If you use a CPAP machine then you likely have experienced 'CPAP dry eye'. The common symptomology is patients with scratchy, irritated eyes on waking if mask fit is not perfect or a nighttime shift occurs.
CPAP dry eye is not a real 'diagnosis'... but certainly is a common clinical observation.
Both are non-preserved and when used just before bed, prevent much of the overnight evaporation that causes the morning discomfort and redness.
Both gels (I-Defence less) cause some blurred vision so only evening use is recommended.
Learn more about these products on mEYEspa