Intravitreal triamcinolone acetonide for treatment of intraocular oedematous and neovascular diseases

Preventive factors, diagnosis, and management of injection-related endophthalmitis: a literature review

BACKGROUND

Intravitreal medication injections represent the gold standard treatment for a variety of potentially blinding chorioretinal vascular diseases. Despite their excellent safety profile, they are associated with the feared complication of injection-related endophthalmitis (IRE). Though the overall incidence of IRE is low, due to the ever-increasing number of injections being performed, it is a complication that all retina specialists are likely to encounter. This article reviews various factors that could potentially influence the risk of IRE and discusses evidence-based strategies for management.

METHOD

PubMed was searched for keywords "intravitreal injection" and "endophthalmitis" from the period of 1995-2021. Relevant articles were reviewed and selected articles were analyzed with respect to the incidence, potential preventive factors, clinical presentation, microbial profile, management, and outcomes for IRE.

RESULTS

There is strong consensus supporting the use of povidone iodine topical antiseptic, eyelid retraction away from the injection site, and avoiding treatment of eyes with active surface or eyelid disease, but there is less agreement on the use of face masks versus "no-talking" policies and optimal anesthetic technique. Current evidence comparing tap and inject or early vitrectomy for treatment of IRE is inadequate to determine an optimal treatment strategy.

CONCLUSION

Intravitreal injections are sight saving, but even using established prophylactic measures there remains a small but real risk of infectious injection-related complications. Further investigations comparing tap and inject versus vitrectomy may help to establish optimal treatment, although the rarity of IRE makes designing adequately powered prospective trials a difficult task.

Steroid Treatment in Macular Edema: A Bibliometric Study and Visualization Analysis

The use of steroids to treat macular edema (ME) is a research hotspot in ophthalmology. We utilized CiteSpace and VOSviewer software to evaluate the Web of Science Core Collection publications and to build visualizing maps to describe the research progress in this topic. There were 3,252 publications for three decades during 1988–2021. The number of studies was low during the first 14 years but has risen consistently in the following two decades. The average publications per year were only 4.8 during 1988–2002, which jumped to 113 per year during 2003–2012, and 227 per year during 2013–2021. These publications came from 83 countries/regions, with the United States, Germany, and Italy leading positions. Most studies were published in Investigative Ophthalmology Visual Science, and Ophthalmology was the most cited journal. We found 9,993 authors, with Bandello F having the most publications and Jonas JB being the most frequently co-cited. According to our research, the most popular keyword is triamcinolone acetonide (TA). Macular edema, diabetic macular edema (DME), retinal vein occlusion (RVO), dexamethasone (DEX), fluocinolone acetonide (FA), and some other keywords were commonly studied in this field. In conclusion, the bibliometric analysis provides a comprehensive overview of steroid hotspots and developmental tendencies in the macular edema study. While anti-VEGF therapy is the first-line treatment for DME and RVO-induced macular edema, steroids implant is a valid option for these DME patients not responding to anti-VEGF therapy and non-DME patients with macular edema. Combined therapy with anti-VEGF and steroid agents is vital for future research.

Factors associated with the duration of action of dexamethasone intravitreal implants in diabetic macular edema patients

We designed this study to determine the association between the duration of action of intravitreal dexamethasone implants and aqueous humor biomarkers or optical coherence tomography (OCT) findings of diabetic macular edema (DME) patients. We measured the concentrations of interleukin (IL)-1β, -8, -10, -17; placental growth factor; and vascular endothelial growth factor in the aqueous humor, and identified the number of hyperreflective foci (HF), grades of ellipsoid zone disruptions, and baseline central subfield thicknesses (CSTs) using OCT of patients with DME. The average duration of action of dexamethasone implants was 4.32 ± 1.18 months. In multivariate linear regression analyses, the duration of action was associated with aqueous IL-8 levels and the number of HF (β = -0.016, p = 0.037 and β = -0.073, p = 0.035, respectively). Multivariate logistic regression showed that the number of HF (>10) was significantly associated with a shorter duration (<4 months) of action (odds ratio: 17.17, p = 0.010). The duration of action of intravitreal dexamethasone implants in DME patients was associated with the level of aqueous IL-8 and the number of HF using OCT. Specifically, higher number of HF in the OCT was associated with a shorter duration of action.

[Medicamental correction of pathomorphological changes of the ocular surface in patients with steroid therapy intolerance after photorefractive keratectomy]

INTRODUCTION

The problems of controlling inflammatory and proliferative response of the retina and correcting tear production in the post-operative period after photorefractive keratectomy (PRK) have not been fully solved yet. Patients intolerable to local steroids require an alternative. One drug that covers those needs is Cyclosporine 0.05%.

PURPOSE

To analyze clinical effectiveness of Restasis eye drops in solving inflammatory-degenerative response and tear production insufficiency (dry eye syndrome) for post-PRK patients with steroid eye drops intolerance accompanied with increasing intraocular pressure (IOP).

PATIENTS AND METHODS

Retrospective analysis of 14 myopic patients (28 eyes) was conducted; mean patient age was 25.9±6 years; myopia was (-)5.65±1.5 Diopters of spherical equivalent (SE); corneal-compensated IOP was 16.98±3.68 mm Hg before the surgery. All patients underwent excimer laser correction (PRK or Trans-PRK) with Schwind Amaris (SCHWIND eye-tech-solutions). After epithelization, all patients were prescribed 0.1% Dexamethasone solution 4 times a day (with decreasing dosing frequency) for 2 months, as well as local lubricants. The article also describes a separate clinical case of subepithelial fibroplasia that occurred post-PRK and was successfully stopped.

RESULTS

All patients had transitory IOP increase caused by local steroid therapy. Mean IOP at 1-month post-op was 20.5±7 mm Hg. At that point local steroids were replaced with 'Restasis' 0.05% (Cyclosporine) eye drops prescribed 2 times per day for 2 months. As the result, IOP values decreased to 16.2±3.21 mm Hg (without any additional therapy); at 6 months mean uncorrected visual acuity reached 0.98±0.05, best corrected visual acuity achieved 1.03±0.06 and SE was 0.04±0.12 Diopters.

CONCLUSION

Local Cyclosporine ('Restasis') is the method of choice for regulation of inflammatory and degenerative response and tear production insufficiency (dry eye syndrome) for post-PRK patients with intolerance to steroid eye drops.

