|Year : 2016 | Volume
| Issue : 2 | Page : 56-61
Evaluation of the effect of donor parameters on visual outcome after optical 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 Web Publication||17-Jan-2017|
Department of Ophthalmology, Swami Rama Himalayan University, Himalayan Institute of Medical Sciences, Jolly Grant, Dehradun, Uttarakhand
Source of Support: None, Conflict of Interest: None
Aim: The aim of the study was to analyse the effect of various donor parameters on visual outcome after optical penetrating keratoplasty (OPK). Methods: Data were reviewed retrospectively for the patients who underwent OPK. Donor factors which included the age and sex of the donor, cause of death, death to enucleation time (DET), death-to-preservation time (DPT), enucleation to utilisation time (EUT), total time (TT) in hours and recipient factors like age, sex, intraocular pressure (IOP) and best corrected visual acuity (BCVA) were analysed from preoperative and postoperative visits at range of 7-9 months. According to BCVA patients were divided into three groups as group 1,2 and 3 with BCVA of ≥6/18 ,6/24-6/60 and <6/60 respectively. Results: Donor variables like gender, cause of death, EUT and TT did not show any effect on the BCVA. The difference between DET of ≤3, >3hours and DPT of ≤4, >4 hours showed significant effect on BCVA with p value of 0.024 and 0.050 respectively. Average logarithm of minimal angle of resolution (log MAR) BCVA at last follow up was 0.75. According to BCVA maximum patients 55 (60.43%) fell into group 2. BCVA improved from the pre operative status in 81 (89.01%) of eyes. Conclusions: Donor variables shows impact on the visual outcome during short span of post OPK follow ups till nine months. Both donor and eye bank variables influence quality of donor corneas, outcome and complications of PK.
Keywords: Death to preservation time, donor variables, penetrating keratoplasty
|How to cite this article:|
Raj A, Dhasmana R, Bahadur H. Evaluation of the effect of donor parameters on visual outcome after optical penetrating keratoplasty. Sudanese J Ophthalmol 2016;8:56-61
|How to cite this URL:|
Raj A, Dhasmana R, Bahadur H. Evaluation of the effect of donor parameters on visual outcome after optical penetrating keratoplasty. Sudanese J Ophthalmol [serial online] 2016 [cited 2022 Jun 30];8:56-61. Available from: https://www.sjopthal.net/text.asp?2016/8/2/56/198541
| Introduction|| |
Penetrating keratoplasty (PK) is a surgical procedure, in which recipient cornea of its full thickness is replaced by donor tissue. Good quality donor material, minimal surgical trauma, and a favorable host environment increase chances of success of PK. After PK, it is usually assumed that an eye with good visual acuity has a successful and functioning graft. Many donor factors influence the outcome of PK which can be attributed to the age and the time elapsed between death and enucleation and its preservation. It is commonly believed that best outcomes of PK as early graft clarity are achieved using corneas from young donors without any delay after death. Australian Graft Registry reported that the graft survival was same for donor age of <50 years or >70 years.  Gain et al. found no significant difference between the two groups of donors of age <85 years and >85 years and older in terms of visual acuity and astigmatism.  Halliday and Ritten found no significant correlation between the time taken to reach a postoperative acuity of 6/12 and the age of donor.  Donor factors such as age, local and systemic diseases, cause of death, and trauma or surgical procedures as well as the storage factors mainly storage method, death to enucleation time (DET), death to preservation time (DPT), enucleation to utilization time (EUT), and total time (TT) can influence the final quality of the corneas. The present study was conducted to analyze the effect of various donor parameters on post optical penetrating keratoplasty (OPK) graft's clinical performance and visual outcome.
| Materials and Methods|| |
The observational study was approved by the Institutional Research Ethical Committee and was in accordance with the tenets set forth in Declaration of Helsinki. Data were reviewed retrospectively for the patients who had undergone PK for the purpose of visual regain from March 2013 to February 2016. Procurement, surgical technique, and postoperative care were of consistent regimens. Donor tissue was distributed by the eye bank according to the EBAA medical standards or rejected because of medical or social factors infectious or structural contraindications or by serologic testing adversely affecting the donor cornea.  Corneoscleral rim excision was done for all eye donations, and donor tissue was collected in McCarey-Kaufman (MK) medium with all aseptic precautions. Tissue grading was done according to grading chart by National Eye Bank as Grade A, B + , B, B− , C, and D.  For OPK, donor tissues graded A, B + were used.
