[The effect of cataract and vitreoretinal surgery on central corneal thickness and corneal hysteresis].

INTRODUCTION

Intraocular irrigating solutions remain for several hours beyond the actual time of surgery in the eye. The irrigating solution ought to resemble biochemically aqueous humor and vitreous and offer protection for sensitive structures of the eye, such as the corneal endothelium. Impairment of the corneal endothelium may lead to corneal oedema and biomechanical alterations of the cornea.

PATIENTS AND

METHODS

54 eyes after pars-plana vitrectomy (PPV) in elective macular surgery were evaluated by measuring corneal thickness (CCT) using ultrasound pachymetry (20 MHz) and corneal hysteresis (CH) using the ocular response analyser (Reichert Ophthalmic Instruments, Buffalo, NY, USA). Measurements were performed not earlier than 2 weeks prior to surgery and 1 to 3 days after surgery. Results were compared to a control group (n = 39) and to 101 eyes after clear cornea cataract extraction (KAT).

RESULTS

The two groups (PPV and KAT) did not differ with respect to age (p = 0.555). Corneal thickness has increased significantly in both groups (p <or= 0.001, mean difference: PPV group 34.95 +/- 23.57 microm and KAT group 23.76 +/- 26.0 microm, respectively) whereas corneal hysteresis decreased significantly postoperatively (p <or= 0.001; 1.93 +/- 3.15 mmHg after PPV and 1.15 +/- 2.65 mmHg after cataract surgery, respectively). Postoperative changes were significantly higher in the PPV group (CCT p <or= 0.01 and CH p = 0.011, respectively).

CONCLUSION

Surgically induced changes of the cornea may not only be characterized by anatomic parameters such as corneal thickness but also by biomechanical parameters such as corneal hysteresis.