Safety of high-dose intravitreal triamcinolone acetonide as low-cost alternative to anti-vascular endothelial growth factor agents in lower-middle-income countries

Purpose

The purpose of this study was to evaluate the safety of high-dose intravitreal triamcinolone acetonide (IVTA) as affordable low-cost alternative to anti-vascular endothelial growth factor (anti-vascular endothelial growth factor [anti-VEGF] agents) in lower-middle-income countries.

Patients and methods

This was a retrospective interventional non-comparative case series. The study recruited patients who received 20 mg IVTA for treating various retinal and optic nerve diseases over the past 5 years. Main outcome measure was assessment of complications secondary to high-dose IVTA. The crosstabs procedure was used to display the interaction between the variables tested. The ANOVA test was used to analyze the differences among group means.

Results

The study included 207 eyes of 168 patients. The main indication for high-dose IVTA were diabetic macular edema 64%, and macular edema secondary to retinal vein occlusion 19%. The mean follow-up period post-injection was 22 months. Mean number of injections was 1.3. Cataract developed in 54% of eyes. Glaucoma developed in 18.5% of eyes. Glaucoma surgery for intractable glaucoma attributed to high-dose IVTA was needed in 1% of eyes. Endophthalmitis and retinal detachment developed in one patient each.

Conclusion

High-dose IVTA is a safe and cost-effective alternative to anti-VEGF agents. Cataract formation and intraocular pressure rise do not pose major adverse effects when weighed against the risk of vision loss due to inability to afford anti-VEGF treatment.

Safety and efficacy of dexamethasone intravitreal implant for treatment of macular edema secondary to retinal vein occlusion in Chinese patients: randomized, sham-controlled, multicenter study

PURPOSE

The purpose of this study was to evaluate the safety and efficacy of dexamethasone intravitreal implant 0.7 mg (DEX) for treatment of macular edema associated with retinal vein occlusion (RVO).

METHODS

This study was a six-month, randomized, double-masked, sham-controlled, multicenter, phase 3 clinical trial with a 2-month open-label study extension. Patients with branch or central RVO received DEX (n = 129) or sham procedure (n = 130) in the study eye at baseline; all patients who met re-treatment criteria received DEX at month 6. Efficacy measures included Early Treatment Diabetic Retinopathy Study (ETDRS), best-corrected visual acuity (BCVA), and central retinal thickness (CRT) on optical coherence tomography.

RESULTS

Time to ≥15-letter BCVA improvement from baseline during the first 6 months (primary endpoint) was earlier with DEX than sham (p < 0.001). At month 2 (peak effect), the percentage of patients with ≥15-letter BCVA improvement from baseline was DEX: 35%, sham: 12%; mean BCVA change from baseline was DEX: +10.6 letters, sham: +1.7 letters; and mean CRT change from baseline was DEX: -407 μm, sham: -62 μm (all p < 0.001). Outcomes were better with DEX than sham in both branch and central RVO. The most common treatment-emergent adverse event was increased intraocular pressure (IOP). Increases in IOP generally were controlled with topical medication. Mean IOP normalized by month 4, and no patient required incisional glaucoma surgery.

CONCLUSIONS

DEX had a favorable safety profile and provided clinically significant benefit in a Chinese patient population with RVO. Visual and anatomic outcomes were improved with DEX relative to sham for 3-4 months after a single implant.

Retinal vascular injuries and intravitreal human embryonic stem cell-derived haemangioblasts

OBJECTIVE

To investigate whether intravitreally applied haemangioblasts (HB) derived from human embryonic stem cells (hESCs) are helpful for the repair of vascular damage caused in animals by an oxygen-induced retinopathy (OIR), by an induced diabetic retinopathy (DR) or by an induced retinal ischaemia with subsequent reperfusion.

METHODS

Human embryonic stem cell-derived HBs were transplanted intravitreally into C57BL/6J mice (OIR model), into male Wistar rats with an induced DR and into male Wistar rats undergoing induced retinal ischaemia with subsequent reperfusion. Control groups of animals received an intravitreal injection of endothelial cells (ECs) or phosphate-buffered saline (PBS). We examined the vasculature integrity in the mice with OIR, the blood-retina barrier in the rats with induced DR, and retinal thickness and retinal ganglion cell density in retina flat mounts of the rats with the retinal ischaemic-reperfusion retinopathy.

RESULTS

In the OIR model, the study group versus control groups showed a significantly (p < 0.001) smaller retinal avascular area [5.1 ± 2.7%;n = 18 animals versus 12.2 ± 2.8% (PBS group; n = 10 animals) and versus 11.8 ± 3.7% (EC group; n = 8 animals)] and less retinal neovascularization [6.3 ± 2.5%;n = 18 versus 15.2 ± 6.3% (n = 10; PBS group) and versus 15.8 ± 3.3% (n = 8; EC group)]. On retinal flat mounts, hESC-HBs were integrated into damaged retinal vessels and stained positive for PECAM (CD31) as EC marker. In the DR model, the study group versus the EC control group showed a significantly (p = 0.001) better blood-retina barrier function as measured at 2 days after the intravitreal injections [study group: 20.2 ± 12.8 μl/(g × hr); n = 6; versus EC control group: 52.9 ± 9.9 μl/(g × hr; n = 6)]. In the retinal ischaemia-reperfusion model, the groups did not differ significantly in retinal thickness and retinal ganglion cell density at 2, 5 and 7 days after baseline.

CONCLUSION

By integrating into damaged retinal vessels and differentiating into ECs, intravitreally administered hESC-HBs may have partially repaired a retinal vascular injury caused by OIR model and DR.

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.

Clearance of autophagy-associated dying retinal pigment epithelial cells - a possible source for inflammation in age-related macular degeneration

Retinal pigment epithelial (RPE) cells can undergo different forms of cell death, including autophagy-associated cell death during age-related macular degeneration (AMD). Failure of macrophages or dendritic cells (DCs) to engulf the different dying cells in the retina may result in the accumulation of debris and progression of AMD. ARPE-19 and primary human RPE cells undergo autophagy-associated cell death upon serum depletion and oxidative stress induced by hydrogen peroxide (H₂O₂). Autophagy was revealed by elevated light-chain-3 II (LC3-II) expression and electron microscopy, while autophagic flux was confirmed by blocking the autophago-lysosomal fusion using chloroquine (CQ) in these cells. The autophagy-associated dying RPE cells were engulfed by human macrophages, DCs and living RPE cells in an increasing and time-dependent manner. Inhibition of autophagy by 3-methyladenine (3-MA) decreased the engulfment of the autophagy-associated dying cells by macrophages, whereas sorting out the GFP-LC3-positive/autophagic cell population or treatment by the glucocorticoid triamcinolone (TC) enhanced it. Increased amounts of IL-6 and IL-8 were released when autophagy-associated dying RPEs were engulfed by macrophages. Our data suggest that cells undergoing autophagy-associated cell death engage in clearance mechanisms guided by professional and non-professional phagocytes, which is accompanied by inflammation as part of an in vitro modeling of AMD pathogenesis.

