They aren’t what most people think they are. Human eyes, touted as ethereal objects by poets and novelists throughout history, are nothing more than white spheres, somewhat larger than your average marble, covered by a leather-like tissue known as sclera and filled with nature’s facsimile of Jell-O. Your beloved’s eyes may pierce your heart, but in all likelihood they closely resemble the eyes of every other person on the planet. At least I hope they do, for otherwise he or she suffers from severe myopia (near-sightedness), hyperopia (far-sightedness), or worse.

Such uniformity is essential: for an eye to focus properly, its length and its optical system must be matched match to within a fraction of a millimeter. When a man and woman toss their genes together to make a baby, nature sets the focal point (determined by the optical power of the cornea and crystalline lens) at a standard distance, then adjusts the length of the eyeball to that same distance – twenty-four millimeters, or about one inch, with a few millimeters of variation thrown in for good measure. Thus unlike livers and kidneys and hearts and brains – those ordinary, non-spherical organs – eyes tend to an impressive sameness all over the world. My spleen may be half again bigger than yours, intestines can vary by five feet in length from person to person, but, with rare and usually disastrous exceptions, eyes are like so many peas in a pod.

Trust me. I’ve handled hundreds of eyeballs, removed from their owners for a variety of unpleasant reasons. One of my jobs – that of the ophthalmic pathologist – is to slice these globes into wafer-thin strips, stain the strips with vivid colors (hematoxylin and eosin, periodic acid schiff, Masson trichrome), then examine the results under a microscope. Given these credentials, I can assure you that your lover’s eyes differ from those of your most despised enemy in only the most superficial ways – in the color and texture of the iris and in the size of its pupil. When we wax eloquent about “beautiful eyes,” we are usually moved more by the trimmings – the lids, the lashes, the brows, the prominence of the globe in its orbit – than by anything contained within the eye itself. The Japanese sometimes refer to westerners as “big eyes,” an illusion caused by the lid position and orbital structure of Occidentals, while in truth Asians exhibit a collective tendency toward myopia that gives them on average slightly larger eyeballs.

A crisis came upon me during my fourth year of medical school. This was the crucial moment, the ultimate decision: to what specialty would I devote my life? Should I tend to phlegmy children who wriggle and scream and scratch my face when I thrust an otoscope into their ear? Should I slice open bellies, wander among livers and spleens and gallbladders, grope my way through greasy omental fat pads to explore coil after coil of diseased intestines? Or should I tend to the human heart, throbbing in its nest between foamy pink lungs?

I flirted with cardiology, then settled on neurology. Nothing rivals the complexity of the human brain, I reasoned, and no goal is more noble than curing its various ailments. The ultimate dialectic: using the skilled synapses of my own brain, I would diagnose and cure the diseased brains of others. Fortunately, before it was too late, a six-week elective in neurology revealed the terrible truth: almost every neurology patient suffers from a stroke or a seizure or an incurable brain tumor, and they almost never – NEVER – get better. Worse yet, the rare patient with a curable lesion is usually snatched up by the neurosurgeons, the most arrogant species on earth. By the end of the elective I felt like a zombie myself.

How about Ophthalmology? Clean, precise, offering its own dialectic: with my intact eye I would diagnose and cure the diseased eyes of others. It didn’t take long, only one good look into the ocular depths through a dilated pupil, and my quest was finished. There before me lay a stunning image – a delicate lacework of arteries and veins spread on a burnt umber palate swirled and streaked with shades of ocher. Most spectacular of all was the retina, a transparent wafer that gleamed like polished glass under the light of my ophthalmoscope. In the center the optic nerve shone like a risen sun. 

I was smitten.

Since every normal eye displays a clear cornea and a white scleral coat, any notion of special beauty attributed to the globe itself must derive from the iris, the dynamic membrane that contains the pupil and rests in front of the crystalline lens. The iris comes in many colors, but if one trusts the obsession of poets and novelists, the most beautiful irises are always blue: light-blue, velvety-blue, welkin-eyed, peacock, midnight, cobalt, ice-blue. Green gets an occasional nod – “she had jewel-bright emerald eyes, so lustrous and fetching they tore through my heart” – but most of the time blue runs the show. The rankest discrimination, and a bit ironic, since blue irises contain no intrinsic pigment, showing only the raw color of the tissue itself. The pigment cells in the Caucasian iris often add a twist to this aesthetic by lying dormant during gestation, breaking the heart of many a parent when the gorgeous blue eyes of their newborn turn muddy-brown as the months go by.

