The authors have declared that no competing interests exist.
To investigate the relationship between baseline number of hyperreflective foci (HF) on spectral domain optical coherence tomography (SD-OCT) in patients with diabetic macular edema (DME), as well as the dynamics of HF during treatment with anti-vascular endothelial growth factor (VEGF), and treatment response.
We evaluated patients diagnosed with DME scheduled for treatment with intravitreal bevacizumab. Eyes were classified as adequate or insufficient treatment responders based on logMAR visual acuity improvement and central retinal thickness (CRT) decrease after three consecutive injections. Associations between number of HF at baseline and treatment response, the change in HF over the course of treatment, and the distribution of HF within the retinal layers were evaluated.
In 54 eyes of 41 patients, mean number of HF and CRT decreased after intravitreal treatment with bevacizumab (p = 0.002 and p<0.001 respectively). Decrease in CRT after 3 months was independently associated with a higher number of HF at baseline (estimated effect -2.61, 95% CI [-4.42–-0.31], p = 0.006). Eyes with adequate treatment response presented with more HF at baseline (OR 1.106, 95% CI [1.012–1.210], p = 0.030) than eyes with insufficient treatment response. Most HF were located within the inner retinal layers, and decrease of HF was mostly due to a decrease of inner retinal HF.
In patients with DME treated with anti-VEGF, higher baseline numbers of HF have predictive value for treatment response in terms of visual acuity improvement and CRT decrease after 3 months. In addition, HF were responsive to anti-VEGF therapy.
Diabetic macular edema (DME) is a sight threatening complication of diabetes mellitus (DM) and one of the most frequent causes of vision loss.[
Although visual function is the most relevant outcome measure, it is a subjective measure of treatment response, and can be influenced by for example fluctuations in glucose levels or the presence of other ocular disorders. Conversely, anatomical measurements such as central retinal thickness (CRT) on spectral domain optical coherence tomography (SD-OCT) are a more objective and reliable outcome measure for treatment response. The diabetic retinopathy clinical research network (DRCR.net) employs a combination of both outcome measures and defined insufficient treatment response as a CRT decrease of ≤10%, or a gain of ≤5 letters on the Early Treatment of Diabetic Retinopathy Study (ETDRS) chart, the equivalent of 0.1 logMAR.[
Hyperreflective foci (HF) are well-circumscribed dots that can be visualized on SD-OCT in all retinal layers. They were first described in patients with DM by Bolz et al. and have since been associated with the presence of DME, as well as with non-proliferative stages of diabetic retinopathy.[
The purpose of this study was to investigate the association between baseline number of HF and treatment response to anti-VEGF in terms of visual acuity (VA) improvement and CRT decrease. We also studied the location of HF in the neuroretina and the behavior of HF during anti-VEGF treatment.
We reviewed the medical files of DM type 2 patients with DME who were treated with intravitreal injections of bevacizumab (1.25 mg) at the department of Ophthalmology of the Radboud University Medical Center between November 2010 and May 2013. We restricted inclusion to treatment naive patients who received a complete loading dose of three consecutive injections with a 4–6 weeks interval, and of whom baseline and 3 month follow up data were available. Other exclusion criteria were: laser treatment or intraocular surgery within 12 weeks prior to the first injection, active proliferative diabetic retinopathy, vitreous hemorrhage or tractional retinal detachment at baseline visit, and presence of other retinal vascular diseases. This study adhered to the tenets of Helsinki. The Research Ethics Committee of the Radboud university medical center Nijmegen approved this study and waived the requirement for informed consent (2018–4424). All data was fully anonymized before it was accessed by the investigators.
The following clinical characteristics were assessed: gender, age, duration of DME, and DR staging according to International Clinical Diabetic Retinopathy Severity Scale.[
We selected baseline and 3 months B-scans centered on the fovea and evaluated these scans for the presence of HF within the central 3000 μm around the fovea (
Foveal centered spectral domain optical coherence tomography (SD-OCT) B-scan image of a patient with DME before (A) and after (B) 3 injections with anti-VEGF. Black arrows indicate hyperreflective foci, within 3000 μm of the fovea (dashed bars).
