Jack Parker

Treatment options for advanced keratoconus: A review

Traditionally, the mainstay of treatment for advanced keratoconus (KC) has been either penetrating or deep anterior lamellar keratoplasty (PK or DALK, respectively). The success of both operations, however, has been somewhat tempered by potential difficulties and complications, both intraoperatively and postoperatively. These include suture and wound-healing problems, progression of disease in the recipient rim, allograft reaction, and persistent irregular astigmatism. Taken together, these have been the inspiration for an ongoing search for less troublesome therapeutic alternatives. These include ultraviolet crosslinking and intracorneal ring segments, both of which were originally constrained in their indication exclusively to eyes with mild to moderate disease. More recently, Bowman layer transplantation has been introduced for reversing corneal ectasia in eyes with advanced KC, re-enabling comfortable contact lens wear and permitting PK and DALK to be postponed or avoided entirely. We offer a summary of the current and emerging treatment options for advanced KC, aiming to provide the corneal specialist useful information in selecting the optimal therapy for individual patients.

Causes of Glaucoma After Descemet Membrane Endothelial Keratoplasty

PURPOSEnTo describe the incidence and causes of glaucoma after Descemet membrane endothelial keratoplasty (DMEK).nnnDESIGNnNonrandomized prospective cohort study at a tertiary referral center.nnnMETHODSnThe incidence of glaucoma was evaluated in the first 275 consecutive eyes that underwent DMEK for Fuchs endothelial dystrophy (260 eyes) or bullous keratopathy (15 eyes). Glaucoma was defined as a postoperative intraocular pressure (IOP) elevation of ≥24 mm Hg, or ≥10 mm Hg from the preoperative baseline. If possible, the cause of glaucoma was identified, and best-corrected visual acuity (BCVA), endothelial cell density (ECD), and postoperative course were documented, with a mean follow-up of 22 (± 13) months.nnnRESULTSnOverall, 18 eyes (6.5%) showed postoperative glaucoma after DMEK. Seven eyes (2.5%) had an exacerbation of a pre-existing glaucoma. Eleven eyes (4%) presented with a de novo IOP elevation, associated with air bubble-induced mechanical angle closure (2%), steroid response (0.7%), or peripheral anterior synechiae (0.4%), or without detectable cause (0.7%). Two eyes (0.7%) required glaucoma surgery after DMEK. At 6 months, all eyes had a BCVA of ≥20/40 (≥0.5), and 81% reached ≥20/25 (≥0.8) (n = 16); mean ECD was 1660 (± 554) cells/mm(2) (n = 15) (P > .1).nnnCONCLUSIONnGlaucoma after DMEK may be a relatively frequent complication that could be avoided by reducing the residual postoperative air bubble to 30% in phakic eyes, applying a population-specific steroid regime, and avoiding decentration of the Descemet graft. Eyes with a history of glaucoma may need close IOP monitoring in the first postoperative months, especially in eyes with an angle-supported phakic intraocular lens.

Identifying causes for poor visual outcome after DSEK/DSAEK following secondary DMEK in the same eye

Purpose:u2002 To identify causes of reduced visual acuity after Descemet stripping (automated) endothelial keratoplasty (DSEK/DSAEK) and to determine whether such eyes can be successfully ‘repaired’ with a secondary Descemet membrane endothelial keratoplasty (DMEK).

Midstromal Isolated Bowman Layer Graft for Reduction of Advanced Keratoconus: A Technique to Postpone Penetrating or Deep Anterior Lamellar Keratoplasty

Midstromal implant of an isolated Bowman layer graft is a new approach to reduce ectasia in eyes with advanced keratoconus. The procedure should postpone penetrating or deep anterior lamellar keratoplasty. Ten eyes of 9 patients with progressive, advanced keratoconus and contact lens intolerance underwent the procedure with no intraoperative adverse events. Throughout the study period, we observed no complications related to stromal dissection and/or the Bowman layer graft. Maximum corneal power decreased from a mean (SD) of 74.5 (7.1) diopters (D) before to 68.3 (5.6) D after surgery (Pu2009=u2009.002). Hence, implant of an isolated Bowman layer graft may offer a safe and effective new technique to reduce ectasia in eyes with advanced keratoconus, potentially allowing continued long-term contact lens wear. The low risk of complications may render the procedure suitable as a treatment to postpone penetrating or deep anterior lamellar keratoplasty in cases with impending contact lens intolerance and/or corneal scarring (clinicaltrials.gov Identifier: NCT01686906).

