Adhesion of Acanthamoeba on Scleral Contact Lenses According to Lens Shape

Abstract

Purpose: To investigate the adhesion of Acanthamoeba to scleral contact lens (ScCL) surface according to lens shape.

Methods: Two strains of A. polyphaga (CDC:V062 and ATCC 30461) and one clinical Acanthamoeba isolate, were inoculated onto five contact lens (CL): one first-generation silicone hydrogel (SHCL; lotrafilcon B; adhesion control) containing plasma surface treatment; two ScCL (fluorosilicone acrylate) one containing surface treatment composed of plasma and the other containing plasma with Hydra-PEG, and two CL designed with a flat shape having the same material and surface treatments of the ScCL. Trophozoites that adhered to the lens's surfaces were counted by inverted optical light microscopy. Possible alterations of the lens surface that could predispose amoeba adhesion and Acanthamoeba attached to these lens surfaces were evaluated by scanning electron microscopy (SEM).

Results: All strains revealed greater adhesion to the ScCL when compared with the flat lenses (P < 0.001). The clinical isolate and the ATCC 30461 had a higher adhesion (P < 0.001) when compared with the CDC:V062. A rough texture was observed on the surface of the lenses that have been examined by SEM. Also, SEM revealed that the isolates had a rounded appearance on the surface of the ScCL in contrast with an elongated appearance on the surface of the silicone hydrogel.

Conclusions: The findings revealed that the curved shape of the ScCL favors amoeba adhesion.

Figure 1.

Inverted optical light microscopic images of adherent Acanthamoeba trophozoites to different surfaces of CL in an experiment carried out in triplicate. Initial inoculum of 1 × 10⁵ trophozoites/CL. CDC:V062 and ATCC 30461, reference strains of A. polyphaga; clinical isolate, isolated from a patient with AK; Group 1, SHCL; Group 2.1, SsCL with Plasma surface treatment; Group 2.2, Flat lenses with Plasma surface treatment; Group 3.1, SsCL with Plasma and Hydra-PEG surface treatment; Group 3.2 Flat lenses with Plasma and Hydra-PEG surface treatment (magnification × 200, Advanced Research Center in Acanthamoeba; CEPA-UNIFESP).

Figure 2.

SEM image of CL surface: (A; Group 1) SHCL, (B; Group 2.1) SsCL (surface treatment with plasma), (C; Group 2.2) Flat lens (surface treatment with plasma), (D; Group 3.1) SsCL (surface treatment with plasma and Hydra-PEG), (E; Group 3.2) Flat lens (surface treatment with plasma and Hydra-PEG) (magnification ×20,000, CEME-UNIFESP).

Figure 3.

SEM image of the clinical isolate Acanthamoeba spp. trophozoites adhered to the SHCL and ScCL surface: (A; Group 1) amoeboid trophozoite (clinical isolate) adhered to the SHCL (Group 1), (B; Group 2.1) rounded trophozoite (clinical isolate) adhered to the ScCL (surface treatment with the plasma: Group 2.1), (C; Group 3.1) rounded trophozoite (clinical isolate) adhered to the ScCL (surface treatment with plasma and Hydra-PEG: Group 3.1). The red arrows indicate the site of the clinical isolate adhesion by the acanthopodia to the lens surface (magnification ×15,000, CEME-UNIFESP).