The texture of the iris is all but invisible to the unaided eye, but the ophthalmologist’s slit-lamp microscope discloses a panorama of diaphanous spokes, crypts and valleys, flecks and spots and strands that dance about with each twitch of the pupil. Dark irises tend toward a tight weave, while light irises fluff up like a shag rug. And there’s the all-important pupil: constricted by morphine and bright light, dilated by fear, darkness, sexual arousal, and death. Yes, the coroner’s final measure, the mark of a departed soul – enormous black pupils that give nary a twitch to even the brightest light. Despite this morbid sign, many cultures consider large pupils a sign of beauty. “Belladonna,” Spanish for “beautiful lady,” is also the name of a pupil-dilating poison extracted from the plant Atropa belladonna, more commonly known as deadly nightshade.

A note on cosmetics: under an ophthalmologist’s slit-lamp microscope, false lashes look like mutilated telephone poles, while mascara shows up as greasy black chunks that squiggle across the corneal tear film with every blink. For the efficiency-minded woman there is permanent eyeliner, a dark line tattooed along the lid margin. It works beautifully, provided styles don’t change, and provided the tattooist, working millimeters from the cornea, doesn’t inject ink into the eyeball.

About myopia – if you have it, be happy. Numerous scientific studies have shown that near-sighted men and women boast a higher average intelligence than their non-myopic cohorts. The precise mechanism of this association remains unknown, but there are two popular theories: nature and nurture. Those who support nature argue that during embryologic development, the eyes develop from the same neural tube as the brain itself. Since large eyes tend to be myopic, big eyes and big brains might go together in much the same fashion as long arms and long legs.

Those who favor nurture insist that myopia leads to high intelligence because of its effect on childhood development. Most near-sighted kids wander around undiagnosed for years, and during this formative period – unable to see the baseballs, Frisbees, and rocks thrown at them by their playmates – they spend a lot of time indoors. The non-athletic myopes who take up reading get high scores on their SATs, while those who take up eating give us claustrophobia by overflowing the seat next to us on airplanes. Myopia also exerts a powerful influence on career choice: eighty-five percent of my fellow ophthalmologists are myopic, an incidence far greater than that of the normal population. Pathology breeds preoccupation.

However beautiful the human eye, it serves a more important purpose than romantic allure. Forty percent of the brain is devoted to vision, which provides us with more information than our other four senses combined. Our optic nerves transmit millions of impulses to the brain every second, impulses that specify the location, color, and intensity of light for all the points in our visual space. Even more remarkable, our visual cortex fuses the slightly disparate images from each eye to give us the three-dimensional miracle known as depth perception. A stunning feat, given that video cameras, arguably the benchmark of modern technology, can muster only two dimensions.

Certain ocular tissues stand on the pinnacle of evolution. How does nature, so crude in claw and fang, create a surface that brings light to a pin-point focus? This surface must be perfectly curved, perfectly transparent, perfectly smooth. It must be – water! Which is to say, the cornea owes its optical precision to a tear film whose dissolved salts, lipids and proteins allow it to maintain a flawless wetted surface. A man who has no tears stands on the threshold of blindness. Worse yet, that man will writhe in agony: a bone-dry cornea responds to each blink with a tormenting jolt of pain, a jolt so severe its sufferers compare it to rubbing shards of glass on the eye.

Another evolutionary triumph: for light to reach the retina unimpeded, the cornea and lens must remain

 transparent, and yet, like all living tissues, they must be nourished by oxygen. More than 99.9 percent of all human cells obtain their oxygen from capillary blood flow, but capillaries lacing through the cornea and lens would veil our vision with an opaque net. To remain crystal clear, the outer portion of the cornea must survive on oxygen absorbed from the surrounding air, while the lens and the inner cornea depend on. aqueous, a colorless fluid that flows through the chambers of the eye. Since aqueous contains neither hemoglobin nor cells of any sort, it carries only a tiny fraction of the oxygen contained in blood. And the rate of aqueous flow must be precisely controlled: a deficiency shrivels the eye into a useless spitball, while glaucoma, caused by blockage of the trabecular drainage channels near the base of the iris, leads to throbbing pain and blindness. Thus pain-free vision, the presumed birthright of every human, demands an arrangement as delicate and wondrous as that achieved by any space-age gadget.

