Diabetic eye disease, particularly diabetic retinopathy (DR), remains one of the most preventable yet persistent causes of vision loss among working-age adults globally. As the prevalence of diabetes continues to rise, healthcare systems face mounting pressure to deliver treatments that are not only clinically effective but also economically sustainable. Monotherapy with anti–vascular endothelial growth factor (VEGF) agents has become the standard of care for diabetic macular edema (DME) and proliferative diabetic retinopathy (PDR). However, many patients require frequent injections, and a significant subset demonstrates an incomplete response. This has driven interest in dual therapy—combining two treatment modalities—to improve outcomes and potentially reduce the overall treatment burden. Evaluating the cost-benefit ratio of this approach demands a careful analysis of clinical evidence, economic modeling, and patient-centric factors. This article provides an in-depth examination of the long-term value proposition of dual therapy in diabetic eye disease management.

Understanding Diabetic Eye Disease: Pathophysiology and Disease Burden

Diabetic retinopathy is a microvascular complication of diabetes mellitus that damages retinal capillaries, leading to ischemia, hemorrhage, and macular edema. The condition progresses from mild nonproliferative DR (NPDR) to severe NPDR and ultimately PDR, characterized by neovascularization. Diabetic macular edema, a common cause of vision loss, can occur at any stage. The disease burden is substantial: according to the International Diabetes Federation, approximately one in three people with diabetes has some form of DR, and it accounts for roughly 2.6% of global blindness.

Beyond vision loss, DR imposes significant economic costs—direct medical expenses for treatment, indirect costs from lost productivity, and intangible costs related to quality of life. The chronic nature of the disease means that patients often require lifelong monitoring and repeated interventions. Therefore, any therapeutic strategy that can stabilize retinopathy with fewer visits and lower complication rates has the potential to deliver meaningful value.

Standard Treatment Modalities: Monotherapy Landscape

The current armamentarium for managing DR and DME includes several well-established monotherapies:

  • Anti-VEGF injections: Agents such as ranibizumab (Lucentis), aflibercept (Eylea), bevacizumab (Avastin), and the newer faricimab (Vabysmo) inhibit VEGF, reducing vascular permeability and neovascularization. They are first-line for center-involving DME and often used for PDR.
  • Focal/grid laser photocoagulation: Although less common in the anti-VEGF era, laser remains useful for peripheral ischemia in PDR and for non–center-involving DME.
  • Corticosteroid implants: Dexamethasone (Ozurdex) and fluocinolone acetonide (Iluvien) provide sustained release, targeting inflammatory pathways and VEGF-independent edema. They are particularly beneficial for chronic DME or patients resistant to anti-VEGF.
  • Panretinal photocoagulation (PRP): The traditional treatment for PDR, now often deferred or combined with anti-VEGF to reduce neovascularization and prevent vitreous hemorrhage.

Despite their efficacy, monotherapy has limitations. Many patients require monthly or bimonthly anti-VEGF injections for years. Approximately 30–40% of DME eyes show incomplete resolution with anti-VEGF alone. Corticosteroids carry risks of cataract progression and intraocular pressure elevation. Laser can cause permanent scotomas and may not prevent recurrence. These shortcomings have motivated exploration of combination strategies.

What Is Dual Therapy? Rationale and Key Combinations

Dual therapy in diabetic eye disease refers to the concurrent or sequential use of two distinct therapeutic mechanisms to achieve synergistic or additive effects. The primary rationales are:

  • Enhanced efficacy: Targeting multiple pathogenic pathways (e.g., VEGF and inflammation) may overcome resistance and improve anatomical and functional outcomes.
  • Extended durability: Combining a long-acting agent with a fast-acting one may reduce injection frequency, easing the treatment burden.
  • Reduced side effects: Lowering the dose or frequency of each agent can potentially minimize toxicities while maintaining effect.

