OPTICAL COHERENCE TOMOGRAPHIC HYPERREFLECTIVE FOCI IN EARLY STAGES OF DIABETIC RETINOPATHY UMBERTO DE BENEDETTO, MD, RICCARDO SACCONI, MD, LUISA PIERRO, MD, ROSANGELA LATTANZIO, MD, FRANCESCO BANDELLO, MD, FEBO Purpose: To analyze the presence of hyperreflective foci in Type 1 and Type 2 diabetic patients, separately, without clinically significant diabetic macular edema and visual impairment. Methods: Noninvasive, observational prospective study. Seventeen and 19 consecutive Type 1 and Type 2 diabetic patients (33 and 38 eyes), respectively, were recruited. All patients had no clinically significant diabetic macular edema or visual impairment. Two age- and sexmatched control groups were also included. Patients underwent an ophthalmologic examination including spectral domain optical coherence tomography. Hyperreflective foci were counted considering horizontal B-scan passing through the fovea. Results: On spectral domain optical coherence tomography, patients affected by Type 1 and Type 2 diabetes had a mean of 7.5 ± 4.6 and 9.9 ± 4.5 hyperreflective foci, respectively. Subjects of control groups had a mean of 0.9 ± 0.8 and 1.7 ± 1.5 hyperreflective foci, respectively. Hyperreflective foci amount was statistically different between Type 1 and Type 2 diabetic groups (P = 0.032) and significantly higher in diabetic patients than in controls (P , 0.001). Hyperreflective foci amount was significantly higher in diabetic patients with a poor quality glycometabolic control (P , 0.001 and P = 0.016) or affected by hypertension (P = 0.008). Conclusion: We reported the presence of hyperreflective foci in diabetic patients without diabetic macular edema and visual impairment. This spectral domain optical coherence tomography finding might be a useful marker for the diagnosis and the follow-up in the early stage of diabetic retinopathy. RETINA 35:449–453, 2015
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iabetic retinopathy represents the most important cause of visual impairment in working-age individuals.1 In this vascular retinopathy, inner retinal capillary changes lead to the breakdown of the blood– retina barrier, and this alteration give rise to an increased vascular permeability and to diabetic macular edema (DME).2,3 The Wisconsin Epidemiologic Study of Diabetic Retinopathy reported an incidence of DME over a 10-year period between 13.9% and 25.4%, making it the first mechanism of vision loss in patients with nonproliferative diabetic retinopathy (NPDR).4
During the last decade, optical coherence tomography (OCT) has become a popular noninvasive optical imaging modality used widely to detect pathologic changes in the macular morphology and objectively measure the retinal thickness in patients affected by DME.5–10 Bolz et al11 studied diabetic retinopathy using spectral domain OCT (SD-OCT) and described for the first time in the literature the presence of hyperreflective foci (HRF) in patients with DME. Subsequently, Uji et al12 demonstrated that the presence of HRF in the outer retina was associated with disrupted external limiting membrane or inner/outer segment line, suggesting photoreceptor degeneration in patients with DME; these findings were also associated with a decreased visual acuity, showing the clinical relevance of the HRF. Recently, Vujosevic et al13 also described the migration of HRF from the inner to the outer retina layers during the diabetic retinopathy progression.
