Choroidal Neovascularization (CNV): Causes, Symptoms, Types, Diagnosis, OCT Findings, and Treatment

Title: Choroidal Neovascularization (CNV): Causes, Symptoms & Treatment

Description: Learn about choroidal neovascularization (CNV), including its causes, types, symptoms, OCT and angiography findings, diagnosis, anti-VEGF treatment, complications, and prognosis.

Focus Keyword: Choroidal Neovascularization

Secondary Keywords: CNV, choroidal neovascularization causes, CNV symptoms, CNV OCT, choroidal neovascularization treatment, macular neovascularization, anti-VEGF, wet AMD

Introduction

Choroidal Neovascularization (CNV) is the abnormal growth of new blood vessels from the choroid toward or into the retinal pigment epithelium (RPE), subretinal space, or retina.

These newly formed vessels are often fragile and leaky. They can cause accumulation of:

• Fluid
• Blood
• Lipid
• Exudation

around the macula and can lead to distortion or loss of central vision.

CNV is particularly important in ophthalmology because it is a major cause of severe visual impairment in conditions such as neovascular age-related macular degeneration (AMD).

However, CNV can occur in several other disorders, including:

• Pathologic myopia
• Ocular histoplasmosis
• Angioid streaks
• Inflammatory chorioretinal diseases
• Pachychoroid-related disorders
• Choroidal tumors
• Trauma and other conditions

What Is Choroidal Neovascularization?

Choroidal neovascularization means the formation of abnormal new blood vessels originating from the choroidal circulation.

The term can be broken down as:

Choroidal → originating from the choroid

Neo → new

Vascularization → formation of blood vessels

So:

Choroidal Neovascularization = Abnormal new choroidal blood vessels

These vessels can grow through or around Bruch's membrane and extend toward the RPE or retina.

Why Is CNV Important?

Normal blood vessels are tightly regulated.

CNV involves abnormal vascular growth that can result in:

New vessel formation

↓

Vascular leakage

↓

Subretinal/intraretinal fluid

↓

Hemorrhage

↓

Photoreceptor and RPE damage

↓

Macular dysfunction

↓

Central vision loss

Early diagnosis is important because ongoing leakage and bleeding can cause irreversible macular damage.

Anatomy Relevant to Choroidal Neovascularization

To understand CNV, it is helpful to understand the relationship between:

• Choroid
• Bruch's membrane
• RPE
• Photoreceptors
• Retina

The normal arrangement is:

Retina

↓

RPE

↓

Bruch's membrane

↓

Choriocapillaris

↓

Choroid

CNV develops when abnormal vessels cross the normal anatomical barriers.

How Does Choroidal Neovascularization Develop?

One of the most important drivers of CNV is vascular endothelial growth factor (VEGF).

When retinal or RPE tissues experience:

• Hypoxia
• Oxidative stress
• Inflammation
• Degenerative changes
• Mechanical stress

VEGF signaling can increase.

VEGF promotes:

• Endothelial cell proliferation
• New vessel formation
• Vascular permeability

Therefore:

Disease process

↓

Increased VEGF signaling

↓

Abnormal vessel growth

↓

Fragile new vessels

↓

Leakage and hemorrhage

↓

Macular damage

Types of Choroidal Neovascularization

CNV can be classified according to the anatomical location of the abnormal vessels.

Type 1 CNV – Sub-RPE Neovascularization

Type 1 CNV develops beneath the RPE.

The abnormal vessels grow between:

RPE ↔ Bruch's membrane

This is commonly associated with neovascular AMD.

OCT appearance may include:

• Sub-RPE fluid
• Pigment epithelial detachment
• Double-layer sign
• Sub-RPE hyperreflective material

Type 2 CNV – Subretinal Neovascularization

Type 2 CNV grows through the RPE and extends into the subretinal space.

It may be associated with:

• Intraretinal fluid
• Subretinal fluid
• Hemorrhage
• Exudation

Type 3 CNV – Retinal Angiomatous Proliferation

Type 3 CNV is commonly referred to as retinal angiomatous proliferation (RAP).

