A spelunker friend of mine once led me into a cave that dropped off precipitously into a world beyond daylight and vegetation, a world cold, damp and mineral. Hours later, when we returned to the mouth of the cave, I noticed a sweet smell -- the smell of foliage that is always in the air in the country, but that I seldom notice. Being so long in the dark cave similarly charged my vision. For what seemed the first time, I saw how blue the sky can be, and how green the trees -- how bright our world is.

Andrew Potok's "Ordinary Daylight" made me think back to that day when daylight had never seemed less ordinary. That is one of this book's important effects, to show the phrase "ordinary daylight" to be an oxymoron.

The blind always teach us to value sight, by forcing us to imagine the lack of it, but Potok, who is now in his late 40s, is an especially good teacher. As a painter, he was trained to see better than the rest of us do. Then when he began to lose his vision to an inherited eye disease called retinitis pigmentosa (a cruelly apt-sounding affliction for a painter), he put his artist's sensibility, as well as his artist's eye, to the task of recording the physical and psychological effects of growing blindness.

But the medium was no longer pigment and canvas; it was words. Not only did he have to learn the skills the blind must master if they are to function among us -- to use a cane, to read Braille -- he had to learn to write. Think of the difficulties: "As I type, my words disappear into an inaccessible sea of paper, retrieved for me days or weeks later by readers who fill tape after tape with my awkward prose, awaiting revision. If I don't need the flow, the uninterrupted sense of a taped passage, I can still put my typescrpt under the zoom lens of my closed-circuit TV system and read it with my own eyes slowly, letter by magnified letter, each 1 1/2 inches tall."

Yet the prose that has grown from that process does not seem labored; it is nimble, at times even elegant. It is alive with carefully observed detail. Here is Potok describing the full extent to which he is able to see: "If one imagines full sight as a masaic of millions of visual units, the vision remaining to me is determined by a small number of functioning cells unevenly distributed over the whole. I see through a small, irregular doughnut-shaped area with a little help from two motion-perceiving crescents somewhere near the edges. The central losses eliminate all clarity, and the peripheral ones limit my orientation in space. In the full mosaic of cells, the dysfunctional ones are not black, nor are there sharp boundaries between them and the neighboring useful cells. Blindness isn't blackness; it is nothingness. I have, therefore, on my retina, a tiny amount of somethingness surrounded and influenced by a vast nothingness."

Even though this book's excellence is proof as we read it that Potok's story has a happy ending, it is nonetheless a painful story. When we first see Potok, he has already learned to "cope" with his blindness -- that is, to resign himself to it in visible ways, by learning the necessary skills and by getting a job as a counselor to others who have the disease: "I was carving out a unique place for myself in the blind world . . . . I was becoming a kind of half amateur (necessary to be taken somewhat seriously by colleagues and clients alike), friend and counselor to people who were themselves in some stage of nonacceptance of our shared blight, retinitis pigmentosa."

But an important, psychological ways he has not accepted the disease any better than the people he is counseling. Along comes news of a miracle cure -- bee stings -- for an affliction science says is incurable, and off Potok goes on almost the next plane to England, where a mysterious woman was claiming that the venom of her special bees was clearing the vision of people with retinitis pigmentosa. Accompanied by his skeptical wife, Charlotte, he leaves behind their farm in Vermont, their children and his counseling group, whose members understand his need to grasp at any possibility of regaining his sight.

Our hopes are with him too, but long before he learns that the cure does not work, we realize he is the victim of a charlatan. I was irritated at him for being so blind -- figuratively -- until I realized that his continued submission to dozens of painful bee stings, day after day for months, represents the depth of his reluctance to be literally blind. Still, it is excruciating to witness: The back of his neck swells where the bees are applied, and he has headaches; his moods vary from exhilaration at times when he thinks he sees better to pitched depressions when he realizes that his sight has not improved; Charlotte returns to the farm, and to her life as a potter, and he is alone in London. Finally, and most terribly, his hope drains away, and he himself returns, bitter and humiliated that he has allowed himself to believe in magic.

Just at the moments in his narrative when I felt that I could bear no more, Potok doubles back, filling us in on significant events in his past, and always making connections, as anyone who tries to understand his experience must, between the past and the present. When he first talks to Helga Barnes, the woman who claims she can cure him, he finds her voice "penetrating and seductive, the voice of a woman, a European woman -- my mother? -- who would touch me, change me, make everything right again." He describes the flight of his family from Poland, where his mother was a successful and wealthy furrier. Uprooted by Hitler, she was transplanted in New York and before long flourished again. This is a connection that Potok does not make -- that his family's ability to start anew parallels his own situation.

At the end of this book, there are signs that Potok will flourish, too. He has proven himself in his new medium. I hope he can find another story as compelling as his own to tell.