Corneal transplantation used to be synonymous with penetrating keratoplasty (PK): a full-thickness procedure that delivered optical clarity at the cost of slow rehabilitation and a meaningful risk of rejection and secondary glaucoma. Over the past two decades, a quiet revolution has taken place. Layer-selective procedures now allow surgeons to replace only what is diseased and keep what is healthy. For endothelial failure, Descemet’s membrane endothelial keratoplasty (DMEK) has become the benchmark in suitable eyes; for stromal disease, deep anterior lamellar keratoplasty (DALK) can restore transparency while preserving the patient’s own endothelium; for keratoconus, biologic ring segments (CAIRS) are emerging as a tissue-friendly alternative to synthetic devices and can be combined with cross-linking to stabilise the cornea.

These advances have shortened recovery, reduced immunologic risk, and made outcomes more predictable – developments that place optometrists at the centre of earlier detection, more effective treatment, better expectation-setting, and safer shared care.

HOW CORNEAL TRANSPLANTATION DIFFERS FROM OTHER ORGAN TRANSPLANTS

Many patient anxieties melt away when we explain what makes corneal transplantation unique. The cornea is avascular; it has no direct blood supply. This single anatomical fact lowers the risk of immune rejection dramatically compared with vascularised organs like kidneys, livers or lungs. When rejection does occur, it’s usually confined to the grafted tissue and often responds to intensive topical steroid drops if caught early.

Because the cornea is immune-privileged and matching of blood groups or HLA (human leukocyte antigen) typing isn’t required, grafts are ordered through eye banks and surgery is usually scheduled routinely – most patients book a date within several weeks of their surgical consultation rather than waiting for a ‘call’ like other organ recipients. Postoperatively, almost every patient will use topical corticosteroid drops for a few months, tapering under the surgeon’s guidance. Explaining it this way reassures patients – it’s planned, predictable surgery with high success rates, and optometrists help guide the recovery in the community.

ENDOTHELIAL DISEASE AND THE RISE OF DMEK

Endothelial dysfunction – most commonly from Fuchs’ endothelial corneal dystrophy (FECD) or pseudophakic bullous keratopathy – remains the leading indication for corneal transplantation in developed health systems. The typical clinical picture is a patient in their 60s or 70s describing ‘morning fog’ that lifts as the day progresses, central guttae on slit-lamp examination, a thickened cornea on pachymetry, and a drop in contrast and nighttime quality of vision. Historically, these patients faced PK with months of visual rehabilitation and substantial suture-induced astigmatism. Endothelial keratoplasty revolutionised the surgical management of endothelial dysfunction by treating only the failing endothelial layer.

DMEK represents the most anatomically respectful approach to endothelial replacement. The donor tissue is nothing more than Descemet’s membrane with its single layer of endothelium – about 8–12 µ in thickness, very similar to cling film. In surgery, the diseased host endothelium is stripped, the ultra-thin graft is injected into the anterior chamber, is unscrolled, and positioned against the posterior stroma. A small bubble of air or gas keeps it in place while adhesion develops over hours to days. Because no donor stroma is transplanted, there’s no stromal interface to scatter light, and there does not tend to be the irritating hyperopic shift that occurs with procedures such as DSEK and Descemet's stripping automated endothelial keratoplasty (DSAEK) that also transplant corneal stroma. Visual rehabilitation is often remarkably quick: many patients notice a big improvement within seven to 14 days and return to completely normal within a few weeks. Just as important, the risk of immunologic rejection is low, and steroid exposure can often be tapered more quickly than after full-thickness grafting.

DMEK has the advantage of being able to replace the failed endothelial layer of a penetrating keratoplasty. This often avoids the need for patients with a failed penetrating graft to have the prolonged visual recovery associated with that procedure. While performing DMEK under a PK is a very difficult procedure, the patient benefit in successful cases can be huge.

For the optometrist, DMEK reshapes timelines and priorities. Patients often present for refraction earlier than expected; a conservative approach is sensible in the first weeks, as small refractive shifts can settle as oedema clears. Visual acuity can fluctuate with subtle oedema, so sometimes your reassurance is just as valuable as the phoropter. Sub-epithelial scarring from chronic oedema can take months to fully resolve. Tasks for the patient’s eye care team include reinforcing drop adherence and checking intraocular pressure (IOP) while patients are on topical steroids. DMEK detachments are not uncommon in the early postoperative period, but it is very rare for them to occur after the graft has fully attached. DMEK detachments are usually correctable with an in-clinic or in-theatre ‘rebubbling’ by the surgeon.

