Colour vision changes in patients with pressure differences across the lamina cribrosa

The retinal nerve fibre layer (RNFL) thickness parameters describe the integrity of retinal ganglion cells (RGC) and their axons and can be affected in pathological processes involving the optic nerve. Glaucoma and papilledema are two conditions where RGCs and hence RNFL, are damaged due to the pressure differences across the lamina cribrosa. The latter separates the intraocular and intracranial pressure compartments. In glaucoma, the intraocular pressure (IOP) is elevated and in papilledema, the intracranial pressure is elevated. When intracranial pressure is managed, papilledema patients can recover without significant loss of RGC. Conversely irreversible RGC loss can occur in severe cases. Subtle, functional changes that are often not detected clinically can remain following recovery. The detection of such changes require sensitive functional tests and a knowledge of normal age limits for the stimulus attribute investigated. Results of preliminary studies designed to assess how colour vision and rod and cone mediated flicker sensitivity recover in papilledema will be reported for a number of patients. Following recovery, the results often reveal binocular summation effects, even when the differences between the two eyes remain significant. Patients classed clinically as fully recovered continue to show small differences between the two eyes, even when the measured binocular thresholds are within the expected age limits. In summary, the preliminary findings from this investigation show how various attributes of vision are affected during the early stages of the disease and after treatment and recovery from late stage of severe papilledema with loss of RGCs.