Poorly controlled hypertension (HTN) affects several systems such as the cardiovascular, renal, cerebrovascular, and retina. The damage to these systems is known as target-organ damage (TOD). HTN affects the eye causing 3 types of ocular damage: choroidopathy, retinopathy, and optic neuropathy. Hypertensive retinopathy (HR) occurs when the retinal vessels get damaged due to elevated blood pressure. There has been significant evidence that hypertensive retinopathy acts as a predictor of systemic morbidity and mortality due to TOD. A study by Erden et al. showed that the increase in the incidence of retinopathy is related to the degree of severity and duration of HTN.
Apart from essential and secondary hypertension, there are other factors which play an important role in the development of hypertensive retinopathy. The prevalence of hypertensive retinopathy is more in Afro-Caribbean as compared to Europeans and more in women as compared to men. Genetic factors can also play a role with certain genotypes associated with an increased risk of hypertensive retinopathy. Pontremoli et al. studied the genetic factors linked to hypertensive retinopathy and found the deletion of the allele of the angiotensin-converting enzyme has a higher risk associated with the development of hypertensive retinopathy. Smoking is considered to have a strong association with severe or malignant hypertensive retinopathy as studied by Poulter et al. Renal dysfunction (persistent microalbuminuria and low creatinine clearance) in patients has shown to be a marker for hypertensive retinopathy and end-organ damage. Uckaya et al. found an association with plasma leptin. It was observed that plasma leptin levels were higher in patients with hypertensive retinopathy and postulated that it is associated with vascular endothelium damage.
The severity and duration of hypertension are directly proportional to the incidence of hypertensive retinopathy as studied by Erden et al. The incidence of hypertensive retinopathy in their study was 66.3%. Kabedi et al. stated hypertensive retinopathy incidence of 83.6% out of the total hypertensive patients and found chronic kidney disease to be the most significant factor to predict severe hypertensive retinopathy. As per the study conducted by Del Brutto et al., hypertensive retinopathy grade 1 was recorded in 37%, and grade 2 hypertensive retinopathy was noted in 17% of hypertensive patients.
Retinal blood vessels have distinct features, which differentiate them from other blood vessels:
Thus, an increase in blood pressure (BP) is transferred directly to the vessels which initially constrict. However, a further increase in BP overcomes this compensatory tone and damage to the muscle layer and endothelium ensues.
Hypertensive retinopathy has the following phases:
In this phase, the local autoregulatory mechanisms come into play. This causes vasospasm and retinal arteriole narrowing, which is evident by the decrease in the arteriole to venule ratio (Normal = 2:3). In older patients with arteriosclerosis, focal arteriolar narrowing develops, as affected vascular segments cannot undergo narrowing.
Persistent increase in BP causes certain changes in vessel wall:
This leads to a severe form of arteriolar narrowing, arteriovenous (AV) crossing changes, and widening and accentuation of light reflex (silver and copper wiring). AV crossing changes occur when a thickened arteriole crosses over a venule and subsequently compresses it as the vessels share a common adventitious sheath. The vein, in turn, appears dilated and torturous distal to the AV crossing.
Seen in patients with severely increased BP; characterized by the disruption of the blood-brain barrier and leakage of blood and plasma into the vessel wall disrupting the autoregulatory mechanisms. In this stage, retinal signs occur such as retinal hemorrhage (flame-shaped and dot blot), hard exudate formation, necrosis of smooth muscle cells and retinal ischemia (cotton-wool spots).
Severe intracranial hypertension leads to optic nerve ischemia and edema (papilledema). Also, fibrinoid necrosis of choroidal arterioles occurs leading to segmental infarction of choriocapillaries. This gives rise to:
These signs are termed as choroidopathy.
Hypertensive retinopathy is usually asymptomatic and is diagnosed on fundoscopic features. The following are signs of hypertensive retinopathy.
AV Crossing Changes
Macular star formation due to deposition of hard exudates around the macula.
Optic Nerve Changes
Optic disk swelling (also known as hypertensive optic neuropathy)
In a study by Wong et al., they identified certain retinal signs to be associated with increased risk for stroke. The signs are AV nicking, focal arteriolar narrowing (as this is associated with arteriosclerosis), microaneurysms, cotton wool spots, retinal hemorrhages (dot blot and flame-shaped), and decreased AV ratio.
The following are classification systems for hypertensive retinopathy based on fundus examination with indirect ophthalmoscopy or +90 D lens.
Keith-Wagner- Barker classification
For Hypertensive Retinopathy
The main purpose of screening for hypertensive retinopathy is that retinal vessels are the only blood vessels visible on routine examination. The effects of chronically elevated HTN are easily visible in the eye as hypertensive retinopathy and choroidopathy, and this reflects the vascular changes occurring in other systems. Ophthalmologists and general physicians should work in collaborations to ensure that hypertensive patients are efficiently screened, and timely managed to reduce the risk of ocular and systemic morbidity and mortality. Henderson et al., however, noted that Hypertensive retinopathy is associated with an increased risk of stroke even after controlling BP and other vascular risk factors.
The management of hypertensive retinopathy depends on the severity of the disease:
Important to note is that BP should be lowered in a controlled fashion. This is crucial to prevent ischemic damage to vital organs such as optic nerve and brain.
The other conditions which present with optic disc swelling are:
Conditions which mimic chronic hypertensive retinopathy are:
Chronic hypertensive retinopathy rarely causes significant visual loss. The retinal changes can be halted when hypertension is treated. However, arteriolar narrowing and AV changes persist. For untreated malignant hypertension, the mortality is high as 50% within 2 months of diagnosis and almost 90% by the end of 1 year. Vision loss in hypertensive retinopathy is because of either secondary optic atrophy after prolonged papilloedema or retinal pigmentary changes after exudative retinal detachment.
Hypertension has effects on multiple systems, and it is important to have care coordination between the physician, physician assistant, nurse practitioner, ophthalmologist, nephrologist, and cardiologist to ensure early detection and control of hypertension and improve patient outcomes. Patients with hypertension need to be informed that they should follow up regularly with an ophthalmologist for a complete eye assessment. In addition, patients need to be educated about the importance of compliance with antihypertensive medications. (Level V)
In most patients, hypertensive retinopathy does not cause vision loss as long as the hypertension is treated. However, if the blood pressure remains untreated, it can lead to vision loss within a short period of time. The cause of the vision loss is either due to retinal pigmentary changes or secondary to optic atrophy, neither of which is reversible. (Level V)
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