Table 1.
Characteristics of studies (n = 54).
| Study, Year Sample Size |
Diabetes Type | Age | Dietary Factor | Diet Evaluation | DR Outcome | DR Evaluation | Classification of DR | Quality Score |
|
|---|---|---|---|---|---|---|---|---|---|
| 3 Interventional studies | |||||||||
| Houtsmuller et al., 1979 n = 96 |
Any diabetes | Not stated | Saturated fat diet vs. unsaturated fat diet | NA | Incidence and progression | Fundus photograph | None, NPDR, PDR, PRP | High bias | |
| Howard-Williams et al., 1985 n = 149 |
Any diabetes | <66 | Saturated fat diet vs. unsaturated fat diet | NA | Incidence | Ophthalmologist examination | None, retinopathy | High bias | |
| Diaz-Lopez et al., 2015 n = 3614 |
T2DM | 55–80 | Mediterranean diet | NA | Incidence | Ophthalmologist examination | None, NPDR, PDR | Moderate bias | |
| 17 Prospective studies | |||||||||
| Horikawa et al., 2021 T2DM: 912 |
T2DM | 65–85 | Sodium | Validated food frequency questionnaire | Incidence | Ophthalmologist examination | Japanese Diabetes Complication Study Method | 10 | |
| Park et al., 2021 DR: 731 no DR: 1336 |
T2DM | DR: 53.1 (9.7) no DR: 55.6 (9.7) |
Glutamic acid and aspartic acid | 3-day food record with computer-aided nutritional analysis | Incidence | Fundus photograph, OCT | ETDRS | 10 | |
| Horikawa et al., 2017 n = 936 |
T2DM | 40–70 | Carbohydrates | Validated food frequency questionnaire | Incidence and progression | Ophthalmologist examination | International Classification System | 10 | |
| Horikawa et al., 2014 n = 978 |
T2DM | 40–70 | Sodium | Validated food frequency questionnaire | Incidence and progression | Ophthalmologist examination | International Classification System | 10 | |
| Tanaka et al., 2013 n = 978 |
T2DM | 40–70 | Vitamin C, Vitamin E, carotenoids, fruits, and vegetables, | Validated food frequency questionnaire + 24 h dietary recall | Incidence | Ophthalmologist examination | International Classification System | 10 | |
| Hainsworth et al., 2019 PDR: 379 no PDR: 1061 |
T1DM | PDR: 26 (21–32) no PDR: 27 (22–32) |
Alcohol beverage | Simple background questionnaire | Incidence and progression | Standardized stereoscopic seven-field fundus photographs | ETDRS | 9 | |
| Horikawa et al., 2019 n = 978 |
T2DM | 40–70 | Vitamin B6 | Validated food frequency questionnaire | Incidence | Mydriatic indirect ophthalmoscopic examination and slit lamp biomicroscopic fundus examination, with supplementation of fundus photography and fluorescein angiography | International Clinical Diabetic Retinopathy, DME Severity Scale | 9 | |
| Sala-Vila et al., 2016 n = 3482 |
T2DM | 55–80 | Long-chain omega-3 polyunsaturated fatty acids and oily Fish | Validated food frequency questionnaire | Incidence | Clinical and hospital records | None, NPDR, PDR | 9 | |
| Lee et al., 2010 n = 1239 |
T2DM | 55–81 | Alcohol | Self-report in a general questionnaire | Progression | Fundus photograph | Modified ETDRS | 9 | |
| Roy et al., 2010 n = 469 |
T1DM | Men: 26.7 (10.7) Women: 27.8 (10.8) |
MUFA, PUFA, oleic acid, protein, dietary fiber, carbohydrates, sodium, total calories, alcohol | Validated food frequency questionnaire | Incidence and progression | Fundus photograph | Modified ETDRS | 9 | |
| Moss et al., 1993 Young: 439 Older: 478 |
