 0.05 with conventional laser and 1.91 ± 0.13, 1.50 ± 0.15, 1.26 ± 0.08, 1.18 ± 0.06, and 0.97 ± 0.04 with short-pulse laser, respectively. Findings suggest the short-pulse laser displayed delayed hypoautofluorescence progression. This implies potential postponement in post-irradiation atrophic changes, as well as metabolic amelioration delay in the ischemic retina, when compared to conventional laser treatment.

Imaging ocular water inflow in the mouse with deuterium oxide MRI

Abnormal intraocular fluid flow or clearance is involved with a variety of eye diseases such as glaucoma and diabetic retinopathy, but measurement of water exchange dynamics in the vitreous and aqueous remain challenging. 2H MRI can be used to image deuterium oxide (D₂O) as a tracer, but the signal-to-noise ratio for deuterium is low due to its low concentration, which has hampered its application to imaging the eye. To overcome this challenge, we investigated the feasibility of direct D2O MRI to measure water dynamics in the mouse eye. The balanced steady-state free precession (bSSFP) sequence provided substantially higher signal-to-noise ratio for imaging D2O in fluid compared to standard gradient echo and spin echo sequences. bSSFP allowed dynamic imaging of intraocular water inflow in the mouse with 41 s temporal resolution. The inflow rate in the vitreous was found to be faster than in the aqueous. These studies demonstrate the feasibility of in vivo imaging of water inflow dynamics into the both the vitreous and aqueous in mice, which could be useful in studies of abnormal fluid exchange in rodent models of eye disease.

Retinal Photoreceptors and Microvascular Changes in the Assessment of Diabetic Retinopathy Progression: A Two-Year Follow-Up Study

BACKGROUND

With the increasing global incidence of diabetes mellitus (DM), diabetic retinopathy (DR) has become one of the leading causes of blindness in developed countries. DR leads to changes in retinal neurons and microcirculation. Rtx1TM (Imagine Eyes, Orsay, France) is a retinal camera that allows histological visualisations of cones and retinal microcirculation throughout the DM duration.

OBJECTIVE

This study aimed to analyse the cones and retinal microvascular changes in 50 diabetic individuals and 18 healthy volunteers. The patients participated in the initial visit and two follow-up appointments, one and two years after the study, beginning with Rtx1TM image acquisition, visual acuity assessment, macular OCT scans and blood measurements.

RESULTS

The study revealed significant differences in the cone density, mosaic arrangement and vascular morphology between healthy and diabetic patients. The final measurements showed decreased photoreceptor and microvascular parameters in the DR group compared with the control group. Furthermore, in the 2-year follow-up, both groups' Rtx1TM-acquired morphological changes were statistically significant.

CONCLUSIONS

Rtx1TM technology was successfully used as a non-invasive method of photoreceptors and retinal vasculature assessment over time in patients with diabetic retinopathy. The study revealed a trend toward more vascular morphological changes occurring over time in diabetic patients.

Relationship between Diabetic Nephropathy and Development of Diabetic Macular Edema in Addition to Diabetic Retinopathy

This study aimed to examine the relationship between diabetic retinopathy (DR) and systemic factors. We evaluated 261 patients (143 men, 118 women, aged 70.1 ± 10.1 years) with type 2 diabetes. All participants underwent a fundus examination, fundus photography using spectral domain optical coherence tomography (SD-OCT), and blood tests. For glycated hemoglobin (HbA1c) levels, the average and highest values in the past were used. We observed DR in 127 (70 men and 57 women) of 261 patients. Logistic regression analyses revealed a significant correlation between DR development and the duration of diabetes (OR = 2.40; 95% CI: 1.50), average HbA1c level (OR = 5.57; 95% CI: 1.27, 24.4), highest HbA1c level (OR = 2.46; 95% CI: 1.12, 5.38), and grade of diabetic nephropathy (DN) (OR = 6.23; 95% CI: 2.70, 14.4). Regression analyses revealed a significant correlation between the severity of DR and duration of diabetes (t = -6.66; 95% CI: 0.21, 0.39), average HbA1c level (t = 2.59; 95% CI: 0.14, 1.02), and severity of DN (t = 6.10; 95% CI: 0.49, 0.97). Logistic regression analyses revealed a significant correlation between diabetic macular edema (DME) development and DN grade (OR = 2.22; 95% CI: 1.33, 3.69). DN grade correlates with the development of DR and DME, and decreased renal function predicts the onset of DR.

Role of Vitrectomy in Nontractional Refractory Diabetic Macular Edema

Background: Currently, the gold standard of diabetic macular edema (DME) treatment is anti-vascular endothelial growth factor (VEGF) injections, although a percentage of patients do not respond optimally. Vitrectomy with or without internal limiting membrane (ILM) peeling is a well-established treatment for DME cases with a tractional component while its role for nontractional cases is unclear.The aim of this study is to evaluate the role of vitrectomy with or without ILM peeling in nontractional refractory DME.Methods: We performed a retrospective review of twenty-eight eyes with nontractional refractory DME treated with vitrectomy at San Giuseppe Hospital, Milan, between 2016 and 2018. All surgeries were performed by a single experienced vitreoretinal surgeon. In 43.4% of cases, the ILM was peeled. Best corrected visual acuity and optical coherence tomography (OCT) scans were assessed preoperatively and at 6, 12, and 24 months post-vitrectomy. Results: The mean central macular thickness improved from 413.1 ± 84.4 to 291.3 ± 57.6 μm at two years (p < 0.0001). The mean logarithm of the minimum angle of resolution logMAR best-corrected visual acuity (BCVA) improved after two years, from 0.6 ± 0.2 to 0.2 ± 0.1 (p < 0.0001). We found no difference between ILM peeling vs. no ILM peeling group in terms of anatomical (p = 0.8) and visual outcome (p = 0.3). Eyes with DME and subfoveal serous retinal detachment (SRD) at baseline had better visual outcomes at the final visit (p = 0.001). Conclusions:We demonstrated anatomical and visual improvement of patients who underwent vitrectomy for nontractional refractory DME with and without ILM peeling. Improvement was greater in patients presenting subretinal fluid preoperatively.

Vitrectomy with ILM peeling in diabetic macular edema in one eye vs. intravitreal anti-VEGF injections in the second eye: a comparative study

PURPOSE

The aim of this study was to compare the results of vitrectomy performed in patients' worse eyes with diabetic macular edema to the results of continuous anti-VEGF treatment performed in patients' fellow eyes.

METHODS

A retrospective interventional study of 14 patients with diabetic macular edema in both eyes. The better eye was always qualified for aflibercept injections (group 1), and the worse eye was scheduled for vitrectomy (group 2). The follow-up lasted 12 months. The following parameters were measured: visual acuity (V), central retinal thickness (CRT), maximum retinal thickness (MRT), central choroidal thickness (CCT), superficial fovea avascular zone (sFAZ) and deep fovea avascular zone (dFAZ), and vessel density at the level of superficial (sVD) and deep (dVD) retinal vessels.

RESULTS

None of the analyzed factors differed between groups with statistical significance at any timepoint. The time of recovery of vision was identical in both eyes (F = 0.91, p = 0.449). The final sFAZ was significantly smaller for group 2 (median 196 μm) than for group 1 (median 375 μm; U = 101.0; p = 0.022; r = 0.44).

CONCLUSION

Both techniques resulted in similar improvements in visual acuity and decreases in CRT after 1 year. sFAZ decreased in all eyes, with a higher extent after vitrectomy.

Effect of panretinal photocoagulation on retina and choroid in diabetic retinopathy: An optical coherence tomography angiography study

BACKGROUND

To analyze the quantitative changes in both macular, and choroidal thickness, and microvascularization after panretinal photocoagulation (PRP) in eyes with proliferative diabetic retinopathy (PDR) or severe non-proliferative diabetic retinopathy (NPDR) by using optical coherence tomography angiography (OCT-A).

METHODS

The patients diagnosed with severe NPDR or PDR according to the Early Treatment Diabetic Retinopathy Study (ETDRS) and decided to be treated with PRP were included in this prospective and observational study. Ten eyes of 10 patients with PDR and twelve eyes of 12 patients with severe NPDR were examined. Macular scans (6 × 6 mm) were obtained from OCT-A at baseline and at month 6 after PRP. Subfoveal choroidal thickness (SFCT) measurements that were obtained through the foveolar center on a high-definition line scan were recorded.