DMEK also pairs elegantly but routinely with cataract surgery in what many call a ‘triple procedure’ – phacoemulsification, intraocular lens (IOL) implantation, and endothelial keratoplasty in one procedure.

From the patient’s perspective, this compresses risk and recovery into one operation and avoids two separate procedures. From the optometrist’s standpoint, it means an early period of refractive uncertainty, as both corneal clarity and lens position settle. A staged approach to glasses, with temporary spectacles or updated readers before the final refraction, often keeps patients comfortable without locking them into premature prescriptions. Anisometropia may need to be addressed with contact lenses if there is a gap between having the second eye grafted.

Where, then, do DSEK and DSAEK fit?

These slightly older techniques include a sliver of donor stroma with Descemet’s membrane and endothelium. The added thickness simplifies tissue handling and can be advantageous in complex eyes – those with prior glaucoma drainage devices, anterior segment abnormalities, or profound corneal oedema where unscrolling a DMEK graft is treacherous. Visual results are good, but the interface can blunt contrast and introduce more hyperopic shift, and the recovery tends to be slower.

Patients who have one eye of each procedure frequently prefer the DMEK side for crispness – a useful anecdote when helping someone weigh options. Yet the key message for primary care is practical: knowing which procedure was performed guides follow-up expectations, informs how aggressively you chase early refractions, and shapes how you counsel on the pace of improvement.

STROMAL DISEASE, DALK, AND THE PLACE OF PK

Not all corneal pathology is endothelial. Advanced keratoconus with scarring, healed microbial keratitis, and traumatic opacities can compromise the anterior stroma while leaving the endothelium healthy. In these scenarios, deep anterior lamellar keratoplasty (DALK) allows surgeons to replace diseased stroma down to Descemet’s membrane, preserving the patient’s own endothelial layer. The surgical goal is a clean separation – a ‘big bubble’ – between stroma and Descemet’s; when successful, the optical result approaches that of PK without exposing the eye to the principal long-term risk of corneal transplantation: chronic endothelial cell loss and rejection.

For optometrists co-managing DALK, the rehabilitation is much slower than DMEK. Sutures are present and, although patterns aim to minimise astigmatism, the cornea can be optically unruly until selective suture removal and wound remodelling proceed. Early refractions help the patient function, but the definitive prescription often evolves over months. Contact lens expertise is invaluable in this setting. Some patients achieve excellent spectacle acuity; many still benefit from modern scleral lenses that vault the graft-host junction and address residual irregularity and aberrations without touching the new cornea. Because the endothelium is not transplanted, steroid courses are shorter, pressure-related side effects are less common, and late endothelial failure – the inevitable complication of PK – is essentially eradicated.

Why perform PK at all? Full-thickness transplantation retains a role when pathology is truly full thickness: deeply cicatricial scars, perforating injuries, descemetocele sequelae, or eyes where DALK cannot be completed safely because of recurrent micro-perforations and scarring that obliterates the deep surgical plane needed for a DALK. PK’s optics can be superb, but they’re paid for with greater immunologic risk, long-term endothelial cell loss, and an extended period of suture-mediated astigmatism. Patients should understand that while the clarity can be transformational, the journey is slower and the vigilance higher. For optometrists, this translates into a longer period of refraction adjustments, more frequent pressure checks while on steroids, and a lower threshold to treat ocular surface disease aggressively to protect a valuable graft.

A modern twist worth noting is the ‘mushroom’ graft – a hybrid in which a large-diameter anterior cap is paired with a smaller posterior stem. In effect, it maximises stromal replacement while limiting how much endothelium is transplanted, preserving some of the host’s posterior cornea. Clinically, this can yield more stable wounds, less induced astigmatism, and lower rejection risk than a standard PK, which is particularly useful in traumatised or paediatric corneas. For optometrists, the postoperative management resembles DALK more than PK: refraction refines as sutures are adjusted, and optical rehabilitation is often smoother than with a traditional full-thickness button.

KERATOCONUS AND THE EMERGENCE OF CAIRS

Keratoconus straddles biomechanics and optics: a cornea that’s too steep and too thin to provide stable focus, and too irregular to be corrected fully with spectacles. Crosslinking has rightly become the backbone of disease modification, but many young adults are still left functionally impaired by shape irregularity or contact lens intolerance. Intrastromal corneal ring segments have long offered a mechanical solution, but synthetic devices can extrude, migrate, or trigger stromal thinning in fragile corneas.

