sudden deep redness may be due to sub conjunctival hemorrhage, it will get dissolved itself in three weeks, as precautionary measure you can use Tobrex eye drops 4-5 times.
Hello
It is very difficult to comment without examining you
It could be due to many causes like sub conjunctival hemorrhage,dryness etc
Kindly share photos of your eyes so that I may guide you better
Regards
Disclaimer : The content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding your medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.