|Year : 2019 | Volume
| Issue : 2 | Page : 48-53
Suture related astigmatism after penetrating keratoplasty
Anuradha Raj, Renu Dhasmana, Harsh Bahadur
Department of Ophthalmology, Himalayan Institute of Medical Sciences, Swami Rama Himalayan University, Dehradun, Uttarakhand, India
|Date of Submission||26-Jul-2019|
|Date of Decision||06-Oct-2019|
|Date of Acceptance||22-Oct-2019|
|Date of Web Publication||09-Mar-2020|
Dr. Anuradha Raj
Department of Ophthalmology, Himalayan Institute of Medical Sciences, Swami Rama Himalayan University, Jolly Grant, Dehradun, Uttarakhand
Purpose: The purpose of the study was to evaluate the influence of various factors on the astigmatism before and after suture removal after penetrating keratoplasty. Methods: This observational study was conducted in which we reviewed retrospectively the records of 51 eyes of 50 patients who underwent PK for optical purposes in between March 2013 to February 2016. Various recipient parameters like age, sex, lens status , indications of PK, grading and size of recipient graft, pre and post suture removal (SR), best-corrected visual acuity (BCVA) refractive and keratometric astigmatism(KA) with axis, central corneal thickness(CCT), IOP, and graft clarity were noted. Results: Average age of the recipient was 51.16±18.53 years. Major indication of PK was corneal opacity in 47 (54.02%). B+ grade and graft size of ≥8 mm was used in maximum cases 79 (90.80%), 50 (57.47%) respectively. Pre SR refractive and KA were 4.85±1.04D and 5.24±1.08D respectively and post SR refractive and KA were 2.56±0.74D and 2.87±0.80D respectively. Pre SR in maximum cases 67 (77.01%) refractive astigmatism was seen with in 3-6 D and post SR maximum cases 53 (60.91%) were seen with refractive astigmatism <3 D. Indications of PK showed significant relationship with KA before SR with p value of 0.01. Size of graft showed significant relationship with pre SR refractive astigmatism, pre and post SR KA (P = 0.00,0.00,0.00) respectively. Conclusion: Indications of PK and size of the graft influence astigmatism both pre and post SR after PK.
Keywords: Astigmatism, graft-host junction, penetrating keratoplasty
|How to cite this article:|
Raj A, Dhasmana R, Bahadur H. Suture related astigmatism after penetrating keratoplasty. Sudanese J Ophthalmol 2019;11:48-53
| Introduction|| |
Keratoplasty is a well-established surgical procedure that helps in treating different corneal disorders. Keratoconus, corneal opacities, and many corneal dystrophies are well-known indications for this procedure. Penetrating keratoplasty (PK) involves full-thickness corneal graft transplantation. However, it has the disadvantage of triggering the immunological reaction and thus resulting in graft rejection. Ing et al. reported 10-year cumulative risk of graft rejection of 21%. Visual acuity after keratoplasty depends on graft clarity and refractive error. Cases with clear graft may not achieve the desired level of increase in visual acuity due to postoperative high astigmatism. Donor graft-recipient bed disparity, indication of PK, trephine size, malapposition of donor and recipient tissues, decentralized trephination, suture technique, and time of suture removal (SR) cause postoperative astigmatism.,, To the best of our knowledge, the influence of factors affecting changes in astigmatism before and after SR has been analyzed in only a few studies by Mader et al. and Yilmaz et al.,
This study was conducted to evaluate influence of various factors such as indications, graft size, and grade on the astigmatism pre- and post-SR.
| Materials and Methods|| |
The research was approved by the institutional research ethical committee and was in accordance to the tenets set forth in the Declaration of Helsinki. This observational study was conducted retrospectively in which records were reviewed for 51 eyes of 50 patients who underwent PK for optical purposes and were examined for routine follow-up between March 2013 and February 2016.
Patients with preoperative diagnosis of corneal opacity or scarring, pseudophakic bullous keratopathy (PBK), corneal dystrophy, and anterior staphyloma were included in the study. All cases had clear graft at the time of enrollment.
All patients of post therapeutic and tectonic grafts, corneal ectasias or keratoconus, graft failure, uncontrolled postkeratoplasty glaucoma, graft rejection, graft infection, and cases with additional ocular procedures besides PK such as trabeculectomy, cataract surgery, and sequential SR were excluded from the study. Uncooperative cases and cases with follow-up <24 months were also excluded from study.
The parameters such as age, sex of the patient, indications of PK, lens status, grading and size of recipient graft, best-corrected visual acuity (BCVA) pre- and post-SR, refractive astigmatism and keratometric astigmatism (KA) with axis, central corneal thickness (CCT), IOP, and graft clarity were noted till maximum of 18 months after PK with range of 7–12 months after SR. The refractive astigmatism and KA were divided as <3, 3–6, and >6 Diopter (D) before and after SR. BCVA was noted with pin hole, glasses, or rigid gas-permeable lenses.
