Abstract
Purpose:
The zebrafish (Danio rerio) eye shares many similarities with the human eye and is increasingly being used as model for eye development, disease and regeneration. A mutant zebrafish, coined bugeye because of its grossly buphthalmic eyes, has been shown to have some similarities with human glaucoma due to its elevated intraocular pressure (IOP) and optic nerve pathology. We investigated whether a non-invasive clinical tonometer could measure IOP in zebrafish and importantly, distinguish bugeye from wild-type fish.
Methods:
Adult zebrafish were anesthetized in tricaine and placed on a styrofoam bed. A moist paper towel was placed over the fish body, leaving the head and gills exposed. Tricaine solution was perfused over the gills to keep the fish oxygenated and sedated. The fish’s eye was brought up to the probe of a Paradigm blood flow analyzer pneumotonometer and the IOP was repeatedly measured and averaged. The average IOP of several strains of fish were then compared to each other using analysis of variance.
Results:
Bugeye eyes (n=13) were significantly larger compared to TU/TL (n=10) strains both in size and ratio to the head (p=0.006 and 1.6E-06 respectively). The zebrafish quickly recover after IOP measurement, returning to normal activity within minutes of being placed in fresh water. IOP values did not significantly vary in wild-type fish over 12 months of age. Strain AB fish (n=29) had slightly higher IOP values compared to TU/TL, but the difference was not significant. Bugeye mutants had significantly elevated IOP values compared to wild-type fish (bugeye 25.3 mmHg; TU/TL 14.6 mmHg; p=0.01). However, IOP in bugeye zebrafish did not significantly correlate with eye size or eye/head ratios.
Conclusions:
A non-invasive pneumotonometer can be used to measure IOP in adult zebrafish and distinguish bugeye fish from wild-type strains.
Keywords: 568 intraocular pressure