Small Incision Lenticule Extraction for Postkeratoplasty Myopia and Astigmatism

[Surgical technique of keratoplasty with simultaneous implantation of a continuous ring or ring segment into the graft]

The article presents the surgical technique of penetrating keratoplasty (PK) and deep anterior lamellar keratoplasty (DALK) with femtosecond-laser assistance involving simultaneous implantation of an intracorneal continuous ring (ICCR) or an intracorneal ring segment (ICRS) into the graft. Surgical technique no. 1 - keratoplasty with simultaneous implantation of ICRS. Intrastromal circular tunnel is formed in the central zone of donor cornea using femtosecond laser. Then penetrating trepanation 8.1 mm in diameter is performed symmetrically to the formed tunnel. After preparing penetrating or lamellar recipient bed, suture fixation is placed in the corneal transplant, then the ICRS is implanted into the graft. Surgical technique no. 2 - keratoplasty with simultaneous implantation of ICCR. The donor cornea is dissected from periphery to center using femtosecond laser. Central zone remains untouched. A large diameter full-thickness trepanation is performed and the donor cornea is divided into the anterior and posterior layers. The ICCR is put on the donor cornea while holding the posterior layer with forceps. Penetrating or lamellar recipient bed is prepared, then the corneal graft is fixed with sutures. Transparent corneal graft acceptance does not guarantee high visual acuity due to post-keratoplasty astigmatism. Surgical correction of astigmatism is performed in the long term post-operatively and isn't effective enough. We proposed this new surgical technique of keratoplasty with simultaneous implantation of ICCR and ICRS into the graft as close as possible to the visual axis of the eye, which can help make the postoperative astigmatism minimal both immediately after surgery and in the long term. The study proposes a new approach to intraoperative prevention of post-keratoplasty astigmatism. The technique is simple, safe and effective. Analysis of long-term outcomes is required before recommending this method for widespread use in clinical practice.

SMILE after DALK to reduce residual refraction: two-year results

PURPOSE

To determine the two-year results of small incision lenticule extraction (SMILE) for correcting post-keratoplasty myopia and myopic astigmatism.

METHODS

In this case-series study, 10 eyes of 10 patients with a 6- to 10-year history of successful deep lamellar keratoplasty (DALK) underwent SMILE using the VisuMax laser platform. Ophthalmologic examinations and visual acuity and refraction measurement were taken pre- and 1, 3, 6, 12, and 24 months postoperatively. The Pentacam and Sirius imaging were done in the first and last follow-up sessions.

RESULTS

The mean age of the patients was 39.60 ± 7.86 years. Six subjects were male. Two years after SMILE, the mean improvement in UDVA and CDVA was 3.60 ± 1.84 (P < 0.001) and 1.60 ± 2.91 (P = 0.231) LogMAR, respectively. The mean decrease in spherical equivalent, spherical error, and cylinder power was 1.92 ± 1.96 diopter (D) (P = 0.013), 0.70 ± 3.05D (P = 0.213), and 2.42 ± 2.91D (P = 0.024), respectively. The vector mean target-induced astigmatism, surgical-induced astigmatism, and difference vector were 1.30D@44˚, 1.11D@24˚, and 0.86D@73˚, respectively. Two years after SMILE, vertical coma, horizontal coma, and spherical aberration increased by 0.44 ± 0.51, 0.23 ± 0.32, and 0.02 ± 0.16 µm, respectively, (all P > 0.05) while trefoil reduced by 0.29 ± 0.75 µm (P = 0.428).

CONCLUSION

SMILE can be an effective procedure for reducing refraction and astigmatism after DALK in patients with moderate myopia and moderate to severe astigmatism and improves the visual acuity in these patients. Axis rotation during surgery may result in under-correction of astigmatism. Refinement of SMILE treatment nomogram for post-DALK cases seems necessary.

Post-penetrating keratoplasty astigmatism

Postoperative astigmatism is one of the common complications affecting visual outcomes after a penetrating keratoplasty. It can result from various factors related to host, donor and surgical technique, resulting in suboptimal visual outcome. While some of the measures taken during preoperative planning and during actual surgery can reduce the magnitude of postoperative astigmatism, postoperative correction of astigmatism is often required in cases with high degrees of astigmatism. When spectacles and contact lenses fail to provide optimal visual outcomes, various surgical techniques that include astigmatic keratotomy, compression sutures, toric intraocular lens placement, and laser refractive procedures can be considered. When none of these techniques are able to achieve a desired result with in the acceptable optical range, a repeat keratoplasty is considered a last option. We discuss the various causes and management of complication of postoperative astigmatism occurring after a full thickness corneal transplantation surgery.

Intrastromal Lenticule Rotation for Treatment of Astigmatism Up to 10.00 Diopters Ex Vivo in Human Corneas

PURPOSE

To evaluate the feasibility of intrastromal lenticule rotation (ISLR) as a novel technique for management of astigmatism up to 10.00 diopters (D).

METHODS

Eighteen human donor corneas were mounted on an artificial anterior chamber. After laser application and dissection, the lenticule was rotated 90° in the intrastromal pocket. Scheimpflug tomography (Pentacam HR; Oculus Optikgeräte GmbH, Wetzlar, Germany) was acquired preoperatively and following ISLR. The attempted astigmatic correction was twice the cylindrical magnitude of the lenticule referenced to the corneal plane: 4.80 D (5.00 D group, n = 9) and 9.32 D (10.00 D group, n = 9), respectively. The change in keratometric astigmatism was evaluated by vector analysis.

RESULTS

In the 5.00 D group, ISLR caused a mean absolute surgical induced astigmatism (SIA) of 5.30 ± 1.14 D with a correction index (CI) of 1.14 ± 0.25 and an angle of error (AoE) of -0.80° ± 4.61°. In the 10.00 D group, the SIA averaged 9.57 ± 1.10 D with a CI of 1.03 ± 0.12 and an AoE of 2.75° ± 3.60°. The average total corneal refractive power (TCRP) increased 1.36 ± 0.67 and 1.95 ± 1.57 D in the 5.00 D and 10.00 D groups, respectively. Postoperative optical coherence tomography revealed stromal redistribution in the periphery of the optical zone with tissue addition in the preoperative steep meridian and tissue reduction in the preoperative flat meridian.

CONCLUSIONS

ISLR seemed feasible and precise for management of regular astigmatism up to 10.00 D ex vivo in human donor corneas. A myopic shift was observed in TCRP. The in vivo corneal remodeling after ISLR warrants investigation. [J Refract Surg. 2019;35(7):451-458.].