WANTED: Students with desire to help humanity. Could earn up to $40,000 or more in a health profession seeking newcomers.

The field: Optometry.

The catch: Four more years of rigorous -- and expensive -- schooling after you've picked up a bachelor's degree. Probably a hefty debt once you've graduated.

Optometry, say practitioners, is an occupation often overlooked by students seeking a career in medicine, but the need is there -- especially for blacks and Hispanics willing to work in urban areas.

"Considering that high technology requires better vision than ever before; that the elderly population is increasing; that public recognition of the need for preventive eye care is increasing -- and that the average practicing optometrist is over 50 -- the opportunities for graduating optometrists are clearly apparent," says John T. Crozier, dean of student affairs for Pennsylvania College of Optometry in Philadelphia.

"For those who wish to serve in minority communities, the need is even greater."

"There's plenty of opportunity," agrees Charles Comer, who heads the minority recruitment project of the black-formed National Optometric Association. The association takes major credit for increasing the number of black optometrists in this country from about 100 a decade ago to 200 now out of a total of 22,000 U.S. practitioners.

The association also actively recruits Hispanics -- of which there are about 200 currently practicing -- and American Indians.

"We go to schools and make presentations, then invite the classes to come in and see our work," says Dr. John Howlette of Richmond, Va., an association founder. In these visits, "We're seen as role models. A lot of kids who go into the field see a black optometrist for the first time." Recruiters serve as counselors throughout the student's education.

In 1951 when Howlette set up practice, "I was the second black optometrist in the state. Now there are five in Richmond and 9 or 10 in the state -- which I like to attribute to my recruiting efforts."

That he is effective can be seen in the roster of family members he has signed up: His son, son-in-law, brother and niece's husband.

Chicago optometrist Robert L. Johnson, current association president, would like to see more enrollment of inner-city students willing to return to their neighborhoods, where many residents may not have access to quality eye care. "The greatest need we have is in urban areas."

Inner-city patients have to be taught "what a complete eye exam should entail," says Johnson's associate, Hattie Stewart, of Plano-Child Development Center and Optometric Associates of Chicago. Sometimes, she says, "Operators who think more about their level of profit take advantage of lower-income people. They slap glasses on their face and say, 'Go forth and see,' " failing to check for "other problems.

"If a patient doesn't know what to expect, it's easy to not give them as much. Kids in public housing are wearing glasses and still have vision problems."

Adds Howlette: "To give good primary vision care in the ghetto is appreciated."

Comer estimates that a minority graduate going into private practice might earn $35,000 to $37,000 or more a year, once he or she is established, though the cost of starting up -- as much as $40,000 -- may be prohibitive for some. "But many of them do it, and they make it."

Other opportunities are in offices with established optometrists ("Many inner-city practices are going begging") or in government health services, where salaries may begin at the $21,000 to $25,000 level.

"We have a successful minority optometrist talk to students to tell them that this is a viable profession," says Comer, "that they can make a decent income and be of help."

What concerns the profession is that while the need for its services grows, the number of students entering the nation's 16 schools or colleges has increased only slightly in recent years to about 1,150 annually. (In 1980, 60 were black, 72 Hispanic and 6 Indian.)

One problem they see is that many people confuse their profession with two others in the vision field:

Optometrists -- doctors of optometry -- examine eyes for vision problems and write prescriptions for glasses and contact lenses.

Ophthalmologists are medical doctors with additional training to treat diseases of the eye.

Opticians make the glasses from the prescription.

Another problem is the cost of getting a degree. At Pennsylvania College of Optometry, for example, yearly tuition currently is $8,870. Beyond that, explains Lawrence H. McClure, assistant dean of student affairs, the costs include $1,500 to $1,600 for books and instruments for a first-year student and $5,000 a year for living expenses.

To pay their bills, most students take out a loan from one or more of several federally funded programs available through the optometry school, at a current interest rate of up to 9 percent. With the Reagan Administration budget cuts, "Students are having to assume a larger burden of their education costs."

Some grants are offered, particularly to students with "exceptional" financial needs. And many states without local optometry schools have contracts with schools outside the state to pay a portion of the tuition for a certain number of their students. Virginia and Maryland, but not the District of Columbia, are among the contracting states.

Often students find they have to work parttime, says Comer, but this sharply reduces study time. Howlette, 54, says that along with the GI Bill, "I drove a streetcar in Chicago at night from 5 p.m. to 3 a.m. and went to school from 8 to 4." (The large number of GI Bill-educated optometrists heading for retirement in the next decade is seen as widening career opportunities for today's students.)

Through a combination of loans, grants and work, however, once accepted into a school, students usually can expect to get the funds to complete their education, says Lee W. Smith, executive direction of the Association of Schools and Colleges of Optometry. "We have a low dropout rate."

Currently, says McClure, students at his institution are graduating with an average indebtedness of $21,000. Even at that, he figures, "It's a worthwhile investment."

For more information on a career in optometry, write:

* American Optometric Association, Education and Manpower Division, 243 N. Lindbergh Blvd., St. Louis, Mo. 63141. Include stamped, self-addressed business envelope.

* National Optometric Association, Minority Recruitment, Box F, East Chicago, Ind., 46312.

* Association of Schools and Colleges of Optometry, Suite 406, 600 Maryland Ave. SW, Washington, D.C. 20024.