We rely on our vision for virtually everything, yet we rarely stop to think about the intricate biological process that makes it all possible. Our eyes are constantly coordinating with the brain to process light, distinguish color, and construct images, all without a conscious effort. But despite its remarkable efficiency, this system is far from invincible. Our vision hinges on a delicate balance of interconnected components. Even minor disruptions can have devastating consequences.

The cornea—the clear, dome-shaped outer layer of the eye—is the cornerstone of our vision,  accounting for 70% of the eye’s focusing power through refracting light rays onto the retina at the back of the eye. Its surface is lined with a stratified epithelium that plays a crucial role in maintaining eye clarity and function. At the limbus, where the edge of the cornea meets the sclera (the white of the eye), the corneal epithelium hosts a reservoir of stem cells. These stem cells can proliferate to ensure a constant renewal of epithelial cells, allowing the cornea to repair itself and remain transparent. 

However, when these stem cells are depleted—whether due to trauma, genetic disorders, or immune-mediated conditions—this renewal process is thwarted. Consequently, fibrotic tissue slowly accumulates over the cornea, leading to vision loss. This is the harrowing reality faced by those with limbal stem cell deficiency (LSCD). 

For years, treatment options for LSCD have been limited. Traditional approaches usually involve grafting healthy corneal epithelial tissue from a patient’s healthy eye or, if not possible, from a donor. However, these methods come with significant limitations, including limited donor availability, quality inconsistencies, and the risk of immunological rejection. 

A new study published in The Lancet by scientists at Osaka University offers a promising alternative. The study details a groundbreaking first-of-its-kind clinical trial, where stem cell technology was harnessed to treat patients with severe corneal eye diseases. Researchers successfully used induced pluripotent stem cells (iPSCs) to create corneal epithelial cell sheets, which were then grafted onto the patients. 

This breakthrough was only made possible due to the powerful nature of iPSCs. While all somatic cells contain the exact same genetic information, the “turning on” and “turning off” of specific genes leads to phenotypic diversity in our cells. Scientists have leveraged this phenomenon to create iPSCs through reprogramming adult stem cells back into a pluripotent state, allowing them to differentiate into an unlimited variety of cell types, including corneal epithelial cells. 

The researchers developed a specialised method known as SEAM (self-formed ectodermal autonomous multi-zone) to guide iPSCs into developing eye-related tissues in a way that mimics the natural development of the eye, minimising the reliance on complex external signals.  The most crucial product of this process was the creation of corneal epithelial cells. 

The resulting iPSC-derived corneal epithelial cells (iCEPs) were then cultivated into sheets and grafted onto patients' eyes following the removal of sub-epithelial fibrotic tissue.

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Above: Procedure that researchers used to generate and transplant human iCEPS. Image courtesy of Soma et al., 2024.

The study included four main participants with varying stages of LSCD, ranging from moderate stem cell loss to severe vision impairment. After the operation, the results were consistently monitored throughout a 52-week follow-up period as well as an additional one-year safety monitoring period. 

Significant improvements were observed in all patients, with the main metric being the LCSD  disease stage. Additionally, visual acuity was enhanced and corneal opacification diminished in all treated eyes. Most importantly, the team observed no major adverse effects such as tumorigenesis or immune rejection, which have historically hindered stem-cell-based therapies. 

While the exact mechanism by which the iPSC-derived grafts restored the corneal surface remains uncertain, the results of the study are undeniably promising. 

The team at Osaka University Hospital is already planning to initiate a larger clinical trial to enhance the compelling results of their study. Thanks to the ingenuity and innovation of these researchers, the ability to restore vision loss is no longer confined to our imagination. For those living with LSCD, the future may finally be in focus.

Written by Farah Abdellatif, this article was selected as a winner of our 2025 High School Science Communication Challenge. From Sudan, Abdellatif is a student at North London Collegiate School in Dubai.