01OverviewDefinition, clinical context and the essential points that orientate the chapter.
The retina provides a visible record of microvascular injury, but it is not a complete measure of systemic vascular health. Diabetes can damage capillary walls and impair retinal perfusion; hypertension can alter arterioles and, when severe, overwhelm vascular regulation. A patient may have both processes. Reading a retinal image therefore requires attention to the pattern, current visual function, blood pressure and previous eye findings.
Clinical care has three linked purposes: identify a current threat to sight, reduce the systemic factors contributing to future damage, and ensure that the person reaches the correct surveillance service. A screening photograph, a diabetes review and a hospital retinal appointment answer different questions. Clear communication prevents someone with active eye disease from being left waiting for a routine screening invitation.
Key points
- Diabetic retinal damage can be clinically important before the person notices any visual change.
- Microvascular leakage and capillary closure produce different retinal findings and may coexist in the same eye.
- Hypertensive and diabetic changes overlap; examination findings must be interpreted alongside measured blood pressure and systemic assessment.
- Diabetic macular oedema threatens central function, while proliferative disease can cause bleeding and tractional complications.
- England's screening programme invites eligible people aged twelve or over, with two-year intervals after two successive tests without retinopathy.
- Symptomatic eye disease needs clinical assessment even when screening was recently reassuring.
- Coordinate major glycaemic treatment changes with ophthalmology when retinopathy could worsen during a rapid HbA1c reduction.
02AetiologyUnderlying causes, associations and risk factors, with why each one matters.
Cumulative metabolic exposure
Sustained hyperglycaemia and the duration of diabetes contribute to retinal vascular injury. Individual susceptibility, kidney disease and other systemic factors influence the likelihood and course of clinically important retinopathy.
Raised arterial pressure
Longstanding hypertension affects retinal arterioles, while a severe rise can damage the retinal circulation more acutely. Coexisting diabetes complicates interpretation because both disorders can produce haemorrhagic and ischaemic retinal signs.
03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.
- 1Leakage from damaged capillaries
Loss of vascular barrier integrity permits fluid and circulating material to enter retinal tissue. Microaneurysms, haemorrhages and lipid deposits reflect different consequences of this injury, while macular fluid can interfere with detailed central vision.
- 2Capillary closure and angiogenic drive
Non-perfused retina produces signals that encourage abnormal new vessel growth. These vessels are fragile and may be associated with fibrous tissue, creating risks of vitreous bleeding, traction and secondary angle neovascularisation.
- 3Arteriolar injury and acute pressure stress
Chronic pressure exposure can change arteriolar calibre and appearance. More severe vascular injury can produce retinal haemorrhage, local nerve-fibre ischaemia and disc swelling, requiring interpretation in the context of the systemic presentation.
04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.
Distinguish slowly worsening reading vision from an abrupt haze, fixed shadow or sudden loss. Record each eye's function separately and ask about previous laser, injections and surgery. A recent normal screening result only describes the examination at that time.
Describe the location of haemorrhages, hard exudates, cotton-wool spots, vascular changes and any new vessels. Isolated labels can be misleading: cotton-wool spots reflect local nerve-fibre ischaemia and are not unique to diabetes or hypertension.
Obtain a properly measured blood pressure and assess for symptoms of acute target-organ injury. Review diabetes duration, current HbA1c, kidney function, smoking and relevant treatment changes. The severity of one retinal sign cannot independently establish the duration or severity of systemic disease.
Ask whether the patient attends screening, digital surveillance or a hospital eye service and when the next review is due. Confirm who receives results and who will act on them. Difficulty attending or understanding letters is a remediable care problem, not evidence that the eye disease is unimportant.
05InvestigationsWhat to request, why it matters and how to interpret it.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Visual acuity and appropriate retinal examinationFirst step - Why
- Identify present visual impairment and clinically important retinal pathology.
- Interpretation and limitations
- Assess both eyes with correction and examine the retina through an adequate view. Preserved acuity can coexist with peripheral proliferative disease; an ungradable photograph requires an alternative assessment rather than an assumed normal result.
- 02
Macular OCT when central disease is suspected - Why
- Assess retinal fluid and structural explanations for impaired central vision.
- Interpretation and limitations
- OCT identifies macular thickening and other structural changes, but does not measure the whole retinal circulation or replace examination for proliferative disease. A dry-looking scan does not exclude macular ischaemia.
- 03
Blood pressure and systemic target-organ assessment - Why
- Determine whether retinal findings accompany a hypertensive emergency.
- Interpretation and limitations
- NICE links severe clinic hypertension with retinal haemorrhage or papilloedema to same-day specialist assessment. Renal tests, urinalysis, ECG and other investigations are selected within the systemic assessment; do not delay urgent referral to complete a routine outpatient panel.
- 04
Longitudinal metabolic and renal information - Why
- Inform retinal risk, systemic treatment and coordination between services.
- Interpretation and limitations
- HbA1c trends, renal function and the timing of treatment changes are more useful than an isolated glucose value. Communicate a planned intervention likely to cause a rapid substantial HbA1c fall so ophthalmology can assess the retina before and after the change.
06Differential diagnosisRealistic alternatives and the features that help distinguish them.
Retinal vein occlusion
Venous obstruction can cause retinal haemorrhage, oedema and ischaemia in a characteristic distribution. Hypertension or diabetes may be contributing risk factors, but the retinal event still needs its own diagnosis and management plan.
