Just as clear photography depends on precisely focusing incoming light rays onto film, clear vision depends on focusing beams of light onto the retina. Consequently, when the normally crystalline lens a component of the eye's light-focusing apparatus -loses its transparency there is a breakdown in the camera. This process, known as cataract formation, leads to partial or total blindness. While cataractous lenses often can be removed and effective vision restored via use of special eyeglasses, researchers hope ultimately to be able to reverse or even prevent their formation. Success on this front, though, depends on a thorough understanding of the chemical events involved in cataract formation, and thus far. technical limitations have kept this beyond the ophthalmologist's grasp. Now, however, scientists have transformed an old analytical technique into a tool that not only is helping to unravel the molecular mysteries of cataract formation, but also is illuminating serious flaws in the conventional test models of this phenomenon. That tool is nuclear magnetic resonance (NMR) spectroscopy, and as its name implies, it gathers information from atoms whose nuclei are magnetic. All major particles in a nucleus that is, protons and neutrons have magnetic moments, explains Thomas Glonek of the Chicago College of Osteopathic Medicine. These miniature magnets form pairs, a north-south teaming with a south-north, to leave the overall magnetic moment of the nucleus nil. But in many nuclei, an unpaired neutron is leftover, and that particle causes the entire atom to be magnetic, says Glonek, who, along with Jack V. Greiner and colleagues, is using the properties of such atomic magnets to probe lens chemistry. Using NMR technology, the magnetic atoms in a sample first are allowed to align themselves in a magnetic field and then are knocked out of alignment with lowenergy radio waves. The energy that a particular atom absorbs to disalign itself produces a characteristic signal that is recorded as a printed peak on an NMR spectrum. The position of the peak on a printout helps identify the molecule on which the atomic atom sits, and the area under the peak represents the quantity of the molecule present in the sample. In the early days of NMR, printouts consisted of peaks from the magnetic isotope of hydrogen (H-1), which served only to help chemists determine structures of molecules in solids and solutions. At that point, because the hydrogen spectrum from a living system usually shows nothing more than a signal for water, NMR spectroscopy was virtually useless on biologic samples. (H-1 NMR spectroscopy differs from its descendant H-1 NMR imaging -a picture-producing analytical technique that some researchers believe shows cancerous tissue-detecting potential [SN: 6/9/79, p. 380].) The technique was slow to find biochemical applications, Glonek explains, because signals of atomic nuclei more relevant to living systems were too weak to detect with early NMR technology Eventually, though, with the aid of highpowered magnets and more sensitive spectrometers, researchers began probing biochemically relevant nuclei those from phosphorous-31 (P-31) and carbon-13 (C-13)in systems such as red blood cells and muscles. Thus began the NMR probe of complete biological components, an area of research that recently embraced analysis of the chemical events that may initiate cataract formiation. Previously, the study of eye chemistry meant analytically sifting through many ground up lenses in hopes of extracting just one small piece of information. Now, r