Afflicted by love’s madness all are blind.

[Scilicet insano nemo in amore videt.]

Propertius (50–16 BC) Roman elegiac poet [Sextus Propertius]

Elegies, Book 2, Elegy 14, l. 18ff (2.14.18) [ed. Harbottle (1906)]
    (Source)

(Source (Latin)). Other translations:

And surely no one sees when love his senses steals away.
[tr. Cranstoun (1875); 3.5]

To be sure, when mad with love no one can see.
[tr. Gantillon (1884); 3.5]

This is the truth of the adage "Madly in love, nobody uses his eyes."
[tr. Phillimore (1906)]

But men love-maddened one and all are blind.
[tr. Butler (Loeb) (1912)]

A man in love, as I am, stumbles blindly.
[tr. Carrier (1963)]

But who in love’s madness retains his sight?
[tr. Musker (1972)]

Of course no one uses his eyes when he is madly in love.
[tr. Goold (Loeb) (1990)]

In mad love no one can see straight.
[tr. Lee (1992)]

No one of course can see when crazed with love.
[tr. Kline (2001)]

In lover’s madness none can see.
[tr. Holcombe (2009)]

Unsourced variant: "No one in love can see."