RESULTS

Best-corrected visual acuity (BCVA) significantly decreased (p = 0.018), central foveal thickness and mean parafoveal thickness significantly increased (p < 0001 and p < 0.001, respectively) six months after PRP. The thickness of all parafoveal retinal quadrants (temporal, superior, nasal, inferior) increased (p = 0.001, p = 0.003, p < 0.001, p < 0.001, respectively) and mean parafoveal, parafoveal temporal, and parafoveal nasal vessel density of the deep capillary plexus (DCP) significantly decreased six months after PRP compared with the baseline values (p = 0.023, p = 0.041, p = 0.018, respectively).

CONCLUSIONS

The parafoveal vessel density of DCP decreased significantly 6 months after PRP in eyes with PDR or severe NPDR. While the difference in SFCT and choroidal flow density was not significant from the baseline; central and parafoveal retinal thickness increased and BCVA decreased significantly 6 months after PRP treatment.

Hospital-Based Study of Risk Factors Associated with Development of Myopic Macular Neovascularization in Highly Myopic Eyes

INTRODUCTION

Myopic macular neovascularization (MNV) is the most common cause of a reduction of central vision in eyes with pathologic myopia, and it can progress to macular atrophy in the long term. The aim of this study was to determine the risk factors associated with the development of MNVs.

METHODS

There were 17,198 follow-up records from 5,409 eyes of 2,784 highly myopic patients that were reviewed. The general information and ophthalmic information in the records were studied. The significance of the correlations of factors associated with the development and predicting the development of myopic MNV were determined.

RESULTS

Being a woman (odds ratio [OR] = 0.727, p < 0.001), having a longer axial length (OR = 0.948, p < 0.001), having a poorer baseline best-correct visual acuity (BCVA, OR = 2.098, p < 0.001), having severe myopic maculopathy (overall: p < 0.001), prior myopic MNV in the fellow eye (OR = 4.105, p < 0.001), presence of patchy atrophy (overall p < 0.001), lacquer cracks (OR = 1.718, p < 0.001), prior foveal retinal detachment (RD, OR = 3.269, p < 0.001), prior macular hole (MH, OR = 0.641, p < 0.001), prior macular retinoschisis (OR = 1.533, p < 0.001), and prior macular edema (OR = 1.508, p < 0.001) were significantly correlated with the development of myopic MNV. Eyes with MNV and patchy atrophy would require an intensive follow-up examination for myopic patients as the fellow eye would have a risk of >70% for the development of myopic MNV in 3 years and nearly 80% in 5 years.

CONCLUSIONS

Clinicians need to pay special attention to eyes with severe grades of myopic maculopathy, prior myopic MNV in the fellow eye, presence of patchy atrophy, and prior foveal retinal detachment to determine the onset of myopic MNV.

Diabetic retinopathy screening in the emerging era of artificial intelligence

Diabetic retinopathy is a frequent complication in diabetes and a leading cause of visual impairment. Regular eye screening is imperative to detect sight-threatening stages of diabetic retinopathy such as proliferative diabetic retinopathy and diabetic macular oedema in order to treat these before irreversible visual loss occurs. Screening is cost-effective and has been implemented in various countries in Europe and elsewhere. Along with optimised diabetes care, this has substantially reduced the risk of visual loss. Nevertheless, the growing number of patients with diabetes poses an increasing burden on healthcare systems and automated solutions are needed to alleviate the task of screening and improve diagnostic accuracy. Deep learning by convolutional neural networks is an optimised branch of artificial intelligence that is particularly well suited to automated image analysis. Pivotal studies have demonstrated high sensitivity and specificity for classifying advanced stages of diabetic retinopathy and identifying diabetic macular oedema in optical coherence tomography scans. Based on this, different algorithms have obtained regulatory approval for clinical use and have recently been implemented to some extent in a few countries. Handheld mobile devices are another promising option for self-monitoring, but so far they have not demonstrated comparable image quality to that of fundus photography using non-portable retinal cameras, which is the gold standard for diabetic retinopathy screening. Such technology has the potential to be integrated in telemedicine-based screening programmes, enabling self-captured retinal images to be transferred virtually to reading centres for analysis and planning of further steps. While emerging technologies have shown a lot of promise, clinical implementation has been sparse. Legal obstacles and difficulties in software integration may partly explain this, but it may also indicate that existing algorithms may not necessarily integrate well with national screening initiatives, which often differ substantially between countries.

Diabetic macular ischaemia- a new therapeutic target?

Diabetic macular ischaemia (DMI) is traditionally defined and graded based on the angiographic evidence of an enlarged and irregular foveal avascular zone. However, these anatomical changes are not surrogate markers for visual impairment. We postulate that there are vascular phenotypes of DMI based on the relative perfusion deficits of various retinal capillary plexuses and choriocapillaris. This review highlights several mechanistic pathways, including the role of hypoxia and the complex relation between neurons, glia, and microvasculature. The current animal models are reviewed, with shortcomings noted. Therefore, utilising the advancing technology of optical coherence tomography angiography (OCTA) to identify the reversible DMI phenotypes may be the key to successful therapeutic interventions for DMI. However, there is a need to standardise the nomenclature of OCTA perfusion status. Visual acuity is not an ideal endpoint for DMI clinical trials. New trial endpoints that represent disease progression need to be developed before irreversible vision loss in patients with DMI. Natural history studies are required to determine the course of each vascular and neuronal parameter to define the DMI phenotypes. These DMI phenotypes may also partly explain the development and recurrence of diabetic macular oedema. It is also currently unclear where and how DMI fits into the diabetic retinopathy severity scales, further highlighting the need to better define the progression of diabetic retinopathy and DMI based on both multimodal imaging and visual function. Finally, we discuss a complete set of proposed therapeutic pathways for DMI, including cell-based therapies that may provide restorative potential.

Axial myopia, a protective factor for diabetic retinopathy-role of vascular endothelial growth factor

Long axial length is one of the ocular protective factors in development of diabetic retinopathy (DR). In this study we examined the effect of axial length (AL) on aqueous humor vascular endothelial growth factor (VEGF) levels in patients with diabetes mellitus with or without DR. Forty-eight eyes of 48 participants were divided into three groups of 16 each. Group A consisted of non-diabetic patients, Group B had diabetic patients without DR, and Group C had diabetic patients with treatment-naive non-proliferative DR (NPDR). The groups were further subdivided based on axial lengths i.e., AL ≤ 23.30 mm (A1, B1, C1) and AL > 23.30 mm (A2, B2, C2). Undiluted aqueous humor was obtained during cataract surgery to measure the VEGF levels. We observed significant decrease in VEGF concentration in patients with AL ≥ 23.30 mm as compared with AL ≤ 23.30 mm in non-diabetic as well as diabetic patients. As the eye elongates, there is less secretion of VEGF in non-diabetics as well in diabetics with or without DR. Our findings strengthened the concept that an increase in AL leads to less VEGF in diabetic eyes, thus leading to less severe DR changes.

Retinal vascular oxygen saturation in response to a less extensive laser treatment in proliferative diabetic retinopathy

PURPOSE

The purpose of this study was to evaluate the association between retinal laser burden and vascular oxygen saturation in patients with proliferative diabetic retinopathy (PDR) treated with different extent of retinal laser.

METHODS

The study was a prospective, interventional study of patients with treatment-naïve PDR. Patients were treated with navigated retinal laser (Navilas^® , OD-OS GmbH, Teltow, Germany) in different doses. Retinal oximetry was obtained at baseline (BL) prior to laser and after 6 months (M6). Patients were divided into three groups according to total laser spots applied: <1500 spots (Group 1), 1500-2000 spots (Group 2), and >2000 spots (Group 3).