From the Department of Ophthalmology, San Raffaele Scientific Institute, University Vita-Salute, Milan, Italy. None of the authors have any financial/conflicting interests to disclose. Reprint requests: Luisa Pierro, MD, Department of Ophthalmology, San Raffaele Scientific Institute, Via Olgettina, 60, 20132 Milan, Italy; e-mail: [email protected]
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In this study, we investigate the presence of HRF in asymptomatic patients affected by Type 1 or Type 2 diabetes, separately, without clinically significant DME and visual impairment. The aim of this study was to analyze if HRF may be an early marker of diabetic retinopathy. Material and Methods In this noninvasive, observational, and prospective study, we recruited 71 eyes of 36 consecutive asymptomatic patients affected by Type 1 or Type 2 diabetes who presented to the Retina Service of the San Raffaele Department of Ophthalmology in Milan between December 2010 and January 2012. Inclusion criteria were 18 years or older of age, diagnosis of Type 1 diabetes at least 10 years before or Type 2 diabetes at least 5 years before, the presence of a very mild NPDR with microaneurysms only or the presence of a mild NPDR with microaneurysms plus hard exudates, cotton-wool spots, and/or mild retinal hemorrhages corresponding to Grades 20 and 35, respectively, on the Early Treatment of Diabetic Retinopathy Study (ETDRS) scale. Exclusion criteria were the presence of visual impairment (best-corrected visual acuity [BCVA], .0.1 logMAR), presence of hard exudates or retinal hemorrhages along the horizontal B-scan passing through the fovea, previous ocular surgery or laser treatment to the retina, refractive error .5 diopters, significant media opacities, evidence of DME on fundus biomicroscopy, sign of any other active retinal disease in the study eye (including the presence of an epiretinal membrane or vitreomacular traction syndrome). Two age- and sex-matched control groups were also included. All individuals were volunteers recruited specifically for this study. A younger control group (individuals younger than 40 years) was matched to the group of patients with Type 1 diabetes, and an older control group (individuals older than 40 years) was matched to the group of patients with Type 2 diabetes. The following clinicopathologic data were recorded for each subject (diabetic patients and control subjects): questions about general health status (including previous diagnosis of hypertension [HTN] and/or other cardiovascular diseases identified by their medical doctors or their cardiologists, and hemoglobin A1c [HbA1c] levels), measurement of BCVA (determined in all subjects with logMAR and ETDRS charts), intraocular pressure, fundus examination, color fundus photographs, and SD-OCT scans obtained using Spectral OCT SLO (OPKO/OTI, Ophthalmic Technologies Inc, Toronto, Canada). Linear scans of the macula were performed to evaluate
macular morphology, and a 128 · 512 raster scan to obtain central foveal thickness (CFT). The presence of HRF was defined as the presence of small focal hyperreflective areas scattered mainly in outer retinal layers but also spreading in all retinal layers observed in at least one SD-OCT scan14; HRF are invisible at clinical examination and fundus photography. The number of HRF was determinate considering the horizontal B-scan passing through the fovea. In the presence of microaneurysms or vessels visible in the fundus photography, the hyperreflective spots corresponding to these findings were excluded by the count of HRF. Two examiners well trained in OCT evaluation and masked to the purpose of the investigation (L.P. and R.L.) independently appraised the OCT images. Statistical analysis was performed using IBM (Armonk, NY) SPSS Statistics version 20. The Gaussian distribution of continuous variables was verified with the Kolmogorov-Smirnov test. Comparisons of mean HRF amount, CFT, BCVA, HbA1c level, age, and duration of the disease between control groups and Type 1 and Type 2 diabetic groups were performed using the Student’s t-test. Also comparison of mean HRF amount, age, and duration of the disease between Type 2 diabetic patients affected by HTN and Type 2 diabetic subjects without HTN was performed using the Student’s t-test. Pearson correlation analyses were performed to analyze the correlation between HRF amount, CFT, and HbA1c level. In all analyses, values of P , 0.05 were considered as statistically significant. We certify that all applicable institutional and governmental regulations concerning the ethical use of human volunteers were followed during this study. It was approved by the Institutional Review Board of the San Raffaele Scientific Institute. The study was performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki. All study patients provided written informed consent to the use of their personal data. Results Between December 2010 and January 2012, a total of 71 NPDR eyes of 36 consecutive asymptomatic diabetic patients were included for the current analysis. One eye of 1 patient affected by Type 1 diabetes was excluded for amblyopia. Seventeen and 19 patients (33 and 38 eyes) were affected by Type 1 and Type 2 diabetes, respectively. The mean age at diagnosis was 36.0 ± 8.1 years (median, 36; range, 23–45 years) in Type 1 group and 63.9 ± 8.7 years (median, 34; range, 48–76 years) in Type 2 group (P , 0.001). All patients were whites, 58.3% of them were men, and 41.7% were women. Systemic HTN was recorded in 14 patients affected by
