**5.4 Surgical interventions**

Surgical interventions in active HSV keratitis are limited to the severe stromal involvement with the increased risk of corneal perforation. Those may include: application of cyanoacrylate glue, amniotic membrane transplantation or therapeutic keratoplasty.

Other indications for surgical procedures include inactive corneal scarring after keratitis or cataract formation mainly due to prolonged treatment with topical steroids. Superficial opacifications could be considered as an indication for phototherapeutic keratectomy (PTK), although the corneal thinning is usual after HSV keratitis and therefore it limits the use of this method. The PTK ablation should always be limited to anterior one-third of stromal layers and leave a minimum residual stromal bed thickness (RSBT) of 250 μm to avoid further corneal ectasia. Also, spontaneous reactivation of HSV keratitis is well known after PTK, because laser ablation stimulates viral shedding in tears and reactivates the virus [49, 50].

When an extensive scar with corneal thinning is present a deep anterior lamellar keratoplasty (DALK) or penetrating keratoplasty (PK) should be considered. DALK eliminates the risk of endothelial immunologic rejection, but due to advanced corneal scarring and thinning may be difficult to perform. An obligatory preoperative assessment before keratoplasty procedures include the corneal sensitivity analysis and the exclusion of the active viral infection with neovascularization. It is well established, that the presence of deep stromal vascularization exceeding 2 or more quadrants, creates a significant risk for a graft immunologic rejection and graft failure. Another factor, strongly connected to the increased risk of the graft failure is a herpetic infection recurrence. To address those issues, the combination of the antiviral prophylaxis with the prophylaxis of a immunologic rejection should be implemented. Antiviral prophylaxis includes the use of high-dose oral acyclovir as recommended by American Academy of Ophthalmology (AAO guidelines recommended 800 mg 3 times daily for at least 1 year) [37]. The prophylaxis of a immunologic rejection includes usually systemic steroids combined with topical therapy. Despite the prophylaxis, there is a relatively high rate of graft failure performed in eyes after herpetic keratitis reported in the literature: 26% at 3 years, 15% at 5 years and 53.7% at 8 years [51–53]. In the last years, there have been an increasing interest in keratorosthesis surgery, as a viable option allowing a long term restoration of vision in patients with high risk for corneal transplantation. Boston type I keratoprosthesis (BKPro) is the most commonly implanted keratoprosthesis worldwide. BKPro was first used in 1965 by Professor Claes H. Dohlman [54, 55]. The BKPro surgery is usually complex with the high incidence of intraocular complications. Also the rate of postoperative complications is high and includes: glaucoma, retroprosthetic membrane formation, keratolysis, endophthalmitis, vitreoretinal complications, such as retinal detachment, cystoid macular edema, uveitis and hypotony/phthisis. In the latest study of the long term BKPro outcomes published in 2020, the probability of maintaining or improving vision was 75,0% at 5 years and 66,7% at 10 years [56].

In summary, surgical intervention in HSV keratits is challenging and high-risk procedure, therefore a special attention should be brought when referring such patients.
