Publication Date

2014-07-10

Availability

Open access

Embargo Period

2014-07-10

Degree Name

Master of Science (MS)

Department

Biomedical Engineering (Engineering)

Date of Defense

2014-06-16

First Committee Member

Jorge Bohorquez

Second Committee Member

Ozcan Ozdamar

Third Committee Member

Vittorio Porciatti

Abstract

Flicker electroretinograms are steady-state electroretinograms (ERGs) generated by high rate flash stimuli that produce overlapping periodic responses. When a flash stimulus is delivered at low rates, a transient response named flash ERG (FERG) representing the activation of neural structures within the outer retina is obtained. Although FERGs and flicker ERGs are used in the diagnosis of many retinal diseases, their waveform relationships have not been investigated in detail. This study examines this relationship by extracting transient FERGs from specially generated quasi steady state, random ERGs at stimulation rates above 10 Hz and similarly generated conventional flicker ERGs. The ability to extract the transient FERG responses by deconvolving flicker responses to temporally jittered stimuli at high rates is investigated at varying rates. FERGs were obtained from seven normal subjects stimulated with LED-based displays, delivering steady state, low jittered quasi steady state and low jittered random responses at five stimulation rates of 10, 15, 32, 50, 68 Hz. The two deconvolution methods (CLAD and RAD) enabled a successful extraction of “per stimulus” unit transient ERG responses for all high stimulation rates. The deconvolved FERGs were used successfully to synthesize flicker ERGs obtained at the same high stimulation rates. The experimental results showed that, as the stimulation rate increased, the a-wave and b-wave amplitudes decreased significantly between the 10 and 15 Hz and 15 and 32 Hz. Furthermore, the implicit time of a-wave increased between 2 and 10 Hz and decreased between 15 and 32 Hz. Moreover, b-wave decreased significantly as the stimulation rate increased up to 32 Hz.

Keywords

Flicker ERG; Electroretinograms; Steady state ERG; Transient ERG response

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