Critical Flicker Frequency (CFF) is Reduced in Children with Suspected Reading Disability

Dr. Tannen’s Research Review and Commentary:

In this study (of our SUNY Optometry-based research team), the critical flicker frequency threshold (CFF) of 39 children who had a history of  reading disability were compared to 23 age matched normal readers.  CFF threshold discriminated well between reading disabled and normal readers.   CFF threshold is a test that measures visual magnocellular function and adds further evidence to the  growing body of evidence that shows reduced temporal processing in individuals with reading disability. 

CFF threshold is a simple test to perform and hopefully will be commercially available  within the next year as a clinical test for optometrists and other health professionals to perform. (NOTE: I have no financial interest in this device). 

This research will be presented as a Poster Presentation at the Association for Research in Vision and Ophthalmology (ARVO) 2011 Annual Meeting 

Authors: Barry Tannen^1A, Kenneth J. Ciuffreda^1B, Noah M. Tannen. ^ADept of Clinical Sciences, ^BDept of Vision Sciences, ¹SUNY/State College of Optometry, New York, NY.Abstract:
Purpose: To assess the critical flicker frequency threshold (CFF) clinically in children with suspected reading disability.
Methods: The CFF threshold of 39 children between the ages of 7-16 years with suspected reading disability based on the chief complaint of “reading problems” was measured in the primary author’s private practice during the course of a comprehensive vision evaluation. 23 age-matched controls without any history or complaint of reading problems were also tested. CFF threshold was assessed binocularly with the habitual near prescription in place at 40 cm. The test light consisted of 4 contiguous white light-emitting diodes (LEDs) with which were mounted within a handheld rectangular enclosure and provided diffuse illumination via a circular translucent plexiglass cover. The size of the test field was 3.5 degrees with a luminance of 100cd/m2 performed in a dimly illuminated room. The flicker rate was controlled by a calibrated dial, which allowed the experimenter to gradually increase or decrease the flicker frequency over a range of 30 to 60 Hz. Patients were instructed to fixate the center of the test field, while the rate of flicker was either increased (‘‘stops flickering’’) or decreased (‘‘starts to flicker’’) at a rate of approximately 1 Hz per second. 3 ascending and 3 descending measurements were taken alternately. A single mean CFF threshold was obtained by averaging the 6 measurements.
Results: Mean CFF threshold was 45.48Hz +/-3.0Hz in the normal readers and 39.59+/-1.4Hz in the patients with reading problems, which was significantly different (t-test, p<0.01). Only 3 of the 39 children (7.5%) with reading problems had a CFF threshold within 1 standard deviation of the mean CFF threshold of normal readers in our sample.

Conclusions: Mean CFF threshold discriminated well between children with a chief complaint of reading problems and those with no history or report of reading problems. This agrees with earlier studies demonstrating reduced temporal processing reflecting visual magnocellular impairment in individuals with reading disability. We suggest that the CFF threshold test, which is both simple and rapid, be considered for inclusion in the clinical vision testing for children presenting with reading problems.