PRK for atypical corneas?

The issue of PRK or LASIK for patients with atypical corneas is extremely important for medical and legal reasons. Many experienced ophthalmologists have relied on Pentacam and Orbscan images to determine whether a patient with form fruste keratoconic findings on standard anterior curvature computerized video-keratography is suitable for LASIK or PRK. Following the link below you will see screen capture topography images of two patients.

Patient one underwent PRK OD for high cylinder plano - 5.00 x 020 (pre-op pach 565 microns OD) Her anterior topography you can see by following the link below and I dont have her color orbscan scanned but the posterior float is 0.030 at the central 3 mm optical zone with a normal pachymetric pattern. Her most recent refraction OD postop year 6 is is +3.50 - 2.0 x 020 (20/30)

Patient two had a thin cornea, 473 microns OD, 463 microns OS.
Preop MRX: -2.50 -3.50 x 020 OD and -2.50 -3.50 x 163 OS (2004)
Topos are available by clinking on the link below.
1 week postop: plano OD and plano OS
2 year postop: -0.50 -1.50 x 20 OD and plano - 1.50 x 160 OS



The above two cases are limited anecdotal case reports to suggest perhaps we should exercise caution in offering PRK to patients with atypical corneas in the form of thin pachymetry (less than 500 microns) and/or atypical corneal curvature.

In both cases above, each patient was consented regarding the potential for ectasia development. I think it is interesting to observe the time frame for refractive instability and the speed at which that change occurrs. When patients observe slow gradual change they actually tolerate this type of instability much better than rapid decompensation in the 3 to 6 month range.

Hopefully collagen crosslinking procedures can offer some form of stability either pre or postoperatively in these complex cases. In the mean time I offer these patients matrix metalloproteinase modulation (tetracycline class), mast cell stabilization, and Alphagan intraocular pressure reduction with mild miosis (avoid prostaglandin analog).

If the patient has any underlying risk factors for ectasia such as sleep apnea or eye rubbing, I attempt to address these issues as well.

OCT the new titanic?

Recent kera-net discussions led me to the conclusion that embracing new technology always runs the risk of discarding effective old technology. Unfortunately the learning curve of new technology may require us to make 2 diagnosis forward but 1 diagnosis back.

Post cataract surgery cystoid macular edema (CME) is a major problem with an incidence of 1 to 10% depending on how it is defined.

Optical coherence tomography (OCT) is an advanced retinal imaging diagnositc modality believe to refine the diagnosis of this postoperative CME. Unfortunately the patient may have visual complaints with a negative OCT scan but a positive pattern of cystoid macular edema with flourescein angiography.

The patient in question had visual acuity of 20/50 - OD and OS with a monofocal intraocular lens with routine uncomplicated phacoemulsification. Think about what a multifocal intraocular lens patient would complain about with a similar or lesser amount of OCT negative, FA positive CME.

Click on the link below to see the images in the picassa web album.



The titanic was unsinkable and so is every new technology in Ophthalmology. If you look at the images on the slide show you may have seen the first iceberg hit the "new" titanic.

Special thanks to Dr. Elias Mavrofrides of the FLorida Retina Institute.
http://www.floridaretinainstitute.com/index.html