Section 11-E: Benefits of studying glaucoma genetics

Every year, thousands of Americans are blinded by glaucoma. In most cases, the loss of vision caused by glaucoma could be limited or prevented by currently available therapies if the disease were identified in its early stages. Many cases of glaucoma are not discovered until vision has already been permanently lost, because clinical signs of early glaucoma are subtle and silent to the patient.

The discovery of glaucoma disease genes provides a method for early detection of glaucoma. Genetic testing for disease-causing mutations in these genes is capable of identifying those at highest risk for developing glaucoma years to decades before vision loss or other symptoms are manifested. Heightened surveillance and early institution of glaucoma therapy can then be provided to these patients before any vision is lost, perhaps even before any symptoms are observed.

Testing to determine the genetic causes of glaucoma will also facilitate the development and evaluation of new medical therapies and surgical interventions.

Glaucoma is a collection of distinct diseases with similar clinical appearances. Genetic testing will allow physicians to identify groups of patients with the same biochemical basis of glaucoma. Some sub-types of glaucoma may respond to certain treatments while others may not. Identification of such well-characterized groups of patients to test new medical therapies and surgical interventions will help speed the discovery of new, effective treatments.

Genetic study of inherited diseases such as glaucoma will likely promote advances in therapy as well as diagnosis. For example, methods to replace defective genes with normal functioning genes (trans-genes) are being perfected. At present, however, there are some limitations to this technology known as gene therapy. Some of the major obstacles in using gene therapy include difficulties in obtaining 1) effective delivery of the trans-genes to the right tissues of the eye, 2) control of transgene activity, 3) maintenance of transgene effect, and 4) low-cost methodology. Advances in all of these areas are being realized, and gene therapy for glaucoma may be possible in the future.

Most inherited genetic defects, however, may be treated with currently available medical and surgical therapies. As the functions of disease-causing genes are discovered, conventional treatments may also be tailored to mitigate disease-causing defects. In one form or another, genetic research opens the promise of a new generation of sight-saving therapies.

Section 11-F: References

1. Fingert JH, Anderson, MG. Chapter 144: Glaucoma. In Emery and Rimoin’s Principles and Practice of Medical Genetics. 5th Ed. Elsevier, Philadelphia, 3133-3156, 2006.
   
2. Allingham RR, et al., editors. Shields’ Textbook of Glaucoma, ed. 5. Philadelphia: Lippincott Williams & Wilkins, 163-169, 2005.
   
3. Fingert JH, Stone EM, Sheffield VC, Alward WLM. Myocilin Glaucoma. Survey of Ophthalmology, 47: 547-561, 2002.
   
4. Sheffield VC, Alward WLM, Stone EM. Chapter 242: The Glaucomas. In Scriver CR, et al, eds. The Metabolic & Molecular Basis of Inherited Disease. 8th Ed. MacGraw-Hill, St. Louis, 6063-6075, 2001.
   
5. Johnson AT, Alward WLM, Sheffield VC, Stone EM. Chapter 2: Genetics and Glaucoma. In Ritch R, Shield MB, Krupin T, eds. The Glaucomas. 2nd Ed. Mosby, Chicago, 39-54, 1996.
   
6. GeneTests http://www.genetests.org
   
7. GeneReviews . see http://tinyurl.com/34eks3(http://www.genetests.org/servlet/access?id=8888892&key=3L1fqyZufuJdP&fcn=y&fw=29qT&filename=/reviewsearch/searchdz.html)
   
8. The John and Marcia Carver Non-profit Genetic Testing Laboratory http://www.carverlab.org.
   
   

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