Preliminary outcome of hemi-Descemet membrane endothelial keratoplasty for Fuchs endothelial dystrophy

Background/aims To evaluate the clinical outcome of a full-diameter, untrephined, semicircular Descemet graft in a consecutive series of Descemet membrane endothelial keratoplasty (hemi-DMEK), potentially allowing the harvesting of two grafts from a single donor corneoscleral rim. Methods Interventional case series of 10 eyes of 10 patients with Fuchs endothelial dystrophy. Best corrected visual acuity (BCVA), endothelial cell density (ECD) and central corneal thickness (CCT) were evaluated up to 6u2005months postoperatively, and intraoperative and postoperative complications were recorded. Results Hemi-DMEK was successful in 9 out of 10 eyes; one eye showed persistent graft detachment despite rebubbling and underwent a secondary DMEK. BCVA improved in all successful hemi-DMEK eyes: at 6u2005months 100% of eyes (n=7) reached ≥20/40 (≥0.5), 86% (n=6) ≥20/25 (≥0.8), 29% (n=2) ≥20/20 (≥1.0) and 14% (n=1) reached 20/17 (≥1.2). Two eyes were excluded from visual analysis due to low visual potential. Preoperative donor ECD declined from 2744 (±181) cells/mm2 to 940 (±380) cells/mm2 centrally at 6u2005months postoperatively (n=9), with (donor and/or host) endothelial cell redistribution over bare stromal areas adjacent to the graft. Average CCT decreased from 745 (±153) µm preoperatively to 520 (±37) µm at 6u2005months. Four eyes required rebubbling for visually significant graft detachment. No other complications occurred throughout the study period. Conclusions Hemi-DMEK may give visual outcomes similar to those in conventional DMEK. If ECD decrease and graft detachment rate would prove acceptable in larger series, hemi-DMEK could have the potential to double the availability of donor tissue for endothelial keratoplasty.

Bowman layer transplantation: 5-year results

PurposeThe purpose of this study was to evaluate the 5-year clinical results of isolated Bowman layer (BL) transplantation in the treatment of advanced keratoconus.MethodsIn this prospective, single-center, interventional case series at a tertiary referral center, 20 eyes of 17 patients with advanced keratoconus underwent BL transplantation, i.e. an isolated Bowman layer graft was positioned into a manually dissected mid-stromal pocket. Scheimpflug-based corneal tomography measurements, best corrected spectacle and contact lens visual acuities (BSCVA and BCLVA), endothelial cell density, and complications were evaluated up to 5xa0years after surgery.ResultsMeasured simulated and maximum keratometry (Kmean and Kmax) values were stable up to 5xa0years after surgery (Pu2009=u2009.310 and Pu2009=u2009.195 for 5xa0years compared to 1xa0month follow-up, respectively), following an initial decrease from pre- to 1xa0month postoperatively (Pu2009<u2009.001 each). Mean LogMAR BSCVA remained stable (Pu2009>u2009.99), after an initial improvement from pre- to 12xa0months postoperatively (Pu2009=u2009.007). Mean BCLVA did not change from preoperative to 5xa0years postoperatively (Pu2009=u2009.219). During all postoperative follow-ups, mean densitometry values were higher than preoperatively (Pu2009<u2009.001). A corneal hydrops occurred in one eye at 4.5xa0years postoperatively; no other postoperative complications were observed. Kaplan-Meier analysis showed an estimated success rate of 84% at 5xa0years postoperatively. Endothelial cell density remained stable from before to 5xa0years after surgery (Pu2009=u2009.319).ConclusionsAfter early postoperative corneal flattening, topographies were stable up to 5xa0years after BL transplantation, preserving BCLVA and contact lens tolerance, potentially allowing long term postponement of penetrating or deep anterior lamellar keratoplasty.