Intravitreal triamcinolone acetonide, retinal microglia and retinal ganglion cell apoptosis in the optic nerve crush model

PURPOSE

To evaluate the effect of intravitreal triamcinolone acetonide (TA) on the activation of retinal microglia cells (RMGCs) and survival of retinal ganglion cells (RGCs) in an optic nerve crush (ONC) model.

METHODS

Adult female Sprague-Dawley rats underwent a standardized ONC and either received an intravitreal injection of TA (TA group) or of phosphate-buffered saline (PBS, PBS group) in the right eyes. At 1, 3, 7, 14 and 28 days after the ONC, the animals were killed. The retinas were examined by immunohistochemistry, light microscopy, Western blot or retrograde labelling of RGCs by fluorogold injected into the superior colliculi.

RESULTS

The TA group as compared to the PBS control group showed a significantly (p < 0.0001) lower density of activated RMGCs, at 14 days [4.2 ± 1.6 versus 9.3 ± 2.2 cells/high-power microscopic field (HPF)] and at 28 days (2.3 ± 1.1 versus 4.4 ± 1.5 cells/HPF), and with a significantly lower expression of inflammatory factors. Central density of RGCs as stained by haematoxylin-eosin or by fluorogold was significantly (all p < 0.05) more reduced in the PBS group than in the TA group at days 14 and 28 after baseline. The survival rate (cell density in the study eye as compared to cell density in the contralateral unaffected eye) was significantly higher in the TA group than in the PBS group on days 14 (58% versus 45%; p = 0.003) and 28 (52% versus 41%; p = 0.022).

CONCLUSIONS

Intravitreal TA as compared to intravitreal PBS was associated with a lower density of activated RMGCs and a higher density of surviving RGCs in an ONC model.

Incidence, Risk Factors, and Timing of Elevated Intraocular Pressure After Intravitreal Triamcinolone Acetonide Injection for Macular Edema Secondary to Retinal Vein Occlusion: SCORE Study Report 15

IMPORTANCE

The Standard of Care vs Corticosteroid for Retinal Vein Occlusion (SCORE) Study showed that intravitreal triamcinolone acetonide (IVTA) is effective at reducing macular edema and improving visual acuity in participants with retinal vein occlusion. Secondary analysis of the incidence, risk factors, and timing of intraocular pressure (IOP) elevation occurring after IVTA provides guidance for clinical decision making and management of patients treated with IVTA.

OBJECTIVE

To investigate the incidence, risk factors, and time course of IOP elevation in participants in the SCORE Study.

DESIGN, SETTING, AND PARTICIPANTS

Secondary analysis conducted from August through December 2014 of a prospective, randomized clinical trial featuring an evaluable population conducted at 75 clinical sites. Six hundred eighty-two patients with macular edema secondary to retinal vein occlusion were enrolled in the study. The SCORE Study enrollment period ran from November 4, 2004, to February 29, 2008, with participant follow-up ending February 28, 2009.

INTERVENTIONS

Study participants were randomized to standard of care, 1 mg of IVTA, or 4 mg of IVTA therapy and followed up for a mean (SD) of 24.7 (10.3) months.

MAIN OUTCOMES AND MEASURES

Intraocular pressure elevation greater than 10 mm Hg from baseline.

RESULTS

Kaplan-Meier incidences of IOP elevation greater than 10 mm Hg from baseline at 36 months were 0.02 (95% CI, 0.01-0.06), 0.09 (95% CI, 0.05-0.14), and 0.45 (95% CI, 0.38-0.53) in the standard of care, 1-mg IVTA, and 4-mg IVTA groups, respectively. The rates of IOP-related events were higher for the 4-mg IVTA group compared with the other groups (P ≤ .001 for main outcome measure). Younger age, 4-mg IVTA vs 1-mg IVTA treatment, and higher baseline IOP were found to confer greater risk for IOP-related events (P < .05 for all). The median number of days from time of first injection to IOP elevation greater than 10 mm Hg from baseline was 34.0 and 52.5 days in participants treated with 1-mg and 4-mg IVTA, respectively.

CONCLUSIONS AND RELEVANCE

Intravitreal triamcinolone acetonide injection therapy, in particular the 4-mg dose, is associated with an increased risk for IOP elevation. The risk factors for an IOP-related event include higher treatment dose, younger age, and higher baseline IOP. Intraocular pressure-related events may take several months from the time of first IVTA injection to occur. Clinicians should be mindful of these risk factors when assessing the risks and benefits of IVTA therapy and also of the need for long-term follow-up of participants at risk for this complication.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00105027.

Intravitreal steroids versus observation for macular edema secondary to central retinal vein occlusion

BACKGROUND

Central retinal vein occlusion (CRVO) is a common retinal vascular abnormality associated with conditions such as hypertension, diabetes, glaucoma, and a wide variety of hematologic disorders. Macular edema (ME) represents an important vision-threatening complication of CRVO. Intravitreal steroids (IVS), such as triamcinolone acetonide, have been utilized to treat macular edema stemming from a variety of etiologies and may be a treatment option for CRVO-ME.

OBJECTIVES

To explore the effectiveness and safety of intravitreal steroids in the treatment of CRVO-ME.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (2014 Issue 10), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to November 2014), EMBASE (January 1980 to November 2014), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 13 November 2014. For all included primary studies, we used The Science Citation Index (3 December 2014) and manually reviewed reference lists to identify other possible relevant trials.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) that compared intravitreal steroids, of any dosage and duration of treatment of at least six months, with observation for the treatment of CRVO-ME.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened titles and abstracts identified from the electronic searches and assessed full-text articles from potentially eligible trials. Two review authors independently assessed trial characteristics, risk of bias, and extracted data from included trials. We contacted investigators of included trials for desired data not provided in the trial reports.

