Correction Of Crab Claw Topographic Pattern Using Two 90 Degree Arc Intracorneal Ring Segments

To assess the visual and refractive out come of using two 90 degree arc intracorneal ring segments (ICRS) in cases with crab claw topographic pattern which indicate the patients have corneal ectasia which may be pellucid marginal degeneration (PMD) or pellucid like keratoconus (PLK)

the memorial institute for ophthalmic research 

Prospective interventional study of (17) eyes of 9 patients with crab claw topographic pattern either PLK or PMD that need ICRs .  Inclusion Criteria: patients with crab claw topographic pattern, no previous corneal surgery, high cylinder that need ICRS for correction. Exclusion Criteria: Patients with central corneal opacity, very thin cornea less than 400um and previous ocular surgery were excluded.

Preoperative evaluation included detailed ocular history, full ophthalmic examination including: uncorrected VA(UCVA), manifest refraction, best spectacle-corrected VA (BSCVA) and Pentacam.

The femtosecond laser was used in all cases for tunnel and incisions creation. Implantation of the ICRS was carried out under full aseptic technique.

The study evaluated 17 eyes of 9 patients (7 males and 2 females) with a mean age of 24.41 ± 7.11 years and ranged from 22 to 29 years. The mean duration of follow-up was 12 months and ranged from 6 to 18 months.

Regarding visual outcome, the mean UCVA improved significantly from (0.12 +/- 0.09) to (0.86 +/-0.16) postoperatively (P < 0.001). The UCVA improved in all eyes (100%). The mean BCVA in LogMAR improved significantly from (0.31 +/- 0.18) to (0.91 +/- 0.11) postoperatively (P < 0.001). The mean cylinder was (-8.00 +/- 1.30) preoperatively that improved to (-1.50 +/- 1.00) at the end of the follow-up (P < 0.001) while the mean sphere improved non-significantly from (+2.00 +/- 1.00) to (+2.50 +/- 1.00) postoperatively.  

We concluded that two 90-degree arc ICRS implantation is a safe and efficient surgical option in the management of patients with crab claw topographic pattern which was either PMD or PLK with a good visual and refractive outcomes.