Any diabetes | 21–94 | Alcohol | Self-report in a general questionnaire | Incidence and progression | Fundus photograph | Modified ETDRS | 9 | |
| Gupta et al., 2020 Abstainers: 563 Consumers: 93 |
Not stated | Abstainers: 58.88 (9.45) Consumers: 58.41 (8.09) |
Alcohol | Questionnaire on alcohol consumption | Incidence and progression | Fundus photograph | ETDRS, Airlie House Classification | 8 | |
| Cundiff et al., 2005 n = 1412 |
T1DM | 13–39 | MUFA, PUFA, carbohydrates, protein, dietary fiber, sodium, alcohol, high calories | Dietary history interview | Progression | Fundus photograph | Modified ETDRS | 8 | |
| Young et al., 1984 n = 296 |
Any diabetes | 20–59 | Alcohol | Self-report in a general questionnaire | Incidence | Direct ophthalmoscopy | Modified ETDRS | 8 | |
| Ghaemi et al., 2021 T1DM with MD: 1669 T1DM without MD: 180 T2DM with MD: 15886 T2DM without MD: 4452 |
T1DM or T2DM | T1DM with MD: 50.63 (20.11) T1DM without MD: 51.40 (16.20) T2DM with MD: 59.78 11.00) |
Mediterranean diet | 14 item questionnaire | Incidence | Records from the National Program for Prevention and Control of Diabetes of Iran database | International Classification of Diseases, 10th Revision: E10.3, E11.3, E12.3, E13.3, and E14.3 | 7 | |
| Kadri et al., 2021 DR: 106 no DR: 155 |
T2DM | 57.73 (11.29) | Alcohol, antioxidants, milk, tea, coffee, fruits, meat, fish, egg, chapathi, rice, total Calories | 24 h dietary recall | Incidence and progression | Dilated fundus examination using slit-lamp biomicroscopy (90D), indirect ophthalmoscopy, fundus photography | Not stated | 7 | |
| Yan et al., 2019 n = 8122 |
Not stated | 57.2 (5.2) | Meat, dairy products, wholemeal bread, breakfast cereal, vegetables, fruit, and fruit juice | Self-administered questionnaire | Incidence and progression | Retinal photocoagulation from the Medicare Benefits Schedule data (note: used as a proxy for DR progression) | Not stated | 6 | |
| 29 Cross-Sectional Studies | |||||||||
| Fenwick et al., 2015 n = 395 |
T2DM | >18 | Alcohol | Validated food frequency questionnaire | Prevalence | Non-dilated fundus photography | ETDRS | 10 | |
| Ganesan et al., 2012 n = 1261 |
Any diabetes | >40 | Dietary fiber | Validated fiber questionnaire |
Prevalence | Dilated fundus photograph | Modified ETDRS | 10 | |
| Beulens et al., 2008 n = 1857 |
T1DM | 15–60 | Alcohol | Self-report in a general questionnaire | Prevalence | Dilated fundus photograph | None, Background, Proliferative | 10 | |
| Lee et al., 2022 DR: 270 no DR: 1080 |
T2DM | DR: 59.9(0.8) no DR: 58.6(0.4) |
Coffee | Validated food frequency questionnaire | Prevalence | Fundus photograph | ETDRS, modified Airlie House Classification | 9 | |
| Liu et al., 2021 DR: 378 no DR: 894 |
Not stated | >40 | Choline | 24 h dietary recall | Prevalence | Fundus photograph | Not stated | 9 | |
| Millen et al., 2016 n = 1305 |
Any diabetes | 45–65 | Vitamin D, fish, milk | Validated food frequency questionnaire | Prevalence | Fundus photograph | Modified Airlie House Classification | 9 | |
| Sahli et al., 2016 n = 1430 |
Any diabetes | 45–65 | Carotenoids (lutein) | Validated food frequency questionnaire | Prevalence | Non-dilated fundus photograph | ETDRS | 9 | |
| Mayer-Davis et al., 1998 n = 387 |
