Keratometric index variation in keratoconic eyes before and after Intacs-SK implantation

Resumo

Purpose: To evaluate the variation in keratometric index (KI) in eyes with keratoconus (KC), before and after the implantation of Intacs SK (Addition Technology Inc); Patients and Methods: 19 eyes with keratoconus, before and after Intacs-SK implantation (minimum follow-up of 6 months), and a control group of 26 healthy eyes were retrospectively studied. The anterior (ARC) and posterior radius of curvature (PRC), the ratio between them (ratio ARC/PRC) and the mean pupil power (MPP) were evaluated for the central 3 mm, using a tomographic system combining Scheimpflug photography and placido-disc analysis. The KI was calculated using the paraxial formula for thin lens, assuming the MPP (accessed by ray-tracing) as the true corneal power; Results: The mean values for ARC, PRC, ratio ARC/PRC and KI were, respectively, for the control group and for the keratoconic eyes before surgery: 7,71±0,30 e 6,78±0,52mm (p<0,05); 6,35±0,67 e 5,59±0,86mm (p<0,05), 1,236±0,220 e 1,234±0,159 (p>0,05); e 1,3317±0,0031 e 1,3321±0,0521 (p>0,05). In keratoconic eyes, after a mean follow-up of 9,47 months after Intacs-SK implantation, the ARC increased to 7,26±0,56mm (p<0,001), and the PRC increased to 5,63±0,95mm(p>0,05), which was not statistically significant. The mean ratio ARC/PRC increased to 1,314±0,190 (p<0,05) and the mean KI decreased to 1,3285±0,0817 (p<0,05); Conclusions: After Intacs-SK implantation, only the anterior cornea surface seems to be significantly flattened, with a consequent decrease in the KI. Thus, the standardized KI values may not be suitable for intra-ocular lens calculation in these patients. No statistical differences were found in the ratio ARC/PRC and in the KI between normal and keratoconic eyes.