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.
Table: Late-onset Iatrogenic Keratectasia After LASIK in Pregnant Women
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. Scheimpflug 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.
Figure. Corneal topographies of unilateral central keratectasia. A) Preoperative topography shows no signs of keratectasia on the anterior corneal surface. B) Eight years after LASIK and 1 year after delivery, central keratectasia is noted. C) Twelve months after subsequent cross-linking, significant regression occurred.
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 identified 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 exposed to high doses of estradiol. Aside from estrogen, other hormones such as cortisol and thyroxin show substantial changes during pregnancy and may also alter corneal biomechanics.6
Borderline corneas with the risk of developing keratectasia during pregnancy need to be identified pre-operatively and the Ectasia Risk Score System (ERSS) may help characterize such biomechanical configura-tions.7 Because of the limited preoperative data, correct application of the ERSS in the patients presented herein was not possible, but at least 2 patients were at moderate risk (ERSS >2) preoperatively. Based on only five cases, a general recommendation to consider future pregnancy a potential risk factor of LASIK is not appropriate; however, in our clinics the counseling of LASIK in female patients younger than 40 years with an ERSS ⩾2 will include the additional risk during pregnancy.
Future systematic studies should investigate the effect of pregnancy on corneal biomechanics. Pregnancy may stimulate progression of corneal keratectasia years after LASIK. This risk should be included in the benefit-risk analysis prior to LASIK in borderline cases.
Farhad Hafezi, MD, PhD
Tobias Koller, MD
Victor Derhartunian, MD
Theo Seiler, MD, PhD
- Hafezi F, Kanellopoulos J, Wiltfang R, Seiler T. Corneal collagen cross-linking with riboflavin and ultraviolet A to treat induced keratectasia after laser in situ keratomileusis. J Cataract Refract Surg. 2007;33(12):2035–2040. doi:10.1016/j.jcrs.2007.07.028 [CrossRef]
- Hafezi F, Iseli HP. Pregnancy-related exacerbation of iatrogenic keratectasia despite corneal collagen crosslinking. J Cataract Refract Surg. 2008;34(7):1219–1221. doi:10.1016/j.jcrs.2008.02.036 [CrossRef]
- Padmanabhan P, Radhakrishnan A, Natarajan R. Pregnancy-triggered iatrogenic (post-laser in situ keratomileusis) corneal ectasia—a case report. Cornea. 2010;29(5):569–572. doi:10.1097/ICO.0b013e3181bd9f2d [CrossRef]
- Suzuki T, Kinoshita Y, Tachibana M, et al. Expression of sex steroid hormone receptors in human cornea. Curr Eye Res. 2001;22(1):22–33. doi:10.1076/ceyr.18.104.22.16880 [CrossRef]
- Spoerl E, Zubaty V, Terai N, Pillunat LE, Raiskup F. Influence of high-dose cortisol on the biomechanics of incurbated porcine corneal strips. J Refract Surg. 2009;25(9):S794–S798. doi:10.3928/1081597X-20090813-06 [CrossRef]
- Gatzioufas Z, Thanos S. Acute keratoconus induced by hypothyroxinemia during pregnancy. J Endocrinol Invest. 2008;31(3):262–266.
- Randleman JB, Woodward M, Lynn MJ, Stulting RD. Risk assessment for ectasia after corneal refractive surgery. Ophthalmology. 2008;115(1):37–50. doi:10.1016/j.ophtha.2007.03.073 [CrossRef]
Late-onset Iatrogenic Keratectasia After LASIK in Pregnant Women
|Patient No.||Age at LASIK (y)||Age at Onset (y)||Occurrence After LASIK (y)|