Q by Doctor Randy:
I have not seen the patient yet, but was called by a colleague who wanted to refer a 55 year old patient with the above to me for “corneal laser treatment”. I asked of the patient had any ocular surface disease/recurrent erosions, and was told that the only problem was decreased acuity form the opacities themselves. No irregular astigmatism, no cataracts.
How would those of you advise those of us who only have access to “USA technology” to proceed to treat such a patient?
A by doctor Will:
I have performed PTK on a handful of Granular Dystrophy patients who were experiencing reduced vision The problem in Granular Dystrophy is that the opacities are breaking through the anterior stromal surface. Removing the epithelium reveals a highly irregular surface
The goal with PTK is to just smooth out the surface, not eliminate opacities.
After smoothing out the stromal surface with PTK – patients will note improved vision – both on Snellen testing as well as report improved quality of vision
Following the PTK – There will be plenty of opacities remaining.
Overall – the PTK procedure should be a very superficial treatment. I have had one patient require a repeat PTK 6-7 years after the first treatment – and I expect that the PTK lasts for 5-10 years, depending on the patient. So focusing as much on corneal smoothing while preserving as much corneal tissue is key, in my opinion.
I hope this helps
Answer by Emil Chynn, MD:
When we treat granular dystrophy or scars, as long as there’s a significant refractive error, we try to treat that, too. Then the issue always arises re if abnormal tissue ablates at a faster or slower rate than normal cornea stroma
We (meaning myself and the various doctors who’ve worked with me) have concluded this is impossible to predict. So then we just shoot our normal nomogram. And have been pleasantly surprised that our refractive outcomes have come out close to plano
Regarding differential ablation rates and leaving bumps and lumps, if you employ a PRK nomogram and ablation profile, as long as your scars are mostly central and superficial, you wind up shaving off a substantial amount of the opacities. I’ve used many different agents to mask, and now there are dozens of tears out with varying viscosities. Unfortunately the predictability of outcomes when using any masking agent is lower than if you don’t use one.
Luckily as many of us have pointed out the epithelium can cover and mask a huge amount of surface irregularity. Therefore after myopic ablation, since you’re creating a “top hat” profile afterwards, it seems like the epithelium is more able to cover up the residual pathology than the original pathology, because the epithelium is going to try to recreate a more normal “dome” shape. There’s also epithelial hyperplasia, which can be encouraged with topical NSAIDs. So these are two often-ignored factors that contribute significantly to a smoother front refractive surface after PRK of opacities, even without using a masking agent in an attempt to differentially and preferably ablate scars or dystrophic deposits over normal stroma