The number five suits Greg Hewett’s fifth book, Blindsight. The book has five sections. Its first poem is in five stanzas, and its final stanza is composed of five words. The fives that orbit the book belie its larger numerical conceit: each line has a prime number of syllables, each stanza a prime number of lines, each poem a prime number of stanzas, each section a prime number of poems, and the collection itself a prime number of sections (although there is one poem that is an exception to the stanza rule). Additionally, the publication of Blindsight makes Hewett a poet with a prime number of books.

Numerical organization is one way of seeing in these poems, which tessellate around questions of sight, and consider the visible, the visual, the unseen, and the remembered. Not seeing, in these poems, is a condition of mechanical failure (blindness), but it’s also a failure of rigor, of not looking closely enough. Not seeing can also be a condition of patchy memory, in Blindsight, or one of inadequate specificity: landscapes of endless trees, or suburbs or highways that are hard to distinguish.

The title of the book’s first section, “Number Blind,” refers to dyscalculia, a condition that makes it difficult or impossible for those who have it to absorb or communicate numerical information. In addition to having trouble with basic math, dyscalculics find it difficult to interpret numbers in visual forms (numbers on a clock, for instance) and, additionally, to remember spatial or directional data, such as countries on a map.

Number blindness opens the poems to their larger interest in missing or unavailable information. In “Memoir,” “On the days the fog lifts, / it isn’t any clearer.” In “Prime Time,” “TV sets flickered on as the sun went off the air.” The poems offer a catalogue of what compromises clarity, and of the kinds of clarity that are selectively present, even as they’re fogged or marred by light or time or the decay of bodies or suburbs or how weird the television shows of the 1970s look in 2016.

Often these poems turn back to a boyhood and the beguiling negative space of memory. “Witness” opens “There’s a car crash in my head / from when I was just a kid.” “Because I Could Not” opens “In elementary school I beat you up just because.” These memories rhyme, in other poems, with concerns about what happens to boys. Blindsight’s strong link between being a boy and being a poet echoes George Oppen’s “Boy’s Room,” whose speaker notes, on seeing the childhood rooms of Keats and Shelley, “And indeed a poet’s room / Is a boy’s room.” Blindsight is oriented toward the boy the speaker was, and toward the disorientation of being that boy still.

The blur of memory finds its companion in Hewett’s treatment of the physical loss of sight. The book’s first poem, “Approaching Blindness,” opens “When I go out, I wear black / glasses to protect my eyes.” Hewett’s speaker finds solace in placing himself in a constellation of other poets who were born into or arrived at blindness. The book’s title poem riffs on both Milton and Homer, and opens “Never considering how his light is spent, / the mountaineer tastes the height and sheer of cliff.” Poems that deal with the loss of sight resist the compulsion to read it as a diminishment, instead of as a change that offers other strengthened abilities in its stead.

These poems are beguiled by what’s iterable and what isn’t. Dead people aren’t coming back. Rooms that used to exist won’t reappear or smell the same again. “Grandmother’s House” opens, “I want to write about my grandmother’s house, though this is not my / grandmother’s house.” There’s an earnest urgency, in the poems, to record before too much light pollution cancels out all of the stars, before small children get bigger, before film stars are longer dead, before old porn stops being appealing.

Blindsight’s foci, personal and literary, filmic and artistic, represent a range of far and more recent pasts. These poems are interested in the contemporary moment so much as it is the site of their reflections. Yet these poems firmly resist nostalgia. Their speaker is caught between the desire to make a record and the insistence that all records fail, and that their failure, the gaps of what’s unseen or unseeable, is interesting and necessary. Plus, amid what isn’t iterable are those things that can’t help but repeat and come back. “Echo” ends, “But when I open my eyes, / everything becomes echo / of words within words.”