Surgical Correction of Presbyopia

Lenticular, Corneal, and Scleral Approaches

Michael Greenwood, MD; Shamik Bafna, MD; Vance Thompson, MD

Disclosures

Int Ophthalmol Clin. 2016;56(3):149-166. 

In This Article

CK

CK is the application of low-frequency radio waves to selectively modify or "shrink" collagen fibrils within the cornea. The radio waves are delivered through a fine-tipped probe applied to the peripheral corneal stroma in a circumferential band. As the collagen shrinks, the band constricts and there is a steepening of the corneal curvature central to the band. The placement, intensity, and duration of treatment affect how much steepening takes place. CK was initially used to correct low to moderate levels of hyperopia and astigmatism,[28] but, more recently, it has been used to induce monovision in presbyopes.[28,29]

One-year results from an FDA clinical trial for the use of CK to induce monovision as a treatment for presbyopia revealed J1 or better UNVA for 38% (20/53) of eyes and J3 or better for 81% (43/53) of eyes treated for near vision. Binocular UNVA of J1 or better was achieved for 47% (25/53) of patients and J3 or better for 89% (47/53) of patients. Binocular UDVA was 20/20 or better for 97% (60/62) of patients and 20/40 or better for all patients (62/62).[30] Ye and colleagues studied 27 presbyopic patients who underwent CK for monovision. Mean UNVA of the CK eye went from 0.92 (20/166)±0.16 before treatment to 0.30 (20/40)±0.13 at 12 months after treatment (P<0.05).[31] Stahl reported on 10 eyes of 10 patients who underwent CK in the nondominant eye to treat presbyopia. Preoperatively, 1 patient had binocular UDVA of 20/30 or better and UNVA of J5 or better. At 1-year post-CK (n=10) 8 patients had binocular UDVA of 20/20 or better and J1 or better UNVA. All patients had UDVA 20/40 and UNVA J3. At 3 years postoperatively (n=9), 2 patients achieved 20/20 UDVA and J1 UNVA or better and 7 achieved 20/40 UDVA and J3 UNVA or better.[32,33] CK can also been used to correct hyperopic refractive error after cataract or refractive surgery.[34–36] In a report by Claramonte, only 25% of a group of 16 eyes achieved a UDVA of 20/40 or better following cataract surgery because of residual hyperopia. After adjustment with CK, 62.5% of eyes had a UDVA of 20/40 or better at 12 months postoperative.[34]

An advantage of CK over other techniques is that it does not involve any tissue removal or addition, and it also preserves the optical clarity of the visual axis. CK is also very safe. In studies that reported safety as lines of best-corrected visual acuity lost, only 7 of a total of 770 eyes (1%) lost 2 lines of CDVA,[31–33] and these patients were involved in the initial FDA clinical trial treating hyperopia, which had exceeded FDA safety standards. It has also been shown that the there is no damage to the corneal endothelium as endothelial cell counts at the corneal periphery, mid-periphery, and centrally revealed no significant change from preoperative values after 1 year of follow-up.[34] Contrast sensitivity is also spared with CK.[34–37] One of the disadvantages of CK is that the effect can regress over the course of a few months,[32] which is the main reason for its failure to become a mainstream procedure.

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