Of all the ugly things in this world, I would argue that diseases top the list: cancer, syphilis, leprosy, gangrene, fungating ulcers. Even the pictures lying flat and odorless on the pages of a textbook bring a surge of nausea. And let us not forget elephantiasis, an infestation by filarial worms that wriggle through the lymphatic system, causing such severe edema the legs often swell to the size of tree trunks. Male victims pay a special price, with the unluckiest among them pushing their scrotum before them in a wheelbarrow.

But surely the eye, the most delicate of organs, is afflicted by only the subtlest diseases. Or so one might think. I soon discovered the fallacy of this logic. Indeed, some of the most grotesque diseases known to medicine are those that disfigure the eye. Ophthalmology did not prove the sanitary refuge I had hoped for. On the second day of my student elective in the Stanford Eye Clinic, I examined Justine Jewell, a tall, slender diabetic in her late teens. She was accompanied by a tall mother who carried twice her daughter’s bulk. Justine complained, “My eyes are full of floaters.” Good, I thought. Floaters. No problem. Everything looked fine from the outside – white sclera, clear corneas, pale blue irises. Then I shined my ophthalmoscope through her dilated pupils. “Excuse me” I said, and stepped out of the room.

By that time in my career, I had seen the interior of a few dozen eyes, each a breath-taking panorama of amber and brown, yellow and pink, shading through a delicate lacework of arteries and veins. But Justine’s eyes were filled with tangles of angry red spiders. Dark clots rose into the vitreous gel, trailing streamers of blood in all directions. I rushed into the hall to grab Doug Jacobson, the retinal specialist in clinic that morning. It took only an instant. Doug focused the beam of his ophthalmoscope on Justine’s right eye, then her left, removed the ophthalmoscope from his head and hung it on the wall.

“You have diabetic retinopathy,” he said. “And I’m sorry to say it’s very advanced.”

The mother burst into tears. “Oh, doctor,” she sobbed, “my grandmother, my cousin Ernest, this woman across the street – so many people I know went blind from diabetes! Can’t you do something?” 

Justine said nothing. Her eyes were dry, wide open, the irises stretched into pale blue rims around the blackness of her dilated pupils. Later, in private, Jacobson gave me her diagnosis in the vernacular – jungle-osis. Jungle-osis meant dense black clots, arching streamers of blood, a traction retinal detachment bound with scars so dense they defy the reparative efforts of even the most skillful surgeon. It meant blindness, both eyes, and soon – weeks, perhaps a month or two. Justine, not yet twenty years of age, was doomed to stumble through the remaining decades of her life with a white cane or a guide dog. Worse yet, she might develop absolute glaucoma, an intractable rise in pressure so painful and nauseating the victims often beg to have their eyes removed.

But – perhaps not. Justine’s only hope was a treatment so recently developed we had no proof that it worked, a treatment whose promise was based on the crudest evidence. For decades, ophthalmologists had noted a strange phenomenon: when one eye of a diabetic showed widespread retinal scars from an old injury or infection, that eye often retained vision long after diabetic hemorrhages had blinded the unscarred eye. Apparently, by a mechanism no one understood at the time, these scars protected the surviving retinal tissue from the ravages of diabetes. And so, by a logic that might impress a blacksmith or a witchdoctor, the new treatment called for obliterating much of the nonessential peripheral retina in an effort to save the central portion that gives us our sharpest vision. Since there was no other option, Jacobson advised Justine – a young girl poised on the brink of blindness, dry-eyed and speechless with fear – to let us experiment on her.

