IntraCor what you need to know
All corneal refractive surgery involves shaping of the cornea.
IntraCor was developed by Dr Luis Ruiz, a Columbian surgeon. The aim was to increase the central multifocality of the cornea so that people who need reading glasses could read better without compromising their distance vision. It uses a femtosecond laser to deliver a series of concentric circular cuts within the corneal stroma. It preserves the anterior corneal fibres and Bowman’s layer. The pattern of concentric cylinders creates a hyper prolate corneal shape to enhance near vision. No tissue is removed by these intracorneal cuts and the effect is entirely biomechanical.
As well as Dr Ruiz, Dr Holzer and other colleagues in Germany have reported short follow up of three months in a small number of eyes using this technique. The German data showed a loss of two or more lines of corrected distance visual acuity in 8% of eyes at three months. This was worse than the Columbian data. The majority of patients also reported symptomatic halos at night. These halos improved with time.
This is an appealing technology, but has two real limitations preventing its use at present;
Firstly, the accuracy of the procedure: When an excimer laser is used to remove corneal tissue it is extremely precise and it is known how the cornea responds. When a femtosecond laser is used to alter the biomechanics of the cornea, as in IntraCor, the accuracy of the biomechanical response is unpredictable.
The second and more serious issue is one of medium and long term safety. The most feared complication of LASIK is producing ectasia, or weakening of the cornea, which occurs rarely these days. It occurs rarely because patients at risk of developing this; eg with thin or abnormal corneas, are excluded.
IntraCor is deliberately designed to use the biomechanical properties that produce ectasia to be altered in a way that changes the shape of the cornea.
It is the unknown regarding the possibility of producing unpredictable biomechanical weakening of the cornea with IntraCor, which means that it is not used routinely by ophthalmic surgeons. (Kruger RR October 2009. Journal of Refractive Surgery: 25:836-840)
