Eect of donor and host factors on corneal graft transparency

Objective : To study the correlation between donor factors and recipients' factors on graft clarity. Materials and methods : The study comprised 30 cases of Keratoplasty surgery with a follow up of 6 months. All donor corneas were evaluated by Konan specular microscope for endothelial cell count; details of the donor like age, cause of death were noted. The patients were divided into two groups, Group 1 had graft failure, and Group 2 had clear corneas. Observation and Result : There were 12 patients in group 1 and 18 patients in group 2 with six months of follow up. The mean endothelial cell count in group 1 was 1942.3/mm 2, and group 2 was 2334.8/mm 2 . There is a significant difference in the mean endothelial cell count between the two groups. On analysing the indication for Keratoplasty in two groups, the outcome was best for the corneal opacity group during worst for the graft failure group. Conclusion: Donor endothelial cell count significantly influenced graft outcome; rest donor factors (age, death enucleation interval, enucleation surgery interval) don't affect graft survival. Indication for Keratoplasty is a significant predictor of graft survival.


Introduction
Blindness is a significant public health problem in developing countries. Cataracts and corneal diseases are the two major causes of blindness in countries in developing economies. [1]. According to the World Health Organization, corneal diseases are one of the significant causes of vision loss and blindness in the world today, after cataracts and glaucoma. [2].
In India, it is estimated that there are approximately 6.8 million people with vision less than 6/60 in at least one eye due to corneal diseases; out of these, about a million have bilateral involvement. [3,4]. It is estimated that the number of people with unilateral corneal blindness in India will increase to 10.6 million by 2020. [4].
According to the National Programme for Control of Blindness (NPCB) estimates, about 120,000 corneal blind persons in the country. According to a recent estimate, there is an addition of 25,000-30,000 corneal blindness cases every year in the country. Immune-mediated rejection is the leading cause of graft failure; up to 30% of penetrating Keratoplasty will have at least one episode of rejection.

Materials and methods
Study design: Prospective interventional study.
The study was conducted in the department of ophthalmology tertiary care centre of Central India. Age less than ten years.

Results
There was a total of 30 patients in our study.
Clinical observations were made to study the factors affecting the clarity of the graft.

Table 3-Indications of surgery in our study
The most common indication for surgery in our study was corneal opacity at 36.7%, followed by

Discussion
In our study, we analysed various donor and recipients' factors affecting graft clarity. However, immunologic graft rejection after Keratoplasty is less likely than it is in other solid organ transplantation. This is attributable to the avascular corneal structure, the immunosuppressive ocular microenvironment, and the phenomenon of the anterior chamber-associated immune deviation. This produces reduced immunity to antigens introduced into the anterior chamber in experimental animal models.8,9 However, in eyes presenting with corneal neovascularisation and previous graft failure, the prognosis for corneal graft survival is reduced, and the incidence of rejection is high, similar to that of solid organ transplants. In our study, we found 60% of grafts to be precise.

Correlation between endothelial cell count and graft clarity
In our study, we found that endothelial cell count has a significant effect on graft transparency.
Endothelial cells of the human cornea maintain this tissue dehydrated by their pumping activity, thereby assuring its transparency. This is an active process that is controlled by Na+/K+ ATPase and involves the generation of a bicarbonate ion gradient across the corneal endothelium. The corneal endothelium consists of a monolayer of polygonal cells, the numerical density of which is highest at birth (3000 cells/mm2) and decline slowly but steadily after that.
A minimal numerical density of 400-500 cells/mm2 is required to sustain the pumping activity of the endothelium. Dysfunction results in corneal decompensation and loss of vision. The fact that the endothelium becomes gradually depleted of cells rather than compensating for its losses reflects the limited capacity of these cells to regenerate. This situation may become exacerbated by losses incurred during certain diseases or after intraocular surgery. [10]. We also found in our study that corneas with higher endothelial cell count had significantly higher graft clarity than low endothelial cell count, as depicted in  Registry, some grafts are categorised as high-risk grafts [14].
Our findings are in complete agreement with these workers that corneal opacity without vascularisation is a good indication for performing Keratoplasty.
In our study, corneal opacity group, all patients had clear graft, while the results were worst for the graft failure group.

Conclusion
Our study is one of its kind as it compares mean endothelial cell count with graft clarity.
Donor endothelial cell count significantly influenced graft outcome; rest donor factors like age, death enucleation interval, enucleation surgery interval don't affect graft survival.
Indication for Keratoplasty is a significant predictor of graft survival. The outcome was best for the corneal opacity group during worst for the graft failure group.

Author Contribution
AJ: Concept of study, Review of literature.

HJ: Data collections and its interpretation.
NJ: Data management, references, and literature review.