Just months before Justine’s arrival, our clinic had acquired the Coherent Radiation Model 800, one of the first lasers used to treat the human eye. Its console, six feet long and three feet high, looked like a coffin on legs. A glass tube buried deep within its circuitry gave off a high-pitched whine and emitted an eerie, bluish-green beam of light. Shown against a wall, the beam formed a circle of shimmering motes that scurried about like atoms in a nuclear furnace. A fabulous instrument, more precise than any razor, but now its tightly focused beam would serve a crude purpose – destroying retinal tissue. By the dozens, by the hundreds, the laser emitted tiny flashes, each flash the space-age equivalent of a magnifying lens burning a hole in a leaf. When the treatment was complete, lifeless white scars obliterated more than half of the patient’s peripheral retina. Care was taken to avoid the vital central portion, assuring that, if the treatment proved successful, the patient would maintain the acute vision needed to read and drive a car.

Justine suffered. To dull the pain from those hundreds of burns, we injected Xylocaine deep behind the eye. The contact lens used to deliver the laser beam sometimes caused a painful corneal abrasion. For three or four days after every treatment, fluid leaking from the peripheral burns seeped into the central retina, blurring and distorting her vision. Justine’s mother was always there, wringing her hands and squeezing her eyes shut when her daughter moaned under our long needle. But after six treatments the vitreous hemorrhages began to clear. The tangle of spiders melted away. Nine months after Justine’s first visit, Jacobson announced, “That’s it. All the hemorrhage is gone.”

Justine’s mother burst into tears, dropped her purse on the floor and threw her arms around Jacobson. His face blushed fiery red as he struggled against her grip, muttering, “No, no, it’s too soon to tell for sure,” but he was a small man, an inch or two shorter and many pounds lighter than the joyful mother.

Four years later, during the last months of my residency, Justine’s vision was still 20/20 in both eyes. There was no trace of hemorrhage, nor of the spidery vessels that signal recurrent proliferative retinopathy. Over the next three decades, recoveries like Justine’s would number in the thousands as laser surgery became the gold standard for treating diabetic retinopathy. A study published in 1976 showed a four-fold reduction in severe visual loss, but modifications to the original method eventually reduced total blindness among diabetics to a tiny fraction of the original incidence. By the turn of this century, numerous charities had delivered improved versions of the Coherent Model 800 to developing nations across the globe, allowing hundreds of thousands of patients to enjoy its benefits. Unfortunately, there remains a dark side to this story: many diabetics slip through the system, seeking care only when rampant scars have obliterated all hope of treatment, while some patients suffer an attack of retinopathy so fulminant and destructive, even the most timely therapy cannot sustain the acuity needed to drive or read.

Despite these limitations, laser surgery for proliferative retinopathy has proved a medical triumph of the first order. Here is something crude in principle, simple to perform and easily learned, but it works. In the miracle that defeated jungle-osis, my role – treating thousands of patients with the laser, plus teaching the procedure to almost a hundred residents – has been the greatest privilege of my career.

Even with laser surgery and a host of other high-tech developments, the blind are still with us. If we live long enough, our eyes will always fail us. Most ten-year-olds can count the legs on an ant, while only the rare nonagenarian can see the ant itself. Sooner or later our eyes, along with our knees and our hearts and our hair, will surrender to the vile duo of father time and ,mother nature. During the early years of life, the sclera is snowy white, the ocular media – composed of the cornea and lens and vitreous gel – remain crystal clear, while the retina shimmers like beaten silver under the light of an ophthalmoscope. Indeed, the sparkle we see in children’s eyes is no illusion. But by our twenties, the shank of young adulthood, the luster has begun to fade, foreshadowing the greenish cataract and rheumy yellow sclera of senescence.

Old age’s first target is often our crystalline lens, a lentil-shaped tissue that hangs behind the iris, suspended by a thousand translucent filaments. Tension on these filaments allows youngsters to focus their eyes from near to far with the ease and precision of a Nikon camera, but in order to sustain its marvelous clarity, the lens must survive without capillaries, nourished only by oxygen-poor aqueous fluid. Such metabolic tenuousness leaves the lens in a constant state of near suffocation, vulnerable to every biological assault. Like the canary in the mine, it is often the first tissue to fall victim when our bodies are attacked by radiation, toxins, or aging. During our fifth decade, our lenses begin to lose the elasticity that allows them to alter their focus from distance to near, bringing the curse of bifocals or reading glasses. Then, inexorable as an unloved season, cataracts appear, diffracting light into haloes, casting an odd tint on familiar objects, eventually drawing a dark veil over our world.

