Intraoperative cauterization of the cornea can reduce postkeratoplasty refractive error in patients with keratoconus

Comparison of penetrating keratoplasty outcomes with or without microwave thermokeratoplasty

Microwave thermokeratoplasty (MTK) is a surgical procedure for the correction of pathologic corneal steepening. The purpose of this study was to examine the postoperative outcomes of eyes with advanced keratoconus that underwent femtosecond-laser zig-zag penetrating keratoplasty (z-PK) following MTK for reshaping of the central cornea. This study involved 32 eyes of 32 consecutive advanced keratoconus patients; i.e., 25 eyes of 25 patients who underwent MTK prior to z-PK (MTK + z-PK group), and 7 eyes of 7 patients who underwent z-PK alone (z-PK group). In all treated eyes, visual acuity (VA) and corneal topography were measured before surgery and at 6-months postoperative. At 6-months postoperative, the mean uncorrected distance VA (logarithm of the minimum angle of resolution) and surface regularity index (SRI) of the MTK + z-PK group was 0.62 ± 0.39 (mean ± standard deviation) and 1.26 ± 0.45, respectively, while that in the z-PK group was 1.02 ± 0.18 and 7.64 ± 3.22, respectively. Both variables were significantly better in the MTK + z-PK group than in the z-PK group (P < 0.05). The findings in this study reveal that MTK prior to z-PKP is effective for improving UDVA and reducing the irregularity of corneal topography in patients with advanced keratoconus.

Astigmatism Orientation After Deep Anterior Lamellar Keratoplasty for Keratoconus and Its Correlation With Preoperative Peripheral Corneal Astigmatism

PURPOSE

To evaluate the orientation of keratometric astigmatism (KA) after deep anterior lamellar keratoplasty (DALK) for keratoconus and its correlation with preoperative peripheral KA.

METHODS

This is a retrospective, single-center observational study including keratoconic patients undergoing DALK between January 2016 and January 2017 with regular astigmatism postoperatively. The orientation of postoperative KA was classified as with-the-rule (WTR), against-the-rule, or oblique and was correlated with the corresponding preoperative peripheral KA, calculated by the sinusoidal fitting of points of the axial keratometric power map at 8 mm diameter.

RESULTS

Forty-one keratoconic eyes were included, with the most common orientation of KA post-DALK being WTR (65.9%), followed by against-the-rule (19.5%) and oblique (14.6%). A significant correlation was found between preoperative peripheral KA and post-DALK KA regarding axis (P < 0.001, r = 0.88) and power (P = 0.0128, r = 0.23).

CONCLUSIONS

The axis of post-DALK astigmatism and to a lesser extent its respective power in keratoconic eyes can be predicted using the preoperative peripheral KA, with "WTR" being the most common astigmatic orientation.

Vitreous cavity length in keratoconus: implications for keratoplasty

PurposeTo compare axial length (AL) with vitreous cavity length (VCL) in patients with keratoconus and to ascertain whether graft size can be tailored to reduce myopic refractive error in patients with keratoconus undergoing penetrating keratoplasty (PK).Patients and methodsThe AL and VCL were measured prospectively in patients with keratoconus not undergoing PK (Group 1) and in normal phakic, emmetropic individuals (Group 2). A retrospective analysis of these measurements in patients with keratoconus who had undergone PK (Group 3) was also performed. The postoperative spherical equivalent (SE) was then correlated to size of donor buttons.ResultsKeratoconus patients tended to have a longer mean VCL than emmetropic normal individuals. The mean VCL of these patients (Group 1) was 16.49 mm±SD 1.13 compared to the mean VCL of 15.94 mm±SD 0.56 in normals (Group 2, P<0.0001). Patients with keratoconus who had an undersized graft showed reduced myopic refractive error compared to those with same size or oversized grafts.ConclusionVCL measurement is more accurate than AL measurement in deciding upon graft-host size disparity for corneal graft in patients with keratoconus. In patients with increased VCL, undersizing the donor button helps in reducing postoperative myopia. We recommend VCL measurement as part of the routine workup in all keratoconus patients undergoing corneal transplants.

A Review of Randomized Controlled Trials of Penetrating Keratoplasty Techniques

PURPOSE

To assess the effects of variations in operative technique on the outcomes of penetrating keratoplasty (PK).

METHOD

Systematic literature review of published randomized controlled trials of operative techniques in PK.

MAIN OUTCOME MEASURES

Visual acuity, refractive error, endothelial cell density, graft rejection, intraocular pressure (IOP), and other surgical complications.

