Proto-Indo-European Roots

Root/Stem: *kaiko-
Meanings:  blind
Italic Latin caecus 'blind'
Celtic Old Irish caech 'one-eyed', Welsh coeg 'empty', Old Cornish cuic
Indic Sanskrit kekara- 'squint-eyed'
Germanic Gothic haihs 'blind'
Notes: This root could be regarded as the so-called "European" word, unless the Old Indic word which proves the Common Indo-European origin of the root. 
In fact, the diphthong *ai was rather rare in Indo-European, as well as the very sound *a. There can be maybe 10 or 15 roots which contain this diphthong found among the Proto-Indo-European corpus. Were they loanwords from some other language?