Mutant eyes (generated using the "EGUF" system) display morphological defects when larvae are raised on media containing 2 mmol caffeine/L and 3 mmol hydroxyurea/L. Ommatidia are frequently fused and irregularly spaced, with variable numbers of photoreceptors and accessory cells. Indentations are seen in the eye surface. Third instar eye discs have apparently normal morphology and cell cycle patterning. Both drugs contribute the observed developmental defects, though exposure to 2 mmol caffeine/L alone gives a slightly stronger eye phenotype compared to exposure to 3 mmol hydroxyurea/L alone.