Penetrating Keratoplasty (Optical) — Procedure Guide, Recovery & Risks | MyMedicPlus

Penetrating keratoplasty (PK), or full-thickness corneal transplantation, replaces the entire diseased or opacified cornea — all five layers from epithelium to endothelium — with a matched donor cornea obtained from an eye bank. It is the most widely performed tissue transplant procedure globally and has been performed for over a century. PK restores corneal clarity and curvature in conditions where both stromal and endothelial disease is present. Compared with newer lamellar techniques (DSAEK, DMEK) that selectively replace only the endothelium, PK is indicated when multiple corneal layers are simultaneously diseased. The procedure is performed under operating microscope magnification using a trephine to cut matching circular buttons from recipient and donor corneas, which are then sutured with fine nylon sutures. Visual recovery is slow, typically requiring 12–18 months. Penetrating keratoplasty (PK) has largely been superseded by selective lamellar techniques for many indications, but remains the procedure of choice when all layers of the cornea are affected by scarring or disease. Unlike deep anterior lamellar keratoplasty (DALK) which preserves the host endothelium, PK replaces all corneal layers including endothelium, making it essential for endothelial failure combined with stromal disease. Graft survival rates at 5 years for low-risk indications (keratoconus) exceed 90%, but fall substantially for vascularised beds, repeat grafts, or high-immunological-risk cases. Tissue is sourced from certified eye banks following stringent donor screening.

Penetrating keratoplasty is indicated when corneal disease affects multiple layers and cannot be managed with lamellar (selective layer) transplantation. Common indications include advanced keratoconus with central scarring or hydrops, bullous keratopathy from Fuchs' endothelial dystrophy with coexisting stromal scarring, full-thickness corneal opacification from healed infectious keratitis (herpes simplex, bacterial, or fungal), severe corneal burns or trauma with full-thickness involvement, and failed previous corneal grafts. It is also indicated for stromal dystrophies (granular, macular, lattice) causing significant visual impairment. Contraindications include active corneal or ocular surface infection, severe dry eye or lid abnormalities impeding epithelial healing, extensive limbal stem cell deficiency, uncontrolled glaucoma, and in children under 2 years where amblyopia management must accompany the transplant. Fuchs endothelial dystrophy with concurrent deep stromal scarring precluding selective endothelial transplantation is a classic indication for PK rather than modern DMEK or DSAEK. Chemical injury, physical trauma with full-thickness corneal disruption, and corneal ectasia following complicated refractive surgery are also indications. A failed previous corneal graft — regardless of original indication — may require repeat PK if endothelial transplantation is not feasible due to iris or anterior segment anatomy.

Under local (retrobulbar block) or general anaesthesia, the patient is positioned supine at the operating microscope. A circular trephine (7.5–9.0 mm diameter) is used to cut a full-thickness button from the central recipient cornea; the diseased disc is removed. A matching or slightly oversized (0.25–0.5 mm larger) donor button, prepared from the preserved donor eye, is placed onto the recipient bed. The donor cornea is secured with interrupted or continuous 10-0 nylon sutures — typically 16 interrupted sutures or a single 12-bite running suture — under high magnification. Suture tension is adjusted using an intraoperative keratoscope (Placido disc) to minimise post-operative astigmatism. The eye is patched and shielded post-operatively. The entire procedure takes 60–90 minutes. Topical steroid and antibiotic drops are commenced immediately. Sutures may remain in situ for 12–24 months to allow wound strength to develop. A trephine of the appropriate diameter (typically 7.5–8.5 mm) is used to cut the host cornea under vacuum. The donor button is cut from an endothelium-up position on an artificial anterior chamber. The graft is secured with 16 interrupted 10-0 nylon sutures or a single running suture, with intraoperative keratometry guiding suture adjustment to minimise astigmatism. The anterior chamber is reformed with balanced salt solution. Operative time is 60–90 minutes under local or general anaesthesia.

Penetrating keratoplasty achieves 5-year graft survival of 80–90% for keratoconus, 70–80% for bullous keratopathy, and 65–75% for regraft procedures. Visual acuity of 6/18 or better is achieved in 70–80% of patients with keratoconus and in 50–60% of those with bullous keratopathy at 12 months. Grafts restore corneal clarity and substantially improve visual quality compared with spectacles or rigid contact lenses in failed corneas. For appropriate cases, best-corrected visual acuity is 6/12 or better in over 60% of keratoconus patients. The surgery is life-changing for patients with severely reduced vision from corneal disease, with most gaining independence from low vision aids. Penetrating keratoplasty restores optical clarity to opaque corneas that cannot be managed by any other technique, achieving best-corrected visual acuity of 6/12 or better in over 70% of cases for keratoconus when graft survival is maintained. For corneal scarring from herpetic keratitis or trachoma, visual rehabilitation through PK enables patients to return to work and daily activities. Repeat PK can achieve acceptable outcomes even after failed primary grafts when immunological risk factors are optimised.

The most significant complication is graft rejection, occurring in 10–20% of grafts within 5 years. Rejection episodes — characterised by reduced vision, photophobia, and a rejection line of keratic precipitates — require urgent high-dose topical corticosteroid treatment, with reversal in 70–80% if treated promptly. Graft failure (endothelial decompensation) occurs in 10–15% at 5 years. Other complications include high post-operative astigmatism (average 3–4 dioptres) requiring rigid contact lenses or suture adjustment, glaucoma (20–30%), loose or broken sutures, wound dehiscence, infectious keratitis of the donor tissue, and persistent epithelial defects. Children require aggressive amblyopia therapy post-operatively to prevent irreversible visual loss. Allograft rejection is the leading cause of corneal graft failure — endothelial rejection, stromal rejection, or epithelial rejection can occur months to years post-operatively. Rejection episodes — presenting with red eye, photophobia, and visual blur — require urgent intensive topical steroid therapy. High post-operative astigmatism (often 3–5 D or more) frequently requires selective suture removal or adjustment. Secondary glaucoma from topical steroid use or synechia formation complicates 15–25% of cases.

The eye is patched for 24 hours post-operatively and reviewed on day 1 to check the graft is clear and sutures intact. Topical corticosteroid drops (e.g., prednisolone 1%) are used intensively for 3–6 months then tapered slowly, often continuing at low doses for 12–18 months or longer to prevent chronic rejection. Topical antibiotics are used for 4–6 weeks. Physical activity is restricted for 2–4 weeks; eye protection with a shield is worn at night for 6 weeks. Sutures may be selectively removed at 12–24 months to correct astigmatism. Final refraction cannot be determined until all sutures are removed and the corneal shape has stabilised, typically 18–24 months post-operatively. Patients are educated on rejection symptoms and instructed to seek urgent review if vision changes suddenly. Topical steroid therapy (prednisolone acetate 1%) is maintained for months to years, often for life in high-risk cases, to suppress rejection. Topical antibiotics are used for the first 1–2 months. Sutures remain in place for 12–24 months and are selectively removed under slit-lamp guidance to reduce astigmatism. Contact lens fitting for residual astigmatism can begin 12–18 months post-operatively once sutures are removed and the refraction is stable.