Glare, Halo After PRK Despite Good Refractive Result

CASE PRESENTATION

FRANCESCO CARONES, MD
This eye presents with a fairly decentered ablation performed with a relatively small optical zone size over a relatively large low-mesopic pupillary entrance. We do not know whether the PRK performed for this high refractive correction induced significant stromal reaction leading to haze formation; however, the symptoms reported and depicted by the patient seem to be mostly related to induced coma and spherical aberration as detected by wavefront analysis.

This situation could be easily managed with an orthokeratologic approach by prescribing a gas-permeable contact lens, but obviously this is not what the patient would like to have. The Scheimpflug camera shows the cornea to be thick enough to allow enhancement. If undertaken, this would have to be customized and targeted at reducing higher-order aberrations—primarily coma and spherical aberration.

To manage this case, I would suggest performing a corneal wavefront-guided PRK using the Amaris excimer laser platform (Schwind Eye-tech-solutions, Kleinostheim, Germany) and the Keratron corneal topographer (Optikon 2000, Rome). My reason for choosing this particular platform is that it provides accurate registration of the measured wavefront during the ablation and a fast and active tracking process, which is also able to compensate for cyclotorsional misalignment.

Given the degree of higher-order aberrations detected by total wavefront analysis, I assume the ablation depth would not be less than 50 µm to correct these errors over a 7-mm diameter optical zone size, yet to leave sufficient residual stromal thickness. To avoid risk of haze formation, I would use prophylactic mitomycin C 0.2 mg/mL, applied for 30 seconds at the end of ablation using a soaked Merocel sponge.

JOSE L. GÜELL, MD
Confronted with such a situation, I would like to have two questions answered: (1) What is the patient's concept of fewer problems in his right eye? Does this mean that the patient is not concerned significantly with his right eye and is seeking treatment only for the left? (2) Do we have any idea of the rationale for performing PRK on the left and LASIK on the right eye? It would also be helpful to know the correction in the right eye, so that we can roughly calculate the residual keratometry (K) readings and compare with the left. (The K readings were quite flat in this eye.)

Taking into account that I do not have this information, I will only suggest some comments. (1) It is relatively common to have optical quality complaints when lamellar refractive surgery is performed in one eye and surface ablation in the other. (2) It is also common to have complaints in patients with obvious postoperative aniseikonia—clearly different K readings in both eyes. (3) One possibility could be to suggest wavefront-guided treatment at the same time as correcting the residual astigmatism with a large optical zone. However, taking into account the actual visual acuity and the associated risk of residual haze after a PRK reoperation, I would avoid that. On the other hand, the use of mitomycin C at the time of the ablation might help reduce haze. (4) I would encourage this patient to positively consider both what he has (current UCVA) and what he may lose with a reoperation.

A. JOHN KANELLOPOULOS, MD
This case has not been treated yet. I have waited a good 6 months for some slight corneal haze to subside.

The only irregularity on the patient's diagnostic imaging that I consider important is the slightly decentered ablation evident in the Scheimpflug maps, which corresponds with the oblique coma in the wavefront maps. I will therefore consider performing a customized retreatment using one of the following options: (1) A wavefront-guided treatment, which would enlarge the optical zone, address the coma, and hopefully ameliorate the unwanted visual symptoms. (2) A topography-guided treatment, which would recenter the optical zone and possibly enlarge it. This approach has the advantage that it would not take into account noncorneal aberrations, but the disadvantage that it may throw off the final refraction—it may make the eye slightly myopic if the neutralization of the optical zone enlargement is not perfect. A trial with a rigid gas permeable contact lens may better elucidate options 1 and 2. The patient is contact-lens intolerant. (3) An asphericity-adjusted treatment, which may enlarge the effective optical zone and improve asphericity, reducing spherical aberration. The disadvantage with this technique is that it will not address any central corneal irregularity and therefore will do nothing for the coma.

Francesco Carones, MD, is the Cofounder and Medical Director of the Carones Ophthalmology Center, Milan, Italy. Dr. Carones states that he has no financial interest in the products or companies mentioned. He is a member of the CRST Europe Editorial Board. Dr. Carones may be reached at +39 02 76318174; fcarones@carones.com.

Jose L. Güell, MD, is the Director of the Cornea and Refractive Surgery Unit at the Instituto de Microcirugía Ocular, Barcelona, Spain, and an Associate Professor of Ophthalmology at the Universitat Autónoma de Barcelona. Dr. Güell states that he is a consultant to Carl Zeiss Meditec AG. He may be reached at +34 93 253 15 00; guell@imo.es.

A. John Kanellopoulos, MD, is a Clinical Associate Professor of Ophthalmology at NYU Medical School and Director of the Laservision.gr Institute in Athens, Greece. Dr. Kanellopoulos is on the CRST Europe Editorial Board and is Section Editor for the Refractive Complications column. He states that he has no financial interest in the companies or products mentioned. Dr. Kanellopoulos may be reached at www.brilliantvision.com.