February 2009

Insights Into Post Intacs Fitting

History, Presentation, Treatment

A 42-year-old man with keratoconus was referred by his surgeon for a contact lens fitting after non-complicated surgical insertion of an Intacs (Keravision/Additive Technology) implant in the cornea of his left eye.

His preoperative status was:

MRx: –3.25 +3.50 x 35, BCVA 20/30
Pachymetry: 560 microns
Clear cornea, free of scarring and Vogt’s striae.
Topography revealed 4-mm to 5-mm central round inferior steepening.

One month post-op, the patient’s status was: MRx: –1.00 +4.00 x 030, 20/20^-2. His vision stabilized at 4 months post-op: MRx: +2.50 –1.75 x 118, 20/20^-2

I fitted this patient with a CooperVision Proclear Toric soft contact lens (8.7/14.4) +2.50 – 1.75 x 110. The fit was stable with no rotation, and the patient’s best-corrected visual acuity was 20/20.

Understanding the Intacs Patient

When Intacs are used as treatment for keratoconus, the surgeon’s goals are three-fold:

1. Improve visual acuity with and without spectacles.
2. Defer corneal transplantation. (Note that the long-term effects on keratoconus progression post Intacs implantation are unknown.)
3. Create a cornea more receptive to contact lenses.

Intacs change the shape and power of the central cornea through an arc-shortening/flattening effect. Among their advantages are that they are additive, removable and replaceable. In addition, they reposition the cone and allow a large, clear optic zone.

Candidates for Intacs surgery must demonstrate the following:

• Corneal apex at least 350 microns thick
• 450 microns of tissue in the periphery
• No scarring
• Less than 60D in steep K reading
• Signs and symptoms of contact lens intolerance (subjective or mechanical irritation from GP lenses), such as: punctate epithelial erosions, epithelial breakdown, shortened wearing time, or failure to provide functional vision (< 20/40).

Researchers have demonstrated the following results from Intacs implantation¹:

• BSCVA : 33 (45%) out 74 eyes gained > 2 lines
• UCVA: 72% gained > 2 lines
• Mean BSCVA: 20/50 pre-op to 20/32 post-op
• Mean UCVA: 20/200 pre-op to 20/80 post -op
• Statistically significant change in mean keratometry values 50.86D pre-op to 47.63D post-op.
• No statistically significant change in astigmatism; 3.33D pre-op to 3.06D post-op.

Fitting and Follow-up for Intacs Patients

Practitioners should wait at least 3 months post implantation for vision to stabilize before attempting to fit a patient with contact lenses. In fact, one study reported visual acuity, refraction and topography were not stable until 9 months post-op.²

At follow-up, be sure to monitor for postsurgical complications, such as chronic foreign body sensation, halos, keratolysis infection, channel deposits or neovascularization at the wound site.

References

1. Boxer Wachler BS, Christie JP, Chandra NS, Chou B, Korn T, Nepomuceno R. Intacs for keratoconus. Ophthalmology. 2003;110:1031-1140. Erratum in: Ophthalmology. 2003;110:1475.
2. Siganos CS, Kymionis GD, Kartakis N, Theodorakis MA, Astyrakakis N, Pallikaris IG. Management of keratoconus with Intacs. Am J Ophthalmol. 2003;135:64-70.

By Ann Laurenzi, OD, FAAO
Cleveland, Ohio

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