RESULTS

We included 33 eyes of 28 patients with treatment-naïve PDR. The groups did not differ according in BL characteristics. Between BL and M6, retinal arteriolar oxygen saturation did not change but retinal venular oxygen saturation (median with interquartile range) decreased in Groups 1 and 2 (1: 65.5 ± 8.8% versus 60.5 ± 9.5%, p = 0.04; 2: 65.3 ± 7.3% versus 63.0 ± 13.5%, p = 0.04). Focal retinal venular oxygen saturation, located to quadrants with retinal neovascularization, decreased in Group 2 from BL to M6 (67.5 ± 13.3% versus 61.5 ± 8.8%, p = 0.04). Retinal venular diameter decreased from BL to M6 in Group 1 (174.5 ± 15.3 μm versus 165.1 ± 28.7 μm, p = 0.01).

CONCLUSIONS

In this study of patients with treatment-naïve PDR, we showed that a less extensive laser treatment caused a reduction in retinal venular oxygen saturation and diameter 6 months after treatment. Our results suggest that less extensive laser treatment may be sufficient to improve the retinal metabolic environment conducive to PDR regression.

Calculation of intraocular lens power and to determine the relationship between ocular biometry and severity of diabetic retinopathy in patients with type II diabetes mellitus

Purpose:

To calculate the intraocular lens power and to determine the relationship between ocular biometry and severity of diabetic retinopathy (DR) in patients with type II diabetes mellitus.

Methods:

The study group included 150 type II diabetic subjects with DR. The control group consisted of 150 type II diabetic subjects having no DR. Axial length (AL), corneal power, and anterior chamber depth were measured using LenStar. DR and diabetic macular edema were classified according to International DR Classification. Crystalline lens power was calculated using Barrett Universal II formula. AL to corneal radius ratio was calculated. Chi-square test was used for categorical variables.

Results:

In multivariate logistic models adjusting for age, sex, glycosylated hemoglobin, duration of diabetes, Mean age of patients in the study group was 62.45 ± 4.85 years, whereas in the control group, it was 63.37 ± 7.29 years. Of the eyes with DR, 117, 76, 69, and 38 had mild NPDR, moderate NPDR, severe NPDR, and PDR, respectively. The difference in the mean duration of diabetes mellitus and glycosylated hemoglobin in both study and control groups was found to be statistically significant. A progressive decrease in the mean AL and the anterior chamber depth was observed with increasing severity of DR, and difference was statistically significant. There was a progressive increase in intraocular lens power with increasing severity of DR, and difference was found to be statistically significant.

Conclusion:

In persons with diabetes mellitus, globe elongation plays quite an important role in protective effects against DR, with contribution from intraocular lens power and other refractive components.

INVOLUTION OF NEOVASCULAR AGE-RELATED MACULAR DEGENERATION AFTER ENDOPHTHALMITIS

PURPOSE

To report patients who demonstrated an alteration in the clinical and optical coherence tomography features of neovascular age-related macular degeneration after resolution of endophthalmitis.

METHODS

Retrospective case series of the subsequent changes in the macula and need for anti-vascular endothelial growth factor therapy in patients with neovascular age-related macular degeneration who developed endophthalmitis after intravitreal injection.

RESULTS

The study included seven eyes of seven patients with follow-up ranging between 3 months and 11 years. The vitreous cultures (n = 7) before intravitreal antibiotic injection were the following: culture-negative (4) and coagulase-negative Staphylococcus (3). Initial treatment included vitreous tap and injection (4) and pars plana vitrectomy (3). In 5/7 eyes, the optical coherence tomography showed resolution of subretinal fluid and serous pigment epithelial detachment, and there was no additional anti-vascular endothelial growth factor treatment administered.

CONCLUSION

After successful treatment of endophthalmitis in patients with neovascular age-related macular degeneration, there was relative involution of the maculopathy and reduced anti-vascular endothelial growth factor treatment burden in this series.

Association of changes of retinal vessels diameter with ocular blood flow in eyes with diabetic retinopathy

We investigated morphological changes of retinal arteries to determine their association with the blood flow and systemic variables in type 2 diabetes patients. The patients included 47 non-diabetic retinopathy eyes, 36 mild or moderate nonproliferative diabetic retinopathy (M-NPDR) eyes, 22 severe NPDR (S-NPDR) eyes, 32 PDR eyes, and 24 normal eyes as controls. The mean wall to lumen ratio (WLR) measured by adaptive optics camera was significantly higher in the PDR groups than in all of the other groups (all P < 0.001). However, the external diameter of the retinal vessels was not significantly different among the groups. The mean blur rate (MBR)-vessel determined by laser speckle flowgraphy was significantly lower in the PDR group than in the other groups (P < 0.001). The WLR was correlated with MBR-vessel (r = − 0.337, P < 0.001), duration of disease (r = 0.191, P = 0.042), stage of DM (r = 0.643, P < 0.001), systolic blood pressure (r = 0.166, P < 0.037), and presence of systemic hypertension (r = 0.443, P < 0.001). Multiple regression analysis demonstrated that MBR-vessel (β = − 0.389, P < 0.001), presence of systemic hypertension (β = 0.334, P = 0.001), and LDL (β = 0.199, P = 0.045) were independent factors significantly associated with the WLR. The increased retinal vessel wall thickness led to a narrowing of lumen diameter and a decrease in the blood flow in the PDR group.

Evaluation of Macular Changes in the Long Term after Pars Plana Vitrectomy with Internal Limiting Membrane Peeling for Diabetic Macular Edema

AIM

To evaluate long-term macular changes following pars plana vitrectomy (PPV) with internal limiting membrane (ILM) peeling for diabetic macular edema (DME).

METHODS

Forty eligible eyes of 37 patients were included in this retrospective study. Best corrected visual acuity (BCVA), central macular thickness (CMT), and 5-mm macular volume (5-MV) were examined preoperatively, postoperatively after 1, 2, 3, 6, 12, and 24 months, and at a final visit. Response to surgical treatment was considered as recurrence, reincrease, or recovery of DME based on macular changes.

RESULTS

Mean follow-up time was 51.1 ± 19.0 months after surgery. Recurrence (n = 5) and reincrease (n = 17) of DME was observed in 22 eyes (55%) and additional treatments were applied. Recovery of DME was observed in 18 eyes (45%). Preoperative and final-visit mean BCVA (logMAR) was 1.08 ± 0.37 and 0.93 ± 0.45, respectively (p = 0.02). Preoperative and final-visit mean CMT was 514.74 ± 155.65 and 281.87 ± 112.58 µm, respectively (p < 0.001). The 5-MV significantly decreased following surgery (from 8.18 ± 1.57 to 6.52 ± 1.39 mm3; p < 0.001). DME was present in 12 eyes (30%) at the final visit.

CONCLUSION

Although PPV with ILM peeling had efficacy in DME management, this effect tended to decrease over time, such that a considerable number of patients required additional treatment.

Pathogenic role of human C-reactive protein in diabetic retinopathy

PURPOSE

Elevated blood levels of C-reactive protein (CRP) are associated with both type 1 and type 2 diabetes and diabetic complications, such as diabetic retinopathy (DR). However, its pathogenic role in DR remains unknown. The present study aims to investigate the potential role of CRP in DR pathogenesis and explore its underlying mechanism.

MATERIALS AND METHODS

Human CRP transgenic (hCRP-Tg) rats were employed for streptozotocin (STZ)-induced diabetic and oxygen-induced retinopathy (OIR) models. The retina function was monitored by electroretinography (ERG) and retinal thickness was measured by optical coherence tomography (OCT). TUNEL and cell death ELISA were performed to measure the apoptosis. Oxidative stress was detected by the measurement of reactive oxygen species (ROS) in cells and 3-Nitrotyrosine staining in tissue sections.

RESULTS

In non-diabetic condition, hCRP-Tg with elevated hCRP levels in the retinas demonstrated declined ERG responses and decreased retinal thickness. In STZ-induced diabetic condition, overexpression of hCRP deteriorated retinal neurodegeneration as shown by ERG and apoptosis assays. hCRP also exacerbated retinal leukostasis and acellular capillary formation induced by diabetes. In the OIR model, overexpression of hCRP exacerbated retinal neovascularization (NV). In retinal cell lines, hCRP treatment induced cell death and over-production of ROS. Furthermore, hCRP-induced overexpression of pro-inflammatory, pro-oxidative, and pro-angiogenic factors was associated with up-regulation of CD32 and the NF-κB signaling in the retinas.

