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Surgical Treatment of Concurrent Cataract and Primary Pterygium

The recruitment status of this study is unknown. The completion date has passed and the status has not been verified in more than two years.
Verified July 2010 by Hospital Authority, Hong Kong.
Recruitment status was:  Recruiting
Information provided by:
Hospital Authority, Hong Kong Identifier:
First received: November 21, 2007
Last updated: July 6, 2010
Last verified: July 2010

Pterygium is known to induce with-the-rule astigmatism. The corneal curvature along the long axis of the pterygium body is flattened. The excision of pterygium will result in steepening of the cornea and reduction of astigmatism. Therefore, the effect of pterygium excision on intraocular lens (IOL) power calculation has been examined in our previous study. The study confirmed that pterygium can cause alteration of IOL power.

The determination of IOL power for cataract surgery is usually calculated from IOL formula called SRK II formula. IOL power = A - (2.5 x AL)-(0.9 x K). Variable A denotes the A-constant of the intraocular lens which is dependent on the IOL material and refractive index. Other variables for input include axial length (AL) and keratometry (K). A larger K reading will result in a lower estimated IOL power and vice versa. Previous studies have documented simultaneous cataract and pterygium operation resulted in reasonable visual outcome without adjustment of IOL power.

With the presence of a pterygium, the cornea is flattened and lead to a reduction of K value and over-estimation of calculated IOL power. This randomized controlled trial is designed to compare the refractive outcomes of sequential and simultaneous pterygium and cataract operation.

Pterygium excision should be done with various adjuvant therapies to minimize recurrence. Our previous studies reliably demonstrated limbal conjunctival graft and mitomycin C were effective methods to achieve low pterygium recurrence. We use limbal conjunctival autograft as the adjuvant therapy in the current study because this method is safer to be performed either alone or in combination with phacoemulsification. We avoid using mitomycin C as the adjuvant therapy in order to minimize the possibility of intraocular toxicity due to seepage.

Condition Intervention
Lenses, Intraocular
Procedure: combined pterygium and cataract operation
Procedure: pterygium excision followed by cataract operation

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Open Label
Primary Purpose: Treatment
Official Title: Surgical Treatment of Concurrent Cataract and Primary Pterygium: A Randomized Control Trial

Resource links provided by NLM:

Further study details as provided by Hospital Authority, Hong Kong:

Primary Outcome Measures:
  • final refraction deviation from target [ Time Frame: 1 and 3 months post cataract operation ]

Secondary Outcome Measures:
  • change of IOL power from pre-pterygium estimated power [ Time Frame: 1 and 3 months post pterygium excision ]

Estimated Enrollment: 75
Study Start Date: October 2004
Estimated Study Completion Date: December 2006

Ages Eligible for Study:   18 Years and older   (Adult, Senior)
Sexes Eligible for Study:   All

Inclusion Criteria:

  • >18 years old
  • Primary pterygium > 2mm across corneal limbus [Measurement made from the imaginary line of surgical limbus to the most advance edge of the visible pterygium tissue] Concurrent visually significant cataract ( BCVA < 20/70 )
  • Informed consent for both pterygium and cataract surgery

Exclusion Criteria:

  • Temporal pterygium
  • Double headed pterygium
  • Previous ocular surgery in which conjunctival-limbal graft is not feasible
  • Pterygium covering visual axis that preclude keratometric assessment
  • History of scleritis or autoimmune diseases
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Please refer to this study by its identifier: NCT00563277

Contact: Lulu Cheng, Dr (852) 2632 2878

Alice Ho Miu Ling Nethersole Hospital Recruiting
Hong Kong, China
Hong Kong Eye Hospital Recruiting
Hong Kong, China
Sub-Investigator: Dennis Lam, Prof         
Prince of Wales Hospital Recruiting
Hong Kong, China
Sub-Investigator: Alvin Young, Dr         
Sub-Investigator: Gloria Leung, Dr         
Sub-Investigator: Arthur Cheng, Prof         
Sponsors and Collaborators
Hospital Authority, Hong Kong
Principal Investigator: Lulu Cheng, Dr Department of DOVS, Prince of Wales Hospital/ The Chinese University of Hong Kong
  More Information

Additional Information: Identifier: NCT00563277     History of Changes
Other Study ID Numbers: CRE-2004.274-T
Study First Received: November 21, 2007
Last Updated: July 6, 2010

Keywords provided by Hospital Authority, Hong Kong:
Intraocular lens power calculation accuracy

Additional relevant MeSH terms:
Lens Diseases
Eye Diseases
Conjunctival Diseases processed this record on April 26, 2017