Corneal surface

Phototherapeutic
keratectomy (PTK)

Treating a cornea damaged at the surface with the laser — without, this time, aiming to correct your glasses.

Phototherapeutic keratectomy, or PTK, is an excimer laser procedure. It removes a very thin layer from the surface of the cornea to treat a localised condition: an opacity, an irregularity, or a superficial layer that no longer adheres properly.

The distinction is essential. The same laser that, in refractive surgery, reshapes the cornea to change its focus serves here a different purpose: to restore a healthy, regular and comfortable surface. This is not about freeing you from glasses, but about treating the cornea itself.

The same tool, two intentions

In refractive surgery (LASIK, transPRK), the laser sculpts the cornea to correct myopia, hyperopia or astigmatism. In PTK, it acts on a cornea whose problem is not its focus but the state of its surface: a diseased superficial layer is removed or smoothed to restore clarity and regularity.

The same excimer laser, two intentions: refractive and therapeutic Two corneal cross-sections compared, each under an identical excimer beam. On the left, refractive intent: the tissue removed, shown as a dashed hatched outline, is lens-shaped — thickest at the centre and tapering to nothing at the edge; the original, steeper surface is recalled as a dashed line above the new, flatter surface. The curvature is therefore changed. On the right, therapeutic intent or PTK: the tissue removed forms a layer of constant thickness that takes the superficial opacities with it; the original and new surfaces stay parallel, so the curvature is preserved. Each section shows the epithelium, the basement membrane and the stroma. Refractive intent reshaping the curvature The curvature is changed. Tissue is removed as a lens, thicker at the centre, to change where the eye focuses. Therapeutic intent — PTK treating the surface The curvature is preserved. A layer of constant thickness is removed, taking the surface irregularity with it. Epithelium Basement membrane Stroma Tissue removed The beam is the same: what differs is the profile of tissue removed.
One laser, two intentions The excimer laser according to the goal pursued: reshaping the curvature (refractive) or treating the surface (PTK).

What PTK can treat

PTK addresses well-identified superficial conditions. Three situations arise most often.

01

Cogan’s
dystrophy

Epithelial basement membrane dystrophy — an abnormality of the layer on which the epithelium, the cornea’s surface covering, rests. It can cause erosions and fluctuating vision.

Cogan’s dystrophy →
02

Recurrent
erosions

Repeated breaks in the epithelium, often painful on waking, linked to insufficient adhesion of this layer.

Recurrent erosions →
03

Irregular corneas
and opacities

Raised areas, deposits or scars at the surface: Salzmann’s nodular degeneration, band keratopathy, superficial after-effects.

Irregular corneas and opacities →

How the procedure is carried out

PTK is carried out under local anaesthetic, using drops. After removing the surface epithelium manually or with the laser, I use the excimer laser to treat, over a few microns, the superficial layer concerned. When the surface is irregular, a smoothing gel (masking agent) can be applied to help the laser even out the relief. The epithelium can also serve as a natural masking agent during a first pass of the laser.

A protective contact lens is placed at the end of the procedure. The cornea then rebuilds its epithelium over a few days — a phase comparable to recovery after transPRK: transient discomfort, watering and light sensitivity while the surface heals over. Close follow-up accompanies this healing.

Stated plainly

What PTK does not do

An informed decision means knowing the limits as much as the benefits.

It treats the surface, not the cause.

Some conditions — dystrophies in particular — may return over time, because their underlying mechanism remains. PTK can then be repeated. This is something to factor in, not an unexpected event.

It can change your correction.

By removing tissue at the centre of the cornea, PTK tends to flatten it slightly, which can shift vision towards hyperopia. This hyperopic shift can be anticipated: it can be reduced, or built into the strategy by combining, where relevant, a therapeutic step and a refractive step (a combined PRK).

It only applies to superficial conditions.

A deep opacity is not a matter for PTK, but for other solutions, up to a lamellar graft.

Doing nothing, or treating differently, is sometimes the right choice.

Many situations are managed first with simple measures — lubrication, a contact lens, topical treatment. PTK comes into play only when these measures are not enough, or when the discomfort warrants it.

How I proceed

Before any PTK, I map your cornea — topography, thickness measurements (pachymetry) — to locate the condition precisely and gauge its impact on vision. It is this mapping that determines the depth of treatment, whether a correction should be combined with it, and the outcome one can reasonably expect. Follow-up, afterwards, is part of the procedure: the surface is monitored, and any recurrence is managed in good time.

A condition of the corneal surface, or an opinion to compare?

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To understand refractive laser surgery

Laser surgery — overview →

Irregular cornea after previous surgery (radial keratotomy)

Have you already had eye surgery? →
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