Intra-corneal rings or intacs
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INTACS (intra-corneal rings) are polymethylmethacrylate segments that are surgically fitted into the core corneal stroma to even out the central cornea. INTACS are currently manufactured and marketed by Addition Technologies. More and more eye specialists are choosing this optical application for the treatment of various eye conditions like keratoconus, “forme frusta” keratoconus with mild myopia, post-LASIK ectasia, pellucid marginal degeneration and cornea that is too fragile for supplementary uplift after undergoing a LASIK for myopia.

History of the development of INTACS

INTACS was initially manufactured by a company named Keravision. It was originally designed and approved by the FDA for the therapy of mild myopia in the range of – 1 to – 3 Diopters. But with the invention of excimer laser and laser-assisted subepithelial keratomileusis (LASIK), INTACS became redundant. For LASIK proved more accurate and easier to implement in various refractive error conditions. Hence, Keravision went kaput and INTACS were no more considered a viable correction for myopia.

The use of INTACS for treatment of keratoconus was pioneered by Dr Joseph Colin in France. In 2001, he released a one-year follow-up and recently he came up with a five-year study on a selected group of patients and both times he reported effective results. Since his achievements, at least five other research groups have successfully proved the efficacy of INTACS for keratoconus cure.

Recently, United States sanctioned the use of INTACS for the treatment of keratoconus. However, it comes under a human device exemption, which permits its use only under the supervision of a review group. Right now, 0.25, 0.275, 0.30, 0.325, and 0.35 mm segments of INTACS are manufactured in the US. One can also get the.40 and 0.45 mm-sized segments outside the US.

It has also been reported (at least 2 published studies) that INTACS is an effective means to correct astigmatism in patients with pellucid marginal degeneration who have clear corneas but are contact lens intolerant.

Latest developments in the implementation of INTACS have suggested its potential use in performing PRK on patients after an INTACS surgery on cases with thick corneas and non-progressive type.

Symptoms and applications of INTACS

INTACS are applicable in the following conditions:

  • Mild to moderate keratoconus with clear corneas and contact lens intolerance
  • INTACS is a desired choice to penetrating or lamellar keratoplasty for eyesight correction
  • As a refractive remedy on patients wearing either contact lenses or spectacles. (However, this is not permitted in the US since it does not conform to the FDAs human device exemption approval)
  • For treatment of forme fruste keratoconus or patients with extremely fragile corneas whose myopic error is less than 3D. In fact it is a highly desired therapy since it is safer when compared to laser refractive surgery.

The surgical process

The surgical procedure consists of the following pre and post-operative steps:

  1. INTACS selection
  2. Incision
  3. Surgery
  4. Post-operative care

INTACS selection

There are various sizes of INTACS available. Hence, there are various possible permutations and combinations of INTACS as well, for implantation in the process of flattening of the core cornea and astigmatism correction. What is best is that whatever the combination used, there is always some desired result.

Incision

There are a variety of theories and no standard code regarding the place of the opening through which the INTACS is inserted. A common recommendation is to place the incision on the steepest axis.

Surgery

Originally the surgery was done using a mechanical spreader, but now-a-days a femtosecond laser (the Intralase) has come up as a close competitor.

The advantages of the femtosecond laser are:

  • Enables easy insertion of the INTACS
  • Saves time
  • Surgeon and patient friendly
  • Ensures high rate of certainty in INTACS placement, hence deters superficial placement and INTACS wear and tear
  • Allows easy reinsertion of INTACS if the first attempts are disappointing
  • Ensures speedier post-operative eyesight recuperation

Post-operative care

The main issue in post-operative care is the use of contact lenses and it is a highly challenging and evolving process. Apart from a good surgeon, one also needs a proficient contact lens provider since lens intolerance is a major cause of going for INTACS implants.
Right after the surgery a soft disposable contact lens can be safely used. Usually a contact lens of around 3D less than their preoperative spherical equivalent is suggested. This ensures maximum comfort and instant postoperative eyesight.

It is advised to use rigid contact lenses after 3 months, when the cornea is fairly settled, the stitches have been removed and the wound has healed. There have also been reports about the effectiveness of customized lenses after an INTACS surgery.

Disadvantages of INTACS

INTACS comes with its set of both intraoperative and postoperative complications. Some of them are:

  • Puncture of the anterior segment and superficial positioning of the INTACS
  • Infection from leaving the INTACS too near the edge of the incision
  • Erosion of the INTACS implant since they keep hitting each other. This results from excess rotation of the INTACS
  • Halo and glare in young patients
  • Rare problems like constant swelling, consistently unstable eyesight, intraocular sensitivity, photophobia, loss of UCVA, and loss of BCVA.
 
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