Electroretinogram evaluation of equine eyes with extensive ‘bullet-hole’ fundic lesions

Fonte: Rachel A. Allbaugh, Gil Ben-Shlomo and R. David Whitley

Appearance of the left fundus in the same patient showing subjectively denser bullet-hole lesions.
   Appearance of the left fundus in the same patient showing subjectively denser bullet-hole lesions.

Objective: To evaluate the impact of extensive bullet-hole nontapetal fundic lesions in horses on retinal function as measured by full-field electroretinography (ERG). Materials and Methods: Full-field ERG was performed on two horses with numerous bullet-hole lesions in the nontapetal fundus of both eyes. The ERG was first recorded from the eye with the more extensive lesions in response to a low-intensity light stimulus (0.03 cd s/m2) that was given at times (T) T = 5, 10, 15, 20 min of dark adaptation. Consecutively, combined rod–cone response was evaluated bilaterally in response to high-intensity light stimulus (3 cd s/m2), followed by cone function evaluation by flicker stimulus (3 cd s/m2 at 30 Hz). Off-line analysis of the ERG recordings was then performed. Results: Despite extensive bullet-hole lesions in the nontapetal fundus bilaterally in both horses, retinal function as measured by ERG did not show any observable deficits. The b-wave amplitude of the full-field ERG increased continuously from 5 to 20 min of dark adaptation peaking at 446 lv and 377 lv for horse number 1 and 2, respectively. The b-wave amplitudes of the combined rod–cone response were OS- 459 lv and OD- 392 lv for horse number 1 and OS- 491 lv and OD- 608 lv for horse number 2. The amplitude of the flicker ERG for horse number 1 was OS- 86 lv and OD- 110 lv and for horse number 2, OS- 80 lv and OD- 74 lv. Conclusions: Extensive bullet-hole chorioretinal lesions do not appear to compromise outer retinal function in these horses.

 

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