Rotational Stability of the Acrysof, Tecnis and Envista Intraocular Lenses
Condition: Cataract; Astigmatism
MeSH terms: Cataract; Astigmatism
Study type: Interventional

Summary: 
      Brief Summary:

      Age-related cataract is the main cause of impaired vision in the elderly population
      worldwide. In the UK, more than half of people who are over 65 years old have some cataract
      development in one or both eyes. The only treatment that can restore functional visual
      ability is cataract surgery where the opacified crystalline lens is removed by
      phacoemulsification and an artificial intraocular lens is implanted. It is estimated that
      around 10 million cataract operations are performed around the world each year. Cataract
      operations are generally very successful, with a low risk of serious complications.

      During the past two decades, cataract surgery underwent tremendous change and modernisation
      resulting in today's small incision phacoemulsification surgery and a safe technique with a
      short rehabilitation time for the patient. Traditional spherical monofocal intraocular lenses
      (IOLs) restore best-corrected vision and may lessen the need for spectacles. These IOLs
      correct only the spherical portion of the total refractive error and do not correct corneal
      astigmatism. Astigmatism is a visually disabling refractive error affecting the general
      population, especially those with cataract. At least 15% to 20% of cataract patients have 1.5
      diopters (D) or more of corneal or refractive astigmatism. With increased patient
      expectations, the trend is not only to remove the cataract but also to address the problem of
      pre-existing astigmatism at the time of surgery.

      Surgical-induced astigmatism can be reduced by smaller incisions, i.e. microincision cataract
      surgery (MICS), which by definition is surgery performed through incisions smaller than 2.0
      mm, reducing the need for suturing. This results in better corneal optical quality, thus
      improving visual outcomes. There are also other surgical options to correct preexisting
      astigmatism during cataract surgery like: selectively positioning of the phacoemulsification
      incision; astigmatic keratotomy with corneal or limbal relaxing incisions; excimer laser
      refractive procedures such as photorefractive keratectomy, laser in situ keratomileusis, and
      laser-assisted subepithelial keratectomy; or implanting pseudophakic toric posterior chamber
      intraocular lenses (IOLs).

      Toric IOLs have been shown to result in good visual and refractive outcomes. Combined with
      MICS, these IOLs can allow effective correction of cylindrical errors intraoperatively,
      improving visual quality and thus leading to spectacle independence. Plate haptic and loop
      haptic toric IOLs have been considered for about a decade but have been associated with
      postoperative rotational instability. Rotation of a toric lens from its intended orientation
      degrades its corrective power, with approximately 3.3% loss of cylindrical power for every
      degree off axis. A misorientation of approximately 30° negates the effectiveness of
      astigmatic correction, and a misorientation of more than 30° may induce additional
      astigmatism. Although some patients are asymptomatic despite induced astigmatism, others
      experience symptoms such as blurred or distorted vision, headache, fatigue, eyestrain,
      squinting, or eye discomfort. Thus, IOL orientation stability is an essential goal in toric
      IOL design.

      RATIONALE

      The purpose of this study is to assess and compare the axial IOL rotation and optical quality
      (refraction, visual acuity, decentration and tilt) and capsular bag reaction after
      micro-incision surgery with an IOL implantation in cataract patients - Acrysof SN60WF, Tecnis
      ZCB00 & Envista MX60 IOL
    


Intervention name(s): Implantation of an Alcon Acrysof SN60WF intraocular lens; Implantation of an AMO Tecnis ZCB00 intraocular lens; Implantation of an Envista MX60 intraocular lens
Intervention type(s): Other; Other; Other
Intervention description(s): Patients suffering from senile cataract getting replaced their human crystalline cataractous lens; Patients suffering from senile cataract getting replaced their human crystalline cataractous lens; Patients suffering from senile cataract getting replaced their human crystalline cataractous lens
Allocation: Randomized
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Treatment