Vitrectomy in the management of diabetic retinopathy

Pharmacological adjuvants for diabetic vitrectomy surgery

Diabetic vitrectomy is a highly intricate surgical procedure performed during the advanced stages of diabetic retinopathy (DR). It is used to treat conditions such as tractional or combined retinal detachment, vitreous hemorrhage, and subhyaloid hemorrhage, which are all severe manifestations of proliferative DR. The results of the surgery are uncertain and variable. Vitreoretinal surgery has made significant progress since the early stages of vitrectomy. In the past ten years, advancements in intravitreal pharmacotherapy have emerged, offering new possibilities to improve the surgical results for our patients. Within the realm of medical terminology, an "adjunct" refers to a pharmaceutical or substance employed to aid or expedite the primary therapeutic intervention for a particular ailment. Their introduction has broadened the range of therapeutic choices that are accessible prior to, during, and following surgical procedures. This review article will specifically analyze the pharmacological adjuncts used in diabetic vitrectomy surgery, with a focus on their role in facilitating or aiding specific steps of the procedure. The implementation of this system of categorization offers benefits to the surgeon by allowing them to foresee potential difficulties that may occur during the surgical procedure and to choose the appropriate pharmacological agent to effectively tackle these challenges, thus enhancing surgical success rates.

Determining the Superiority of Vitrectomy vs Aflibercept for Treating Dense Diabetic Vitreous Hemorrhage: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

This review aimed to systematically compare the efficacy and safety of intravitreal aflibercept (IVA) and vitrectomy for treating severe vitreous hemorrhage (VH) secondary to proliferative diabetic retinopathy (PDR). The review was conducted in accordance with PRISMA guidelines. A search strategy, including the MEDLINE, Embase, Cochrane Central Register of Controlled Trials, and US National Library of Medicine databases, was developed to identify randomized controlled trials (RCTs) that compared vitrectomy and IVA for managing VH due to PDR (participant age ≥ 18 years). The primary outcome measure was the difference in the mean visual acuity between the two treatment groups at 1, 6, and 24 months. Outcome measures included clearance of VH (in weeks), the incidence of recurrent VH, and the rate of complications. The studies were evaluated using the Cochrane Bias (ROB) tool. We identified 774 articles; six articles met the inclusion criteria, and two were ultimately included (n = 239 eyes). With or without PRP, IVA injections and vitrectomy were performed in 117 and 122 eyes, respectively. The mean BCVA at one month was significantly better in the vitrectomy group (MD=0.22, CI:0.10-0.34, p=0.0003), but no difference was found at six months (MD=0.04, CI: -0.04-0.12, p=0.356). The incidence of recurrent VH was significantly higher in the IVA group (OR=5.05, CI:2.71-9.42, p<0.0001). The probability of recurrent VH was five times greater in the IVA group than that in the vitrectomy group. There were no significant differences in the overall proportions of intra- or postoperative complications (OR=0.64, CI: 0.09-4.85, p=0.669). None of the studies had a low ROB in any of the seven domains. We conclude that IVA can be considered a viable treatment modality for diabetic VH in patients with a good follow-up. Vitrectomy initially provides better visual effect, faster VH recovery, and lower VH recurrence than IVA injections.

Post-vitrectomy delayed retinal breaks in proliferative diabetic retinopathy

PURPOSE

To report a series of cases of post-operative new secondary retinal breaks following vitrectomy for proliferative diabetic retinopathy (PDR).

METHODS

This retrospective case series included data of patients diagnosed with post-operative retinal breaks following uneventful vitrectomy surgery for PDR from January 2018 to December 2021.

RESULTS

New post-vitrectomy retinal breaks in PDR were seen in 7% of eyes (n = 10/148 eyes; 10 patients). Age of study patients ranged from 45 to 69 years and there were 8 males. Vitreous surgery was performed for vitreous hemorrhage in six eyes, macular tractional retinal detachment in three eyes and epiretinal membrane in one eye. Tractional fibrovascular proliferation near the retinal break prior to its development was noted either pre- or intra-operatively in 8 eyes. Mean time interval between the vitreous surgery and secondary retinal break development was 6.4 months. Residual fibrous tissue post-surgery adjacent to the break was noted in 4 cases. Sclerosed retinal vessel was noted in 4 eyes and associated inner retinal thinning or schisis in 5 eyes. No retinal detachment was noted in any case. Prophylactic barrage was done in 4 eyes. Last follow-up interval ranged from 4 to 53 months and visual acuity ranged from 6/6 to 6/60. No subretinal fluid, traction or break enlargement was noted at the last visit.

CONCLUSION

Delayed post-operative retinal breaks following vitrectomy are uncommon in PDR eyes. Careful preoperative evaluation of the retinal proliferations, intraoperative dissection of the membranes and regular post-operative reviews are vital in anticipating the development of delayed post-vitrectomy retinal breaks. Observation could be the management strategy for these breaks.

American Association of Clinical Endocrinology Clinical Practice Guideline: Developing a Diabetes Mellitus Comprehensive Care Plan-2022 Update

OBJECTIVE

The objective of this clinical practice guideline is to provide updated and new evidence-based recommendations for the comprehensive care of persons with diabetes mellitus to clinicians, diabetes-care teams, other health care professionals and stakeholders, and individuals with diabetes and their caregivers.