HRF IN EARLY DIABETIC RETINOPATHY DE BENEDETTO ET AL
Type 2 diabetes. None of Type 1 diabetic patients was affected by HTN. Type 1 and Type 2 diabetic patients reported a mean duration of the disease of 19.2 ± 8.2 years and 10.6 ± 4.4 years, respectively (P , 0.001). Mean HbA1c level was 8.4 ± 1.6% (range, 5.9–11.8%) and 7.2 ± 0.7% (range, 6.1–8.4%) for Type 1 and Type 2 diabetic patients (P , 0.001). The subjects of control groups were selected homogenous for age and sex. A control group of 15 younger individuals (mean age, 32.3 ± 3.4 years; median, 33; range, 24–36 years) was compared with the group of Type 1 diabetic patients (P = 0.067). A control group of 13 older subjects (mean age, 57.1 ± 7.6 years; median, 52; range, 40–61 years) was compared with the group of Type 2 diabetic patients (P = 0.052). Mean BCVA was 0.00 ± 0.01 logMAR (range, 0–0.05 logMAR) for Type 1 diabetic group and 0.00 ± 0.02 logMAR (range, 0–0.1 logMAR) for Type 2 diabetic group (P = 0.075). Best-corrected visual acuity was 0 logMAR in all control patients. On SD-OCT examination, intraretinal HRF were present in all patients affected by Type 1 (Figure 1, B and C) and Type 2 (Figure 2, B and C) diabetes as scattered punctiform dots invisible at clinical examination, fundus photography, and in red-free images (Figures 1A and 2A). Patients affected by Type 1 and Type 2 diabetes had a mean of 7.5 ± 4.6 HRF (median, 7.0; range, 3–22) and 9.9 ± 4.5 HRF (median, 10.0; range, 4–21), respectively; HRF amount was then statistically different between Type 1 and Type 2 diabetic patients (P = 0.032). Subjects of control groups had a mean of 0.9 ± 0.8 HRF (median, 1.0; range, 0–3) and 1.7 ± 1.5 (median, 1.0; range, 0–5), respectively (P = 0.067). Moreover, comparing the diabetic groups (Types 1 and 2) with the respective control groups, HRF amount was significantly higher in the diabetic patients (P , 0.001 in both groups). Mean CFT was 234.5 ± 13.7 mm (184–297 mm) and 256.3 ± 12.7 mm (175–337 mm) for Type 1 and Type 2 diabetic patients, respectively (P = 0.061). In the 2
451
control groups, mean CFT was lower than in diabetic groups (218.8 ± 14.3 mm [P = 0.034] and 222.8 ± 15.4 mm [P = 0.004], respectively). In both diabetic groups, no significant correlation was found between the number of HRF and the CFT (P = 0.495 and =0.145, respectively). Instead, the overall HRF amount in the 2 diabetic groups (Types 1 and 2), analyzed separately, was correlated significantly to the HbA1c levels (P , 0.001 and P = 0.016, respectively); patients with a poor quality glycometabolic control were associated with a larger presence of HRF. In the Type 2 diabetic group, there was a significant correlation between HRF amount and the presence of HTN. Patients affected by HTN had a higher number of HRF than subjects without HTN (11.2 ± 4.6 and 6.8 ± 2.7 HRF, respectively; P = 0.008). These 2 subgroups did not differ in HbA1c levels (7.15 ± 0.72 and 7.43 ± 0.49%, respectively; P = 0.382) and duration of the disease (11.1 ± 4.7 and 9.6 ± 3.7 years, respectively; P = 0.381). Patients affected by HTN were older than patients without HTN (mean age, 58.8 ± 8.9 and 66.0 ± 7.8 years, respectively; P = 0.025), but there was no significant correlation between age and number of HRF in these 2 subgroups (P = 0.531 and =0.233, respectively). Sex, patient age, and duration of the disease did not influence significantly the number of HRF within the retinal layers. Discussion Diabetic macular edema is a well-known cause of visual impairment in diabetic patients. In the last 2 decades, the role of OCT was stressed to analyze morphologic retinal changes and to understand physiopathologic mechanisms of DME. Thereby, Bolz et al11 described a new OCT retinal entity characterized by the presence of scattered, punctiform clinically invisible dots located in all retinal layers of patients affected by DME; these new findings were named HRF. The presence of these foci was also described
Fig. 1. Red-free image (A) does not show the presence of HRF. Spectral domain optical coherence tomography horizontal B-scan passing through the fovea (B and C) reveals the presence of 10 HRF (arrows) in a patient affected by Type 1 diabetes.
