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Although there is evidence for myopia being related to near-work, the question remains how reading possibly promotes the eye’s elongation. One might think that it is trivial whether we read dark text on a bright background or the opposite contrast with bright letters on a darker ground; however, eyes react differently depending on which contrast polarity we use.

Our visual system is segregated into an OFF and an ON pathway to efficiently signal information about luminance increments and decrements. Research in animals revealed that the selective activation of these pathways interferes with refractive error development, and that a defect in the ON pathway is associated with myopia.^1-4 In humans, recent work found that the retinal OFF pathway is predominantly stimulated during reading of standard contrast text, resulting in a significant thinning of the choroid.⁵

Inverted contrast text, on the other hand, stimulates the ON pathway and leads to thicker choroids, which are assumed to be protective against myopia development.⁵ The OFF stimulation was found to be even enhanced when reading black-on-white text at close distances.⁶ This is of concern since thinner choroids are linked to myopia onset, and children are constantly exposed to this type of stimulation during their school days and leisure time.

In a previous investigation, we found that the ciliary muscle, which is the main player during accommodation, surprisingly becomes thinner after 30 minutes of reading black text on a white background at a close distance.⁷Repeating this experiment with a subgroup using the opposite contrast revealed that myopic eyes again reacted with a thinning of their ciliary muscle, while emmetropic ones became rather thicker. This might indicate that the text contrast is only of importance to the ciliary muscle structure prior to myopia development.⁸ Interestingly, we recently showed that the accommodation and pupil responses are not influenced by the text contrast polarity (with the same luminance) in either refractive group.⁹

Do the retinal responses in myopic eyes differ from that of emmetropes when reading with standard or inverted contrast? To answer this question, we designed a stimulus to selectively activate the ON or OFF pathway during electroretinography. Indeed, our first results show that the retina reacts differently to inverted and standard contrast conditions of the same mean luminance depending on the refractive error of the eye and the area of the retina stimulated.¹⁰

With our ongoing research,¹¹ we not only aim to gain a better understanding of the differences between the retinal processing in a myopic compared to an emmetropic eye, including the retinal activity to various stimuli during near-work. Ultimately, we also intend to develop a stimulus that maximally activates the ON pathway to possibly contribute to improved myopia management therapies for children.

1. Pardue MT, Faukler AE, Fernandes A, et al. High susceptibility to experimental myopia in a mouse model with a retinal on pathway defect. Invest Ophthalmol Vis Sci. 2008 Feb;49:706-712.

2. Crewther SG, Crewther DP. Inhibition of retinal ON/OFF systems differentially affects refractive compensation to defocus. Neuroreport. 20023 Jul 1;14:1233-1237.

3. Crewther DP, Crewther SG. Refractive compensation to optical defocus depends on the temporal profile of luminance modulation of the environment. Neuroreport. 2002 Jun 12;13:1029-1032.

4. Chakraborty R, Park HN, Hanif AM, Sidhu CS, Iuvone PM, Pardue MT. ON pathway mutations increase susceptibility to form-deprivation myopia. Exp Eye Res. 2015 Aug;137:79-83.

5. Aleman AC, Wang M, Schaeffel F. Reading and myopia: contrast polarity matters. Sci Rep. 2018 Jul 18;8:1-8.

6. Hoseini-Yazdi H, Read SA, Alonso-Caneiro D, Collins MJ. Retinal OFF-Pathway Overstimulation Leads to Greater Accommodation- Induced Choroidal Thinning. Invest Ophthalmol Vis Sci. 2021 Oct 4;62:1-12.

7. Wagner S, Schaeffel F, Zrenner E, Straßer T. Prolonged nearwork affects the ciliary muscle morphology. Exp Eye Res. 2019 Sep;186:107741.

8. Wagner S, Strasser T. Does reading text with inverted contrast affect the ciliary muscle structure of emmetropic and myopic eyes? Invest Ophthalmol Vis Sci. 2022 Jun;63:1450-F0408.

9. Wagner S, Wichmann T, Strassert T. Are Effects of Retinal ON/OFF Pathway Stimulation Influenced by Accommodation and Pupil Responses during Reading Task? Abstract from the 2023 American Academy of Optometry Meeting, New Orleans. Available at https://aaopt.org/past-meeting-abstract-archives/?SortBy=ArticleAuthor&ArticleType=&ArticleYear=&Title=Effects+of+retinal&Abstract=&Authors=&Affiliation=&PROGRAMNUMBER=. Accessed Nov. 13, 2023.

10. Wagner S, Strasser T. Impact of text contrast polarity on the retinal activity in myopes and emmetropes using modified pattern ERG. Sci Rep. 2023 Jul 9;13:11101.

11. Wagner S, Settele A, Strasser T. ERG Responses of Emmetropes vs. Myopes to Selective ON/OFF Pathway Activation Using a Novel Stimulus. Abstract from the 2023 American Academy of Optometry Meeting, New Orleans. Available at https://aaopt.org/past-meeting-abstract-archives/?SortBy=ArticleAuthor&ArticleType=&ArticleYear=&Title=ERG+REsponses&Abstract=&Authors=&Affiliation=&PROGRAMNUMBER=. Accessed Nov. 13, 2023.