Corneal allogenic intrastromal ring segments (CAIRS) have revolutionised this concept with human donor tissue. Implanted into femtosecond-created channels, these biologic arcs integrate with host stroma rather than sitting as foreign bodies. The optics are familiar: placing tissue in the mid-peripheral cornea flattens the cone and regularises the topography. The clinical experience, however, is subtly different. Because the material is corneal, the surface tends to be quieter, the risk of extrusion appears lower, and the segments can be tailored to match eccentric or asymmetric cones. When combined with cross-linking in progressive disease, CAIRS can both reshape and stabilise the cornea, often buying time – or even avoiding the need for full-thickness transplantation.

For optometrists, CAIRS offers a great option for young patients who are struggling: there’s a middle path between ever-thicker spectacles, hard contact lenses that they may be intolerant of, and a transplant. Preoperatively, optometrists can assist with an accurate repeatable refraction (not an easy task in keratoconus). Post-operatively optimising the ocular surface is critical before optical visual rehabilitation. The goal of CAIRS is to give the patient good vision in glasses, not emmetropia. Scleral lenses can still be fitted over a cornea with CAIRS.

CAIRS isn’t a cure-all, and advanced scarring or lens intolerance may still lead some patients to DALK or a mushroom graft later on. Yet for a significant group, biologic ring segments expand the therapeutic window and preserve native cornea for longer.

OPTICAL REHABILITATION: SEEING THE JOURNEY THROUGH

Across all keratoplasty types, optical rehabilitation is where optometry turns surgical success into genuine visual benefit for patients. The tasks are the same – refraction, lens fitting, ocular surface care – but the timing and tactics vary.

After DMEK, early improvement makes initial prescriptions tempting. A pragmatic approach is to provide an interim correction if daily function demands it, while counselling that fine-tuning is likely within the first few months as the cornea dehydrates and stabilises. Small refractive shifts are common; patients appreciate knowing this ahead of time. Dry eye management also matters: a healthy tear film supports the healing epithelium and stabilises the vision. Poor quality and fluctuating tears give poor quality and fluctuating vision.

After DALK, patience is key. Selective suture removal by the surgeon alters astigmatism in steps; each step deserves its own refraction. Rather than chasing every half-dioptre with new glasses, many practices adopt a rhythm – temporary lenses to bridge function, then a definitive pair once the suture map is stable. For those with residual irregularity, modern scleral lenses provide reliable, comfortable acuity with minimal interaction at the graft-host junction. Teaching insertion and removal, checking for blanching and midday fogging, and coordinating with the surgeon about when lens wear can safely begin are all practical, high-impact contributions that highlight the critical role that optometrists play in the care of these visually vulnerable patients.

Post-PK patients need both optical creativity and clinical vigilance. Glasses can work beautifully when topography allows; when it doesn’t, hybrids or sclerals can tame irregular astigmatism. Because steroid exposure is longer, IOP checks are essential, and because the endothelial reserve is finite, any drop in clarity is a call to act – not a reason to ‘watch and wait’.

RECOGNISING TROUBLE EARLY

Complications are less common than they once were, but they still affect outcomes.

The first is graft detachment after DMEK: the patient may report a sudden drop in clarity; you might see a meniscus at the graft edge, a faint line on retroillumination, or an area that refuses to clear with time. In this setting, reassurance and speed matter in equal measure. Many detachments are partial and easily corrected with a rebubbling procedure.

The second is immune rejection. Patients often remember the mnemonic ‘RSVP’ – redness, sensitivity to light, vision loss, pain. It is critical that optometrists are aware that rejection can be subtle before it’s obvious: new keratic precipitates on the graft, an anterior chamber reaction out of proportion to symptoms, or a faint Khodadoust line. When in doubt, treat and review; refer if needed. If you are worried about rejection, commit to a strong steroid like prednisolone or dexamethasone. Starting an intensified steroid regimen today is much better than delaying treatment until definitive signs of rejection become present.

Third is pressure. Steroid-responsive IOP spikes don’t follow a timetable. Measure pressure at every meaningful visit while patients are on steroids; a rough ocular surface or sore lids can distract from what’s happening inside the eye. Younger patients, in particular, can develop very rapid and severe responses.

