Film is essentially a visual medium, remembering that the silent era paved the way for today's all-thud-and-spectacle cinema, which should mean that to go blind is, for any film-maker, the ultimate indignity. Diagnosed in late 1986 as HIV+, director Derek Jarman went public with the news almost immediately, much to the chagrin of the would-be moralists, and since has continued to turn out a regular stream of enormously varied films and books, from his mid-80s non-narrative period, to his more recent, highly-successful experiments in the striped cinematic form, like the appropriated classics of Edward II or the brightly coloured atmospheric economies of Wittgenstein. But with his illness finally slipping into its latter stages and his eye-sight succumbing to a gradual decline, comes almost certainly his final piece, Blue.

Blue is the colour of the void, of his blindness: "In the pandemonium of image, I present you with the universal Blue". And blue is the colour of the screen here - a vivid, deep, relentless blue for the entire 75 minutes. Against this Jarman constructs an elaborate soundtrack of voices, sounds and music to create a sophisticated patchwork in response to the state in which he finds himself; patchwork that spares us, the audience - his audience - nothing.

The writing is a summation of his work down the years - here is the anger and indignation of The Last of England, the harsh canvass, spewed with vitriol apropos the state of things; here is the resignation of the quieter passages of his exceptional books; here is the suffering and melancholy of his War Requiem; here is the great good humour of Derek Jarman the interviewee, the unrepentant subject of his autobiography, Dancing Ledge; here is the Everyman confused and grumpy at being ill; and here is the trangressive, elegiac maker of the masterpiece, The Garden.

Indeed, Blue is The Garden's first cousin, an encounter inside the mind of its creator, there an extraordinary collage of picture and noise colliding in a crie de coeur, a simultaneously obscure and enlightening journey to the heart of the man. Blue is shorn of image, replaced with reflective blankness, commentary provided by such Jarman regulars as Nigel Terry (who speaks for the director), Tilda Swinton, John Quentin, and memorably, the director himself: a blend of diary interludes - hospital visits, the numbing routine of pills that keep him alive - and the thoughts and poetry that narrate the slow acceptance of his own mortality. Music is provided by his usual composer, Simon Fisher Turner, and drop-ins from collaborators of old such as Coil (The Angelic Conversation) and Brian Eno (Jarman's first feature, Sebastiane).

Whether or not Blue is strictly cinema seems, in the final analysis, irrelevant. It has a meditative quality, a richness of personality that allows this to be both the most avant-garde and approachable feature of Jarman's career; a testament ultimately to the genuine truth and decency of one of the world's finest film-makers. "I caught myself looking at shoes in a shop window," he explains near the end. "I thought of going in there and buying a pair, but I stopped myself. The shoes I am wearing at the moment should be sufficient to walk me out of life." Exceptional.