DEC 05, 2011
This retrospective case series published in the November issue of Cornea describes the long-term postoperative results of five patients (five eyes) diagnosed with central toxic keratopathy (CTK) after photorefractive keratectomy (PRK). They were part of a group of 74 eyes treated with PRK or LASIK during a two-month period. The authors conclude that these patients may have experienced unexpected primary stromal dehydration secondary to an unknown pharmacological reaction.
The patients diagnosed with CTK, a term used to describe steroid-unresponsive stromal thinning following laser refractive surgery, experienced corneal stromal thinning associated with central opacification (haze), hyperopic shift and central striae during the first postoperative week. All epithelial defects were healed by day three, when the bandage contact lens was removed. Central corneal thickness measured by ultrasound one month postoperatively showed stromal thinning of 48 +/- 39 (range 19-116) microns compared with expected postoperative values. Extended topical steroid application did not seem to affect CTK progression.
Haze and corneal thickness improved over several months and stabilized after six months. At the last postoperative visit, corneal thickness had gained 44 +/- 22 (range 20-80) microns compared to the postsurgical measurement. There was a hyperopic shift at one month, which improved in all eyes at six months, although two eyes still had greater than 1 D (spherical equivalent) of hyperopia at 12 months. Uncorrected visual acuity improved compared to preoperative levels in all eyes but did not achieve maximal levels until six to 12 months. Best-corrected visual acuity (BCVA), on the other hand, decreased at one month postoperatively and gradually improved afterward. One eye lost two lines of BCVA and another eye lost one line.
Around the time when these cases were performed, the surgeons had changed their postoperative topical steroid regimen and aborted their practice of rinsing the contact lens prior to application on the cornea. The authors hypothesize that the contact lens storage solution used may have resulted in CTK.
They say that the use of steroids in these patients did not improve clinical outcomes and could have had an adverse effect by further enhancing corneal thinning. In eyes that have experienced CTK, they suggest waiting at least 12 to 18 months after the initial surgery before performing postoperative enhancement to correct corneal irregularities because of the high rate of spontaneous recovery.
They recommend carefully rinsing a bandage contact lens prior to use after PRK or in a post-LASIK eye with an epithelial defect. They say that the use of nonsteroidal anti-inflammatory drugs after PRK or LASIK should be minimized. Drugs other than antibiotics probably should be introduced only after the epithelium has healed and the bandage contact lens removed. The authors report no further complications since implementing these guidelines.