No correlations found between corneal or graft thickness, visual acuity and forward light scatter

Am J Ophthalmol. 2010;150(4):490-497.

Issue: November 25, 2010

Increased corneal thickness after Descemet's stripping endothelial keratoplasty did not diminish visual acuity or increase forward light scatter, a study showed.

"Although the additive nature of the DSEK procedure may seem counterintuitive to visual outcomes, variations in the thickness of the cornea or graft after DSEK do not contribute to visual acuity or intraocular forward light scatter," the study authors said. "Although much thinner grafts than those in the present study may be associated with better vision, the endothelial cell loss and survival of very thin grafts also must be shown to be better than after DSEK for them to be advantageous."

The prospective cohort study included 44 eyes of 38 patients that required DSEK because of decreased vision associated with Fuchs' endothelial dystrophy. Mean patient age at the time of surgery was 67 years.

Patients with a filtering bleb, uncontrolled glaucoma, central corneal scarring unrelated to Fuchs' dystrophy, or history of herpetic keratitis, maculopathy or optic neuropathy were excluded.

All eyes were pseudophakic after surgery.

Investigators evaluated best corrected high- and low-contrast visual acuity, intraocular forward light scatter and corneal thickness preoperatively and at 1, 3, 6 and 12 months postoperatively.

Study results showed that total corneal thickness increased from 610 µm preoperatively to 680 µm at 1 month and 660 µm at 3 months. Graft thickness was 170 µm at 1 month, 157 µm at 3 months and stable at 12 months.

LogMAR BCVA improved from 0.44 preoperatively to 0.26 at 3 months and 0.16 at 12 months. The gains were statistically significant.

Data showed no association between postoperative corneal or graft thickness, BCVA and forward light scatter, the authors said.

This well-designed study shows that mean best corrected visual acuity as well as low contrast visual acuity improve through at least 12 months after DSEK. The visual improvement is associated with a reduction in forward light scatter as preoperative sub-epithelial haze in the host cornea decreases with time after DSEK. The graft thicknesses ranged from about 80 µm to 340 µm and did not significantly correlate with visual acuity, which ranged from 20/16 to 20/63, in this cohort of pseudophakic Fuchs’ dystrophy patients without other significant visual limitations. However, random variation in other factors, such as mismatch between donor and recipient curvature, could mask a graft thickness effect, if one exists. As the authors note, an important relationship between graft thickness and visual acuity may exist with much thinner grafts, such as endothelium-only DMEK grafts, which have been reported to provide better postoperative visual acuity than DSEK.

– Marianne O. Price, PhD
Executive Director, Cornea Research Foundation of America, Indianapolis