Assessment of Axial Length Measurements in Mouse Eyes

Abstract

Purpose To compare measurements of murine ocular axial lengths (AL) made with 780 nm partial coherence interferometry (PCI) and 1310 nm spectral domain–optical coherence tomography (SD-OCT). Methods AL was measured at postnatal day (P) 58 in C57BL/6J mice. Repeated AL measurements were taken using a custom-made 780 nm PCI and a commercial 1310 nm SD-OCT. Intra- and inter-user variability was assessed along the central optical axis as well as two-degree off-axes angles with the SD-OCT. Data were collected and analyzed using Cronbach’s alpha (α), Bland-Altman coefficient of repeatability (CR), agreement plots, and intra-class correlation coefficients (ICC). Results Axial length measurements agreed well between the two instruments (3.262 ± 0.042 mm for PCI; 3.264 ± 0.047 mm for SD-OCT; n= 20 eyes). The ICC for PCI compared to SD-OCT was 0.92, confirming high agreement between the two instruments. Intra-user ICC for the PCI and SD-OCT were 0.814 and 0.995, respectively. Similarly, inter-user ICC for PCI and SD-OCT were 0.970 and 0.943, respectively. Using SD-OCT, a two-degree misalignment of the eye along the horizontal meridian produced mean differences in AL of −0.002 ± 0.017 mm relative to the centrally aligned images, while similar misalignment along the vertical meridian created 0.005 ± 0.018 mm differences in AL measurements. Conclusions AL measurements from the 780 nm PCI and 1310 nm SD-OCT correlate well. Multiple statistical indices indicate that both instruments have good precision and agreement for measuring murine ocular axial length in vivo. While the vertical meridian had the greater variability in AL in the small mouse eye; two-degree off-axes differences were within the standard deviation of centrally aligned AL.

Visually-Driven Ocular Growth in Mice Requires Functional Rod Photoreceptors

“…In a selection of animals that underwent PCI and SD-OCT measurements, the axial length values were averaged together, since measurements by the two techniques were in good agreement (interclass correlation coefficient ¼ 0.94). 58 For FD results, refractive errors are presented as ''myopic shift'' (difference between right and left eyes), since the refractive errors of untreated opposite eyes were not statistically different from those of naïve control eyes. Axial lengths of FD cohort were normalized to 4-week-old values (baseline) to eliminate individual variability in eye size due to differences in body size.…”

“…57 While still anesthetized, axial length measurements were obtained using 1310 nm spectral-domain optical coherence tomography (SD-OCT; Bioptigen, Inc., Durham, NC, USA), as described previously. 58 After measurements, mice were given yohimbine (2.1 mg/kg) to reverse the effects of anesthesia and reduce the development of corneal lesions. 60 Mice recovered on a warming pad with saline drops applied to the eyes.…”

“…57 First, eyes were dilated with 1% tropicamide and measurements of refractive state obtained using an automated photorefractor. 23,42,58 Axial length measurements of a subset of mice (see Table for animal numbers) were acquired using a custom-built 845-nm time-domain partial coherence interferometer (PCI) after being placed in an open-ended conical tube with the mouse's head pedestal stabilized by a clip. 58,59 Mice then were anesthetized (ketamine 80 mg/kg and xylazine 16 mg/kg) and refractions repeated to obtain a more stabilized measurement with standard deviations of less than 0.5 diopters (D).…”

“…23,42,58 Axial length measurements of a subset of mice (see Table for animal numbers) were acquired using a custom-built 845-nm time-domain partial coherence interferometer (PCI) after being placed in an open-ended conical tube with the mouse's head pedestal stabilized by a clip. 58,59 Mice then were anesthetized (ketamine 80 mg/kg and xylazine 16 mg/kg) and refractions repeated to obtain a more stabilized measurement with standard deviations of less than 0.5 diopters (D). 57 While still anesthetized, axial length measurements were obtained using 1310 nm spectral-domain optical coherence tomography (SD-OCT; Bioptigen, Inc., Durham, NC, USA), as described previously.…”

No Evidence for Association of SCO2 Heterozygosity with High-Grade Myopia or Other Diseases with Possible Mitochondrial Dysfunction

“…Previous characterization of this mouse model of Sco2 deficiency revealed that heterozygous KI/WT, homozygous KI/KI, and compound heterozygous KI/KO mice were viable but had muscle weakness and respiratory chain deficiencies in multiple tissues (most prominently in the KI/ KO mice) Yang et al 2010); however, no ophthalmologic analysis had been performed. Highgrade myopia is associated with globe axial elongation sufficient to cause a refractive distortion of at least À6.0 diopters, and the level of myopia in mouse models has previously been assessed by measuring globe axial length (Park et al 2012). …”