MAIN RESULTS

We included two RCTs that enrolled a total of 708 participants with CRVO-ME. SCORE compared triamcinolone acetonide intravitreal injections (n = 165) with observation (n = 72); GENEVA compared dexamethasone intravitreal implants (n = 290) with sham injections (n = 147). We observed characteristics indicative of high risk of bias due to incomplete outcome data in SCORE and selective outcome reporting in GENEVA. Loss to follow-up was high with 10% in the steroid groups and almost twice as much (17%) in the observation group. GENEVA enrolled participants with both branch and central retinal vein occlusion, but did not present subgroup data for the CRVO-ME population. A qualitative assessment of the results from GENEVA indicated that the dexamethasone implant was not associated with improvement in visual acuity after six months among participants with CRVO-ME. Although the SCORE investigators reported that participants treated with 1 mg (n = 82) or 4 mg (n = 83) triamcinolone intravitreal injections were five times more likely to have gained 15 letters or more in visual acuity compared with participants in the observation group (1 mg; risk ratio (RR): 5.27; 95% confidence interval (CI) 1.62 to 17.15; 4 mg RR 4.92; 95% CI 1.50 to 16.10) by the eighth-month follow-up examination, the average visual acuity decreased in all three groups. However, eyes treated with triamcinolone lost fewer letters than participants in the observation group at 8 months (1 mg mean difference (MD): 8.70 letters, 95% CI 1.86 to 15.54; 4 mg MD: 9.80 letters, 95% CI 3.32 to 16.28). A higher incidence of adverse events was noted with IVS therapy when compared with observation alone. As many as 20% to 35% of participants experienced an adverse event in the IVS groups compared with 8% of participants in the observation group of the SCORE study. The GENEVA investigators reported 63% in the treatment arm versus 43% in the observation arm experienced an adverse event. The most commonly encountered adverse events were elevated intraocular pressure, progression of cataracts, and retinal neovascularization. We graded the quality of evidence as low due to study limitations, imprecision of treatment estimates, and selective outcome reporting.

AUTHORS' CONCLUSIONS

The two RCTs reviewed herein provide insufficient evidence to determine the benefits of IVS for individuals with CRVO-ME. The improvement in visual acuity noted in the SCORE trial should be interpreted with caution as outcome data were missing for a large proportion of the observation group. Adverse events were observed more often with IVS treatment compared with observation/no treatment.

[Ocular hypertension after intravitreal steroid injections: Clinical update as of 2015]

Intravitreal injections are a therapeutic delivery method best suited to the treatment of retinal diseases. Recent years have been marked by the use of anti-VEGF agents as well as the arrival of sustained-release corticosteroid implants in France, replacing triamcinolone acetonide. A common complication of IVT steroids is secondary ocular hypertension (OHT) resulting from increased outflow resistance. This article summarizes current understanding. OHT induced by topical steroids has been described for 60 years. Intravitreal use also shows a temporary effect if the exposure is short, dose dependence, and varying incidence depending on the drug used. Sustained release formulations and discontinuing treatment have reduced the risk of induced OHT. Risk factors that induce OHT must be clearly identified prior to an injection. Most cases of OHT can be controlled medically, although differences exist between different drugs. In cases where it cannot be controlled, removal of the implant, selective laser trabeculoplasty, and filtration surgery can be discussed.

Vitreous incarceration after ranibizumab injection: an ultrasound biomicroscopy study

BACKGROUND AND OBJECTIVE

The aim of the study was to evaluate vitreous incarceration at the injection site using ultrasound biomicroscopy (UBM) after intravitreal injection of ranibizumab.

PATIENTS AND METHODS

The study included 39 eyes of 34 patients who underwent intravitreal injection of 0.05 mL of ranibizumab. UBM (HiScan; Optikon, Rome, Italy) with a 50 MHz probe was performed 1 day after surgery to determine the existence of vitreous incarceration at the injection site.

RESULTS

The mean patient age was 59.7 (± 10.1) years, and 58.9% were female. Vitreous incarceration into the pars plana site was detected in six eyes (15.3%) the day after intravitreal injection.

CONCLUSION

Vitreous incarceration at the injection site after intravitreal injection is thought to lead to a higher risk for complications such as infection, retinal breaks, retinal detachment, vitreous hemorrhage, and fibrovascular proliferation at the injection site. To understand the clinical importance of vitreous incarceration, further long-term prospective studies are necessary.

Comparison of the effects of intravitreal bevacizumab and triamcinolone acetonide in the treatment of macular edema secondary to central retinal vein occlusion

AIM

To compare the effects of intravitrealbevacizumab (IVB) and intravitreal triamcinolone acetonide (IVT) in the treatment of macular edema (ME) secondary to central retinal vein occlusion (CRVO).

MATERIALS AND METHODS

There were 20 patients treated with IVB (1.25 mg/0.05 mL) and 16 treated with IVT (4 mg/0.1 mL). The two groups were compared with regard to best-corrected visual acuity (BCVA), central macular thickness (CMT) on optical coherence tomography (OCT), slit-lamp biomicroscopy and fundus fluorescein angiography results, intraocular pressure (IOP), numbers of injections, and adverse events.

RESULTS

The mean follow-up times in the IVB and IVT groups were 17.45±8.1 months (range: 8-33 months) and 19.94±10.59 months (range: 6-40 months), respectively (P = 0.431). Visual acuity increased and CMT decreased significantly within both groups, but no differences were observed between the groups (P = 0.718). The percentages of patients with increased IOP and iatrogenic cataracts were significantly higher in the IVT group than in the IVB group.

CONCLUSIONS

Treatment with IVB and IVT both resulted in significant improvement in visual acuity and a decrease in CMT in patients with ME secondary to non-ischemic CRVO, with no difference between the two treatments. The incidence of adverse events, however, was significantly greater in the IVT group than in the IVB group. IVB may be preferred over IVT for the treatment of ME in patients with non-ischemic CRVO.

Three intravitreal bevacizumab versus two intravitreal triamcinolone injections in recent onset central retinal vein occlusion

PURPOSE

To evaluate the effects of repeated intravitreal injections of bevacizumab (IVB) versus triamcinolone acetonide (IVT) in the treatment of acute central retinal vein occlusion (CRVO).

METHODS

In this randomized clinical trial, 86 eyes with recent onset (<12 weeks) CRVO were assigned to two groups: IVB group (43 eyes) that received three monthly injections of 1.25 mg of IVB, and IVT group (43 eyes) that received two injections of 2 mg IVT 2 months apart. Outcomes were best-corrected visual acuity (BCVA), central macular thickness (CMT), and intraocular pressure (IOP) changes.