The most studied dual therapy approaches include:

Anti-VEGF Plus Corticosteroid

Combining an anti-VEGF injection with an intravitreal corticosteroid implant or injection targets both VEGF-driven neovascularization and inflammation-mediated edema. Several trials have evaluated this combination for DME. For example, the Protocol U study (DRCR.net) showed that adding intravitreal dexamethasone to ranibizumab improved anatomical outcomes in persistent DME but did not consistently achieve superior visual acuity gains over anti-VEGF monotherapy at one year. However, subgroup analyses suggested benefits for eyes with pseudophakia or significant intraretinal fluid. More recent evidence from the PHOTON trial for aflibercept 8 mg (which is a single-agent high-dose approach) has complicated the picture, but dual therapy remains an option for refractory cases.

Anti-VEGF Plus Laser

Combining anti-VEGF injections with focal/grid laser or PRP is another common dual approach. For DME, studies like the DRCR.net Protocol I found that ranibizumab plus prompt laser did not produce better visual outcomes than ranibizumab alone, but the combination reduced the number of injections needed. For PDR, the Protocol S trial showed that ranibizumab alone was noninferior to PRP for visual acuity, but combination therapy (PRP plus anti-VEGF) is sometimes used for aggressive neovascularization or to avoid extensive laser scars.

Sequential Dual Therapy (Transition from One Agent to Another)

In clinical practice, many patients start on anti-VEGF monotherapy and then receive a corticosteroid implant after insufficient response. This sequential dual therapy—often termed "rescue therapy"—is a pragmatic approach that avoids upfront combination costs. Its cost-benefit profile differs from planned concurrent therapy.

Emerging Combinations: Anti-VEGF Plus Anti-Angiopoietin

The approval of faricimab, a bispecific antibody targeting both VEGF-A and Ang-2, represents a novel form of dual pharmacological therapy in a single molecule. It blurs the line between monotherapy and dual therapy because it combines two mechanisms in one injection. Early trials suggest superior durability, with many patients able to extend dosing to every 16 weeks. This may shift the cost-benefit analysis considerably, as it reduces injection frequency without the risks of separate agents.

Evaluating the Cost-Benefit Ratio: A Multidimensional Framework

Assessing the cost-benefit ratio of dual therapy requires moving beyond simple drug cost comparisons. A comprehensive evaluation should incorporate:

  • Direct medical costs: Drug acquisition, supplies (syringes, operating room time if implant), physician fees, imaging visits, and management of complications (e.g., cataract surgery, glaucoma medications).
  • Indirect costs: Patient travel time, lost work productivity, caregiver burden.
  • Clinical effectiveness: Visual acuity gains, retinal thickness reduction, time to disease progression, need for rescue therapy, rate of vitreous hemorrhage or tractional retinal detachment.
  • Safety profile: Rates of endophthalmitis, inflammation, cataract, glaucoma, and systemic adverse events (e.g., stroke, myocardial infarction with anti-VEGF).
  • Quality of life: Patient-reported outcomes, visual function questionnaires, treatment satisfaction.
  • Time horizon: Short-term (1–2 years) vs. long-term (5 years or lifetime) perspectives are critical because initial costs may be offset by later savings.

Economic Considerations: Upfront vs. Long-Term Costs

A frequently cited barrier to dual therapy is the higher initial cost. For example, combining an anti-VEGF injection (e.g., aflibercept ~$1,850 per dose) with a dexamethasone implant (Ozurdex ~$1,200–$1,500) or a fluocinolone implant (Iluvien ~$5,000–$8,000) can double or triple the first-year medication cost compared to anti-VEGF monotherapy. However, proponents argue that if dual therapy sufficiently reduces injection frequency—from monthly to every 3–4 months—the cumulative five-year cost could be lower, especially when factoring in fewer clinic visits, imaging, and reduced indirect costs.

