|Year : 2004 | Volume
| Issue : 2 | Page : 151-3
Low Endothelial Cell Count and Clear Corneal Grafts
Samar K Basak
Disha Eye Hospital & Research Centre, Barrackpore, West Bengal, India
Samar K Basak
Disha Eye Hospital & Research Centre, Barrackpore, West Bengal
Source of Support: None, Conflict of Interest: None
Specular microscopic study on clear corneal grafts indicates that at times surprisingly low endothelial cell density can maintain the grafted cornea in a relatively dehydrated state. The critical limit of the endothelial cell count for corneal decompensation is thought to be 700 cells/mm2. This communication reports 13 cases of clear corneal graft with endothelial cell count below 700 cells/mm2.
Keywords: Clear corneal graft, specular microscopy, endothelial cell count, pachymetry, critical limit of endothelial cell count
|How to cite this article:|
Basak SK. Low Endothelial Cell Count and Clear Corneal Grafts. Indian J Ophthalmol 2004;52:151
A major decrease in the corneal endothelial cell population after penetrating keratoplasty occurs in the first year. At three months this decrease is between 18% and 24%, and by the end of one year between 34% and 45%., Thereafter, despite a small degree of continuous cell loss, corneal grafts have a favourable prognosis for longterm clinical stability. However, the endothelial cell density does not always correlate well with the endothelial function. In the long run, this continuous decrease in endothelial cell count, and their concomitant increase in size and shape are accompanied by a decreased ability to maintain and restore pump and barrier function. Thus, when the endothelial cell count goes below 700 cells/mm2, the functional reserve is minimum and corneal oedema is likely to occur. This apparent paradox of low endothelial cell count and clear corneal graft has been reported earlier in the literature. ,,, This communication reports a series of 13 cases of clear corneal graft with surprisingly low endothelial cell count.
| Case report|| |
Thirteen patients with clear corneal graft with endothelial cell count below 700 cells/mm2 were included in this retrospective case series. Endothelial cell count and pachymetry were done in these cases with a non-contact specular microscope [SP-2000P (Topcon ®)]. For each patient, the values were obtained from the average of readings of five predetermined points, namely, central, nasal, temporal, upper and lower. The follow-up period for these patients ranged between 7 and 63 months (mean 36.2 ± 7.1 months). The recipient′s age, indications (preoperative diagnosis), donor age, graft age (follow-up period) and postoperative clinical course are given in the [Table - 1]. The density of the donor corneal endothelium was not known prior to penetrating keratoplasty in these eyes.
The donor age for these 13 patients was between 44 and 88 years (mean 68.2 ± 11.9 years). Two eyes (cases 2 and 9) developed allograft rejection after 4 and 7 months respectively. With medication, rejection was reversed in both the cases and the grafts became clear. One patient developed steroid-induced glaucoma, which was controlled medically. One patient developed steroid-induced cataract after 14 months and phacoemulsifica-tion with PCIOL was successfully done. The best-corrected visual acuity at the last visit was 6/12 or better in 9 eyes. Three patients had visual acuity between 6/36 and 6/18. The endothelial cell count of these grafts ranged from 393 to 635 cells/mm2 (mean 509.61 ± 48.21). In 6 eyes, the cell count was below 500 cells/mm2; and in 7 eyes, the count was below 700 cells/mm2. The pachymetric readings ranged from 439 to 599 µm (mean 514.62 ± 52.17). The anterior segment and specular microscopic photographs of two patients are shown in [Figure - 1] and [Figure - 2].
| Discussion|| |
Reports on specular microscopic study after penetrating keratoplasty have shown that at times surprisingly low endothelial cell density can maintain the grafted cornea in a relatively dehydrated state. Pesko et al have reported two cases where the endothelial cell density was 500 cells/mm2. Rao et al have reported one case of clear corneal graft with a cell count of 445 cells/mm2 and thickness of 451µm. Abbott et al reported an inverse correlation of the pachymetric value with the cell count in grafted corneas with low endothelial cell count.
In this series, there was no definite correlation of pachymetric readings (correlation coefficient = 0.276) with the cell count. There was also no definite pattern of correlation with recipient′s age, indications, donor age, graft age and the postoperative clinical course in this group of patients.
Bourne reported a relationship between decreased endothelial cell density in 12 eyes with clear corneal graft with enlarged endothelium to deswelling rate and endothelial permeability to fluorescein by fluorophotometry, and compared it with normal control subjects. He related this to the decreased cross-sectional area of the intercellular space facing the anterior chamber, due to the decreased number of cells in the endothelial monolayer. The fluid leakage and endothelial pump, which are thought to occur mainly through this pathway between cells, is thus reduced. On the other hand, endothelial permeability increases in eyes with an inherent problem, as in Fuchs′ endothelial dystrophy, resulting in stromal oedema and increased corneal thickness. Kus et al reported endothelial cell count and pachymetric value for 20 clear corneal grafts 15-33 years after penetrating keratoplasty. Only 2 of the 20 eyes had guttatae changes and 8 eyes had an endothelial count below 700 cells/mm2. The endothelial cell count of 700 cells/mm2 is often considered the critical limit of endothelial density to maintain corneal transparency. A few authors would put this number at 400-500 cells/mm2.,  However, in individual cases, other factors such as the age of the recipient, donor age, host corneal pathology, glaucoma, uveitis, allograft rejection and above all, the donor endothelial morphology or disease may also influence the critical endothelial cell count.
In this series, despite the reduced cell density of these grafts, the dehydration function of the endothelium was sufficient to maintain corneal clarity which may be explained by the reduced pump-leak hypothesis. It may be concluded that in spite of a small degree of continuous endothelial cell loss, corneal grafts have a favourable prognosis for longterm clinical stability. The remaining endothelial cells have a minimal functional reserve which may be at high risk of graft failure after additional endothelial trauma like uveitis, glaucoma, allograft rejection or cataract surgery
| References|| |
Bourne WM. One-year observation of transplanted human corneal endothelium. Ophthalmology
Culbertson WW, Abbott RL, Forster RK. Endothelial cell loss in penetrating keratoplasty. Ophthalmology
Randall VT, Edelhauser HF, Leibowitz HM, Freddo TF. Corneal structure and function. In: Leibowitz HM and Waring-III GO, editors: Corneal Disorders: Clinical diagnosis and Management
, 2nd ed. Philadelphia: WB Saunders, 1998.p22.
Kus KM, Seitz B, Langenbucher A, Naumann GO. Endothelium and Pachymetry of clear corneal grafts 15 to 33 years after penetrating keratoplasty. Am J Ophthalmol
Abbott RL, Fine M, Guillet E. Long-term changes in endothelium following penetrating keratoplasty. Ophthalmology
Pesko K, Volker-Dieben HJ. Changes in corneal endothelium after penetrating keratoplasty. Cesk Slov Oftalmol
Rao SK, Leung TSA, Young LA, Fan SPD, Lam SCD. Is there a minimum endothelial cell count for a clear cornea after penetrating keratoplasty? (Letter) Indian J Ophthalmol
Bourne WM. Functional measurement on the enlarged endothelial cells of corneal transplants. Trans Am Ophthalmol Soc
[Figure - 1], [Figure - 2]
[Table - 1]