Neuroadaptation: multifocal contact lenses and IOLs

In 2020, 36.9 percent of the world's population was older than 40 years.¹ The expected average age in the industrialised nations for the period from 2025 to 2030 is 80.6 years; for developing countries, the prognosis is 73.7 years, and for the least developed countries 67.6 years.¹  Nevertheless the percentage of wearers of multifocal contact lenses is still relatively low, despite the high number of presbyopes worldwide. Although William Feinbloom was the first to obtain a patent for the production of a bifocal contact lens in 1936,² there are still unanswered questions about the acceptance of simultaneous multifocal systems. This applies equally to multifocal contact lenses and multifocal intraocular lenses. The central question in this context is neuroadaptation, by which we understand the plasticity of the brain during the processing of visual stimuli.³

In principle, simultaneous multi-focal systems usually produce two or more overlapping retinal images and the patient is required to suppress the respective blurred image. This so-called "physiological retouching" or "neuroadaptation" is the essential factor in the acceptance of simultaneous multifocal systems. In clinical practice, optometrists and ophthalmologists therefore inform their patients about this and call adaptation times of up to six months, especially in the area of multifocal intraocular lenses.

The question of the different length of neuroadaptation or even the non-acceptance of simultaneous multifocal systems certainly depends on the respective lens system but also on the individual patient. There has been great progress in this area in recent years due to the variety of new designs in the field of simultaneous lens systems for both contact lenses and IOLs. Nevertheless, the important question of which lens is suitable for which patient has not yet been properly resolved, which is why neuroadaptation is increasingly becoming the focus of many current research activities.⁴

The influence of the quality of binocular vision on the acceptance of multifocal contact lenses and thus also on neuroadaptation was already investigated by Cagnolati in 1993⁵ in his study "Acceptance of different multifocal contact lenses depending on binocular findings". More recent studies on neuroadaptation include Fernandes et al.⁶ and Rosa et al.⁷ with their studies "Short-term delay in neural response with multifocal contact lens might start at the retinal level" and "Functional magnetic resonance imaging to assess neuroadaptation to multifocal intraocular lenses". Providing presbyopic and aphakic patients with multifocal contact lenses or IOLs requires careful and differentiated information about the advantages and disadvantages of each type of treatment. Reliable information regarding a possibly longer adaptation period in connection with the respective therapy method is important for the satisfaction of the patient.

References

[1] Ang, C. (2021). Visualizing the World’s Population by Age Group. https://www.visualcapitalist.com/ the-worlds-population-2020-by-age. Referencing: 11 September 2023.

[2] Toshida, H., Takahashi, K., Sado, K., Kanai, A., Murakami, A. (2008). Bifocal contact lenses: History, types, characteristics, and actual state and problems. Clin. Ophthalmol., 2, 869-877.

[3] Zhang, L., Lin, D., Wang, Y., Chen, W., Xiao, W., Xiang, Y., Zhu, Y., Chen, C., Dong, X., Liu, Y., Chen, W., Lin, H. (2021). Comparison of visual neuroadaptations after multifocal and monofocal intraocular lens implantation. Front. Neurosci., 15, 648863.

[4] Alio, J. L., Pikkel, J. (2019). Multifocal Intraocular Lenses: Neuroadaptation. Multifocal Intraocular Lenses. In: Multifocal Intraocular Lenses (eds. Alio, J. L., Pikkel, J.) Springer Nature.

[5] Cagnolati, W. (1993). Acceptance of different multifocal contact lenses depending on binocular findings. Optom. Vis. Sci., 70, 315-322. 

[6] Fernandes, P., Ferreira, C., Domingues, J., Amorim-de-Sousa, A., Faria-Ribeiro, M., Queirós, A., González-Meijome, J. M. (2022). Short-term delay in neural response with multifocal contact lens might start at the retinal level. Doc. Ophthalmol., 145, 37-51.

[7] Rosa, A. M., Miranda, A. C., Patrício, M. M., McAlinde, C., Silva, F. L., Castelo-Branco, M., Murta, J. N. (2017). Functional magnetic resonance imaging to assess neuroadaptation to multifocal intraocular lenses. J. Cataract Refract. Surg., 43, 1287-1296.