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Up Front | Nov 2002

Refractive Challenge

Toric Treatments With Conductive Keratoplasty

A 53-year-old white female presented for a consultation on vision correction. She had a history of hyperopic astigmatism, exotropia with complaints of diplopia, and dry eyes. As an office administrator, she spent many hours daily in front of a computer.

On examination, the patient's BSCVA was a variable 20/20- OU with a manifest refraction of +2.50 -2.00 X 15 OD and +1.50 -1.00 X 180 OS. The slit lamp examination revealed dryness of both ocular surfaces, but was otherwise unremarkable. With her distance correction, she had an exotropia of 14.0 PD at distance and 25.0 PD at near. After a lengthy discussion with the patient, we decided to proceed with strabismus surgery and dry-eye treatment, followed by a contact lens trial. At that point, we would discuss her refractive surgical options.

I performed a left lateral rectus recession on an adjustable suture and, 1 month later, permanently occluded the puncta of the lower lids bilaterally. The diplopia resolved, and the patient's dry eye symptoms improved. She tried four different combinations of soft contact lenses (toric, nontoric, monovision, and emmetropia correction)—all without success. With the contact lenses, the patient's distance vision varied, her BCVA was rarely better than 20/30, and she became increasingly interested in pursuing her refractive surgical options.

1. Would you continue attempting to fit the patient with contact lenses?
2. Recommend hyperopic/astigmatic surface ablation (PRK/LASEK)?
3. Would you recommend hyperopic/astigmatic LASIK?
4. Recommend clear lens exchange (with or without AK)?
5. Await FDA approval of phakic IOLs?
6. Recommend hyperopic/astigmatic CK?

I had performed hyperopic LASIK on the patient's sister 1 1/2 years earlier and treated her nondominant eye successfully for monovision. The patient's dry eye problem made me decide against hyperopic LASIK in her case. We discussed other options such as clear lens exchange (with or without limbal relaxing incisions) and investigational techniques such as phakic IOLs. The patient was outside the age range for the hyperopic STAAR ICL study (STAAR Surgical, Monrovia, CA) and was not particularly interested in an intraocular procedure. Although, due to astigmatism, the patient's refractive error fell outside the FDA-approved range of correction for CK, I thought that the procedure still warranted consideration.

Understanding the experimental nature of the treatment, she agreed to become the first patient treated with CK for hyperopic astigmatism in the US. She desired correction for distance vision and accepted that she would need reading glasses postoperatively. From a surgical perspective, my biggest concern was the nomogram; the safety of CK has always been impressive, and postoperative worsening of dry eye symptoms is exceedingly rare. The patient understood that an enhancement would likely be necessary. She desired correction of both eyes simultaneously, which seemed reasonable given the relatively low astigmatic correction OS.

Figure 1A and B show the surgical plan for both eyes. The concept was to neutralize the astigmatism by widening the spherical portion of the treatment zone along the steep meridian and adding treatment spots along the flat meridian.

The procedure was uneventful. Postoperatively, the patient did well, returning to work 4 days after the surgery with over-the-counter, +1.25 D reading glasses. Two months after the procedure, her UCVA was 20/40 OD and 20/20 OS. She refracted to 20/20 OU with +1.00 -0.50 X 110 OD and -0.25 sphere OS (Figure 1C and D).

The patient was extremely pleased but began to contemplate the possibility of correcting her nondominant eye in order to improve her reading vision. Interestingly, a spherical soft contact lens trial for monovision correction OD worked well, and we have planned enhancement surgery.

Following FDA approval in April 2002, CK has gained increased acceptance among ophthalmologists as a safe and effective technique for correcting low to moderate hyperopia.1,2 The data from the multicenter FDA clinical trial demonstrated that 92% of eyes had a UCVA of 20/40 or better and that 60% of eyes achieved 20/20 or better UCVA 12 months postoperatively. Of the 318 eyes with 12 months follow-up, none has experienced a loss to date of more than two lines of BSCVA. The mean baseline cycloplegic spherical equivalent refraction was +1.86 ± 0.63 D with a range of +0.75 to +4.00 D.

Although CK is FDA-approved for spherical hyperopia (<1.0 D of refractive cylinder), other potential indications exist. Because of CK's impressive safety profile, it is well suited for monovision induction in presbyopic emmetropes.2 I have also used CK to fine tune LASIK outcomes (either overcorrected myopic LASIK or undercorrected hyperopic LASIK) when lifting the flap and/or removing additional tissue are not desired. Pseudophakes are candidates for CK when a small hyperopic refractive error exists, and I have successfully used CK within the incisions of post-RK hyperopes to create what I call a “radio-suture.”

Because the collagen shrinkage induced by CK steepens the central cornea when the energy is applied at least 3 mm from the corneal center, the procedure should, in theory, be a powerful tool for correcting astigmatism. Although the nomograms are still being developed, Figures 2 and 3 illustrate CK's cylinder-neutralizing capability. Antonio Mendez, MD, of Mexicali, Mexico, developed the CK procedure.3 He and his son, Benjamin Mendez Noble, MD, also of Mexicali, discovered that CK can create a coupling effect, when applied in certain patterns, that corrects astigmatism without significantly affecting the spherical equivalent.

Although in CK the current emphasis has been on enabling patients to see without glasses and contact lenses, additional uses may include specific astigmatism treatments to allow toric or RGP contact lens wearers to begin wearing spherical soft contact lenses. Refinements to the nomograms for toric treatments are ongoing, and continued study will be needed to evaluate fully the safety and efficacy of these new applications for CK.

Jonathan M. Davidorf, MD, is Director of the Davidorf Eye Group in West Hills, California, and is an assistant clinical professor at the Jules Stein Eye Institute. He is a consultant for Refractec, Inc. (Irvine, CA). Dr. Davidorf may be reached at (818) 883-0112; drj@davidorf.com.
1. McDonald MB, Davidorf JM, Maloney RK, Manche EE, Hersh P. Conductive keratoplasty for the correction of low to moderate hyperopia: 1-year results on the first 54 eyes. Ophthalmology. 2002;109:637-649.
2. Davidorf JM, Durrie DS, Pallikaris I. Conductive keratoplasty. In: Agarawal A, ed. Presbyopia: A Surgical Textbook. Thorofare, NJ: Slack, Inc.; 2002:165-173.
3. Davidorf JM, Mendez-Noble B. Conductive keratoplasty for the treatment of mixed astigmatism. Paper presented at: Symposium on Cataract, IOL and Refractive Surgery; June 4, 2002; Philadelphia, PA.
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