METHODS

The American Association of Clinical Endocrinology selected a task force of medical experts and staff who updated and assessed clinical questions and recommendations from the prior 2015 version of this guideline and conducted literature searches for relevant scientific papers published from January 1, 2015, through May 15, 2022. Selected studies from results of literature searches composed the evidence base to update 2015 recommendations as well as to develop new recommendations based on review of clinical evidence, current practice, expertise, and consensus, according to established American Association of Clinical Endocrinology protocol for guideline development.

RESULTS

This guideline includes 170 updated and new evidence-based clinical practice recommendations for the comprehensive care of persons with diabetes. Recommendations are divided into four sections: (1) screening, diagnosis, glycemic targets, and glycemic monitoring; (2) comorbidities and complications, including obesity and management with lifestyle, nutrition, and bariatric surgery, hypertension, dyslipidemia, retinopathy, neuropathy, diabetic kidney disease, and cardiovascular disease; (3) management of prediabetes, type 2 diabetes with antihyperglycemic pharmacotherapy and glycemic targets, type 1 diabetes with insulin therapy, hypoglycemia, hospitalized persons, and women with diabetes in pregnancy; (4) education and new topics regarding diabetes and infertility, nutritional supplements, secondary diabetes, social determinants of health, and virtual care, as well as updated recommendations on cancer risk, nonpharmacologic components of pediatric care plans, depression, education and team approach, occupational risk, role of sleep medicine, and vaccinations in persons with diabetes.

CONCLUSIONS

This updated clinical practice guideline provides evidence-based recommendations to assist with person-centered, team-based clinical decision-making to improve the care of persons with diabetes mellitus.

DRDB: A Machine Learning Platform to Predict Chemical-Protein Interactions towards Diabetic Retinopathy

Diabetic retinopathy (DR), a diabetic microangiopathy caused by diabetes, affects approximately 93 million people, worldwide. However, the drugs used to treat DR have limited efficacy and the variety of side effects. This is possibly because the complicated pathogenesis of DR is associated with multiple proteins. In this work, we attempted to identify potential drugs against DR-associated proteins and predict potential targets for drugs using in silico prediction of chemical-protein interactions (CPI) based on multitarget quantitative structure-activity relationship (mt-QSAR) method. Therefore, we developed 128 binary classifiers to predict the CPI for 15 DR targets using random forest (RF), k-nearest neighbours (KNN), support vector machine (SVM), and neural network (NN) algorithms with MACCS, extended connectivity fingerprints (ECFP6) fingerprints, and protein descriptors. In order to facilitate discovery of the novel drugs and target identification using the 128 binary classifiers, a free web server (DRDB) was developed. Compound Danshen Dripping Pills (CDDP), composed of Salvia miltiorrhiza, Panax notoginseng, and borneol, is commonly used in the treatment of cardiovascular diseases. To explore the applicability of DRDB, the potential CPIs of CDDP in treatment of DR were investigated based on DRDB. In vitro experimental validation demonstrated that cryptotanshinone and protocatechuic acid, two key components of CDDP, are capable of targeting ICAM-1 which is one of the key target of DR. We hope that this work can facilitate development of more effective clinical strategies for the treatment of DR.

Ultrasonic fragmentation for removing thick organized clots during diabetic vitrectomy - A novel technique

A 65-year-old male with proliferative diabetic retinopathy (PDR) and non-clearing vitreous hemorrhage underwent 25G pars plana vitrectomy (PPV). A large disk of thick organized blood of 5 disk diameter (DD) size was encountered in subhyaloid space. All attempts including lower cut rates to remove this disk using a 25G cutter turned futile. We used a 20G fragmatome to safely remove this hard clot from vitreous cavity in 50 s. Surgical time for removal of similar clot of 3 DD by 25G cutter in another eye was 5 min. Removal of thick clotted subhyaloid blood by ultrasonic fragmentation during diabetic vitrectomy is a safe, faster, and useful maneuver.

Efficacy and safety of Chinese medicines for vitreous hemorrhage: A protocol for systematic review and meta-analysis

BACKGROUND

Vitreous hemorrhage (VH) is a common ophthalmic disease with a high rate of blindness, which will seriously affect the quality of life of patients and bring great burden to patients' families and society. The treatment for VH contains medical therapy, lasers, and surgery. At present, there is no recognized western medicine with definite curative effect and little side effect for the treatment of VH. In most cases, PRP is not available to treat VH; intravitreal injection or surgical treatment is adopted as the primary therapy. However, in the long-term treatment, the effect of the above-mentioned treatment is not satisfactory, so many patients choose oral Chinese medicines, which has been widely used in China to treat VH. Numerous clinical trials have demonstrated that Chinese medicines can promote the absorption of VH and improve the visual function of patients. The purpose of this review is to evaluate the efficacy and safety of Chinese medicines in the treatment of VH and inform a decision aid for the clinical encounter between patients and clinicians. Besides, it is beneficial to establish a future research agenda.

METHODS

The systematic review will include all of the randomized controlled trials on the efficacy and safety of Chinese medicines for VH. Nine electronic databases, namely PubMed, Web of Science, EMBASE, the Cochrane Library, Google Scholar, China National Knowledge Infrastructure (CNKI), Wanfang Database, China Science and Technology Journal database (VIP), and CBM, will be searched normatively on the basis of the rule of each database from the inception to August 31, 2019. We will also search registers of clinical trials, potential gray literature, and conference abstracts. There are no limits on language and publication status. The literature screening, data extraction, and quality assessment will be conducted by 2 reviewers independently. The reporting quality and risk of bias will be assessed by other 2 researchers. Standard of curative effect and total treatment efficacy rate were assessed as the primary outcome. The secondary outcomes will include the curative effect of single symptom and sign, the improvement rate of single auxiliary examination, withdrawal and reduction of western medicines in a course of treatment, maintenance of western medicines after the course of treatment, laboratory efficacy indexes. Meta-analysis will be performed using RevMan5.3 software provided by the Cochrane Collaboration.

