Keratoconus, keratoplasty thickness, and endothelial morphology.

Abstract

SUMMARY A group of successful keratonic grafts (51 eyes) up to 10 years from operation were examined to e3tablish a relationship between graft thickness and acuity. Best acuity occurred in the grafts of normal corneal thickness. No grafts were thinner than normal; thus no tendency to keratonic thinning occurred. No relationship between age of graft and thickness was determined. Endothelial cell studies in vivo of a small number of grafts showed that cell counts a third of normal coexisted with normal acuity and corneal thickness.It has been suggested that the keratoconus graft can after a time show keratonic features of the primary disease. The present work measured the corneal graft thickness in 51 eyes to establish whether after a time the graft became abnormally thin. According to Ruben (1972) many grafts were thicker than normal cornea, and the greater the thickness the more abnormal the corrected acuity was likely to be. These findings were assumed to be related to endothelial dysfunction and/or stromal fibrosis and corneal irregularity.In the present study the grafts were only of keratonic eyes and graft eye groups were compared as to their thickness and keratometry. Further, for a few patients with acuity corrected to normal the endothelial mosaic was studied by means of slit-lamp macrophotography and any correlation with corneal thickness was noted. A study of the same group of patients as to acuity, contact lens wear, and effects on curvatures and corneal sensitivity is reported separately (Rubens and Colebrook, 1979a, b).It is accepted that at the time of operation the fresh donor cadaver material is almost always thicker than normal cornea, and that often during the operation procedure both thinning and clearing of the graft does occur. While this may not be indicative of endothelial function, but rather the drying of the graft, it will be expected that after several years the clear grafts would vary according to the degree of endothelial survival. If keratoconus is to recur in a graft, one would expect some thinning associated with steepening of the graft.In all the grafts analysed the recipient aperture and

Effects of central corneal thickness on measurement of intra‐ocular pressure in keratoconus and post‐keratoplasty

“…Within the post-keratoplasty group 21% of cases fell within the normal limits of thickness. This is comparable with the ®gure of 15% noted by Ruben et al (1979). Ultrasonic pachymeters tend to underestimate corneal thickness when compared with optical pachymeters (Nissen et al, 1991;Patel and Stevenson, 1994).…”

“…The mean thickness in the post-keratoplasty group, 564 m (s.d. 244 m) is lower than the average of 600 m reported by Ruben et al (1979) in 51 post-graft cases. However, it is higher than the typical range of 500±520 m for the normal cornea.…”