This study is a longitudinal assessment using a classic dose-escalation study design to assess the safety and maximal tolerated dose (MTD) of topical MSC Secretome eye drops. The study will be conducted at Illinois Eye and Ear Infirmary located at University of Illinois at Chicago. The study will use anterior segment Optical Coherence Tomography (OCT)/Scheimpflug Imaging, esthesiometry, and visual analogue scale (VAS) to assess treatment tolerability.

The "Safety of Topical Mesenchymal Stromal Cell Secretome for Ocular Surface Disease" study is designed to evaluate the safety and maximal tolerated dose (MTD) of topical MSC Secretome eye drops in patients with chronic ocular surface disease through a dose-escalation study under a 28-day topical application protocol, and also obtain a preliminary observation on the following:

1. Incidence of treatment emergent adverse events (TEAE) assessed at 28 days following treatment initiation
2. Proportion of patients with improved corneal epithelial barrier at 28 days compared to baseline
3. Final visual acuity, corneal epithelial thickness, corneal stromal haze, corneal sensation, and treatment tolerability

The objective is to determine the dose of MSC Secretome through a first-in-human study through a dose-escalation strategy targeting a toxicity rate of 33% or less.

Inclusion Criteria:

• Patients 18 years of age or older
• Chronic corneal epithelial disease with fluorescein staining score ≥ 6 by NEI grading scale
• Reduced corneal sensation (≤ 4 cm measured by Cochet Bonnet esthesiometry) in at least one corneal quadrant
• A stable ocular surface with no objective clinical evidence of significant (> 50%) improvement/worsening of the epithelial disease in the last 30 days
• Epithelial disease refractory to conventional non-surgical treatments (e.g., preservative-free artificial tears, gels or ointments; discontinuation of preserved topical drops; anti-inflammatory therapy)

Exclusion Criteria:

• Any active or suspected ocular infection (bacterial, viral, fungal or protozoal).
• Evidence of corneal ulceration with stromal loss > 10%
• Presence of an epithelial defect ≥1.0 mm in the largest diameter in the affected eye
• Presence of any size epithelial defect that has been persistent for more than 30 days
• Patients unable to discontinue or intermittently remove therapeutic contact lens in the study eye (to apply drops) during the 4-week study period
• History of any ocular surgery (including laser or refractive surgical procedures) in the affected eye within the 3 months prior to study enrollment
• History of chemical injury within the last 6 months prior to study enrollment Known hypersensitivity to one of the components of the study or procedural medications (e.g.,fluorescein)
• History of drug, medication or alcohol abuse or addiction
• Use of any investigational agent within 4 weeks of screening visit
• History of previous enrollment in the MSC Secretome Study at a lower dose
• Participation in another clinical study at the same time as the present study
• Participants who are pregnant at the time of study enrollment