Abstract
Background:
The designs of custom ocular occluders vary widely and may introduce heterogeneity in biological outcomes. Retinal dopamine D₁ receptor (D₁R) signaling is thought to exert a protective role and reduce dopaminergic activity in rabbit retina.

Aim:
The aim of this study was to prove the reduction in D1R concentration in rabbit eyes after the eye occlusion process for 30 days.

Methods:
A low-cost, opaque monocular occluder was developed by repurposing black plastic bottle caps cushioned with adhesive bandage tape. The occluder was applied to the right eye of 2 to 3-month-old male New Zealand White rabbits for 30 days, with the left eye serving as an unoccluded control. The devices were replaced every 3 days under minimal lighting. At the end of the occlusion period, rabbits were euthanized, their eyes were enucleated, and retinal/vitreal tissues were collected. D₁R concentrations were quantified using enzyme-linked immunosorbent assay.

Results:
The bottle-cap occluder was well tolerated; no clinical signs of conjunctivitis, corneal opacity, discharge, eyelid edema, or orbital cellulitis were observed. Retinal/vitreal D₁R levels were consistently lower in occluded eyes than in fellow eyes. In Rabbit 1, D₁R concentrations were 0.41 ng/mL in the left (unoccluded) eye and 0.26 ng/mL in the right (occluded) eye; in Rabbit 2, D1R concentrations were 2.82 ng/mL and 1.95 ng/mL, respectively.

Conclusion:
This pilot study suggests that a simple black bottle-cap–based eye occluder can be safely used in rabbits and is associated with reduced retinal D₁R levels supporting its utility as a low-cost tool for experimental dopamine research.

Key words: Dopamine; Rabbit; Eye occluder; Experimental model; Sustainable laboratory practice.