April 2019

CORNEA

Contact lens-assisted crosslinking approach refined, expanded


by Vanessa Caceres EyeWorld Contributing Writer


UV barrier-free soft contact lens soaked in riboflavin

The contact lens is then placed on the cornea, and this increases the functional corneal thickness by a mean of 107+–9.4 µ (90–124 µ). UV-A irradiation is continued.
Source (all): Soosan Jacob, MS, FRCS

 

As corneal crosslinking (CXL) continues to expand around the globe, one surgeon’s approach to treat thin corneas also continues to grow in popularity.
The method is contact lens-assisted corneal crosslinking (CACXL), and it was created by Soosan Jacob, MS, FRCS. The technique was originally published in 2014, and Dr. Jacob began to perform it in 2012.1
Dr. Jacob developed the idea behind CACXL after seeing patients who would be suitable for CXL but who did not have the minimum corneal thickness (400 microns after removing epithelium) considered safe for treatment. One potential treatment option is corneal transplantation, but that seemed extreme to perform just because the cornea was thin, Dr. Jacob said. She also saw some patients treated with hypotonic CXL, but noticed the results were not always ideal and that sometimes the patient would not get the required thickness.

CACXL technique

With CACXL, Dr. Jacob works with corneas that are less than 400 microns. Iso-osmolar riboflavin 0.1% in dextran or riboflavin in HPMC (VibeX Rapid, Avedro) is applied every 3 minutes for 30 minutes after epithelial removal. Patients then use an ultraviolet (UV) barrier-free soft contact lens that has also been simultaneously soaked in riboflavin for 30 minutes. The contact lens adds approximately 100 microns of functional thickness. Ultraviolet-A treatment can begin, along with iso-osmolar riboflavin 0.1% applied intermittently as in the standard CXL technique. Dr. Jacob performs CACXL with an epithelium-off accelerated CXL protocol (10 mW/cm2 for 9 minutes). The accelerated protocol is more patient-friendly and decreases intraoperative dehydration, she said.
In an initial report of CACXL results published in 2014 in 14 eyes, the mean preop minimum corneal thickness was 377.2 microns compared to 485.1 microns after the contact lens and riboflavin use.1 Patients had an average absolute increase in minimum corneal thickness of 107.9 ± 9.4 microns; the mean stromal demarcation line depth was 252.9 ± 40.8 microns. None of the eyes had significant endothelial loss, and all had stable corneal topography at follow-up.
Use of anterior segment OCT (AS-OCT) and intraop pachymetry are important measurements before and during CACXL, Dr. Jacob said. “We’ve seen on average that the contact lens gives 110 microns of additional thickness, but to make calculations easier, it is simple to remember it as 100 microns,” Dr. Jacob advised.
This technique generally works well for corneas up to 350 microns. In very thin corneas (320–350 microns), if CACXL does not lead to the 400-micron benchmark as measured by intraop pachymetry, Dr. Jacob uses two drops of distilled water to help the functional pachymetry quickly reach 400 microns. This is quick and simple to attain since a large volume of corneal swelling is not required as the bulk of functional increase in pachymetry is already provided by the riboflavin-soaked contact lens.
Dr. Jacob said to make sure that the contact lens being used does not have a UV filter, which many contact lenses have. “If the lens has a UV filter, in effect you are doing nothing at all,” she said. She frequently uses the SofLens Daily Disposable (Bausch + Lomb), which is made with hilafilcon B and is widely available.
After treatment, patients are patched for the night and receive a new bandage contact lens the next day until epithelial healing.
Postop care for CACXL patients is similar to that for conventional CXL patients. Dr. Jacob advises patients to avoid any mechanical stress on the eye. She also monitors for keratoconus progression using refraction, keratometry, pachymetry, and Kmax measurements. As for all crosslinking procedures, she keeps a close watch on patients to check for signs of progression. “We’ve been very pleased with our results with CACXL and fortunately have an extremely low rate for retreatment,” she said.

What the studies show

More surgeons around the globe are now using CACXL as well. It is performed at about 80 branches of the hospital where she works in India. Additionally, several published studies from Dr. Jacob and other researchers provide more evidence about the effectiveness of CACXL and help refine the technique.
A 2016 study included 10 eyes and found that CACXL increased functional corneal thickness and that in vivo confocal microscopy changes were similar to those seen with conventional CXL. This study recommended the use of AS-OCT after contact lens application but before UV treatment to confirm there is a functional thickness of 400 microns or more.2
A 2017 retrospective study in the Journal of Cataract & Refractive Surgery focused on the demarcation line depth after CACXL in 21 eyes.3 Researchers found that hydroxypropyl methylcellulose-based riboflavin led to a deeper demarcation line than dextran-based riboflavin. However, both solutions were safe for the endothelium at 6 months.
A study published in Acta Ophthalmologica analyzed the biomechanical effect of CACXL in post-mortem porcine eyes and found there was about a third less of a biomechanical effect after CACXL compared with the standard approach.4 Efficacy for CACXL might be bolstered by lowering or omitting the riboflavin film on the contact lens, the authors concluded.
A study in 2015 in the Journal of Refractive Surgery, however, showed that CACXL showed greater effect in murine corneas, which are more similar to the thin corneas that CACXL treats, than in porcine corneas, which are similar to corneas with higher thickness.5 This study showed that the amount of absorbed UV light was more important in porcine than in murine corneas and that the higher oxygen availability in thin corneas potentially increases overall efficacy of crosslinking in thin corneas as compared to corneas of standard thickness.
Dr. Jacob continues to expand her study of keratoconus treatments with the corneal allogenic intrastromal ring segments technique (CAIRS). The technique uses the corneal allogenic intrastromal ring segment in patients with keratoconus, followed by either accelerated conventional or accelerated contact lens-assisted CXL. A pilot study with 24 patients found that the technique, combined with CXL, was safe and effective for keratoconus, giving significant improvements in almost all parameters including uncorrected and spectacle corrected distance visual acuity.6
Dr. Jacob has now performed CAIRS in about 80 patients.

About the doctor
Soosan Jacob, MS, FRCS
Director and chief
Dr. Agarwal’s Refractive and Cornea Foundation
Senior consultant, cataract and glaucoma services
Dr. Agarwal’s Eye Hospital
Chennai, India

Contact information
Jacob
: dr_soosanj@hotmail.com

References

1. Jacob S, et al. Contact lens-assisted collagen cross-linking (CACXL): A new technique for cross-linking thin corneas. J Refract Surg. 2014;30:366–72.
2. Mazzotta C, et al. In vivo confocal microscopy after contact lens-assisted corneal collagen cross-linking for thin keratoconic corneas. J Refract Surg. 2016;32:326–31.
3. Malhotra C, et al. Demarcation line depth after contact lens-assisted corneal crosslinking for progressive keratoconus: Comparison of dextran-based and hydroxypropyl methylcellulose-based riboflavin solutions. J Cataract Refract Surg. 2017;43:1263–1270.
4. Wollensak G, et al. Biomechanical efficacy of contact lens-assisted collagen cross-linking in porcine eyes. Acta Ophthalmol. 2019;97:e84–e90.
5. Kling S, et al. Increased biomechanical efficacy of corneal cross-linking in thin corneas due to higher oxygen availability. J Refract Surg. 2015;31:840–6.
6. Jacob S, et al. Corneal allogenic intrastromal ring segments (CAIRS) combined with corneal cross-linking for keratoconus. J Refract Surg. 2018;34:296–303.

Financial interests
Jacob
: None

Contact lens-assisted crosslinking approach refined, expanded Contact lens-assisted crosslinking approach refined, expanded
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