Several cost-effectiveness analyses have addressed this. A 2024 systematic review in JAMA Ophthalmology examined model-based studies for DME treatments. It found that anti-VEGF monotherapy was generally cost-effective at typical willingness-to-pay thresholds, but combination therapy with corticosteroid implants was cost-effective only in specific populations: pseudophakic patients with chronic DME who had suboptimal response to anti-VEGF. In these subgroups, the reduced injection burden and improved anatomical outcomes offset the higher implant cost over three to five years. For phakic patients, the high rate of cataract surgery associated with corticosteroids eroded the cost advantage.

Another key economic factor is healthcare resource utilization. Dual therapy may reduce the number of intravitreal injection visits, which require sterile preparation, monitoring, and potential complications. In busy retina practices, reducing visit frequency can free up capacity for other patients, improving overall system efficiency. However, the cost of the combination procedure itself (e.g., performing both injection and implant in one visit) may be similar to a single injection visit, but the drug cost is additive.

Clinical Outcomes: Evidence from Pivotal Studies

To evaluate the benefit side of the ratio, we review key clinical data for three major dual therapy scenarios:

Anti-VEGF + Dexamethasone Implant for Persistent DME

The DRCR.net Protocol U (published 2016) randomized patients with persistent DME despite at least three prior anti-VEGF injections to continue ranibizumab monthly plus either dexamethasone implant or sham. At 24 weeks, the combination group showed greater improvement in central subfield thickness but no significant difference in visual acuity (mean gain ~5 letters vs. ~3 letters in the sham group). However, by 52 weeks, the visual acuity difference was still modest and not statistically significant. The combination group had more cataract progression and IOP elevation. A post hoc analysis suggested that pseudophakic eyes had more robust visual benefits. Therefore, the clinical benefit–to–risk ratio is favorable in pseudophakic, recalcitrant DME, but marginal in phakic eyes.

Anti-VEGF + Focal Laser for DME

The DRCR.net Protocol I showed that ranibizumab plus prompt laser reduced the mean number of injections over three years compared to ranibizumab alone (11 vs. 16), with similar visual outcomes. However, the laser group had more macular scarring and loss of small pigment epithelial detachments. The trade-off: fewer injections but potential permanent retinal damage. Many clinicians now reserve laser for persistent edema after anti-VEGF monotherapy, making it a delayed dual therapy rather than immediate combination.

Anti-VEGF + PRP for PDR

Protocol S demonstrated that ranibizumab alone provided comparable visual outcomes to PRP alone at two years, with lower rates of vitreous hemorrhage and need for vitrectomy. However, combination therapy (PRP + ranibizumab) is not standard because PRP does not reduce injection frequency significantly. Instead, dual therapy in PDR often involves anti-VEGF injections to control neovascularization while using PRP for long-term stabilization—a sequential approach. A recent trial (CLARITY) showed that starting with aflibercept and adding PRP as needed reduced the risk of vitreous hemorrhage compared to PRP alone. The cost-effectiveness of this dual approach depends on the number of injections needed.

Faricimab: Dual Mechanism in One Drug

The YOSEMITE and RHINE trials for DME found faricimab (anti-VEGF-A/anti-Ang-2) noninferior to aflibercept with a superior durability profile: 54% of patients on faricimab could maintain every-16-week dosing, compared to 32% for aflibercept at 8-week intervals. This resulted in fewer injections over two years (mean 9.5 for faricimab vs. 12.1 for aflibercept). While faricimab has a higher per-dose cost (~$2,200 vs. aflibercept $1,850), the reduced injection frequency may lower total costs over time. For patients who cannot achieve extended dosing with anti-VEGF monotherapy, faricimab essentially provides a built-in dual therapy benefit without the inconvenience of separate agents.

Patient Stratification: Who Benefits Most?

