Fig 3. Fundus image of representative normal and affected dogs.

The normal canine ONH appears pink and irregularly shaped due to myelination of the retinal ganglion cell axons as shown in this 72.1-month old carrier of the G661R ADAMTS10 missense mutation (A). While the ONH still appears normal early in the disease process (B1, 21.1-month old affected dog), it becomes dark and round with advanced disease-related atrophy (B2 and B3, 89.4- and 94.9-month affected dogs, respectively). With moderate atrophy, the ONH still appears slightly pink and irregularly shaped (B4). Because of secondary cornea and lens opacification with advanced glaucoma, the quality of the fundus images deteriorates and makes visualization of details such as cupping difficult. The identification of these representative dogs in the lower right corners of the images matches those in Table 1.