Validation of Alternative Methods for Detecting Meibomian Gland Dropout Without an Infrared Light System: Red Filter for Simple and Effective Meibography

Abstract

Purpose: To evaluate the validity and reliability of alternative methods for evaluating meibomian gland (MG) dropout without using an infrared light system: red-filtered or isolated red-channel images (RCIs) of the everted eyelid.

Methods: We evaluated MG dropout in the everted upper and lower eyelids of 125 eyes of 64 patients with good-quality infrared meibography images (IMIs) and color digital photographs with and without a red filter. Red-filtered images (RFIs) were converted to black and white and adjusted for contrast/brightness [adjusted red-filtered images (aRFIs)]. RCIs were computationally isolated from color digital photographs obtained without a red filter. After randomization, the total meiboscore (0-6) was evaluated by 2 independent evaluators (interobserver reliability) masked to the image origin, and again after a 30-day interval (intraobserver reliability).

Results: The meiboscores evaluated using the RFI, aRFI, and RCI were strongly positively correlated with those evaluated using the IMI (RFI: ρ = 0.788; aRFI: ρ = 0.735; RCI: ρ = 0.630; all P < 0.001, Spearman correlation analysis). Linear-weighted κ-values (κw) showed substantial agreement between the RFI and IMI (κw = 0.676, 95% CI = 0.594-0.759). The RFI had substantial intraobserver reliability (κw = 0.735, 95% CI = 0.685-0.785) and moderate interobserver reliability (κw = 0.467, 95% CI = 0.371-0.563). Computational adjustment of RFIs did not enhance the validity or reliability, and RCIs had limitations in some cases.

Conclusions: MGs were successfully visualized using a red filter on a slit lamp and showed substantial agreement with visualization using the standard infrared method. Although interobserver reliability was only moderate, this alternative technique may be useful for evaluating MG dropout when an infrared meibography device is not available.

FIGURE 1.

Anterior segment color digital photographs of the eyelids with or without the red filter. In the upper (A and B) and lower (C and D) eyelids of the right eye of a 23-year-old female patient, the MGs can be visualized by simply inserting a red filter in front of the objective lens of the slit lamp (B and D). In the lower (E and F) eyelid of the right eye of a 53-year-old male patient, the MGs showed dropout in the nasal half.

FIGURE 2.

Four sets of images of the tarsal conjunctiva and the underlying tarsus containing MGs. A–E, Images of the right eye of a 26-year-old female patient show intact MGs. F–J, Images of the left eye of a 56-year-old male patient show impaired MGs. A and F, Images of color photographs. B and G, Images of infrared meibography. C and H, Images acquired through a red filter. D and I, Brightness/contrast-adjusted images acquired through a red filter. E and J, Red-channel images of color photographs.

FIGURE 3.

Correlation plots of the meiboscores and histograms for the grade differences. A–C, Correlation plots of the meiboscores evaluated by the new methods compared with the standard infrared method. D–F, Histograms for the grade differences between the new methods and the standard infrared method. A and D, Comparison between images acquired through a red filter and the standard method. B and E, Comparison between brightness/contrast-adjusted images acquired through a red filter and the standard method. C and F, Comparison between the red-channel of the color photograph and the standard method. Numbers in parentheses represent the number of observations; ρ, Spearman rank correlation coefficient rho; τ, Kendall rank correlation coefficient tau b; *P < 0.001.

FIGURE 4.

Limitation of the RCIs in some cases. A and B, Images of the lower eyelid of the left eye of a 40-year-old female patient show (A) intact MGs with an indistinguishable area due to the bright reflection in the RCI (arrows). B, The outline of the MGs is more distinguishable in the same area of the RFI (arrowheads). C, The MGs are not quite distinguishable from the RCI of the upper eyelid of the left eye in a 75-year-old female patient. D, Although difficult, the MGs can be distinguished in the RFI of the same eyelid with careful evaluation (empty arrows) and may be easier when viewed live. Evaluation is usually more difficult in the upper eyelid of older patients.