Allotex Allogenic Corneal Inlay for Presbyopia: A Minimally Invasive Solution
Understanding Presbyopia and Its Challenges
Presbyopia is an age-related loss of near focusing ability that typically becomes symptomatic after age 45. It is extremely common – an estimated 1.8 billion people worldwide are presbyopic, experiencing difficulty with near tasks like reading. Emmetropic presbyopes (those with previously perfect distance vision) enjoy good distance vision with little or no correction, yet gradually lose their near vision. These patients are often reluctant to compromise their distance clarity or undergo major surgery, making presbyopia correction a delicate balance.
Traditionally, presbyopia is managed with reading glasses or multifocal contact lenses, but many patients desire spectacle independence. Surgical options exist – monovision laser corrections, multifocal intraocular lenses (IOLs via lens exchange), corneal laser procedures (PresbyLASIK), corneal inlays, and even newer pharmacological drops – but no single technique is universally accepted as the standard. Each approach has limitations, especially for emmetropic or mildly ametropic presbyopes who do not otherwise need full-time glasses. Monovision (using one eye for near, one for far) can reduce binocular acuity and stereopsis, and not everyone tolerates the imbalance. Refractive lens exchange (replacing the clear lens with a multifocal or accommodating IOL) is effective for near vision but is not always an ideal solution in young emmetropes. Given these issues, there is a strong interest in alternative solutions that can improve near vision while minimally impacting distance vision and maintaining a high safety profile.
Biological Corneal Inlays: A Proven Track Record
In exploring presbyopia solutions, corneal inlays have drawn attention because they alter the eye’s optics at the corneal plane, are removable, and leave the eye’s internal anatomy untouched. Earlier attempts used synthetic materials (for example, the KAMRA small-aperture inlay and the Raindrop hydrogel inlay) which showed promise in improving near vision. However, synthetic implants had biocompatibility problems; many patients developed corneal haze, fibrosis, or other complications, and the devices often had to be removed. Ultimately, those synthetic presbyopic inlays were withdrawn from the market . This history led researchers to ask: could an allogenic (biological) corneal inlay succeed where synthetics fell short ?
The idea of using donor corneal tissue as an implant is not entirely new. In the keratoconus realm, corneal allogenic intrastromal ring segments (CAIRS) – essentially ring-shaped inlays made from donor cornea – have been used to stabilize and reshape the keratoconic cornea. Studies have demonstrated that CAIRS can significantly improve uncorrected and corrected vision and corneal topography in keratoconus, with outcomes comparable to traditional plastic ring segments . Notably, the allogeneic nature of CAIRS seems to confer a lower complication rate: for example, in a multi-study analysis, the incidence of visual phenomena like halos or glare was only ~0.2% with allogenic rings, versus around 10% with synthetic polymethylmethacrylate rings . Researchers attribute this to the biocompatibility of human collagen, which more closely matches the cornea’s optical properties and integrates better with native tissue . The success of CAIRS in a disease setting provides a safety and efficacy precedent for using biological inlays in the cornea. It is on this foundation that allogenic corneal inlays for presbyopia – such as the Allotex inlay – have been developed.
Design and Mechanism of the Allotex Presbyopic Inlay
The Allotex presbyopic inlay is a small disc-shaped lenticule fashioned from human donor corneal tissue. Donor corneas (not suitable for full transplant due to age or other factors) are processed to create hundreds of ultra-thin “blanks” of stromal tissue . These lenticules are decellularized (removing cells that could cause immune reactions, leaving behind the collagen matrix) and then precisely shaped with an excimer laser into a microscopic lens. The finished inlay is approximately 2.6 mm in diameter and ~20–22 μm thick, essentially a wafer-thin sliver of collagen . Despite its tiny size, the lenticule is crafted to have a specific add power – roughly +2.50 diopters – in the central optical zone . In other words, it behaves like a small corneal contact lens that provides a near-focus power boost. The inlays are stored in a sterile packaging solution (often in a vial with recombinant albumin) and sterilized with high-energy radiation(electron-beam), ensuring no transmissible pathogens . Because the material is human collagen, the refractive index is nearly the same as the host cornea, minimizing interface issues like reflections or scatter.
