Corneal surface · Indication

Epithelial basement
membrane dystrophy
(Cogan’s dystrophy)

A surface that no longer quite holds — and the discomfort that goes with it.

Cogan’s dystrophy, or epithelial basement membrane dystrophy, is the most common abnormality of the corneal surface. The basement membrane is the thin layer to which the epithelium, the surface covering, anchors. When it is irregular, the epithelium adheres poorly and can lift in places. On examination, this produces the characteristic patterns of "maps", "dots" and "fingerprints" — hence its other name, map-dot-fingerprint dystrophy.

What you may feel

Many people with this dystrophy have no symptoms: it is found on examination. When it does show itself, it is often in two ways.

Painful episodes

A sharp pain on waking, as you open your eyes, when the eyelid pulls on a poorly attached epithelium. The eye waters, becomes sensitive to light and red, with a gritty, foreign-body sensation. The episode can last from a few minutes to a few days, then settle, before returning.

Fluctuating vision

When the surface irregularity lies in the visual axis, vision can become blurred at times, with halos or a hazy veil that varies from one day to the next.

Why it happens

The epithelium normally holds to the cornea through an anchoring system on its basement membrane. In this dystrophy, that anchoring is faulty: overnight, dryness and the rubbing of the eyelid on waking are enough to lift the superficial layer.

What is tried first

Most situations are managed without any procedure. Depending on the discomfort, I suggest simple, step-by-step measures: intensive lubrication, ointment at night, sometimes hypertonic (high-salt) drops to limit swelling of the epithelium, or a protective contact lens for a set period to allow firm adhesion to rebuild. As long as these measures are enough, there is no reason to go further.

Where PTK comes in, and what it can offer

PTK is considered when the painful episodes recur despite these measures, or when the surface irregularity lastingly affects vision. The laser removes the abnormal basement membrane and the poorly anchored superficial layer; the epithelium can then reform on a more regular surface, to which it adheres better.

The aim is twofold: to space out, or even stop, the painful recurrences, and to regularise the surface so as to stabilise vision when that was what was affected. Studies report a lasting improvement in a large proportion of cases — though this cannot be guaranteed for every eye.

Stated plainly

What you should know about its limits

PTK treats the surface, not the underlying tendency: the dystrophy remains, and a recurrence is still possible over time. The procedure can then be repeated. Like any PTK, it can shift the correction slightly towards hyperopia, which can be anticipated. Recovery is that of a transPRK: a few days of discomfort while the surface heals over.

How I proceed

I first map your cornea to locate the condition and measure its impact. It is this assessment that shows whether simple measures are enough, or whether PTK would bring a benefit, and which one. Follow-up then makes it possible to detect any recurrence in good time.

Painful mornings, fluctuating vision?

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Cogan’s dystrophy is a common cause of erosions

Recurrent erosions →

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PTK — corneal surface →