New surgical techniques make acute hydrops in keratoconus a treatable disease
Prof Bjӧrn Bachmann MD PhD FEBO
Conservative treatments for hydrops in keratoconus patients are becoming obsolete with the advent of new surgical approaches such as compression sutures and mini-Descemet’s patch grafting, which can greatly reduce the duration of the condition, reports Prof Bjӧrn Bachmann MD PhD FEBO, University Hospital Cologne, Germany.
“Compression sutures and mini-DMEK contribute to a paradigm shift from conservative to surgical treatment of acute hydrops in keratoconus,” Prof Bachmann told the 24th ESCRS Winter Meeting in Marrakech, Morocco.
He noted that acute hydrops occurs in 2.5-to-3% of eyes with keratoconus and is unilateral in most cases. The condition usually occurs in the second and third decade and predominantly in male patients, as is the case with keratoconus. Spontaneous resolution of corneal oedema generally occurs between one and nine months.
Conservative treatments have long been the mainstay of treatment for corneal hydrops. However, they are mostly palliative in nature and generally do not shorten the duration of the condition. Furthermore, the conservative approach has a limited effect on the potential for complications, such as corneal scarring, which occurs in nearly all cases and will be extensive in some cases. In addition, hydrops occurring close to the limbal area can provoke severe corneal neovascularisation. Other potential complications include microbial keratitis and corneal perforation.
Bringing Descemet’s membrane and stroma
Hydrops in keratoconus results from a failure of the less flexible Descemet’s membrane to align with the inner surface of the ectatic stroma. The rupture and detachment of Descemet’s membrane allows the influx of aqueous humour into clefts within the stroma. Surgical treatments introduced in recent years are designed to bring the Descemet’s membrane and stroma back into alignment with each other or to patch the rupture with a small Descemet’s endothelial graft.
The first surgical approach to be introduced was intracameral injections octafluoropropane (CF38) gas at non-expanding concentration 14%. Research suggests that it can at best bring about a slow improvement in the condition. In a retrospective study, the mean time for resolution of the oedema was 78.7 days in 62 eyes that underwent intracameral C3F8injection and 117.9 days 90 eyes that received conservative treatment (p<0.0001) (Basu et al. Ophthalmology 2011;118:934-9). “The problem is if there is too much distance between the detached Descemet’s membrane and the corneal stroma. If you have a large tear in the membrane, the gas can just pass through the hole and fill up the space between Descemet’s and the corneal stroma and then you will have the opposite effect from what was intended,” Prof Bachmann said. A real step forward was compression sutures and intracameral gas tamponade technique, he noted. It involves drawing two-to-five full-thickness sutures with 10-0 nylon across the Descemet’s membrane tear to draw the ectatic stroma and the DM into conformation with each other. That is followed by the intracameral injection of C3F8 or SF6 gas in non-expanding concentrations. Patients undergo suture removal two to six weeks after surgery. In a study involving 15 acute hydrops keratoconus patients, average time for resolution of corneal oedema following the procedure was 8.87 days (Rajaram an et al, Cornea. 2009 Apr;28(3):317-20).
Marc Muraine MD later introduced a variation of the technique where the suture only extends though the stroma (Br J Ophthalmol 2015;99:773-7). The technique has also been combined with OCT guided drainage of acute hydrops, which helps clear the cornea even faster (Siebelmann et al, Cornea 2019).
A new approach in acute hydrops is the use of mini-DMEK grafts, sized 5.0mm or less, to patch the disrupted Descemet’s membrane. In a study he and his associates performed, four mini-DMEK procedures in three eyes of three patients, UCVA logMAR improved from 1.6 before to 1.2 after six-to-eight weeks. They had to repeat the procedure in one patient because the Descemet’s membrane of patient had so much tension the patch did not attach. They removed a piece of Descemet’s membrane from that patient. There was a partial detachment of graft without relapse of hydrops in two eyes.
Comparing Mini-DMEK vs compression sutures, Dr Bachmann noted that mini-DMEK has the advantage of eliminating any risk of suture loosening and leakage from the stitch canal. In addition. unlike compression sutures, mini-DMEK can treat massive oedema. Its main disadvantages are that it requires general anaesthesia and is a complex technique best performed with intraoperative optical coherence tomography (OCT). The main advantages of compression sutures are that it is an easy technique requiring no special equipment and can be performed with local anaesthesia. The main disadvantages with the technique are the risk of leakage and the risk of relapse in eyes with large amounts of oedema.
“Acute hydrops has become a treatable disease. In most patients surgical approaches rather than a purely conservative treatment is advisable. The new surgical treatments provide a rapid improvement in visual acuity and presumably results in less scar formation or vascularisation of the corneal stroma and reduce the risk of requiring a penetrating keratoplasty,” Prof Bachmann concluded.