CONCLUSIONS

Elevated hCRP levels play a pathogenic role in DR. Targeting the hCRP-CD32-NF-κB pathway may represent a novel therapeutic strategy for DR.

Transient Increase and Delay of Multifocal Electroretinograms Following Laser Photocoagulations for Diabetic Macular Edema

Background: The acute physiological changes induced by focal retinal photocoagulation (PC) have been largely unexplored. Methods: This was a case-series study. We recorded multifocal electroretinograms (mfERGs) just before PC, and mfERGs were also recorded 5′, 15′, one hour, 24 h, and one week after the PCs. Transient changes of mfERGs were analyzed in eyes which underwent PCs to treat diabetic macular edema. The mfERGs recorded from the predominantly irradiated area and that from non-irradiated areas were analyzed separately. Results: Fifteen eyes of 15 patients were included in this study. The mfERGs elicited from non-irradiated areas did not change after PC, but the mfERGs elicited from the irradiated area changed with time; the amplitude was larger at 60′ than that before (p < 0.05) and at 5′ after PC (p < 0.01) and significantly smaller at 24 h and 1 week than that before and at 60′ after the PC (p < 0.01). The implicit time was significantly prolonged after PC. mfERG on irradiated area with the severe diabetic change was less altered after PCs. Conclusions: The transient increase in the amplitude at 60′ likely resulted from a biological amplification of partially damaged cells adjacent to the PC spots. The mfERGs manifested the dynamic alterations of the retinal function following PCs.

Changes of visual fields in treatment of proliferative diabetic retinopathy: a systematic review

The aim of this systematic review was to compare certain side-effects [visual fields (VF), dark adaptation, colour vision (CV) and contrast sensitivity (CS)] of conventional panretinal photocoagulation (PRP) with those of other treatments in proliferative diabetic retinopathy (PDR). A systematic literature search was conducted on 30 November 2018 in PubMed and Embase. The search comprised the keywords 'proliferative diabetic retinopathy', 'laser', 'treatment' and 'anti-vegf'. We included prospective studies and randomized controlled trials that investigated certain side-effects (VF, dark adaptation, CV, CS) in treatment of PDR (primary outcome). In total, 1867 articles were screened, and 10 studies were included (2176 eyes of 2086 patients examined in the VF studies and 1360 eyes of 1360 patients examined in the CV and CS studies). Visual fields (VF) were investigated in 10 studies, CV in one study and CS in one study. Treatment modalities included conventional PRP, other modalities of laser treatment and vascular endothelial growth factor (VEGF) inhibitors. Four studies demonstrated a worse VF impact of PRP than VEGF inhibitors. Seven studies reported of an overall worsening in VF after laser with no differences between different laser approaches. No differences were found in CV or CS. Overall, we found a trend, confirmed in four large studies, towards VEGF inhibitors causing less harm to VF compared to conventional PRP. Whilst VF was generally depressed after laser, it did not differ between different treatment approaches. Furthermore, it was not possible to make certain conclusions of CV or CS, with only one study in each field.

Inhibitory Action of Antidiabetic Drugs on the Free Radical Production by the Rod Outer Segment Ectopic Aerobic Metabolism

Rod outer segments (OS) express the FoF1-ATP synthase and the respiratory chain, conducting an ectopic aerobic metabolism that produces free radicals in vitro. Diabetic retinopathy, a leading cause of vision loss, is associated with oxidative stress in the outer retina. Since metformin and glibenclamide, two anti-type 2 diabetes drugs, target the respiratory complexes, we studied the effect of these two drugs, individually or in association, on the free radical production in purified bovine rod OS. ATP synthesis, oxygen consumption, and oxidative stress production were assayed by luminometry, oximetry and flow cytometry, respectively. The expression of FoF1-ATP synthase was studied by immunogold electron microscopy. Metformin had a hormetic effect on the OS complex I and ATP synthetic activities, being stimulatory at concentrations below 1 mM, and inhibitory above. Glibenclamide inhibited complexes I and III, as well as ATP production in a concentration-dependent manner. Maximal concentrations of both drugs inhibited the ROI production by the light-exposed OS. Data, consistent with the delaying effect of these drugs on the onset of diabetic retinopathy, suggest that a combination of the two drugs at the beginning of the treatment might reduce the oxidative stress production helping the endogenous antioxidant defences in avoiding retinal damage.

Combined vitrectomy, near-confluent panretinal endolaser, bevacizumab and cyclophotocoagulation for neovascular glaucoma - a retrospective interventional case series

Background: Neovascular glaucoma (NVG) is a severe, potentially blinding disease and a therapeutic challenge. The purpose of this study was to evaluate the safety and efficacy of an integrative surgical approach to neovascular glaucoma. Methods: Retrospective analysis of a one-year follow-up of a consecutive interventional case series of NVG. Eyes underwent transscleral cyclophotocoagulation, pars plana vitrectomy, near-confluent panretinal photocoagulation, and intravitreal bevacizumab. Phakic eyes underwent concomitant cataract surgery. Best-corrected visual acuity (BCVA, logMAR), intraocular pressure (IOP, mmHg), number of glaucoma medication, visual analog pain scale (VAPS, 0-10) were recorded at baseline, and 1, 3, 6, and 12 months. Blind eyes were excluded. Results: Seventy-seven eyes of 77 patients (45 male, 32 female, mean age 73.6±12.2 years) were included. NVG underlying conditions included retinal vein occlusion (41.6%), proliferative diabetic retinopathy (35.1%), central retinal artery occlusion (19.5%), and ocular ischemic syndrome (3.9%). Mean IOP decreased postoperatively from 46.3±10.1 mmHg to 14.5±7.9 mmHg (p<0.001), glaucoma medication from 4.7±1.3 to 1.8±1.8 (p<0.001), and VAPS from 6.0±1.8 to 0. BCVA remained unchanged. Postoperative intraocular inflammation had resolved in all eyes at the one-month follow-up. 71.4% (55/77) eyes did not require additional major interventions during follow-up. Conclusions: A single, comprehensive surgery session lowered IOP significantly, reduced GMS, and controlled pain.

Combined vitrectomy, near-confluent panretinal endolaser, bevacizumab and cyclophotocoagulation for neovascular glaucoma - a retrospective interventional case series

Background: Neovascular glaucoma (NVG) is a severe, potentially blinding disease and a therapeutic challenge. The purpose of this study was to evaluate the safety and efficacy of an integrative surgical approach to neovascular glaucoma. Methods: Retrospective analysis of a one-year follow-up of a consecutive interventional case series of NVG. Eyes underwent transscleral cyclophotocoagulation, pars plana vitrectomy, near-confluent panretinal photocoagulation, and intravitreal bevacizumab. Phakic eyes underwent concomitant cataract surgery. Best-corrected visual acuity (BCVA, logMAR), intraocular pressure (IOP, mmHg), number of glaucoma medication, visual analog pain scale (VAPS, 0-10) were recorded at baseline, and 1, 3, 6, and 12 months. Blind eyes were excluded. Results: Seventy-seven eyes of 77 patients (45 male, 32 female, mean age 73.6±12.2 years) were included. NVG underlying conditions included retinal vein occlusion (41.6%), proliferative diabetic retinopathy (35.1%), central retinal artery occlusion (19.5%), and ocular ischemic syndrome (3.9%). Mean IOP decreased postoperatively from 46.3±10.1 mmHg to 14.5±7.9 mmHg (p<0.001), glaucoma medication from 4.7±1.3 to 1.8±1.8 (p<0.001), and VAPS from 6.0±1.8 to 0. BCVA remained unchanged. Postoperative intraocular inflammation had resolved in all eyes at the one-month follow-up. 71.4% (55/77) eyes did not require additional major interventions during follow-up. Conclusions: A single, comprehensive surgery session lowered IOP significantly, reduced GMS, and controlled pain.

Effect of panretinal photocoagulation on macular vasculature using optical coherence tomography angiography

BACKGROUND

To evaluate the changes of macular vascular density in the superficial capillary (SCP) and the deep capillary plexus (DCP), foveal avascular area (FAZ), choroidal flow, and macular thickness after pan-retinal photocoagulation (PRP).