Mechanism of action: The Allotex inlay is designed to improve near vision by increasing the eye’s depth of focus rather than by simply creating a strong monovision. Its aspheric design induces a controlled amount of higher-order spherical aberration (4th and 6th order) in the central cornea. By inducing these aberrations (in a manner analogous to certain extended depth-of-focus IOL designs), the inlay stretches the range of clear focus for the inlay eye. Practically, this means the treated eye gains improved intermediate and near vision while retaining useful distance vision. The +2.5 D central add power effectively slightly increases the cornea’s curvature power in the center, aiding near focus at ~40 cm . Unlike a multifocal optic, which splits light into distinct focal points, this approach creates a continuous range of focus (though at the expense of a mild reduction in peak sharpness on the eye’s optical axis). The result is a form of “corneal multifocality” or extended depth-of-field effect. This allows patients to see up close without losing all clarity at distance in that eye – a gentler compromise than full monovision. It’s important to note that only one eye (usually the non-dominant eye) receives the inlay, so the fellow eye remains fully optimized for distance. Binocularly, the brain can blend the inputs, granting the patient improved near vision from the inlay eye and crisp distance vision from the dominant eye.
Surgical Placement Under a LASIK Flap
Surgically, implanting the Allotex inlay is an ultra-minimally invasive procedure – very similar to performing a LASIK flap, but without any excimer laser ablation of the cornea. The surgeon first uses a femtosecond laser to create a thin corneal flap (approximately 100–110 μm thick) on the non-dominant eye. The diameter of the flap is usual for LASIK, around 8–9 mm, providing plenty of space to place the 2.6 mm inlay. Once the flap is created and lifted, the surgeon introduces the sterile allograft lenticule onto the stromal bed. Under an operating microscope, the inlay is carefully centered over the pupil to align with the visual axis. Because the lenticule is transparent and tiny, a specialized inserter is used: it is often a loop-like instrument about 3–4 mm across, which can pick up the wet inlay by surface tension. The surgeon “floats” the inlay onto the cornea and then wicks away the fluid, allowing the lenticule to gently settle into place on the stromal surface. Minor adjustments can be made while the inlay is still moist – it can be nudged into perfect position. Once it dries for a short time, the lenticule adheres and integrates with the cornea and becomes difficult to dislodge. The corneal flap is then laid back down over the inlay, just as it would be in completing a LASIK procedure.
Once the flap is closed, the inlay resides in a pocket within the cornea – effectively making the procedure a lamellar inlay implantation. There is no ablation and no full-thickness incision; thus, the structural integrity of the eye is largely preserved. Postoperatively, patients typically use a regimen of corticosteroid and antibiotic drops (similar to LASIK). Notably, the required steroid course is relatively short – on the order of a few weeks – because the allogenic implant causes minimal inflammation . In clinical trials, no significant corneal haze or immune rejection response has been observed, and inlays are often essentially invisible on slit-lamp exam under the healed LASIK flap . Anterior segment OCT is used to confirm the inlay’s position since it can be hard to see otherwise. Because the inlay is placed under a flap, it lies in a immune-privileged space (the corneal stroma typically has low immune activity), further reducing the risk of rejection or inflammation.
Biocompatibility and Removability Advantages
A key advantage of the Allotex allograft inlay is its biocompatibility. Being made of human collagen, the inlay integrates with the surrounding stroma rather than inciting a foreign-body reaction. Surgeons have noted that after a few months the inlay can hardly be distinguished from the host cornea – there is no telltale line or haze around it. This is in stark contrast to synthetic inlays. The refractive index of the allograft is the same as cornea, so it avoids inducing glare or halos from index mismatch.
