Clinical trial NCT00563277: Surgical Treatment of Concurrent Cataract and Primary Pterygium
Official title: Surgical Treatment of Concurrent Cataract and Primary Pterygium: A Randomized Control Trial
Study type: INTERVENTIONAL
Overall status: UNKNOWN
Phase: NA
Conditions: Pterygium
Cataract
Lenses, Intraocular
Keywords: Pterygium
Cataract
Intraocular lens power calculation accuracy
Lead sponsor: Hospital Authority, Hong Kong
Sponsor class: OTHER_GOV
First posted: 2007-11-26
Enrollment: 75
Sex: ALL
Minimum age (years): 18
Standard ages: ADULT
OLDER_ADULT
Allocation: RANDOMIZED
Intervention model: PARALLEL
Primary purpose: TREATMENT

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.


Eligibility criteria: 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

Primary outcomes:
measure: final refraction deviation from target
timeFrame: 1 and 3 months post cataract operation
Secondary outcomes:
measure: change of IOL power from pre-pterygium estimated power
timeFrame: 1 and 3 months post pterygium excision
Other outcomes:
Locations:
city: Hong Kong
country: China
facility: Alice Ho Miu Ling Nethersole Hospital
city: Hong Kong
country: China
facility: Hong Kong Eye Hospital
city: Hong Kong
country: China
facility: Prince of Wales Hospital
Study officials:
affiliation: Department of DOVS, Prince of Wales Hospital/ The Chinese University of Hong Kong
name: Lulu Cheng, Dr
role: PRINCIPAL_INVESTIGATOR
References: