Biochemical markers in the vitreous

Abstract

Abstract Purpose Prealbumin is a 55kDa protein (transthyretin) which plays an important role in the plasma transport of retinol in complex with retinol‐binding protein. It is also synthesized by the retinal pigmentepithelium (RPE) but the functional significance of ocular prealbumin is still unclear. In this study, we wanted to explore the use of prealbumin as a biochemical marker in human vitreous fluid in various conditions. Methods Prealbumin concentration was assayed in vitreous fluid using a BN II nephelometer (Dade Behring). Cadaver eyes (n =59) served as a reference. Vitreous fluid was investigated in 64 patients where therapeutic vitrectomy was indicated: 9 eyes were operated on for retinal detachment less than 1 week old, 25 eyes for longstanding retinal detachment (more than 1 week old), another 13 for proliferative diabetic retinopathy, 17 patients had vitreoretinal retraction at the macula, and in 1 case floaterectomy was performed. Results In the reference group, median prealbumin value was 6.0 mg/l (IQR: 2‐19.8 mg/l); total protein: median 567 mg/l; IQR: 271‐996 mg/l). For patients operated for retinal detachment, prealbumin values were lowest in patients with retinal detachment less than 1 week old (median: 3 mg/l, IQR: 0‐12 mg/l) and highest for patients with longstanding retinal detachment (median: 17 mg/l, IQR: 1‐25 mg/l)(P<0.05). Conclusion Prealbumin is abundant in human vitreous fluid. In pathological conditions, prealbumin values may vary. No correlation was found between prealbumin levels and total protein levels in vitreous fluid. In particular, patients with longstanding retinal detachment showed highest prealbumin values. This might be due to increased synthesis of prealbumin by RPE cells. Prealbumin concentrations in the vitreous may be used as a marker for retinal dysfunction.