RESULTS

Mean BCVA improved significantly at 6 months in both groups; from 0.87 ± 0.49 to 0.41 ± 0.35 logMAR in IVB group, and from 0.81 ± 0.45 to 0.62 ± 0.48 logMAR in IVT group (p < 0.001). However, between-group differences reach a significant level at months 4 (p = 0.003) and 6 (p < 0.001) in favour of the IVB group. In terms of CMT reduction, the difference between the groups was statistically significant (p = 0.002) at month 6. Significant differences were noted more in the ischaemic cases in favour of the IVB group. Mean IOP rise was significantly higher in the IVT group at all visits.

CONCLUSIONS

Both 3-times monthly IVB injections and 2-times IVT injections could be effective in cases with recent onset CRVO up to 6 months. However, considering the better outcomes after IVB injections and the potential complications of IVT injections, we would recommend prescheduled repeated IVB injections for such cases. The observed favourable responses were more pronounced in the ischaemic types; nevertheless, this should be confirmed in larger studies.

Interventions for the treatment of uveitic macular edema: a systematic review and meta-analysis

Background

Uveitic macular edema is the major cause of reduced vision in eyes with uveitis.

Objectives

To assess the effectiveness of interventions in the treatment of uveitic macular edema.

Search strategy

Cochrane Central Register of Controlled Trials, Medline, and Embase. There were no language or data restrictions in the search for trials. The databases were last searched on December 1, 2011. Reference lists of included trials were searched. Archives of Ophthalmology, Ophthalmology, Retina, the British Journal of Ophthalmology, and the New England Journal of Medicine were searched for clinical trials and reviews.

Selection criteria

Participants of any age and sex with any type of uveitic macular edema were included. Early, chronic, refractory, or secondary uveitic macular edema were included. We included trials that compared any interventions of any dose and duration, including comparison with another treatment, sham treatment, or no treatment.

Data collection and analysis

Best-corrected visual acuity and central macular thickness were the primary outcome measures. Secondary outcome data including adverse effects were collected.

Conclusion

More results from randomized controlled trials with long follow-up periods are needed for interventions for uveitic macular edema to assist in determining the overall long-term benefit of different treatments. The only intervention with sufficiently robust randomized controlled trials for a meta-analysis was acetazolamide, which was shown to be ineffective in improving vision in eyes with uveitic macular edema, and is clinically now rarely used. Interventions showing promise in this disease include dexamethasone implants, immunomodulatory drugs and anti-vascular endothelial growth-factor agents. When macular edema has become refractory after multiple interventions, pars plana vitrectomy could be considered. The disease pathophysiology is uncertain and the course of disease unpredictable. As there are no clear guidelines from the literature, interventions should be tailored to the individual patient.

Downregulation of VEGF mRNA expression by triamcinolone acetonide acetate-loaded chitosan derivative nanoparticles in human retinal pigment epithelial cells

BACKGROUND

The purpose of this study was to investigate the downregulation of mRNA expression of vascular endothelial growth factor (VEGF) by triamcinolone acetonide acetate (TAA)-loaded chitosan nanoparticles in human retinal pigment epithelial cells.

METHODS

TAA-loaded deoxycholic acid-modified chitosan (TAA/DA-Chit) nanoparticles were prepared via a self-assembly mechanism, and their morphology and zeta potential were examined by transmission electron microscopy and zeta potential analysis, respectively. DA-Chit and TAA/DA-Chit nanoparticle toxicity was evaluated using a Cell Counting Kit-8 assay. The efficiency of cellular uptake was determined using fluorescein isothiocyanate-labeled DA-Chit nanoparticles, in place of TAA/DA-Chit nanoparticles, assessed by both inverted fluorescence microscopy and flow cytometry. Downregulation of VEGF mRNA expression by TAA/DA-Chit nanoparticles was further investigated by real-time reverse transcription polymerase chain reaction (RT-PCR) assay of the treated human retinal pigment epithelial cells.

RESULTS

TAA/DA-Chit nanoparticles were prepared with a TAA-loading capacity in the range of 12%-82%, which increased the water solubility of TAA from 0.3 mg/mL to 2.1 mg/mL. These nanoparticles showed oblate shapes 100-550 nm in size in transmission electron microscopic images and had positive zeta potentials. The Cell Counting Kit-8 assay indicated that the DA-Chit and TAA/DA-Chit nanoparticles had no toxicity and low toxicity, respectively, to human retinal pigment epithelial cells. Fluorescein isothiocyanate-labeled DA-Chit nanoparticle uptake by human retinal pigment epithelial cells was confirmed by inverted fluorescence microscopy and flow cytometry. Real-time RT-PCR assay showed that the VEGF mRNA level decreased after incubation of human retinal pigment epithelial cells with TAA/DA-Chit nanoparticles.

CONCLUSION

TAA/DA-Chit nanoparticles had a downregulating effect on VEGF mRNA expression in human retinal pigment epithelial cells and low cytotoxicity, which might be beneficial characteristics for the development of future treatment for diabetic retinopathy.

Ultrasound biomicroscopy study of vitreous incarceration subsequent to intravitreal injections

OBJECTIVE

To study the existence of vitreous incarceration by ultrasound biomicroscopy (UBM) at the pars plana after direct intravitreal injection of triamcinolone acetonide ± bevacizumab without anterior chamber paracentesis.

DESIGN

Interventional case series.

PARTICIPANTS

Patients undergoing intravitreal injection of triamcinolone acetonide with or without intravitreal bevacizumab.

METHODS

In 21 eyes, the existence of vitreous incarceration at the pars plana site of intravitreal injection of 0.05 mL of drug was studied by UBM (50 MHz probe of the VUmax, Sonomed, NY), the day after surgery, by 1 technician. The reason for injection was diabetic retinopathy in 12 (57.1%) eyes; age-related macular degeneration in 6 (28.6%) eyes; branch retinal vein occlusion in 2 (9.5%) eyes; and choroiditis in 1 eye (4.8%). In 1 eye, only triamcinolone acetonide was injected, and in the other eyes, bevacizumab mixed with triamcinolone acetonide was injected.

RESULTS

We studied 21 eyes in 13 patients. Of the subjects, 61.5% were male. The mean age of the patients was 62.2 years. On the day after intravitreal injection of the drug, vitreous incarceration into the pars plana site was detected by UBM in 42.9% of the eyes.

