A Phase 1/2 Crossover Study to Assess EXP039 for Myopia or Hyperopia

Inclusion Criteria: 1. Age ≥18 to ≤80 years 2. Participants must be in good general health, with no significant medical problems that, in the opinion of the investigator, would preclude participation in the trial, at Screening and/or before administration of the dose of study drug 3. Low-to-moderate hyperopia (SER of +0.50D to +2.00D) or myopia (SER of -0.50 D to -4.00D) at Screening 4. Between-eye SER difference of no more than 0.50D 5. Best-corrected distance visual acuity better than or equal to 20/20 in both eyes at Screening 6. Astigmatism in each eye of less than or equal to 0.75D with manifest refraction at Screening 7. Women of childbearing potential (WOCBP) must have a negative urine pregnancy test at Screening 8. WOCBP must be non-pregnant and non-lactating, and must use a medically approved, highly effective contraception method from Screening until study completion, including the follow up period. Female participants who are in same sex relationships are not required to use contraception.Males must be surgically sterile (\>30 days since vasectomy with no viable sperm), abstinent, or if engaged in sexual relations with a WOCBP, the participant and his partner must use a medically approved, highly effective contraceptive method from Screening until study completion, including the follow-up period. 9. Males must not donate sperm for at least 90 days after the last dose of study drug 10. Participants must have the ability and willingness to attend the necessary visits 11. Participants must be willing and able to provide written informed consent after the nature of the study has been explained and prior to the commencement of any study procedures. Exclusion Criteria: 1. Any central corneal abnormality (e.g., keratoconus, Pellucid marginal degeneration, corneal scar, Fuchs' endothelial dystrophy, guttata, or edema) in either eye that is likely to interfere with visual acuity 2. Moderate or severe dry eye as defined by corneal fluorescein staining score of ≥3 on Oxford scale at Screening 3. Any clinically significant pupillary or iris abnormality (e.g., anisocoria of \>1 mm between eyes at Screening or baseline, abnormal pupil shape in either eye, iris transillumination defects, or any congenital or traumatic defect of the iris) 4. Narrow iridocorneal angles (Shaffer grade ≤2 or lower on gonioscopy examination), history of angle-closure glaucoma, or previous iridotomy 5. Intraocular pressure (IOP) \<8 mmHg or \>23 mmHg in either eye or history of glaucoma or ocular hypertension 6. Any clinically significant abnormal lens finding (e.g., cataract, loose zonules, exfoliation, pseudoexfoliation) 7. History of any intraocular surgery including cataract surgery or phakic intraocular lens surgery 8. History in either eye of previous corneal inlay, full- or partial-thickness corneal transplant, radial keratotomy or any corneal surgery including laser-based corneal refractive surgery 9. Any clinically significant abnormal finding on dilated fundus examination in either eye or known history of retinal detachment, retinal trauma, retinal or vitreal surgery, or clinically significant retinal disease in either eye 10. Clinically significant strabismus or diplopia 11. History of stereo vision difficulties 12. History of optic neuropathy or amblyopia in either eye 13. Use of orthokeratology contact lenses within the past 1 month prior to EXP039 dosing on Day 1 14. Use of temporary or permanent punctal plugs or history of punctal cautery in one or both eyes 15. Planned use of any contact lenses during the study 16. Allergy to pilocarpine or any of its excipients 17. Serious systemic illness that, in the opinion of the Investigator's, would render the participant ineligible 18. Pre-planned hospitalization or ocular or systemic surgery during the study period 19. History of any substance abuse (alcohol and/or illegal drugs) and not willing to abstain from drug(s) and reasonably limit alcohol consumption to approximately 2 alcoholic beverages per day during the 30-day study period 20. Participation in any other study of investigational therapy during the study period or within the last 30 days or 5 half-lives, whichever is longer 21. Unwilling or unable to complete study procedures or to be followed up for the duration of the study