Refractive corneal transplantation: control of astigmatism and ametropia during penetrating keratoplasty

Managing Post-Keratoplasty Astigmatism: High-Tech vs. Low-Tech Imaging Techniques for Guiding Suture Manipulation

Astigmatism is a visually significant condition that can develop after keratoplasty. The management of post-keratoplasty astigmatism can be performed both when transplant sutures are in place and when they have been removed. Fundamental for astigmatism management is its identification and characterization in terms of type, amount, and direction. Commonly, post-keratoplasty astigmatism is evaluated through corneal tomography or topo-aberrometry; however, many other techniques can be used in case these instruments are not readily available. Here, we describe several low-tech and high-tech techniques used for post-keratoplasty astigmatism detection in order to quickly understand if it contributes to low vision quality and to determine its characteristics. The management of post-keratoplasty astigmatism through suture manipulation is also described.

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.

An analysis of factors associated with graft topographic outcomes after deep anterior lamellar keratoplasty

PURPOSE

To investigate the correlations between preoperative, operative, and postoperative factors and corneal graft topographic parameters after deep anterior lamellar keratoplasty (DALK) performed in keratoconus-affected eyes.

METHODS

This prospective, interventional study enrolled 44 eyes. Graft topographic parameters, including keratometric astigmatism and the surface regularity index (SRI), were assessed after complete suture removal. Univariate analyses were used to evaluate the effects of preoperative factors (donor quality, donor and recipient age, keratoconus severity), operative factors (graft size, donor button roundness, roundness and centration of the donor-recipient junction), and postoperative factors (time point of suture removal) on postoperative topographic parameters.

RESULTS

The roundness of the donor-recipient junction after complete suture removal had a significant association with the roundness of the donor button after trephination (P = 0.04) and the amount of graft decentration relative to the limbus (P = 0.03). A significant correlation was found between the value of graft decentration relative to the limbus and postoperative keratometric astigmatism (P = 0.001) and between the roundness of the donor-recipient junction and the postoperative SRI (P = 0.02). The flat axis of the keratometric astigmatism and the longer axis of the graft lay in the direction of graft displacement. Other investigated factors had no significant association with postoperative topographic indices.

CONCLUSION

Graft displacement relative to the limbus and roundness of the donor-recipient junction were the main predictors of graft astigmatism and regularity, respectively, after DALK. Noncircularity of the donor button after trephination could increase the graft surface irregularity indirectly by influencing the roundness of the surgical wound.

Effects of corneal thickness distribution and apex position on postoperative refractive status after full-bed deep anterior lamellar keratoplasty

OBJECTIVE

To investigate the effects of corneal thickness distribution and apex position on postoperative refractive status after full-bed deep anterior lamellar keratoplasty (FBDALK).

METHODS

This is a retrospective analysis of patients who were diagnosed with advanced keratoconus between 2011 and 2014 in our hospital. The base of the cone in all patients did not exceed the central cornea at a 6-mm range. The FBDALK was performed by a same surgeon. All patients had a complete corneal suture removal and the follow-up records were intact. Patients who had graft-bed misalignment or who were complicated with a cataract or glaucoma were excluded. Uncorrected visual acuity (UCVA), best spectacle corrected visual acuity (BSCVA), and Pentacam examination data were recorded at two years postoperatively. The recorded data included the superior-inferior (S-I) and nasal-temporal (N-T) corneal thickness differences in 2, 4, 6, and 8 mm diameter concentric circles with the corneal apex as the center (S-I_{2 mm}, S-I_{4 mm}, S-I_{6 mm}, S-I_{8 mm}, N-T_{2 mm}, N-T_{4 mm}, N-T_{6 mm}, and N-T_{8 mm}), the linear, X-axis, and Y-axis distance between the corneal pupillary center and the cornea apex, total corneal astigmatism at a zone of 3 mm diameter from the corneal apex (TA_{3 mm}), the astigmatic vector values J₀ and J₄₅, and the corneal total higher-order aberration for 3 and 6 mm pupil diameters (HOA_{3 mm} and HOA_{6 mm}). Statistical analysis was performed by SPSS 15.0.

