Topographic analysis of corneal regularity after 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.

Systematic review and meta-analysis of femtosecond laser-enabled keratoplasty versus conventional penetrating keratoplasty

PURPOSE

The aim of this meta-analysis is to compare femtosecond laser-enabled keratoplasty with conventional penetrating keratoplasty regarding postoperative astigmatism, visual functions, graft rejection, graft failure, and complications.

METHODS

Eligible studies were retrieved from five mainstream electronic databases, including PubMed, Embase, Ovid MEDLINE, Cochrane Library, and ClinicalTrial.gov. Postoperative topographic astigmatism was set as the primary outcome, and best-corrected visual acuity, spherical equivalent, endothelial cell density, graft rejection, graft failure, and complications were chosen as the secondary outcomes. Standard mean difference and risk ratio were the size effects for continuous data and binomial data, respectively. The data were pooled through either the random-effects model or the fixed-effects model based on data heterogeneity. Moreover, subgroup analyses were conducted when the heterogeneity occurred distinctly (I² > 50%).

RESULTS

A total of seven comparative studies were included. The pooled standard mean difference (-0.32, 95% confidence interval: -0.74 to 0.10) showed that femtosecond laser-enabled keratoplasty was not superior over conventional penetrating keratoplasty to decrease postoperative topographic astigmatism (p = 0.14). However, best-corrected visual acuity after femtosecond laser-enabled keratoplasty was significantly better than that after conventional penetrating keratoplasty (p = 0.00, standard mean difference: -0.23, 95% confidence interval: -0.37 to -0.10). Furthermore, endothelial cell density after femtosecond laser-enabled keratoplasty was preserved significantly better (p = 0.03, standard mean difference: 0.63, 95% confidence interval: 0.07-1.20). Moreover, spherical equivalent, graft rejection, graft failure, and complications represented no distinct differences between femtosecond laser-enabled keratoplasty and conventional penetrating keratoplasty (p > 0.05).

CONCLUSION

Femtosecond laser-enabled keratoplasty may not be superior over conventional penetrating keratoplasty in decreasing postoperative topographic astigmatism, but might have advantages to achieve best-corrected visual acuity and endothelial cell density preservation. In addition, the two techniques seem to be comparable regarding spherical equivalent, graft rejection/failure, and complications.

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.

Rapid suture management of post-keratoplasty astigmatism

AIM

Post-keratoplasty astigmatism is managed by topography-guided suture removal. This can take several weeks until satisfactory reduction in astigmatism is achieved. This study aimed to assess whether topography performed 30-40 min after the removal of the first pair of sutures would predict the next set of sutures requiring removal.

METHODS

A prospective study of 20 consecutive penetrating keratoplasty patients was carried out. Topography guided suture removal in the steep meridian was carried out. Topography was repeated after 30-40 min and 4-6 weeks later. The tight sutures requiring removal were identified for each occasion and compared. The difference was considered insignificant if the axes of sutures requiring removal was <22.5 degrees. Paired t-test and chi (2) were performed for statistical analysis.

RESULTS

In 85% of individuals, the 30-40 min topography gave an accurate indication of the next pair of sutures requiring removal. The difference in mean astigmatism at 30-40 min post suture removal (4.37+/-2.08 D) and at 4-6 weeks (4.24+1.97 D) was not significant (P=0.150). However, the difference between vector-corrected change of topographic astigmatism at 30-40 min after suture removal and at 4-6 weeks (1.72 D) was significant (P<0.001). Improved best-corrected visual acuity was seen in 50% of patients.

CONCLUSION

This study showed that corneal topography performed 30-40 min after suture removal can identify the next set of sutures requiring removal. This can be used as a guide to remove more sutures at the same visit, thereby expediting post-keratoplasty visual rehabilitation and reducing the number of follow-up visits.

Late Changes in Refraction, Pachymetry, Visual Acuity, and Corneal Topography After Penetrating Keratoplasty

PURPOSE

To analyze the late changes in refraction, corneal topography, and pachymetry after penetrating keratoplasty.

METHODS

We have retrospectively analyzed data of 64 eyes of 56 patients with a clear corneal graft and no other ocular diseases. The eyes were examined soon and several years after all sutures were removed, at 19.5 +/- 3.1 months and 76.8 +/- 25.2 months, respectively, after keratoplasty. All eyes were examined using the EyeSys 2000 videokeratograph and the Tomey SP2000 ultrasonic pachymeter. Corneal surface regularity was studied using the indices provided by the Holladay Diagnostic Summary (ie, asphericity coefficient Q; corneal uniformity index CU; predicted corneal acuity PCA). Irregular astigmatism was quantified using semimeridian data from videokeratographs (refractive power symmetry index).

RESULTS

Visual acuity increased by an average of 0.35 +/- 0.93 lines (P = 0.002) between the 2 examinations, whereas no significant changes in refraction and videokeratoscopy (ie, power, indices, and irregular astigmatism) were observed (P > or = 0.08). Central corneal thickness significantly increased from 542 +/- 31 microm to 572 +/- 38 microm (P < 0.001). Change in BSCVA did not significantly correlate with the change in refraction, in topographic indices, or in irregular astigmatism (rs < or = 0.13; P > or = 0.16).

CONCLUSION

Late after penetrating keratoplasty, best corrected visual acuity shows a small but statistically significant improvement, whereas refraction and corneal surface regularity are stable. This late improvement in visual acuity is not explained by current techniques.