If granddaddy lives long enough, he won’t be able to read, but if he’s lucky – if cataracts are the only cause of his impairment – twenty minutes at the hands of a skilled surgeon, and the opaque lump is gone, sucked out through a vibrating needle and replaced by an acrylic lens the size of a cornflake. The next morning granddaddy will pour over his morning newspaper as happily as he did in his twenties.

“It’s macular degeneration, isn’t it, doctor?”

“Yes, I’m afraid so.”

To see clearly, we need more than a clear cornea and a clear lens. Much more: a retina to transform light into nervous impulses, an optic nerve to transmit these impulses to the brain, and a visual cortex to process the impulses. Arguably the most complex link in this chain is the retina, a delicate, multi-layered, altogether wondrous membrane. But alas, the retina harbors a fatal flaw: like the lens, it falls victim to the ravages of time. As we live beyond our fifth decade, an ever-increasing proportion of us will suffer degeneration of the macula, the central portion of the retina and the site of its most active, densely-packed neurons. First comes loss of the silvery sheen that adorns the retina of the young; then, as more years pass, there begins a descent into the ragged, lusterless wasteland known as “dry” macular degeneration – an insidious progress akin to the wrinkles and liver spots that transform a baby’s face into the face of a crone. Year by year, line by line on the acuity chart, victims lose their vision. Worse yet, over time the dreaded disease expands its roster of victims until, among the few that reach the century mark, virtually none are spared its devastation.

“Doctor, when I got up this morning there was a black spot in my right eye. It blocks out everything I look at.”

This was Sister Maria, an eighty-four-year-old nun. I have heard similar words from a sixty-nine-year-old railroad engineer and an eighty-six-year-old former prizefighter with a crooked nose. 

A colleague of mine, a seventy-three-year-old professor of pathology at the University of Louisville School of Medicine, spoke more bluntly. One afternoon he got up from his microscope, walked across Muhammad Ali Boulevard and barged into my clinic at the Department of Ophthalmology and Visual Sciences. “God dammit, Gamel,” he said, “what the hell’s going on with my right eye?”

As I suspected the moment I heard their complaints, these were the unlucky ones. Most patients with macular degeneration suffer the “dry” form, which steals vision slowly, but a small percent suffer an abrupt hemorrhage or leakage beneath the retina that marks the onset of the “wet” form. From that point on, every object they look at disappears into a black hole. Fate makes only one concession: though the blind spot tends to enlarge over time, and though it quickly destroys the ability to read or drive, it rarely obliterates all sight, allowing the majority of sufferers to navigate a familiar environment.

“Doctor . . . please . . . tell me . . . is there a treatment?”

Dry-eyed or weeping, motionless or wringing their hands, clear-voiced or choked with fear, sooner or later every patient with macular degeneration will ask the same question. Theory offers two potential cures: transplanting the eye, or replacing the retina and its supporting structures. For the moment, both procedures remain well beyond the reach of science. The complexity of the retina rivals that of the brain itself. To transplant either organ, the surgeon must reconnect millions of axons – microscopic neural tubes so fragile the subtlest trauma destroys them forever. I suspect this achievement will elude the best surgeons for generations to come.

At the moment we can boast paltry progress against macular degeneration. For patients with the “dry” form, the only proven remedy is a regimen of vitamins and antioxidants that delays – but does not stop – the insidious loss of vision. On a more positive note, recent advances in molecular biology have given us a panoply of new drugs for treating “wet” macular degeneration. Though vastly more effective than the therapies available earlier in my career, these miracle molecules remain an imperfect cure: they must be injected repeatedly into the eye, they improve vision in only a small proportion of patients, and of these only a lucky few sustain the improvement for the remainder of their lives. Despite the triumphs of modern medicine, decay is written into our genes. It is our destiny.

