Researchers in Brazil evaluated the impact of implantation of corneal ring segments on the quality of life of keratoconus patients using a survey developed by the U.S. National Eye Institute (NEI).

Sixty-nine eyes of 42 keratoconus patients received the implants. The average age of the participants in the study was 24.9 years.

All eyes in the study were implanted with Keraring intrastromal corneal rings segments (Mediphacos). Twenty-seven patients received the implants in both eyes and 15 had the procedure performed on one eye only.

All patients completed the NEI Refractive Error Quality of Life (NEI-RQL) questionnaire before surgery and 4.5 to 8 months after ICRS implantation.

The NEI-RQL survey contains 42 items that cover a range of issues such as clarity of vision, appearance, night vision and glare. Answers to each item are converted to a 100-point scale.

In addition to evaluating quality of life, the researchers took objective measurements of refractive error, best-corrected visual acuity (BCVA) and contrast sensitivity before surgery and 3 months after surgery.

After ICRS surgery, the researchers found significant improvements in all NEI-RQL scores and the overall survey score.

Survey items that showed the greatest improvement included:

• Clarity of vision
• Far vision
• Near vision
• Activity limitations
• Appearance

“Satisfaction with correction” had the greatest improvement, ranging from scores of 25 to 50 preoperatively to 80 to 90 after surgery.

At 3 months after surgery, best spectacle-corrected visual acuity and binocular BCVA improved significantly. There also was a significant decrease in corneal curvature values, from a mean of 50.22 diopters (D) pre-operatively to 46.27 D after the procedure. Contrast sensitivity also improved after ICRS implantation.

The study authors concluded that ICRS implantation not only improves objective measures of visual function such as visual acuity and refraction, but also has a positive impact on the subjective quality of life of patients with keratoconus.

[Ed. note: At present, Intacs corneal implants (Addition Technology, Inc.) are the only FDA-approved ICRS for use in the United States.]

SOURCE:  Evaluation of the impact of intracorneal ring segments implantation on the quality of life of patients with keratoconus using the NEI-RQL (National Eye Institute Refractive Error Quality of life) instrument. British Journal of Ophthalmology. January 2010.

Keratoconus is a progressive eye disorder characterized by thinning and bulging of the cornea into an irregular cone-shaped profile, causing blurred vision that cannot be fully corrected with eyeglasses. If left untreated, progressive keratoconus can require a corneal transplant.

In the early stages of keratoconus, vision may be adequately corrected with rigid gas permeable (GP) contact lenses, and fitting these lenses often is the first line of treatment for keratoconus.

Due to weakening of the corneal structure in keratoconus, LASIK and other corneal refractive surgery is contraindicated for anyone diagnosed with keratoconus or who shows early signs of suspect keratoconus.

In progressive keratoconus or advanced keratoconus that makes GP contact lens wear impossible, newer treatment options include implantation of intrastromal corneal ring segments (ICRS) and corneal collagen cross-linking (CXL) therapy.

In CXL, a liquid riboflavin (vitamin B2) solution is applied to the surface of the cornea and then is activated with ultraviolet light, typically for a period of 30 minutes. This noninvasive therapy has been show to successfully create stronger bonds between collagen fibers within the cornea and thereby strengthen the corneal tissue.

The researchers in this study sought to determine which sequence of these procedures works best when both ICRS implantation and CXL are employed to treat progressive keratoconus.

Patients were divided into two groups: Group 1 underwent corneal collagen cross-linking first and Group 2 underwent intrastromal corneal ring segment implantation first.

The results of the study showed that uncorrected distance visual acuity and corrected distance visual acuity improved in both groups; and myopia, astigmatism and corneal curvature decreased in both groups.

However, Group 2 (ICRS implantation followed by corneal collagen cross-linking) showed greater improvements in corrected distance visual acuity, overall myopia and astigmatism reduction and corneal curvature reduction.

The researchers concluded that ICRS implantation followed by CXL therapy is the preferred sequence for the most successful treatment of progressive myopia.

SOURCE:  Effect of treatment sequence in combined intrastromal corneal rings and corneal collage crosslinking for keratoconus. Journal of Cataract & Refractive Surgery. December 2009.

Keratoconic eyes receiving the implantable corneal rings demonstrated improved visual acuity and stable corneal flattening throughout the study’s five-year follow-up period.

What is keratoconus?

Keratoconus (KC) is a degenerative disorder of the eye characterized by a progressive bulging outward of the clear front surface of the eye into an irregular cone shape.

The disorder often causes visual impairment that cannot be corrected with eyeglasses or contact lenses. Severe cases of keratoconus may necessitate a corneal transplant to restore vision.

The exact incidence of KC is unknown, but the National Keratoconus Foundation estimates the condition affects one out of every 2,000 people in the United States.

Corneal rings for keratoconus: Study results

In the Brazilian study, 35 eyes of 28 patients were implanted with Ferrara corneal ring segments and monitored for at least five years.

(Ferrara corneal rings are similar to Intacs intrastromal ring segments produced in the United States. Developed by Brazilian ophthalmologist Paulo Ferrara, MD, Ferrara corneal rings are used throughout Europe and South America to treat keratoconus.)

Data gathered five years after surgery revealed:

• Mean uncorrected visual acuity improved from worse than 20/125 pre-operatively to better than 20/70 after corneal ring segment implantation.
• Mean best-corrected visual acuity improved from approximately 20/50 pre-operatively to approximately 20/32 after implantation of corneal rings.
• Mean minimum corneal curvature decreased from 48.99 diopters (D) pre-operatively to 44.45 D after corneal ring segment implantation.
• Mean maximum corneal curvature decreased from 54.07 D pre-operatively to 48.09 D after corneal rings were inserted.

All corneal flattening was statistically significant and remained stable throughout the study’s follow-up period of five years.

Corneal rings for keratoconus: Conclusions

The researchers concluded that implantation of intrastromal corneal ring segments in keratoconic eyes produced significant improvements in uncorrected and corrected visual acuity and decreases in corneal curvature, and that these changes appear to be stable over an extended period of at least five years.

SOURCE:  Long-term follow-up of intrastromal corneal ring segments in keratoconus. Journal of Cataract & Refractive Surgery. October 2009.