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Fig. 2. Red-free image (A) without HRF. Spectral domain optical coherence tomography examination (B and C) showing the presence of 12 HRF (arrows) in a patient affected by Type 2 diabetes.
in other retinal diseases, such as age-related macular disease, retinal vein occlusions, and uveitis.14–18 Uji et al12 showed the clinical relevance of HRF, reporting that their presence in the outer retina layers decreases visual acuity of subjects with DME. Although the anatomical correspondence of this new finding is not clear, Bolz et al11 and Ota et al17 and Framme et al19 further suggested that HRF are a morphologic sign of accumulation of intraretinal fluid and lipid extravasation, and consequently precursors of hard exudates. This hypothesis may be supported by our results that showed a higher number of HRF in patients with the worst glycometabolic control than in subjects with lower HbA1c levels; patients with the worst glycometabolic control may have a greater lipid extravasation associated with a higher HRF amount. However, different etiologies have been suggested about the nature of HRF. Coscas et al14 interpreted the presence of these foci in patients affected by agerelated macular disease as activated microglia cells in a biological inflammatory reaction. This inflammatory reaction, which was well documented in the early stages of diabetic retinopathy,20–22 may support the hypothesis that HRF represent accumulation of inflammatory cells in diabetic retinopathy also. Using SD-OCT, in the current series, we investigated the presence of HRF in asymptomatic Type 1 and Type 2 diabetic patients affected by NPDR, without clinically significant DME and visual impairment (BCVA, 0–0.1 logMAR). The presence of HRF was detected in all diabetic patients, scattered in all retinal layers. To the best of our knowledge, no study was published comparing the different distribution of HRF in the two types of diabetes. We demonstrated that Type 1 diabetic patients had less HRF than individuals affected by Type 2 diabetes (P = 0.032). Consequently, the disease duration is not involved in the genesis of HRF considering that Type 1 diabetic patients reported a longer duration of the disease than subjects affected by Type 2 diabetes. Even the different age of the
patients cannot be considered a cause of HRF development because no significant difference in HRF amount was found between the control groups with the young and the old patients. Therefore, this different HRF amount in Type 1 and Type 2 diabetic patients may conceal itself in the dissimilar pathogenesis of the 2 types of diabetes. The presence of HTN, which was demonstrated as an important risk factor of development of diabetic retinopathy,23 may play an important role in the pathogenesis of HRF. Analyzing our data, we reported that the presence of HTN was significantly correlated with a higher number of HRF in Type 2 diabetic patients (P = 0.008); therefore, the presence of HTN may be considered an important cofactor in the development of HRF in individuals affected by Type 2 diabetes impairing the fluid resorption in the retinal layers.24 Also a poor quality glycometabolic control was associated with a larger presence of HRF, and this finding confirms again the importance of an optimal glycometabolic control in diabetes. The most important limitations of our study were the small sample size and the absence of a long-term followup. Further studies are on the way to investigate changes of the HRF amount and distribution over time, and their association with variations of glycometabolic status, CFT, and visual acuity. In conclusion, using SD-OCT, we demonstrated that there is a significant difference of the HRF amount in Type 1 and Type 2 diabetic patients. Our data suggested that this OCT finding might be a useful marker for the diagnosis of diabetic retinopathy in the early stage of the disease (i.e., asymptomatic NPDR patients without DME); these clinically invisible foci might also be useful as an additional marker for the glycometabolic status of the patients. Key words: diabetic retinopathy, hyperreflective dots, hyperreflective foci, SD-OCT.
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References 1. Klein R, Klein BE, Moss SE. The Wisconsin epidemiologic study of diabetic retinopathy. XVI. The relationship of C-peptide to the incidence and progression of diabetic retinopathy. Diabetes 1995;44:796–801. 2. Ciulla TA, Amador AG, Zinman B. Diabetic retinopathy and diabetic macular edema: pathophysiology, screening, and novel therapies. Diabetes Care 2003;26:2653–2664. 3. Antcliff RJ, Marshall J. The pathogenesis of edema in diabetic maculopathy. Semin Ophthalmol 1999;14:223–232. 4. Klein R, Klein BE, Moss SE, Cruickshanks KJ. The Wisconsin epidemiologic study of diabetic retinopathy. XV. The long-term incidence of macular edema. Ophthalmology 1995;102:7–16. 5. Otani T, Kishi S, Maruyama Y. Patterns of diabetic macular edema with optical coherence tomography. Am J Ophthalmol 1999;127:688–693. 6. Otani T, Kishi S. Tomographic findings of foveal hard exudates in diabetic macular edema. Am J Ophthalmol 2001;131:50–54. 7. Hee MR, Puliafito CA, Wong C, et al. Quantitative assessment of macular edema with optical coherence tomography. Arch Ophthalmol 1995;113:1019–1029. 8. Diabetic Retinopathy Clinical Research Network, Browning DJ, Glassman AR, Aiello LP, et al. Relationship between optical coherence tomography-measured central retinal thickness and visual acuity in diabetic macular edema. Ophthalmology 2007;114:525–536. 9. Tremolada G, Pierro L, De Benedetto U, et al. Macular micropseudocysts in early stages of diabetic retinopathy. Retina 2011;31:1352–1358. 10. Querques G, Lattanzio R, Querques L, et al. Enhanced depth imaging optical coherence tomography in type 2 diabetes. Invest Ophthalmol Vis Sci 2012;53:6017–6024. 11. Bolz M, Schmidt-Erfurth U, Deak G, et al. Optical coherence tomographic hyperreflective foci: a morphologic sign of lipid extravasation in diabetic macular edema. Ophthalmology 2009; 116:914–920. 12. Uji A, Murakami T, Nishijima K, et al. Association between hyperreflective foci in the outer retina, status of photoreceptor layer, and visual acuity in diabetic macular edema. Am J Ophthalmol 2012;153:710–717.