For the precise assessment of the visual regain, strict exclusion criteria were followed to minimize the influence of noncorneal factors on the recovery of visual acuity. Eyes with preoperative pathologies such as lid pathologies, severe dry eye, ocular surface disorders, graft infection, graft rejection, corneal perforation, preexisting glaucoma, retinal pathology, and triple procedures (cataract surgery with or without lens implant) were excluded.  This "retrospective" exclusion of cases is justifiable because these complications cannot be related to the donor cornea parameters. Hospital notes were also examined to find patients who had visual acuities recorded, at successive clinic visits, with the use of a pinhole and with refraction. Other exclusion criteria were the patients who were lost to follow-up before suture removal.
All patients who underwent OPK for various indications were included in the study [Figure 1]. All cases had clear graft at the time of enrollment.
|Figure 1: Distribution of various indications of penetrating keratoplasty|
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Preoperative ophthalmological examination was reviewed for the recipients, which consisted of measurement of uncorrected visual acuity (UCVA), manifest refraction (if possible), best-corrected visual acuity (BCVA) with fully corrective glasses or rigid gas permeable contact lenses, slit-lamp biomicroscopy, Goldman applanation tonometry, dilated fundus examination or B-scan if fundus was not visible. OPKs were done with a standard technique with donor grafts 0.5 mm larger than the recipient. Depending on the indications, vascularity, and infection, both interrupted and continuous suturing were done. Histopathological examination was done for the recipient button and donor corneoscleral rim. Routine postoperative medication consisted of topical prednisolone 1% combined with preservative-free topical antibiotic, artificial tears, cycloplegics, and antiglaucoma if required, followed by tapering topical steroids. Routine follow-up schedule was weekly for 1 st month, biweekly for 2 nd month, monthly for 3 months, and 3 monthly afterward. To exclude the surgical bias, all patients included in the study were operated by one surgeon.
Data were analyzed for donor corneal factors such as age and sex of the donor, cause of death, DET, DPT, EUT, and TT in hours and recipient records were reviewed for recipient age, sex, recipient size, intraocular pressure (IOP), and BCVA.
Retrospective data of BCVA records were gathered preoperatively and from postoperative visits after suture removal in range of 7-9 months follow-up. Selective interrupted suture removal and adjustments in continuous suture tension were started at 3 months postoperatively to reduce keratometric astigmatism. Sequentially selective interrupted suture removal was performed starting with tight sutures depending on keratometry and was continued until an acceptable amount of astigmatism was achieved till maximum of 9 months.
IOP was measured by using a Tonopen™ at each visit and medical management was initiated if IOP was elevated (>22 mmHg). Patient's charts were reviewed for donor epithelial status and graft clarity from follow up at various intervals. After suture removal for all patients, visual outcomes included UCVA, BCVA, manifest refraction, mean keratometry and keratometric astigmatism at the final follow-up at a range of 7-9 months postoperatively. According to BCVA, grouping was done as 1, 2, and 3 with BCVA of ≥6/18, 6/24-6/60, and <6/60, respectively.
Data were initially entered into an excel spreadsheet and then transferred to Statistical Package for Social Sciences (SPSS) (SPSS software version 22, SPSS Inc., Chicago, IL, USA). The quantitative factors such as age, graft size, and central graft thickness and qualitative factors such as indications of PK were included in the data. The descriptive statistics was used to express data in terms of frequency and percentage. Data were expressed in terms of means ± standard deviations (SDs). The donor variable such as donor age, sex, cause of death, DET, DPT, EUT, and TT and recipient factors such as recipient size and IOP were taken into account for their correlation with visual outcome [Table 1]. BCVA were converted from the Snellen's units to the logarithm of minimal angle of resolution (logMAR). Chi-square test was used to find out the BCVA at last follow-up and its relationships with the various donor factors or variables. P < 0.05 was considered statistically significant.
|Table 1: Relationship between the donor and recipient parameters with best-corrected visual acuity in different groups|
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| Results|| |
In the present study, data of 91 eyes of 91 patients was reviewed who underwent OPK for various indications. The recipient age at which PKs were done ranged from 10 to 83 years (mean 49.19 ± 19.35 years). The sex distribution among the recipient in the current study was 64 (70.32%) males and 27 (29.67%) females. Left eye was involved in 53 (58.88%) cases. The sex distribution in donors was 53 (58.88%) and 38 (42.22%) for males and females, respectively. The donor age in this study ranged in between 17-95 years (mean ± SD 70.27 ± 15.11 years).
