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Which method of flicker perimetry is most effective for detection of glaucomatous visual field loss?
1Optics and Visual Assessment Laboratory, Department of Ophthalmology, University of California, Davis, Sacramento 95816, USA.
Purpose:
The authors compared the efficacy of two different forms of flicker perimetry: temporal modulation perimetry (TMP), which measures contrast thresholds for a fixed temporal frequency, and critical flicker frequency (CFF), which measures the highest frequency for which flicker is detected at a fixed contrast.
Methods:
The authors compared 16 patients with early to moderate glaucomatous visual field loss with 16 age-matched normal controls. Flicker stimuli consisted of 2 degrees diameter targets of 2 seconds in duration, presented in 44 locations throughout the central 30 degrees visual field. Flicker was presented within a cosine envelope to avoid temporal transients. For TMP, contrast sensitivity thresholds were measured for 8-Hz sinusoidal flicker; CFF thresholds were measured for a stimulus of 100% contrast.
Results:
The results indicate that TMP and CFF produced similar test-retest reliability in normals. CFF had slightly better reliability in glaucoma patients. Receiver operating characteristic analysis revealed that TMP could provide better separation of normals and glaucoma patients than did CFF. Similar findings were obtained when the thresholds for both procedures were converted to Z scores.
Conclusions:
Both methods of flicker perimetry testing provide acceptable test-retest reliability, and both can distinguish normal subjects from glaucoma patients. However, TMP is more effective in separating normal subjects from glaucoma patients than CFF, suggesting that TMP is the method of choice for detecting glaucomatous damage using flicker perimetry.