It involves abnormal vascular proliferation originating within the retina, with connections involving the deeper vascular/choroidal circulation.

Important Exam Point

Type 3 CNV = Retinal Angiomatous Proliferation (RAP)

Macular Neovascularization Classification

Modern imaging terminology increasingly uses the broader term macular neovascularization (MNV).

MNV can include:

• Type 1
• Type 2
• Type 3
• Mixed lesions

This terminology emphasizes the anatomical location and vascular origin of the neovascular complex.

Causes of Choroidal Neovascularization

CNV is not a disease by itself. It is a complication or manifestation of several underlying disorders.

1. Neovascular Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is one of the most important causes of CNV.

In neovascular AMD, abnormal vessels develop beneath or through the RPE and can cause:

• Fluid
• Hemorrhage
• Exudation
• Fibrosis
• Macular damage

2. Pathologic Myopia

Severe myopia can cause structural changes in the posterior eye.

These may include:

• Thinning of the choroid
• Stretching of the retina
• Lacquer cracks
• Bruch's membrane abnormalities

These changes can predispose to myopic CNV.

3. Ocular Histoplasmosis Syndrome

Presumed ocular histoplasmosis can cause:

• Chorioretinal scars
• Peripapillary changes
• Macular CNV

The neovascularization can develop near areas of previous chorioretinal damage.

4. Angioid Streaks

Angioid streaks represent breaks or abnormalities involving Bruch's membrane.

These defects can permit abnormal vessel growth and lead to CNV.

5. Inflammatory Chorioretinal Diseases

Inflammation can stimulate abnormal vascular growth.

CNV may occur with conditions such as:

• Multifocal choroiditis
• Punctate inner choroidopathy
• Presumed ocular histoplasmosis
• Other inflammatory chorioretinal disorders

6. Pachychoroid-Related Disorders

CNV can occur in some patients with pachychoroid-spectrum disease.

For example, patients with chronic central serous chorioretinopathy can develop secondary neovascularization.

7. Choroidal Trauma and Scarring

Previous ocular trauma or chorioretinal scars can occasionally create conditions favorable for abnormal vascular proliferation.

8. Choroidal Tumors and Other Rare Causes

Some choroidal lesions and tumors can be associated with secondary vascular abnormalities.

The underlying cause must therefore be identified whenever CNV is diagnosed.

Risk Factors for Choroidal Neovascularization

Risk factors depend on the underlying disease.

Important factors may include:

• Increasing age
• AMD
• Smoking
• Genetic susceptibility
• Pathologic myopia
• Previous ocular inflammation
• Angioid streaks
• Chorioretinal scars
• Chronic pachychoroid disease

Symptoms of Choroidal Neovascularization

CNV primarily affects central vision when the macula is involved.

1. Blurred Central Vision

Patients may notice that objects appear unclear.

This can interfere with:

• Reading
• Driving
• Face recognition
• Fine-detail tasks

2. Metamorphopsia

Straight lines may appear:

• Bent
• Wavy
• Distorted

This is a common warning symptom of macular disease.

3. Central Scotoma

Patients may notice:

• A dark spot
• Gray spot
• Missing area
• Blurred area

in central vision.

4. Sudden Visual Loss

Acute bleeding from fragile neovascular vessels can cause sudden deterioration in vision.

5. Micropsia or Macropsia

Objects may sometimes appear:

• Smaller than normal
• Larger than normal

depending on the retinal changes.

6. Reduced Contrast Sensitivity

Patients may have difficulty distinguishing subtle details.

7. Color Vision Changes

Macular involvement may produce changes in color perception.

Important Warning Sign

New distortion of straight lines or sudden central visual loss should be evaluated promptly.

Diagnosis of Choroidal Neovascularization

Diagnosis generally involves multimodal imaging.

