Stocker’s Line: Iron Line at the Pterygium Head

Stocker’s line is a fine, brown-yellow line of iron in the corneal epithelium that runs in front of the head of a pterygium.

It marks the advancing edge of the lesion on the cornea.

Therefore, a careful look at the line helps you judge how long the pterygium has been there and how active it is.

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What Stocker’s Line Represents

Iron accumulates in basal epithelial cells where the surface is uneven and the tear film pools.

The line follows the curve of the pterygium head and sits just beyond its apex.

Because the deposit lies in the epithelium, it does not cause symptoms of its own.

How to Find Stocker’s Line

Use the slit lamp with the cobalt blue filter, because the iron stands out as a dark line.

Look in the clear cornea just beyond the apex of the head.

The line may be partial or faint, so scan slowly.

Teachers often take the line as a sign of a slowly growing lesion, although the evidence is limited.

Stocker’s Line Versus Other Iron Lines

Location tells you the cause.

The Hudson-Stahli line is horizontal and sits in the lower cornea of older people.

The Fleischer ring surrounds the cone in keratoconus, and Ferry’s line sits in front of a filtering bleb.

Therefore, a line at the head of a pterygium is Stocker’s line (see corneal iron lines).

Managing the Pterygium

The line itself needs no treatment.

Manage the pterygium with lubricants and ultraviolet protection when it is small and quiet (see pterygium).

Consider excision with a conjunctival autograft if the lesion threatens the visual axis, causes astigmatism or stays inflamed (see conjunctival autograft).

History and Symptoms in Pterygium

Ask about foreign body sensation, redness, dryness and blur from induced astigmatism.

Also, ask about sun exposure, wind, dust and outdoor work.

Because the lesion grows slowly, many patients report years of symptoms.

Features of the Pterygium Head

Look at the head for small gray islands called Fuchs islets.

Also check the cornea for induced astigmatism with topography.

A thick, fleshy lesion with prominent vessels is more active than a flat, pale one.

Pseudopterygium

In contrast, a pseudopterygium is a scar band attached to the cornea after injury or inflammation.

Also, a probe can pass under its neck, which differs from a true pterygium.

Therefore, ask about previous burns, ulcers or surgery.

Surgical Considerations

Recurrence is the main problem after excision.

Conjunctival autograft gives lower recurrence rates than bare sclera excision.

Also, patients should avoid sun and wind exposure after surgery to lower the risk.

A Pitfall to Avoid

Ocular surface squamous neoplasia can mimic a pterygium.

Therefore, send excised tissue for histology when the lesion looks atypical (see ocular surface squamous neoplasia).

Also, watch for rapid growth, leukoplakia and prominent feeder vessels.

Reading the Line Together With the Lesion

A well-defined line suggests a stable head, and a blurred or absent line fits an active, advancing lesion.

This reading is a clinical impression, so confirm it by following the lesion over time.

Also, photograph the head to compare at later visits.

Staining Pattern

A pterygium head may take fluorescein at its margin because the surface is uneven.

Iron lines themselves do not stain, because they lie within the epithelium.

Therefore, use blue light without dye to see the line.

Symptoms That Need Attention

Pain, marked redness or a sudden change in the lesion call for review.

Also, reduced vision from astigmatism or from encroachment on the visual axis calls for referral.

Patient Counselling

Explain that the lesion is benign but can grow.

Ask the patient to wear sunglasses and a hat outdoors, and use lubricants for comfort.

Because recurrence follows surgery in some patients, discuss it before the operation.

Role of Topography

Pterygia flatten the cornea along the axis of the lesion and induce astigmatism.

The effect grows as the head moves toward the visual axis.

Therefore, measure topography before surgery and again after healing.

Stocker’s Line in Established Lesions

The line usually appears in long-standing lesions in adults who have spent years outdoors.

Young patients with a small pterygium rarely show it.

Because iron needs time to accumulate, the line points to a lesion that has been present for a while.

Photographing Stocker’s Line

Cobalt blue illumination gives the best photographs, and a smartphone adapter on the slit lamp captures them easily.

Also, take a second image with white light so you can compare the pterygium head with the line.

Stocker’s Line and Surgical Planning

The line lies just beyond the head, so it gives a rough landmark for the corneal extent of the lesion.

Also, record the distance from the limbus to the apex before surgery.

Because the apex moves toward the visual axis over time, this number guides the timing of excision.

For the latest studies, see the PubMed results for Stocker’s line.

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References

1. Gass JDM. The iron lines of the superficial cornea: Hudson-Stahli line, Stocker’s line, and Fleischer’s ring. Arch Ophthalmol. 1964;71:348-358.
2. Chui J, Di Girolamo N, Wakefield D, Coroneo MT. The pathogenesis of pterygium: current concepts and their therapeutic implications. Ocul Surf. 2008;6:24-43.
3. Hirst LW, Axelsen RA, Schwab I. Pterygium and associated ocular surface squamous neoplasia. Arch Ophthalmol. 2009;127:31-32.
4. Mannis MJ, Holland EJ, eds. Cornea. 5th ed. Elsevier; 2022.