|Title||WHY DOES THE HRT II SOMETIMES FAIL?|
|Author, Co-Author||Jerome Sherman, Sanjeev Nath, Herminder Boparai|
|Abstract|| PURPOSE: This study was undertaken to document and analyze the reasons for HRT failures. A failure was defined as a normal HRT, according to the Moorfields regression analysis, in a glaucoma subject with glaucomatous type field defects.
METHODS: Analysis of HRT findings in 1) subjects with POAG alone (N =71) and in 2) subjects with glaucoma as part of an "overlap syndrome" (n=29).
RESULTS: A total of 15 subjects (15%) demonstrated HRT failures. Analysis of HRT failures revealed the erroneous placement of the HRT reference plane, arbitrarily set at 50u below the surface in the papillo-macular (PM) bundle. If the PM bundle is thinned or if it is sitting at the base of a staphyloma or deep crescent, the reference plane will be placed much deeper into the retina. Myopic subjects with deep temporal crescents (n=3) demonstrate less cupping with the HRT than with ophthalmoscopy and were often misclassified. Subjects with central field reduction due to loss of the PM bundle (n=2) also demonstrate a normal HRT. Another common finding leading to HRT misclassification was disc drusen (dd) in glaucoma subjects (n=3) since dd fill the cup. Some subjects with high myopia and glaucoma (n=2), angle closure glaucoma (n=1), Posner-Schlossman syndrome (n=1), and pigmentary glaucoma (n=1) failed to demonstrate both clinical and HRT cupping. Here, spikes in IOP appear to result in RNFL loss without cupping. Failures also occurred in glaucoma subjects with LHON (n=1), and persistent fetal vasculature (n=1).
CONCLUSIONS: The HRT is a useful clinical instrument. Occasional failures and the reasons for the failures alert the clinician to consider the categories of failures identified above.
|Affiliation of Co-Authors||Eye Institute and Laser Center, Eye Institute and Laser Center|