Oral l-Cysteine Supplementation Enhances the Long Term-Effect of Topical Basic Fibroblast Growth Factor (bFGF) in Reducing the Corneal Haze after Photorefractive Keratectomy in Myopic Patients

Abstract

We aimed at evaluating the long-term effects of l-cysteine oral supplementation to basic fibroblast growth factor (bFGF) eye-drops on corneal re-epithelization and transparency in myopic patients subjected to photorefractive keratectomy (PRK). Forty patients subjected to bilateral PRK for myopia were enrolled and randomly divided into two groups receiving an additional therapy together with the standard postoperative treatment consisting in local tobramycin 0.3%, dexamethasone 0.1%, diclofenac 0.1%, and 0.2% hyaluronate. Group 1 included 20 patients (11 males and 9 females; 34.09 ± 8 years of age) receiving only bFGF eye-drops (10 μg/10 μL) four times a day for 7 days starting from the day of surgery; Group 2 included 20 patients (12 males and 8 females; 37.35 ± 11.5 years of age) who were postoperatively administered with topical basic fibroblast growth factor (bFGF; 10 μg/10 μL) four times a day for 7 days plus oral l-cysteine supplementation (500 mg/capsule) once a day for 15 days, starting 7 days before PRK. Patients were followed-up for 12 months. Clinical ophthalmologic parameters were recorded for all the 80 examined eyes. The corneal transparency was evaluated in vivo by slit lamp and confocal microscopy. The data showed that: (a) the corneal haze occurred in a smaller percentage of the patients who were postoperatively administered with topical bFGF plus oral l-cysteine supplementation (Group 2) compared to patients who received only bFGF (Group 1); (b) at 6 months of follow-up, the stromal mean image brightness of the patients belonging to Group 2 was significantly lower than that of the Group 1 (p < 0.03), and, interestingly, the difference was even more evident at 12 month from the treatment (p < 0.001). Moreover, the final mean of the spherical equivalent refraction was -0.06 ± 0.2 D in Group 1 and -0.08 ± 0.3 D in Group 2, whereas the final uncorrected distance visual acuity (UDVA) was equal or superior to 20/25 in 100% of eyes in both Group 1 and 2. Post refractive patients can benefit from the administration of l-cysteine before the surgery and in association with bFGF in the early postoperative period, showing a faster corneal re-epithelization able to prevent corneal haze in the long-term recovery.

Keywords: basic fibroblast growth factor; corneal haze; corneal re-epithelialization; l-cysteine administration; photorefractive keratectomy.

Figure 1

Corneal haze incidence at 3, 6, and 12 month of follow-up as a function of its time of regression in patients who received only bFGF (bFGF Group) and in patients who were administered topical bFGF plus oral l-cysteine supplementation (bFGF + l-cys Group). * p < 0.05 bFGF + l-cys Group vs. bFGF Group at each time of follow-up.

Figure 2

Mean image brightness of the stroma (marker of altered cornea), measured with the ConfoScan 4 confocal microscope and expressed as mean ± SD scatter units (SU) in corneas of patients who received only bFGF (bFGF Group) and of patients who were administered topical bFGF plus oral l-cysteine supplementation (bFGF + l-cys Group). ○ p < 0.05 bFGF Group at 3, 6, and 12 months of follow-up vs. bFGF at 1 month of follow-up; ●● p < 0.01 and ●●● p < 0.001 bFGF + l-cys Group at 3, 6, and 12 month of follow-up vs. bFGF + l-cys Group at 1 month of follow-up; * p < 0.03 and ** p < 0.001 bFGF + l-cys Group vs. bFGF Group at each time of follow-up.

Figure 3

Representative ConfoScan 4 confocal microscope images of the stroma of 5 patients who received only bFGF (bFGF Group) and of 5 patients who were administered topical with bFGF plus oral l-cysteine supplementation (bFGF + l-cys Group). Images were taken at 6 months of follow-up. Yellow arrows indicate the light scattering regions of cornea.