Surgical Treatment of Concurrent Cataract and Primary Pterygium

Sponsor

Hospital Authority, Hong Kong (Other)

Overall Status

Unknown status

CT.gov ID

NCT00563277

Collaborator

(none)

Enrollment

Locations

Duration (Months)

Patients Per Site

Patients Per Site Per Month

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
Pterygium Cataract Lenses, Intraocular	Procedure: combined pterygium and cataract operation Procedure: pterygium excision followed by cataract operation	N/A

Study Design

Study Type:

Interventional

Anticipated Enrollment :

75 participants

Allocation:

Randomized

Intervention Model:

Parallel Assignment

Masking:

None (Open Label)

Primary Purpose:

Treatment

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

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

Secondary Outcome Measures

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

Eligibility Criteria

Criteria

Ages Eligible for Study:

18 Years and Older

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