Ophthalmology – Salzmann’s Nodular Degeneration

What the Corneal Lesion Represents

Salzmann’s nodular degeneration (SND) is an acquired, usually slowly progressive corneal degeneration characterized by one or more:

• Smooth, elevated subepithelial nodules
• Creamy white, gray-white, yellow-white, or occasionally bluish lesions

The nodules lie anteriorly, typically between the:

Corneal epithelium and Bowman layer

They are most often found in the:

• Peripheral cornea
• Midperipheral cornea

but may become:

• Paracentral
• Central

When central or sufficiently large, they can cause significant visual disturbance through:

Irregular astigmatism and alteration of corneal curvature.

Who Most Commonly Develops It

SND is uncommon, although its exact prevalence is uncertain.

It occurs most often in:

• Middle-aged or older adults
• Women more frequently than men

Disease may be:

• Unilateral
• Bilateral
• Solitary
• Multifocal

Why the Nodules Form

The precise mechanism is incompletely understood.

Current evidence favors:

Chronic epithelial injury and ocular-surface inflammation → abnormal wound healing → subepithelial fibrosis and collagen deposition

rather than a true inherited corneal dystrophy.

Conditions That Predispose to SND

Frequently associated ocular surface disorders include:

• Meibomian gland dysfunction
• Dry eye disease
• Blepharitis
• Chronic keratitis
• Vernal keratoconjunctivitis
• Previous phlyctenular keratitis
• Trachoma
• Interstitial keratitis
• Chronic contact lens wear
• Ocular trauma

SND may also appear after:

• Corneal surgery
• Longstanding ocular surface irritation

Many patients nevertheless have:

No clearly identifiable precipitating disorder.

Relationship With Other Corneal Disease

SND can coexist with:

• Epithelial basement membrane dystrophy
• Dry eye disease
• Meibomian gland dysfunction
• Prior corneal inflammation
• Previous keratorefractive or other corneal surgery

The underlying ocular surface disorder should be treated because ongoing inflammation may promote:

• Symptoms
• Progression
• Recurrence after surgery

Typical Symptoms

Many lesions are:

Asymptomatic

and discovered during routine examination.

Symptomatic patients may report:

• Foreign-body sensation
• Dryness
• Burning
• Tearing
• Redness
• Intermittent discomfort
• Photophobia
• Reduced vision

Pain is less common but may occur with:

• Epithelial breakdown
• Recurrent erosion

Why Vision Becomes Blurred

Vision may decline because the nodules distort the anterior corneal surface.

Consequences include:

• Irregular astigmatism
• Higher-order aberrations
• Reduced contrast
• Variable refraction
• Corneal flattening
• Hyperopic shift

A peripheral lesion can therefore influence central vision even when it does not directly cover the visual axis.

Characteristic Slit-Lamp Appearance

Typical examination shows:

• Smooth elevated corneal nodule
• Gray-white to creamy appearance
• Subepithelial location
• Often multiple lesions

The epithelium over the nodule may be:

• Intact
• Thinned
• Irregular

Usual Corneal Distribution

SND most often affects the:

Midperipheral or peripheral cornea

but lesions may extend centrally.

Central and paracentral nodules are more likely to produce:

• Reduced acuity
• Irregular astigmatism
• Refractive instability

Changes in Bowman Layer

Bowman layer underneath a nodule may be:

• Thinned
• Fragmented
• Disrupted
• Absent

The lesion therefore represents more than simple epithelial elevation.

Microscopic Appearance

Histopathology classically shows:

• Subepithelial hyaline/fibrous collagen
• Disorganized extracellular matrix
• Attenuated epithelium
• Disruption or absence of Bowman layer

Fibroblast-like cells may be present within the lesion.

How the Diagnosis Is Established

Diagnosis is usually:

Clinical

based on slit-lamp appearance.

Additional testing is most useful when:

• Visual acuity is reduced
• Cataract surgery is being planned
• Refractive surgery is being considered
• Corneal irregularity needs quantification

Mapping the Corneal Shape

Corneal topography or tomography is particularly useful when visual symptoms are present.