RESULTS

This study will provide a comprehensive review based on current evidence of Chinese medicines treatment for VH in several aspects, including standard of curative effect, total treatment efficacy rate, the curative effect of single symptom and sign, the improvement rate of single auxiliary examination, withdrawal and reduction of western medicines in a course of treatment, laboratory efficacy indexes, total treatment efficacy, and safety, among others.

CONCLUSION

The conclusion of this study will provide evidence to determine whether Chinese medicines are an effective and safe intervention for patients with VH.

ETHICS AND DISSEMINATION

It is not necessary to obtain ethical approval for this study. The systematic review will be published in a peer-reviewed journal, presented at conferences and will be shared on social media platforms.

PROSPERO REGISTRATION NUMBER

PROSPERO CRD42020152321.

Recurrent retinal detachment after diabetic vitrectomy

PURPOSE

To investigate the characteristics of recurrent retinal detachment (RD) after diabetic vitrectomy (DV).

METHODS

Consecutive cases underwent vitrectomy for recurrent RD after DV was collected and separated into the following four groups for analysis: rhegmatogenous RD (RRD), pure tractional RD (Proliferative Subgroup 1), combined RD with proliferative tissue within the equator (Proliferative Subgroup 2), and combined RD with both posterior and peripheral proliferations (Proliferative Subgroup 3).

RESULTS

Of the 41 cases enrolled, retinal reattachment was achieved in 73.2%. Over all, visual acuity was statistically better after operation (p = 0.001). All cases in the RRD group (four cases) had reattachment and a better final vision (p = 0.008). In the proliferative subgroups, those with pure tractional RD (Subgroup 1, seven cases) had the best visual acuity at the time of recurrent RD (p = 0.002). Subgroups 2 and 3 showed statistically significant better final visual acuity (p = 0.045 and 0.019, respectively). Poor preoperative vision (p = 0.001), non-attachment (p = 0.004), and neovascular glaucoma (p = 0.001) were associated with poor prognosis.

CONCLUSIONS

Visual acuity may improve after operation for recurrent RD after diabetic vitrectomy. Visual prognosis was better in cases with pure RRD. In the proliferative subgroups, vision was impaired by the development of neovascular glaucoma and retinal non-attachment.

Genotypes and Phenotypes: A Search for Influential Genes in Diabetic Retinopathy

Although gene–environment interactions are known to play an important role in the inheritance of complex traits, it is still unknown how a genotype and the environmental factors result in an observable phenotype. Understanding this complex interaction in the pathogenesis of diabetic retinopathy (DR) remains a big challenge as DR appears to be a disease with heterogenous phenotypes with multifactorial influence. In this review, we examine the natural history and risk factors related to DR, emphasizing distinct clinical phenotypes and their natural course in retinopathy. Although there is strong evidence that duration of diabetes and metabolic factors play a key role in the pathogenesis of DR, accumulating new clinical studies reveal that this disease can develop independently of duration of diabetes and metabolic dysfunction. More recently, studies have emphasized the role of genetic factors in DR. However, linkage analyses, candidate gene studies, and genome-wide association studies (GWAS) have not produced any statistically significant results. Our recently initiated genomics study, the Diabetic Retinopathy Genomics (DRGen) Study, aims to examine the contribution of rare and common variants in the development DR, and how they can contribute to clinical phenotype, rate of progression, and response to available therapies. Our preliminary findings reveal a novel set of genetic variants associated with proangiogenic and inflammatory pathways that may contribute to DR pathogenesis. Further investigation of these variants is necessary and may lead to development of novel biomarkers and new therapeutic targets in DR.

Gravity influences bevacizumab distribution in an undisturbed balanced salt solution in vitro

PURPOSE

The effects of gravity on bevacizumab or the recommended head position after intraocular bevacizumab injection have not been reported. To evaluate the effect of gravity on bevacizumab in vitro, we added bevacizumab to the upper part of a test tube filled with balanced salt solution (BSS) and examined its distribution over time.

MATERIALS AND METHODS

Sixty-four test tubes were divided equally into two groups; group 1 (32, collected from upper part of the tube) and group 2 (32, collected from lower part of the tube). Each test tube was filled with 5 mL BSS before bevacizumab (1.25 mg/0.05 mL) was added, and then stored at 36°C. Bevacizumab concentration in 8 test tubes from each group was measured at 12, 24, 48, and 168 h using an enzyme-linked immunosorbent analysis (ELISA) kit. Mann-Whitney and Jonckheere-Terpstra tests were used for statistical analysis.

RESULTS

Bevacizumab concentration was significantly higher in Group 2 than in Group 1 at 12, 24, 48, and 168 h (12, 24, 48, and 168 h; P < 0.01 each; Mann-Whitney test). The mean change in bevacizumab concentration over time tended to increase in Group 1 (P < 0.01; Jonckheere-Terpstra test), but tended to decrease in Group 2 (P < 0.01; Jonckheere-Terpstra test).

CONCLUSIONS

The significant differences in concentration between the upper and lower parts even after a considerable amount of storage time showed that bevacizumab did not dissolve immediately and diffused evenly throughout the solution. It appeared that more bevacizumab settled in the lower part of the tube than in the upper part because of gravitational force. However, the concentration difference between the upper and lower parts decreased as bevacizumab gradually diffused over time, indicating that the difference in concentration due to gravity was more significant at the beginning of bevacizumab injection.

