POEM-F for Achalasia International Study

Inclusion criteria: 1. Adult patient (age ≥18 and ≤65 years-old) and with symptomatic achalasia type I or II. 2. Capability of understanding and complying with the study requirements, including filling the Eckardt Score, GERD-HRQL and RSI questionnaire and signing the informed consent form. 3. Patients with achalasia type I, II or III who are one of the following: * Treatment naïve, or * Failed prior through-the-scope balloon dilation, Savary or pneumatic dilation Exclusion criteria: 1. Patients unable or unwilling to provide consent. 2. Previous esophageal or gastric surgery. 3. Prior achalasia treatment including Heller myotomy, POEM. 4. Sigmoid achalasia, or significant esophageal dilatation \>6cm in lower esophagus 5. Disrupted mucosal integrity at the distal esophagus, eg. Ulcer, fibrotic scars etc 6. Patients with large hiatal hernias (axial length \> 2 cm and Hill grade \>2). 7. Patients with significant cardiorespiratory comorbidities which may limit their ability to undertake general anesthesia for the procedure, including ASA grade III or above. 8. Patients with obesity (Body Mass Index (BMI) ≥ 30). 9. Pregnant women or those planning pregnancy or breastfeeding women. 10. Uncorrectable coagulopathy defined by international normalized ratio (INR) \> 1.5 or platelet count \< 50000/µl.