All PKs were performed by standard surgical technique under peribulbar anesthesia by single surgeon. Full-thickness corneal graft preserved in Mackey–Kaufmann media was used within 96 h. Donor and recipient corneas were trephined manually. Graft oversizing of 0.5 mm was done in all cases. The grafts were secured to the host bed by 16 interrupted or continuous bites using 10-0 nylon [Figure 1]. The recipient button and donor corneoscleral rim were sent for histopathological examination. Routine postoperative medication consisted of topical steroids and antibiotic six times daily along with artificial tears, cycloplegics, and anti-glaucoma medication if required. Routine followup schedule was weekly for the 1st month, twice during 2nd month and monthly for the 3–6 months and 3 monthly afterward. SR was started in all cases between 6 months and 1 year of follow-up. Corneal astigmatism was measured with either an optical keratometer (Javal–Schiotz) or auto kerato-refractometer or both. The astigmatic measurements were examined just before SR and 9–12 months (latest follow-up) after SR. At the time of SR, all existing sutures whether continuous or interrupted were removed completely. The patients whose sutures were removed sequentially were not included in this study.
|Figure 1: Continuous and interrupted suturing in penetrating keratoplasty|
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Astigmatic changes after SR were represented in two ways: net difference and vectorial difference. Net difference was calculated by subtraction of the amount of astigmatism before and 1 year after SR regardless of changes in axis. Negative values indicate decrease in absolute value of astigmatism, and positive values indicate increase in astigmatism. Vectorial difference was found by measurement of the change in KA after SR regarding both the axis shift and amount of astigmatism, as proposed by Jaffe and Clayman. All patients were classified according to their astigmatic values before and after SR as patients with <3 D, 3–6 D, and >6 D of astigmatism.
Data were initially entered into an excel spreadsheet and then transferred to SPSS software (Statistical Package for Social Sciences, version 22, SPSS Inc, Chicago, IL, USA). Data were expressed in terms of means ± standard deviations. Pearson Chi-square and Fisher's exact test were used to find the association between the refractive astigmatism and KA before and after SR with various variables. When data were not normally distributed, Kruskal–Wallis test was used to compare among different indications of PK and Mann–Whitney U-test was used to compare various astigmatic variables among both grades and sizes of the graft. P <0.05 was considered as statistically significant.
| Results|| |
A total of 51 eyes of 50 individuals were included in the study. Average age of the recipient was 51.16 ± 18.53 years. Pre-SR BCVA (logarithm of the minimum angle of resolution [logMAR]) was 0.89 ± 0.18. Post-SR BCVA (logMAR) was 0.46 ± 0.27. Pre- and post-SR CCT were 542.86 ± 31.44 μm and 503.11 ± 32.71 μm, respectively. Major indication of PK was corneal opacity in 47 (54.02%). B+ grade and graft size of ≥8 mm was used in maximum cases 79 (90.80%) and 50 (57.47%), respectively. Pre-SR refractive astigmatism and KA were 4.85 ± 1.04 D and 5.24 ± 1.08 D, respectively, and post-SR refractive astigmatism and KA were 2.56 ± 0.74 D and 2.87 ± 0.80 D, respectively. Pre-SR refractive astigmatism was seen in maximum cases, i.e., 67 (77.01%) within 3–6 D and post-SR refractive astigmatism <3 D was seen in maximum cases, i.e., 53 (60.91%) [Table 1]. Indications of PK showed significant relationship with KA before SR with P = 0.01 [Table 2].
|Table 2: Influence of various variables on refractive and keratometric astigmatism before suture removal|
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Indications of PK showed significant influence on post-SR refractive astigmatism, pre-, and post-SR KA (P = 0.02, 0.05, and 0.04), respectively [Table 3].
|Table 3: Influence of various indications of penetrating keratoplasty on refractive and keratometric astigmatism pre- and post-suture removal|
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Graft grade showed no significant relationship with various astigmatic variable, but size of graft showed significant relationship with pre-SR refractive astigmatism, pre-, and post-SR KA (P = 0.00) each [Table 4] and [Table 5]. CCT showed no significant relationship with pre- and post-PK astigmatic variables.
|Table 4: Influence of various variables on refractive and keratometric astigmatism after suture removal|
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|Table 5: Influence of grade and size of graft on refractive and keratometric astigmatism pre- and post-suture removal|
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| Discussion|| |
After PK, despite being clear, corneal graft may be an optical failure due to irregular astigmatism which leads to suboptimal vision., 15%–31% of patients undergoing PK may develop postoperative astigmatism >5 diopters (D) and in 10%–20% of PK cases cannot be corrected satisfactorily by spectacles or contact lenses., Williams et al. evaluated 60 patients who underwent PK with different preoperative diagnoses and noted that 38% of patients had 5 D or more astigmatism. Similarly, in the current study, the mean refractive astigmatism and KA were 4.85 ± 1.04 D and 5.24 ± 1.08 D respectively. In maximum i.e. 77.01% cases preSR refractive astigmatism was seen within 3–6 D which is higher than 38% as reported by Williams et al.
