Epidemiology and dynamics of development
The development of retinal damage directly correlates with the duration of diabetes mellitus. This is a classic late complication that requires time for structural changes in the vascular bed to form. Statistics clearly demonstrate this dependence:
- At disease onset: signs of fundus damage are detected in only a small fraction of patients — about 3%.
- After 10 years: as metabolic disorders progress, pathological changes are recorded in 40–45% of patients.
- After 15 years: specific retinal damage is diagnosed in almost every patient — in 97% of cases.
Understanding this chronology is critical for clinical practice, as it underscores the covert, latent nature of microvascular defect accumulation and dictates the need for regular screening.
Key links in pathogenesis
The formation of diabetic eye damage is based on two fundamental pathophysiological processes:
- Microangiopathy. Acts as the triggering factor. There is systemic damage to small blood vessels, primarily arterioles supplying the ocular tissues and optic nerve structures.
- Hypoxia. Due to impaired adequate blood supply, ocular tissues (especially the retina) begin to experience severe oxygen deprivation.
It is this escalating oxygen deficit that triggers a cascade of compensatory yet ultimately destructive reactions leading to severe anatomical defects.
Non-proliferative (background) stage
Two main forms of the disease are distinguished. The first is non-proliferative retinopathy (also referred to as background or simple). This is the most common variant, accounting for over 90% of all diagnosed cases.
The pathogenesis of this stage involves a sequential chain of microvascular catastrophes:
- Initially, the permeability of microvessel walls pathologically increases.
- The fluid component of blood leaks into tissues, leading to the development of exudates.
- The walls of arterioles and venules lose elasticity, and specific outpouchings—microaneurysms—form on them.
- Microthrombi form within the lumen of damaged capillaries, which inevitably results in vascular occlusion (blockage).
- Due to the fragility of the vascular wall, microhemorrhages occur in the retinal tissue and vitreous body.
Vascular occlusion by microthrombi exacerbates local ischemia, closing the vicious cycle of pathogenesis. It is at this stage that a serious risk of blindness develops.
Proliferative stage
The second form is proliferative retinopathy. It is significantly less common, occurring in approximately 10% of patients, but is characterized by an extremely severe clinical course. This stage is a direct evolutionary continuation of the non-proliferative stage when adaptive reserves are depleted.
The key sign is neovascularization—the process of pathological formation of new microvessels. This mechanism is actively stimulated by tissue hypoxia: the retina, attempting to compensate for the lack of oxygen, initiates the growth of new capillaries. However, these vessels are morphologically defective and grow directly into the vitreous body.
In areas of massive hemorrhages from these fragile vessels, connective tissue proliferation is triggered, resulting in the formation of coarse scars. The final and most dramatic point of this cascade is retinal detachment, which occurs in areas of the largest hemorrhages and scarring, leading to irreversible vision loss.
Briefly: answers to topical questions
What are the main risk factors for developing diabetic retinopathy, apart from the duration of diabetes?
According to sources, risk factors for DM complications, including diabetic retinopathy, aside from long disease duration, include:
- older age and puberty;
- smoking;
- arterial hypertension;
- dyslipidemia;
- family history of complications;
- obesity;
- sedentary lifestyle.
Additionally, to prevent the onset and progression of DR and DME, control of modifiable risk factors is recommended: glycemic control, blood pressure, and lipid profile; during history-taking, attention is paid to the degree of DM compensation (glucose level, HbA1c), the presence of hypertension, and lipid metabolism parameters.
What ophthalmological examination methods are used to diagnose diabetic retinopathy?
To diagnose diabetic retinopathy, a set of standard and additional instrumental ophthalmological examination methods is applied.
The main methods include:
- Visometry — determination of visual acuity;
- Ophthalmotonometry — measurement of intraocular pressure;
- Biomicroscopy — examination of the anterior segment of the eye;
- Ophthalmoscopy — examination of the fundus with a dilated pupil (using a wide-field indirect ophthalmoscope).
Additional methods to verify the diagnosis:
- Optical coherence tomography (OCT) and OCT angiography;
- Fluorescein angiography (FA) of the eye — to assess retinal blood flow;
- Computer perimetry;
- Ultrasound of the eyeball;
- Color Doppler ultrasound of ocular vessels.
What modern treatment methods exist for the proliferative stage of diabetic retinopathy?
For the proliferative stage of diabetic retinopathy, sources indicate the following treatment options:
- Laser retinal photocoagulation; panretinal laser photocoagulation (PRP) is performed under conditions of drug-induced mydriasis. The goals indicated for PRP are suppression of VEGF expression, prevention of neovascularization, and stabilization or improvement of corrected visual acuity.
- Intravitreal administration of angiogenesis inhibitors.
- Vitrectomy as surgical treatment.
How is diabetic retinopathy classified according to current clinical guidelines?
According to current guidelines, the most comprehensive classification of diabetic retinopathy is the ETDRS scale, which divides the disease into stages depending on the severity of changes.
The following stages are distinguished:
- Non-proliferative — can be minimal, mild, or moderate;
- Preproliferative — graded as severe non-proliferative;
- Proliferative — categorized into states with low and high risk of vision loss;
- Advanced (terminal) — far-advanced complications.
An important addition is the assessment for diabetic macular edema (DME), which is classified as center-involving or non-center-involving and can develop at any stage of the disease.
To remember the cascade of the non-proliferative stage, use the mnemonic "PEA-TC": Permeability (increases) → Exudates (leak out) → Aneurysms (balloon) → Thrombi (occlude) → Clots/Hemorrhages (destroy).
Class and exam questions
Why do new vessels form in diabetic retinopathy if this ultimately leads to blindness?
Neovascularization is the body's desperate attempt to compensate for escalating retinal hypoxia. However, these new capillaries grow into the vitreous body, possess extremely fragile walls, and rupture easily, leading to massive hemorrhages and subsequent scarring.
At what duration of diabetes mellitus does retinal damage become practically inevitable?
According to epidemiological data, specific retinal changes are detected in 97% of patients 15 years after the onset of the disease. For comparison, at the onset of the disease, this figure is only about 3%.
What is the fundamental difference between the non-proliferative and proliferative stages?
The non-proliferative stage (more than 90% of cases) occurs within existing vessels: their permeability increases, and microaneurysms and microthrombi develop. The proliferative stage (about 10%) is characterized by the growth of brand-new, pathological microvessels beyond the retina into the vitreous body.
What is the main cause of retinal detachment in this disease?
Retinal detachment occurs in the proliferative stage in areas of major hemorrhages. The spilled blood organizes with the formation of dense connective tissue scars that mechanically pull and eventually detach the retina from the underlying tissues.
What else to study on this topic
- Mechanisms of microaneurysm formation in arterioles and venules
- Pathogenesis of diabetic microangiopathy: biochemical fundamentals
- The role of tissue hypoxia in stimulating angiogenesis factors
- Types of exudates in retinal lesions
- Vitreous scarring processes following hemorrhages
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