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13. Vujosevic S, Bini S, Midena G, et al. Hyperreflective intraretinal spots in diabetics without and with nonproliferative diabetic retinopathy: an in vivo study using spectral domain OCT. J Diabetes Res 2013;2013:491835. 14. Coscas G, De Benedetto U, Coscas F, et al. Hyperreflective dots: a new spectral-domain optical coherence tomography entity for follow-up and prognosis in exudative age-related macular degeneration. Ophthalmologica 2013;229:32–37. 15. Coscas G, Loewenstein A, Augustin A, et al. Management of retinal vein occlusion—consensus document. Ophthalmologica 2011;226:4–28. 16. Ogino K, Murakami T, Tsujikawa A, et al. Characteristics of optical coherence tomographic hyperreflective foci in retinal vein occlusion. Retina 2012;32:77–85. 17. Ota M, Nishijima K, Sakamoto A, et al. Optical coherence tomographic evaluation of foveal hard exudates in patients with diabetic maculopathy accompanying macular detachment. Ophthalmology 2010;117:1996–2002. 18. Fong AH, Li KK, Wong D. Choroidal evaluation using enhanced depth imaging spectral-domain optical coherence tomography in Vogt-Koyanagi-Harada disease. Retina 2011; 31:502–509. 19. Framme C, Schweizer P, Imesch M, et al. Behavior of SD-OCT-detected hyperreflective foci in the retina of antiVEGF-treated patients with diabetic macular edema. Invest Ophthalmol Vis Sci 2012;53:5814–5818. 20. Tang J, Kern TS. Inflammation in diabetic retinopathy. Prog Retin Eye Res 2011;30:343–358. 21. Kern TS. Contributions of inflammatory processes to the development of the early stages of diabetic retinopathy. Exp Diabetes Res doi:10.1155/2007/95103. 22. Joussen AM, Poulaki V, Le ML, et al. A central role for inflammation in the pathogenesis of diabetic retinopathy. FASEB J 2004;18:1450–1452. 23. Knowler WC, Bennett PH, Ballintine EJ. Increased incidence of retinopathy in diabetics with elevated blood pressure. A sixyear follow-up study in Pima Indians. N Engl J Med 1980;302: 645–650. 24. Bhargava M, Ikram MK, Wong TY. How does hypertension affect your eyes? J Hum Hypertens 2012;26: 71–83.
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iabetic retinopathy represents the most important cause of visual impairment in working-age individuals.1 In this vascular retinopathy, inner retinal capillary changes lead to the breakdown of the blood– retina barrier, and this alteration give rise to an increased vascular permeability and to diabetic macular edema (DME).2,3 The Wisconsin Epidemiologic Study of Diabetic Retinopathy reported an incidence of DME over a 10-year period between 13.9% and 25.4%, making it the first mechanism of vision loss in patients with nonproliferative diabetic retinopathy (NPDR).4
During the last decade, optical coherence tomography (OCT) has become a popular noninvasive optical imaging modality used widely to detect pathologic changes in the macular morphology and objectively measure the retinal thickness in patients affected by DME.5–10 Bolz et al11 studied diabetic retinopathy using spectral domain OCT (SD-OCT) and described for the first time in the literature the presence of hyperreflective foci (HRF) in patients with DME. Subsequently, Uji et al12 demonstrated that the presence of HRF in the outer retina was associated with disrupted external limiting membrane or inner/outer segment line, suggesting photoreceptor degeneration in patients with DME; these findings were also associated with a decreased visual acuity, showing the clinical relevance of the HRF. Recently, Vujosevic et al13 also described the migration of HRF from the inner to the outer retina layers during the diabetic retinopathy progression.
