# Determination of Ophthalmic Parameters and Ocular Morphology in Ring‐Necked Parakeets (Psittacula krameri)

## TL;DR

This study establishes normal eye parameters and describes eye structure in ring-necked parakeets, aiding in the diagnosis of eye conditions in this bird species.

## Contribution

The paper provides the first detailed empirical data on ophthalmic parameters and ocular morphology specific to ring-necked parakeets.

## Key findings

- Normal values for tear production, intraocular pressure, corneal thickness, and other eye parameters were determined in ring-necked parakeets.
- Gram-positive bacteria, particularly Staphylococcus sp., were the most common in the corneoconjunctival microbiota.
- Young parakeets have brown irises that transition to blue by 60 days of age.

## Abstract

To determine normal ophthalmic test values and to describe the ocular morphology of ring‐necked parakeets (
Psittacula krameri
).

33 captive birds were examined, although not all tests were conducted on each bird. The tests included endodontic absorbent paper point tear test (EAPPTT), intraocular pressure (IOP), corneal touch threshold (CTT), central corneal thickness (CCT), palpebral and corneal diameters, ocular ultrasonography, and corneoconjunctival microbiota. The iris coloration of seven young parakeets was evaluated, and two macerated skulls were described.

Normal values obtained were: EAPPTT: 7.57 ± 1.95 mm/min; IOP: 12.47 ± 1.51 mmHg; CTT: 2.46 ± 0.5 mm; CCT: 0.12 ± 0.006 mm; palpebral diameter: 8.04 ± 0.49 mm,; corneal diameter: 6.41 ± 0.49 mm. In ocular ultrasonography, the dimensions in the sagittal plane were: axial globe length (AGL): 0.94 ± 0.02 cm; vitreous chamber depth (VCD): 0.47 ± 0.02 cm; lens axial length (LAL): 0.32 ± 0.01 cm; anterior chamber depth (ACD): 0.1 ± 0.01 cm; pecten width (PW): 0.12 ± 0.02 cm, and pecten length (PL): 0.42 ± 0.04 cm. In the dorsal plane: AGL: 0.93 ± 0.03 cm; VCD: 0.47 ± 0.02 cm; LAL: 0.32 ± 0.03 cm; ACD: 0.1 ± 0.01 cm; PW: 0.32 ± 0.04 cm, and PL: 0.35 ± 0.03 cm. Microbiota analysis identified predominantly gram‐positive bacteria, with Staphylococcus sp. being the most common (47.5%). Anatomical evaluation of skulls revealed a large lacrimal process extending to the zygomatic process, and the margins of the processes intersect but do not fuse. Young parakeets exhibit a brownish iris that gradually turns blue by 60 days of age.

These findings may contribute to the diagnosis of ophthalmic conditions in this species and provide insight into normal anatomical features.