CONCLUSION

Vitreous incarceration exists after intravitreal injection of drug, but its clinical importance is still unknown. Further long-term prospective studies are recommended.

An Update on Intravitreal Injections for Macular Diseases: Friend or Foe?

The purpose of this article is to review the role of intravitreal injections of medications in the treatment of the two common macular diseases, macular edema and age related macular degeneration (AMD). We perform literature search by search engine Pubmed till May 2011, using keywords 'intravitreal injections', 'age-related macular degeneration' and 'macular edema' to retrieve relevant review articles and original papers. To conclude, with advance in technology, intravitreal injections of medications may have become an integral part of our ability to treat a wide range of macular diseases. The use of ranibizumab, pegaptanib in the treatment of neovascular AMD and TA in the treatment of various causes of macular edema have shown promising results in a number of prospective randomized controlled trials, with low risk of complications reported.

Intravitreal cell-based production of glucagon-like peptide-1

BACKGROUND

To examine the efficacy and safety of an intravitreal cell-based production of glucagon-like peptide-1 (GLP-1) by intravitreally implanted and encapsulated cells.

METHODS

The experimental study included 12 Sprague-Dawley rats. Four cell beads with a diameter of 600 μm were intravitreally implanted. Each bead contained 3,000 GLP-1-secreting cells, which were encapsulated by a barium cross-linked sodium alginate matrix. At baseline and at each of the follow-up examinations at Day 3, Day 7, and Day 14, 4, 3, 3, and 2 animals, respectively, were killed. The concentration of active GLP-1 in the vitreous body samples was determined by enzyme-linked immunosorbent assay. The retinas were histologically examined.

RESULTS

The active GLP-1 concentration in the vitreous samples increased significantly after baseline (<5 pM) to a peak at Day 3 (287 ± 196 pM) and at Day 7 (238 ± 55 pM), before it decreased at Day 14 (70 ± 8 pM). The histologic examinations did not show signs of apoptosis or tissue destruction.

CONCLUSION

The intravitreal application of beads containing alginate-encapsulated cells producing GLP-1 resulted in an intraocular production of GLP-1 with a significant increase in the intraocular GLP-1 concentration, without observed cytotoxic effects. An intravitreal cell-based drug therapy with GLP-1 appears feasible.

Development of ocular hypertension and persistent glaucoma after intravitreal injection of triamcinolone

Purpose

This study evaluates intraocular pressure (IOP) elevation secondary to intravitreal injection of triamcinolone acetonide (IVTA) and discusses its management.

Methods

The records of 175 patients who underwent IVTA treatment and regular eye examinations in the period 2003–2006 were reviewed. One hundred and twenty-two of these patients were included in the study, of which 147 eyes that received IVTA (4 mg/0.1 ml) were followed for at least 9 months. Mean IOPs observed after IVTA injection as well as IOP elevations defined as moderate (≥5 mm Hg), important (≥10 mm Hg) and severe (>25 mm Hg) during the follow-up period were evaluated and compared statistically.

Results

Overall, the mean IOPs following IVTA injection were statistically significantly higher than the preinjection IOP (15.8 ± 2.6), after the first hour (17.7 ± 2.9), the first week (18.7 ± 4.1), the first month (19.6 ± 6.2), the second month (19.1 ± 6.1), the third month (18.0 ± 4.1), the sixth month (17.3 ± 4.0), and the ninth month (17.0 ± 2.7), but not after the first day (16.3 ± 7.6). Important IOP elevations were observed mostly in the first (17.7%) and second months (10.2%). In 40 (27.7%) eyes, topical antiglaucomatous therapy was needed and 7 later required surgical intervention to lower the IOP. Of the remaining 33 eyes, topical treatment was continued in 14 (9.5%) because of IOPs ≥20 mm Hg.

Conclusion

The persistence of IOP elevation beyond the IVTA clearance period and the development of intractable secondary glaucoma requiring surgical intervention substantiate the need for careful consideration of IVTA indication and follow-up.

Neuroprotective effect of intravitreal cell-based glucagon-like peptide-1 production in the optic nerve crush model

PURPOSE

To examine the effect of intraocularly produced glucagon-like peptide-1 (GLP-1) on the survival rate of retinal ganglion cells in an optic nerve crush model.

METHODS

Forty-one Sprague--Dawley rats were divided into a study group (21 animals) in which 4 beads with 3000 genetically modified cells to produce GLP-1 were intravitreally implanted into the right eye; a saline control group (n = 12) with intravitreal saline injection; and a GLP-1 negative bead control group (n = 8) in which 4 beads with 3000 cells without GLP-1 production were intravitreally implanted. The right optic nerves of all animals were crushed in a standardized manner. After labeling the retinal ganglion cells by injecting 3% fluorogold into the superior colliculus, the animals were sacrificed, and the ganglion cells were counted on retinal flat mounts.

RESULTS

The retinal ganglion cell density of the right eyes was significantly higher in the study group (median: 2081 cells/mm(2) ; range: 1182-2953 cells/mm(2) ) than in the GLP-1 bead negative control group (median: 1328 cells/mm(2) ; range: 1007-2068 cells/mm(2) ; p = 0.002) and than in the saline control group (median: 1777 cells/mm(2) ; range: 1000-2405 cells/mm(2) ; p = 0.07). Correspondingly, the survival rate (ratio of retinal ganglion cell density of right eye/left eye) was significantly higher in the study group (median: 0.72; range: 0.40-1.04) than in the GLP-1 bead negative control group (median: 0.44; range: 0.36-0.68; p = 0.003) and than in the saline control group (median: 0.56; range: 0.36-0.89; p = 0.03).

CONCLUSION

Glucagon-like peptide-1 produced by intravitreally implanted cell beads was associated with a higher survival rate of retinal ganglion cells after an experimental optic nerve crush in rats.

Intravitreal ranibizumab (Lucentis) for treatment of central retinal vein occlusion: a prospective study

BACKGROUND/PURPOSE

To evaluate the effect of individualized repeated intravitreal injections of ranibizumab (Lucentis) on visual acuity (VA) and central foveal thickness (CFT) for central retinal vein occlusion (CRVO)-induced macular edema.

