Gene therapy involves replacing the defective gene with a correct one that is encapsulated within a viral capsid. Once injected, the virus replicates allowing for delivery of the corrected gene. Given that the pathway is different for each genetic mutation, gene therapy is an expensive treatment.
Several clinical trials are underway to treat various inherited retinal diseases through gene therapy. Find more information here https://www.clinicaltrials.gov/ct2/results?cond=&term=gene+therapy&cntry=&state=&city=&dist=
LUXTURNA™ (voretigene neparvovec) is an approved gene therapy for patients with two mutations in a gene called RPE65. Mutations in RPE65 may cause either Leber Congenital Amaurosis or Retinitis Pigmentosa. The drug is administered as an injection under the retina(subretinal injection) following a parsplana vitrectomy. Luxturna is not yet available in India.