Fourth is infection and epithelial integrity. Bandage lenses relieve bullous pain, but they’re not set-and-forget devices. Antibiotic prophylaxis is essential, lens hygiene must be impeccable, and any epithelial defect on a graft deserves more caution than the same defect on a native cornea. A small infiltrate can threaten a very precious gift from a grieving family.

Finally, don’t forget the human complication: expectations. Modern keratoplasty is a triumph of microsurgery, but recovery is still long and sometimes slow. Explaining each step helps – why vision will be foggy after a bubble, why sutures move in stages, why glasses might change more than twice in a year.

MAKING THE REFERRAL COUNT

When a patient is ready for a surgical opinion, the quality of the referral makes a real difference. A succinct letter that answers three questions works best.

First, what is the visual problem – night glare, morning fog, contact lens intolerance – supported by acuity, refraction, and keratometry (if available).

Second, what is the structural problem – guttae and oedema with pachymetric thickening; a central stromal scar with irregular astigmatism; an inferior cone with apical thinning?

Third, what has already been tried and how did it go – hypertonics, bandage lenses, crosslinking, contact lens trials? Add in practical details: ocular comorbidities (glaucoma, dry eye disease, herpes simplex virus, etc.), systemic medications that may affect healing, anticoagulant use, allergies, and the patient’s goals. A referral with these points makes planning and assessment far more efficient – especially in a stretched public system.

In your busy practice, just remember that for post-transplant recovery, DMEK feels quick and crisp; DSAEK is steadier in complex eyes; DALK is safer long term when the endothelium is healthy; PK is a rescue that still has a role. CAIRS can be a bridge, preserving corneal tissue in keratoconus while improving function now. A confident optometrist generally makes a confident patient with a road map for what they can expect and what their recovery will be.

FUTURE DIRECTIONS

Even as current techniques mature, the frontier keeps moving.

Descemetorhexis without graft/Descemet’s stripping only (DSO), where central guttae are removed to stimulate peripheral endothelial migration, offers a graft-sparing option for selected FECD eyes, especially when paired with Rho-kinase inhibitors such as Ripasudil. Cultured endothelial cell therapy, delivered as an injection rather than a lamellar graft, could expand access where donor tissue is scarce and may simplify postoperative care. Bioengineered scaffolds, whether acellular or seeded with human cells, are inching closer to the clinic and could ease global shortages. Meanwhile, artificial intelligence is already helping flag early keratoconus on routine imaging, making earlier, better-timed referrals possible.

For optometry, each innovation has a practical theme: triaging who can safely wait and who should be referred urgently; explaining novel therapies in plain language; adapting follow-up protocols to new pharmacology; and refining the art of optical rehabilitation for eyes that are restored anatomically but still need tuning optically.

BRINGING IT ALL TOGETHER

Advances in corneal transplantation haven’t just changed what happens in theatre; they’ve reshaped the care around it. Patients move faster from diagnosis to intervention, see better sooner, and face fewer long-term risks. That places optometrists in an even more pivotal position. They’re the ones who notice the morning blur and scattered light before the patient can describe them. They’re often the trusted long-term eye care provider, so patients may value their optometrist’s advice even more than their surgeon’s. Surgeons may fix the anatomy – but it’s usually optometrists who fix the optics.

So, in your busy clinic tomorrow, you should feel confident about what to say to patients with a variety of corneal pathologies. When you diagnose Fuchs’ dystrophy, you can reassure patients that while DMEK surgery exists, a referral doesn’t always mean immediate surgery. DMEK is planned, not urgent, and usually only needed when vision becomes more troublesome than the thought or risk of surgery. Rejection is uncommon because the cornea lacks a blood supply, and most people regain useful vision fairly quickly, with just a few months of drops.

When you meet a 22-year-old with contact lens–intolerant keratoconus, you can outline a path that includes cross-linking and, if appropriate, biologic ring segments that integrate rather than irritate. Reassure that there are interventions that may defer or even avoid full-thickness transplantation.

When you co-manage a DALK or a mushroom graft, you can explain why glasses will change as sutures come out, why scleral lenses might be the patient’s best friend, and why the long game is safer because the patient’s own endothelium is intact.

Modern keratoplasty is precision made visible or, in the case of DMEK, almost invisible. By understanding the rationale behind DMEK, DSAEK/DSEK, DALK, PK, CAIRS, and hybrid techniques, optometrists can translate surgical advances into everyday visual reality for their patients.