AIM: To highlight the importance of microRNA (miRNA)-21-5p in directing the phosphatase and tensin homolog (PTEN) gene to control the phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) pathway in retinal pigment epithelial (RPE) cells in humans subjected to photodamage. METHODS: Human adult RPE cell line-19 (ARPE-19) was cultured in vitro and randomly divided into control, damage, overexpression, negative, and PI3K/Akt blocker groups to establish a photodamage model of ARPE-19 cells. The models were subjected to 24h of light exposure, after which the corresponding indices were detected. The cell counting kit-8 assay quantified cell viability, while flow cytometry determined apoptosis rates. The miRNA-21 mimics and miRNA mimic NC were transfected into ARPE-19 cells using a transient transfection technique. Quantitative reverse transcription polymerase chain reaction (SYBR Green) and Western blotting analyzed expression levels of miRNA-21-5p, PTEN, p-PI3K/PI3K, p-mTOR/mTOR, and p-Akt/Akt. Statistical analyses comprised one-way analysis of variance and the Student-Newman-Keuls test for multiple group comparisons. RESULTS: The photodamage group demonstrated reduced cell survival rates than the control group (P<0.01). The overexpression group exhibited higher cell survival rates than the injury group (P<0.01). The negative group showed no difference in viability (P>0.05). The PI3K/Akt blocker group demonstrated lower cell viability, compared with the overexpression group (P<0.01). CONCLUSION: miRNA-21-5p significantly increases ARPE-19 cell survival after photodamage and inhibits light-induced ARPE-19 cell apoptosis, suggesting that it may play a protective role in RPE by activating the PI3K/Akt/mTOR pathway while downregulating PTEN expression.