# Ultrasonographic Ocular Biometry of the Greater Caribbean Manatee (Trichechus manatus manatus)

## TL;DR

This study used ultrasound to measure eye dimensions in manatees and found that some eye features change with age.

## Contribution

The study provides the first ultrasonographic ocular biometric data for the greater Caribbean manatee across different age groups.

## Key findings

- Corneal thickness, vitreous chamber depth, and axial globe length were similar across age groups.
- Anterior chamber depth and axial lens length increased with age.
- Positive correlations between body length and ocular parameters were significant only in calves.

## Abstract

This study aimed to characterize the ocular biometry of the
Trichechus manatus manatus
applying B‐mode ultrasonography across different age groups. Twenty‐two animals were assessed employing a portable ultrasound device equipped with a linear transducer. Five ocular parameters were assessed: corneal thickness (CT), anterior chamber depth (ACD), axial lens length (ALL), vitreous chamber depth (VCD), and axial globe length (AGL). Data were statistically analyzed at a 5% significance level based on normality and variance. The mean values (cm) for the right eye of calves, juveniles, and adults were, respectively, CT (0.082 ± 0.012; 0.088 ± 0.011; 0.091 ± 0.010), ACD (0.040 ± 0.005; 0.051 ± 0.008; 0.052 ± 0.007), ALL (0.345 ± 0.028; 0.367 ± 0.016; 0.414 ± 0.020), VCD (1.137 ± 0.076; 1.155 ± 0.062; 1.161 ± 0.089), and AGL (1.606 ± 0.098; 1.663 ± 0.071; 1.720 ± 0.094). Values for the left eye were CT (0.082 ± 0.012; 0.088 ± 0.012; 0.087 ± 0.011), ACD (0.041 ± 0.008; 0.048 ± 0.006; 0.052 ± 0.007), ALL (0.345 ± 0.028; 0.381 ± 0.027; 0.411 ± 0.025), VCD (1.147 ± 0.076; 1.174 ± 0.045; 1.166 ± 0.086), and AGL (1.617 ± 0.086; 1.693 ± 0.062; 1.717 ± 0.095). CT, VCD, and AGL were similar across age groups, while ACD and ALL increased with age. Positive correlations between body length and ocular parameters were significant only in calves. Ocular ultrasonography is, thus, an effective, safe, and reproducible tool for ophthalmic evaluations in T. m. manatus.