The most common indication for PK was corneal scarring including adherent leucoma 44 (48.35%) and least common indication was stromal corneal dystrophy in 2 (2.19%) cases [Figure 1].
The age of the donor showed weakly significant effect on BCVA with P = 0.086. Gender, cause of death, EUT and TT did not show any effect on the post-OPK BCVA. The difference between DET ≤3 and >3 and DPT ≤4 h and >4 h showed significant effect on BCVA with P = 0.024 and 0.050, respectively [Table 1]. Average BCVA in logMAR at last follow-up was 0.75. Post-OPK maximum patients 55 (60.43%) had BCVA of 6/24-6/60 and minimum 10 (10.98%) patient fell in group of BCVA of <6/60.
To determine whether any improvement in visual acuity had resulted from the transplant procedure, a comparison was made of preoperative Snellen acuity and the postoperative acuity at the time of the last follow-up.
Mean preoperative BCVA was 1.34 ± 0.54 logMAR, which improved to 0.75 ± 0.13 (range 0-1.30) logMAR at final follow-up. Mean preoperative keratometry was 54.05 ± 2.14 Diopter (D) (range 46.0-57.5D), which was reduced to 44.42 ± 2.54D (range 39.75-56.00D), postoperatively. Preoperatively, mean spherical equivalent refractive error and keratometric astigmatisms were −11.84 ± 4.45D and 5.05 ± 3.26D, respectively. Postoperatively, these figures decreased to −3.76 ± 3.04D and 3.34 ± 2.05D, respectively.
Preoperative BCVA was ≤6/60, counting fingers (CFs) at 1 meter and hand movements close to face (HMCF) in 6 (6.59%), 68 (74.72%), and 17 (18.68%) eyes, respectively. Post-OPK in 10 (10.98%) cases BCVA was same as before PK in 3 eyes HMCF and 7 cases CF, which we classified. In all these ten cases, the causes of no improvement in visual acuity were graft failure, 7 cases due to repeated rejection episodes, and 3 cases due to postkeratoplasty glaucoma. In 81 (89.01%), BCVA improved from the preoperative status to ≥6/18, 6/24-6/60 in 26 (28.57%), and 55 (60.43%) eyes, respectively [Figure 2].
|Figure 2: Distribution of best corrected visual acuity in patients' postoptical penetrating keratoplasty|
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Host factors such as the recipient size and IOP showed no significant effect on visual outcome.
Keratometric astigmatism observed ranged in between −4D and + 5D.
| Discussion|| |
Although visual acuity is not a sine qua non of a functioning graft, it is usually true that good acuity has a successful, functioning graft. However, good acuity does not predict graft success. In this study, visual acuity was used as a measure of graft quality. Any additional ocular pathology that could decrease acuity was excluded from the analysis. Normal corneas have excessive endothelial cell function than required to maintain corneal deturgescence and clarity. Storage techniques and donor parameters affecting the endothelial cells adversely may not reduce its function below the critical value. A successful graft initially may lose clarity and fail over a longer period of follow-up.
In the present study, BCVA showed weakly significant relationship with the age of the donor as increased donor age results in decreased endothelial cell viability and slower visual recovery. Adult eyes undergoing PK with young donor corneas as compared to older donor corneas had greater incidence of allograft reactions and the postoperative corneal curvature. However, there was no difference in the incidence of graft failure due to rejection between the two groups.
Palay et al. proposed an explanation for the repeated failure to observe an effect of donor age on corneal graft survival. Older donor tissue has low average endothelial cell density (ECD) than that of younger donors; however, there is less likelihood of its further reduction by rejection. Younger donor tissue has a higher initial ECD, but it is more likely to be reduced by frequent rejection. Due to the balance of these factors with each other, the net effect is same survival rate for PKs from young and old donors.  Halliday and Ritten reported no significant correlation between the time taken to reach a postoperative acuity of 6/12 and either storage time of donor corneas or age of the donor. A significant delay in recovery of visual acuity was found with increasing age of recipient.  Older donor age and longer storage time are more likely to be associated with lower ECD; however, as long as the ECD is greater than a given minimum at the time of PK, these parameters will have insignificant influence on long-term graft survival. The cornea donor study results indicate that donor age is not an important factor in PKs performed for endothelial disease.  Therefore, functional and cellular results of PKs are not dramatically influenced by very old donor age, so elderly should not be deemed off limits for corneal procurement. Gain et al. found no significant difference in terms of BCVA and astigmatism in between the two groups donors <85 years and >85 years.  Halliday and Ritten found no significant correlation between the age of donor and the time taken to reach a postoperative acuity of 6/12. 