Boris Osterhaus was a gray-haired farmer from Cecelia, Kentucky. His pot belly stretched the bib of his denim overalls tight as a drum. Minutes after arriving in my office, he pulled a pouch of Red Man Chewing Tobacco from the pocket of his denim shirt, then, remembering that this was neither the time nor the place to tuck a wad into his cheek, grimaced and stuffed the pouch back in his pocket. An optometrist in Cecelia had referred him to an ophthalmologist in Elizabethtown, the ophthalmologist had referred him to me, and now, after a hundred miles over back-country roads, Boris learned from my lips that he would never read or drive again. A dry, pock-marked wilderness had destroyed the macula in both of his eyes. When I finished my dismal spiel – a diplomatic version of “Mother Nature is a bitch, Father Time is a son of a bitch, and there’s not a damn thing we can do about it” – Boris leapt out of his chair to grip me in a knuckle-cracking handshake.

“Thank you, doctor, thank you so much. I just can’t tell you how good it is to finally hear the truth straight up and down. Now I can get that confounded woman” – he gestured toward the stern-faced daughter who had brought him – “to stop dragging me all over the county. She keeps saying nowadays you doctors can fix anything. What a load of rubbish! I’ve lived eighty-three hard-bit years, and ain’t nobody in my family been able to read much after they was seventy-five or eighty. That’s just the way it is. I knowed it all along, but she wouldn’t listen.”

Of all my patients with macular degeneration, Hans Bergerman proved the most astute observer. No surprise, given his curriculum vitae: professor emeritus, former chairman of Stanford’s department of anthropology, editor of five books, author of two hundred academic publications. His bushy brows and bald, sun-darkened head gave him a gnomish look. Born in Brazil of German parents, he spoke with a crisp accent and sat stiff as a soldier in the exam chair. He never took his eyes off me for a moment.

“Let’s see how this matches yours,” he said, handing me a sketched outline of the blind spot he had noted in his right eye. I had just finished my exam and was drawing my own picture of the lesion that lurked beneath the macula of that eye. Both drawings resembled a childish doodle of a wolf’s head, but in my doodle the snout and ears were drawn with a red pencil to show streaks of sub-retinal blood. The wolf’s bulbous jowl was formed by a tangle of pathologic vessels that threatened to hemorrhage at any moment, destroying forever Bergerman’s central vision. The diagnosis was crystal clear – “wet” macular degeneration. Several years before, the same disease had destroyed the central vision in his left eye.

Bergerman was lucky. Wet macular degeneration usually strikes in the central portion of the retina, where laser therapy, the only option available at that time, would cause instant blindness. When I saw that his lesion lay a fraction of a millimeter removed from the center, I felt a shiver of anxiety. I had to treat the poor man by cauterizing the tangle of vessels with a laser beam, even though the zone that divided success from disaster was no greater than the width of a few human hairs. Doug Jacobs, the faculty attending who watched my every move through the viewing tube on the slit-lamp microscope, will never know the sweat that dripped from my armpits as I fired dozens of blue-green flashes into Bergerman’s eye.

Three months later, Bergerman said, “Thank you, Doctor.” His vision was 20/30. The tangle of vessels had shrunk to a dry, flat scar. He thanked me again two years later, the day he awoke to find a huge black spot in the center of his vision. My treatment had failed. I knew it would fail – unless the patient died first, treatment of macular degeneration always failed – but the sight of that dark clot beneath his retina brought me to the verge of tears.

“Thank you very much,” he said. “You allowed me to read for an extra two years.” On his way out of the exam room, he stopped to shake my hand and give my shoulder a friendly squeeze. With a rueful smile he said, “You sound so sad doctor, like you just lost your best friend. Who do you think you are – a magician, a god who makes old men young forever?”

Patients are more than the sum of their failing parts. The wisest among them know that life cannot be cured, but even they need someone to inform them, and – when healing fails – to accompany them on the lonely road to blindness and death. I did not learn this truth in a book or a laboratory or a lecture hall. My patients taught it to me. They came in desperation, returned year after year to share their struggles, and, as the years passed, they died. One way or the other I always lost the battle, but they gave me many precious moments.

The eye begins as a perfect thing, a miraculous organ, but its luster, mortal and doomed as life itself, fades with each passing year. I watched it all through my slit-lamp microscope. I watched my patients grow old with grace, and slowly, decade by decade, they taught me how to do it.