Barriers to fluorescein and protein movement

Area of Science:

• Ophthalmology
• Retinal Physiology
• Pharmacokinetics

Background:

• Vitreous fluorophotometry is used to assess the primary blood-retinal barrier.
• The retina has multiple barriers that may differentially affect molecule permeability.

Purpose of the Study:

• To investigate the retinal barrier's permeability to molecules of different sizes.
• To differentiate the barrier properties for small molecules (fluorescein) versus larger ones (proteins).

Main Methods:

• Injected carboxyfluorescein and fluoresceinated dextrans of varying sizes into the subretinal space of rabbit eyes.
• Monitored diffusion and persistence of these molecules within the ocular compartments.

Main Results:

• Carboxyfluorescein rapidly crossed the retina into the vitreous.
• Dextrans comparable in size to proteins showed very poor retinal penetration.
• Large dextrans remained in the subretinal space for days, unlike the injected fluid.

Conclusions:

• The retina presents a more substantial barrier to protein-sized molecules than to fluorescein.
• Vitreous fluorophotometry findings should consider the differential barrier properties of the retina.