Contact lens discomfort associated with bulbar conjunctival microvascular alternations

Abstract

 

Purpose

 

To determine the relationship between contact lens discomfort and conjunctival microvascular alternations imaged with functional slit-lamp biomicroscopy (FSLB).

 

Methods

 

FSLB was used to create non invasive microvascular perfusion maps (nMPMs) and measure hemodyanmics. A large field of view on the temporal conjunctiva were obtained for creating nMPMs. Fractal analyses were performed to quantify the nMPMs (Fig. 1). A high speed video recording and a high magnification were achieved for imaging hemodyanmics. Custom software was developed to segment conjunctival nMPMs for fractal analysis and measure blood vessel diameter, blood flow velocity and flow rate. Five registered vessels were imaged for microcirculation. Ten subjects were imaged every 2 hours from 9 am to 5 pm at one visit. The coefficient of repeatability (CoR) of the tests was analyzed using the first two time points. At another visit, one eye of each subject wore a PureVision lens for 6 hours. Imaging was performed at baseline, 0.5, 1, 2, 4 and 6 hours of wearing the lens.

 

Results

 

There were no significant diurnal variations in vessel diameter, blood flow velocity, flow rate and fractal dimensions over the test period, although fluctuations occurred (P > 0.05). The CoRs of these measurements were within 13%, except for the flow rate (33%). For the lens group, significant increases of all measured vascular parameters were found (P < 0.05) after lens wear. Ocular discomfort related to all vascular parameters (r ranged from 0.84 to 0.99, P < 0.05). The highest correlation was found between discomfort and the vessel width (0.99).

 

Conclusions

 

Contact lens discomfort strongly related to microvascular network’s fractality and hemodyanmics of the human conjunctiva, which can be measured easily and reliably using FSLB.

 

 

Figure 1: Frame-captured images of the bulbar conjunctival microcirculation (magnification = 210×) were obtained in a normal subject before (A) and after 6 hours of wearing a contact lens. Clusters of the red blood cells are clearly visible. The temporal conjunctiva of another subject was imaged (magnification = 22×, C to E). The microvascular network of the bulbar conjunctiva was clearly visualized in the raw image (C), segmented vessel network (D) and skeletonized vessel network (E). The cropped area was 7.87×7.87 mm2 in the temporal conjunctiva 1 mm away from the limbus.

 

Keywords: 477 contact lens • 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • 749 vascular occlusion/vascular occlusive disease