Purpose
To investigate the impact on human conjunctival goblet cell (GC) survival and mucin release for benzalkonium chloride (BAK) preserved and preservative-free (PF) 0.005% (w/v) latanoprost (LT) eye drops, and to compare the eye drops’ physicochemical properties.

Methods
GC cultures were established from human conjunctival donor tissue. The impact of eye drops on GC survival was assessed using lactate dehydrogenase (LDH) and tetrazolium dye (MTT) colorimetric assays. Mucin release was evaluated through mucin-specific immunostaining. pH-value, osmolality, drop mass and surface tension for all LT eye drops were measured.

Results
After application with PF-LT for 30 minutes (min), the GC survival was maintained (p = 0.7043), while all BAK-LT eye drops reduced survival to approximately 70% (p<0.0001). Following application with PF-LT for 30 min, mucin was found around the GC nucleus, as seen in the vehicle control, indicating no secretion. In contrast, BAK-LT caused diffuse staining of mucin, similar to the secretagogue histamine, indicating stimulation of secretion. The pH of the BAK-LT and PF-LT eye drops were 6.0-6.9 and 6.8, respectively. The osmolality was 258-288 mOsm/kg for the BAK-LT eye drops and 276 for PF-LT eye drop. The mean drop mass was 26-31 mg for the BAK-LT eye drops and 30mg for PF-LT. The surface tension was lower for all BAK-LT eye drops (31.1-32.1 mN/m) compared to PF-LT (42 mN/m).

Conclusions
PF-LT compared to various branded and generic LT preparations containing BAK should be used to improve goblet cell tolerability and ocular surface health.