Real dynamic assessment of tear film optical quality for monitoring and early prevention of dry eye

Abstract

To evaluate real dynamic assessment of tear film optical quality for monitoring and prevention of dry eye.Right eyes of 62 normal and 39 dry eye subjects were included. Dynamic measurement of objective scatter index (OSI) was performed by using the Optical Quality Analysis System II (OQAS II), correlation coefficient between OSI and time (CCOT) was calculated. According to whether the CCOT was significantly ascending, normal and dry eye groups were further subdivided for comparison. By using Scheimpflug-Placido topographer, non-invasive tear break-up time (NITBUT) was recorded, and a 2-dimensional precorneal tear film map was reconstructed and divided into central, middle, and peripheral corneal zones, distribution of tear break-up spots in the 3 corneal zones were analyzed.The numbers of tear break-up spots were higher in all the 3 corneal zones of the dry eye subjects (P < .01), when compared with the normal subjects. The Dry Eye subjects with ascending CCOT had the shortest NITBUT (P < .001-.034) and the most tear break-up spots over the whole cornea (P < .001-.044). Between the dry eye subjects with non-ascending CCOT and those with ascending CCOT, difference of tear break-up spots was found significant only in the peripheral corneal zone (P < .01).Non-ascending and ascending CCOT of dry eye patients reflect different stability of tear film. Real dynamic assessment of tear film optical quality is potential for monitoring and early prevention of dry eye.

Figure 1

An example for the measurement of tear film optical quality dynamics. As the measurement started, subjects were advised to naturally blink twice and then keep their eyes open for at least 10 seconds. Serial double-pass retinal images of a point source and their corresponding OSIs were recorded automatically, in the interval of 0.5 second. CCOT was calculated from the OSI fluctuation in these 10 seconds right after the blinking. CCOT = coefficient between OSI and time, OSI = objective scatter index.

Figure 2

A Placido disc pattern composed of 22 white and black rings was projected onto the cornea. The locations and times of tear break-up spots were reconstructed into a 2-dimensional precorneal tear film map, which was divided into central (the central ring 1 to ring 7), middle (ring 8 to ring 15), and peripheral (ring 16 to ring 22) zones.

Figure 3

The frequencies with ascending correlation coefficient between OSI and time (CCOT) in the normal and the dry eye groups were very close (P = .956). OSI = objective scatter index.

Figure 4

The correlation coefficient between OSI and time (CCOT) (top left), ocular surface disease index (OSDI) (top right), non-invasive tear break-up time (NITBUT) (bottom left), and Schirmer test (bottom right) were compared between Normal/NA versus Normal/A, Dry Eye/NA versus Dry Eye/A, Normal/NA versus Dry Eye/NA, Normal/A versus Dry Eye/A subgroups. /NA, /non-ascending; /A, ascending. ^∗P value < .05; ^∗∗∗P value < .001. OSI = objective scatter index.

Figure 5

The distribution of tear break-up spots in central (top left), middle (top right), peripheral (bottom left) corneal zones, and the total tear break-up spots on the whole cornea (bottom right) were compared between Normal/NA versus Normal/A, Dry Eye/NA versus Dry Eye/A, Normal/NA versus Dry Eye/NA, Normal/A versus Dry Eye/A subgroups. /NA, /non-ascending; /A, ascending. ^∗P value < .05; ^∗∗P value < .01.