The cost-benefit ratio is not uniform across all diabetic eye disease patients. Identifying subgroups where dual therapy provides clear advantage is essential for personalized medicine:

  • Pseudophakic patients with chronic DME and incomplete response to anti-VEGF: Highest likelihood of benefit from adding a corticosteroid implant. The risk of cataract progression is moot, and visual gains may be more sustained. Several cost-effectiveness models show this group yields the best return on investment.
  • Phakic patients with DME: Dual therapy with corticosteroid is less attractive because of cataract risk, which often leads to additional surgery costs and transient vision loss. For these patients, switching to a bispecific antibody like faricimab or adding focal laser may be more cost-effective.
  • Patients with PDR and high-risk features: Combination of anti-VEGF and PRP may reduce vitreous hemorrhage risk, but economic analyses are sparse. Given that vitreous hemorrhage can lead to emergent vitrectomy (costing >$10,000 per case), even a moderate reduction could be cost-saving.
  • Patients with good visual acuity at presentation: Early aggressive dual therapy may overtreat eyes that would do well with monotherapy. The incremental cost of dual therapy in such patients is unlikely to be justified.

Safety Profile and Quality of Life Implications

Cost-benefit analysis must include adverse events. Dual therapy with corticosteroids increases the risk of cataract (especially in phakic eyes) and elevated IOP requiring medical or surgical intervention. These events incur additional costs—cataract surgery ($3,000–$5,000 per eye) and glaucoma medications or surgery—which can offset the savings from fewer injections. Conversely, anti-VEGF monotherapy carries a low but cumulative risk of endophthalmitis with each injection; reducing injections by even one per year may lower this risk proportionally.

From a patient perspective, the burden of frequent clinic visits is substantial. The NEI VFQ-25 questionnaire studies show that treatment burden negatively impacts emotional well-being and daily activities. If dual therapy can reduce visit frequency without compromising vision, quality of life improves. Some patients prefer a slightly higher drug cost if it means fewer office visits, especially those who live far from retinal specialists or have mobility issues.

Healthcare System and Payer Perspectives

In value-based care models (e.g., bundled payments, accountable care organizations), the total cost of care for a diabetic patient over a year includes ophthalmic services, diabetes management, and complications. A retina specialist may feel pressure to choose therapies that minimize overall expenses, even if the drug cost is higher. Dual therapy that reduces injections from 8 to 4 per year may lower total procedure-related costs (each injection visit costing ~$500–$700 in Medicare reimbursement), so the net cost to the payer may be neutral or favorable despite higher drug costs.

Medicare and commercial insurers often require step therapy: first try anti-VEGF monotherapy, then consider a corticosteroid implant only if inadequate response. This policy implicitly acknowledges the cost-benefit advantage of reserving dual therapy for nonresponders. However, some argue that early dual therapy could prevent progression and reduce long-term disability—a hypothesis that needs prospective trials with long follow-up.

Conclusion: Toward Personalized Cost-Effective Dual Therapy

The cost-benefit ratio of dual therapy in long-term diabetic eye disease management is nuanced and highly context-dependent. For pseudophakic patients with persistent DME despite anti-VEGF, adding a dexamethasone or fluocinolone implant appears cost-effective by improving anatomical outcomes and reducing injection frequency over several years. For phakic patients, the cataract risk limits the value; alternative dual mechanisms such as faricimab or deferred laser may offer a better balance. In PDR, combining anti-VEGF with PRP is generally reserved for aggressive cases but may be cost-effective if it prevents costly surgeries. Overall, the current evidence does not support routine first-line dual therapy for all diabetic retinopathy patients. Instead, a stratified approach based on lens status, response to prior therapy, and disease severity is most likely to yield a favorable cost-benefit ratio.

Future research should focus on head-to-head comparisons of dual therapy versus high-dose monotherapy (e.g., aflibercept 8 mg) and longer-term cost-effectiveness models incorporating real-world adherence and quality-of-life data. As the diabetic population grows, ophthalmologists must work with health economists and payers to define biomarkers that predict dual therapy responders. Ultimately, the goal is not merely to evaluate cost vs. benefit but to align treatment intensity with individual patient needs—optimizing both vision outcomes and resource allocation in a sustainable system.