Evaluation of preloaded intraocular lens injection systems: Ex vivo study.

PURPOSE: To compare preloaded intraocular lens (IOL) injection systems. SETTING: Sussex Eye Hospital, Brighton, United Kingdom. DESIGN: Experimental study. METHODS: In 30 porcine eyes, 5 preloaded +22.0 diopters IOLs were implanted from each of the following preloaded IOL systems: Ultrasert (U), iTec (iT), Eyecee (E), iSert (iS), Rayone (R), and CT Lucia (CT). External and internal wound size was measured. Nozzle damage was assessed using digital photography. The ease of opening the pack, ophthalmic viscosurgical device (OVD) injection, advancing into the nozzle, nozzle insertion, and IOL delivery was scored on a 4-point Likert scale, and the time was recorded. RESULTS: The iT, E, and iS injectors with acute angled bevels and shorter nozzle tips showed more damage after implantation. The fastest with regard to opening the pack and nozzle insertion was U, OVD injection and advancing into the nozzle was E, and IOL delivery was R. The maximum postimplantation wound stretch was 20% with the CT (mean 2.64 mm ± 0.1 [SD]), and the least was 11.8% with the iT (mean 2.46 ± 0.1 mm). Both the U and R scored 4 (very easy) for all parameters measured; the E, iS, iT, and CT scored 4 or less in some parameters with decreasing scores, respectively. CONCLUSIONS: The models, design, and injection systems varied with each brand; however, the longer and more parallel the nozzle and less acute the angle of the bevel tip, the lesser the stress with less nozzle damage after surgery. All preloaded systems varied in the ease-of-use and time for surgical steps, and all lead to postoperative wound stretch.

Corneal Cross-Linking: An Example of Photoinduced Polymerization as a Treatment Modality in Keratoconus.

The cornea is one of the principal refractive elements in the human eye and plays a crucial role in the process of vision. Keratoconus is the most common corneal dystrophy, found mostly among young adults. It is characterized by a reduced number of collagen cross-links in the corneal stroma, resulting in reduced biomechanical stability and an abnormal shape of the cornea. These changes lead to progressive myopia, corneal thinning, central scarring and irregular astigmatism, causing severely impaired vision. Hard contact lenses, photorefractive keratectomy or intracorneal rings are the most common treatment options for refractive error caused by keratoconus. However, these techniques do not treat the underlying cause of the corneal ectasia and therefore are not able to stop the progression of the disease. Riboflavin photoinduced polymerization of corneal collagen, also known as corneal cross-linking (CXL), has been introduced as the first therapy which, by stabilizing the structure of the cornea, prevents the progression of keratoconus. It stiffens the cornea using the photo-sensitizer riboflavin in combination with ultraviolet irradiation. This is a current review of the CXL procedure as a therapy for keratoconus, which relies on photoinduced polymerization of human tissue. We have focused on its biomechanical and physiological influences on the human cornea and have reviewed the previous and current biochemical theories behind cross-linking reactions in the cornea.