Closing One's Eyes In Solat ?

It is Makruh (reprehensible) to close the eyes during Solat.

However, one is excused when there absolutely no way a person may obtain concentration whilst having his eyes open. Still - one must understand that continuous practice of this may deprive a person of the great blessings and Nur of praying the way the Prophet Muhammad SAW prayed.

If someone finds it difficult to concentrate in Solat without closing the eyes, one may semi-close the eyes for a start.

The way of the Prophet Muhammad SAW was that he would focus his eyes at the place of sajadah during solat whilst in the standing position. We must try our best to conform as only in his (SAW) way is success in this world and the Hereafter.