First see the following verse from Quran:
الَّذِينَ هُمْ فِي صَلَاتِهِمْ خَاشِعُونَ
Those who humble themselves in their prayers [23:2]
In its interpretation have come the followings:
و روى ان رسول الله صلى الله عليه و آله كان يرفع بصره الى السماء في
صلوته، فلما نزلت الاية طأطأ رأسه و رمى ببصره الى الأرض.
It is narrated that the holy prophet --peace be upon him and his
household-- used to take his sights sometimes toward the skies while
at praying until this verse was revealed, then after he bent his neck
and kept his sights downward to the ground.
في تفسير على بن إبراهيم و قوله: «الَّذِينَ هُمْ فِي صَلاتِهِمْ
خاشِعُونَ» قال: غضبك بصرك في صلوتك و إقبالك عليها.
From Imam Sadiq --peace be upon him-- Ali ibn Ibrahim has quoted that
as Allah has stated "Those who humble themselves in their prayers" so
keep your sights downward ...
في مجمع البيان «هُمْ فِي صَلاتِهِمْ خاشِعُونَ» روى أن النبي صلى الله
عليه و آله راى رجلا يعبث بلحيته في صلوته فقال: اما انه لو خشع قلبه
It is quoted from the holy prophet --peace be upon him-- when he saw a
man playing with his beard while he was at Salat, that he said if his
heart was humble also his body limbs were certainly humble.
في كتاب الخصال عن أمير المؤمنين عليه السلام: ليخشع الرجل في صلوته فانه
من خشع قلبه لله عز و جل، خشعت جوارحه فلا يعبث بشيء...
From Imam Ali --peace be upon him-- it is quoted that he said one who
humbles his heart for Allah, his body limbs would also be humbled and
he would not play with a thing.
في أصول الكافي عدة من أصحابنا عن سهل بن زياد عن محمد بن الحسن ابن شمون
عن عبد الله بن عبد الرحمن عن مسمع بن عبد الملك عن أبي عبد الله عليه
السلام قال: قال رسول الله صلى الله عليه و آله: ما زاد خشوع الجسد على
ما في القلب فهو عندنا نفاق
In the book Usul Kafi it is quoted from Imam Sadiq --peace be upon
him-- that he narrated from the apostle of Allah --peace be upon him
and his household-- that he said if the humility of body exceeds the
humility of the heart that is hypocrisy in our view.
Source: تفسير نور الثقلين، ج3، ص: 528
So you see the whole story, no one would get blind, physically, for seeing the skies, but it is only discouraged (مکروه) in Shia Fiqh, and instead it is encouraged (مستحب) to look at your prostration position (موضع السجدة). Avoiding any discouraged deed and committing any encouraged deed of course would have some effects on the person, and in reverse committing any discouraged deed would have its own bad effects.