Corneal transplantation outcomes after the extrusion of an intrastromal keratoprosthesis: a pilot study

Nonpenetrating Foldable Intrastromal Keratoprosthesis: A Review of the Literature

PURPOSE

To review the literature focusing on the clinical outcomes of KeraKlear (KK) (KeraMed), a foldable intrastromal keratoprosthesis.

METHODS

We searched 6 databases using 4 keywords: KeraKlear, Foldable Keratoprosthesis, Intrastromal Keratoprosthesis, and Non-penetrating Keratoprosthesis. Included studies had to be conducted in vivo on humans, published until January 3, 2023, and had to investigate the implantation of the KK. Eyes were considered at high risk of keratoprosthesis retention failure whenever there was an active inflammatory ocular surface disorder or in case of previous KK failure. We aimed at recording the postoperative complications, rate of prosthesis retention, and mean improvements in visual acuity.

RESULTS

We identified 144 publications, 6 of which (38 eyes) met the inclusion criteria. No randomized controlled trials were found, and some studies had significant limitations regarding sample size and follow-up duration. With a mean follow-up of 28 ± 18.8 months, postoperative complications of any kind occurred between 0% and 50% and 24% had an implant extrusion/needed a reoperation. The mean postoperative visual acuity improvement on the last follow-up was -0.83 ± 0.27 LogMAR, that is, -0.57 ± 0.3 for high-risk and -1.03 ± 0.25 for low-risk eyes, whereas 1 year after implantation, 50% of the prostheses were retained in the former and 81% in the latter group. None of the eyes developed glaucoma, endophthalmitis, or expulsive hemorrhages; none had to be eviscerated/enucleated.

CONCLUSIONS

Despite the limited quality and quantity of evidence, the available literature seems to suggest the KK to be a valuable tool in the treatment of complicated corneal disorders. Because in many parts of the world, the access to corneal transplantation is limited, this prosthesis could represent a valid alternative.

Numerical Study of Customized Artificial Cornea Shape by Hydrogel Biomaterials on Imaging and Wavefront Aberration

The blindness caused by cornea diseases has exacerbated many patients all over the world. The disadvantages of using donor corneas may cause challenges to recovering eye sight. Developing artificial corneas with biocompatibility may provide another option to recover blindness. The techniques of making individual artificial corneas that fit the biometric parameters for each person can be used to help these patients effectively. In this study, artificial corneas with different shapes (spherical, aspherical, and biconic shapes) are designed and they could be made by two different hydrogel polymers that form an interpenetrating polymer network for their excellent mechanical strength. Two designed cases for the artificial corneas are considered in the simulations: to optimize the artificial cornea for patients who still wear glasses and to assume that the patient does not wear glasses after transplanting with the optimized artificial cornea. The results show that the artificial corneas can efficiently decrease the imaging blur. Increasing asphericity of the current designed artificial corneas can be helpful for the imaging corrections. The differences in the optical performance of the optimized artificial corneas by using different materials are small. It is found that the optimized artificial cornea can reduce the high order aberrations for the second case.

A Foldable Nonpenetrating Keratoprosthesis: Medium to Long-Term Clinical Results in Patients with Corneal Blindness due to Noninflammatory Anterior Cornea Disease

PURPOSE:

To report the medium to long-term safety and performance outcomes of the KeraKlear nonpenetrating artificial cornea (KeraKlear) as the primary procedure in patients with corneal blindness due to noninflammatory anterior cornea disease.

METHODS:

Fifteen patients with corneal blindness (preoperative visual acuity [VA] of ≥20/200) due to a non-inflammatory anterior corneal condition were included in this prospective, single-center study. Preoperative diagnoses included corneal scars, keratoconus, and corneal dystrophies. Diseased corneas were implanted with the KeraKlear (KeraMed Inc., Irvine, California, USA) by a single surgeon (JMV) using a femtosecond laser to create all incisions. Participants were followed up with for as long as 64 months. Uncorrected Snellen VA and postoperative complications were recorded.

RESULTS:

The average age at the time of surgery was 49.6 years old and 67% of patients were female. The patients experienced an average improvement in uncorrected Snellen VA of 7.6 lines (−1.17 logMAR). Average uncorrected vision at the last visit was 20/100 (0.73 logMAR), and median uncorrected vision at the last visit was 20/70 (0.54 logMAR). One patient experienced extrusion of the KeraKlear due to infection. There were no cases of glaucoma, retroprosthetic membrane, or endophthalmitis, the three most common complications of penetrating keratoprostheses (KPro).

CONCLUSIONS:

Medium and long-term outcomes of the KeraKlear indicate that this device is a viable alternative to corneal transplantation as a primary procedure in patients with non-inflammatory causes of corneal blindness, especially when corneal tissue is not available. The KeraKlear does not penetrate into the anterior chamber, and therefore, is less susceptible to the most common complications of penetrating KPro including endophthalmitis, glaucoma, and retroprosthetic membrane. The KeraKlear also has a comparable or improved adverse event rate compared to penetrating keratoplasty.