Findings from a recent study published in BMC Ophthalmology identified biomarkers that may predict an early anatomical response to intravitreal ranibizumab (IVR) for diabetic macular edema (DME) using optical coherence tomography angiography (OCT-A).
Give me some background.
DME is an ocular complication of diabetes resulting from a damaged blood-retinal barrier caused by elevated blood glucose levels resulting in leakage of fluid from the retina vessels into the adjacent neural retina.
- Its treatment: Anti-vascular endothelial growth factor (VEGF) intravitreal injections.
Previous studies have shown that the efficacy of anti-VEGF injections varies for DME patients, with a relative to that depended on baseline visual acuity.
- Further: Certain anti-VEGF agents impose a greater financial burden on patients, potentially impacting the treatment approach.
Bring it back to this study.
Using OCT-A, physicians can now noninvasively image retinal microvasculature and monitor characteristics of diabetic retinopathy, such as:
- Degree of hypoperfusion in the retina
- Vessel density (VD) in the superficial and deep capillary plexuses (SCP and DCP)
- Foveal avascular zone area (FAZ-A) measurements
Consequently, researchers sought to evaluate whether these characteristics could predict the treatment response to IVR for DME.
Now talk about the study.
In this prospective study, investigators included 111 eyes of 102 naive participants (58.8% female, mean age: 54.54 years [35-69 years]) who had DME.
Enrolled patients underwent a complete ophthalmologic history and examination using a pre-designed OCT-A checklist.
Findings?
The research team compared the best-corrected visual acuity (BCVA) and central macular thickness (CMT) before and after IVR injection in good and poor responders:
- BCVA
- Good responders
- Pre-IVR: 0.704 ± 0.158
- Post-IVR: 0.305 ± 0.131
- Poor responders
- Pre-IVR: 0.661 ± 0.164
- Post-IVR: 0.540 ± 0.178
- Good responders
- CMT
- Good responders
- Pre-IVR: 436.22 ± 54.66 µm
- Post-IVR: 308.12 ± 33.09 µm
- Poor responders
- Pre-IVR: 387.74 ± 44.05 µm
- Post-IVR: 372.09 ± 52.86 µm
- Good responders
The researchers found that the FAZ-A was 0.297 ± 0.038 mm in good responders and 0.407 ± 0.05 mm in nonresponders.
Anything else?
Investigators then compared the preoperative VD of different areas in good and bad responders, including:
- SCP VD
- Good responders: 24.02 ± 3.01% µm
- Poor responders: 17.89 ± 3.19% µm
- SCP parafoveal VD
- Good responders: 43.06 ± 2.67% µm
- Poor responders: 37.96 ± 1.82% µm
- DCP foveal VD
- Good responders: 30.58 ± 2.89% µm
- Poor responders: 25.45 ± 3.14% µm
What does this all mean?
The study authors noted that “eyes with large FAZ-A and/or insufficient baseline VD measurements, particularly at the SCP level, demonstrated a reduced anatomical response corresponding to that of eyes that responded initially to three initial IVR injections.”
Meaning: Eyes lacking a response to IVR may be more susceptible to developing macular ischemia—potentially as a result of increased VEGF production that could render anti-VEGF treatment ineffective and allow DME to persist.
Limitations?
These included:
- Analyzing the data of patients in varying stages of diabetic retinopathy (DR)
- A 3-month follow-up period
Take home.
These findings suggest that OCT-A offers an accurate measurement for VD in the macular as well as the FAZ-A, which could be used to predict an early treatment response to IVR in DME patients.
The VD in the SCP and DCP and FAZ-A size at baseline can predict an early treatment response to IVR—supporting the belief that eyes with more severe ischemia detected by OCT-A at baseline are less responsive to anti-VEGF treatment.