This poem by Rossetti is one that is written in praise of the beauty of the speaker's beloved and the importance of his sight in seeing his beloved. It is this sight and the love that accompanies it that gives the poem its title. The act of seeing is crucial to the love that the speaker has for his beloved. Consider how this is expressed through the series of rhetorical questions that begin the poem:
When in the light the spirits of mine eyes
Before thy face, their altar, solemnize
The worship of that Love through thee made known?
This quote compares the eyes of the speaker to faithful religious adherents presenting worship before the altar of their God (which metaphorically is how the face of the speaker's beloved is described). So important to the speaker is this act of seeing his beloved that were he not able to see her eyes any more, life would become a barren, stale and infertile place, robbed of any beauty or joy. All that would be left to the speaker would be, as the final line of the poem describes it, "The wind of death's imperishable wing." The act of seeing conveys the love the speaker has for his beloved, and the importance of seeing her is captured in the way that life would be intolerable without her, and his joy and ecstasy would be exchanged for bitterness and life without hope. "Lovesight" therefore captures both the emotions of the speaker but also the transforming nature his act of homage has on the world and his attitude towards it.