It may demonstrate:

• Irregular astigmatism
• Localized flattening
• Distortion extending beyond the visible nodule

These changes can explain reduced vision even when the lesion is peripheral.

Anterior Segment OCT

Anterior segment OCT can demonstrate:

• Hyperreflective subepithelial lesion
• Thickness of the nodule
• Relationship to Bowman layer
• Depth of associated stromal haze

It can be useful when planning:

• Superficial keratectomy
• PTK

Conditions That Can Look Similar

Important alternatives include:

• Spheroidal/climatic droplet degeneration
• Corneal keloid
• Corneal amyloidosis
• Band keratopathy
• Subepithelial corneal scar
• Peripheral hypertrophic scarring
• Nodular degeneration after chronic inflammation

The smooth elevated subepithelial configuration and clinical context usually distinguish SND.

When Observation Is Enough

If the patient is:

• Asymptomatic
• Visually unaffected
• Stable

then:

No direct treatment of the nodules is required.

The underlying ocular surface should still be optimized.

Improving the Ocular Surface

Management may include:

• Preservative-free artificial tears
• Lubricating gels or ointments
• Warm compresses
• Lid hygiene
• Meibomian gland treatment
• Treatment of blepharitis
• Modification of contact lens wear

This may significantly improve:

• Foreign-body sensation
• Fluctuating vision

but usually does not make established nodules disappear.

Anti-Inflammatory Surface Therapy

If clinically significant ocular-surface inflammation is present, treatment may include:

• Short course of topical corticosteroid under supervision
• Topical cyclosporine
• Lifitegrast where appropriate

These agents treat the associated inflammatory dry-eye disease rather than directly dissolving the nodule.

Punctal Occlusion

Punctal plugs may help selected patients with:

• Significant aqueous-deficient dry eye

but active lid or surface inflammation should generally be controlled first.

Using Contact Lenses for Optical Rehabilitation

A:

• Rigid gas-permeable lens
• Scleral lens
• Occasionally hybrid lens

can sometimes improve vision by masking:

Irregular corneal astigmatism

when surgery is undesirable or unsuitable.

When Surgery Becomes Appropriate

Surgical treatment is considered when nodules cause:

• Reduced vision
• Significant irregular astigmatism
• Persistent discomfort
• Recurrent epithelial breakdown
• Contact lens intolerance
• Difficulty obtaining reliable keratometry before cataract surgery

Superficial Keratectomy

Superficial keratectomy is usually the principal surgical treatment.

The procedure typically involves:

• Removing epithelium over the lesion
• Peeling or dissecting the nodule from the anterior cornea
• Smoothing the underlying surface

Many nodules separate relatively cleanly from the underlying stroma.

Expected Effects of Nodule Removal

Successful superficial keratectomy can improve:

• Best-corrected visual acuity
• Irregular astigmatism
• Corneal regularity
• Foreign-body sensation

It may also reverse some of the:

Nodule-induced corneal flattening and hyperopic shift.

Phototherapeutic Keratectomy

Excimer laser phototherapeutic keratectomy (PTK) may be useful when:

• Residual anterior stromal haze remains
• Surface irregularity persists after mechanical removal
• Disease is broad or recurrent

PTK can smooth the anterior cornea but may cause:

• Refractive shift
• Haze
• Recurrence

Therefore treatment depth should be conservative.

Mitomycin C

Mitomycin C has sometimes been applied during surgery to reduce:

• Fibroblast proliferation
• Haze
• Recurrence

However:

Its routine use for every Salzmann lesion is not established.

It should be used selectively because of potential corneal toxicity.

When Corneal Transplantation Is Needed

Keratoplasty is:

Rarely required

because disease is usually superficial.