Other causes of disc swelling
Raised intracranial pressure, inflammation and optic nerve ischaemia can cause disc swelling. The finding should not be attributed to blood pressure without considering visual function, neurological symptoms and the rest of the examination.
An unrelated cause of visual loss
Cataract, corneal disease, retinal detachment and non-diabetic macular disorders may explain the current complaint. A familiar diagnosis of diabetes must not become a substitute for identifying the actual cause of new symptoms.
07ManagementImmediate care, first-line treatment, alternatives and escalation.
01Acute retinal and systemic riskAct on the dangerous combinationFirst stepSevere hypertension accompanies retinal injury or new visual symptoms suggest an acute event.+
- 1Arrange same-day specialist care for the NICE severe-pressure and retinal-sign combination, including assessment for injury outside the eye.
- 2For sudden visual loss or a new field shadow, use the appropriate emergency retinal or neurological pathway without waiting for screening.
- 3Document blood pressure, visual findings, symptom timing and relevant medicines so the receiving teams can coordinate care.
02Asymptomatic diabetes surveillanceKeep screening connected to clinical careA person with diabetes has no new visual symptom and needs ongoing surveillance.+
- 1Confirm enrolment in the relevant national screening programme and explain that its purpose is detecting diabetic retinal disease.
- 2In England, explain the invitation interval from previous results; two successive tests without retinopathy support a two-year interval.
- 3Continue ordinary eye care and ensure that referral or surveillance after an abnormal result is followed through to a defined appointment.
03Established retinal diseaseTreat ocular and systemic contributors togetherSpecialist assessment confirms diabetic macular or proliferative disease requiring treatment or closer review.+
- 1Agree a retinal plan based on lesion activity, visual impact and anatomy, rather than the HbA1c result alone.
- 2Coordinate glycaemic, blood-pressure and other vascular risk management with the responsible diabetes or primary-care team.
- 3Before a major treatment change, communicate the retinal status and organise the ophthalmic review needed to assess early worsening or progression.
08ComplicationsImportant consequences, why they occur and why they matter clinically.
Central visual impairment
Macular oedema or ischaemia can impair reading and recognition of detail. Improved systemic control does not immediately reverse every macular lesion, and local retinal treatment may still be needed to preserve useful function.
Bleeding and traction
Proliferative retinal disease can lead to vitreous haemorrhage and mechanical retinal separation. The visibility of the retina and relationship of traction to the macula influence specialist treatment decisions.
Systemic target-organ injury
Severe hypertension accompanied by retinal injury may coexist with renal, cardiac or cerebral damage. An ophthalmic finding can therefore signal the need for urgent systemic assessment rather than an eye-only follow-up plan.
09Monitoring and follow-upTreatment response, safety checks and longer-term review.
- Track retinal findings and visual function alongside systemic control, recognising that these measures may change at different rates.
- Confirm that people receiving active hospital retinal care have a documented review pathway and know which appointments replace or supplement screening.
- Review missed visits, transport, visual difficulty using medicines and communication needs so that a nominal follow-up plan is actually achievable.
- Provide a specific route for new symptoms, including urgent assessment for sudden loss, a curtain or a substantial floater change.
- After an acute hypertensive presentation, ensure both systemic follow-up and any required ophthalmic review are arranged; improvement in one domain does not establish resolution in the other.
10Special situationsVariants, exceptions and circumstances that change the usual approach.
Screening does not assess every eye problem
The diabetic programme is designed around retinopathy detection and referral. It does not replace a complete eye examination for a new complaint, refraction or other ocular disease. Explain this distinction when a person assumes that a recent screening photograph makes another assessment unnecessary.
Rapid improvement can require closer observation
A substantial fall in HbA1c can be associated with early worsening of pre-existing retinopathy. NICE advises communication with ophthalmology before treatment expected to cause this change. The response is coordinated retinal assessment, not a blanket instruction to leave harmful hyperglycaemia untreated.
Pregnancy changes retinal surveillance
Pre-existing diabetes needs pregnancy-specific retinal assessment. NICE distinguishes preconception planning, when rapid glucose optimisation is deferred until retinal assessment and treatment, from early pregnancy with high HbA1c, when retinopathy is not a contraindication to rapid optimisation. Coordinate diabetes, maternity and eye care rather than applying either rule indiscriminately.
An eye finding needs a receiving clinician
A report of severe blood pressure and retinal haemorrhage should reach a service able to assess systemic injury that day. Sending an ordinary optometry letter with no urgent handover can leave the patient between services while a dangerous systemic process continues.
Protection of function is practical
Ask whether vision affects glucose monitoring, insulin administration, recognising tablets or arranging food. Accessible devices, labels and support may be needed while treatment proceeds. Improving the person's ability to manage their diabetes can support both immediate safety and longer-term retinal care.
11Common pitfallsFrequent interpretation and management errors.
- 01
Attributing all retinal haemorrhages to diabetes without measuring blood pressure or considering another vascular disorder.
- 02
Waiting for papilloedema before acting on severe hypertension with retinal haemorrhage.
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Using a two-year low-risk screening interval for a patient with active hospital-treated retinopathy or new symptoms.
- 04
Promising that a lower HbA1c will immediately restore vision already affected by macular or tractional disease.
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Allowing rapid glycaemic treatment changes and retinal follow-up to proceed without communication between the responsible teams.