LED Light Characteristics for Surgical Shadowless Lamps and Surgical Loupes

Abstract

Background: Blue light has more energy than longer wavelength light and can penetrate the eye to reach the retina. When surgeons use magnifying loupes under intensive surgical shadowless lamps for better view of the surgical field, the total luminance is about 200 times brighter than that of typical office lighting. In this study, the effects of 2 types of shadowless lamps were compared. Moreover, the effect of various eyeglasses, which support magnifying loupes, on both the light energy and color rendering was considered.

Methods: The light intensity and color rendering were measured on 3 variables: light transmittance, light intensity, and color rendering.

Results: Under shadowless lamps, the light energy increased with low-magnification loupes and decreased with high-magnification loupes. Filtering eyeglasses reduced the energy, especially in conditions where the low-magnification loupe was used. The best color-rendering index values were obtained with computer eyeglasses under conventional light-emitting diode shadowless lamps and with no glass and with lightly yellow-tinted lenses under less-blue light-emitting diode.

Conclusions: Microsurgeons are exposed to strong lighting throughout their career, and proper color rendering must be considered for easier recognition. Light toxicity and loss of color rendering can be reduced with an appropriate combination of shadowless lamps and colored eyeglasses.

Fig. 1.

A eyeglass sample used in this investigation: original eyeglasses with clear lenses (glass #1).

Fig. 2.

Four more eyeglass samples used in this investigation (A) blue-light reduction eyeglasses sold as PC eyeglasses (glass #2), (B) light yellow-tinted eyeglasses (glass #3), (C) dark yellow-tinted eyeglass (glass #4), and (D) conventional dark-tinted sunglasses (glass #5).

Fig. 3.

The relative light transmittance curve (in %) for the 5 eyeglass samples: glasses #1–#5 (A–E, respectively). The lens spectrum curves were obtained from JIN Co., Ltd. Each curve indicates a large difference in the transmittance and in the blue-light cut rate.

Fig. 4.

Part I of the light intensity data (A) without the magnifying loupe, (B) with the low-magnification surgical loupe, and (C) with the high-magnification surgical loupe. C, CRYSTAL; S, SKYLED.

Fig. 5.

Part II of the light intensity data for (A) the CRYSTAL surgical lamp with and without glasses (C + #1, 2, 3, 4, or 5), (B) the CRYSTAL surgical lamp and the low-magnification loupe with and without glasses (C + L + #1, 2, 3, 4, or 5), (C) SKYLED with and without glasses (S + #1, 2, 3, 4, or 5), and (D) SKYLED and the low-magnification loupe with and without glasses (S + L + #1, 2, 3, 4, or 5).

Fig. 6.

The integral area of the high-magnification loupe groups is far lower than that from the other groups (no loupe and low-magnification loupe) (A). Therefore, in the following examinations, we only examined the no-loupe (B and C) and low-magnification groups (D and E). Compared with no-loupe groups B and C, low-magnification loupe groups D and E showed a sharp decrease between the no-glass and with-glass groups.

Fig. 7.

The color-rendering index for (A) the CRYSTAL surgical lamp with and without glasses (C + #1, 2, 3, 4, or 5), (B) the CRYSTAL surgical lamp and the low-magnification loupe with and without glasses (C + L + #1, 2, 3, 4, or 5), (C) SKYLED with and without glasses (S + #1, 2, 3, 4, or 5), and (D) SKYLED and the low-magnification loupe with and without glasses (S + L + #1, 2, 3, 4, or 5).