From the Department of Ophthalmology, San Raffaele Scientific Institute, University Vita-Salute, Milan, Italy. None of the authors have any financial/conflicting interests to disclose. Reprint requests: Luisa Pierro, MD, Department of Ophthalmology, San Raffaele Scientific Institute, Via Olgettina, 60, 20132 Milan, Italy; e-mail: [email protected]
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In this study, we investigate the presence of HRF in asymptomatic patients affected by Type 1 or Type 2 diabetes, separately, without clinically significant DME and visual impairment. The aim of this study was to analyze if HRF may be an early marker of diabetic retinopathy. Material and Methods In this noninvasive, observational, and prospective study, we recruited 71 eyes of 36 consecutive asymptomatic patients affected by Type 1 or Type 2 diabetes who presented to the Retina Service of the San Raffaele Department of Ophthalmology in Milan between December 2010 and January 2012. Inclusion criteria were 18 years or older of age, diagnosis of Type 1 diabetes at least 10 years before or Type 2 diabetes at least 5 years before, the presence of a very mild NPDR with microaneurysms only or the presence of a mild NPDR with microaneurysms plus hard exudates, cotton-wool spots, and/or mild retinal hemorrhages corresponding to Grades 20 and 35, respectively, on the Early Treatment of Diabetic Retinopathy Study (ETDRS) scale. Exclusion criteria were the presence of visual impairment (best-corrected visual acuity [BCVA], .0.1 logMAR), presence of hard exudates or retinal hemorrhages along the horizontal B-scan passing through the fovea, previous ocular surgery or laser treatment to the retina, refractive error .5 diopters, significant media opacities, evidence of DME on fundus biomicroscopy, sign of any other active retinal disease in the study eye (including the presence of an epiretinal membrane or vitreomacular traction syndrome). Two age- and sex-matched control groups were also included. All individuals were volunteers recruited specifically for this study. A younger control group (individuals younger than 40 years) was matched to the group of patients with Type 1 diabetes, and an older control group (individuals older than 40 years) was matched to the group of patients with Type 2 diabetes. The following clinicopathologic data were recorded for each subject (diabetic patients and control subjects): questions about general health status (including previous diagnosis of hypertension [HTN] and/or other cardiovascular diseases identified by their medical doctors or their cardiologists, and hemoglobin A1c [HbA1c] levels), measurement of BCVA (determined in all subjects with logMAR and ETDRS charts), intraocular pressure, fundus examination, color fundus photographs, and SD-OCT scans obtained using Spectral OCT SLO (OPKO/OTI, Ophthalmic Technologies Inc, Toronto, Canada). Linear scans of the macula were performed to evaluate
macular morphology, and a 128 · 512 raster scan to obtain central foveal thickness (CFT). The presence of HRF was defined as the presence of small focal hyperreflective areas scattered mainly in outer retinal layers but also spreading in all retinal layers observed in at least one SD-OCT scan14; HRF are invisible at clinical examination and fundus photography. The number of HRF was determinate considering the horizontal B-scan passing through the fovea. In the presence of microaneurysms or vessels visible in the fundus photography, the hyperreflective spots corresponding to these findings were excluded by the count of HRF. Two examiners well trained in OCT evaluation and masked to the purpose of the investigation (L.P. and R.L.) independently appraised the OCT images. Statistical analysis was performed using IBM (Armonk, NY) SPSS Statistics version 20. The Gaussian distribution of continuous variables was verified with the Kolmogorov-Smirnov test. Comparisons of mean HRF amount, CFT, BCVA, HbA1c level, age, and duration of the disease between control groups and Type 1 and Type 2 diabetic groups were performed using the Student’s t-test. Also comparison of mean HRF amount, age, and duration of the disease between Type 2 diabetic patients affected by HTN and Type 2 diabetic subjects without HTN was performed using the Student’s t-test. Pearson correlation analyses were performed to analyze the correlation between HRF amount, CFT, and HbA1c level. In all analyses, values of P , 0.05 were considered as statistically significant. We certify that all applicable institutional and governmental regulations concerning the ethical use of human volunteers were followed during this study. It was approved by the Institutional Review Board of the San Raffaele Scientific Institute. The study was performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki. All study patients provided written informed consent to the use of their personal data. Results Between December 2010 and January 2012, a total of 71 NPDR eyes of 36 consecutive asymptomatic diabetic patients were included for the current analysis. One eye of 1 patient affected by Type 1 diabetes was excluded for amblyopia. Seventeen and 19 patients (33 and 38 eyes) were affected by Type 1 and Type 2 diabetes, respectively. The mean age at diagnosis was 36.0 ± 8.1 years (median, 36; range, 23–45 years) in Type 1 group and 63.9 ± 8.7 years (median, 34; range, 48–76 years) in Type 2 group (P , 0.001). All patients were whites, 58.3% of them were men, and 41.7% were women. Systemic HTN was recorded in 14 patients affected by
