Lighting Standards Revisited: Introduction of a Mathematical Model for the Assessment of the Impact of Illuminance on Visual Acuity

Abstract

Purpose: Primary objective of present study is to introduce a contemporary methodology for the lighting standards update addressing both normophakic and pseudophakic patients.

Methods: For the sake of our study, we theoretically estimated the intraocular-to-crystalline lens iIluminance ratio (ICIR) and the intraocular lens (IOL) luminous efficiency function VIOL(λ) as a new lighting benefit metric. Then, in a sample of 24 pseudophakic patients (38 eyes) implanted with the trifocal diffractive IOL Panoptix (SG) and in a control group (CG) of 28 normophakic participants (50 eyes), uncorrected distance visual acuity (UDVA) was measured at illuminance of 550lx (optimal UDVA). Following dark adaptation, illuminance was gradually raised from 20 lx until illuminance level that the patient reached his/her optimal UDVA. This measured illuminance at this point was defined as the minimum required illuminance level (MRIL). MRIL and UDVA for illuminance levels between 20 and 550lx in SG were compared with the corresponding values in CG. MRIL calculation allowed the construction of a predictive mathematical model that estimates the impact of environmental lighting on UDVA.

Results: ICIR for Panoptix eyes ranged from 54.00% to 55.99%. Both groups had significantly higher UDVA at 550lx compared to 20lx (p < 0.05). CG had significantly higher UDVA than SG at 20lx (7.20 letters, p = 0.045), while no significant difference was detected at 550lx (0.40 letters, p = 0.883). SG required significantly more illuminance than CG to maintain their UDVA (MRILSG= 191.05lx, MRILCG= 122lx, p = 0.007). Our predictive model suggests suboptimal UDVA in a series of lighting directives for normophakic and Panoptix eyes.

Conclusion: This is the first study to introduce the VIOL(λ) as a new lighting benefit metric and a mathematical model that quantifies the impact of illuminance on UDVA in normophakic and pseudophakic patients.

Clinicaltrialsgov identifier: NCT04263636.

Keywords: illuminance; light transmission; lighting standards; luminous efficiency function; multifocal intraocular lens.

Conflict of interest statement

The authors report no conflicts of interest in this work.

© 2021 Labiris et al.

Figures

Figure 1

Layout of experimental facility room (dimmable luminaires, illuminance meter, visual acuity chart, lighting control system, etc.).

Figure 2

Illumination distribution according to RELUX simulation tool.

Figure 3

Relative luminous efficiency functions. V(λ) is the original photopic luminous efficiency function. VPanoptix(λ) is the modified photopic luminous efficiency function for pseudophakic eyes implanted with Panoptix IOLs. Vpanoptix(λ) lower values = V(λ) for the lower transmittance values for the distant focal point of Panoptix IOL. Vpanoptix(λ) upper values = V(λ) for the upper transmittance values for the distant focal point of Panoptix IOL.

Figure 4

Τhe spectral transmittance values for the distant focal point of Panoptix IOL in comparison with a 53-year-old crystalline lens. Vpanoptix(λ) lower values = V(λ) for the lower transmittance values for the distant focal point of Panoptix IOL. Vpanoptix(λ) upper values = V(λ) for the upper transmittance values for the distant focal point of Panoptix IOL.

Figure 5

Actual relative spectral radiant flux emitted from the selected light sources.

Figure 6

Percentile UDVA for study and control group at different illuminance levels. . .

Figure 7

Necessary additional illuminance of study group for equal percentile UDVA with control group (xSGeq - x) for different illuminance levels. , where γ = (100–2.4) %.

Figure 8

Additional percentile illuminance (xSGeq - x)/x needed in study group for equal percentile UDVA with control group. , where γ = (100–2.4) %.