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Asymmetric Intrastromal Corneal Ring Segments

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Keratoconus

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Abstract

Irregularities in keratoconic eyes do not tend to be uniform. They can be steeper in one area of the cornea and flatter in another. Intracorneal ring segment (ICRS) implants have been used to correct surface irregularities in keratoconic eyes since the early 2000s. The thickness of a standard ICRS is uniform, so the flattening effect of the segment is the same across the length of the ring. This factor requires that the surgeon make a decision on which area to flatten most at the expense of another. The presence of a corneal inlay may provide biomechanical support for ocular tissue. Eyes that underwent ICR implantation show overall flattening of the cornea, dislocation of the corneal apex toward the center, preservation of corneal asphericity, and decreased surface irregularity. A progressive-thickness ICRS was introduced to treat nonuniform irregularities of the cornea in ectatic corneal disorders. As the name suggests, the ring thickness in a progressive-thickness ICRS increases or decreases from one end to the other, thus producing a progressive corneal flattening effect. Progressive-thickness ICRS offers variable thickness within the same device—it is thinner on one end and thicker on the opposite end. The two versions, 160° and 330° arcs, have gradual thickness variations ranging from 150 μm to 250 μm and 200 μm to 300 μm. The 160° asymmetric rings are available in both chiral configurations (clockwise and counterclockwise). Progressive-thickness or asymmetric ICRS may decrease surface irregularity in corneas with great asymmetry.

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Acknowledgments

Luiz Cruz provided assistance with the clinical photographs.

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Authors and Affiliations

  1. Optical Surgery, Department of Ophthalmology, Federal University of Sāo Paulo, São Paulo, SP, Brazil

    Marta Beatriz de Filippi Sartori, Allyne Mota Kalaf & Luiz Ito da Cruz

  2. Department of Ophthalmology, Diadema Municipal Medical Specialty Center, São Paulo, SP, Brazil

    Marta Beatriz de Filippi Sartori

Authors
  1. Marta Beatriz de Filippi Sartori
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  2. Allyne Mota Kalaf
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  3. Luiz Ito da Cruz
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Correspondence to Marta Beatriz de Filippi Sartori .

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Editors and Affiliations

  1. Provisão Eye Hospital of Maringá, Maringá, Paraná, Brazil

    Edna Almodin

  2. Federal University of São Paulo, São Paulo, São Paulo, Brazil

    Belquiz Amaral Nassaralla

  3. Nucleo de Medicina Ocular, Goiânia, Goiás, Brazil

    Jordana Sandes

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de Filippi Sartori, M.B., Kalaf, A.M., da Cruz, L.I. (2022). Asymmetric Intrastromal Corneal Ring Segments. In: Almodin, E., Nassaralla, B.A., Sandes, J. (eds) Keratoconus . Springer, Cham. https://doi.org/10.1007/978-3-030-85361-7_50

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  • DOI: https://doi.org/10.1007/978-3-030-85361-7_50

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  • Publisher Name: Springer, Cham

  • Print ISBN: 978-3-030-85360-0

  • Online ISBN: 978-3-030-85361-7

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