Grabska-Liberek et al. found that the rating of the morphological state of corneas suitable for PK depended mostly on age of the donor, cause of death, and DPT. The rating of corneal tissues obtained in a very short time of 5 h after death was excellent and very good as compared to corneas removed 8-12 h after the donor's death. The endothelial cell loss increased after 7 days of preservation independent of other factors. 
In the present study, gender, cause of death, EUT, and TT showed no significant effect on visual outcome. In this study, the patients in which BCVA was not regained after PK belonged to the group of multiple graft rejections. Stulting et al. reported that donor age, ABO compatibility, and other donor factors were not associated with graft rejection.  The majority of studies showed that donor preservation method and time, donor age, cause of death, and preoperative donor ECD and its morphometric measures such as coefficient of variation and hexagonality had no influence on overall graft failure. ,
In the present study, DET and DPT significantly affected the visual outcome which is contradictory to various studies which can be explained by the fact that the BCVA monitoring in this study is done for a short follow-up of maximum 9 months which could not take into account the attrition of endothelial cells in this short span of time.
Feizi et al. investigated the influence of donor and eye bank factors, including age, sex, cause of death, DPT, graft quality, storage time, and type of storage media on post-PK complications and outcomes. Donor and eye bank variables affected the quality of donor corneas in the early postoperative course which is also proved in the current study. The results demonstrated that DPT was correlated significantly with epithelium-related problems after PK.
However, their long-term effect on clinical outcomes, complications, and graft survival was insignificant. Feizi et al. reported that refractive outcomes and postoperative BCVA were not significantly associated with donor or eye bank variables which are not consistent with the results of the present study.  On the contrary to the current study, long-term significant effect of the DPT and DET on visual outcome was seen which makes this study unique and different. Long-term results of DPT on visual outcome can be explained by the effect of the storage media, MK media, on the ECD and to some extent the donor age affects the ECD. The duration of corneal storage of up to 3 days in MK media and up to a few weeks in organ culture was unrelated to the postoperative visual acuity in one small series.  Palay et al. reported no difference in failure for grafts with host trephine sizes <8 mm compared to those >8 mm (P = 1.0, Fisher's exact test) which is in accordance to the present study where host trephine size showed no effect on visual outcome of the recipient.  The effect of donor factors such as DPT and DET on visual outcome were not validated before which makes this study unique and different.
Highlights of the study
- Donor parameters such as death to enucleation time and death to preservation time plays an important role on visual outcome after penetrating keratoplasty
- 89.01% of patients showed improvement in their best-corrected visual acuity as compared to preoperative status which shows importance of penetrating keratoplasty to relieve burden of blindness from this developing country
- Besides the storage media, age of the donor, and endothelial cell density, these time-related donor parameters can take care of the objectives of penetrating keratoplasty.
Quality of donor cornea quality may also be assessed in vivo by measurements of corneal thickness and ECD, but both of them were not assessed in the current study. We assessed donor tissue only in one storage media while other media were not used to get the comparative data on DPT. We have not taken into account the effect of recipient factors such as age and indications on visual outcome.
| Conclusion|| |
Various donor parameters influence the visual outcome significantly during a short follow-up of maximum of 9 months without taking into account the ECD. However, both donor and eye bank variables have effects on the quality of donor corneas, post-PK outcomes, and complications. Before transplantation all patients had BCVA of ≤6/60, however, after OPK, 81 (89.01%) patients showed improvement in their BCVA as compared to their preoperative visual status which suggest that PK can be a reasonably successful procedure for visual outcome in this part of developing world for most of the indications if the minimum donor selection criteria set by eye banks is respected. In the current study, further follow-up may provide information on long-term effect of donor parameters on visual outcome after PK.
We would like to thank Mr. Shubham Pandey, Assistant Professor Statistics for Statistical analysis, and 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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[Figure 1], [Figure 2]