Retinal drug toxicity in the absence of visible fundus changes

A variety of systemic medications cause retinal drug toxicity associated with characteristic ophthalmoscopic changes e.g. pigmentary retinopathies, crystalline retinopathies, retinal vasculopathies, or retinopathies associated with macula edema. However, altered retinal function can occur in the absence of visible fundus changes. For example, the cardiac glycosides, digoxin and digitoxin, are frequently associated with disturbances of colour vision mediated through the inhibition of sodium‐potassium ATPase. Similarly, phosphodiesterase inhibitors such as sildenafil can also act on the photoreceptor transduction cascade to cause reversible changes in colour perception, blurred vision and increased glare sensitivity. Exposure to antiepileptic drugs that modulate GABA, can also lead to altered visual function. The most significant adverse reaction occurs with vigabatrin which can cause irreversible concentric visual field loss in susceptible individuals. It is important for eye care professionals to be aware of the potential for adverse reactions associated with systemic drugs and consider the use of functional vision tests for their detection and monitoring.