Effect of Pars Plana Vitrectomy With or Without Cataract Surgery in Patients with Diabetes: A Systematic Review and Meta-Analysis

INTRODUCTION

Pars plana vitrectomy (PPV) is considered to be an essential and effective surgical approach for the management of complications of diabetic retinopathy. Given the high rate of accelerated cataract progression after PPV, PPV combined with cataract surgery appears to be an attractive treatment option for patients with diabetes. However, this combined surgical approach remains controversial in terms of effectiveness and safety. We have therefore conducted a meta-analysis to evaluate the treatment outcome of PPV with or without cataract surgery.

METHODS

A systematic search of three electronic databases (PubMed, Web of Science, and the Cochrane Library) was performed to identify relevant articles, using the key words "pars plana vitrectomy," "cataract," and "diabetic retinopathy." Main outcome measures included the final visual acuity and postoperative complications. The incidence of postoperative complications was pooled using odds ratio (OR) with 95% confidence intervals in a random effect model.

RESULTS

Ultimately, one randomized controlled trial (RCT) and four high-quality retrospective studies met the inclusion criteria and were included in the meta-analysis. In four of these studies, final visual acuity did not vary significantly between patients undergoing PPV alone and those undergoing PPV combined with cataract surgery (combined surgery). Only one study reported better visual improvement in the combined treatment group. Our analysis also showed that most phakic eyes after PPV had cataract progression with varying degrees. In addition, patients receiving PPV alone had a lower risk of neovascular glaucoma (OR 0.36; P  < 0.05), iris synechias to anterior capsule (OR 0.36; P  < 0.05), and iris rubeosis (OR 0.26; P  < 0.05) compared with those receiving combined surgery.

CONCLUSION

Overall, our findings show that PPV combined with cataract surgery achieved good outcomes without a substantial increased risk to visual acuity or most complications. Given the high rates of cataract progression after PPV, combined surgery may be the more appropriate treatment for patients with diabetes and coexistent visually significant cataract.

Outcomes of vitrectomy for diabetic tractional retinal detachment in Chicago's county health system

PURPOSE

To examine outcomes of 23-gauge (23G) pars plana vitrectomy (PPV) for complex diabetic tractional retinal detachment (TRD) in Chicago's Cook County Health and Hospitals System (CCHHS).

MATERIALS AND METHODS

This is a retrospective noncomparative study of diabetic TRD cases that underwent PPV at CCHHS. Primary retinal reattachment rate, visual function, and postoperative complications were analyzed.

RESULTS

Sixty nine consecutive cases were included. Primary reattachment and final attachment were achieved in 68/69 eyes (98.6%). Secondary retinal detachment was noted in 1 eye (1.4%). Vitreous hemorrhage requiring repeat PPV developed in 5 eyes (7.2%) and reoperation due to other complications was required in 4/69 eyes (5.8%). Perfluoropropane (C3F8) gas tamponade was used in 91.3% of eyes and silicone oil in 8.7% of eyes. Mean LogMAR visual acuity significantly improved from 1.84 ± 0.61 to 0.93 ± 0.66, (P<0.0001). Vision was stabilized or improved in 66 eyes (95.7%). Visual acuity of 20/200 or better was achieved in 49/69 eyes (71.0%) and 20/50 or better in 16/69 eyes (23.2%).

CONCLUSIONS

Even in patients with severe and advanced diabetic TRD pathology and unique demographics as seen in CCHHS, modern vitrectomy techniques can provide excellent anatomical and visual outcomes.

Postoperative Complications of Pars Plana Vitrectomy for Diabetic Retinal Disease

Despite recent advances in the medical management of diabetic retinal disease, there remain established indications for vitreoretinal surgery in the treatment of severe proliferative diabetic retinopathy. These include non-clearing vitreous hemorrhage and tractional retinal detachment. Advances in surgical instrumentation, technique, and experience have led to improved visual outcomes, as well as a corresponding decrease in the incidence of postoperative complications. However, the presence of systemic and ocular factors in diabetic patients increases the risk of adverse events compared to non-diabetic individuals. This review will focus on the most important postoperative complications following pars plana vitrectomy, with specific considerations for the diabetic patient.

Outcomes of transconjunctival sutureless 27-gauge micro-incision vitrectomy surgery in diabetic vitreous haemorrhage

Objective:

To evaluate the visual outcomes of 27-gauge transconjunctival sutureless vitrectomy surgery and its complications in patients with diabetic vitreous hemorrhage.

Methods:

A quasi-experimental study was conducted where eighty seven eyes of 87 uncontrolled type II diabetes mellitus patients presenting with diabetic vitreous hemorrhage were selected to undergo 27-gauge transconjunctival sutureless micro-incision vitrectomy surgery. Main outcome measured was best corrected visual acuity (BCVA). Post-operative complications were also screened for at each visit. The follow ups were at post-operative day one, one month, three months and six months respectively.

Results:

Out of 87 patients, 52 (59.8%) were males and 35 (40.2%) were females. The mean age of the patients was 52.32 ± 6.78 years (95% CI: 53.13 - 55.57). For most of the patients, the BCVA improved progressively with each subsequent follow up visit. Pre-operative BCVA was 1.01 ± 0.206 logMar, compared to BCVA at final follow up of 0.44 ± 0.231 (p-value < 0.001). Six (6.9%) patients developed recurrent vitreous hemorrhage during the study period, four (4.6%) developed cataract, one (1.1%) had increased intraocular pressure and sub conjunctival hemorrhage was present in two (2.3%).