METHODS

Our study was a prospective interventional case series. Twelve eyes of 12 consecutive patients diagnosed with CRVO-related macular edema (nine perfused, three ischemic CRVO) treated with repeated (when CFT was >220 microm) intravitreal injections of ranibizumab as a monotherapy within 3 months of onset were evaluated. Optical coherence tomography (OCT) and fluorescein angiography (FA) were performed monthly and every 3 months respectively. Changes in VA (ETDRS) and CFT were analyzed using the student's paired t-test.

RESULTS

The mean time from diagnosis until injection was 80 days (2.7 months; range, 63-90 days) and the follow-up time was 12 months. In total, 89 injections were performed (mean 7.4). The mean CFT improved from 480 +/- 166 microm at baseline to 230 +/- 33 microm (P < 0.001) at the end of the follow-up. During the same period, of the 12 eyes, eight demonstrated improved VA (>0.3 LogMAR change, >15 letters), three stable VA and one worse VA as compared to baseline. None of the nine patients with perfused CRVO were converted to ischemic at 12 months, and one of the three eyes with ischemic CRVO developed iris neovascularization despite two ranibizumab injections. No ocular or systemic side-effects were noted.

CONCLUSION

Individualized repeated intravitreal injections of ranibizumab have shown promising results in VA improvement and decrease in CFT in patients with macular edema associated with CRVO. Further studies are needed in order to elucidate the role of intravitreal lucentis in the ischemic form of CRVO, and its efficacy in preventing conversion from the perfused to the ischemic form of the disease.

Diabetic macular edema

A variety of treatment options are available for the treatment of diabetic macular edema. They include laser photocoagulation, anti-VEGF drugs, intravitreal steroids, and vitrectomy with or without release of vitreoretinal traction. A full understanding of the physiological mechanisms of these treatment modalities allows sensible combination of treatment options. Retinal photocoagulation has repeatedly been shown to improve retinal oxygenation, as does vitrectomy. Oxygen naturally reduces VEGF production and thereby decreases leakage of plasma proteins from capillaries into the tissue. In addition, vitrectomy allows faster clearance of cytokines, such as VEGF, from the retina into the vitreous cavity. The VEGF-lowering effect of photocoagulation and vitrectomy can be augmented with anti-VEGF drugs and corticosteroids reduce the effect of VEGF on capillary permeability. Starling's law explains vasogenic edema, which is controlled by osmotic and hydrostatic gradients between vessel and tissue. It explains how VEGF-induced vascular permeability causes plasma protein to leak into the tissue interstitial space, thus decreasing the osmotic pressure gradient between vessel and tissue, resulting in water accumulation, i.e. edema. This is reversed by reducing VEGF production, which is achieved with laser treatment; or by removing VEGF with antibodies or vitrectomy; or by reducing the permeability effect with steroids. At the same time, Starling's law takes into account hemodynamic changes that affect the hydrostatic gradient. High arterial blood pressure and hypoxic vasodilatation increase the hydrostatic pressure in the microcirculation, which increases water flux from vessel to tissue and induce edema. Treatment of arterial hypertension or reversal of retinal hypoxia with laser reverses this pathophysiology and reduces edema. Newton's third law explains, that vitreoretinal traction decreases hydrostatic tissue pressure in the retina, increases the pressure gradient between vessel and tissue, and stimulates water fluxes from vessel into tissue, leading to edema. Release of vitreoretinal traction reverses this mechanism and reduces edema.

Effects of repeated injection of intravitreal triamcinolone on macular oedema in central retinal vein occlusion

PURPOSE

To investigate the effectiveness of repeated injections of intravitreal triamcinolone acetonide (IVTA) in the treatment of macular oedema caused by central retinal vein occlusion (CRVO).

METHODS

Seventeen pseudophakic or aphakic eyes of 17 patients (10 male, seven female) with macular oedema caused by CRVO received a repeat injection of 4 mg IVTA, 16 weeks after the first injection of the same dose. The examination included measurements of best-corrected visual acuity (BCVA) for distance and central foveal thickness (CFT) by optical coherence tomography (OCT), preoperatively and 1, 2, 3 and 4 months postoperatively. The values were compared by paired-t test. Side-effects were monitored.

RESULTS

BCVA and CFT were not significantly different before initial and repeat injections. Transient improvements of BCVA and CFT were achieved after both injections. At the end of follow-up, BCVA and CFT were significantly different compared to pre-injection values in the same group (P = 0.032, 0.049 in the initial-injection group and P = 0.001, 0.008 in the repeat-injection group, respectively). However, compared to the initial injection, BCVA measurements were significantly worse at each time-point (P = 0.043, 0.011, 0.010 and 0.012, respectively) after the repeat injection, as were CFT at 1, 2 and 3 months post-injection (P = 0.040, 0.015 and 0.025, respectively). The achieved maximum mean intraocular pressures were 20.00 [standard deviation (SD) 2.06] mmHg and 18.56 (SD 3.65) mmHg after the first and repeat injections, respectively. These values were not significantly different (P = 0.467). No other significant adverse events were noted during the study.

CONCLUSION

A repeat injection of 4 mg IVTA may not be as effective as an initial injection for the treatment of macular oedema caused by CRVO.

Ultrasonographic pictures of intravitreal triamcinolone acetonide

PURPOSE

To evaluate ultrasonographic pictures of intravitreal triamcinolone acetonide (IVTA).

METHODS

Twenty-eight eyes from 28 patients who needed intravitreal injection of triamcinolone acetonide (4 mg/0.1 mL) were included in this study. A baseline ocular B-scan ultrasound examination was performed in all eyes before IVTA injection. Subsequent examinations were scheduled about 1 hour, 1 day, and 1 week after the injection and thereafter weekly up to complete sonographic disappearance of triamcinolone acetonide. Ultrasonographic pictures of IVTA and disappearance time of the medication were evaluated.

RESULTS

In all the eyes, IVTA was seen as multiple inhomogeneous markedly hyperechoic areas with various size and shape and nonuniform distribution through the vitreous cavity. Common pictures included localized bright hyper-reflective area, diffuse bright point-like echo sources, membranous surfaces, and subhyaloid opacities. IVTA deposited along acoustic interfaces and changed their ultrasonographic characteristics. IVTA facilitated visualization of posterior vitreous surface in seven patients. Opacities due to IVTA gradually cleared over a 3- to 7-week period.

CONCLUSIONS

The findings indicate that IVTA has a bright hyper-reflective ultrasonic image and should be considered as a differential diagnosis for vitreous opacity. IVTA can change the ultrasonographic pattern of the vitreous cavity and highlight membranous surfaces.