T2DM | 20–74 | Vitamin C, Vitamin E, beta-carotene | 24 h dietary recall | Prevalence | Dilated fundus photograph | Modified Airlie House Classification | 9 | |
| Moss et al., 1992 Young: 891 Older: 987 |
Any diabetes | 2–96 | Alcohol | Self-report in a general questionnaire | Prevalence | Fundus photograph | Modified Airlie House Classification | 9 | |
| Chen et al., 2022 DR: 696 no DR: 4515 |
Not stated | DR: 62.43 (11.79) no DR: 58.961 (12.421) |
Calcium and potassium | 24 h dietary recall | Prevalence | Fundus photograph | ETDRS | 8 | |
| She et al., 2020 DR: 119 No DR: 336 |
T2DM | DR: 63.2 (8.5) no DR: 65.4 (8.8) |
Antioxidants | 3-day food record | Prevalence | Fundus photograph | ETDRS | 8 | |
| Chua et al., 2018 n = 357 |
T2DM | 58 (52–62) | Fish | Validated food frequency questionnaire | Prevalence | Two-field digital retinal photographs | ETDRS, Airlie House Classification | 8 | |
| Fenwick et al., 2018 n = 609 |
T1DM or T2DM | 64.6(11.6) | Diet soft drink | Validated food frequency questionnaire | Prevalence | Two-field (macula and optic disc) dilated fundus photos were captured using a non-mydriatic retinal camera (fundus photography) | ETDRS for DR and the American Academy of Ophthalmology Scale for DME | 8 | |
| Granado-Casas et al., 2018 DR: 103 no DR: 140 |
T1DM | DR: 46.2(10.8) no DR: 42.1(10.3) |
Fat | Validated food frequency questionnaire | Prevalence | Ophthalmologist examination | International Clinical Classification System for diabetic retinopathy | 8 | |
| Thapa et al., 2018 DM: 1692 no DM: 168 |
Not stated | DM: 69.8 (7.4) no DM: 67.9 (6.7) |
Alcohol | Simple background questionnaire | Prevalence | Dilated fundus examination by a retina specialist | ETDRS | 8 | |
| Sasaki et al., 2015 n = 379 |
Any diabetes | >18 | Vitamin C, Vitamin E, beta-carotene, MUFA, PUFA, carbohydrates, protein | Validated food frequency questionnaire | Prevalence | Fundus photograph | Modified ETDRS | 8 | |
| Kumari et al., 2014 n = 353 |
Any diabetes | 21–95 | Coffee | Questionnaire on coffee consumption | Prevalence | Dilated fundus photograph | Modified Airlie House Classification | 8 | |
| Mahoney et al., 2014 n = 155 |
Any diabetes | >40 | Fruits and vegetables | Validated food frequency questionnaire | Prevalence | Non-dilated fundus photograph | ETDRS | 8 | |
| Harjutsalo et al., 2013 n = 3608 |
T1DM | Median age: 37.4 (28.9–46.8) | Alcohol | Self-report in a general questionnaire | Prevalence | History of laser photocoagulation | Severe DR vs. None | 8 | |
| Millen et al., 2004 n = 1353 |
Any diabetes | 45–65 | Vitamin C and Vitamin E | Validated food frequency questionnaire | Prevalence | Non-dilated fundus photograph | Modified Airlie House Classification | 8 | |
| Xu et al., 2020 DM: 614 no DM: 4667 |
Not stated | DM: 68.03(6.49) no DM: 67.88(6.64) |
Tea | Questionnaire on tea consumption | Prevalence | Fundus photograph | ETDRS | 7 | |
| Engelen et al., 2014 n = 1880 |
T1DM | 15–60 | Sodium | Estimated from urinary sodium excretion | Prevalence | Fundus photograph | None, NPDR, PDR | 7 | |
| Shalini et al., 2021 DR: 194 no DR: 150 Control: 151 |
T2DM | DR: 55.0(0.6) no DR: 56.0(0.9) Control: 54.0(0.9) |
