Dr. Chynn has the most Refractive Fellows working for him of any surgeon in NYC. In fact, Park Avenue LASEK is the largest Refractive Fellowship Program in NYC! We have 4 Refractive Fellows at all times, 2 Senior Fellows and 2 Junior Fellows. All are full MDs! They have chosen to spend 1-2 years learning the intricacies of Refractive Surgery from Dr. Chynn, since he was at Columbia when the excimer laser was invented, and at Harvard when LASEK was invented. So they can learn from a true pioneer!
Why we safely treated the highest Rx ever lasered in NYC: -22.00! And why LASIK is unsafe for extreme Rxs.
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Dr. Chynn is recognized as a National Expert in Refractive Surgery – read this article to see his advice to other laser surgeons.
In this article, 3 national “thought leaders” including Dr. Chynn were asked their opinion on how to treat a complicated case. Dr. Chynn advocates using the VISX WaveScan CustomVue to create a PreVue lens. Using the PreVue lens, Dr. Chynn can show complicated patients (e.g., LASIK patients with flap complications) how they would see after he fixes their problem by performing a totally non-invasive, surface LASEK over their prior (failed) LASIK.
This case is interesting both for its complexity and realism, as it demonstrates a common situation encountered by the refractive practitioner–namely, the situation of a patient presenting with incomplete records, having had surgery elsewhere, and desiring further surgery, ” but only if it’s safe.”
The patient has had prior refractive surgery OD for a metallic foreign body scar–either a PTK or a PRK. He reports ghosting or monocular diplopia in that eye, which is most likely due to his superiorly decentered ablation with respect to the optical zone, which can be seen on his topography OD. Again, it is difficult to be certain if this represents the postoperative result of an intentionally decentered PTK to remove his scar, or an unintentionally decentered PRK to remove his scar and simultaneously address his refractive error. I would guess the former, although as a rule I prefer to treat such cases with a PRK, as in my hands the final refractive result is more predictable and patient satisfaction higher after performing a PTK with an (uncontrolled) hyperopic shift.
We can address OD as if it’s simply a (complicated) refractive case. The cornea is clear, so although I think we would all agree that the chances of scarring in a surface ablation is always higher in retreatments, I do not think this risk is significant. That said, I always try to minimize this risk in surface retreatments by giving oral steroids, branded Pred Forte, and intraoperative MMC.
The other safety consideration for reoperating OD is answered by the Orbscans, which shows sufficient corneal thickness both centrally and peripherally for the rather minor intended refractive treatment, with no signs of keratoconus OU.
The question then arises whether one can successfully treat this situation simply with standard wavefront algorithms, or whether decentered ablations are best treated with a specialized retreatment algorithm or topographically-guided ablation, one of which is available from each of the major laser manufacturers.
Reviewing the CustomVue map OD, the fact that higher order aberrations comprise 56% of total error is neither impressive nor concerning to me, since the underlying refractive error is quite minor, with a spherical equivalent of only -0.51. I actually wish that this percentage was somehow normalized for spherical equivalent, as I think such a index would be more useful clinically when comparing aberrated eyes.
More importantly, the WaveScan refraction of +0.20 – 1.41 x 142 is similar to the hard lens over-refraction of +0.75 – 0.75 x 180. This reassures me that the WaveScan is objectively measuring a global refractive error similar to what the patient is experiencing subjectively.
Before retreating this or any complicated patient, I like cut a PreVue lens and have the patient hold it up, documenting both his objective improvement in visual acuity, as well as subjective improvement in symptomatology. In this case, I would need to see at least a 1-line improvement of acuity to 20/25, as well as a significant subjective improvement of his ghosting/diplopia OD. In my practice, a PreVue lens that demonstrates both objective and subjective improvement will usually lead to a visual outcome that is satisfactory from a patient point of view. I am a strong proponent of using the PreVue capability of the VISX system, which I believe is underutilized. Beware of performing complicated enhancements without a PreVue lens, or where vision out of the PreVue does not show both objective and subjective improvement!
In CustomVue retreatments, I am more hesitant to adjust treatment parameters, particularly the physician adjustment, because I feel that the results of doing so are more unpredictable than in primary treatments. Another reason I don’t like to adjust these cases is that I commonly utilize the PreVue feature, which makes less sense when you then wind up shooting something dissimilar to what you PreVued. This is why I like that the WaveScan refraction is similar to my manifest, so I don’t feel I need to adjust it. If it is very different, I will just try to keep capturing WaveScans until I get one that is similar to what I think I “need.”
In terms of staging, the question arises whether to operate on OD or OS first. I never operate OU in enhancements, both for prudence and medical-legal reasons. In this case, I would actually leave this decision up to the patient, as either choice seems reasonable medically.
I could perform LASEK or epi-LASEK OS (I only perform advanced surface ablations), make that eye 20/20 or potentially better, eliminate his anisometropia, and by doing so actually reduce his symptomatology, since his uncorrected vision with both eyes open would excellent. I have staged many cases like this, and a significant minority of patients will then decline to have further surgery on the fellow (abnormal) eye, after gaining good functionality.
On the other hand, most patients would elect to operate on OD first. I would then counsel them about their increased risk of scarring from a second surface procedure, as well as steps we would take to reduce this risk. I never promise the patient that his final result in the reoperated eye will be as good as in the fellow eye, or perfect, because what we are actually trying to do is fix an “imperfect, damaged” eye. However, provided I have postive results from the PreVue lens, I would tell the patient that his visual acuity should improve, and his subjective symptoms should somewhat diminish.
In terms of which advanced surface procedure to perform, I would only perform a LASEK, not an epi-LASEK in such cases, because of the slightly increased risk of an intra-stromal incursion by the epi-LASEK separator in retreatments and cases with prior foreign bodies, which I have seen.
By carefully reviewing the preoperative data, confirming the safety of a reoperation, utilizing the PreVue lens feature, appropriately staging the two procedures, and managing patient expectations, I would be fairly confident that this patient could be retreated with a standard CustomVue ablation, with highly satisfactory results.