Utilization of refractive surgery technology in keratoconus and corneal transplants

Toric implantable collamer lens for high myopic astigmatism in keratoconic patients after six months

BACKGROUND

The aim was to evaluate the safety, efficacy, stability and predictability of posterior chamber collagen copolymer phakic intraocular lens (pIOL) implantation to correct myopia and myopic astigmatism associated with keratoconus.

METHODS

The unaided vision and visual acuity, refraction and adverse events were measured in 22 keratoconic eyes of 14 patients after using an implantable collamer lens (ICL) (STAAR Surgical Inc.) to correct refractive error. The outcome was evaluated over six months.

RESULTS

The mean pre-operative spherical equivalent (SE) and cylinder changed from -4.98 ± 2.63 DS and -2.77 ± 0.99 DC to -0.33 ± 0.51 DS and -1.23 ± 0.65 DC, respectively at the end of six months. Before the surgery the mean Snellen decimal visual acuity was 0.63 ± 0.20. The mean unaided vision and visual acuity changed to 0.76 ± 0.23 and 0.85 ± 0.21, respectively at the end of six months. The mean safety and efficacy indices were 1.40 ± 0.32 and 1.24 ± 0.34, respectively. No eye lost a line of visual acuity and 17 eyes (77.3 per cent) gained one or more lines. Fifteen eyes (68.2 per cent) were within 0.50 D and 20 (90.9 per cent) were within 1.00 D of the desired spherical equivalent refraction. There was a change in manifest refraction of 0.09 ± 0.21 (ranging from -0.25 to +0.75) from one week to six months after the surgery.

CONCLUSION

The clinical outcomes of the current study demonstrate the safety, efficacy and predictability of toric implantable collamer lens in the correction of myopia and myopic astigmatism associated with keratoconus. The patients' refractions achieved early stability and remained stable during the course of the study.

Intrastromal corneal ring segments: effect of relationship between alignment and topographic keratometric meridians

PURPOSE

To determine whether the keratometric and refractive surgical effects of paired intrastromal corneal ring segments (ICRS) depend on their alignment relative to steep and flat topographic meridians.

SETTING

St. Paul's Eye Unit, Royal Liverpool University Hospital, Liverpool, United Kingdom.

DESIGN

Comparative case series.

METHODS

Keratoconic patients who had two 0.3 mm Intacs ICRS inserted were retrospectively grouped depending on alignment of segments within 30 degrees either side of the steep (meridional group) or the flat (perpendicular group) topographic meridians, respectively, with the rest in the oblique group. Principal outcome measures were changes in visual acuity, refractive surgical effect, and keratometric surgical effect 4 months postoperatively.

RESULTS

Forty eyes of 40 patients were included. There was a significant reduction in keratometric power (flattening) (P<.01) but not in refractive error in all 3 groups. The reduction in keratometric astigmatism was significantly greater in the perpendicular group (-2.67 diopters [D]) than in the meridional group (-0.65 D) (P=.03), with the oblique group (-0.9 D) in between (P=.12). The principal reduction was flattening orthogonal to the incision site, with relative steepening in the axis of ICRS alignment. In all groups, variations in the refractive surgical effect and keratometric surgical effect were very high.

CONCLUSIONS

Placement of two 0.3 mm ICRS had a variable effect with limited predictability. There was predominant flattening of the cornea orthogonal to the axis of ICRS alignment. Irrespective of the location of preoperative steep and flat keratometric meridians, the maximum reduction in astigmatism occurred when the incision and the segments were placed along the flat topographic meridian.

