Histopathologic Analysis of Explanted KAMRA Corneal Inlays Demonstrating Adherent Fibroconnective Tissue Scar Formation

BCLA CLEAR Presbyopia: Management with corneal techniques

Corneal techniques for enhancing near and intermediate vision to correct presbyopia include surgical and contact lens treatment modalities. Broad approaches used independently or in combination include correcting one eye for distant and the other for near or intermediate vision, (termed monovision or mini-monovision depending on the degree of anisometropia) and/or extending the eye's depth of focus [1]. This report reviews the evidence for the treatment profile, safety, and efficacy of the current range of corneal techniques for managing presbyopia. The visual needs and expectations of the patient, their ocular characteristics, and prior history of surgery are critical considerations for patient selection and preoperative evaluation. Contraindications to refractive surgery include unstable refraction, corneal abnormalities, inadequate corneal thickness for the proposed ablation depth, ocular and systemic co-morbidities, uncontrolled mental health issues and unrealistic patient expectations. Laser refractive options for monovision include surface/stromal ablation techniques and keratorefractive lenticule extraction. Alteration of spherical aberration and multifocal ablation profiles are the primary means for increasing ocular depth of focus, using surface and non-surface laser refractive techniques. Corneal inlays use either small aperture optics to increase depth of field or modify the anterior corneal curvature to induce corneal multifocality. In presbyopia correction by conductive keratoplasty, radiofrequency energy is applied to the mid-peripheral corneal stroma, leading to mid-peripheral corneal shrinkage and central corneal steepening. Hyperopic orthokeratology lens fitting can induce spherical aberration and correct some level of presbyopia. Postoperative management, and consideration of potential complications, varies according to technique applied and the time to restore corneal stability, but a minimum of 3 months of follow-up is recommended after corneal refractive procedures. Ongoing follow-up is important in orthokeratology and longer-term follow-up may be required in the event of late complications following corneal inlay surgery.

KAMRA presbyopic inlay refractive outcomes: a Canadian perspective

OBJECTIVE

To retrospectively analyze the visual outcomes of KAMRA (AcuFocus Inc, Irvine, Calif.) inlay insertion in a cohort of patients reporting success of procedure, complications, patient satisfaction, and refractive outcomes.

DESIGN

Retrospective trial at the TLC Laser Centre, Toronto.

METHODS

A total of 5 surgeons at the practice inserted 35 KAMRA inlays in 35 patients between October 2012 and June 2014. Some patients had a sole KAMRA inlay insertion, whereas others had combined laser vision correction (LVC) and KAMRA inlay on either the same day or sequentially. There was a small cohort of patients who had previous unrelated LVC. Mean time of follow-up was 299 days.

RESULTS

After KAMRA inlay insertion there was a significant improvement in uncorrected near visual acuity (p = 0.00009), uncorrected intermediate visual acuity (p = 0.00006), and uncorrected distance visual acuity (p = 0.02), but levels of patient dissatisfaction were 43%. The most common cause for dissatisfaction was requirements for readers (23%), followed by dysphotopsias (11%). The explantation rate was 11.42%, and 28.5% of patients required enhancements after inlay insertion.

CONCLUSIONS

The KAMRA corneal inlay has significant improvements in uncorrected near visual acuity, uncorrected intermediate visual acuity, and uncorrected distance visual acuity when used in isolation or combined with LVC. Appropriate patient selection is crucial. This procedure should not be used as first-line presbyopia management because of low levels of patient satisfaction, biocompatibility concerns, and explantation rates.

Surgical Technique to Treat Presbyopic Inlay-Associated Corneal Haze With Sequential Excimer Photoablation: A Case Series

PURPOSE

To describe an approach using sequential excimer laser ablation of the stromal surface of the corneal flap with or without subsequent excimer ablation to the stromal bed to reduce presbyopic inlay-associated corneal haze.