RESULTS

A total of 47 eyes of 46 patients met the criteria and were included in this study. The mean follow-up time was (28±7) months. The mean UCVA was 0.45±0.23 (logMAR) (MAR: minimum angle of resolution) and the mean BSCVA was 0.19±0.15 (logMAR), which were all significantly positively correlated with postoperative TA_{3 mm} and HOA_{3 mm}. The mean S-I corneal thickness differences were (44.62±37.74) μm, and the mean N-T was (38.57±32.29) μm. S-I_{2 mm} was significantly positively correlated with J₀ (r=0.31), J₄₅ (r=0.42), HOA_{3 mm} (r=0.37), and HOA_{6 mm} (r=0.48). S-I_{4 mm} and S-I_{8 mm} were significantly positively correlated with HOA_{3 mm} (r=0.30, r=0.40) and HOA_{6 mm} (r=0.46, r=0.35). The X-axis distance between corneal pupillary center and corneal apex was significantly positively correlated with J₄₅ (r=0.29).

CONCLUSIONS

In patients with advanced keratoconus after FBDALK, the unevenly distributed thickness at corneal pupillary area and the misalignment of corneal apex and pupillary center might cause significant regular and irregular astigmatism, which affected the postoperative visual quality.

Management of post-keratoplasty astigmatism

Post-keratoplasty astigmatism remains a challenge for corneorefractive surgeons. While maintaining a healthy graft is the most crucial issue in keratoplasty procedures, astigmatism is a limiting factor in the visual rehabilitation of otherwise successful corneal grafts. The management of post-keratoplasty astigmatism takes place at 2 stages: when sutures are still present at the graft-host junction and when all sutures have been removed. Excessive suture-in post-keratoplasty astigmatism is usually managed by selective suture manipulation, ie, suture adjustment and/or suture removal along the steep meridian of astigmatism. A small amount of suture-out post-keratoplasty astigmatism can be managed by spectacles. Higher magnitudes of astigmatism can be addressed by contact lenses or surgical intervention, such as relaxing and compressing procedures. Laser lamellar refractive surgery can also be used to manage post-keratoplasty astigmatism, and toric phakic intraocular lenses have recently been recommended. In this review, we discuss the etiology and management of post-keratoplasty astigmatism and provide recommendations and tips to minimize it.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Corneal wavefront errors 24 months after deep lamellar endothelial keratoplasty and penetrating keratoplasty

PURPOSE

To evaluate high-order aberrations (HOA) induced by the anterior corneal surface after deep lamellar endothelial keratoplasty (DLEK) and penetrating keratoplasty (PK).

DESIGN

Prospective, randomized clinical trial.

METHODS

Twenty-eight eyes of 25 patients with corneal edema resulting from Fuchs dystrophy underwent DLEK with a 9- to 10-mm incision (n = 13) or PK with double-running sutures (n = 15) at the Cornea Service, Mayo Clinic Department of Ophthalmology, Rochester, Minnesota. The main outcome measures were HOA from the anterior corneal surface calculated from corneal topography and decomposed into Zernike polynomials to the sixth order, high- and low-contrast visual acuity (VA), and contrast sensitivity. Variables after surgery were compared with those before surgery and between treatments by using generalized estimating equation models with Bonferroni adjustment.

RESULTS

Total HOA through 24 months (0.48 +/- 0.15 microm) after DLEK was similar to total aberration before surgery (0.44 +/- 0.23 microm; P = .10). After PK, total HOA remained elevated through 24 months (1.68 +/- 0.58 microm) compared with that before surgery (0.49 +/- 0.27 microm; P < .005) and compared with that after DLEK (P < .006). At 24 months after PK, corneas with sutures removed had greater total HOAs than corneas with sutures intact (1.90 +/- 0.52 microm vs 1.18 +/- 0.33 microm; P = .001). High- and low-contrast VA and contrast sensitivity at 24 months after PK did not correlate with any HOA.

CONCLUSIONS

HOAs from the anterior corneal surface were higher after PK compared with after DLEK but did not correlate with visual function after PK.

Evaluation of techniques of single continuous suturing in penetrating keratoplasty

AIM

To evaluate the three techniques of single continuous suturing-namely, torque, antitorque, and no torque in penetrating keratoplasty.

METHODS

53 eyes of 53 patients underwent penetrating keratoplasty using torque (17 patients), antitorque (18 patients), and no torque (18 patients) suturing techniques in this prospective study. Patients were followed up at 4 weeks, 3 months, and 6 months. Keratometric, videokeratographic, refractive astigmatism, and best corrected visual acuity were determined in all the three groups at each follow up visit. Post-keratoplasty suture adjustment was done at 4 weeks, if the astigmatism was >3 dioptres.

RESULTS

The initial astigmatism in the torque group was higher than in the other two groups, although it was not statistically significant. Following suture adjustment, there was a significant decrease in astigmatism in all the three groups (p<0.0001). However, no significant difference in the postoperative astigmatism at 3 months and at 6 months was seen among the three groups.