Another major benefit is removability. If for any reason the patient cannot tolerate the visual effect (for example, some people may struggle with even mild monovision or notice visual changes they don’t like), the inlay can be explanted. Removing the inlay is usually done by lifting the LASIK flap again and simply peeling or rinsing out the lenticule. Because it is thin and unencapsulated, it comes out easily. The cornea is then re-floated with saline and the flap repositioned. The easy reversibility of the allogenic inlay gives both surgeons and patients added confidence – it’s a “try-and-see” solution that can be undone if needed, unlike permanent corneal laser ablations or intraocular surgeries.
Importantly, because the allograft inlay is placed in only one eye, the other eye acts as a control and safety net. The patient’s binocular distance vision remains excellent, and if the inlay eye’s vision were ever compromised, one could rely on the fellow eye. In practice, complications like infection or significant inflammation with inlays have been exceedingly rare. The procedure disrupts less tissue than even a standard LASIK, and inlays have shown a very low rate of adverse events over several years of study (with no cases of immunologic rejection reported).
Comparison to Other Presbyopia Treatment Options
Laser monovision (via LASIK/PRK or contact lenses) has been a go-to solution for presbyopia in many emmetropes. In monovision, one eye (usually non-dominant) is made mildly myopic to see near, while the dominant eye remains focused for distance. This can certainly reduce dependence on reading glasses, but it comes at a cost. To achieve a strong near vision (J1–J2, or being able to read fine print), one typically needs about –1.50 D to –2.00 D of myopia in the reading eye. That level of monovision will cause the near eye’s distance vision to drop to roughly 20/60 or 20/80 (or worse) and can reduce binocular depth perception . Many patients, especially those who have enjoyed crisp vision in both eyes, struggle with this compromise. While some adapt well, others describe the monovision eye as feeling “blurry” or report difficulty with night driving and subtle 3D tasks due to loss of stereopsis. By contrast, an allogenic corneal inlay aims to achieve similar near vision improvement with far less distance blur in the treated eye.
Another advantage is reversibility – if monovision LASIK is done and the patient dislikes it, one must perform another laser procedure to undo it (or fit a contact lens). With the inlay, a simple removal restores the original vision. That said, monovision remains a straightforward and cost-effective option for many; the allogenic inlay is simply a new alternative that may offer a more balanced visual outcome for those who are sensitive to the trade-offs of monovision.
Refractive lens exchange (RLE) or presbyopic lens surgery is another route to address presbyopia. This is essentially an early cataract surgery: the clear crystalline lens is electively removed and replaced with a multifocal or extended depth-of-focus intraocular lens to provide near and far focus. RLE can achieve excellent results, effectively “curing” presbyopia in both eyes. For the emmetropic presbyope, many surgeons feel RLE is too aggressive if other options exist. In that context, a corneal inlay is appealing because it avoids intraocular surgery altogether. The Allotex inlay can be placed in one eye to give near vision, delaying or obviating the need for lens surgery until perhaps the patient naturally develops cataracts later in life. Importantly, having a corneal inlay does not preclude future cataract surgery – the inlay can be removed beforehand or even potentially left in place if it does not interfere with calculations (though removal is simple, so typically it would be removed when the time comes to do cataract surgery). Compared to multifocal IOLs, the corneal inlay causes less dysphotopsia (fewer halos) because it uses the eye’s existing optics in a more subtle way . In summary, the inlay offers a middle ground for patients who seek spectacle-free near vision but are not ideal candidates for or are uncomfortable with lens replacement surgery.
It’s also worth noting other approaches: Corneal laser presbyopia treatments (like PresbyLASIK) attempt to create multifocal corneal shapes by laser ablation. These have had mixed success and can be irreversible. In comparison, an allogenic corneal inlay is a one-time intervention that provides continuous near vision improvement, and if it doesn’t suit the patient, it can be removed – a unique combination of effectiveness and reversibility.