Important investigations include:

1. Visual acuity
2. Dilated fundus examination
3. OCT
4. OCT angiography
5. Fluorescein angiography
6. Indocyanine green angiography in selected cases

1. Dilated Fundus Examination

The clinician may identify:

• Retinal hemorrhage
• Subretinal hemorrhage
• Exudates
• Pigmentary abnormalities
• Fibrosis
• Drusen or other underlying pathology

2. Optical Coherence Tomography

OCT is one of the most important tests for detecting and monitoring CNV-related activity.

Possible OCT findings include:

• Intraretinal fluid
• Subretinal fluid
• Pigment epithelial detachment
• Sub-RPE hyperreflective material
• Hyperreflective foci
• RPE disruption
• Fibrotic tissue
• Outer retinal damage

High-Yield Point

New or increasing intraretinal/subretinal fluid on OCT can indicate active neovascular disease.

3. OCT Angiography

OCTA allows visualization of vascular networks without intravenous dye.

It can demonstrate:

• Neovascular networks
• Flow patterns
• Vascular branching
• Anastomotic vessels
• Changes over time

OCTA is particularly useful for detecting nonexudative or quiescent neovascularization, although interpretation requires clinical correlation.

4. Fluorescein Angiography

Fluorescein angiography has traditionally played an important role in identifying leakage from CNV.

It can demonstrate:

• Early hyperfluorescence
• Progressive leakage
• Classic or occult patterns in historical classifications

5. Indocyanine Green Angiography

ICGA provides better visualization of the choroidal circulation than fluorescein angiography.

It can be particularly useful in:

• Pachychoroid disease
• Type 1 CNV
• Polypoidal lesions
• Occult choroidal vascular abnormalities

Active vs Inactive CNV

A major clinical question is whether CNV is active or inactive.

Active CNV may show:

• New or increasing fluid
• Hemorrhage
• Exudation
• New visual symptoms
• Enlargement or change of the neovascular complex

Inactive CNV may show:

• No active leakage
• No new fluid
• Stable structural findings
• Fibrotic or atrophic changes

Choroidal Neovascularization and VEGF

VEGF is central to the development of many forms of CNV.

VEGF can:

• Stimulate angiogenesis
• Increase vascular permeability
• Promote leakage

This explains why anti-VEGF therapy has become the primary treatment for many exudative CNV conditions.

Treatment of Choroidal Neovascularization

Treatment depends on:

• Underlying cause
• CNV type
• Activity
• Location
• Visual acuity
• OCT findings
• Presence of hemorrhage or fluid

The main treatment for many active CNV conditions is intravitreal anti-VEGF therapy.

1. Anti-VEGF Injections

Anti-VEGF medications inhibit VEGF signaling and can reduce:

• Abnormal vessel growth
• Vascular leakage
• Retinal fluid
• Macular edema

Common anti-VEGF agents used in ophthalmology include:

• Bevacizumab
• Ranibizumab
• Aflibercept
• Faricimab
• Brolucizumab in selected settings

The choice depends on the underlying disease, local practice, patient factors, and clinician assessment.

2. Treatment Regimens

Anti-VEGF treatment may follow different strategies.

Loading Phase

Several injections may initially be given at regular intervals.

Treat-and-Extend

Treatment intervals are gradually extended when disease activity remains controlled.

Pro Re Nata

Treatment may be given when disease activity recurs.

The specific regimen depends on the drug and disease.

3. Photodynamic Therapy

Photodynamic therapy (PDT) has an important role in selected forms of CNV and pachychoroid-related neovascular disease.

It may be particularly useful in specific conditions where choroidal vascular abnormalities are a major component.

4. Laser Photocoagulation

Traditional thermal laser has a limited role today because many macular CNV conditions are treated more effectively with anti-VEGF therapy.

Laser may still be considered in selected non-foveal lesions or specific circumstances.

5. Treatment of the Underlying Disease

Successful management requires treating the condition responsible for CNV.

