Influence Of Eye Axes And Multifocal Intraocular Lens Centration In Photic Phenomena

Photic phenomena (PP) can be defined as bright artifacts perceived by patients along or around direct bright lights or reflected over objects located in the visual field. The percentage of subjects bothered by PP has been reported between 10% and 25% depending on multifocal intraocular lens (MIOL) model and follow-up.  Among factors that affects to PP, it has been hypothesized that eye axes (chord-mu and chord-alpha) can affect to the PP perceived by patients but clinical evidence around this topic is still very limited. The aim of this study was to assess how eye axes and IOL centration (chord-iol) affects to photic phenomena of patients implanted with a trifocal intraocular lens.

Qvision, Ophthalmology Department, VITHAS Almería Hospital, Almería, Spain

58 subjects were monocularly measured during the 3-month follow-up after implantation of either Q-Flex M 640MY (n=47) or Liberty 677MY (n=11) (Medicontur). Eye axes were measured with the Pentacam AXL Wave (Oculus), providing the chord-mu and chord-alpha by the “Cataract Pre Op” display. On the other hand, chord-iol was measured over the “Iris image” display with the caliper option. The objective PP was obtained with the objective scatter index (OSI) provided by the HD Analyzer and the subjective PP with the Light Distortion Index (LDI) measured with the Light Distortion Analyzer. Relationships between axes and PP were assessed with the partial Spearman rho for the magnitude of the axes and after decomposition in cartesian coordinates.

The LDI was 13.34% for the 640MY and 14.64% for the 677MY (p=0.74). Objective (OSI) and subjective (LDI) measurements of PP were directly correlated between them (rho=0.58, p<0.0005). Eye axes were ≤ 1.21 mm for chord-iol, ≤ 0.42 mm for chord-mu and ≤ 0.71 mm for chord-alpha. No significant correlations were found, neither for chord-mu nor for chord-alpha (p>0.05). However, subjective PP decreased with the chord-iol displaced through the temporal location versus the vertex normal (rho=0.32, p=0.02). No relationships were found between OSI and none of the evaluated eye axes.

The mean PP obtained with Q-Flex M 640MY and Liberty 677MY was lower than the cut-off of 15.20% for which subjects usually pass from a slightly bothered to a moderately bothered response to the PP, according to a previous published study of our group and in ESCRS Winter 2022. In opposite as some authors have suggested that the nasal displacement of the IOL is recommended to reduce dysphotopsia, displacement of the MIOL trough temporal location decreases the subjective PP. Despite the known limitations of wavelength of double-pass systems for measuring diffractive MIOLs, a moderate correlation of the OSI with the LDI suggests the possible use of this objective metric for the PP assessment with MIOLs.