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This abstract is assigned to session AOB: Academia Ophthalmologica Belgica

Title	Outcomes after 6 year follow up, retrospective study of corneal collagen cross linking in corneal ectasia.
Abstract Nr.	1021

Purpose	To assess the long term effects of corneal cross linking (CXL) and possible prediction factors.
Methods	Prospective, nonrandomized study. 273 eyes of 213 patients with progressive keratoconus (n=210) and post Lasik ectasia (n=3) were included and treated with CXL at the University Hospital Maastricht from 2007 until 2014. Refraction, best corrected visual acuity (BCVA), corneal topography, pachymetry and endothelial cell density were performed at baseline and at 1, 3, 6 and 12 months, and yearly thereafter for 6 years.
Results	The mean preoperative age was 29±10 years. The mean follow up period was 21±18 months. The steep keratometric value (preoperative: 50.2±5.1D) decreased significant after CXL to 49.6±4.7D and 48.1±5.4D after 1 (n=165) and 5 years (n=15), respectively. The mean keratometric value (kmean) (preoperative: 48.3±4.9D) decreased significantly after CXL to 47.7±4.85D and 45.9±4.7D after 1 (n=161) and 5 years (n=14), respectively. The BCVA improved significantly (>1line) in 83.3% (120 eyes of 144 eyes) in the first year and stabilized thereafter. Linear mixed model analysis (LMMA) demonstrated that higher preoperative Kmean was correlated with a the stronger flattening of the cornea. Secondly, a LMMA showed that the more severe preoperative LogBCVA, the more visual improvement after CXL was seen. After one year 18 eyes showed progression (11.5%). None of these patients were treated for a second time.
Conclusion	Retrospective long term follow up data showed the efficacy of the procedure in reducing the keratometric values and visual improvement. The preoperative value of Kmean and Logmar BCVA are predictive factors for the change of Kmean and Logmar BCVA in time.

Authors 1

Last name	Ayvaz
Initials	A
Department	University Eye Clinic Maastricht (UECM)
City	Maastricht

Authors 2

Last name	Saelens
Initials	IEY
Department	UECM
City	Maastricht

Authors 3

Last name	Berendschot
Initials	TTJM
Department	UECM
City	Maastricht

Authors 4

Last name	Dickman
Initials	MM
Department	UECM
City	Maastricht

Authors 5

Last name	Visser
Initials	N
Department	UECM
City	Maastricht

Authors 6

Last name	Nuijts
Initials	RMMA
Department	UECM
City	Maastricht