advertisement
Abstract #8906 Published in IGR 5-2
Tonography demonstrates reduced facility of outflow of aqueous humor in myocilin mutation carriers
Wilkinson CH; Van der Straaten D; Craig JE; Coote MA; McCartney PJ; Stankovich J; Stone EM; Mackey DAJournal of Glaucoma 2003; 12: 237-242
PURPOSE: To demonstrate the effect in vivo of the myocilin gene mutation Thr377Met on outflow facility of aqueous humor, as measured by tonography. MATERIAL AND METHODS: Forty-two members of a pedigree known to carry the Thr377Met mutation were examined for glaucoma, evaluated with tonography, and screened for myocilin mutations. Tonography was used to calculate the coefficient of aqueous outflow facility (C), as well as the ratio of the resting intraocular pressure (IOP) to C (P0/C). Subjects were reexamined for glaucoma five years after tonography. RESULTS: Seven subjects were excluded because of previous treatment known to alter facility of aqueous outflow. The mean outflow facility of the eyes of the 12 subjects carrying the Thr377Met mutation was significantly reduced compared with the 23 non-carriers' eyes using both C (p < 0.001) and P0/C (p < 0.001). Reduced outflow facility was also demonstrated in those mutation carriers who were not yet expressing clinical signs of glaucoma or ocular hypertension when measured using C (p = 0.015) and P0/C (p = 0.001). After five years, progression towards glaucoma had occurred in five of the myocilin mutation-carriers, two of whom showed bilateral progression; three carriers remained completely normal. Four subjects had bilateral glaucoma at the outset and remained unchanged. The carriers' eyes that progressed towards glaucoma had reduced outflow facility compared with those that remained normal, although the difference was not statistically significant. CONCLUSIONS: Carriers of the myocilin Thr377Met mutation have reduced outflow facility, which may be detected prior to developing glaucoma. Tonography was not seen to be clinically useful in predicting progression towards glaucoma.
Dr. D.A. Mackey, Center for Eye Research Australia, Department of Ophthalmology, University of Melbourne, Royal Victorian Eye and Ear Hospital, 32 Gisborne Street, East Melbourne, Victoria, Australia 3002. D.Mackey@utas.edu.au
Classification:
1.2 Population genetics (Part of: 1 General aspects)
6.2 Tonography, aqueous flow measurement (see also 2.6) (Part of: 6 Clinical examination methods)