Table 1. Characteristics of studies (n = 31).
| Author, year | Sample Size | Diabetes | Age | Dietary Component | Dietary Assessment | DR outcome | Method of Diagnosing DR | DR Classification | Quality |
|---|---|---|---|---|---|---|---|---|---|
| Interventional Studies (n = 3) | |||||||||
| Houtsmuller, 1979 | 96 | Any Diabetes | n.a. | Saturated Fat vs Unsaturated Fat | n.a. | Progression & incidence | Fundus Photography | None, NPDR, PDR, PRP | High Bias |
| Howard-Williams, 1985 | 149 | Any diabetes | <66 | Saturated Fat vs Unsaturated Fat | n.a. | Incidence | Ophthalmologist Examination | None, Retinopathy | High Bias |
| Diaz-Lopez, 2015 | 3614 | T2DM | 55–80 | Med Diet | n.a. | Incidence | Ophthalmologist Examination | None, NPDR, PDR | Moderate Bias |
| Prospective Studies (n = 9) | |||||||||
| Young, 1984 | 296 | Any Diabetes | 20–59 | Alcohol | Self Report in general questionnaire | Incidence | Direct Ophthalmoscopy | Modified ETDRS | 8 |
| Moss, 1993 | Young: 439 Older: 478 |
Any Diabetes | 21–94 | Alcohol | Self Report in general questionnaire | Incidence & progression | Fundus Photography | Modified ETDRS | 9 |
| Roy, 2010 | 469 | T1DM | NR* | MUFA, PUFA, Oleic Acid, Protein, Dietary Fibre, carbohydrates, sodium, high caloric | Validated FFQ | Progression & Incidence | Fundus Photography | Modified ETDRS | 9 |
| Cundiff, 2005 | 1412 | T1DM | 13–39 | MUFA, PUFA, Carbohydrates, Protein, Dietary Fibre, Sodium, Alcohol, High Calories | Dietary History Interview | Progression | Fundus Photography | Modified ETDRS | 8 |
| Lee, 2010 | 1239 | T2DM | 55–81 | Alcohol | Self Report in general questionnaire | Progression | Fundus Photography | Modified ETDRS | 9 |
| Tanaka, 2013 | 978 | T2DM | 40–70 | Fruit & vegetables, Vitamin C, Vitamin E, Carotenoids | Validated FFQ + 24 Hr Dietary Recall | Incidence | Ophthalmologist Examination | International Classification System | 10 |
| Horikawa, 2014 | 978 | T2DM | 40–70 | Sodium | Validated FFQ | Progression& incidence | Ophthalmologist Examination | International Classification System | 10 |
| Horikawa, 2017 | 978 | T2DM | 40–70 | Carbohydrates | Validated FFQ | Progression & Incidence | Ophthalmologist Examination | International Classification System | 10 |
| Sala-Vila, 2016 | 3482 | T2DM | 55–80 | PUFA (LCw3) & Oily Fish | Validated FFQ | Incidence | Clinical and Hospital Records | None, NPDR, PDR | 9 |
| Case-Control Studies (n = 4) | |||||||||
| Giuffre, 2004 | Cse = 45 Ctr: 87 |
Any Diabetes | >40 | Alcohol | Self Report in general questionnaire | Prevalence | Direct Opthalmoscopy + Fundus Photography | ETDRS | 7 |
| Ma, 2014 | Cse: 100 Ctr: 100 |
T2DM | >18 | Green Tea | Questionnaire on tea consumption | Prevalence | Fundus Photography | ETDRS | 8 |
| Alcubierre, 2015 | Cse: 139 Ctr: 144 |
T2DM | NR | Vitamin D, calcium | Validated FFQ | Prevalence | Ophthalmologist Examination | International Classification System | 8 |
| Alcubierre, 2016 | Cse: 146 Ctr: 148 |
T2DM | 40–75 | MUFA, PUFA, Oleic Acid, Carbohydrates, Protein, Dietary Fibre, | Validated FFQ | Prevalence | Ophthalmologist Examination | International Classification System | 10 |
| Cross-Sectional Studies (n = 15) | |||||||||
| Roy, 1989 | 34 | Any Diabetes | NR | MUFA, PUFA, Carbohydrates, Protein, Dietary Fibre | 3-d Food Record | Prevalence | Fundus Photography | Modified Airlie House Classification | 5 |
| Moss, 1992 | Young: 891 Older: 987 |
Any Diabetes | 2–96 | Alcohol | Self Report in general questionnaire | Prevalence | Fundus Photography | Modified Airlie House | 9 |
| Mayer-Davis, 1998 | 387 | T2DM | 20–74 | Vitamin C, E & Beta-Carotene | 24 Hr Dietary Recall | Prevalence | Dilated Fundus Photography | Modified Airlie House Criteria | 9 |
| Millen, 2004 | 1353 | Any Diabetes | 45–65 | Vitamin C & E | Validated FFQ | Prevalence | Non-Dilated Fundus Photography | Modified Airlie House | 8 |
| Beulens, 2008 | 1857 | T1DM | 15–60 | Alcohol | Self Report in general questionnaire | Prevalence | Dilated Fundus Photography | None, background, proliferative | 10 |
| Ganesan, 2012 | 1261 | Any Diabetes | >40 | Dietary Fibre | Validated Fibre Questionnaire | Prevalence | Dilated Fundus Photography | Modified ETDRS | 10 |
| Harjutsalo, 2013 | 3608 | T1DM | NR | Alcohol | Self Report in general questionnaire | Prevalence | History of Laser Photocoagulation | Severe DR Vs None | 8 |
| Lugo-Radillo, 2013 | 88 | Any Diabetes | NR | Fruit & Vegetables | Oral Questionnaire on F&V Consumption | Prevalence | Ophthalmologist Examination | International Classification System | 5 |
| Mahoney, 2014 | 155 | Any Diabetes | >40 | Fruit & Vegetables | Validated FFQ | Prevalence | Undilated Fundus Photography | ETDRS | 8 |
| Engelen, 2014 | 1880 | T1DM | 15–60 | Sodium | Estimated from Urinary Sodium Excretion | Prevalence | Fundus Photography | None, NPDR, PDR | 7 |
| Kumari, 2014 | 353 | Any Diabetes | 21–95 | Coffee | Questionnaire on coffee consumption | Prevalence | Dilated Fundus Photography | Modified Airlie House Classification | 8 |
| Sasaki, 2015 | 379 | Any Diabetes | >18 | Vitamin C, E, B-Carotene, MUFA, PUFA, carbohydrates, protein | Validated FFQ | Prevalence | Fundus Photography | Modified ETDRS | 8 |
| Fenwick, 2015 | 395 | T2DM | >18 | Alcohol | Validated FFQ | Prevalence | Undilated Fundus Photography | ETDRS | 10 |
| Millen, 2016 | 1305 | Any Diabetes | 45–65 | Vitamin D, Fish, Milk | Validated FFQ | Prevalence | Fundus Photography | Modified Airlie House | 9 |
| Sahli, 2016 | 1430 | Any Diabetes | 45–65 | Carotenoids (Lutein) | Validated FFQ | Prevalence | Non-Dilated Fundus Photography | ETDRS | 9 |