METHODS

In this prospective interventional non-comparative case series, patients with very severe nonproliferative (NPDR) and early proliferative diabetic retinopathy (PDR) and no significant macular edema who were candidates for pan-retinal photocoagulation underwent measurement of corrected distance visual acuity (CDVA), optical coherence tomography (OCT), Optical coherence tomography angiography (OCTA) at the baseline, 1, and 6 months following completion of PRP treatment.

RESULTS

Thirty-nine eyes from 21 patients with diabetes were enrolled. Superficial and deep capillary plexus densities in the foveal and parafoveal area didn't change significantly 1 and 6 months post-PRP (p > 0.1 in all of them). The FAZ area constricted 6 months following PRP (p = 0.075). Based on the calculated circularity index, the FAZ became significantly more circular after 6 months of follow-up (p = 0.047). Although the choroidal flow area increased after PRP this increase wasn't statically significant neither at 1 month nor at 6 months post-PRP (p = 0.31 and 0.23, respectively).

CONCLUSION

Although OCTA parameters were not significantly affected by PRP at both short-term (1 month) and long-term (6 months) follow-ups, the FAZ area became significantly circular after PRP may be due to redistribution of blood flow in hypoperfused foveal capillary plexus.

Aflibercept and navigated versus conventional laser in diabetic macular oedema: a 12-month randomized clinical trial

PURPOSE

To examine the efficacy of intravitreal aflibercept and navigated laser as compared to intravitreal aflibercept and conventional laser in diabetic macular oedema (DME) treatment.

METHODS

In 12-month randomized clinical trial, 48 eyes of 37 patients with centre-involved DME at Odense University Hospital were randomized 1:1 to receive three monthly injections of aflibercept followed by navigated (group A) or conventional (group B) focal/grid laser. From month four through twelve, patients were examined monthly, and additional injections were given pro re nata (PRN) (central retinal thickness [CRT]>20% from lowest measurement or loss in visual acuity [VA]>5 Early Treatment Diabetic Retinopathy Study [ETDRS] letters compared with baseline). Outcome measures; (1) percentage of eyes that needed additional injections after laser in group A and B, (2) mean number of injections in group A and B, and (3) mean change in VA and CRT in group A and B.

RESULTS

In the PRN phase, 60.5% of patients needed additional injections without differences between groups A and B (58.3 versus 63.2%, p > 0.99). The mean number of injections between baseline and month 12 was 4.4 (4.2 versus 4.6, p = 0.41). From baseline to month 12, VA improved by 8.4 ETDRS letters, and CRT was reduced by 97.4 μm (+9.4 versus +7.1 letters, p = 0.17, and -83.2 versus -115.4 μm, p = 0.21).

CONCLUSION

No difference in need for retreatment was detected between treatment arms of aflibercept and navigated versus conventional laser.

Alterations in retinal arteriolar microvascular structure associate with higher treatment burden in patients with diabetic macular oedema: results from a 12-month prospective clinical trial

PURPOSE

This study was based on data from a 12-month prospective clinical trial and aimed to examine changes in retinal microvascular structure in eyes treated with intravitreal aflibercept in combination with focal/grid laser photocoagulation for diabetic macular oedema (DME).

METHODS

We included 32 treatment naïve eyes of 22 patients with centre involving DME. The treatment algorithm comprised a loading phase of three monthly injections of aflibercept and focal/grid laser photocoagulation [baseline (BL)-month 3 (M3)] followed by a pro re nata (PRN) aflibercept phase until month 12 (M12). Eyes were divided into groups with and without need for PRN treatment after loading. Parameters of retinal microvascular structure were measured in 45° optic disc centred fundus images at BL, M3 and M12 using a semi-automated software (VAMPIRE®, Vessel Assessment and Measurement Platform for Images of the Retina, Universities of Dundee and Edinburgh, UK).

RESULTS

A significant decrease in retinal arteriolar calibre was demonstrated at both M3 (-11.2 μm, p = 0.005) and M12 (-11.5 μm, p = 0.04) as compared to BL in eyes that needed PRN treatment during follow-up. In contrast, arteriolar calibre remained unchanged in eyes without need for PRN treatment (M3: -1.6 μm, p = 0.79 and M12: -7.0 μm, p = 0.22). For retinal venules, vessel calibre decreased both in eyes with and without need for PRN therapy at M3 (-9.5 μm, p = 0.01 and -11.6 μm, p = 0.01) as well as at M12 (-15.6 μm, p = 0.001 and -11.0 μm, p = 0.04).

CONCLUSION

Early changes in retinal arteriolar calibre are associated with an increased treatment burden during the first year of DME treatment.

Laser treatment in retinitis pigmentosa-a review

Retinitis pigmentosa (RP) is a common inherited retinal disease for which effective treatment is not yet known. This review sought to analyze the available medical literature covering the efficacy of different forms of laser treatment for RP in laboratory and clinical trials. The PubMed database was searched using the following phrases: "laser photocoagulation", "subthreshold laser", "nanolaser", "micropulse laser", "retinitis pigmentosa", "rod-cone dystrophy", and "retinal dystrophy". Results were stratified as clinical or experimental studies. Six studies involving animal models and three studies involving human subjects that examined laser treatment in RP were found. Laboratory studies on rodents favored classic laser photocoagulation as the most effective therapy for slowing the progression of proto-oncogene tyrosine-protein kinase MER-related RP. Two clinical studies on humans suggested transient but robust functional benefits of subthreshold micropulse laser treatment in RP. The available material is too scarce to define laser treatment as a standard procedure to treat RP in humans. Nondamaging retinal laser therapy should be tested more intensively in clinical trials as there is no proven negative side effect of that treatment and the theoretical background, especially the chaperone and reparative roles of heat shock proteins elicited during the procedure, supports this form of RP management.

Macular laser photocoagulation in the management of diabetic macular edema: Still relevant in 2020?

Macular laser photocoagulation (MLP) is inferior to intravitreal vascular endothelial growth factor (VEGF) inhibitors in the treatment of center-involved diabetic macular edema (DME). Ultra-widefield fluorescein angiography-guided laser photocoagulation to presumed ischemic areas of the peripheral retina or MLP do not reduce the treatment burden nor improve the visual outcomes of eyes treated with anti-VEGF drugs. Destruction of retinal tissue is not necessary to induce a therapeutic response in DME. Modern lasers are capable of producing invisible laser "burns" that do not destroy the targeted tissue using micropulse subthreshold (ST) mode where the laser's duty cycle is modified or alternatively selective retinal therapy (SRT) where ultrashort pulses of continuous wave laser selectively target the RPE. The best results with micropulse ST laser are obtained in eyes with a central macular thickness ≤400 μm. Eyes need to be treated in a continuous manner with no spaces between burns in the edematous area. Micropulse ST-MLP downregulates inflammatory biomarkers produced by activated microglial cells and Müller cells. Micropulse ST-MLP may reduce the anti-VEGF injection burden in DME. In SRT, the diseased RPE is targeted and heated with the laser with the hope that the adjacent RPE migrates and proliferates into these areas to heal the diseased RPE. There is much less experience with SRT, but the results are promising and deserve further study.

Outcomes of 25-Gauge Vitrectomy for Tractional and Nontractional Diabetic Macular Edema with Proliferative Diabetic Retinopathy

The benefit of pars plana vitrectomy with internal limiting membrane peeling for tractional macular edema and diffuse nontractional macular edema in diabetic retinopathy has been reported. Although these studies had included various stages, use of conventional 20-gauge vitrectomy system, small number of cases, single-center study, and lack of retinal structure measurements were limitations. We compared one-year outcomes of 25-gauge vitrectomy for refractory diabetic macular edema with or without the tractional proliferative membrane in proliferative diabetic retinopathy (PDR) eyes and examined the prognostic factors for postoperative visual acuity. A total of consecutive 116 PDR eyes of 116 patients that underwent 25-gauge vitrectomy for tractional macular edema (TME group: 56 eyes) or nontractional macular edema (nTME group: 60 eyes) at six centers were retrospectively reviewed. Visual acuity (VA), central macular thickness (CMT), complications, and postoperative treatments before and 12 months after vitrectomy were compared. Mean VA improved significantly in each group (both P < 0.01), and mean CMT decreased significantly in each group (both P < 0.01). Thirteen eyes underwent additional vitrectomy, six eyes developed neovascular glaucoma, six eyes received intravitreal anti-VEGF injection, and thirteen eyes received subtenon triamcinolone acetonide injection. Multiple linear regression analysis showed that baseline VA and CMT in the TME group and kidney function in the nTME group were the predictable factors of the 12-month postoperative VA. Twenty-five-gauge vitrectomy effectively improved VA and macular structure both in TME and nTME groups. Baseline VA, CMT, and kidney function are important factors affecting postoperative VA.