METHODS

Twelve patients who underwent KAMRA inlay (Acufocus) explantation due to corneal haze were included. The mean interval between explantation and the primary surgery (phototherapeutic keratotomy [PTK] to corneal flap) was 16.2 ± 29.7 months (range = 1 to 83 months). The corneal flap was lifted and laid on an evisceration spoon and an excimer laser was used to ablate the flap stroma by 30 to 40 µm depth. Subsequently, an excimer laser was used to ablate and treat the stromal bed following a second flap lift according to the manifest refraction, leaving a minimal residual stromal bed thickness of greater than 300 µm. For both procedures, mitomycin C 0.02% was applied to the stromal bed before the flap was replaced and a bandage contact lens applied.

RESULTS

Reductions in corneal haze were observed, following PTK to the corneal flap with or without photorefractive keratectomy (PRK) to the stromal bed, both clinically and on imaging. No significant changes in uncorrected distance visual acuity (P = .442) and corrected distance visual acuity (P = .565) were observed. Improvements were observed for both spherical equivalent refractive errors (P = .036) and corneal light backscatter (P = .019). There were significant improvements in spherical aberrations (P = .014) but no changes in total lower and higher order aberrations.

CONCLUSIONS

PTK to the corneal flap with or without subsequent stromal bed PRK is an effective technique in treating corneal haze following presbyopic inlay explantation. [J Refract Surg. 2023;39(9):639-646.].

Explantation of KAMRA Corneal Inlay: 10-Year Occurrence and Visual Outcome Analysis

PURPOSE

To evaluate 10 years of KAMRA corneal inlay explantation and associated visual outcomes.

PATIENTS AND METHODS

Single-site retrospective chart review of 22 cases of AcuFocus KAMRA Inlay (ACI7000PDT) explantation (range 1 week-1 year). Uncorrected distance visual acuity (UDVA), uncorrected near visual acuity (UNVA), corrected distance visual acuity (CDVA), and manifest refraction at 1 day, 1 week, 1 month, 3 months, 6 months, and 1 year post-explantation were reviewed.

RESULTS

The explantation rate was 8.2% across 10 years. All patients underwent KAMRA explantation due to dissatisfaction with their vision including blurry near vision, impaired night vision, decreased vision in dim lighting, streaks or halos, haze, and double vision. Mean UDVA pre-implant was -0.01±0.13 logMAR (logarithm of the minimal angle of resolution), 0.30±0.22 logMAR pre-explant, and 0.16±0.15 logMAR post-explant (n=20). Mean UNVA pre-implant was 0.37±0.09 logMAR, 0.38±0.13 logMAR pre-explant, and 0.42±0.21 logMAR post-explant (n=20). Mean CDVA pre-implant was -0.01±0.04 logMAR and 0.05±0.11 logMAR post-explant (n=17). Mean CDVA pre-explant was 0.04±0.07 logMAR and 0.04±0.11 logMAR post-explant (n=19). Significant differences were observed between pre-implant and post-explant UDVA (p=0.009), and between pre-explant and post-explant UDVA (p=0.02). All patients (100%) had 20/20 or better CDVA pre-implant but decreased to 73.7% post-explant. Sixty percent (12/20) of the patients lost UDVA Snellen acuity lines post-explant. MRSE was -0.31±0.29 D pre-implant and +0.26±0.77 D post-explant (p=0.007) with note of a hyperopic shift. The hyperopic shift in 31.6% (6/19) of patients did not resolve after explantation. Post-explant residual corneal haze occurred in 72.7% (16/22) of patients.

CONCLUSION

Although the KAMRA corneal inlay is a removable device, patients may experience residual corneal haze, hyperopic shift, and deficits in UDVA after explantation compared to pre-implantation UDVA.

Inlays and the cornea

Presbyopia is a growing problem in view of an aging global population and increasingly patients desire spectacle-free solutions to address this condition. Surgically implanted corneal inlays have been the topic of renewed research efforts in the past several years as a treatment option for presbyopia, with several approaches being used to modify the refractive properties of the cornea and enhance near vision. In this review we discuss historical approaches to corneal inlay surgery, critically appraise the current generation of presbyopia-correcting corneal inlays and their associated complications and consider the future prospects for emerging corneal inlay technologies that aim address the shortcomings of currently available inlays.