Eye of adults are slightly rough and slightly smaller than those of wild type. The macrochaetae of the notum are missing. Ommatidia have one or more extra photoreceptor cells which may be of any of the inner or outer photoreceptor cell types. This phenotype is seen when heterozygous with stg^Dr-mr21, stg^Dr-FA30, stg^AR2 or stg^RXT13 or Df(3R)Ptp99A^R3. When stg^hwy is heterozygous with stg⁴ or stg² there is no ommatidial phenotype, though bristle defects are still evident. The pattern and number of S phase cells in the third instar eye disc is unaffected. The number of mitotic cells anterior to the furrow is reduced. Overall there is a two-fold reduction in the number of mitotic cells in the anterior eye disc compared to wild type. Cells are in G₂ arrest. Despite this, pattern formation in the eye disc proceeds normally, though later in development extra cone cells are evident.

Homozygotes have bristle and eye defects. Eye discs contain ectopic photoreceptors that are predominantly of the R2/R5 type.