Photodynamic therapy with intravitreal application of triamcinolone acetonide in age-related macular degeneration: functional results in 54 patients

PURPOSE

This study aimed to investigate the functional results, efficacy and complications after photodynamic therapy (PDT) combined with intravitreal triamcinolone acetonide injection (IVTA) in patients with choroidal neovascularization (CNV) caused by age-related macular degeneration (AMD).

METHODS

A retrospective analysis of clinical data for 54 patients with CNV resulting from AMD was carried out. All patients had a follow-up of 12 months. The patients were treated with standardized PDT and IVTA (4 mg) as a first-line treatment or following PDT failure. Visual acuity (VA), greatest linear diameter (GLD) of the CNV and foveal thickness were evaluated.

RESULTS

Mean VA at baseline was 0.8 logMAR (0.4-1.4). After 12 months VA improved (> 2 lines) in 20.4% of patients and stabilized (+/- 2 lines) in 64.8%. There was no statistical significance in VA outcome between patients undergoing first-line treatment and patients with PDT failure; however, fewer PDT treatments were required to stop CNV activity in patients undergoing first-line treatment. At 12 months, a reduction in foveal thickness was seen in 67.7% of patients and a reduction in CNV GLD in 32.7%. Complications occurred in 22% of patients and included a transient rise in intraocular pressure, cataract and sterile hypopyon.

CONCLUSIONS

Our analysis shows that fewer PDT treatments were required to stop CNV activity when triamcinolone was used as first-line treatment. We can thus conclude that PDT combines synergistically with IVTA and the combination may lead to a cost reduction compared with PDT therapy alone. The overall complication rate of 22% is high and must be compared with complication rates caused by new intravitreal anti-VEGF (vascular endothelial growth factor) drugs in combination with PDT.

Intravitreal steroids versus observation for macular edema secondary to central retinal vein occlusion

BACKGROUND

Central retinal vein occlusion (CRVO) is a common retinal vascular abnormality associated with conditions such as hypertension, diabetes, glaucoma, and a wide variety of hematologic disorders. Macular edema (ME) represents an important vision-threatening complication of CRVO. There is no proven treatment; laser photocoagulation is not effective in treating cystoid macular edema secondary to CRVO. Intravitreal steroids, such as triamcinolone acetonide, have been utilized to treat macular edema stemming from a variety of etiologies and may represent a treatment option for CRVO-ME.

OBJECTIVES

The objective of this review was to explore the effectiveness and safety of intravitreal steroids in the treatment of CRVO-ME.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 4, 2008), MEDLINE (January 1950 to November 2008) and EMBASE (January 1980 to November 2008). There were no language or date restrictions in the search for trials. The electronic databases were last searched on 5 November 2008. For all included primary studies, we used The Science Citation Index and manually reviewed reference lists to identify other possible relevant trials. We contacted researchers in the field, currently working on a randomized controlled trial (RCT) on this topic (The Standard Care versus Corticosteroid for Retinal Vein Occlusion - SCORE study), for information on additional current, past, or unpublished trials.

SELECTION CRITERIA

We considered RCTs that compared intravitreal steroids of any dosage/duration to observation in the treatment of CRVO-ME for inclusion in this review. We focused on studies that included individuals of any age or gender with unilateral or bilateral disease, with a minimum of six months follow up. Secondarily we considered non-randomized studies with the same criteria for description of evidence, however we did not conduct a separate electronic search for finding all non-randomized studies.

DATA COLLECTION AND ANALYSIS

We found no RCTs that met the inclusion criteria after independent and duplicate review of the search results.

MAIN RESULTS

We found no relevant RCTs and therefore performed no meta-analysis. Evidence from non-randomized studies is reported in this review.

AUTHORS' CONCLUSIONS

There is inadequate evidence for the use of intravitreal steroids for CRVO-ME due to a paucity of RCTs and well-designed observational studies on the topic; therefore, it is still an experimental procedure.

Physiology of vitreous surgery

Vitreous surgery has various physiological and clinical consequences, both beneficial and harmful. Vitrectomy reduces the risk of retinal neovascularization, while increasing the risk of iris neovascularization, reduces macular edema and stimulates cataract formation. These clinical consequences may be understood with the help of classical laws of physics and physiology. The laws of Fick, Stokes-Einstein and Hagen-Poiseuille state that molecular transport by diffusion or convection is inversely related to the viscosity of the medium. When the vitreous gel is replaced with less viscous saline, the transport of all molecules, including oxygen and cytokines, is facilitated. Oxygen transport to ischemic retinal areas is improved, as is clearance of VEGF and other cytokines from these areas, thus reducing edema and neovascularization. At the same time, oxygen is transported faster down a concentration gradient from the anterior to the posterior segment, while VEGF moves in the opposite direction, making the anterior segment less oxygenated and with more VEGF, stimulating iris neovascularization. Silicone oil is the exception that proves the rule: it is more viscous than vitreous humour, re-establishes the transport barrier to oxygen and VEGF, and reduces the risk for iris neovascularization in the vitrectomized-lentectomized eye. Modern vitreous surgery involves a variety of treatment options in addition to vitrectomy itself, such as photocoagulation, anti-VEGF drugs, intravitreal steroids and release of vitreoretinal traction. A full understanding of these treatment modalities allows sensible combination of treatment options. Retinal photocoagulation has repeatedly been shown to improve retinal oxygenation, as does vitrectomy. Oxygen naturally reduces VEGF production and improves retinal hemodynamics. The VEGF-lowering effect of photocoagulation and vitrectomy can be augmented with anti-VEGF drugs and the permeability effect of VEGF reduced with corticosteroids. Starling's law explains vasogenic edema, which is controlled by osmotic and hydrostatic gradients between vessel and tissue. It explains the effect of VEGF-induced vascular permeability changes on plasma protein leakage and the osmotic gradient between vessel and tissue. At the same time, it takes into account hemodynamic changes that affect the hydrostatic gradient. This includes the influence of arterial blood pressure, and the effect oxygen (laser treatment) has in constricting retinal arterioles, increasing their resistance, and thus reducing the hydrostatic pressure in the microcirculation. Reduced capillary hydrostatic pressure and increased osmotic gradient reduce water fluxes from vessel to tissue and reduce edema. Finally, Newton's third law explains that vitreoretinal traction decreases hydrostatic tissue pressure in the retina, increases the pressure gradient between vessel and tissue, and stimulates water fluxes from vessel into tissue, leading to edema.