CONCLUSIONS

The three techniques of single continuous suturing-that is, torque, antitorque, and no torque produce a similar final astigmatic results. Suture adjustment is an effective method of reducing post-penetrating keratoplasty astigmatism.

Combined interrupted and continuous versus single continuous adjustable suturing in penetrating keratoplasty: a prospective, randomized study of induced astigmatism during the first postoperative year

OBJECTIVE

To compare postoperative astigmatism induced by two different suturing techniques in penetrating keratoplasty (PKP).

DESIGN

A monocenter, prospective, randomized clinical trial with a longitudinal 1-year follow-up.

PARTICIPANTS

A total of 95 eyes undergoing PKP were randomized into 2 groups. Of these, 51 eyes were allocated to the combined interrupted and continuous suturing group (ICS) and 44 eyes to the single continuous adjustable suturing (SCAS) group.

INTERVENTION

In the ICS group, suturing was with a combination of 12 interrupted 10-0 nylon and 1 continuous 11-0 nylon sutures. Eyes in the SCAS group had been sutured with a single running 24-bite 10-0 nylon. Selective suture removal started no earlier than 10 weeks after surgery; suture adjustment could start as soon as possible after surgery.

MAIN OUTCOME MEASURES

Astigmatism was measured by topography, keratometry, and refraction at 3-, 6-, 9-, and 12-month postoperative intervals.

RESULTS

The difference in mean time of suture manipulation between groups was significant (P = 0.0001), with the SCAS starting earlier. A significant decrease in astigmatism occurred by either interrupted suture removal (6.69 +/- 3.11 diopter [D] before to 4.76 +/- 2.99 D after, P = 0.0002) or suture adjustment (7.18 +/- 3.12 D before to 4.46 +/- 3.24 D after, P = 0.0001). However, the net astigmatic reduction in the SCAS group was not significantly greater (P = 0.250) than in the ICS group. Vector change was 7.40 +/- 4.17 D and 6.28 +/- 4.14 D for SCAS and ICS, respectively (P = 0.13). At no interval (3, 6, 9, or 12 months) was there significant difference in astigmatism between the two groups. Refractive astigmatism (cyl, D) at 1 year was 2.66 +/- 1.70 for the ICS and 3.12 +/- 2.62 for the SCAS, but there was no significant treatment effect (P = 0.945). Furthermore, 66% of the ICS eyes and 58% of the SCAS eyes (P = 0.295) were within the astigmatic target of the study (<3.5 D).

CONCLUSIONS

Postkeratoplasty astigmatism can be decreased similarly with either adjustment of a single running suture or selective removal of interrupted sutures. No advantage of the SCAS over ICS in terms of fewer manipulations or less astigmatism was seen as suggested previously.

Videokeratoscopy of recipient peripheral corneas in combined penetrating keratoplasty, cataract extraction, and lens implantation

PURPOSE

We performed a prospective clinical trial to evaluate computerized videokeratoscopic analysis of the peripheral recipient cornea in intraocular lens power calculations for triple procedures: penetrating keratoplasty, cataract extraction, and intraocular lens insertion.

METHODS

Patients with Fuchs' dystrophy underwent consecutive triple procedures. Surgery was performed in 16 eyes by a single surgeon (O.N.S.) using a single technique. If videokeratoscopic analysis disclosed dioptric powers greater than 40 diopters in the circumference of the corneal map, the surgeon's average postoperative central corneal power of 46 diopters was used with the regression formula. If dioptric powers less than 40 diopters were detected in the circumference of the corneal map, 45 diopters was used to avoid postoperative hyperopic shifts and to decrease deviation from intended refractive error. Refraction and videokeratoscopic analysis were performed six months after suture removal (18 to 24 months postoperatively).

RESULTS

Analysis of covariance demonstrated that preoperative peripheral videokeratoscopic data of the recipient cornea correlated (P = .0001) with postoperative central corneal power, whereas preoperative central corneal power of the recipient cornea did not correlate (P = .35). Deviation from intended refraction (range, -2.54 to +1.22 diopters) was within 2 diopters in 14 eyes (88%) and within 3 diopters in all eyes. No patients had anisometropia greater than 3 diopters.

CONCLUSION

Preoperative data from computerized videokeratoscopic analysis of the recipient peripheral cornea correlated with postoperative central corneal power, and improved postoperative refractive outcomes compared with previously reported results of triple procedures.