Carotenoids | Validated raw food-based food frequency questionnaire with HPLC of plasma carotenoids | Prevalence | Fundus examination by indirect ophthalmoscopy, slit-lamp biomicroscopy, fundus fluorescein angiography | ETDRS | 6 | |
| Alsbirk et al., 2021 T1DM: 50 T2DM: 460 |
T1DM or T2DM | T1DM: 44.5 (13–87) T2DM: 66 (27–92) |
Fish food, PUFAs supplements | Questionnaire of self-reported dietary history | Prevalence | Fundus photograph | International Clinical Diabetic Retinopathy, DME Severity Scale | 6 | |
| Mirghani et al., 2021 DR: 66 no DR: 134 |
Not stated | 50.74(13.51) | Diet sugar-free carbonated soda beverage | Validated food frequency questionnaire | Prevalence | Fundus examination | Not stated | 5 | |
| Kawasaki et al., 2018 NPDR: 83 no NPDR: 280 |
T1DM or T2DM | NPDR: 58.9 no NPDR: 55.6 |
Alcohol | Simple background questionnaire | Prevalence | Fundus findings from clinic and hospital records | International Clinical Diabetic Retinopathy | 5 | |
| Lugo-Radillo et al., 2013 n = 88 |
Any diabetes | No DR: 58.50 (1.11) DR: 56.82 (1.65) |
Fruits and vegetables | Oral questionnaire on fruit and vegetable consumption | Prevalence | Ophthalmologist examination | International Classification System | 5 | |
| Roy et al., 1989 n = 34 |
Any diabetes | DR: 37.9 (12) No DR: 37.7 (9) |
MUFA, PUFA, carbohydrates, protein, dietary fiber | 3-day food record | Prevalence | Fundus photography | Modified Airlie House Classification | 5 | |
| Acan et al., 2018 DME: 63 no DME: 350 |
T1DM or T2DM | DME: 58.86 (11.27) no DME: 56.03 (11.95) |
Alcohol | Simple background questionnaire | Prevalence | Dilated fundoscopy by ophthalmologists, central macular thickness analysis with OCT | ETDRS, OCT central macular thickness ≥ 250 μm | 3 | |
| 5 Case–control Studies | |||||||||
| Alcubierre et al., 2016 Case: 146 Control:148 |
T2DM | 40–75 | MUFA, PUFA, oleic acid, carbohydrates, protein, dietary fiber | Validated food frequency questionnaire | Prevalence | Ophthalmologist examination | International Classification System | 10 | |
| Zhang et al., 2019 DM with DR: 43 DM without DR: 43 Controls: 40 |
T2DM | DM with DR: 59 (49–66) DM without DR: 53 (44–65) Controls: 54(47–67) |
Vitamin A | Validated food frequency questionnaire with HPLC of plasma retinol | Prevalence | Not stated | Not stated | 8 | |
| Alcubierre et al., 2015 Case: 139 Control:144 |
T2DM | No DR: 58.1 (10.3) DR: 60.3 (8.9) |
Vitamin D, calcium | Validated food frequency questionnaire | Prevalence | Ophthalmologist examination | International Classification System | 8 | |
| Ma et al., 2014 Case:100 Control:100 |
T2DM | >18 | Green tea | Questionnaire on tea consumption | Prevalence | Fundus photograph | ETDRS | 8 | |
| Giuffre et al., 2004 Case:45 Control:87 |
Any diabetes | >40 | Alcohol | Self-report in a general questionnaire | Prevalence | Direct ophthalmoscopy and fundus photograph | ETDRS | 7 | |
DR—Diabetic retinopathy, DME—Diabetic macular edema, ETDRS—Early treatment diabetic retinopathy study, HPLC—High-performance liquid chromatography, MD—Mediterranean diet, MUFA—Monounsaturated fatty acid, NPDR—Non-proliferative diabetic retinopathy, OCT—Optical coherence tomography, PDR—Proliferative diabetic retinopathy, PRP—Pan retinal photocoagulation, PUFA—polyunsaturated fatty acid, DM—Diabetes Mellitus.