To analyze the characteristics of full-field stimulus thresholds (FST) in patients with middle-and late-stage inherited retinal dystrophy (IRD), and to explore the feasibility of the FST test in evaluating the retinal function for IRD patients.

It was a retrospective case series study. Twenty-eight patients with IRD whose full-field electroretinogram (ERG) results showed no electrical activity (20 patients) or a serious decrease in electrical activity (8 patients) were enrolled, including 17 males and 11 females, with a median age of 32 years. Ten normal controls were also enrolled. All eyes had a measurement of best corrected visual acuity (BCVA) and an ERG test. FST stimulated by red, blue and white lights were examined with an electrophysiological instrument. The decimal value of BCVA was converted to logarithm of the minimum angle of resolution. Data of the better eye of each participant were used for statistical analysis. Independent sample t-test was used to analyze the difference in FST among patients. Linear regression was used to analyze the correlation between FST, visual acuity and ERG amplitudes.

The BCVA of all eyes was 0.7±0.6. Under the stimulation of red, blue and white lights, the FST were(-27.0±7.1), (-47.4±12.2) and(-41.7±11.5) dB in the 8 eyes with decreased electrical activity, (-16.3±7.0), (-27.2±13.7) and(-23.5±12.5) dB in the 20 eyes with no electrical activity, and(-39.9±4.0), (-65.8±4.0) and(-58.5±3.4) dB in the 10 control eyes, respectively. The FST of IRD patients were higher than the normal controls. The FST with red, blue and white lasers in eyes with no electrical activity were higher than those with severely reduced electrical activity (t=-3.472, -3.506, -3.433; all P=0.002). The BCVA was not correlated with the FST under the red, blue and white light stimulation in eyes with a serious reduction in electrical activity (r=0.134, 0.011, 0.010; P=0.055, 0.601, 0.611). There was a linear correlation between the red light stimulus FST and the b-wave amplitude of flicker ERG response (r=-0.591, P=0.026), but there was no significant correlation between other amplitudes and FST.

The FST test is a supplementary method to evaluate the retinal function of patients with middle-and late-stage IRD. It can quantitatively reflect the function of rod and cone cell system. As the retinal function of IRD patients decreases, the FST gradually increase.

Retinal dystrophies; Eye diseases, hereditary; Electroretinography; Photic stimulation; Visual field tests; Sensory thresholds