Is Myopia Associated with the Incidence and Progression of Diabetic Retinopathy?

PURPOSE

We sought to determine the association of refractive error and its associated determinants (axial length [AL], anterior chamber depth, and corneal curvature) with the incidence and progression of diabetic retinopathy (DR).

DESIGN

Population-based cohort study.

METHODS

A total of 1562 eyes of 840 individuals with diabetes and gradable retinal photographs (mean age [SD], 57.0 [8.3] years, 48.2% female) from the Singapore Malay and Indian Eye Studies at baseline (2004-2009) and follow-up (2011-2015) examinations were included in the analyses. Refractive error was calculated as sphere plus half negative cylinder, while AL, anterior chamber depth, and corneal curvature were assessed using optical biometry. Incident DR was defined as having no baseline DR and any DR at follow-up; incident vision-threatening DR as no baseline vision-threatening DR but present at follow-up; and DR progression as an increase in severity at follow-up from at least minimal baseline DR. Eye-specific data and generalized estimating equation models were used to account for between-eye correlation to determine the relationships between the exposures and outcomes, adjusted for traditional DR risk factors.

RESULTS

At follow-up, 164 of 1273 (12.9%) eyes had incident DR, 17 of 1542 (1.1%) eyes had incident vision-threatening DR, and 75 of 269 (27.9%) eyes with baseline DR experienced progression. A longer AL (per millimeter increase) (risk ratio 0.58 [95% confidence interval 0.38-0.88) was associated with a lower risk of incident DR. No other associations were found.

CONCLUSION

Our findings show that a longer AL is protective of incident DR.

Deep spectral learning for label-free optical imaging oximetry with uncertainty quantification

Measurement of blood oxygen saturation (sO2) by optical imaging oximetry provides invaluable insight into local tissue functions and metabolism. Despite different embodiments and modalities, all label-free optical-imaging oximetry techniques utilize the same principle of sO2-dependent spectral contrast from haemoglobin. Traditional approaches for quantifying sO2 often rely on analytical models that are fitted by the spectral measurements. These approaches in practice suffer from uncertainties due to biological variability, tissue geometry, light scattering, systemic spectral bias, and variations in the experimental conditions. Here, we propose a new data-driven approach, termed deep spectral learning (DSL), to achieve oximetry that is highly robust to experimental variations and, more importantly, able to provide uncertainty quantification for each sO2 prediction. To demonstrate the robustness and generalizability of DSL, we analyse data from two visible light optical coherence tomography (vis-OCT) setups across two separate in vivo experiments on rat retinas. Predictions made by DSL are highly adaptive to experimental variabilities as well as the depth-dependent backscattering spectra. Two neural-network-based models are tested and compared with the traditional least-squares fitting (LSF) method. The DSL-predicted sO2 shows significantly lower mean-square errors than those of the LSF. For the first time, we have demonstrated en face maps of retinal oximetry along with a pixel-wise confidence assessment. Our DSL overcomes several limitations of traditional approaches and provides a more flexible, robust, and reliable deep learning approach for in vivo non-invasive label-free optical oximetry.

Correlation between Diabetic Retinopathy Severity and Oxygen Metabolism in Patients with Diabetic Macular Edema during Treatment with Intravitreal Aflibercept

PURPOSE

To attribute data on changes in diabetic retinopathy (DR) severity during treatment of diabetic macular edema (DME) with vascular endothelial growth factor inhibitors (anti-VEGF), this study aimed to (1) examine the correlation between oxygen saturations in retinal vessels and the number of DR lesions on ultra-wide field color fundus photographs prior to anti-VEGF treatment and (2) compare changes in oxygen saturations in retinal vessels with changes in the number of DR lesions after a loading dose of three monthly intravitreal injections of 2.0 mg of aflibercept.

METHODS

This 3-month prospective study included 37 eyes of patients with DME and varying severity of peripheral DR lesions. DR lesions were graded on wide field images and retinal oxygen saturations were evaluated by retinal oximetry. Patients were then treated with three monthly intravitreal injections of 2 mg aflibercept and wide field imaging and retinal oximetry were repeated 4 weeks after the last injection. Patients with proliferative DR or previous panretinal photocoagulation were excluded.

RESULTS

Baseline retinal arteriolar oxygen saturation increased with increasing DR severity and numbers of microaneurysms, hemorrhages, and cotton wool spots (p = 0.03, 0.01, 0.03, and <0.001), while no correlation between the severity of DR lesions and retinal venular oxygen saturation was found. After treatment with intravitreal aflibercept, the severity of DR lesions significantly reduced, while retinal arteriolar and venular oxygen saturation as well as the arteriolar-venular difference remained unchanged (95.5 vs. 95.8%, p = 0.44; 62.9 vs. 64.5%, p = 0.08; 32.5 vs. 31.4%, p = 0.33).

CONCLUSION

This study demonstrated that structural DR lesions correlate with retinal arteriolar oxygen saturation in patients with DME prior to anti-VEGF treatment and that improvement in the severity of DR lesions can occur without corresponding changes in retinal oxygen metabolism during intravitreal therapy. Our results suggest that DR severity on color fundus photographs should be interpreted with caution once intravitreal therapy is initiated.

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 (τ_m) 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 τ_m at the center of the defect decreasing with eccentricity. In short spectral channel, but not in long spectral channel, τ_m 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.

Effects of panretinal photocoagulation on retinal vasculature and foveal avascular zone in diabetic retinopathy using optical coherence tomography angiography: A pilot study

Purpose

To evaluate the optical coherence tomography angiography (OCTA) parameters in patients with diabetic retinopathy following panretinal photocoagulation (PRP).

Methods

Eleven eyes of 6 patients with very severe nonproliferative diabetic retinopathy (NPDR) or early proliferative diabetic retinopathy (PDR) were recruited in this prospective interventional pilot study. All patients underwent OCTA imaging at baseline, and choroidal flow, foveal avascular zone (FAZ), retinal thickness, and vascular density were measured at baseline. Three months after treatment, OCTA was repeated, and the alteration in variables was analyzed.

Results

The FAZ area remained unchanged following treatment, (P = 0.75). Retinal thickness increased along (P = 0.02) with an increase in vascular density in the superficial and deep foveal area and the macular temporal sector (P = 0.007, 0.03 and 0.049, respectively). Choroidal flow surface area was unchanged (P = 0.10).

Conclusion

In this study, foveal vascular density increased and FAZ remained unchanged after PRP for diabetic retinopathy.

SIGNIFICANT REDUCTION OF BOTH PERIPAPILLARY AND SUBFOVEAL CHOROIDAL THICKNESS AFTER PANRETINAL PHOTOCOAGULATION IN PATIENTS WITH TYPE 2 DIABETES

PURPOSE

To evaluate changes in peripapillary choroidal thickness (PCT) and subfoveal choroidal thickness (SFCT) after panretinal photocoagulation (PRP) for diabetic retinopathy.

METHODS

This retrospective interventional study included 59 treatment-naive eyes of 33 patients who underwent PRP and completed ≥12 months of follow-up. Peripapillary choroidal thickness and SFCT were measured at baseline and 1, 3, 6, and 12 months post-PRP. Differences between baseline and 12 months (ΔSFCT and ΔPCT) and percentage changes (ΔSFCT or ΔPCT/baseline × 100%) were determined.