HRF IN EARLY DIABETIC RETINOPATHY DE BENEDETTO ET AL
Type 2 diabetes. None of Type 1 diabetic patients was affected by HTN. Type 1 and Type 2 diabetic patients reported a mean duration of the disease of 19.2 ± 8.2 years and 10.6 ± 4.4 years, respectively (P , 0.001). Mean HbA1c level was 8.4 ± 1.6% (range, 5.9–11.8%) and 7.2 ± 0.7% (range, 6.1–8.4%) for Type 1 and Type 2 diabetic patients (P , 0.001). The subjects of control groups were selected homogenous for age and sex. A control group of 15 younger individuals (mean age, 32.3 ± 3.4 years; median, 33; range, 24–36 years) was compared with the group of Type 1 diabetic patients (P = 0.067). A control group of 13 older subjects (mean age, 57.1 ± 7.6 years; median, 52; range, 40–61 years) was compared with the group of Type 2 diabetic patients (P = 0.052). Mean BCVA was 0.00 ± 0.01 logMAR (range, 0–0.05 logMAR) for Type 1 diabetic group and 0.00 ± 0.02 logMAR (range, 0–0.1 logMAR) for Type 2 diabetic group (P = 0.075). Best-corrected visual acuity was 0 logMAR in all control patients. On SD-OCT examination, intraretinal HRF were present in all patients affected by Type 1 (Figure 1, B and C) and Type 2 (Figure 2, B and C) diabetes as scattered punctiform dots invisible at clinical examination, fundus photography, and in red-free images (Figures 1A and 2A). Patients affected by Type 1 and Type 2 diabetes had a mean of 7.5 ± 4.6 HRF (median, 7.0; range, 3–22) and 9.9 ± 4.5 HRF (median, 10.0; range, 4–21), respectively; HRF amount was then statistically different between Type 1 and Type 2 diabetic patients (P = 0.032). Subjects of control groups had a mean of 0.9 ± 0.8 HRF (median, 1.0; range, 0–3) and 1.7 ± 1.5 (median, 1.0; range, 0–5), respectively (P = 0.067). Moreover, comparing the diabetic groups (Types 1 and 2) with the respective control groups, HRF amount was significantly higher in the diabetic patients (P , 0.001 in both groups). Mean CFT was 234.5 ± 13.7 mm (184–297 mm) and 256.3 ± 12.7 mm (175–337 mm) for Type 1 and Type 2 diabetic patients, respectively (P = 0.061). In the 2
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control groups, mean CFT was lower than in diabetic groups (218.8 ± 14.3 mm [P = 0.034] and 222.8 ± 15.4 mm [P = 0.004], respectively). In both diabetic groups, no significant correlation was found between the number of HRF and the CFT (P = 0.495 and =0.145, respectively). Instead, the overall HRF amount in the 2 diabetic groups (Types 1 and 2), analyzed separately, was correlated significantly to the HbA1c levels (P , 0.001 and P = 0.016, respectively); patients with a poor quality glycometabolic control were associated with a larger presence of HRF. In the Type 2 diabetic group, there was a significant correlation between HRF amount and the presence of HTN. Patients affected by HTN had a higher number of HRF than subjects without HTN (11.2 ± 4.6 and 6.8 ± 2.7 HRF, respectively; P = 0.008). These 2 subgroups did not differ in HbA1c levels (7.15 ± 0.72 and 7.43 ± 0.49%, respectively; P = 0.382) and duration of the disease (11.1 ± 4.7 and 9.6 ± 3.7 years, respectively; P = 0.381). Patients affected by HTN were older than patients without HTN (mean age, 58.8 ± 8.9 and 66.0 ± 7.8 years, respectively; P = 0.025), but there was no significant correlation between age and number of HRF in these 2 subgroups (P = 0.531 and =0.233, respectively). Sex, patient age, and duration of the disease did not influence significantly the number of HRF within the retinal layers. Discussion Diabetic macular edema is a well-known cause of visual impairment in diabetic patients. In the last 2 decades, the role of OCT was stressed to analyze morphologic retinal changes and to understand physiopathologic mechanisms of DME. Thereby, Bolz et al11 described a new OCT retinal entity characterized by the presence of scattered, punctiform clinically invisible dots located in all retinal layers of patients affected by DME; these new findings were named HRF. The presence of these foci was also described
Fig. 1. Red-free image (A) does not show the presence of HRF. Spectral domain optical coherence tomography horizontal B-scan passing through the fovea (B and C) reveals the presence of 10 HRF (arrows) in a patient affected by Type 1 diabetes.
