We evaluated 285 eyes diagnosed with PDR from 165 diabetic patients of whom 40 eyes belonged to 21 T1DM patients [14%] and 245 eyes were from 144 T2DM patients [86%]. There were 197 eyes of 113 males [69%] and 88 eyes of 52 females [31%]. All patients proceeded from the reference population of University Hospital Sant Joan, Tarragona, Spain.
This study is part of our line of research on diabetic retinopathy described elsewhere.4
We conducted a retrospective review of all diabetic patients with PDR who attended for treatment at our hospital.
- All patients with T1DM or T2DM diagnosed with PDR in our health care areas. The minimum duration of follow up required was 7 years.
- Patients with any previous type of retinal vascular occlusion.
- Patients with proliferative retinopathy of causes other than diabetes.
- Patients who had previously been operated on for other retinal conditions.
All eyes were initially assessed by fundus examination, optical coherence tomography [OCT] and fluorescein angiography [FA] to ensure the presence of PDR and to classify the type of DME if no vitreous haemorrhage was present, in which case the diagnosis was made after pars plana vitreoretinal surgery.
We conducted a comprehensive review of the medical report documentation for all patients, including age, gender, type of DM, DM treatment [insulin or oral antidiabetic drugs], DM duration and blood pressure. We recorded the body mass index [BMI], estimated glomerular filtration rate [eGFR], the existence of urine albumin to creatinine ratio [UACR] and the mean HbA1c and haemoglobin levels, measured at one year before having been diagnosed with PDR and through the whole study period. We identified the patients treated with anticoagulant or antiplatelet drugs and those diagnosed with chronic pulmonary obstructive disease [CPOD]. Furthermore, we quantified the cigarette consumption in pack-years. Former smokers were those who don’t smoke now but have smoked at some time within the last 10 years and non-smokers were those who had never smoked or have not smoked at any time within the last 10 years, based on Akter et al.11 Finally, we identified the patients who had suffered from polineuropathy, stroke, ischemic cardiopathy and ischemia in the lower limbs.
All eyes were evaluated for the existence and type of DME using the SD-OCT [TOPCON 3D OCT–2000]. We classified the patients into three groups:
- No DME
- Focal or multifocal DME: whether one or multiple areas of exudative microaneurysms were identified along with increased retinal thickness.
- Diffuse DME [whether more than 75% of the fluorescein leakage observed was not related to the presence of microaneurysms].
All eyes were classified into two subgroups depending on whether or not the vitreous was attached to the posterior pole. In addition, we recorded the patients treated with anti-VEGF drugs.
We classified all the eyes with PDR into three groups depending on their vitreous haemorrhage behaviour: the first group were eyes which had never bled [NVH], the second group were eyes that had bled just once [SVH] and the third group were eyes which had bled more than once [RVH]. In addition, we further classified them into two subgroups, depending on the time of recurrence. Early recurrence was considered within 30 days after pars plana vitreoretinal surgery and late recurrence after this period.
The severity of all vitreous haemorrhage episodes was scored on a 5-point scale according to Lieberman et al16 : Grade 0 (no vitreous haemorrhage); Grade 1 (minimal vitreous haemorrhage, optic disk and retinal vessels were clearly visible); Grade 2 (mild vitreous haemorrhage, most of the optic disk and retinal vessels were visible); Grade 3 (moderate vitreous haemorrhage, optic disk or retinal vessels were barely visible); Grade 4 (severe vitreous haemorrhage, too dense to allow visualization of the optic disk).
In our study, those eyes which showed vitreous haemorrhage of grade 3 or 4 and did not clear after 2 months, underwent vitreoretinal surgery along with aditional retinal laser photocoagulation.
Finally, all eyes were classified into another two subgroups according to whether or not patients had previously undergone pan-retinal photocogulation before the beginning of the study period.
Data was analysed using the SPSS software package, version 25.0. In this study, the dependent variable was the presence of recurrent vitreous haemorrhage. The independent variables were: age, gender, DM duration, type of DM, type of DM treatment, arterial hypertension, existence of UACR, eGFR, mean HbA1c, mean haemoglobin, pan-retinal photocoagulation status, smoking status and cigarette consumption [pack-years], the presence of CPOD, treatment with anti-VEGF intravitreal injections and treatment with anticoagulant or antiplatelet drugs.
A descriptive statistical analysis was made of the quantitative data. For qualitative data, we used the analysis of frequency and percentage in each category. The normal data curve was evaluated using the Kolmogorov-Smirnov test. Differences between quantitative variables with normal distribution were examined using Student’s t-test, in other cases we used the Mann-Whitney U test. To compare the mean of one quantitative variable in more than two groups of patients with normal distribution we used one-way ANOVA. Otherwise, the Kruskal-Wallis test was used. Inferential analysis for qualitative data was carried out using the chi-squared table and the determination of the Phi test. To correlate two continuous quantitative variables with normal distribution we used Pearson’s parametric coefficient. For categorical variables we used Spearman’s coefficient. We used the logistic regression analysis to study which independent variables were significantly related to the presence of RVH. Finally, we used the Kaplan-Meier estimator to compare the probability of occurence of RVH among smokers, former smokers and non-smokers in a specific interval of time. P<0.05 was considered statistically significant.