RESULTS

Mean SFCT was 287.7 ± 76.7 μm (139.0-469.0 μm) at baseline and 225.8 ± 62.0 μm (102.5-379.5 μm) 12 months post-PRP (P < 0.001). Mean PCT was 161.2 ± 16.5 μm (75.3-308.1 μm) at baseline and 128.4 ± 41.8 μm (73.0-212.9 μm) 12 months post-PRP (P < 0.001). ΔSFCT was -61.3 ± 28.7 μm (-139.5 to -17.0 μm), and %SFCT was 21.2 ± 7.2% (6.8% to 36.1%). ΔPCT was -36.4 ± 23.2 μm (-149.1 to 5.4 μm), and %PCT was 22.4 ± 12.0% (2.5% to 62.6%). Diabetic retinopathy severity was the only factor significantly correlated with %SFCT (β = 0.500, P = 0.004) and %PCT (β = 0.152, P = 0.024).

CONCLUSION

Both PCT and SFCT reduced significantly after PRP. Diabetic retinopathy severity was significantly correlated with post-PRP changes of peripapillary and SFCT.

How do we evaluate the role of focal/grid photocoagulation in the treatment of diabetic macular edema?

Vascular endothelial growth factor inhibitors (anti-VEGF) have consistently demonstrated efficacy and safety and changed both the aim and perspectives of diabetic macular edema (DME) treatment. Hence, the present and future role of focal/grid laser photocoagulation in DME treatment has been subjected to some debate. However, extensive insight into technical advances in novel laser systems, treatment protocols of anti-VEGF trials and the functional impact of modern focal/grid photocoagulation is needed to evaluate the present and future role of photocoagulation in DME treatment. Across a wide range of clinical trials laser therapy was required as adjunctive/rescue treatment in approximately 20-50% of patients receiving anti-VEGF monotherapy for centre involving DME. Further, a lower retreatment rate and a more stable reduction in retinal thickness have been demonstrated in more studies. However, lacking information on the laser systems used, their technical specifications and protocols of application often complicates direct comparison of results in anti-VEGF trials. Hence, this paper aimed to provide an overview of the currently available data relevant to the potential role of focal/grid laser photocoagulation in DME treatment including a thorough overview of the current most commonly used laser systems. Results with subthreshold diode micropulse laser photocoagulation are intriguing and may offer a valuable option as adjunctive therapy to anti-VEGF treatment. However, more well-designed studies on combination therapy are warranted to determine the full potential of modern retinal photocoagulation systems. In conclusion, current data suggest that focal/grid laser therapy should still be an option for consideration as adjunctive therapy in many patients.

Macular vascular circulation and retinal oxygen saturation changes for idiopathic macular epiretinal membrane after vitrectomy

PURPOSE

To investigate the postoperative changes in retinal-choroidal blood flow area and retinal vascular oxygen saturation among patients with idiopathic macular epiretinal membranes (iERMs).

METHODS

This study prospectively included 24 eyes of 24 consecutive patients who underwent vitrectomy for iERMs. The flow area of choriocapillary layer, retinal superficial capillary plexuses (SCPs) and retinal deep capillary plexuses (DCPs) were performed using optical coherence tomography angiography with angiovue prototype software, and retinal vascular oxygen saturation was measured using retinal oximeter with the built-in software. The flow area of choriocapillary layers and mean retinal vessel oxygen saturation before and after surgery were compared.

RESULTS

Three months after vitrectomy, the foveal flow area of choriocapillary layer increased clinically significantly from 1.5 ± 0.2 to 1.6 ± 0.2 mm² (p = 0.02). The retinal vascular changes of SCPs and DCPs were not statistically significant. The mean retinal arterial oxygen saturation was 89.9 ± 11.3% preoperatively and increased to 94.5 ± 9.7% postoperatively (p = 0.04). Foveal retinal thickness revealed a clinically significant decrease from 547.8 ± 88.2 μm to 403.0 ± 47.5 μm after surgery (p < 0.05). Postoperative best corrected visual acuity had no statistically significant correlation with foveal flow area of the choriocapillary layer and retinal vascular oxygen saturation.

CONCLUSIONS

There was a decrease of retinal thickness, an improved flow area of choriocapillary layer in macular region, and an increase of retinal arterial vascular oxygen among iERMs patients after vitrectomy.

Retinal capillary perfusion: Spatial and temporal heterogeneity

The central role of the cardiovascular system is to maintain adequate capillary perfusion. The spatially and temporally heterogeneous nature of capillary perfusion has been reported in some organs. However, such heterogeneous perfusion properties have not been sufficiently explored in the retina. Arguably, spatial and temporal heterogeneity of capillary perfusion could be more predominant in the retina than that in other organs. This is because the retina is one of the highest metabolic demand neural tissues yet it has a limited blood supply due to optical requirements. In addition, the unique heterogeneous distribution of retinal neural cells within different layers and regions, and the significant heterogeneity of intraretinal oxygen distribution and consumption add to the complexity. Retinal blood flow distribution must match consumption of nutrients such as oxygen and glucose within the retina at the cellular level in order to effectively maintain cell survival and function. Sophisticated local blood flow control in the microcirculation is likely required to control the retinal capillary perfusion to supply local retinal tissue and accommodate temporal and spatial variations in metabolic supply and demand. The authors would like to update the knowledge of the retinal microvessel and capillary network and retinal oxidative metabolism from their own studies and the work of others. The coupling between blood supply and energy demands in the retina is particularly interesting. We will mostly describe information regarding the retinal microvessel network and retinal oxidative metabolism relevant to the spatial and temporal heterogeneity of capillary perfusion. We believe that there is significant and necessary spatial and temporal heterogeneity and active regulation of retinal blood flow in the retina, particularly in the macular region. Recently, retinal optical coherence tomography angiography (OCTA) has been widely used in ophthalmology, both experimentally and clinically. OCTA could be a valuable tool for examining retinal microvessel and capillary network structurally and has potential for determining retinal capillary perfusion and its control. We have demonstrated spatial and temporal heterogeneity of capillary perfusion in the retina both experimentally and clinically. We have also found close relationships between the smallest arterioles and capillaries within paired arterioles and venules and determined the distribution of smooth muscle cell contraction proteins in these vessels. Spatial and temporal heterogeneity of retinal capillary perfusion could be a useful parameter to determine retinal microvessel regulatory capability as an early assay for retinal vascular diseases. This topic will be of great interest, not only for the eye but also other organs. The retina could be the best model for such investigations. Unlike cerebral vessels, retinal vessels can be seen even at the capillary level. The purpose of this manuscript is to share our current understanding with the readers and encourage more researchers and clinicians to investigate this field. We begin by reviewing the general principles of microcirculation properties and the spatial and temporal heterogeneity of the capillary perfusion in other organs, before considering the special requirements of the retina. The local heterogeneity of oxygen supply and demand in the retina and the need to have a limited and well-regulated retinal circulation to preserve the transparency of the retina is discussed. We then consider how such a delicate balance of metabolic supply and consumption is achieved. Finally we discuss how new imaging methodologies such as optical coherence tomography angiography may be able to detect the presence of spatial and temporal heterogeneity of capillary perfusion in a clinical setting. We also provide some new information of the control role of very small arterioles in the modulation of retinal capillary perfusion which could be an interesting topic for further investigation.

Diabetic macular edema: Evidence-based management

Diabetic macular edema (DME) is the most common cause of vision loss in patients with diabetic retinopathy with an increasing prevalence tied to the global epidemic in type 2 diabetes mellitus. Its pathophysiology starts with decreased retinal oxygen tension that manifests as retinal capillary hyperpermeability and increased intravascular pressure mediated by vascular endothelial growth factor (VEGF) upregulation and retinal vascular autoregulation, respectively. Spectral domain optical coherence tomography (SD-OCT) is the cornerstone of clinical assessment of DME. The foundation of treatment is metabolic control of hyperglycemia and blood pressure. Specific ophthalmic treatments include intravitreal anti-VEGF drug injections, intravitreal corticosteroid injections, focal laser photocoagulation, and vitrectomy, but a substantial fraction of eyes respond incompletely to all of these modalities resulting in visual loss and disordered retinal structure and vasculature visible on SD-OCT and OCT angiography. Efforts to close the gap between the results of interventions within randomized clinical trials and in real-world contexts, and to reduce the cost of care increasingly occupy innovation in the social organization of ophthalmic care of DME. Pharmacologic research is exploring other biochemical pathways involved in retinal vascular homeostasis that may provide new points of intervention effective in those cases unresponsive to current treatments.