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RETINA, THE JOURNAL OF RETINAL AND VITREOUS DISEASES 2015 VOLUME 35 NUMBER 3
Fig. 2. Red-free image (A) without HRF. Spectral domain optical coherence tomography examination (B and C) showing the presence of 12 HRF (arrows) in a patient affected by Type 2 diabetes.
in other retinal diseases, such as age-related macular disease, retinal vein occlusions, and uveitis.14–18 Uji et al12 showed the clinical relevance of HRF, reporting that their presence in the outer retina layers decreases visual acuity of subjects with DME. Although the anatomical correspondence of this new finding is not clear, Bolz et al11 and Ota et al17 and Framme et al19 further suggested that HRF are a morphologic sign of accumulation of intraretinal fluid and lipid extravasation, and consequently precursors of hard exudates. This hypothesis may be supported by our results that showed a higher number of HRF in patients with the worst glycometabolic control than in subjects with lower HbA1c levels; patients with the worst glycometabolic control may have a greater lipid extravasation associated with a higher HRF amount. However, different etiologies have been suggested about the nature of HRF. Coscas et al14 interpreted the presence of these foci in patients affected by agerelated macular disease as activated microglia cells in a biological inflammatory reaction. This inflammatory reaction, which was well documented in the early stages of diabetic retinopathy,20–22 may support the hypothesis that HRF represent accumulation of inflammatory cells in diabetic retinopathy also. Using SD-OCT, in the current series, we investigated the presence of HRF in asymptomatic Type 1 and Type 2 diabetic patients affected by NPDR, without clinically significant DME and visual impairment (BCVA, 0–0.1 logMAR). The presence of HRF was detected in all diabetic patients, scattered in all retinal layers. To the best of our knowledge, no study was published comparing the different distribution of HRF in the two types of diabetes. We demonstrated that Type 1 diabetic patients had less HRF than individuals affected by Type 2 diabetes (P = 0.032). Consequently, the disease duration is not involved in the genesis of HRF considering that Type 1 diabetic patients reported a longer duration of the disease than subjects affected by Type 2 diabetes. Even the different age of the
patients cannot be considered a cause of HRF development because no significant difference in HRF amount was found between the control groups with the young and the old patients. Therefore, this different HRF amount in Type 1 and Type 2 diabetic patients may conceal itself in the dissimilar pathogenesis of the 2 types of diabetes. The presence of HTN, which was demonstrated as an important risk factor of development of diabetic retinopathy,23 may play an important role in the pathogenesis of HRF. Analyzing our data, we reported that the presence of HTN was significantly correlated with a higher number of HRF in Type 2 diabetic patients (P = 0.008); therefore, the presence of HTN may be considered an important cofactor in the development of HRF in individuals affected by Type 2 diabetes impairing the fluid resorption in the retinal layers.24 Also a poor quality glycometabolic control was associated with a larger presence of HRF, and this finding confirms again the importance of an optimal glycometabolic control in diabetes. The most important limitations of our study were the small sample size and the absence of a long-term followup. Further studies are on the way to investigate changes of the HRF amount and distribution over time, and their association with variations of glycometabolic status, CFT, and visual acuity. In conclusion, using SD-OCT, we demonstrated that there is a significant difference of the HRF amount in Type 1 and Type 2 diabetic patients. Our data suggested that this OCT finding might be a useful marker for the diagnosis of diabetic retinopathy in the early stage of the disease (i.e., asymptomatic NPDR patients without DME); these clinically invisible foci might also be useful as an additional marker for the glycometabolic status of the patients. Key words: diabetic retinopathy, hyperreflective dots, hyperreflective foci, SD-OCT.
HRF IN EARLY DIABETIC RETINOPATHY DE BENEDETTO ET AL
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