Researchers in Germany have determined that corneal guttae cause an additional significant decrease in contrast sensitivity in eyes with nuclear cataract. They believe that contrast sensitivity might be a better indicator of visual impairment in patients with corneal guttae and nuclear cataract and could strengthen the decision for surgery.
Their study compared the contrast sensitivity measurements between 25 patients with corneal guttae and nuclear cataract and 25 patients with cataract and no corneal guttae. The patients with corneal guttae and nuclear cataract underwent triple Descemet membrane endothelial keratoplasty (DMEK). Patients with nuclear cataract and healthy corneas underwent traditional cataract surgery. Before surgery, the study group had significantly worse contrast sensitivity as measured by both MARS letters and OPTEC 6500P charts.
After surgery, there was no significant difference in MARS letter contrast sensitivity measures between the two groups. However, when the researchers using OPTEC 6500P charts, they found that contrast sensitivity remained significantly lower in the triple DMEK group in the day and night with and without glare at most spatial frequencies. The researchers believe the OPTEC 6500 contrast sensitivity test is the more detailed, photopic and mesopic test.
The study noted that preoperative and postoperative corneal volume, central corneal thickness and anterior corneal densitometry were equal in both groups. Posterior densitometry was significantly higher in the DMEK group than in the control group preoperatively but no differences were found postoperatively.
Nevertheless, the researchers recommend a triple DMEK even in eyes with a visual acuity of ≥20/40. They emphasize that visual quality is determined not only by visual acuity but also by other factors such as contrast sensitivity and color vision.
Augustin VA, Weller JM, Kruse FE, Tourtas T. Influence of corneal guttae and nuclear cataract on contrast sensitivity. Br J Ophthalmol. September 9, 2020. [Epub ahead of print].