Conclusion:

27-gauge micro-incision vitrectomy surgery is an effective sutureless surgery with favorable outcomes, in terms of vision, in patients with diabetic vitreous hemorrhage. The associated complications are few which can be easily managed.

Comparison of clinical outcome between 23-G and 25-G vitrectomy in diabetic patients

PURPOSE:

To compare the clinical outcomes and complications between 23-G and 25-G vitrectomy in patients with diabetic vitreous hemorrhage (VH).

MATERIALS AND METHODS:

A retrospective comparative study comprising 69 eyes (36 eyes in 23-G group and 33 eyes in 25-G group) of 65 patients who underwent vitrectomy with air tamponade for diabetic vitreous hemorrhage (VH) with at least 6 months of follow-up was conducted.

RESULTS:

There were no significant differences between the two groups in age, gender, bilaterality, type of diabetes, presence of hypertension, lens status, and previous argon laser photocoagulation state (P > 0.05). Best-corrected visual acuity (BCVA) of both groups at postoperative 1 month logarithm of the minimum angle of resolution (logMAR) (1.06 ± 0.99, 0.90 ± 0.96), 3 months logMAR (1.07 ± 0.93, 0.83 ± 0.85), and 6 months logMAR (1.03 ± 0.89, 0.83 ± 0.85) significantly improved from the preoperative BCVA logMAR (2.03 ± 0.83, 2.15 ± 0.99) for 23-G group, 25-G group, respectively (P < 0.0001). There was no significant difference in BCVA between the two groups preoperatively and at 1, 3, and 6 months postoperatively (P = 0.566, 0.506, 0.333, and 0.445, respectively), incidence of intraoperative wound suturing (21.4%, 15.2%), postoperative hypotony (0.0%, 0.0%), early postoperative VH (POVH) (11.1%, 15.2%), late POVH (5.6%, 0.0%), retinal detachment (2.8%, 6.1%), neovascular glaucoma (92.8%, 9.1%), and endophthalmitis (0.0%, 0.0%) for 23-G group, 25-G group, respectively (P > 0.05).

CONCLUSION:

25-G vitrectomy is as effective for PDR as 23-G vitrectomy.

Diabetic Retinopathy Clinical Practice Guidelines: Customized for Iranian Population

PURPOSE

To customize clinical practice guidelines (CPGs) for management of diabetic retinopathy (DR) in the Iranian population.

METHODS

Three DR CPGs (The Royal College of Ophthalmologists 2013, American Academy of Ophthalmology [Preferred Practice Pattern 2012], and Australian Diabetes Society 2008) were selected from the literature using the AGREE tool. Clinical questions were designed and summarized into four tables by the customization team. The components of the clinical questions along with pertinent recommendations extracted from the above-mentioned CPGs; details of the supporting articles and their levels of evidence; clinical recommendations considering clinical benefits, cost and side effects; and revised recommendations based on customization capability (applicability, acceptability, external validity) were recorded in 4 tables, respectively. Customized recommendations were sent to the faculty members of all universities across the country to score the recommendations from 1 to 9.

RESULTS

Agreed recommendations were accepted as the final recommendations while the non-agreed ones were approved after revision. Eventually, 29 customized recommendations under three major categories consisting of screening, diagnosis and treatment of DR were developed along with their sources and levels of evidence.

CONCLUSION

This customized CPGs for management of DR can be used to standardize the referral pathway, diagnosis and treatment of patients with diabetic retinopathy.

Influence of Siluron® insertion on model drug distribution in the simulated vitreous body

Biorelevant in vitro test systems may be helpful to understand the in vivo behaviour of modern intravitreal dosage forms such as implants and injections. The already presented Vitreous Model (VM) in combination with the Eye Movement System (EyeMoS) was used to simulate the situation after a vitrectomy in combination with Siluron® silicone oil (SO) insertion in vitro and to investigate the distribution of the model drug fluorescein sodium (FS) within the modified VM. The state after a vitrectomy was simulated in vitro by replacing half the volume of the gelled vitreous substitute by SO. Under consideration of simulated eye movements the position of SO towards the simulated vitreous body was examined. Furthermore, the influence of two different injection techniques was studied. On the one hand, FS was injected directly into the gel and on the other hand the injection was set through the gel in order to directly reach the SO. Independent of the injection technique, it was shown that the model drug distributed almost exclusively into the gel and not into the SO. This can be explained with the backflow of FS into the gel and the lack of solubility in the SO. Using the modified VM and EyeMoS, the in vitro characterization of drug release and distribution behaviour of intravitreal injections can be performed under consideration of a simulated vitrectomy.

Surgical treatment for diabetic vitreoretinal diseases: a review

Over the past four decades, advancements in surgical instrumentations and techniques have significantly improved the postoperative anatomical and visual outcomes of patients with various diabetic vitreoretinal diseases. In particular, surgical interventions for previously serious and untreatable blinding proliferative diabetic retinopathy can now be performed, with much better results. The advents of micro incisional vitrectomy system with better visualization system like binocular indirect ophthalmomicroscope and state-of-the-art instrumentation revolutionized the era of diabetic vitrectomy. High-speed vitrectors, finer instruments, chromo-assisted vitrectomy and use of anti-vascular endothelial growth factors not only change the paradigm but also help achieve much better outcome after diabetic vitrectomies. In this review, we will discuss and summarize the indications, surgical considerations, surgical techniques, potential complications and outcomes of vitreoretinal surgery for diabetic eye diseases.

