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 minutes 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 30Hz). 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 minutes of dark adaptation peaking at 446µv and 377µv for horse number 1 and 2 respectively. The b-wave amplitudes of the combined rod-cone response were OS- 459µv and OD- 392µv for horse number 1 and OS- 491µv and OD- 608µv for horse number 2. The amplitude of the flicker ERG for horse number 1 was OS- 86 µv and OD- 110 µv and for horse number 2 OS- 80 µv and OD- 74 µv.

Conclusions Extensive bullet-hole chorioretinal lesions do not appear to compromise outer retinal function in these horses.