Arun C. Gulani, MD, explains his concept of addressing anterior corneal scars with laser PRK (not PTK) straight to 20/20. In the next article, he will explain how to build the cornea with various modalities in presenting it for laser PRK.
My desire in these invited columns is simple—to change ophthalmologists’ mindset! To free eye surgeons from the burden of technology and terminology.
When looking at a corneal scar, our inherent mindset is: “There is the culprit. Let’s eradicate it.” Numerous diagnostic technologies are then deployed to “understand the scar and its obviously criminal impact on vision.”
Then—in their minds—many ophthalmologists go through an elegant and complicated thought process to determine whether to choose laser PTK (an optically incorrect surgery), diamond burr application (a barbaric procedure on an elegant visual organ), or a corneal transplant (a relatively interventional procedure that should be the last resort, very much like having to open the entire abdomen to get to the gall bladder) as the correct treatment for this corneal scar.
What I suggest instead is to look at the corneal scar and ask yourself, “How can I use this or modify this to help the patient see better with the least intervention?” and “Is it necessary to remove this and at what cost?”
By cost, I mean, the cost in “vision” currency. Chasing the scar at the cost of vision is not acceptable.
In this article focusing on corneal scars, I will explain my concepts of addressing anterior corneal scars with laser PRK (not PTK) straight to 20/20. In part 2, I shall explain how to build the cornea with various modalities in presenting it for laser PRK.
Anterior corneal scars affect vision directly by blocking the optical pathway and indirectly, by altering the shape, and hence the refractive status. Using “Corneoplastique” principles, we can use these very factors and reverse them to our advantage.
In the Gulani 5S algorithm, you can see the impact of the corneal scar on vision and determine the patterned approach of corneal rehabilitation and laser or direct laser, and straight reshaping to vision. The refraction is the mainstay of the corneal scar algorithm, where vision better than 20/30 suggests straight laser PRK; whereas less than 20/40, following a hard contact lens trial, can determine staged laser in two stages or a scar peel, followed by myopic ablation.
For the sake of simplicity, I have divided corneal scars into “on-cornea” scars, which are above the Bowman’s membrane and lead to a camouflaged topography and misleading refractive error and “in-cornea” scars, which actually become part of the cornea and are directly responsible for the topography, and have a direct correlate to the refractive error. These can be lasered through.
Instead of laser PTK, which chases the scar and distorts the shape (costing us in vision currency), why not reshape the cornea and take it straight to vision (in many cases, despite a residual scar)?
For example, one of my patients (see related video) presented with a case of dense corneal scar following herpetic infection 20 years ago. You can see the circular light reflex from the excimer laser seen as D-shaped, due to high astigmatism. After removal of epithelium and confirming “in-cornea” status (herpetic scars usually become part of the cornea, thus producing a smooth surface once the epithelium is removed), I proceeded with a refractive laser ablation, and then applied mitomycin-C for 30 seconds to the central cornea. Upon application of balanced saline solution, the light reflex had become circular, which translates to vision. This patient ended with uncorrected vision of 20/25+ and was thrilled with her outcome.