Validity of Bowman layer transplantation for keratoconus: visual performance at 5-7 years

more retinal harm than red laser pointers (Xu et al. 2016). Safety-regulated hand-held lasers have a power output of <5 milliwatts (mW). One retinalinjury-implicated green laser had an output of 42 mW (Raoof et al. 2014). Laser-induced maculopathy may resemble macular dystrophy (Zhang et al. 2016), and children may be reluctant to admit to the mechanism of injury delaying the diagnosis (Raoof et al. 2014). Development of CNV is a rare but serious complication. In our case, CNV was treated successfully with intravitreal anti-VEGF with no reactivation during 4-year follow-up. The outer retina partially recovered over the years, and the boy kept driving licence vision in both eyes, but will require lifetime ophthalmological monitoring for CNV. We wish to raise awareness of the danger of imported laser ‘toys’ of uncertain safety classification.

Technical feasibility of isolated Bowman layer graft preparation by femtosecond laser: a pilot study

Purpose To evaluate the technical feasibility of isolated Bowman layer (BL) graft preparation by femtosecond laser (FSL) and to compare the ultrastructural morphology to manually dissected grafts. Methods Five whole globes were placed in custom-made eye holders and debrided of epithelium. After programming a dissection depth of 20 μm, the FSL was docked into position and 5 isolated BL grafts were created. From 5 additional globes, corneoscleral buttons were procured, mounted in artificial anterior chambers, and stripped of BL via the previously described manual technique. Three specimens from both series were randomly selected and assigned to transmission electron microscopy for ultrastructural evaluation and thickness measurements. Results All dissections were uneventful and 10 total grafts were produced: 5 by FSL and 5 by manual dissection. Mean graft thickness was 37 (±8.6) μm (n = 3) for the FSL group and 11.7 (±1.6) μm (n = 3) for the manually dissected group. Transmission electron microscopy revealed a thick but relatively smooth posterior cut edge in the FSL group, versus a virtually isolated BL with irregular rests of dispersed stroma in the manually dissected group. Conclusions Femtosecond laser may have potential for harvesting intact BL and with a smooth posterior surface, but accompanied by variable amounts of anterior stroma owing to technical limitations.

Manual mid-stromal dissection as a low risk procedure to stabilize mild to moderate progressive keratoconus

BackgroundTo evaluate the efficacy of manual mid-stromal dissection in stabilizing progressive keratoconus.MethodsSurgeries were performed in 16 eyes of 14 patients with progressive keratoconus. All eyes were examined before and at 1xa0day, 1xa0week, 1, 3, 6 and 12xa0months after surgery, and every 6xa0months thereafter. Pentacam (simK, Kmax and pachymetry), best corrected visual acuity (BCVA) and subjective refraction were recorded up to the latest follow-up visit (mean follow-up time 6.6u2009±u20092.4xa0years).ResultsAll surgeries were uneventful, and no postoperative complications occurred. Keratometry values (nu2009=u200915) stabilized in 6/11 eyesxa0(55%) with a preoperative Kmax <u200960.0 diopter (D), while all eyes >u200960 D showed continued progression. In 11/15 eyesxa0(73%) pachymetry was unchanged. BCVA with spectacles remained stable in 7/12 eyesxa0(58%) and improved ≥2 Snellen lines in 5/12 eyesxa0(42%). BCVA with a contact lens remained stable in 4/9 eyesxa0(44%), improved ≥2 Snellen lines in 3/9 eyesxa0(33%) and deteriorated inxa02/9 eyesxa0(22%).ConclusionsManual mid-stromal dissection was effective in 50% of keratoconic corneas with Kmax values <u200960 D and may be considered in cases ineligible for other interventions such as UV-crosslinking, stromal ring implantation or Bowman layer transplantation. An advantage of the procedure may be that the tissue is unaltered and that no synthetic or biological implant is required.

Unfolding Techniques for the DMEK Graft

In Descemet membrane endothelial keratoplasty (DMEK), graft unfolding is often perceived as the most difficult step and the most challenging to learn [1–3]. Of course, the best way to learn anything is by practice, and for DMEK surgery, there exist both an animal eye model [4] and a method for simulating the operation using an artificial anterior chamber (which is how we teach graft unfolding at our wet-lab courses). Beginning surgeons may also be comforted to know that most clinical outcomes during the “learning curve” of the operation approximate those obtained by more experienced hands [5–7].