Topical anesthesia was used for all procedures. Surgery was performed by one (
references 14–16, 27–37, 39–46, 48, 50–53, 55–57, 59, 60, 62, 63, 65, 66, 70–78, 81–84, 86, 88–94, 98–102, 104–110, 112–116), two (
references 8, 26, 38, 47, 49, 58, 61, 67–69, 79, 80, 85, 87, 95, 96, 111), or more
54,64,97,103 surgeons using a manual (
references 8, 31, 35, 36, 43, 44, 48, 49, 55, 61, 65, 71, 72, 75–78, 81, 83–85, 91, 94, 95, 101, 102, 104, 108, 111, 113, 114) or femtosecond laser-assisted technique (
references 14–16, 26–30, 32–34, 37–42, 45–47, 50–54, 56–60, 62–64, 66–70, 72–74, 79, 80, 82, 86–90, 92, 93, 96–100, 103, 105–110, 112, 115, 116) for the creation of the intrastromal pocket. The reference point was a Sinskey hook marking the center of the pupil. Channel depth varied between 70% (
references 14–16, 33, 35, 37, 48-54, 63, 65, 66, 70, 80, 82, 83, 87, 88, 90, 92, 95, 98, 99, 102, 103, 105, 108, 109, 111, 113, 114), 75% (
references 26, 27, 34, 39, 41, 42, 45, 58, 60, 64, 71, 79, 110), or 80% (
references 8, 29, 30, 32, 33, 43, 47, 54–56, 59, 62, 67–69, 72–78, 81, 84, 85, 93, 94, 97, 103, 107, 112) of the thickness at the ring site, which was measured by ultrasonic pachymetry. The degree of the channel was determined using nomograms of specific ICRS used or was a 360-degree
15,16,26,32,34,36,39,96 tunnel for inserting the segments. Five ICRS were used: Keraring (Mediphacos, Belo Horizonte, Brazil) (
references 8, 16, 27, 28, 31, 32, 36, 41, 42, 47, 54, 55, 58–61, 64, 66, 67, 69, 70, 77, 80, 88, 92, 93, 97–99, 102, 103, 107, 110, 112, 116), Ferrara ring (Ferrara Ophthalmics, Belo Horizonte, Brazil) (
references 14, 30, 35, 43, 62, 63, 76, 78, 81, 82, 84, 85, 89, 91, 94, 101, 104), Intacs (Addition Technology, Inc., Des Plaines, IL) (
references 16, 26, 33, 37, 39, 40, 45, 46, 48, 49, 52, 53, 56, 58, 65, 71–75, 79, 83, 87, 89, 90, 95, 96, 99, 102, 103, 105, 106, 108, 109, 111, 113–115), CornealRing (Visiontech Medical Optics, Belo Horizonte, Brazil),
38,72 and Myoring ICR (Dioptex, GmbH, Linz, Austria).
15,32,34,44,57,86,100 The thickness and arc length of segments were also defined by nomograms and topography when several rings could be used, except in two studies evaluating a specific ICRS.
36,95 The steepest corneal topographic axis was selected as the incision point in all studies except nine (
references 15, 26, 46, 83, 84, 109, 111, 113, 114). Optical zone diameter varied between 5 and 7 mm and was not specified in 36 studies (
references 16, 29, 32, 33, 36, 39, 42, 45, 48, 50–52, 54, 58, 62, 64, 65, 72, 75, 85, 86, 89–91, 95, 96, 100, 101, 103, 104, 106, 111, 113–115). When the optical zone was 5 mm (
references 15, 27, 30, 31, 34, 35, 43, 44, 53, 57, 59–61, 67–70, 77, 78, 80, 81, 84, 88, 92–94, 103, 107, 110), the inner diameter varied from 4.4
35,59,60,88,107,110 to 5.4 mm,
77 and the outer diameter varied from 5.6
23,48,49,77,96,99 to 7.0 mm.
77 When the optical zone was 6 mm,
14,63,71,82,87 the inner diameter varied from 6.0
14,63,82 to 6.6 mm,
87 and the outer diameter varied from 7.0
8 to 7.5 mm.
87 Finally, when the optical zone was 7 mm,
83,102,108,109 the inner diameter was 7 mm and the outer diameter was 8.2 mm. One or two rings were inserted depending on the keratoconus grade in 44 studies (
references 8, 14, 26–30, 32, 41, 49–51, 53–55, 59–61, 67, 68, 75–77, 80, 82, 84, 85, 87–89, 92–94, 96, 97, 102, 103, 107, 109, 110, 112, 116). In 20 studies, only one ring was systematically set up (
references 15, 34–37, 39, 40, 43, 44, 46, 48, 52, 56, 57, 63, 66, 70, 71, 78, 95). In 10 studies, two rings were systematically inserted (
references 65, 72, 74, 79, 83, 105, 108, 111, 113, 114). The number of rings inserted was not specified in 21 studies (
references 16, 31, 33, 38, 42, 45, 47, 58, 62, 64, 69, 73, 81, 86, 90, 91, 98–101, 104, 106, 115). At the end of the procedure, the incision was sutured using 10-0 nylon (
references 26, 37, 46, 48–50, 55, 56, 65, 71, 73, 75, 79, 83, 84, 87, 89, 95, 96, 102, 108, 111, 113). In other studies, the incision was not sutured. Postoperative treatments were antibiotics (quinolone [
references 8, 26, 28, 29, 32, 34, 37, 39, 40, 46, 50, 52, 53, 56, 66, 67, 70, 71, 73, 78–80, 84, 85, 88, 89, 91, 96, 98, 99, 101, 104, 111, 116], aminoglycoside [
references 14, 15, 30, 31, 35, 41, 43, 50, 51, 55, 59, 60, 63, 64, 68, 69, 74–77, 82, 87, 93, 97, 103, 109, 112], or chloramphenicol [
references 35, 36, 42, 62, 65, 72, 81, 83, 88, 92, 102, 107, 108, 110, 113, 114]), steroids (
references 14, 15, 26, 28–32, 34–37, 39–43, 46, 48, 50–53, 55–57, 59, 60, 62–85, 87–91, 93, 96–99, 101–104, 107–116), nonsteroid anti-inflammatory,
8,28,41,46,85,101,104 and/or artificial tears (
references 8, 26, 28, 29, 32, 36, 42, 46, 55, 57, 59, 60, 62, 64, 67, 69–71, 73, 82, 89, 97, 101, 103, 104, 107, 109). Treatments were administrated from 5
34,37,46,64 to 45
36 days after the procedure.