ECTASIA

A study examining the physiology of the human cornea during pregnancy and after delivery is nearing completion, Farhad Hafezi MD, PhD of Geneva University Hospitals, Switzerland, told the 2013 ESCRS Congress in Amsterdam. It focuses on the role of increased oestrogen on corneal biomechanics during pregnancy which has been observed during pregnancy as much as nine years after LASIK.

The study began in 2011 and concludes this year, Dr Hafezi said. It is examining corneal physiology using Scheimpflug imaging to detect changes in topography as well as the Ocular Response Analyzer (Reichert Technologies, Buffalo, NY, US) and Corvis (Oculus, Wetzlar, Germany) to measure changes in corneal biomechanics. Oestrogen levels are also being recorded and correlated with corneal biomechanical changes.

The study builds on previous findings of oestrogen receptors in the cornea and of the fact that oestrogen may upregulate collagenases via prostaglandin release, Dr Hafezi said. Oestrogen exposure reduces biomechanical strength in vitro, and pregnancy-related exacerbation of keratoconus and iatrogenic keratectasia have been reported.

“Pregnancy may affect biomechanically borderline corneas,” he said.

Dr Hafezi recounted an early case he observed. A 33-year-old woman had LASIK in late 2000, and her vision remained stable for over two years. In early 2003 she became pregnant and reported a decrease in vision. Examination revealed a shift from 20/20 uncorrected to 20/63 with -3.5 sphere and -4.0 cylinder at 90 degrees in her right eye, and 20/50 with -5.0 sphere and -4.5 cylinder at 140 degrees in her left. Kmax values in her right eye had climbed from 41.3 after surgery to 44.0 by the end of her pregnancy.

“We didn’t dare touch a pregnant woman with corneal cross-linking (CXL), so we followed her,” Dr Hafezi said. Her ectasia continued to progress, with Kmax reaching 49.3 in January 2005, when she was treated with crosslinking. Her ectasia then regressed. When she became pregnant again in February 2007, her right eye visual acuity again deteriorated sharply, and her Kmax rebounded from 46.4 to 49.0 (Hafez et al. JCRS 2008).

A second case series by Dr Hafezi and colleagues examined five cases of late-onset post-refractive ectasia in pregnancy, ranging from four to nine years after LASIK. All five were treated successfully using standard protocol CXL (Hafezi et al. J Refract Surg. 2012 Apr;28(4):242-3).

“CXL after pregnancy gives amazing results,” Dr Hafezi said. However, additional research is needed to identify risk factors for pregnancy-related ectasia.

Farhad Hafezi: farhad@hafezi.ch