Ocular biometry in rabbits using computed tomography.

OBJECTIVE: To describe a repeatable method of measuring ocular structures and to establish ocular biometry reference ranges in adult domestic rabbits (Oryctolagus cuniculus) without medical history or imaging findings consistent with ophthalmic disease using a 64-slice multidetector computed tomography scanner. PROCEDURE: In this retrospective and observational anatomic study, 100 eyes from 50 rabbits without medical history or imaging findings consistent with ophthalmic disease who received a head computed tomography scan were selected for measurement of globe length, width, and height using 3D multiplanar reconstruction. Lens width and length, the anteroposterior length of the anterior and vitreous chambers, and attenuation of the lens and vitreous chamber were collected. These parameters were compared against age, sex, weight, body condition, and ear conformation. RESULTS: A reference guide was established, with globe width being the largest dimension (18.03 ± 0.81 mm), followed by height (17.18 ± 0.69 mm) and then length (16.64 ± 0.66 mm). Increased weight was associated with an increase in globe height (p = 2.43 × 10-5 ), length (p = 1.63 × 10-4 ), and width (p = 7.0 × 10-3 ). Increased age was associated with increased lens attenuation (p = 1.28 × 10-7 ) and increased transverse lens width (p = 1.64 × 10-3 ). Inter- and intra-observer agreement was excellent. CONCLUSIONS: CT is a reliable modality for measurement of ocular biometry dimensions in rabbits. These reference values can be applied to aid in identifying diseases that affect the dimensions of the ocular structures in rabbits over 18 months of age.

Empirical data demonstrates risk-tradeoffs between landscapes for herbivorous fish may promote reef resilience.

Herbivores balance resource requirements with predation risk, which can differ among landscapes; hence, landscape can shape these trade-offs, influencing herbivore distribution and behavior. While this paradigm has been well established on coral-dominated reefs, tropical reefs worldwide are shifting to algal dominance. If herbivores avoid algae due to higher risk and forage in coral, these algal states may be stabilized. However, if herbivores forage more in resource-rich algal states, this may promote coral recovery. We assessed the distribution and behavior of herbivorous fishes in Moorea, French Polynesia in coral and algal turf-dominated fringing reef sites. Acanthuridae were more abundant in coral states and Labridae, tribe Scarinae, in algal turf states, though total fish abundances were equivalent in the two states. Fish in both families spent more time feeding in algal states and hiding/swimming in coral states. Thus, behavior reflects the trade-off between resource acquisition and refuge in these two landscapes and may promote recovery to coral.