Are intracorneal rings still useful in refractive surgery?

TFOS DEWS II iatrogenic report

Dry eye can be caused by a variety of iatrogenic interventions. The increasing number of patients looking for eye care or cosmetic procedures involving the eyes, together with a better understanding of the pathophysiological mechanisms of dry eye disease (DED), have led to the need for a specific report about iatrogenic dry eye within the TFOS DEWS II. Topical medications can cause DED due to their allergic, toxic and immuno-inflammatory effects on the ocular surface. Preservatives, such as benzalkonium chloride, may further aggravate DED. A variety of systemic drugs can also induce DED secondary to multiple mechanisms. Moreover, the use of contact lens induces or is associated with DED. However, one of the most emblematic situations is DED caused by surgical procedures such as corneal refractive surgery as in laser-assisted in situ keratomileusis (LASIK) and keratoplasty due to mechanisms intrinsic to the procedure (i.e. corneal nerve cutting) or even by the use of postoperative topical drugs. Cataract surgery, lid surgeries, botulinum toxin application and cosmetic procedures are also considered risk factors to iatrogenic DED, which can cause patient dissatisfaction, visual disturbance and poor surgical outcomes. This report also presents future directions to address iatrogenic DED, including the need for more in-depth epidemiological studies about the risk factors, development of less toxic medications and preservatives, as well as new techniques for less invasive eye surgeries. Novel research into detection of early dry eye prior to surgeries, efforts to establish appropriate therapeutics and a greater attempt to regulate and oversee medications, preservatives and procedures should be considered.

Reshaping procedures for the surgical management of corneal ectasia

Corneal ectasia is a progressive, degenerative, and noninflammatory thinning disorder of the cornea. Recently developed corneal reshaping techniques have expanded the treatment armamentarium available to the corneal specialist by offering effective nontransplant options. This review summarizes the current evidence base for corneal collagen crosslinking, topography-guided photorefractive keratectomy, and intrastromal corneal ring segment implantation for the treatment of corneal ectasia by analyzing the data published between the years 2000 and 2014.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Intrastromal corneal ring segment implantation (keraring 355°) in patients with central keratoconus: 6-month follow-up

We evaluate the efficacy and safety of Keraring 355° intrastromal corneal ring segment (ICRS) implantation aided by PocketMaker microkeratome for the correction of keratoconus. Patients underwent ICRS insertion using mechanical dissection with PocketMaker microkeratome and completed 6 months of follow-up. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), refraction, topographic findings, safety, efficacy index, and adverse events were reported for six months postoperatively. We evaluated 15 eyes of 15 patients (12 men) with a mean age of 28.87 ± 6.94 years (range 21–49 years). At final postoperative examination, there was a statistically significant reduction in the spherical equivalent refractive error compared to preoperative measurements (−5.46 ± 1.52 to −2.01 ± 1.63 D, P < 0.001). Mean preoperative UCVA (logMAR) before implantation was 0.79 ± 0.48, and postoperative UCVA was 0.28 ± 0.15, P = 0.001. Mean preoperative BSCVA (logMAR) before implantation was 0.36 ± 0.21; at final follow-up examination BSCVA was 0.18 ± 0.9, P = 0.009. Mean K decreased from 48.33 to 43.31 D, P < 0.001. All patients were satisfied with ICRS implantation; 86.7% were moderately to very happy with the results. No intraoperative or postoperative complications were demonstrated. This preliminary study shows that ICRS (Keraring 355°) implantation is an efficient, cost-effective, and minimally invasive procedure for improving visual acuity in nipple type keratoconic corneas.

Intrastromal corneal ring segments for bilateral keratoconus in an 11-year-old boy

We present the case of an 11-year-old boy who had bilateral implantation of intrastromal corneal ring segments for progressive keratoconus and poor vision. No intraoperative or postoperative complications were seen, and 1 year postoperatively, the patient maintained good spectacle-corrected vision.

FINANCIAL DISCLOSURE

Neither author has a financial or proprietary interest in any material or method mentioned.

