Introduction

Quantum biology is the application of quantum theory to describe aspects of biology that are insufficiently described by classical laws of physics. This field involves the study of how light interacts with biological systems. Prior to the 20th century, physics and biology rarely intersected and biological systems were thought to be too complex to be represented using mathematical methods [1]. However, in present-day ophthalmology, the use of physics is essential, from the use of lasers to correct errors in refraction [2], to using a stream of air to measure intra-ocular pressure [3]. The visual pathway is fundamentally quantum mechanical in nature, involving electron transfer and energy transfer based on surface hopping [4]. Currently, the usage of quantum biology in ophthalmology remains an alien concept to most ophthalmologists and ophthalmic researchers. In the same way that emerging technologies such as virtual reality (VR) [5,6,7] and artificial intelligence (AI) [8,9,10] were rapidly integrated into ophthalmology to benefit patients, quantum biology can be a key future area of research to provide novel diagnostics and treatments. Further research in quantum biology can potentially lead to the development of non-invasive ophthalmic therapeutic devices and new drugs to heal the eye.

Since the early 20th century, the field of quantum biology has evolved significantly and quantum phenomena such as quantum coherence and tunnelling are now widely accepted as being involved in vital processes for enzyme action and energy transfer for every living cell [11]. Recent evidence has shown that light-harvesting systems such as photoreceptors, have evolved quantum features including tunnelling, coherence, and entanglement to function at remarkable levels of efficiency [12]. Tunnelling is a quantum mechanical phenomenon where particles such as electrons or protons travel through a potential barrier that they should not be able to pass [13]. In biological systems, quantum tunnelling is vital for processes that include enzyme reactions and photosynthesis [13]. It allows electrons or protons to pass through energy barriers and thus significantly enhances the speed and efficiency of these reactions [13]. This capability is fundamental to the effective functioning of cellular processes at the atomic level and contributes to the high efficiency observed in biological systems such as light-harvesting complexes in photosynthesis [13] (Table 1).

Table 1 Key quantum phenomena and definitions.
Full size table

Lyu et al. [14] focused on the role of melanin in the turnover of photoreceptor discs in the retinal pigment epithelium (RPE) and its role in age-related macular degeneration (AMD) and Stargardt disease. Investigators utilized “chemiexcitation,” which is a quantum chemistry phenomenon where a chemical reaction leads to the formation of electronically excited states [15]. This process does not involve light energy but instead electrons are triggered by molecular interactions and energy transfers within chemical structures, e.g. the decomposition of dioxetanes [14]. This phenomenon can cause non-radiative energy transfer to DNA or other biomolecules, leading to effects such as bioluminescence or melanin-mediated transfer of energy [14]. In this investigation chemiexcitation of electrons significantly impacts the degradation of lipofuscin—a pigment that accumulates due to the breakdown of photoreceptor discs and is involved in retinal degeneration [14].

The investigation employed high-resolution electron microscopy, genetics, pharmacological treatments, and chemical interventions to demonstrate the degradation pathways of lipofuscin in both pigmented and albino Abca4-/- mice. It was found that in pigmented mice, chemiexcitation aided by melanin effectively reduced lipofuscin levels [14]. On the other hand, albino mice, which lack melanin, showed an accumulation of lipofuscin and related structures unless treated directly with a synthetic dioxetane that induces chemiexcitation (thus bypassing the need for melanin) [14]. Results highlighted that melanin not only aids in the physical breakdown of photoreceptor disc remnants but also chemically through electron excitation, which is pivotal for mitigating lipofuscin buildup and therefore, could be potentially used in delaying the progression of AMD and Stargardt disease [14].

Living systems have had 3.5 billion years of evolutionary optimization, and during this vast time span, these biological systems have likely developed the ability to manipulate quantum dynamics in ways that are not yet fully understood [11]. Advancements in single particle imaging, ultrafast spectroscopy and time-resolved microscopy, and other similar experimental techniques will further enable the study of ophthalmic systems at small scales, and will further reveal the interplay between classical physics and quantum effects.

Future research could also examine if any distinct quantum signatures can be seen in a variety of retinal pathology [12]. As quantum processes in the eye are better understood, this information may also provide novel insights that can be transferred to the field of quantum computing, medical imaging and the development of novel therapeutics. Further multidisciplinary research involving ophthalmologists, spectroscopists, chemists and theoretical physicists to examine this area further.