FINANCIAL DISCLOSURE

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

Keratoconus: overview and update on treatment

Keratoconus is a non-inflammatory, progressive thinning process of the cornea. It is a relatively common disorder of unknown etiology that can involve each layer of the cornea and often leads to high myopia and astigmatism. Computer- assisted corneal topography devices are valuable diagnostic tools for the diagnosis of subclinical keratoconus and for tracking the progression of the disease. The traditional conservative management of keratoconus begins with spectacle correction and contact lenses. Several newer, more invasive, treatments are currently available, especially for contact lens-intolerant patients. Intrastromal corneal ring segments can be used to reshape the abnormal cornea to improve the topographic abnormalities and visual acuity. Phakic intraocular lenses such as iris-fixated, angle-supported, posterior chamber implantable collamer and toric lenses are additional valuable options for the correction of refractive error. Corneal cross-linking is a relatively new method of stiffening the cornea to halt the progression of the disease. The future management of keratoconus will most likely incorporate multiple treatment modalities, both simultaneous and sequential, for the prevention and treatment of this disease.

[New therapeutic approach of keratoconus with intracorneal ring segments aided by femtosecond laser (Tecnolas Perfect Vision): indications, operating technique and results]

OBJECTIVE

To assess the results of intracorneal ring segment implantation assisted by the Tecnolas Perfect Vision(®) femtosecond laser (Heidelberg, Germany).

SETTINGS

Retrospective observational study.

METHODS

The patients were operated on with the Tecnolas Perfect Vision(®) femtosecond laser. The following parameters were evaluated before and after surgery: uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), corneal topography, wavefront analysis, and central corneal thickness. The Wilcoxon test was used for statistical analysis.

RESULTS

Seventeen eyes of 15 patients were included. The mean follow-up was 6.9±0.71 months. Significant improvement of UCVA and BCVA was observed in 82.35% (P=0.027) and 94.12% (P=0.003) of the eyes, respectively. The subjective refraction showed a significant decrease of the sphere from -10.29±5.54 to -6.5±5.03D (P=0.002). The subjective cylinder significantly decreased from 5.43±3.20 to 3.69±2.30D (P=0.026). The SAI also decreased significantly (P=0.011).

CONCLUSION

Femtosecond-assisted intracorneal ring segment implantation is an effective treatment for corneal ectasia. Further studies are needed to improve surgical parameters and outcomes.

Intacs for Keratoconus and Post-LASIK Ectasia

PURPOSE

To evaluate the efficacy of intracorneal ring segments to treat keratoconus and post-laser in situ keratomileusis (LASIK) keratectasia implanted by using either mechanical dissection or a femtosecond laser.

METHODS

Thirty-three eyes of 29 patients had intracorneal ring segments implanted by using mechanical dissection (17 eyes) or a femtosecond laser (16 eyes). Mean follow-up was 10.3 months. Parameters assessed before and after surgery included uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refractive spherical equivalent (MRSE), refractive cylinder (RC), best contact lens-corrected visual acuity (BCLVA), and contact lens tolerance.

RESULTS

Statistically significant changes occurred for all parameters when we analyzed all 33 eyes as 1 group. Mean UCVA LogMar values improved from 1.0 +/- 0.3 (20/200) to 0.6 +/- 0.4 (20/80) (P < 0.0005). Mean BSCVA changed from 0.3 +/- 0.2 (20/40) to 0.2 +/- 0.2 (20/30) (10%; P < 0.05), and MRSE from -9 +/- 4 to -7 +/- 4 D (P < 0.05; 20%). There was a decrease of 0.5 D or more of RC in 62% of eyes. BCLVA improved from 0.2 +/- 0.2 (20/30) to 0.1 +/- 0.1 (20/25) after surgery (P < 0.02). Contact lens tolerance improved in 81% of eyes. There was no statistically significant difference in outcomes between mechanical dissection and femtosecond laser-assisted techniques. However, although statistical power was adequate to detect changes in clinical parameters as a result of surgery, it was not sufficient to conclusively show such differences between surgical techniques.

CONCLUSIONS

For mild to moderate cases of keratoconus and post-LASIK keratectasia, the use of a femtosecond laser for Intacs channel creation seems as effective as mechanical dissection. Future studies are warranted to further evaluate channel creation by a femtosecond laser.

Intacs for the correction of keratoconus: Two-year follow-up

PURPOSE

To evaluate the long-term safety and efficacy of Intacs segments (Addition Technology, Inc.) for the treatment of keratoconus in terms of intraoperative and postoperative complications, visual outcome, restoration of contact lens tolerance, and inhibition of disease progression.