For example:

AMD

→ Anti-VEGF-based management

Myopic CNV

→ Often anti-VEGF

Inflammatory CNV

→ Anti-VEGF plus treatment of inflammation when appropriate

Pachychoroid-related CNV

→ Anti-VEGF with consideration of PDT in selected cases

What Happens If CNV Is Left Untreated?

Persistent active CNV can cause:

• Chronic fluid accumulation
• Retinal damage
• Hemorrhage
• RPE injury
• Photoreceptor loss
• Fibrosis
• Macular scarring
• Permanent central vision loss

Complications of Choroidal Neovascularization

1. Subretinal Fluid

Fluid may accumulate beneath the retina.

2. Intraretinal Fluid

Fluid may enter retinal tissue.

3. Retinal Hemorrhage

Fragile abnormal vessels may bleed.

4. Pigment Epithelial Detachment

The RPE can become elevated due to fluid or neovascular tissue.

5. Fibrosis

Chronic disease may lead to scar formation.

6. Photoreceptor Loss

Persistent disease can damage photoreceptors.

7. Macular Atrophy

Long-term disease and treatment may be associated with retinal/RPE atrophic changes.

8. Permanent Central Vision Loss

Advanced untreated disease can result in significant visual impairment.

Choroidal Neovascularization in Age-Related Macular Degeneration

CNV is a defining feature of neovascular AMD.

The disease may progress from:

Drusen / RPE changes

↓

Bruch's membrane/RPE dysfunction

↓

VEGF and other angiogenic signaling

↓

CNV

↓

Fluid or hemorrhage

↓

Macular damage

↓

Central vision loss

Choroidal Neovascularization in Myopia

Myopic CNV is an important complication of pathologic myopia.

It may present with:

• Sudden visual deterioration
• Central scotoma
• Metamorphopsia
• Small macular hemorrhage

OCT and OCTA are useful for diagnosis and follow-up.

Anti-VEGF therapy is commonly used for active myopic CNV.

CNV vs Central Serous Chorioretinopathy

These conditions can sometimes be confused because both may show subretinal fluid.

CSC

Usually involves:

• Choroidal hyperpermeability
• RPE dysfunction
• Subretinal fluid

CNV

Involves:

• Abnormal neovascular tissue
• Vascular leakage
• Potential hemorrhage

Importantly, chronic CSC can develop secondary CNV.

CNV vs Retinal Neovascularization

These terms are related but describe different vascular origins.

Choroidal Neovascularization

Abnormal vessels arise from the choroidal circulation.

Retinal Neovascularization

Abnormal vessels arise from the retinal circulation.

Retinal neovascularization is commonly associated with ischemic retinal diseases such as:

• Proliferative diabetic retinopathy
• Retinal vein occlusion
• Retinopathy of prematurity

CNV vs Polypoidal Choroidal Vasculopathy

Polypoidal choroidal vasculopathy is an important condition within the spectrum of aneurysmal type 1 neovascularization.

It may present with:

• Subretinal hemorrhage
• Pigment epithelial detachment
• Exudation
• Recurrent fluid

ICGA can be particularly useful in identifying polypoidal lesions.

Prognosis of Choroidal Neovascularization

The prognosis depends on:

• Underlying disease
• Time of diagnosis
• Location of CNV
• Amount of retinal damage
• Presence of fibrosis
• Response to treatment
• Treatment adherence

With modern anti-VEGF therapy, many patients can maintain useful vision that might previously have been lost.

However, treatment generally controls the disease rather than permanently eliminating the underlying susceptibility.

Long-term monitoring may therefore be necessary.

Importance of Regular Follow-Up

CNV can reactivate even after successful treatment.

Follow-up may include:

• Visual acuity assessment
• OCT
• Fundus examination
• OCTA when indicated

Patients should also report new visual symptoms between scheduled appointments.

Amsler Grid and Home Monitoring

For selected patients with macular disease, an Amsler grid can help detect new distortion.

