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

The research article investigates how widespread ‘bullet-hole’ lesions in the nontapetal part of the eye’s fundus affect the retinal function in horses, as measured by full-field electroretinography (ERG). The results suggest that these types of lesions do not seem to impact the outer retinal function of these horses.

Methodology

• Two horses, both with numerous bullet-hole lesions in the nontapetal fundus of both eyes, were selected for this study.
• A low-intensity light stimulus was initially used to record the ERG from the eye with the most lesions.
• The light stimulus was set at 0.03 cd s/m(2) and applied at times T = 5, 10, 15, 20 minutes of dark adaptation.
• Thereafter, the combined rod-cone response was assessed bilaterally in response to a high-intensity light stimulus (3 cd s/m(2)), succeeded by the evaluation of cone function via a flicker stimulus (3 cd s/m(2) at 30 Hz).
• Off-line analysis was carried out on the ERG recordings.

Results

• Surprisingly, despite the severe bullet-hole lesions located in the nontapetal fundus in both eyes of each horse, the retinal function, measured by ERG, did not show any identifiable deficits.
• As the dark adaptation period progressed from 5 to 20 minutes, there was a continuous increase in the b-wave amplitude of the full-field ERG, which peaked at 446 μv and 377 μv for the first and second horses respectively.
• The b-wave amplitudes of the combined rod-cone response were recorded as being OS- 459 μv and OD- 392 μv for the first horse, and OS- 491 μv and OD- 608 μv for the second horse.
• For the first horse, the amplitude of the flicker ERG was OS- 86 μv and OD- 110 μv while for the second horse it was OS- 80 μv and OD- 74 μv.

Conclusion

• The researchers concluded that extensive bullet-hole chorioretinal lesions do not appear to have a negative effect on the outer retinal function of horses based on their study.