A longitudinal case series investigating cellular changes to the transplanted cornea using confocal microscopy

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Abstract

Purpose

To perform a longitudinal evaluation of subjects who had undergone penetrating keratoplasty, using slit scanning confocal microscopy.

Methods

In vivo confocal microscopy was used to evaluate the central cornea of four subjects who had recently undergone penetrating keratoplasty. Subjects were examined on four occasions over a 12-month period after surgery. Quantitative and qualitative aspects of corneal morphology were compared against data from normal control subjects.

Results

The epithelium varied in appearance between subjects and took at least 12 months to return to a similar arrangement to that seen in normal eyes. Bowman's layer was viewed as an acellular layer immediately after surgery with no evidence of nerve fibres, although nerve components were apparent 12 months after surgery. Stromal nerves were not visible immediately after surgery. One year following penetrating keratoplasty there was evidence of thin nerves running a straight course through the central stroma. Keratocyte density in the anterior and posterior stroma was lower in the transplanted cornea but appeared to remain constant over a period of 1 year. Activated keratocytes were seen in the anterior stroma of all subjects; they appeared to be responsible for significant levels of corneal haze. The time period within which this keratocyte activation occurred varied between individuals. Endothelial cell density decreased at an accelerated rate over the 12-month period.

Conclusions

Confocal microscopy allows cellular changes to be monitored in vivo following penetrating keratoplasty and may assist clinicians in understanding postoperative recovery.

Introduction

Penetrating keratoplasty (PK) is used to treat a wide variety of corneal conditions such as keratoconus, pseudophakic corneal oedema, Fuchs’ endothelial dystrophy, herpetic keratitis, ulcerative conditions and hereditary corneal dystrophies. Confocal microscopy (CM) has become an established technique for examining morphological changes to the in vivo cornea in health and disease and has been used previously to study cellular changes following PK [1], [2]. The keratocyte density (KD) has been shown to be lower in the transplanted cornea compared to normal control subjects and seems to remain relatively constant in the month following surgery [1]. Keratocytes appear activated after surgery, with cell processes and bodies being visible [1], [2]. Confocal microscopy has also demonstrated the presence of nerves in the corneal stroma 7 months after surgery [3]. The purpose of this case series is to further evaluate longitudinal changes in cellular morphology in the newly transplanted cornea.

Section snippets

Materials and methods

Four subjects were evaluated over a 12-month period. All had undergone full thickness corneal grafts using corneas stored in organ culture. Details of both the subjects and donors are summarised in Table 1. Full ethical permission was obtained from the Central Manchester Research Ethics Committee of the Manchester Health Authority prior to commencing the study and each subject gave their informed consent for participation.

The subjects were examined on four occasions during the 12-month period

Results

All corneal grafts remained clear for the duration of the study, as determined using slit lamp biomicroscopy. In the earlier post-operative assessments, folds were visible at the level of the posterior stroma in all eyes; these were visualized by CM as dark bands lying in random directions immediately anterior to the endothelium. Folds were not apparent on slit lamp examination in any subject at the 12-month period.

Discussion

The epithelium of the newly transplanted cornea did not demonstrate the regular arrangement that is apparent in the normal eye. This is to be expected as, although epithelial cells have been shown to be largely unaffected by organ culture [8], they have been demonstrated to be affected by the de-swelling period, whilst the cornea is stored in dextran [9]. Sloughing of the external and medium epithelial layers occurs during this period. The remaining epithelium then consists of two layers of

Conclusions

This study provides further evidence of the morphological alterations that occur within the transplanted cornea over a period of 12 months. The findings within this case series are consistent with other published work within this field. It is likely that corneal transparency is affected by increased light scattering caused by abnormal cellular-based reflections from reflective keratocytes. The ability of CM to monitor cellular changes post-PK may assist clinicians in understanding the recovery

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