DALK and PK Key Ingredients for Herpetic Keratitis

Italian doctors describe ways to optimise surgery. Howard Larkin reports from the 39th Congress of the ESCRS in Amsterdam. Both large diameter, 9.0 mm deep anterior lamellar keratoplasty (DALK) and two-piece microkeratome-assisted “mushroom” penetrating keratoplasty (PK) produced excellent long-term visual and survival outcomes for patients with herpetic keratitis, reported Angeli Christy Yu MD on behalf of Prof Massimo Busin MD. She recounted a case of a 13-year-old patient with corneal scarring associated with neovascularisation that initially improved with antiviral treatment. Afterwards, “mushroom” PK was performed as a definitive surgical procedure. He regained 20/20 vision which sustained over 10 years. Such outcomes are not always the case in conventional PK for herpetic keratitis. “We know herpetic keratitis often associated with deep stromal neovascularisation exceeding two quadrants poses a significant risk for immunologic rejection and subsequent graft failure,” Dr Yu said. Likewise, these patients are at high risk of herpetic disease recurrence. As a result, conventional PK for herpetic keratitis has a five-year success rate of about 60%. Long-term antiviral prophylaxis improves the odds of survival by reducing the risk of immunologic rejection and herpetic recurrence. Studies have found oral antiviral prophylaxis is effective for herpetic recurrence prevention, with oral doses ranging from 400 mg twice daily to 800 mg three to five times a day. The American Academy of Ophthalmology recommends high-dose antiviral prophylaxis as well. Dr Yu’s centre uses an initial high-dose oral acyclovir, topical ganciclovir and dexamethasone, and extended tapering of antiviral and steroid prophylaxis. When possible, Prof Busin’s group uses DALK for herpetic scarring. But when there is a significant macroperforation or unsatisfactory clearance within the optical zone because of a full-thickness opacity, PK is performed. OPTIMISING SURGERY Two-piece “mushroom” keratoplasty is designed to optimise the outcomes of full-thickness corneal transplantation, Dr Yu said. Studies show smaller-sized grafts lead to a lower rejection rate but higher refractive error, while larger grafts have higher rejection rates and lower refractive error. The two-piece “mushroom” graft consists of a large 9.0 mm diameter anterior lamella (mushroom “hat”) and a smaller 6.0 mm diameter posterior lamella (mushroom “stem”). This maximises the refractive benefit of a large anterior lamellar graft while minimising the risk of immunologic rejection by reducing the antigenic load, she explained. The procedure begins with a partial thickness trephination of 9.0 mm, followed by circumferential manual lamellar dissection. The residual bed is then trephined to the full thickness at 6.0 mm, usually centred on the pupil. The donor graft is split via microkeratome dissection into two lamellae, with the posterior lamella fitted into the central full-thickness trephination and the anterior graft sutured in place. In a study published in the American Journal of Ophthalmology last year, the group reported on 10-year outcomes of 52 eyes using standard two-piece microkeratome-assisted “mushroom” keratoplasty and a predefined antiviral prophylaxis protocol. All eyes were defined as high risk for recurrence based on the presence of at least two quadrants of neovascularisation. At 10 years, the graft junctions were imperceptible, with the cornea remodelling to its original form. Mean best-corrected vision was about 20/32, with 55% achieving 20/25 or better. After an initial loss of 40%, annual endothelial cell loss was 3%. The risk of rejection was 9.7% and recurrence 7.8%, with overall survival of 92%.i Similarly, 38 eyes that underwent DALK at the centre saw a stromal rejection rate of 6.6%, recurrence of 4.4%, and overall cumulative survival of 96%, Dr Yu reported. “You can always try pneumatic dissection first, which is successful in 70% of DALK cases. If a significant perforation does occur, you can convert to two-piece mushroom keratoplasty and still achieve excellent visual outcomes and, more importantly, survival rates of up to 90%,” she concluded. i AM J Ophthalmol 2020; 217: 212–223. Angeli Christy Yu MD is an ophthalmologist and researcher at the University of Ferrara, Italy, and Ospedali Privati Forlì “Villa Igea”. angeliyu@gmail.com

Tags: DALK, herpetic disease