Topography-guided conductive keratoplasty: treatment for advanced keratoconus

PURPOSE

To evaluate the use of topography-guided conductive keratoplasty in eyes with keratoconus.

DESIGN

Interventional case series.

METHODS

We examined 21 eyes in 21 patients with advanced keratoconus. Topography-guided conductive keratoplasty was performed with intraoperative monitoring of corneal astigmatism using a surgical keratometer. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), corneal topography, manifest refraction, intraocular pressure (IOP), corneal endothelial cell counts, complications, and eventual outcomes were evaluated.

RESULTS

UCVA (logarithm of the minimal angle of resolution [logMAR]), which was 1.65 ± 0.49 preoperatively, improved to 1.04 ± 0.64 at 1 week (P < .001) and 1.12 ± 0.61 at 1 month after surgery (P < .001). BSCVA, which was 1.02 ± 0.56 preoperatively, improved to 0.76 ± 0.65 at 1 week (P = .026) and 0.76 ± 0.60 at 1 month after surgery (P = .003). Manifest refraction, which was -15.13 ± 6.66 diopters (D) before surgery, declined to -9.97 ± 6.71 D at 1 month after surgery (P = .002). Although corneal topography reverted to the preoperative pattern and UCVA and BSCVA also regressed toward preoperative values, 12 of 21 eyes were better able to tolerate and conduct normal daily activities using contact lenses. Five subjects have undergone or are considering corneal transplantation after unsatisfactory postoperative results. No serious perioperative complication was observed.

CONCLUSIONS

Topography-guided conductive keratoplasty may be effective in reshaping corneal configuration in eyes with keratoconus, without serious complications, and possibly contributed to avoiding or delaying corneal transplantation.

Combined Kerarings and Artisan/Artiflex IOLs in Keratectasia

PURPOSE:To evaluate the results of combined intracorneal ring (Keraring, Mediphacos Ltd) and anterior chamber, iris-fixated, phakic intraocular lens (pIOL) (Artisan and Artiflex, Ophtec BV) implantation in patients with ectatic corneal conditions and secondary high myopic and astigmatic refractive error. METHODS:Ten eyes of eight consecutive patients with different ectatic corneal diseases underwent sequential intracorneal Keraring and iris-fixated pIOL implantation. Two eyes with keratoconus, one eye with pellucid marginal degeneration, and one eye with iatrogenic corneal ectasia were implanted with the Artisan pIOL; six eyes with keratoconus were implanted with the Artiflex pIOL. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction spherical equivalent (MRSE), topographic findings, and complications were recorded. RESULTS:Mean UDVA improved from 0.02+/-0.10 pre-operatively to 0.11+/-0.06 after Keraring implantation and to 0.54+/-0.18 after pIOL implantation (P<.001 for all). Mean CDVA improved from 0.18+/-0.12 preoperatively to 0.39+/-0.13 after Keraring implantation and to 0.66+/-0.18 after pIOL implantation (P<.001 for all). Mean MRSE reduced from -12.50+/-6.31 D preoperatively to +/-12.08+/-5.17 D after Keraring implantation (P=.10) and to -0.10+/-0.84 D after pIOL implantation (P<.001). No intra- or postoperative complications were observed. CONCLUSIONS:Sequential intracorneal Keraring segments and Artisan/Artiflex pIOL implantation resulted in visual and refractive improvements in patients with different corneal ectatic conditions with high myopic refractive errors.

Advances in technologies for laser-assisted in situ keratomileusis (LASIK) surgery

Laser-assisted in situ keratomileusis (LASIK) has become the most widely used form of refractive surgery today. The objective of this surgical technique is to modify the anterior corneal shape by ablating tissue from the stroma by means of the excimer laser after creating a hinged corneal flap. This way, we are able to change the refractive status of the patient, providing better unaided vision. Continuous improvements in the original technique have made the surgical procedure safer, more accurate and repeatable. These progressions are due to the development of novel technologies that are the responsible for new surgical instrumentation, which makes the surgical procedure easier for the surgeon, and better excimer laser ablation algorithms, which increase the optical quality of the ablation and thus the safety of the vision correction procedure. This article aims to describe the more relevant advances in LASIK that have played an important role in the spread and popularity of this technique.

