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Introduction and practical application of KERARING rings

Indications for using Kerring

1. In keratoconus (IV, III, II, I Amsles) who cannot tolerate contact lenses and in progressive keratoconus. 2. In Pellucid Marginal Degeneration 3. In Iatrogenic Ectasia: – In ectasia after PRK, LASIK – In Irregulaz Astigmatism after PKP – In Irregulaz Astigmatism after PK 4. In the treatment of Corneal irregularities after trauma

The mechanism of action of karring

1. The effects of Kerring are done in the following way:

– Since it works by the technique of adding tissue to the cornea, it causes the remodeling of the cornea, the result of which is the strength of the cornea. – By regularizing the topography of the cornea and correcting the refraction, the profile of the cornea goes to the normal side and the optical aberration is reduced, which results in better visual acuity and contact lens tolerance. – Corneal Apex goes to the middle of the pupil. – It stabilizes the cornea and delays or eliminates the need for a cornea transplant.

2. Effects of ring sizes:

– Long rings 150, 160, 180, 210, 320, 325, 330 degrees cause cylinder correction and myopic correction (with Flattening mechanism) – short rings (90). 120 degrees (they only cause cylinder correction. Note: the effects of corneal smoothing in myopia depend on the total volume of the coring part: this means that long rings have a volume of k and short rings have a low volume, so rings with The volume of the myopic tank and cylinder are corrected, and the rings of the cylinder are corrected for the low volume.

3. Ring models: Karring has three models:

– SI-5 : 5 mm zone direction, which has 90, 120, 160, 210 degree pieces, each of which has a thickness of 150, 200, 250, 300, 350 microns, and the width of each ring is 600

It is a micron. – SI-6 : 6 mm zone direction, which has 90, 120, 150, 210 degree pieces, each of which has a thickness of 150, 200, 250, 300, 350 microns, and the width of each ring is 800 microns. – New rings 320 , 325 and 350 degrees that are placed in 5.7 mm zone. They have four thicknesses of 150 , 200 , 250 and 300 microns, and the 325 and 330 can be used in pocket and tunnel.



A) Information required for ring operation:

1. Topography) Ant. Elevation map- Axil map- Sagittal (curvature map

2. Full page pachymetry map with full details

3. Manifest refrection (subjective)


5. Coma map/ axis

B) Corneal Asymmetric classification and use of nemogram:


Rings usage

– In the tables, the selected rings are one or two rings, the first number of each ring is the arc of the ring and the second number of each ring is the ring thickness. For example, in the ring 160/300, the number 160 represents the degree of arc of the ring and the number 300 represents the thickness of the ring.

– If the rings suggested by the nemogram are two pieces, the back piece is placed on the flatter side and the lower ring is placed on the steeper side of the steep axis ratio.

– If a ring is suggested by the nemogram, that ring is placed on the steeper side.

The cases where 6-SI rings are used are as follows

1. Mesopic pupil diameter > 0.7, BCVA more than 5 mm 5D under Cylindezvalue, BCVA > 0.6

2. 5D under Cylindezvalue, BCVA > 0.6

3. When the thickness of the cornea in the region of 5 mm is not enough, if
If the cylinder is below 5 diopters, 6-SI rings can be used.

4. When PRK or Phakic IOL placement is the second treatment method after the ring, if the cylinder was below 5D.

Indication and nemogram for choosing 340 and 355 rings

These rings are indicated in central (nipple keratoconus) and are selected as follows:


200μm thickness: for spherical equivalent < 6 D.

300μm thickness: for spherical equivalent > 6 D.



The ring thickness should never exceed 60% of corneal thickness on the ring zone. The central cornea pachymetry is not relevant to ring thickness or tunnel depth.


1- Central marking on light relfex (visual axis), not center of the pupil




3- In manual operation, a diamond knife with a square blade is used and a vertical cut is made to a depth of 80% of the thickness of the thinnest point of the working area of the ring and in the place of the steep axis. 4- By using Micro dissector and spreader tools, the beginning of the desired tunnel is opened, and then the desired tunnel is created with right round and left round maker tools (tunnel dissector).


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Fanaavaran Building , 4th Danesh Alley, Danesh st, 20th km of Damavand Road (Main Street), Pardis Technology Park , Tehran-Iran

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