Clinical Outcomes at 3 Years: Safety and Efficacy Evidence
The feasibility of Allotex allogenic inlays for presbyopia has been evaluated in clinical studies, including a notable prospective trial with 3-year results. In that study, 25 emmetropic presbyopic patients were treated with a corneal inlay in the non-dominant eye and followed for 36 months . Their untreated fellow eyes served as controls. The outcomes from this and other trial data paint an encouraging picture of sustained near vision gains without major loss of distance function:
Near Visual Acuity: Patients’ near vision improved significantly in the inlay-implanted eye. In the 3-year study, the uncorrected near visual acuity (UNVA) of treated eyes was vastly better than that of the untreated eyes (which remained presbyopic) . On average, the inlay eye could achieve around J2 (N6) near acuity (approximately 20/25 at 40 cm) – an improvement from a preoperative near acuity of roughly J10+ (around 20/80) without correction. In practical terms, most inlay patients could read newspaper-sized print comfortably with the treated eye, whereas preoperatively they could not. All patients in early trials achieved at least 20/40 (Jaeger 5) or better near vision in the treated eye, meaning they could read normal newsprint, and many achieved J1–J2 (very small print) binocularly . This level of near vision represents a return to functional reading ability for previously glasses-dependent presbyopes.
Distance Visual Acuity: A critical question is: what happens to distance vision in the inlay eye? Impressively, the studies show minimal impact on distance acuity. At 3 years, there was no statistically significant difference in uncorrected distance visual acuity (UDVA) between treated eyes and fellow (untreated) eyes . The mean UDVA in inlay eyes remained around 20/25 or better, with many inlay eyes seeing 20/20 minus. Some patients did experience a slight myopic shift in the treated eye (expected from the inlay’s add power), leading to about a one-line drop in that eye’s distance acuity. In the 3-year cohort, 6 patients (24%) had a 1-line reduction in best-corrected distance acuity in the treated eye compared to pre-op . No patient lost more than one line of corrected vision. Meanwhile, binocular distance vision remained 20/20 in essentially all cases, since the dominant eye was untouched and the brain binocularly summates vision . Patients generally did not notice any significant change in their distance vision for everyday tasks; with both eyes open they functioned as they did before surgery. Importantly, depth perception (stereopsis) was preserved in these patients, presumably because the inlay eye’s distance vision was still quite good (20/25 or better) and thus provided a useful image for binocular fusion. This aligns with the concept that the inlay induces a “mini-monovision” that is easier for the visual system to adapt to .
Depth of Focus: Objective defocus curve testing has confirmed that the inlay extends the range of clear focus. In the 3-year study, the depth of focus (DoF) – defined as the range of diopters over which vision remains ~20/32 (LogMAR 0.2) or better – was about 2.8 D in the treated eyes (and similarly 2.8 D binocularly), compared to only about 1.1 D in the untreated presbyopic eyes . In other words, the inlay eye could see from distance (0 D defocus) through intermediate and up to roughly +2.8 D (around 35–40 cm) and still maintain good acuity, whereas the untreated eye could only handle up to +1.1 D (around 1 meter) before blurring beyond 20/32. This more than doubles the functional focus range of the eye . Patients reported a broad range of clear vision – for instance, being able to read their phone, work on a computer, and even see car dashboard gauges without glasses – tasks that previously required different pairs of spectacles or bifocals. The area under the defocus curve in treated eyes was significantly better at near and intermediate distances than in untreated eyes, confirming a true extension of continuous vision range .
Refractive Stability: Follow-up out to 3 years indicates that the effect is stable over time. Near visual improvement persisted through the 36-month visit in the trial, and distance acuity in the treated eye did not show progressive degradation. This suggests the inlay’s effect is long-lasting, with no evidence of late biomechanical changes in the cornea (e.g. no significant corneal steepening or flattening occurring beyond the initial intended change). Because the inlay does not rely on any metabolic or cellular activity (unlike corneal remodeling in some procedures), the result tends to be stable as long as the inlay remains in place and clear.
