title: Evaluation of pigment location in tinted soft contact lenses.
abstract: OBJECTIVE
  The purpose of this study was to investigate efficient methods to evaluate the pigment layer location of tinted soft contact lenses and to assess various lens products on the market using those methods.
  
  
  METHODS
  Two types of tinted soft contact lenses with known pigment location embedded or back surface were manufactured and examined. Light microscopy (LM), focused ion beam milling and scanning electron microscopy (FIB-SEM), and Fourier-domain optical coherence tomography (FD-OCT) were used to examine the pigment layer. Lens surface roughness was also measured using atomic force microscopy. In the second part of the experiment, pigment location and surface roughness of a clear lens (Lens A) and eight commercially-available tinted soft contact lenses (Lens B-I) were evaluated using FIB-SEM and FD-OCT.
  
  
  RESULTS
  Pigment location could be reliably determined with FIB-SEM and FD-OCT. With LM, 40% of the lens sections were broken or deformed during slide preparation. The pigment particles in Lens B were buried below the front surface and there were no significant differences of roughness between the front and back surfaces. However, all tinted lenses with surface pigment had significant difference of roughness between front and back surfaces at the pigmented area.
  
  
  CONCLUSIONS
  The FIB-SEM and FD-OCT could reliably locate the pigment layer of tinted soft contact lenses. In addition, lens surface roughness was influenced by pigment layer location.
authors: The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, South Korea; Department of Ophthalmology and Inha Vision Science Laboratory, Inha University School of Medicine, Incheon, South Korea.
authors: Ji Won
authors: JW
authors: Jung
authors: The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, South Korea.
authors: Sun Hyup
authors: SH
authors: Han
authors: The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, South Korea.
authors: Sang Ah
authors: SA
authors: Kim
authors: The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, South Korea; Corneal Dystrophy Research Institute, Severance Biomedical Science Institute, and Brain Korea 21 Plus Project for Medical Science, Yonsei University College of Medicine, Seoul, South Korea.
authors: Eung Kweon
authors: EK
authors: Kim
authors: The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, South Korea.
authors: Kyoung Yul
authors: KY
authors: Seo
authors: The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, South Korea. Electronic address: tikim@yuhs.ac.
authors: Tae-Im
authors: TI
authors: Kim
mesh_terms: D065966:Absorption, Physicochemical; D003124:Colorimetry / Q000379:methods; D004396:Coloring Agents / Q000032:analysis* / Q000737:chemistry*; D003263:Contact Lenses, Hydrophilic / Q000145:classification*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008422:Materials Testing / Q000379:methods; D008853:Microscopy / Q000379:methods; D013499:Surface Properties; D041623:Tomography, Optical Coherence / Q000379:methods
chemical_list: D004396:Coloring Agents
keywords: Atomic force microscopy; Focused ion beam scanning electron microscopy; Pigment location; Surface roughness; Tinted soft contact lenses