For unusually extensive, deep, or recurrent disease, options may include:

• Anterior lamellar keratoplasty
• Rarely penetrating keratoplasty

Importance Before Cataract Surgery

SND can significantly distort:

• Keratometry
• Corneal topography
• Astigmatism measurements
• IOL power calculations

Therefore visually or topographically significant nodules should usually be addressed:

Before cataract biometry and definitive IOL selection.

Why Cataract Measurements Can Be Misleading

A Salzmann nodule may cause:

• Local flattening
• Central corneal flattening
• Irregular astigmatism
• Hyperopic refractive shift

Removing the lesion can substantially change:

Corneal power measurements.

Using preoperative measurements obtained before treating significant SND can therefore produce an:

IOL calculation error.

Timing Cataract Biometry After Keratectomy

After superficial keratectomy, corneal measurements should be repeated only after:

The epithelium and corneal curvature have stabilized.

This often requires:

• Several weeks
• Sometimes longer for larger or multiple lesions

Serial reproducible topography/keratometry is more important than using a rigid fixed waiting period.

Considerations Before Refractive Surgery

Unrecognized SND can also interfere with:

• LASIK planning
• PRK planning
• Toric correction

The ocular surface and corneal shape should first be stabilized.

Healing After Surgical Removal

After superficial keratectomy, management may include:

• Bandage contact lens
• Topical antibiotic until epithelial closure
• Short topical corticosteroid course
• Preservative-free lubrication

Follow-up is initially close to confirm:

Complete epithelial healing.

Risk of Recurrence

SND can recur after:

• Superficial keratectomy
• PTK
• Other treatment

Recurrence may occur:

Years later

and is more likely if the underlying ocular surface disease remains active.

Preventing Recurrence

Useful strategies include:

• Treating MGD
• Controlling dry eye disease
• Managing chronic blepharitis
• Avoiding unnecessary ocular surface trauma
• Optimizing contact lens use

These measures cannot guarantee prevention but may improve long-term surface stability.

Possible Complications

Potential problems include:

• Irregular astigmatism
• Reduced visual acuity
• Recurrent epithelial erosion
• Persistent epithelial defect
• Infectious keratitis if epithelium breaks down
• Corneal haze
• Recurrence after surgery

Expected Long-Term Outcome

Overall prognosis is:

Excellent

because the condition is:

• Benign
• Usually slowly progressive
• Often stable for many years
• Highly amenable to superficial treatment when symptomatic

Most patients maintain good functional vision.

Ophthalmology Pearls

• Salzmann’s nodular degeneration is an acquired subepithelial corneal degeneration characterized by smooth gray-white, creamy, yellowish, or bluish elevated nodules.
• It occurs most commonly in middle-aged or older women.
• SND is probably related to chronic ocular surface injury, inflammation, and abnormal wound healing, rather than representing a true inherited dystrophy.
• Important associations include MGD, dry eye, blepharitis, previous keratitis, chronic contact lens wear, trauma, and previous corneal surgery.
• Many lesions are asymptomatic and require observation only.
• Visual loss usually results from irregular astigmatism and altered corneal curvature, not merely physical obstruction of the visual axis.
• Significant peripheral nodules can cause central corneal flattening and a hyperopic shift.
• Topography/tomography is valuable when vision is reduced or cataract/refractive surgery is planned.
• Anterior segment OCT can help define the subepithelial lesion and its relationship to Bowman layer.
• Conservative treatment focuses on lubrication and management of underlying ocular surface disease.
• Rigid or scleral lenses can sometimes improve vision by neutralizing irregular astigmatism.
• Superficial keratectomy is the main surgical treatment for symptomatic or visually significant nodules.
• PTK is useful when residual anterior stromal irregularity or haze remains.
• Mitomycin C may be used selectively, but routine use is not mandatory.
• Recurrence can occur even after successful removal, especially if the underlying ocular surface disorder persists.
• A visually significant Salzmann nodule should generally be removed before cataract biometry, because it can substantially distort keratometry and IOL power calculations.
• After keratectomy, wait for stable reproducible corneal measurements before final cataract or refractive surgery planning.