RESULTS

Twenty-seven trials were identified. Many involved small numbers, some of which were probably compromised by inadequate statistical power. There was some limited evidence from a small number of studies (usually 1 or 2) for preoperative cauterization of the cone in keratoconus, excimer laser trephination, taking into account the effect of trephine sizing on postoperative IOP, taking into account the effect of trephine sizing on postoperative spherical equivalent, using sodium hyaluronate, avoiding vitrectomy if possible, using an iris-fixated posterior chamber lens implant in the absence of capsular support, and adjusting a single continuous suture intraoperatively if used. However, there was little convincing evidence for choosing interrupted suturing versus continuous suturing or for an effect of suturing on final sutures-out astigmatism. Likewise, there was no convincing evidence for the superiority of any lamellar alternative to PK for deep stromal disease. Overall, most of the effects of changing technique were small, and there was no evidence for the superiority of any specific technique in terms of improved quality of life or cost-effectiveness.

CONCLUSIONS

There is a need for further studies with which to refine decision-making as regards the choice of operative techniques in PK.

Management of keratoconus with Intacs

PURPOSE

To prospectively study the effects of the use of Intacs microthin prescription inserts for the management of keratoconus.

DESIGN

Prospective nonrandomized clinical trial.

METHODS

Thirty-three eyes of 26 keratoconus patients (17 males and 9 females) ages 21 to 51 years (mean age, 32 +/- 9.7 years) were included in the current study. All patients had clear central corneas and contact lens intolerance. Patients were excluded if any of the following criteria applied after the preoperative examination: previous intraocular or corneal surgery; history of herpes keratitis; diagnosed autoimmune disease; and systemic connective tissue disease. Two Intacs segments of 0.45-mm thickness were inserted in the cornea of each eye, aiming at embracing the keratoconus area to try to achieve maximal flattening. Preoperative examination included uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), manifest refraction, keratometric data, and corneal topography.

RESULTS

Intacs were successfully implanted in all eyes. In one eye Intacs were removed after 3 months because of their improper (superficial) placement. The follow-up ranged from 1 to 24 months (mean: 11.3 months). The mean UCVA significantly improved from 0.13 +/- 0.14 (range, counting fingers [CF]-0.5) to 0.39 +/- 0.27 (range, CF-1.0) (P <.01). Of 33 eyes, 2 eyes lost 1 line of UCVA, and 3 eyes maintained the preoperative UCVA, whereas the rest (28 eyes) experienced a 1- to 10-line gain. The mean BCVA also improved from 0.47 +/- 0.31 (range, CF-1.0) to 0.64 +/- 0.26 (range, 0.1-1.0) (P <.01). Of 33 eyes, 4 eyes experienced 1- to 2-line loss of BCVA, 4 eyes maintained the preoperative BCVA, whereas the rest (25 eyes), experienced a 1- to 6-line gain. Of 3 patients (3 eyes) with unsatisfactory results, 1 patient improved with one segment removal and in 2 patients the segments were permanently removed. One of these eyes underwent successful PKP.

CONCLUSIONS

With mean follow-up of 11.3 months, intracorneal ring segments implantation improved UCVA and BCVA in the majority of the keratoconus patients. Even though the results are encouraging, concern still exists regarding the predictability as well as the long-term effect of such an approach for the management of keratoconus.

Deep lamellar keratoplasty: surgical techniques for anterior lamellar keratoplasty with and without baring of Descemet's membrane

PURPOSE

To review current techniques used in deep anterior lamellar keratoplasty (LKP), and to describe a novel approach that facilitates baring of Descemet's membrane (maximum depth anterior lamellar keratoplasty).

METHODS

A highly selective review of the literature is presented, with descriptions of different techniques in the light of the authors' personal experience over 3 decades. A novel method for baring Descemet's membrane is detailed. It involves air injection in such a way that a large bubble is created between stroma and Descemet's membrane. Visual results of this operation in patients with keratoconus are reviewed.

RESULTS

Visual results 6 months after maximum depth anterior LKP in 181 eyes with keratoconus are comparable with those resulting from penetrating keratoplasty: 89% achieved a best spectacle-corrected visual acuity of 20/40 or better, and 10% achieved 20/20 or better. Intraoperative perforation occurred in 9% of cases.

CONCLUSIONS

Maximum depth anterior LKP has some important advantages when compared with other types of anterior lamellar keratoplasty or penetrating keratoplasty, but it remains a challenging procedure. A new technique considerably facilitates this operation and reduces intraoperative complications.