Long-term results, prognostic factors and cataract surgery after diabetic vitrectomy: a 10-year follow-up study

PURPOSE

To report long-term results, prognostic factors and cataract surgery after diabetic vitrectomy.

METHODS

Retrospective review of patient files from a large diabetes centre between 1996 and 2010. Surgical history was obtained from the Danish National Patient Register. Follow-up intervals were 3 months and 1, 3, 5 and 10 years after surgery.

RESULTS

In total, 167 patients had diabetic vitrectomy indicated for non-clearing vitreous haemorrhage (47%) and tractional retinal detachment (53%). The proportion of patients with visual acuity ≥0.3 increased from 29% before surgery to 60% after 3 months (p < 0.001, chi-square test). Median visual acuity increased from 0.06 before surgery to 0.3 after 3 months (p < 0.001, paired signed-rank test) and 0.4 after 1 year (p = 0.009) before stabilizing. No significant long-term prognostic factors were identified for non-clearing vitreous haemorrhage patients. For tractional retinal detachment patients, use of silicone oil was associated with low vision (visual acuity<0.3) after 3 months and 1, 3 and 5 years (all odds ratios >4 and p-values ≤ 0.03, logistic regression). Of the 134 patients who were phakic after surgery, 43% and 29% were phakic after 5 and 10 years, respectively. Use of silicone oil increased the risk of cataract surgery (p = 0.009, log-rank test).

CONCLUSIONS

Most diabetic vitrectomy patients stand to gain visual acuity ≥0.3 after surgery and a stable long-term visual acuity after 1 year. The only consistent long-term predictor of low vision after surgery is use of silicone oil for endotamponade. About 2/3 of phakic patients will subsequently have cataract surgery the first 10 years after diabetic vitrectomy.

Intraocular surgery in a large diabetes patient population: risk factors and surgical results

The prevalence of diabetes is on the increase in developed countries. Accordingly, the prevention and treatment of vision-threatening diabetic eye complications is assuming greater importance. The overall aim of this thesis is to analyse risk factors for intraocular surgery in a large diabetes population and to report surgical results. The specific objectives are to (1) estimate the incidence of diabetic vitrectomy and analyse risk factors (Study I), (2) report long-term results, prognostic factors and incidence of cataract surgery after diabetic vitrectomy (Study II), (3) report results and prognostic factors after cataract surgery in diabetes patients (Study III) and (4) analyse risk factors for diabetic papillopathy with emphasis on metabolic control variability (Study IV). All studies are based on a close-to-complete national surgery register and a large, closely followed diabetic retinopathy screening population. Study I (cohort study, 3980 type 1 diabetes patients) illustrates that diabetic vitrectomy is rarely required in a diabetes patient population with varying degrees of diabetic retinopathy. The risk of reaching diabetic vitrectomy increases fourfold with poor metabolic control, defined as glycosylated haemoglobin A1c > 75 mmol/mol (~9%), which points to good metabolic control as an important preventive measure. Study II (cohort study, 167 diabetes patients) shows that most diabetic vitrectomy patients stand to gain visual acuity ≥0.3 after surgery. Visual acuity is stable after 1 year, and the stability is maintained through 10 years of follow-up. The use of silicone oil for endotamponade is a consistent long-term predictor of low vision after surgery. The risk of requiring cataract surgery after diabetic vitrectomy is substantial, and the risk increases if silicone oil is used. Study III (cohort study, 285 diabetes patients) shows, on the other hand, that diabetes patients can expect a significant improvement in visual acuity after cataract surgery, regardless of the degree of diabetic retinopathy. Poor preoperative visual acuity, a high degree of diabetic retinopathy and advanced age are predictors of a poor visual acuity after surgery. The risk of diabetic macular oedema after surgery is 4%. Finally, Study IV (case-control study, 2066 type 1 diabetes patients) demonstrates that diabetic papillopathy shares characteristics with diabetic retinopathy. The risk of experiencing diabetic papillopathy increases markedly with a drastic, recent reduction in glycosylated haemoglobin A1c and a small optic disc. This lends support to the theory that diabetic eye complications may occur in anatomically predisposed patients in response to metabolic control variability. Overall, results after intraocular surgery in diabetes patients are favourable. Surgery, however, is associated with costs to society, patient discomfort and risk of complications. This thesis provides an analysis of risk factors for intraocular surgery and identifies prognostic factors for visual acuity after surgery, which can be used for preventive purposes, surgical decision-making and patient counselling.

Perfluorocarbon liquid: its application in vitreoretinal surgery and related ocular inflammation

The application of perfluorocarbon liquids has been well acclaimed in vitreoretinal surgery. Its unique physical properties make it an ideal intraoperative tool to improve the efficiency and safety of surgical procedures in complicated cases. The main functions of perfluorocarbon liquids in vitreoretinal surgery include relocating and fixing the detached retina, displacing the subretinal and subchoroidal to fluid anteriorly, revealing proliferative vitreous retinopathy (PVR) for further maneuvers, protecting the macula from exposure to chemicals with potential toxicity, and assisting the removal of foreign body. The related clinical applications include retinal detachment with severe proliferative vitreoretinopathy, giant tear, diabetic retinopathy (DR), retinopathy of prematurity (ROP), and posterior dislocated crystalline and intraocular lenses. The application of perfluorocarbon liquids has been expended over the past fewer years. Several PFCLs related ocular inflammations have been observed in in vitro studies, animal studies, and clinical follow-up. The complete removal of PFCLs is recommended at the end of the surgery in most cases.

