Comparison of Photochemical Crosslinking Versus Sutures for Bonding Conjunctival Grafts.

BACKGROUND AND OBJECTIVES: To explore whether Rose Bengal-induced photochemical crosslinking (RB-PCL) can be a replacement for sutures in conjunctival autograft bonding, we compared the safety, operating time, postoperative ocular signs, and inflammatory responses of RB-PCL versus nylon suturing for sealing conjunctival autografts in rabbits. STUDY DESIGN/MATERIALS AND METHODS: Thirty-six New Zealand White rabbits underwent limbal conjunctival autografting using either sutures or RB-PCL to attach conjunctival autografts to the bare sclera. Animals were randomized to one of two groups (18 per group): the suture group or RB-PCL group. Photochemical crosslinking with a wavelength of 532 nm green light with an illumination intensity of 0.6 W/cm2 for 250 seconds (150 J/cm2 ) or suturing was performed followed by light examination at 3, 7, 28 days after surgery to evaluate the healing condition. Rabbits in each group were euthanized on day 3 (n = 6), 7 (n = 6), or 28 (n = 6) postoperatively, and the graft tissues from the surgical site were processed to evaluate inflammatory response by assessing protein levels of tumor necrosis factor α (TNF-α), and interleukin 6 (IL-6) as well as histological examination. Cell viability was evaluated by counting both total and dead cells on hematoxylin and eosin (H&E) stained tissue samples from both groups at 3 and 7 days after surgery. The surgery procedure time was recorded and the graft surface temperatures were measured before and after illumination. RESULTS: Photochemical crosslinking effectively secured the limbal conjunctival autograft over an ocular conjunctival defect with no significant difference from the suture group. The time required for this light activated bonding method was ~550 seconds in comparison with the suture method of half hour. The differences of measured temperature on the graft surface before and after RB-PCL treatment were 2.98 ± 0.11°C. The induction of IL-6 and TNF-α protein was remarkably reduced in the RB-PCL group compared with the suture group at 3 and 7 days after surgery. Histology revealed less infiltrated neutrophils were observed in the RB-PCL group than in the suture group at 3 and 7 days postoperatively. Furthermore, the RB-PCL group showed a better healing process with less eye discharge and mild conjunctival congestion. No significant difference in percent dead cells was observed between RB-PCL and suture groups at 3 and 7 days after surgery. CONCLUSIONS: RB-PCL is a promising alternative for bonding the conjunctival autograft with shorter operation time, less inflammation and better healing outcomes compared to conventional suture. Thermal damage and phototoxicity were not observed using the RB-PCL method in bonding conjunctival grafts. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Subacute effects of rose Bengal/Green light cross linking on rabbit thin corneal stability and safety.

BACKGROUND AND PURPOSE: The purpose of this study was to investigate the subacute effects of Rose Bengal (RB) and 532 nm green light-induced photochemical crosslinking (RB-PCL) on rabbit thin corneal stability and safety in vivo. MATERIALS AND METHODS: Rabbit thin corneal models with 250 µm thickness were created by photorefractive keratectomy surgery. Photochemical crosslinking with green light (wavelength 532 nm) at an illumination intensity of 0.4 W/cm2 for 250 s (100 J/cm2 ) was performed, followed by antibiotic treatment and slit lamp monitoring for four weeks. At the end of week four, corneal biomechanical stiffness, biochemical resistance to collagenase digestion, and corneal cellular morphology were assessed. The penetration depth of RB into the corneal stromal was measured by confocal microscopy. RESULTS: At the end of week 4, RB-PCL had increased corneal tensile strength by an average 2.5-fold and had extended the corneal collagenase digestion time from 10.17 ± 2.93 to 15.83 ± 2.64 days. RB penetrated approximately 90 µm into the corneal stroma. RB-PCL did not alter the corneal endothelial and stromal morphology at the cellular or subcellular levels, according to electron microscopic examination. CONCLUSIONS: RB and 532 nm green light irradiation effectively induced crosslinking in rabbit thin cornea, by increasing both the biomechanical stiffness and the biochemical resistance without evidence of morphological damage to the corneal endothelium or stroma. This study demonstrated the efficacy of RB-PCL in strengthening thin cornea at four weeks after the treatment, providing a potential and possibly better option for treating corneal ectasia disorders in cases where corneal thickness is less than 400 µm. Lasers Surg. Med. 50:324-332, 2018. © 2017 Wiley Periodicals, Inc.

Photochemical activation increases the porcine corneal stiffness and resistance to collagenase digestion.

