Videt intus edentem
vipereas carnes, vitiorum alimenta suorum,
770Invidiam, visaque oculos avertit. At illa
surgit humo pigre semesarumque relinquit
corpora serpentum passuque incedit inerti;
utque deam vidit formaque armisque decoram,
ingemuit vultumque ima ad suspiria duxit.
775Pallor in ore sedet, macies in corpore toto,
nusquam recta acies, livent rubigine dentes,
pectora felle virent, lingua est suffusa veneno.
Risus abest, nisi quem visi movere dolores.
Nec fruitur somno, vigilacibus excita curis,
780sed videt ingratos intabescitque videndo
successus hominum, carpitque et carpitur una,
suppliciumque suum est.
Envy could be seen, eating vipers’ meat that fed her venom, and at the sight the goddess averted her eyes. But the other got up slowly from the ground, leaving the half-eaten snake flesh, and came forward with sluggish steps. When she saw the goddess dressed in her armour and her beauty, she moaned and frowned as she sighed. Pallor spreads over her face, and all her body shrivels.
Her sight is skewed, her teeth are livid with decay, her breast is green with bile, and her tongue is suffused with venom. She only smiles at the sight of suffering. She never sleeps, excited by watchful cares. She finds men’s successes disagreeable, and pines away at the sight. She gnaws and being gnawed is also her own punishment.
Note how this passage from Metamorphoses 2 is constructed out of words for seeing (videt), sight (visa), eyes (oculos), and culiminates in a vision of Envy wasting away through seeing (videndo).
Then further consider that Envy is Invidia, i.e., a "looking into" - the first words are in fact videt intus - and we begin to see how the narrative is acting out an act of looking, or not looking (oculos avertit), at a creature who, instead of being fed by the joy of the eye, is consumed by the act of looking. Unlike Aglauros who looked into the casket of Erichthonius, Athena averts her eyes from this snaky creature (recall, the goddess's shield bears the head of Medusa - another being who could not be looked at head-on).
This scene of Athena at the house of Envy, with its psychological "insight," is clearly one of the set pieces that led to a host of medieval and Renaissance imitators -- one thinks of allegories even up to Spenser's Fairie Queen as Ovidian. It also led to the commonplace that Ovid (and other classical works) contained, as the great art historian Émile Mâle put it, "a dim sort of revelation" (see a bit more from Mâle here).
And here is Giotto's vision of Invidia from the Scrovegni Chapel, complete with consuming serpent consumed, fire and moneybag: