This study examined conjunctival microvasculature development in long-term habitual contact lens (HCL) wearers after a night of sleep.
Twenty HCL wearers (15 women and 5 men, aged 28.6±6.9 years, mean age±standard deviation) who had worn contact lenses on a daily basis for at least 3 years and 40 noncontact lens (NCL) wearers (23 women and 17 men, aged 36.5±6.6 years, mean age±standard deviation) participated in the study. A functional slitlamp biomicroscopy
imaging system was used to image the temporal bulbar conjunctiva
. Imaging was performed in the morning while the contact lens wearers were not wearing their lenses after a night of sleep. The conjunctival vessel diameters, blood flow velocities, and flow rates were measured. In addition, fractal analyses were performed to obtain the vessel network density (Dbox
) and complexity (D0
The average blood flow velocity
in HCL wearers after a night of sleep was 0.59±0.19 mm/s, which was significantly higher than that in NCL wearers (0.48±0.17 mm/s, P
<0.05). The microvessel network density and complexity levels (Dbox
=1.64±0.05 and D0
=1.71±0.05, respectively) in the HCL wearers were significantly higher than those in NCL wearers (Dbox
=1.61±0.05 and D0
=1.69±0.04, both P
<0.05). The blood flow velocity
was positively correlated with the duration of contact lens wear (r
<0.05) and with the daily number of lens-wearing hours (r
<0.05) in HCL wearers.
This study identified microvascular alterations in the conjunctiva in response to daily contact lens wear after a night of sleep in long-term daily contact lens wearers. The unrecovered changes may indicate that para-inflammation occurs on ocular surfaces because of contact lens wear and that overnight sleeping with no lenses may not sufficiently restore the ocular surface to an intact state.