SETTING

Service d'Ophtalmologie, CHU Pellegrin, Bordeaux, France.

METHODS

This prospective, 2-year follow-up study comprised 100 keratoconic eyes with clear central corneas and contact lens intolerance. The best spectacle-corrected visual acuity (BSCVA), uncorrected visual acuity (UCVA), refractive error, keratometry, pachymetry, and slitlamp examination were assessed preoperatively and 1 and 2 years after Intacs implantation.

RESULTS

At 2 years, the UCVA and BCVA improved in 80.5% and 68.3% of eyes, respectively (P<.001). The proportion of eyes with a BCVA >or=0.5 (20/40) increased from 22.0% at baseline to 51.2% and 53.7% at 1 year and 2 years, respectively (P<.001). The manifest refraction spherical equivalent improved from a mean of -6.93 diopters (D) +/- 3.91 (SD) preoperatively to -4.01 +/- 3.16 D at 1 year and -3.80 +/- 2.73 D at 2 years (P<.001). The mean keratometry readings decreased from 50.1 +/- 5.6 D preoperatively to 46.4 +/- 5.3 D at 1 year and 46.8 +/- 4.9 D at 2 years (P<.001). Contact lens tolerance was restored in over 80% of cases. Postoperative slitlamp observations revealed no clinically significant issues. The segments were removed from 4 eyes without complications or sequelae.

CONCLUSION

Intacs implantation was a safe and efficacious treatment for keratoconus. Significant and sustained improvements in objective visual outcomes were achieved in most cases, with restoration of contact lens tolerance.

European clinical evaluation: Use of Intacs for the treatment of keratoconus

PURPOSE

To evaluate the safety and efficacy of Intacs inserts in keratoconic eyes to alter corneal shape and refractive power and stabilize the progression of corneal ectasia.

SETTING

Service d'Ophtalmologie, Bordeaux, France.

METHODS

In this prospective study, 57 eyes with clear central corneas that were diagnosed with keratoconus and contact lens intolerant were followed for up to 1 year. The primary objectives were to assess the safety of Intacs and the visual outcomes by measuring uncorrected visual acuity (UCVA), best corrected visual acuity, manifest refraction spherical equivalent, keratometry, intraocular pressure (IOP), pachymetry, and patient satisfaction. The stability of the refraction, keratometry, and visual acuity measurements was also assessed.

RESULTS

At the 6-month examination, 78% of patients showed improvement of 2 lines or more in UCVA (P<.001). Best corrected visual acuity of 20/40 or better improved from 53% of patients preoperatively to 74% of patients (P< or =.033). Manifest refraction spherical equivalent improved to 3.1 +/- 2.5 diopters (D) (P<.001) compared with the preoperative examination. Keratometry decreased a mean of -4.3 +/- 2.8 D from the preoperative readings (P< or =.002). These changes appeared to be stable over time. At 6 months, there were no adverse events, no clinically significant increase in IOP, and no decrease in central corneal thickness. In 7 of 57 eyes (12%), the Intacs were removed due to dissatisfaction with visual symptoms. There were no adverse effects or complications associated with the Intacs removal.

CONCLUSIONS

Intacs were safe and effective for treating keratoconus. All patients demonstrated improved objective visual outcomes; functional vision was restored in most patients. Intacs were removed without permanent sequelae.

Le kératocône : options chirurgicales actuelles

The treatment of keratoconus is in part dependant on the severity of the disease process. When contact lenses fail because of patient intolerance or insufficient acuity to meet the patient's needs, penetrating keratoplasty is the usual surgical modality considered for satisfactory visual rehabilitation. Keratoconus is considered to be a contraindication for incisional refractive surgery such as radial keratotomies or LASIK because of the corneal instability conferred by these procedures. When the cornea is transparent, INTACS implantation is a refractive modality that may improve visual function and in some instances prevent the need for corneal transplantation in select patients with keratoconus.