Surgical Treatment of Concurrent Cataract and Primary Pterygium

Hospital Authority, Hong Kong (Other)
Overall Status
Unknown status ID

Study Details

Study Description

Brief Summary

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 or Disease Intervention/Treatment Phase
  • Procedure: combined pterygium and cataract operation
  • Procedure: pterygium excision followed by cataract operation

Study Design

Study Type:
Anticipated Enrollment :
75 participants
Intervention Model:
Parallel Assignment
None (Open Label)
Primary Purpose:
Official Title:
Surgical Treatment of Concurrent Cataract and Primary Pterygium: A Randomized Control Trial
Study Start Date :
Oct 1, 2004
Anticipated Study Completion Date :
Dec 1, 2006

Outcome Measures

Primary Outcome Measures

  1. final refraction deviation from target [1 and 3 months post cataract operation]

Secondary Outcome Measures

  1. change of IOL power from pre-pterygium estimated power [1 and 3 months post pterygium excision]

Eligibility Criteria


Ages Eligible for Study:
18 Years and Older
Sexes Eligible for Study:
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

Contacts and Locations


Site City State Country Postal Code
1 Alice Ho Miu Ling Nethersole Hospital Hong Kong China
2 Hong Kong Eye Hospital Hong Kong China
3 Prince of Wales Hospital Hong Kong China

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

Study Documents (Full-Text)

None provided.

More Information

Additional Information:


None provided.
Responsible Party:
, , Identifier:
Other Study ID Numbers:
  • CRE-2004.274-T
  • HARECCTR0500012
First Posted:
Nov 26, 2007
Last Update Posted:
Jul 7, 2010
Last Verified:
Jul 1, 2010
Keywords provided by , ,
Additional relevant MeSH terms:

Study Results

No Results Posted as of Jul 7, 2010