Postnatal Growth of Eye Size in DBA/2J Mice Compared With C57BL/6J Mice: In-vivo Analysis With OCT

Abstract

Purpose: : The murine eye is known to undergo substantial post-natal growth that continues beyond the period of sexual maturity. In mouse models of glaucoma, IOP elevation may induce abnormal eye growth that needs to be determined. We have characterized post-natal changes in eye size in glaucomatous DBA/2J (D2) mice in-vivo by means of optical coherence tomography (OCT) and compared them to those occurring in C57BL/6J mice (B6).

Methods: : Mice ranging in age between 2.5 and 10 months were tested (D2, n=18; B6, n=17). A custom time-domain OCT system was optimized for cross-sectional imaging of the whole mouse eye, including precise alignment of the mouse eye with the imaging system (Uhlhorn et al,Vision Res 2008). The system has an axial scan length of 7.1 mm in the ocular tissue and produces axial a-scan interferograms at a rate of 20A-lines/s with a resolution 12 µm in the air. IOP was measured with Tonolab rebound tonometer.

Results: : Axial length, anterior chamber (AC) depth, and lens thickness increased significantly (P<0.001) between 2.5 and 10 months of age in both D2 and B6 mice. Age-related changes were well fit by linear regressions on log-log coordinates (R² range: 0.65 to 0.9). However, the increase in axial length was larger in D2 (21%) compared to B6 (9%). The increase in axial length was accounted for, in large part, by increase in AC depth (D2:10%; B6; 1.5%) and by increase in lens thickness (D2: 7%; B6: 9%). Corneal thickness was similar in D2 and B6 mice and did not significantly change with age. IOP increased (P<0.001) relatively more in D2 (7.5 mm Hg, 48%) than in B6 mice (3.3 mm Hg, 19%).

Conclusions: : In DBA/2J mice, post-natal eye growth is relatively larger than that of C57BL/6J mice, and is largely accounted for by relatively greater increase in AC depth. Differential increase in AC depth between D2 and B6 is associated with differential increase in IOP, which seems to be a likely causal factor. This quantitative anatomical information can be non-invasively obtained in-vivo and will facilitate future studies using mouse glaucoma models.

Keywords: development • anterior chamber • intraocular pressure