Early-scatter laser photocoagulation promotes the formation of collateral vessels in branch retinal vein occlusion

PURPOSE

To investigate the effect of early-scatter laser photocoagulation on the formation of collateral vessels in branch retinal vein occlusion.

METHODS

The medical records of 40 cases (40 patients) of branch retinal vein occlusion with macular edema were retrospectively reviewed. Of them, 23 patients were treated with intravitreal bevacizumab injection and 17 patients underwent intravitreal bevacizumab injection with additional laser treatment. Early-scatter laser photocoagulation was applied for capillary non-perfusion areas, regardless of retinal neovascularization. Collateral vessel presence, recurrence rate of macular edema, and number of intravitreal bevacizumab injections were compared between the groups.

RESULTS

During the follow-up period, collateral vessel formation was noted in 10/23 eyes (43.5%) in the intravitreal bevacizumab injection group and 15/17 eyes (88.2%) in the laser combined treatment group (p = 0.004). The recurrence rate of macular edema was lower in the laser combined treatment group (29.4%) than in the intravitreal bevacizumab injection group (65.2%); this difference was statistically significant (p = 0.025). The average numbers of intravitreal bevacizumab injections were 3.57 ± 3.23 in the intravitreal bevacizumab group and 2.14 ± 2.26 in the laser combined treatment group (p = 0.044).

CONCLUSION

Early-scatter laser photocoagulation promotes collateral vessel formation; the presence of collateral vessels seemed to affect the course of macular edema in branch retinal vein occlusion. Combined early-scatter laser photocoagulation treatment after intravitreal bevacizumab injection lowered the recurrence rate of macular edema and number of intravitreal bevacizumab injections in the cases of branch retinal vein occlusion.

Quantitative quality-control metrics for in vivo oximetry in small vessels by visible light optical coherence tomography angiography

Biological functions rely on local microvasculature to deliver oxygen and nutrients and carry away metabolic waste. Alterations to local oxygenation levels are manifested in diseases including cancer, diabetes mellitus, etc. The ability to quantify oxygen saturation (sO2) within microvasculature in vivo to assess local tissue oxygenation and metabolic function is highly sought after. Visible light optical coherence tomography (vis-OCT) angiography has shown promise in reaching this goal. However, achieving reliable measurements in small vessels can be challenging due to the reduced contrast and requires data averaging to improve the spectral data quality. Therefore, a method for quality-control of the vis-OCT data from small vessels becomes essential to reject unreliable readings. In this work, we present a quantitative metrics to evaluate the spectral data for a reliable measurement of sO2, including angiography signal to noise ratio (SNR), spectral anomaly detection and discard, and theory-experiment correlation analysis. The thresholds for each quantity can be flexibly adjusted according to different applications and system performance. We used these metrics to measure sO2 of C57BL/6J mouse lower extremity microvasculature and validated it by introducing hyperoxia for expected sO2 changes. After validation, we applied this protocol on C57BL/6J mouse ear microvasculature to conduct in vivo small blood vessel OCT oximetry. This work seeks to standardize the data processing method for in vivo oximetry in small vessels by vis-OCT.

New insights into diabetic retinopathy by OCT angiography

Diabetic retinopathy (DR) is one of the most common diabetic complications, which has become a leading cause for vision loss, mainly because of macular edema and vitreous hemorrhage. Optical coherence tomography (OCT) angiography is a novel technique to visualize vascular changes including microaneurysm, non-perfusion area, intraretinal microvascular abnormalities, and neovascularization. Recently, it is possible to quantify vascular density, foveal avascular zone area, non-perfusion area objectively using OCT angiography. In addition, OCT angiography also provides an alternative method to evaluate the effect of anti-vascular endothelial growth factor (VEGF) treatments by providing high resolution images of macular microcirculatory abnormalities. Thus OCT angiography is an effective method to investigate the vascular changes of the disease, and can also be potentially applied in the diagnosis, treatment, and follow up of DR.

Modulation of the rod outer segment aerobic metabolism diminishes the production of radicals due to light absorption

Oxidative stress is a primary risk factor for both inflammatory and degenerative retinopathies. Our previous data on blue light-irradiated retinas demonstrated an oxidative stress higher in the rod outer segment (OS) than in the inner limb, leading to impairment of the rod OS extra-mitochondrial aerobic metabolism. Here the oxidative metabolism and Reactive Oxygen Intermediates (ROI) production was evaluated in purified bovine rod OS in function of exposure to different illumination conditions. A dose response was observed to varying light intensities and duration in terms of both ROI production and ATP synthesis. Pretreatment with resveratrol, inhibitor of F₁F_o-ATP synthase, or metformin, inhibitor of the respiratory complex I, significantly diminished the ROI production. Metformin also diminished the rod OS Complex I activity and reduced the maximal OS response to light in ATP production. Data show for the first time the relationship existing in the rod OS between its -aerobic- metabolism, light absorption, and ROI production. A beneficial effect was exerted by metformin and resveratrol, in modulating the ROI production in the illuminated rod OS, suggestive of their beneficial action also in vivo. Data shed new light on preventative interventions for cone loss secondary to rod damage due to oxidative stress.

Idiopathic macular telangiectasis type 2 and co-existent diabetic retinopathy

Background

To study the interaction between idiopathic macular telangiectasis type 2 (MacTel2) and coexistent diabetic retinopathy (DR) during long term follow up.

Methods

A retrospective chart review was done for all eyes with MacTel2 and DR with a minimum 2 years follow up. Eyes with other retinal disorders and poor quality imaging were excluded. Data collected included demographics, presenting visual acuity, systemic evaluation, treatments done, duration of follow up, and final visual outcomes.

Results

Out of 951 patients with MacTel2, 277 patients had diabetes. Out of 277 patients, 44 eyes of 22 patients had MacTel2 coexisting with DR. Twenty-eight eyes of 14 patients were included in this study. All cases of MacTel2 were bilateral with a preponderance of women (71.42%). Mean follow up was 93.07 ± 84.03 months with a mean random blood sugar level of 135.41 ± 45.47 mg% at presentation. Twenty-five (89.28%) eyes presented with mild non-proliferative diabetic retinopathy. Two (7.14%) eyes progressed in their DR staging from baseline. Stage III MacTel2 were noted in 11 (39.28)% eyes at baseline. None of these eyes progressed to stage V during follow up. Mean presenting logMAR BCVA was 0.214 ± 0.227 which dropped to 0.399 ± 0.301 at last visit (p = 0.0005). Diabetic macula edema (DME) was not noted in any eye till last follow up.

Conclusions

12.5% of eyes with MacTel2 in diabetic patients had coexistent DR. MacTel2 led to slowly progressive visual loss irrespective of the presence of DR.

Single capillary oximetry and tissue ultrastructural sensing by dual-band dual-scan inverse spectroscopic optical coherence tomography

Measuring capillary oxygenation and the surrounding ultrastructure can allow one to monitor a microvascular niche and better understand crucial biological mechanisms. However, capillary oximetry and pericapillary ultrastructure are challenging to measure in vivo. Here we demonstrate a novel optical imaging system, dual-band dual-scan inverse spectroscopic optical coherence tomography (D2-ISOCT), that, for the first time, can simultaneously obtain the following metrics in vivo using endogenous contrast: (1) capillary-level oxygen saturation and arteriolar-level blood flow rates, oxygen delivery rates, and oxygen metabolic rates; (2) spatial characteristics of tissue structures at length scales down to 30 nm; and (3) morphological images up to 2 mm in depth. To illustrate the capabilities of D2-ISOCT, we monitored alterations to capillaries and the surrounding pericapillary tissue (tissue between the capillaries) in the healing response of a mouse ear wound model. The obtained microvascular and ultrastructural metrics corroborated well with each other, showing the promise of D2-ISOCT for becoming a powerful new non-invasive imaging tool.