Purchase this article with an account.
Nicolas Alejandre-Alba, Pablo Perez-Merino, Silvia Quintana, Pedro Pascual, Ignacio Jimenez-Alfaro, Susana Marcos; Scheimpflug-based derived aberrometry before and after implantation of different combinations of intracorneal ring segments (ICRS) in keratoconus. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3947.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To analyze the changes in corneal aberrations induced by different combinations of triangular section ICRS in keratoconic eyes
86 keratoconic eyes were evaluated with Scheimpflug tomography (Pentacam by Oculus) before and three months after ICRS implantation (Ferrara-type, triangular section). Corneal aberrations were estimated by virtual ray tracing on anterior and posterior corneal elevation maps, using Zemax, in a 4-mm area centered in the eye’s pupil. Eyes were divided in groups according to the combination (1 or 2) , geometry (optical zone diameter, OZ, 5 or 6 mm, and ICRS angle, 90, 60, 160, 210 deg); and location (inferior I or superior S) of implanted ICRS: 1-OZ5-160I (6 eyes); 2-OZ5-160I-90S (6 eyes); 1-OZ5-210I (5 eyes) ; 2-OZ6-120I-90S (5 eyes) : 2-OZ6-120I-120S (14 eyes); 2-OZ6-150I-90S (8 eyes); 1-OZ6-150I (19 eyes); 1; OZ6; 210I (8 eyes). Changes in corneal aberrations were analyzed by group.
On average ICRS decreased corneal astigmatism by 43% (p<0.001) and corneal coma by 18% (p=0.056). However trefoil increased by ~20% and the overall amount of HOA did not decrease significantly. 5 mm OZ ICRS overall tended to reduce HOA by 39,4% (p=0.09), on average changing coma from 1.23±0.54 μm preop to 0.84±0.50 μm postop (p<0.05), and astigmatism from -5.4±2.6 D preop to -3.5±2.4 D postop (p<0.05). 6 mm OZ ICRS decreased corneal astigmatism (from -5.79±3.17 D preop to -3.14±2.11 D postop; p<0.001) but did not systematically decrease other aberrations. Across groups, coma decreased substantially in 1-OZ5-160I and 1-OZ5-210I (by 21.7% and 39,3%, respectively) and slightly in 2-OZ6-120I-120S (by 12.7%) but increased in 2-OZ6-120I-90S (by 2,9%). Conversely, astigmatism decreased significantly (p<0.05) in the last two groups (by 72,8% and a 55,4% respectively).
Estimations of corneal aberrations in patients implanted with ICRS allows evaluation of the optical changes, rather than corneal shape alone. 5 mm OZ ICRS decrease efficiently corneal aberrations. While 6 mm OZ ICRS produce the largest improvement of astigmatism. Understanding the relationships between ICRS geometry /implantation pattern and the change in optical aberrations is crucial to refine nomograms.
This PDF is available to Subscribers Only