In this study, we explore the effect of photochemical activation induced corneal cross-linking, utilizing Rose Bengal (RB) and 532 nm green light irradiation (RB-PCL), on porcine corneal biomechanical rigidity and the biochemical resistance against collagenase digestion. A protocol with a wavelength of 532 nm and illumination intensity of 0.4W/cm(2) for 250 s to deliver a dose of 100 J/cm(2) was chosen. Using confocal microscopy, we demonstrated that the diffusion depth of RB into porcine cornea was approximately 150 µm and mostly localized in anterior stroma 25 min followed by RB application. After photochemical cross-linking, an increase in tensile strength (by average 200%) and Young's modulus (by average 200%) in porcine corneas was observed. The corneal buttons treated by RB-PCL showed doubling of collagenase digestion time from 10.8 ± 3.1 days in the blank group to 19.7 ± 6.2 days in the RB-PCL group, indicating increased resistance to enzymatic digestion. In conclusion, Collagen cross-linking by RB-PCL increased both the biomechanical stiffness and the biochemical resistance against collagenase digestion in porcine corneas, therefore to allow stabilizing and solidifier the cornea. The advantages and disadvantages of RB-PCL versus UVA/riboflavin cross-linking technique (UV-CXL) are fully explored. Due to the nature of minimal penetration of RB into corneal stroma, the RB-PCL method could potentially be used in patients with corneal thickness less than 400 µm where UV-CXL is limited.

[The clinical efficacy and safety study of Esculin and Digitalis glycosides Eye Drops in treating ametropic asthenopia].

OBJECTIVE: To study the clinical efficacy and safety of the Esculin and Digitalis glycosides Eye Drops used in the patients of ametropic asthenopia. METHODS: Multicenter clinical trial. Asthenopia patients were chosen from eleven hospitals cross China from July, 2008 to January, 2009. The experiment was conducted asthenopia patients who used the Esculin and Digitalis glycosides Eye Drops for 4 weeks continuously. Symptoms of asthenopia, UCVA (uncorrected vision acuity), refraction, amplitude of accommodation, accommodative lag, accommodative sensitivity and positive/negative relative accommodation were measured at different time points, such as treated before, 1 week and 4 week in treated after. RESULTS: After the 4-week's use of Esculin and Digitalis glycosides Eye Drops, each subjective symptom of the patients was decreased significantly (F=353.30, P<0.05). In addition, most of the objective exams of accommodation ability were significantly improved, such as UCVA (left eye: F=23.39, P<0.05; right eye: F=15.62, P<0.05), refraction (left eye: F=10.34, P<0.05; right eye: F=17.13, P<0.05), amplitude of accommodation (left eye: F=14.46, P<0.05; right eye: F=8.29, P<0.05; eyes: F=13.86, P<0.05), accommodative lag (F=14.89, P<0.05) and accommodative sensitivity (left eye: F=62.67, P<0.05; right eye: F=68.77, P<0.05; eyes: F=82.74, P<0.05). And no patient appeared any adverse reaction in whole experiment. CONCLUSIONS: Esculin and Digitalis glycosides Eye Drops is effective and safety for use in the patients of ametropia asthenopia.

Photochemical Cross-Linking for Penetrating Corneal Wound Closure in Enucleated Porcine Eyes.

PURPOSE: To compare the efficacy of photochemical-induced tissue cross-linking (PCL), utilizing Rose Bengal (RB) and 532 nm green light irradiation (RB-PCL), with standard sutures for closure of penetrating corneal incision in porcine cadaver eyes. METHODS: A full-thickness penetrating incision, 3 mm in length parallel to the limbus and perpendicular to the corneal surface, was made in the enucleated porcine cornea. Photochemical cross-linking was performed with tropical RB application and irradiation of 532 nm green light (0.6 W/cm2) for 200, 250, and 300 seconds at laser fluences of 120, 150, and 180 J/cm2, respectively, which was compared with the standard 10-0 nylon suture group. Following treatment, intraocular pressure to the point where wound leakage occurred (IOPL) was measured. Corneal central thickness and surface temperature before and after PCL treatment were recorded. Optical coherence tomography (OCT) and scanning electron microscopy (SEM) were utilized to evaluate wound closure. RESULTS: The mean corneal central thickness was increased from 812.0 ± 47.0 to 838.0 ± 45.6 µm after the incision as a result of cornea aqueous humor infiltration. RB penetrated approximately 140 µm into the porcine corneal stroma. The mean IOPL for untreated blank group after incision was 4.27 ± 0.36 mmHg. Increased laser fluences produced increased IOPL of 27.02 ± 3.01 (PCL120), 31.60 ± 3.67 (PCL150) and 36.73 ± 3.25 mmHg (PCL180), which were statistically different from the control intact group. The mean IOPL in the sutured cornea was 57.30 ± 4.59 mmHg. The average surface temperature difference before and after PCL treatment was 2.03 ± 0.45-2.47 ± 0.79°C. OCT demonstrated not only complete but also improved closure in comparison with disorganized collagen fibers after conventional suturing, which is further confirmed by SEM. CONCLUSIONS: Complete and clinically relevant seal of full-thickness porcine corneal incision was achieved using PCL method ex vivo, which provides potential application of this technique in ocular wound closure.