Background: Blepharoptosis can occur at any age. Its surgical correction may be indicated for functional and cosmetic purposes. Blepharoptosis treatment in children <3 years old may be required on an urgent basis to prevent amblyopia. The type of surgery depends on the severity of ptosis. The purpose of the study is to assess the functional results and complications of frontalis sling operation using double-threaded prolene as a suspensory material to correct severe ptosis with minimal or no levator muscle function. Methods: In total, 72 lids of 59 patients (both male and female) having severe unilateral or bilateral ptosis were included. Frontalis sling with double-threaded prolene using cannula for introducing prolene was used to correct severe ptosis in these patients. Patients were followed up for an average of 21 (range: 12-24) months postoperatively for evaluating the functional and cosmetic results as well as possible complications. Results: Favourable long-term functional and cosmetic results were achieved in most patients. The overall recurrence rate of ptosis was in 5 lids, most of which were in <5-year-old patients. Other complications were incomplete closure in 2 lids, overcorrection in 1 lid, and corneal exposure and exposure keratitis in 1 eye. Infection, wound problems, and supratarsal sulcus obliteration were not observed in any case during the follow-up period. Conclusions: Frontalis sling operation using double-threaded prolene as a suspensory material is an effective technique to correct severe ptosis.