Synthetic corneal inlays

This review is based on the activities of the Vision Cooperative Research Centre (previously Cooperative Research Centre for Eye Research and Technology) Corneal Implant team from 1991 to 2007. The development of a synthetic polymer of perfluoropolyether (PFPE), meeting essential physical and biological requirements, for use as a corneal inlay is presented. Each inlay was placed in a corneal flap created with a microkeratome and monitored over a two-year period in a rabbit model. The results indicate that the PFPE implant shows excellent biocompatibility and biostability. As a result, a Phase 1 clinical trial is being conducted. Three years post-implantation, the PFPE inlays are exhibiting continued excellent biocompatibility. Corneal inlays made from PFPE are biocompatible with corneal tissue in the long term and offer a safe and biologically-acceptable alternative to other forms of refractive surgery.

Long-term follow-up of Intacs in keratoconus

PURPOSE

To evaluate long-term follow-up of Intacs microthin prescription inserts (Addition Technology, Inc, Fremont, California, USA) for the management of keratoconus.

DESIGN

A long-term (five years) retrospective, follow-up study.

METHODS

Seventeen eyes of 15 patients with keratoconus ages 24 to 52 years (mean age +/- standard deviation [SD], 34.0 +/- 10.5 years) who had completed five years of follow-up (mean follow-up +/- SD, 67.2 +/- 7.5 months; range, 58 to 78 months) were included. Two Intacs segments of 0.45-mm thickness were inserted in the cornea of each eye, aiming at embracing the keratoconus area to try to achieve maximal flattening.

RESULTS

No late postoperative complications occurred in this series of patients. At five years, the spherical equivalent error was statistically significantly reduced (pre-Intacs, mean +/- SD -5.54 +/- 5.02 diopters [D]; range, -12.50 to 3.63 D; -3.02 +/- 2.65 D; range, -8.25 to 1.88 D) (P = .01). Pre-Intacs uncorrected visual acuity (UCVA) was 20/50 or worse in all eyes (range, counting fingers to 20/50), whereas, at the last follow-up examination, 10 (59%) of 17 eyes had UCVA of 20/50 or better (range, counting fingers to 20/32). Six eyes (35%) maintained the pre-Intacs best spectacle-corrected visual acuity (BSCVA) and one eye lost 3 lines of BSCVA, whereas the rest of the 10 eyes (59%) experienced a gain of one up to 8 lines.

CONCLUSIONS

After five years, intracorneal ring segments implantation improved UCVA, BSCVA, and refraction in the majority of the keratoconus patients. There was no evidence of progressive sight-threatening complications in this study.

Ectasia after laser in situ keratomileusis

PURPOSE OF REVIEW

The potential for litigation has resulted in increased interest in ectasia after laser in situ keratomileusis. This article summarizes papers written during this past year on this subject.

RECENT FINDINGS

A panel of refractive surgery experts have summarized the current state of knowledge on this subject and provided guidelines to minimize risk. Because ectasia may occur in the absence of risk factors, there may be corneas with biomechanical factors not detectable with present technology which are at risk. Several articles point out the limitations of the Orbscan (Bausch & Lomb, Rochester, New York, USA), in particular its accuracy and reproducibility with regard to data generated from the posterior surface of the cornea. A biomechanical model of the cornea is proposed which suggests that each cornea's response to laser in situ keratomileusis is unique. Several case reports are also reviewed which provide insight into pathogenesis and potential new treatment options; these include reports on histopathology, topographic pseudokeratectasia, ectasia from transient raised intraocular pressure, poor response to laser in situ keratomileusis after incisional surgery, intracorneal rings, collagen cross-linking and conductive keratoplasty to stabilize and sphericize the cornea with ectasia.

SUMMARY

Our knowledge about ectasia is still in evolution. Insights into the biomechanics and genetics of the cornea may allow us to further reduce its occurrence.