An intraclass correlation coefficient for the number of HF was calculated to assess interrater agreement. To account for the relationship between both eyes, univariable linear mixed model analyses were used to assess the difference in CRT, VA and number of HF before and after treatment, and to evaluate the association between baseline number of HF and (change in) CRT and VA. To correct for potential confounders, multivariable linear mixed model analyses were used, applying stepwise backward deletion of non-significant confounders with an influence of <10% on the estimate of HF at baseline. These analyses were conducted using SPSS version 22 (SPSS, Chicago, IL, USA). Mixed effect logistic regression analysis was used to assess associations between baseline number and change of HF with adequate or insufficient treatment response, expressed as an odds ratio (OR) with 95% confidence interval (CI). These analyses were performed in SAS Statistical Analysis Software 9.2 (SAS Institute, Cary, NC, USA). P-values <0.05 were considered statistically significant.
Fifty-four eyes of 41 subjects were evaluated over the course of 3 months of treatment with bevacizumab. Patient characteristics at baseline are described in
Mean changes in central retinal thickness (A), visual acuity (B) and number of hyperreflective foci (C) at baseline and after 3 injections with anti-VEGF. The bars represent mean ± 95% confidence interval. *P<0.05.
Variable |
|
---|---|
Gender, n (%) | |
Male | 22 (54%) |
Female | 19 (46%) |
Age, mean (SD), years | 67 (12) |
Duration DME per eye, median (IQR), months | 8 (2–21) |
DR stage per eye, n (%) | |
Mild | 9 (17%) |
Moderate | 41 (76%) |
Severe | 4 (7%) |
Presence of cysts per eye, n. (%) | 51 (94%) |
Presence of subretinal fluid per eye, n (%) | 13 (24%) |
Foveal disruption of ELM per eye, n (%) | 20 (37%) |
Foveal disruption of PR layer per eye, n (%) | 21 (39%) |
n = number; SD = standard deviation, DM = diabetes mellitus; DME = diabetic macular edema; IQR = interquartile range; DR = diabetic retinopathy; ELM = external limiting membrane; PR = photoreceptor
HF were scattered throughout all retinal layers. The mean number of HF in the inner retinal layers at baseline was 10.4 ± 7.3 versus 7.9 ± 5.0 after treatment (p = 0.010,
The number of HF at baseline was independently associated with a decrease in CRT after 3 months (p = 0.006,
Univariable | Multivariable | |||||
---|---|---|---|---|---|---|
Estimate | 95% CI | P | Estimate | 95% CI | P | |
CRT baseline, μm | -1.89 | -5.71–1.94 | 0.325 | -3.54 | [-7.44–0.366] | 0.074 |
CRT change, μm | -2.47 | -4.64 –-0.31 | 0.026 |
-2.61 | [-4.42–0.79] | 0.006 |
VA baseline, logMAR | 0.013 | 0.004–0.023 | 0.008 |
0.008 | [0.001–0.016] | 0.047 |
VA change, logMAR | -0.002 | -0.009–0.004 | 0.473 | -0.002 | [-0.006–0.009] | 0.661 |
Multivariable analyses were corrected for gender, age, duration of DME, DR stage, presence of cysts, presence of subretinal fluid, disruption of the external limiting membrane, disruption of the photoreceptor layer and the presence of disorganization of the retinal inner layers. Analyses of CRT and VA changes were also corrected for both CRT baseline and VA baseline. Analysis of CRT baseline was also corrected for VA baseline, and analysis of VA baseline was also corrected for CRT baseline.
CI = confidence interval; HF = hyperreflective foci; CRT = central retinal thickness
*P<0.05.