Patients can monitor for:

• New wavy lines
• Missing areas
• New central distortion
• Changes between the two eyes

However, home monitoring does not replace professional retinal examination or OCT.

When Should You See an Eye Specialist?

Seek prompt ophthalmic evaluation if you develop:

• Sudden central vision loss
• New distortion of straight lines
• A new dark spot in central vision
• New blurred vision
• Sudden increase in floaters associated with visual changes
• New visual symptoms in a known AMD patient

Early detection can allow treatment before irreversible macular damage becomes extensive.

Can Choroidal Neovascularization Be Prevented?

Prevention depends largely on controlling the underlying disease.

Helpful measures include:

Stop Smoking

Smoking is an important modifiable risk factor for AMD.

Manage Systemic Health

Maintain appropriate management of:

• Blood pressure
• Diabetes
• Cardiovascular risk factors

Regular Eye Examinations

Particularly important for people with:

• AMD
• High/pathologic myopia
• Previous CNV
• Chorioretinal inflammatory disease

Monitor Vision

Report new metamorphopsia or central visual changes promptly.

Frequently Asked Questions About CNV

What is choroidal neovascularization?

CNV is the abnormal growth of new blood vessels originating from the choroidal circulation and extending toward or into the RPE, subretinal space, or retina.

What is the most common cause of CNV?

In older adults, neovascular age-related macular degeneration is a major cause. CNV can also occur in pathologic myopia, inflammatory disorders, angioid streaks, and other conditions.

What are the symptoms of CNV?

Common symptoms include:

• Blurred central vision
• Metamorphopsia
• Central scotoma
• Sudden visual deterioration
• Reduced contrast

What does CNV look like on OCT?

OCT may show:

• Intraretinal fluid
• Subretinal fluid
• Pigment epithelial detachment
• Sub-RPE neovascular tissue
• RPE and outer retinal abnormalities

CNV = NEW VESSELS → LEAK → BLEED → LOSE CENTRAL VISION

NEW VESSELS

↓

LEAKAGE

↓

FLUID

↓

HEMORRHAGE

↓

MACULAR DAMAGE

↓

VISION LOSS

Types mnemonic:

1 = Under RPE

2 = Under Retina

3 = Retina-origin/RAP

One-Minute Revision

Choroidal Neovascularization

Underlying disease

↓

VEGF signaling

↓

Abnormal choroidal vessel growth

↓

Leakage / hemorrhage

↓

Fluid + retinal damage

↓

Central visual loss

Diagnosis

OCT + OCTA ± FA/ICGA

Major causes

Neovascular AMD

Pathologic myopia

Inflammatory chorioretinal disease

Angioid streaks

Pachychoroid-related disease

Treatment

Anti-VEGF is the cornerstone for many active CNV conditions.

Important classification

Type 1 → Sub-RPE

Type 2 → Subretinal

Type 3 → RAP

Conclusion

Choroidal Neovascularization (CNV) is an important sight-threatening complication of several retinal and choroidal disorders. It occurs when abnormal new blood vessels develop from the choroidal circulation and extend toward the RPE, subretinal space, or retina.

The abnormal vessels are fragile and may leak fluid or bleed, resulting in intraretinal fluid, subretinal fluid, pigment epithelial detachment, hemorrhage, fibrosis, and macular damage. The most important cause in older adults is neovascular AMD, while pathologic myopia, inflammatory eye disease, angioid streaks, and pachychoroid-related disorders are other important causes.

Modern imaging—particularly OCT and OCT angiography—has transformed the diagnosis and monitoring of CNV. Anti-VEGF therapy is the cornerstone of treatment for many forms of active CNV, helping reduce leakage, control neovascular activity, and preserve vision.

The key clinical concept is:

CNV → abnormal choroidal vessels → VEGF-mediated leakage/bleeding → macular damage → central vision loss

Early recognition of metamorphopsia, new central blur, or a central scotoma, followed by prompt retinal evaluation, is essential for achieving the best possible visual outcome.