Comparison of In-the-bag Stability Between Single-piece and Three-piece Intraocular Lens
Condition: Cataract
MeSH terms: Cataract
Study type: Interventional

Summary: 
      Rapid advances of cataract surgery techniques and intraocular lens (IOL) technology have
      enabled the transition of cataract surgery from blindness relief to refractive correction. An
      ideal IOL is the critical component to achieve the refractive target of cataract surgery.
      Biocompatibility, rate of posterior capsule opacification (PCO) and visual quality have all
      been suggested as the critical factors of an ideal IOL and widely investigated. Recently,
      stability of IOL position has also been suggested as one of those critical factors due to its
      close correlation with postoperative visual function. Data suggests that IOL forward movement
      of 0.29 mm along the visual axis is associated with -0.4D myopic shift. Wang and colleagues
      recently reported that 0.5mm decentration of an aspheric IOL could eliminate its
      aberration-correcting effect. Poor stability could even lead to IOL exchange, an additional
      surgery that put both surgeons and patients in pain.

      As the supporting element of an IOL, the haptics are crucial to keep the IOL in place.
      Various haptic designs are being compared in terms of position stability of IOLs. Haptic
      designs of single-piece versus 3-piece are often compared because they are currently the most
      commonly used types. Single-piece IOLs have soft and broader haptics which are made of the
      same material as the optic, usually hydrophobic or hydrophilic acrylic, whereas 3-piece IOLs
      have rigid haptics which are made of poly methyl methacrylate (PMMA). Clinical studies
      comparing these haptic designs have yielded controversial results regarding their position
      stability in the capsular bag, which is the most recommended site for IOL fixation in an
      uneventful cataract surgery.
    

Detailed description: 
      Rapid advances of cataract surgery techniques and intraocular lens (IOL) technology have
      enabled the transition of cataract surgery from blindness relief to refractive correction. An
      ideal IOL is the critical component to achieve the refractive target of cataract surgery.
      Biocompatibility, rate of posterior capsule opacification (PCO) and visual quality have all
      been suggested as the critical factors of an ideal IOL and widely investigated. Recently,
      stability of IOL position has also been suggested as one of those critical factors due to its
      close correlation with postoperative visual function. Data suggests that IOL forward movement
      of 0.29 mm along the visual axis is associated with -0.4D myopic shift. Wang and colleagues
      recently reported that 0.5mm decentration of an aspheric IOL could eliminate its
      aberration-correcting effect. Poor stability could even lead to IOL exchange, an additional
      surgery that put both surgeons and patients in pain.

      As the supporting element of an IOL, the haptics are crucial to keep the IOL in place.
      Various haptic designs are being compared in terms of position stability of IOLs. Haptic
      designs of single-piece versus 3-piece are often compared because they are currently the most
      commonly used types. Single-piece IOLs have soft and broader haptics which are made of the
      same material as the optic, usually hydrophobic or hydrophilic acrylic, whereas 3-piece IOLs
      have rigid haptics which are made of poly methyl methacrylate (PMMA). Clinical studies
      comparing these haptic designs have yielded controversial results regarding their position
      stability in the capsular bag, which is the most recommended site for IOL fixation in an
      uneventful cataract surgery.

      Most previous studies measure the IOL position based on Purkinje reflections. The measurement
      is time-consuming and patients are reluctant to cooperate during image acquisition. Purkinje
      measurement does not detect anterior chamber depth (ACD) and as such cannot reveal the IOL
      position along the axis. Clinical Scheimpflug systems based on rotating Scheimpflug imaging,
      on the other hand, is able to acquire sufficient 3-dimensioinal data points within a
      reasonably short period, usually seconds. It was shown that these systems are one of the best
      methods to estimate IOL position. To better compare the intracapsular stability between
      single-piece and 3-piece IOLs, the investigators measured IOL positions with rotating
      Scheimpflug imaging systems and tested the visual quality of patients implanted with these
      IOLs.
    

Intervention name(s): Phacomulsification lens removal cataract surgery with single-piece Intraocular lens(IOL) implantation; Phacomulsification lens removal cataract surgery with three-piece Intraocular lens(IOL) implantation; Subconjunctival dexamethasone; Viscoelastic materials; proparacaine
Intervention type(s): Procedure; Procedure; Drug; Device; Drug
Intervention description(s): The phacoemulsification lens removal cataract surgery is performed with single-piece IOL.During Phacoemulsification.; The phacoemulsification lens removal cataract surgery is performed with three-piece IOL.During Phacoemulsification.; All patients received subconjunctival dexamethasone (2 mg) during surgery. Topical anesthesia, consisting of a single drop of 0.5% proparacaine (Alcaine, Alcon Laboratories), was administered three times at intervals of 5 minutes prior to surgery; viscoelastic materials are used to protect corneal endothelial cells; 0.5% proparacaine (Alcaine, Alcon Laboratories)
Intervention MeSH terms: Dexamethasone; Proxymetacaine
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Treatment
Keywords: Intraocular lens