Pregnancy may trigger late onset of keratectasia after LASIK.

To the Editor: It is common knowledge that the biomechanical stability of connective tissue changes during pregnancy, leading to reduced stiffness and increased extensibility. These changes are most probably hormone-induced and, therefore, corneal biomechanics also may change during pregnancy. Five patients who underwent LASIK experienced vision deterioration during pregnancy, which we attribute to iatrogenic keratectasia although the cornea prior to pregnancy was stable for years. All patients except one were primapara. All patients showed progressive keratectasia and received corneal collagen cross-linking (CXL) to stop progression.1 Patient age and time of onset of iatrogenic keratectasia are shown in the Table. Representative case: A 32-year-old woman underwent bilateral LASIK in Turkey for 5.00 diopters (D) in the right eye and 4.50 D in the left eye in 2002. Preoperative topography is shown in the Figure. According to the patient, the surgeon stated that uncorrected distance visual acuity (UDVA) was 20/20 in both eyes at 6-month follow-up. Postoperative UDVA remained stable for 6 years until her seventh month of pregnancy in July 2008. Scheimpfl ug analysis showed keratectasia in the right eye with Kmax values of 51.60 D and a minimal corneal thickness of 359 μm, compared to 45.30 D and 398 μm and normal topography in the left eye. Our results suggest that, aside from misinterpretation of preoperative topography and low residual stromal thickness, additional factors may induce iatrogenic keratectasia under certain circumstances. We cannot rule out that some of the cases could have had a preexisting minimal corneal thickness at the lower end of the normal distribution (ie, 505 μm), a minor asymmetry and elevation at the posterior pole (ie, 12 μm at a reference sphere of 8 mm), or even keratoconus. These corneas might have been borderline compensated and biomechanically stable until an additional factor arose, eg, the increase in serum estrogen levels during pregnancy. This may explain why ectasia occurred up to 9 years after LASIK concomitant with pregnancy. Only a few cases of iatrogenic keratectasia and keratoconus occurring during pregnancy have been reported, with one included in this series.2,3 There is growing evidence that the massive estrogen increase in late pregnancy not only prepares the female body for birth but may also increase the risk of keratectasia in predisposed individuals. Suzuki et al4 identifi ed estrogen receptors in the human cornea, and Spoerl et al5 have demonstrated that ex vivo porcine corneas show a distinct reduction in biomechanical stiffness when exTABLE