Table 2.

Summary of the important results of some of the studies done on diabetic retinopathy.

Study	Recommendations
DRS	(1)Prompt PRP for eyes with high risk characteristics. (2)NVD is the strongest predictor for severe visual loss and the second strongest predictor was the extent of retinal hemorrhage/microaneurysm (3)Photocoagulation reduces the risk for ocular hypertension apparently by preventing neovascular glaucoma (4)Focal laser treatment for macular edema before PRP and divide PRP in multiple sessions and decrease the intensity of the burn (5)Risk factors for SVL despite PRP during 5 years after randomization: (a) increasing NVD (most important factor), (b) increasing retinal hemorrhages/microaneurysms, (c) increasing retinal elevation (detachment), (d) increasing proteinuria, (e) increasing hyperglycemia, (f) decreasing treatment density
ETDRS	(1)Focal/grid laser photocoagulation reduced the risk of moderate vision loss (that is, a doubling of the visual angle) from clinically significant macular edema (2)In patients with type 2 diabetes, it is especially important to consider scatter photocoagulation at the time of the development of severe non-proliferative or early proliferative retinopathy (3)Technique for photocoagulation for PDR: Full PRP include 1200 or more of 500μ burns separated from each other by one half burn width at 0.1 s duration. Confluent treatment of flat NVE (4)Fundus photographic risk factors for progression of diabetic retinopathy: a. Severity of intra-retinal microvascular abnormalities, b. Severity of retinal hemorrhages/microaneurysms, c. Severity of venous beading, d. NOT soft exudates (cotton wool spots) (5)Fluorescein angiographic (FA) risk factors for progression of diabetic retinopathy: a. Fluorescein leakage (particularly the diffuse type), b. Capillary loss and dilation, c. Arteriolar abnormalities (e.g., focal narrowing, pruning, staining), d. FA risk factors offer increased power to predict progression of DR, but do not offer clinically important information over clinical exam and color photography (6)Pars plana vitrectomy in the ETDRS for diabetics with vitreous hemorrhage and retinal detachment (7)Risk factors for high risk PDR and severe visual loss (SVL): (a) higher glycosylated hemoglobin, (b) history of diabetic neuropathy, (c) lower hematocrit, (d) elevated triglycerides, (e) lower serum albumen, (f) type 1 diabetes (8)Transient decrease in accommodative amplitude of 1/3 diopter measured at the 4 month exam following scatter photocoagulation (P < 0.001) (9)Causes of severe visual loss (in decreasing order of frequency): (a) vitreous/pre-retinal hemorrhage (despite vitrectomy), (b) macular edema, (c) macular pigmentary change, (d) retinal detachment, (e) narrow or opaque arteries (i.e., ischemia), (f) risk factors for persistent severe visual loss: elevated glycosylated hemoglobin and elevated cholesterol
DRVS	(1)Early Vitrectomy for acute, severe vitreous hemorrhage (VH) in diabetic retinopathy especially significant for patients with type 1 diabetes mellitus showed clear cut advantage (2)Early vitrectomy for severe PDR with useful vision. The advantages of early vitrectomy increased with increasing severity of NV (3)Early vitrectomy for severe vitreous hemorrhage in DR. Four years results indicates that eyes with severe VH in patients with type 1 diabetes mellitus benefit from early vitrectomy
DCCT 1993	Long time result in tight hyperglycemic control showed significantly reduced the progression of diabetic retinopathy
UKPDS 1998	Tight glycemic control showed 34% reduction in progression of DR and 47% in reducing the risk of deterioration of vision

DRS = diabetic retinopathy study, ETDRS = early treatment diabetic retinopathy study, DRVS = diabetic retinopathy vitrectomy study, DCCT = diabetes control complication trials, UKPDS = United Kingdom prospective diabetes study (Aiello et al., 1994, 2010; Pouvlaki et al., 2004; Diabetic Retinopathy Study Research Group, 1976, 1985; Patz and Smith, 1991; Diabetes Control and Complications Trial Research Group, 1993, 1995, 1998; Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Research Group, 2000; Anon., 1995; Writing Team for the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Research Group, 2002; UK Prospective Diabetes Study Group, 1998a,b; Egger et al., 1997; American Diabetes Association, 2004; Rand et al., 1985; Kaufman et al., 1987, 1989; Ferris et al., 1987; Ferris, 1996; Early Treatment Diabetic Retinopathy Study Research Group, 1991a,b,c,d,e; Davis et al., 1998; Braun et al., 1995; Fong et al., 1999; Diabetic Retinopathy Vitrectomy Study Research Group, 1985, 1988a,b; DRVS, 1985; Flynn et al., 1992; Chew et al., 1995; Suzuma et al., 2001; Flynn et al., 1992; Chew et al., 1995), PRP = panretinal photocoagulation, NVD = neovascularization on the disk, NVE = neovascularization elsewhere in the retina, SVL = severe visual loss.