Glaucoma is a condition of increased pressure within the eyeball, which can lead to gradual loss of sight. In this situation, it is best to proceed cautiously and patiently, and to be well informed. Your student should confer with her physician and/or ophthalmologist regarding all the particulars involving her condition and then report back to you with information about what she can and cannot do physically. Usually, there are minimal restrictions once glaucoma is controlled.
You specifically asked about alternatives for inversions during class. In this case, have her do Supta Virasana (Reclining Hero Pose) or Supta Baddha Konasana (Reclining Bound Angle Pose) during the time the class is doing head balance poses, and have her try a supported but not too high Setu Bandha Sarvangasana (Bridge Pose) with her eyes fully covered in lieu of shoulder balance poses. See that she takes her time, goes slowly, and does not hold her breath while coming into and out of the poses.
She may also do standing forward bends, such as Parsvottanasana (Intense Side Stretch Pose), Uttanasana (Standing Forward Bend), and Prasarita Padottanasana (Intense Spread Leg Stretch), with her head elevated and torso and head resting on a bench. Additionally, forward bends and twists would be beneficial, and your student should practice them regularly.
Certified Advanced Iyengar instructor Dean Lerner is co-director of the Center for Well-being in Lemont, Pennsylvania and teaches workshop across the United States. He is a longtime student of B.K.S. Iyengar and served a four-year term as president of the Iyengar National Association of the United States. Known for his ability to teach yoga with clarity and precision, as well as warmth and humor, Dean has conducted teacher training classes at Feathered Pipe Ranch in Montana and other locations.