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Kappa distance change and its relationship with corneal asphericity centration in keratoconic eyes after implantation of a double arc ICRS

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Session Details

Session Title: Photoablation, Cross-Linking and Intracorneal Ring Segment

Session Date/Time: Monday 07/09/2015 | 08:00-10:30

Paper Time: 09:00

Venue: Room 16

First Author: : E.Nakano BRAZIL

Co Author(s): :    C. Oliveira   P. Caddah   J. Saraiva Filho   C. Costa   M. Leite   H. Mello     

Abstract Details


To verify the change of kappa distance after the implantation of a double arc ICRS and its correlation with corneal asphericity and spherical aberration.


This multicenter, prospective, randomized study is being conducted at Federal University of São Paulo UNIFESP and at Hospital Oftalmológico de Brasília, HOB. The expected effect of the double arc ICRS is a central flattening, corneal asphericity modulation and centration and corneal astigmatism management.


Forty eyes of 40 patients were divided into group A (K max up to 60D) and B (K max from 61 to 75D). Eyes were also divided into two sub-groups according to the corneal astigmatism (cutoff value of 5D). For aberrometric and kappa distance measurements, OPDScan III was used. “P dist” (kappa distance) was defined as distance between the first Purkinje image and the center of the photopic pupil. Aberrometry was extracted from the central 5mm zone. Correlation between the change of kappa distance with the change of spherical aberration was also done. Right and left eyes were analyzed separately.


To date, 28 eyes completed 3 months follow up assessment (16 right eye). Preoperative “p dist” was 0.430 micra; 0.414 micra in right eyes, and 0.409 micra in left eyes. After the ICRS implantation centered in the first Purkinje reflex, p dist values were 0.392 (0.264 in OD; 0.382 in OS); 0.305 (0.115 in OD; 0.290 in OS); 0.221 (0.088 in OD; 0.270 in OS), and the amount of spherical aberration (C12) was -0.228; -0.726; -0.780 and -0.789 micra respectively after 7 days, 30 days and 3 The correlation between C12 and p dist was R2= 0,54921.


The double arc ICRS, differently from the conventional single arc one, provides the ectatic cornea a new limbus by its 8mm outer diameter ring. Since the inner 5mm ring is bounded to the outer one by bridges in a pre-determined 35 or 45D curvatute profile, the cornea is remodeled to the curvature and surface regularity imposed by the ICRS. This study shows that the kappa distance decreases after the surgery, as well as the corneal asphericity increases, corroborating the theory that the double arc ICRS plays a role in centrating the corneal vertex toward the line of sight.

Financial Interest:

One of the authors travel has been funded, fully or partially, by a company producing, developing or supplying the product or procedure presented

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