It has been recommended that patients on hydroxychloroquine be monitored regularly for retinopathy. However, there has not been an agreement as to the best screening test for hydroxychloroquine toxicity, which may include visual fields (VF), fundus autofluorescence, spectral domain optical coherence tomography (SD-OCT) and multifocal electroretinography. The authors report on a retrospective study of patients with hydroxychloroquine toxicity over a 20-year period. There were 150 patients who had toxicity, defined as clear parafoveal scotomas between two and six degrees on 10-2 VFs or clear parafoveal thinning and damage on SD-OCT. Eleven patients had relatively complete ring scotomas on VFs despite seemingly normal SD-OCT. However, all other patients with clear parafoveal damage on SD-OCT demonstrated some focal areas of parafoveal VF loss. This indicates that up to 10% of patients with hydroxychloroquine toxicity can manifest prominent ring scotomas first before any abnormality is seen on SD-OCT. The results from this study suggest that screening for hydroxychloroquine toxicity should include both 10-2 VF testing and SD-OCT to provide the optimum specificity and sensitivity.