Next, we stratified the cohort into two groups with either adequate or insufficient treatment response. A total of 30 eyes (56%) showed a CRT decrease of ≥10%, while 16 eyes (30%) showed an improvement in VA of ≥0.1 logMAR. Subsequently, 13 eyes (24%) met both CRT and VA criteria for adequate treatment response, classifying 41 eyes (76%) as insufficient responders. Eyes that were classified as adequate responders presented with higher numbers of HF at baseline than eyes with insufficient CRT and VA response (21.6±9.5 vs. 12.7±8.8, OR 1.106, 95% CI [1.012–1.210], p = 0.030,
Mean number of HF at baseline in groups based on insufficient and adequate CRT response (A); insufficient and adequate VA response (B); and insufficient and adequate combined CRT + VA response (C). Mean change in number of HF in groups based on insufficient and adequate CRT response (D); insufficient and adequate VA response (E); and insufficient and adequate combined CRT + VA response (F). The distribution of HF in the inner and outer retinal layers is displayed as a percentage. The values represent the odds ratio with corresponding 95% confidence interval and p-value. The odds ratio of adequate response is 1.106, which can be interpreted as an increase, or chance, for adequate response by 10.6% for every HF at baseline; when the number of HF at baseline increases by 10, the chance for adequate response increases exponentially by 1.10610 = 2.74 or 274%. The bars represent mean ± 95% confidence interval and are based on descriptive statistics. *P<0.05.
We did not observe a significant difference in HF change between eyes with an adequate CRT and VA response and eyes with insufficient CRT and VA response (-9.5±7.4 vs. -2.6±8.8, OR 0.912, 95% CI [0.831–1.001], p = 0.052,
Higher numbers of HF at baseline were associated with adequate treatment response to anti-VEGF, in terms of CRT decrease and VA improvement. The relationship between baseline number of HF and CRT decrease was also apparent in linear mixed model analysis, showing that the effect was independent from potential confounders. In addition, HF were responsive to treatment with anti-VEGF, and were more often detected in the inner retinal layers than in the outer retinal layers. We also observed that a high number of HF at baseline was associated with poorer VA prior to treatment with anti-VEGF.
The observation that higher numbers of HF at baseline are associated with adequate treatment response could be of importance for clinical practice. For example, when poor response to anti-VEGF can be predicted based on baseline biomarkers, the decision to start with an alternative treatment can be made beforehand, thereby preserving visual performance. Ideally, these findings should be integrated in a prediction model that can reliably predict treatment response, including all other potential predictive factors, such as patient characteristics, environmental factors, genotype variables and other imaging biomarkers to be further investigated.
To the best of our knowledge, a relationship between high baseline number of HF and both adequate morphological and functional treatment outcomes in DME has not been established before, although it has been studied in other cohorts. An association between higher numbers of HF and final visual acuity at a mean of 7 months after treatment with bevacizumab in 33 eyes with DME accompanied by serous detachment was reported by Kang et al.[
The association between higher baseline number of HF and poorer baseline VA is in line with previous studies,[
Various different hypotheses have emerged about the origin of HF that might in fact coexist. HF could be precursors of hard exudates,[
Overall, there was a significant decrease in CRT, but no significant improvement in VA after 3 injections of bevacizumab in this cohort. Earlier studies demonstrated that treatment outcomes in real life are often inferior to the results of controlled clinical trials.[
The use of a well-designed, detailed grading protocol was one of the major strengths of this study, evidenced by the good interrater agreement. This protocol enables replication of our findings and validation in other cohorts. Another strength was the well-defined cohort: we used strict inclusion criteria to limit the analysis to eyes with a completed loading phase and follow-up. Sample size and the short duration of follow-up can be considered limitations of our study, although it has been shown that VA response at 3 months is highly predictive for long term outcomes of anti-VEGF therapy.[
In conclusion, our results suggest that in patients with DME, baseline number of HF are correlated with visual acuity as well as anti-VEGF treatment response in terms of CRT reduction and VA improvement. Replication of our findings in larger cohorts is needed to assess the validity of our study. Additionally, the relation between HF and other anti-VEGF agents and corticosteroids needs to be further explored. This knowledge may contribute to the development of proper risk assessment, and therefore enable personalized decision making and prevention of overtreatment.
(SAV)
The authors thank Milan Phan and Gudo Borgerink for their contribution to the data collection, and Priya Vart for his help conducting the statistical analysis.