Surgical management of diabetic retinopathy

Surgery for late complications of proliferative diabetic retinopathy remains the cornerstone of management even in patients who have received optimal laser photocoagulation and medical therapy. With improvisation in the surgical techniques and development of micro-incision surgical techniques for vitrectomy, the indications for surgical intervention are expanding to include diabetic macular edema with a greater number of patients undergoing early intervention. This review describes the current indications, surgical techniques, adjunctive anti-vascular endothelial growth factor therapy, surgical outcomes, and postoperative complications of pars plana vitrectomy for proliferative diabetic retinopathy and macular edema.

Randomized clinical trial evaluating intravitreal ranibizumab or saline for vitreous hemorrhage from proliferative diabetic retinopathy

IMPORTANCE

Vascular endothelial growth factor plays a role in proliferative diabetic retinopathy (PDR). Intravitreal injection of saline has been shown potentially to lead to improved visual acuity compared with observation alone in eyes with vitreous hemorrhage. Therefore, it is important to determine if intravitreal anti-vascular endothelial growth factor can reduce vitrectomy rates (and risks associated with vitrectomy) compared with saline for vitreous hemorrhage from PDR that precludes placement or confirmation of complete panretinal photocoagulation.

OBJECTIVE

To evaluate intravitreal ranibizumab compared with intravitreal saline injections on vitrectomy rates for vitreous hemorrhage from PDR.

DESIGN

Phase 3, double-masked, randomized, multicenter clinical trial. Data reported were collected from June 2010 to March 2012 and include 16 weeks of follow-up.

SETTING

Community-based and academic-based ophthalmology practices specializing in retinal diseases.

PARTICIPANTS

Two hundred sixty-one eyes of 261 study participants, who were at least 18 years of age with type 1 or type 2 diabetes mellitus. Study eyes had vitreous hemorrhage from PDR precluding panretinal photocoagulation completion.

INTERVENTION

Eyes were randomly assigned to 0.5-mg intravitreal ranibizumab (n = 125) or intravitreal saline (n = 136) at baseline and 4 and 8 weeks.

MAIN OUTCOME MEASURE

Cumulative probability of vitrectomy within 16 weeks.

RESULTS

Cumulative probability of vitrectomy by 16 weeks was 12% with ranibizumab vs 17% with saline (difference, 4%; 95% CI, -4% to 13%) and of complete panretinal photocoagulation without vitrectomy by 16 weeks was 44% and 31%, respectively (P = .05). The mean (SD) visual acuity improvement from baseline to 12 weeks was 22 (23) letters and 16 (31) letters, respectively (P = .04). Recurrent vitreous hemorrhage occurred within 16 weeks in 6% and 17%, respectively (P = .01). One eye developed endophthalmitis after saline injection.

CONCLUSIONS AND RELEVANCE

Overall, the 16-week vitrectomy rates were lower than expected in both groups. This study suggests little likelihood of a clinically important difference between ranibizumab and saline on the rate of vitrectomy by 16 weeks in eyes with vitreous hemorrhage from PDR. Short-term secondary outcomes including visual acuity improvement, increased panretinal photocoagulation completion rates, and reduced recurrent vitreous hemorrhage rates suggest biologic activity of ranibizumab. Long-term benefits remain unknown. Whether vitrectomy rates after saline or ranibizumab injection are different than observation alone cannot be determined from this study.

TRIAL REGISTRATION

The study is listed on www.clinicaltrials.gov, under identifier NCT00996437 (website registration date October 14, 2009).

Review of therapeutic advances in diabetic retinopathy

Diabetic retinopathy is a common microvascular complication of prolonged diabetes. It is one of the leading causes of vision loss in working age adults and a significant source of morbidity. To reduce the incidence and severity of diabetic retinopathy, it is important to identify patients at risk and promptly implement intensive glycemic and hypertensive control. To date, there are many interventions that can limit moderate and severe vision loss in people with diabetes, including laser photocoagulation, vitrectomy surgery, and intravitreal pharmacological injections. This review aims to define the different stages of diabetic retinopathy and the important therapeutic advances developed to address the major causes of vision loss in each stage.

How to overcome retinal neuropathy: the fight against angiogenesis-related blindness

The retina consists of neuronal cells of high metabolic activity that are supplied by an abundant vasculature. It is a main theme of ophthalmologic research, because retinopathies are common causes of blindness in all age groups: age-related macular degeneration in the elderly, diabetic retinopathy in the middle aged, and retinopathy of prematurity and retinoblastoma in children. Interestingly, angiogenesis underlies the pathogenesis of all these diseases, and breakdown of the blood-retinal barrier is also thought to play an important role before and throughout the process of new vessel formation. However, so far, most treatments have targeted angiogenesis only, especially vascular endothelial growth factor. Consideration of the restoration of the blood-retinal barrier should be required. In this review, we discuss the clinical manifestation, pathogenesis, and current treatment options for angiogenesis-related blindness. In addition, because of the recent introduction of novel strategies, we describe pathogenesis-based treatment options to treat angiogenesis-related blindness.

Axial length and intraoperative posterior vitreous detachment as predictive factors for surgical outcomes of diabetic vitrectomy

AIMS

To evaluate the relationship of axial length (AXL), intraoperatively assessed posterior vitreous detachment (PVD) status, and surgical outcomes of diabetic vitrectomy.