Early SR carries risk of wound dehiscence and subsequent infection, but visual recovery could be achieved by suture intervention or manipulations.
In the present study, major indication of PK was corneal opacity in 54.02% which is comparatively higher than 39.21% and 28.1% as reported by Raj et al. and Dandona et al., Raj et al. reported that the different indications of PK show different malappositions of posterior graft-host junctions (GHJ's) as hill and step pattern was seen in PBK and adherent leukoma predominantly, respectively. Hill type of malapposition significantly differs with BCVA (log MAR) and KA. The alignment pattern of the GHJ's by anterior segment-optical coherence tomography correlates significantly with the magnitude of astigmatism after PK. Graft-host thickness disparities and the alignment pattern of GHJs can differ according to the indications of PK and shows significant correlations with KA. However, on contrary, in this study, malappositions has not shown any significant relationship with the astigmatism.
Yilmaz et al. found a significant positive correlation between pre-PK diagnosis of keratoconus and astigmatic shift following SR which showed consistency with the current study where indications of PK showed significant influence on pre-, post-SR KA, and post-SR refractive astigmatism.
After SR various factors influence astigmatism and the astigmatism significantly decreased by SR following PK.
Grade of graft showed no significant relationship with various astigmatic variable. Graft size can be tailored by surgeon for each case without compromising optical quality and immunological purpose. Graft size and donor–recipient disparity show significant impact on postkeratoplasty astigmatism. After PK, a smaller graft diameter results in a flatter curvature and a higher degree of topographic irregularity, but not in higher net astigmatism. Seitz et al. reported that the smaller sized graft results in higher topographic irregularity with astigmatism which tends to regularize on SR. The major reason for the more irregular graft with smaller graft seems to be the closer position of the suture ends to the optical graft center. Pronounced graft irregularities can be seen with wider suture bites. Moreover, after SR, the circular scar of GHJ lies closer to the optical center in smaller grafts. This explain the reason of the fact that overall regularity of graft topography increases with SR, but the principal differences between various graft sizes do persist. Similarly, in the current study, size of graft showed significant relationship with pre-SR refractive astigmatism, pre-, and post-SR KA. Graft oversizing shows a particular impact on the central corneal steepness after PK. Lin et al. reported that surface asymmetries may decrease after the removal of a single running 10-0 nylon suture. Bourne et al. investigated the endothelial cel1 loss after PK for more than a decade, but Langenbucher et al. reported that it depends on the indications of PK which explains the fact that in bullous keratopathy, larger graft is warranted not just to improve the optical performance but also for higher endothelial cells' population.
Graft central thickness is considered to be quantitative method for evaluating corneal edema post-PK. CCT decreases in postoperative period irrespective of indications of PK. Corneal thickness is the factor involved in postkeratoplasty astigmatism. On the contrary, the CCT does not show significant relation with astigmatism. The amount of astigmatic correction as refractive cylinder in spectacles is typically less tolerated than the amount of keratometric or even topographic astigmatism due to the fact that spherical and astigmatic refractive errors can be corrected with spectacles, whereas other optical aberrations cannot be corrected.,
This study has few limitations as the sample size was small. We did not assess the donor-related factors like death-to-preservation time and death-to-utilization time which may influence the graft thickness which can further affect the astigmatism. Keratometry was done with manual and automated keratometer which can measure only up to 3 mm of central cornea. Corneal topography was not done to find the effect of anterior and posterior graft surface on astigmatism which could have yielded more accurate results. Donor and recipient corneas were trephined manually which could have led to mechanical distortion of graft and thereby vertical tilt. Graft oversizing was not varied but fixed to 0.5 mm in all cases. Variations in posterior GHJ's appositions could have been missed in images as we obtained eight images for one eye at a time in raster scan.
| Conclusion|| |
Astigmatism after PK depends on various factors such as indications of PK and size of the graft which affect astigmatism both pre- and post-SR. Both astigmatic and KA show drastic reduction from 3 to 6D before SR to <3 D after SR which can further remarkably reduce the visual disability in these patients, not only due to refractive error but also due to optical aberrations because of higher astigmatism.
Authors would like to thank Mr. Shubham Pandey, Assistant Professor, and Mr Ankit, Lecturer, Department of Biostatistics for Statistical analysis and Mrs Neelam Petwal and Miss Kavita Dogra Lecturer, Department of Optometry for their tireless effort in managing the optometric work up of all the patients. We thank Mr. Surendra Singh Bhandari, Office Assistant for technical support and photographic documentation.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]