Safety and Complications: The safety profile of the allogenic inlay has been excellent to date. In the 3-year study, there were no vision-threatening complications reported. No corneal infections, melts, or clinically significant haze occurred. Best-corrected vision remained high in all patients (again, at most 1 line of loss in a quarter of patients, and even those still had 20/20 or 20/25 correctable vision) . Patients were monitored for signs of rejection (like inflammation around the inlay), but none were observed – consistent with the inlay’s acellular nature. A few patients in earlier trials did request inlay removal due to subjective visual preferences (for example, difficulty adjusting to having one eye slightly different). The removal rate has been low: on the order of 4–8% in trials . Those removals were uncomplicated, and notably, the patients immediately returned to their baseline vision after removal with no lasting corneal issues . No cases of recurrent corneal haze or any need for corneal transplantation have been reported in relation to the inlay, in stark contrast to some synthetic inlay experiences. Table 1 summarizes key outcomes from a representative 3-year clinical study and other reports, highlighting the visual gains and safety indicators.
The data above underscore that allogenic corneal inlays can provide a meaningful near vision benefit for presbyopic patients, with minimal downside in terms of distance vision or safety. Patients in the studies achieved reading vision that met or exceeded normal newspaper-size print requirements, all while maintaining driving-standard distance vision in the treated eye and full distance vision binocularly. The procedure’s reversibility was demonstrated in the few cases it was exercised, giving further credence to its safety.
Conclusion
Allotex allogenic corneal inlays represent an innovative and promising addition to the presbyopia correction arsenal. For optometrists and ophthalmologists, this technology offers a way to help emmetropic presbyopes and those with minimal refractive error achieve independence from reading glasses without resorting to intraocular surgery or permanently altering the cornea. The inlay leverages the unique advantages of biologic tissue – biocompatibility and integration – to avoid complications that plagued earlier synthetic implants. Clinical evidence up to 3 years post-implantation demonstrates that patients can gain around 2–3 lines of near vision, enabling tasks like reading and computer work, while still retaining excellent distance vision (especially when using both eyes together) . Importantly, these benefits come with a strong safety profile: negligible rates of corneal haze or glare complaints, and an easy removal option if needed. In essence, the Allotex inlay offers a minimally invasive, reversible, and effective presbyopia solution – characteristics that are highly attractive in the risk-benefit calculations for treating a non-life-threatening condition like presbyopia.
From an educational standpoint, eye care practitioners should understand that patient selection and counseling are key. Ideal candidates are presbyopes (45–65 years old) with good distance vision (emmetropic or mild Rx) who are motivated to improve near vision and are aware that one eye will be modified for near. They should be free of corneal disease (as a healthy cornea is needed to host the inlay) and have realistic expectations. It should be conveyed that the goal is improved near without glasses, not necessarily absolutely perfect vision at all distances – though many patients end up very satisfied with minimal compromise. As with monovision, some neural adaptation is required, but the data suggest most people adapt well, especially given the treated eye maintains decent distance vision.
Looking ahead, allogenic inlays like Allotex’s may become an important tool for presbyopia management, filling a niche between temporary measures and permanent surgeries. Ongoing studies and longer-term follow-ups will continue to validate their efficacy and safety. If results remain positive, we can expect wider adoption and possibly even enhancements in inlay design (e.g., different add powers or profiles for customization). For now, the 3-year results provide a strong proof-of-concept that biological corneal inlays can safely deliver meaningful presbyopia correction . This approach, born from the synergy of corneal biology and refractive innovation, truly embodies a modern solution to an age-old problem – allowing presbyopes to maintain their active lifestyles and visual freedom with minimal intervention.
Overall, Allotex allogenic corneal inlays offer an exciting presbyopia correction option for the appropriately chosen patient. By preserving what is important (distance vision, corneal health) and improving what is lacking (near vision), all with reversibility, they align well with the refractive goals of many mid-life patients. As clinical experience grows, eye care professionals will be better able to refine patient selection, surgical technique, and postoperative care to maximize outcomes. The concept of a “bioanalogous” corneal implant for presbyopia – using the eye’s own kind of tissue to enhance its optical performance – may well become a mainstream strategy in the coming years, expanding the horizons of presbyopia treatment in the optometric and ophthalmological community.