METHODS

Retrospective, consecutive case series. Clinical records were reviewed for 115 eyes (50 males, 65 females) with more than a 6-month follow-up who underwent diabetic vitrectomy from a single surgeon. Thirty-three eyes had vitreous haemorrhage, 37 had tractional retinal detachment (TRD) threatening the macula, 43 had TRD involving the macula, and two had neovascular glaucoma. AXL was measured preoperatively by ultrasonography, and PVD status was classified intraoperatively: broad vitreo-retinal adhesion as no PVD, PVD at the macular area with attachment at the disc as incomplete PVD, and complete PVD.

RESULTS

Forty-four eyes had no PVD, 23 had incomplete PVD, and 48 had complete PVD. A majority of the no PVD group had macula off TRD (97.7%), whereas vitreous haemorrhage (68.7%) predominated in the complete PVD group. Longer AXLs were noted in the complete PVD group compared with the no PVD and incomplete PVD groups (ANOVA in three groups P=0.0001). Univariate analysis showed that AXL had an influence on anatomical success (P=0.02). Multiple logistic regression analysis yielded that PVD status is a significant predictor of the final best corrected visual acuity (BCVA)>20/100, and BCVA>20/40 (P=0.01, P=0.02).

CONCLUSIONS

Intraoperatively assessed PVD status is a prognostic factor for functional outcomes of diabetic vitrectomy. Shorter AXL was associated with lesser PVD. In eyes with a lack of PVD, careful timing and decision of surgery are mandatory.

Retinal Oximetry Using Intravitreal Illumination

PURPOSE

To demonstrate spectroscopic retinal oximetry measurements on arteries and veins in swine using intravitreal illumination. Retinal arterial and venous saturations are measured for a range of inspired O2 levels after pars plana vitrectomy.

METHODS

Pars plana vitrectomy and intravitreal manipulations were performed on two female American Yorkshire domestic swine. Light from a scanning monochromator was coupled into a fiberoptic intraocular illuminator inserted into the vitreous. The retinal vessels were illuminated obliquely, minimizing vessel glints. Multispectral images of the retinal vasculature were obtained as the swine's arterial blood oxygen saturation was decreased from 100% to 67% in decrements of approximately 10%. Retinal vessel spectra were used to calculate oxygen saturation in selected arteries and veins. Arterial oxygen saturations were calibrated using blood gas analysis on blood drawn from a Swan-Ganz catheter placed in the femoral artery.

RESULTS

Oblique illumination of retinal vessels using an intravitreal fiberoptic illuminator provided a substantial reduction in the central vessel glint usually seen in fundus images, thus simplifying the analysis of spectral data. The vessel shadows were displaced from the vessel image simplifying the light paths in the eye. Using a full spectral analysis simplified by the light path reductions, we calculated retinal vessel saturations. The reduction of glint allowed for increased accuracy in measuring retinal vessel spectral optical density. Abnormally low retinal venous oxygen saturations were observed shortly after pars plana vitrectomy.

CONCLUSIONS

Retinal oximetry using intravitreal illumination has been demonstrated. As a research tool, intravitreal illumination addresses several difficulties encountered when performing retinal oximetry with transcorneal illumination.

Kallikrein-kinin activation by altered vitreous pH: New perspectives for treatment and pathogenesis of diabetic macular edema?

Recently, Gao et al. published an experimental study based on the pathophysiology of diabetic macular edema in Nature Medicine (Nat Med. 2007 Feb;13(2):181-8). They found an increased amount of carbonic anhydrase in the vitreous, which causes a pH shift. This activates the kallikrein-kinin system and leads to increased retinal vascular permeability. In this comment the clinical implications of this article are discussed.

Antioxidant enzymes and diabetic retinopathy

The aim of this study was to discuss the serum copper (Cu), zinc (Zn), nitric oxide (NO), glutathione (GSH), advanced oxidation protein products (AOPP) levels, and superoxide dismutase (SOD) activities with diabetic retinopathy severity. Twenty-five patients with proliferative diabetic retinopathy (PDR group 1), 25 patients with nonproliferative diabetic retinopathy (NPDR group 2), and 25 nondiabetic controls (control group) were included in the study. Patients who had macrovascular complications of diabetes (coronary arterial disease, periferic vascular disease) were excluded. The major finding of our study was that we did not observe any differences between group 1 and 2, which we aimed to discuss the severity of diabetic retinopathy. As the levels of SOD and Zn were not different between the groups, statistically significant differences were observed for GSH, NO, and Cu levels when compared to control group. AOPP levels were statistically increased in group 1 compared to control group. It can be suggested that hyperglycemia in DM is associated with accelerated nonenzymatic glycation and oxidative stress.

Surgery for diabetic retinopathy

Surgery for diabetic retinopathy addresses late secondary complications of a primary microvascular disease. Since surgery is not a causative therapy, the functional outcome of surgery depends on the degree of retinal ischemia and may be disappointing even in technically and anatomically successfully operated eyes. Typical indications for vitrectomy are vitreous hemorrhage, tractional retinal detachment, combined tractional rhegmatogenous retinal detachment and tractive macular edema. More recently diffuse diabetic macular edema has been shown to improve after removal of an attached vitreous in several cases. Neovascular glaucoma requires aggressive surgical intervention to salvage the eye. Cataract surgery is commonly performed in eyes with diabetic retinopathy. It may however deteriorate diabetic eye disease. Vitreous surgery also has a potential for severe complications in diabetic eyes which can be ameliorated but not eliminated by proper surgical strategies and techniques. The decision for an intervention in diabetic eyes always requires a careful weighing of risks and benefits of surgery.