Erythropoietin (EPO) is a glycoprotein hormone conventionally thought to be responsible only in producing red blood cells in our body. However, with the discovery of the presence of EPO and EPO receptors in the retinal layers, the EPO seems to have physiological roles in the eye. In this review, we revisit the role of EPO in the eye. We look into the biological role of EPO in the development of the eye and the physiologic roles that it has. Apart from that, we seek to understand the mechanisms and pathways of EPO that contributes to the therapeutic and pathological conditions of the various ocular disorders such as diabetic retinopathy, retinopathy of prematurity, glaucoma, age-related macular degeneration, optic neuritis, and retinal detachment. With these understandings, we discuss the clinical applications of EPO for treatment of ocular disorders, modes of administration, EPO formulations, current clinical trials, and its future directions.
The majority of patients with dysthyroid eye disease have an acquired colour vision defect. However, no psychophysical investigation of selective damage to colour or flicker pathways has been carried out. In order to clarify the nature of the visual pathology, we have used a psychophysical technique (spectral sensitivity) to selectively stimulate the chromatic and achromatic mechanisms. Spectral spots of size 1 degree presented at a rate of 1 Hz on a bright 1000 td white background are detected by the chromatic mechanism but a rate of 25 Hz reveals the achromatic mechanism. Fifteen patients (28 eyes) between the ages of 50-70 years were tested. The study showed that all patients had reduced spectral sensitivity, either 1 Hz, 25 Hz or both. The patients with reduced 1 Hz or 25 Hz spectral sensitivity only had a shorter systemic and ocular duration of the condition, had no proptosis, normal intraocular pressures in primary gaze, slightly higher intraocular pressures on upgaze, normal visual field plots and FM 100-Hue error scores higher than the normal age-matched values. The patients with reduced both 1 Hz and 25 Hz spectral sensitivities had a longer systemic and ocular duration of the condition, had proptosis, normal intraocular pressures in primary position, higher intraocular pressures on upgaze and higher FM 100-Hue error scores than the age-matched normals and those in Groups 1 and 2. A total of 50% of patients in Group 3 had defective visual field plots. These data suggest that there is a damage of the large achromatic fibres and small chromatic fibres in dysthyroid eye disease. The mechanism of the damage could be one of ischaemic or mechanical or both.