Tolerance to light of patients suffering from infectious keratitis

Purpose With very photophobic patients, the advantages of red or near infrared (NIR) light to develop new ophthalmology imaging devices seem obvious: no or little glare, possibility of long signal integration, no phototoxicity, and lesser autofluorescence of ocular tissues. Nevertheless, in this range, the shortest possible wavelength facilitates signal detection. Aim To determine the maximal irradiance tolerated with 6 wavelengths: 2 red, 2 far red and 1 NIR lights in order to determine the shortest wavelength well tolerated by patients, in comparison with the standard cobalt blue light of ophthalmology slit lamp. Methods Study design: interventional, monocentric, single group assignment study on 30 eyes of 30 patients with infectious keratitis after informed consent. Thanks to a customized machine from our laboratory, the photophobic eye was exposed to the 6 lights with increasing intensity. The patients switched off the light when the discomfort was too elevated. The maximal cumulative irradiance possible at 482, 650, 675, 700, 750 and 800 nm were respectively 171, 689, 759, 862, 920 and 889 mW/cm2. Results The maximal cumulative irradiance tolerated increased significantly with wavelength (p