Assessment of Changes in Corneal Scar Density After Primary Pterygium Excision

with Adjuvant Mitomycin C

Authors

Alvin L. Young, MMedSc (Hons), FRCSIrel

Ka Wai Kam, MRCSEd

Rachel Pui Wai Kwok, MRCSEd, MMRes

Vishal Jhanji, MD, FRCS

Prince of Wales HospitalThe Chinese University of Hong Kong

The Authors Have No Financial Interest To Disclose.

Aims & Objectives

• We aim to assess the changes with time in the corneal scar density of patients following pterygium excision and topical mitomycin C application by serial Scheimpflug images

Materials & Methods

• We recruited patients undergoing primary, single headed pterygium excision with topical mitomycin C.

• Postoperatively patients were prescribed 4 weeks of combined topical corticosteroid and antibiotic eyedrops.

• Scheimpflug images were captured with the Pentacam device at postoperative 1, 4 and 12 weeks.

• Anterior 120um layer of the total 10-12 millimeter zone.

• Statistical analyses were performed to compare density values obtained at postoperative week 1, 4 and 12.

Outcomes

• Primary outcome• Corneal density of the anterior 120um layer of the total 10-12mm zone at POW 1, 4,

12.

• Secondary outcomes• Corneal density of the middle and posterior layers of the total 10-12mm zone POW 1,

4, 12

• Visual acuities / Intraocular pressures

• Status of crystalline lenses / any recurrence of pterygium at 12 week

Results

• 31 eyes of 31 patients

• M: F – 16: 15

• L: R – 19:12

• Mean age at operation 62.0 +/- 9.4 years

WEEK 4 VS 1MEAN REDUCTION IN CORNEAL DENSITY

VALUE P VALUE PERCENTAGES P-VALUE

ANTERIOR -3.07 (-6.60, +0.46)

0.086 - 4.7% (-10.7, +1.3)

0.112

WEEK 12 VS 1ANTERIOR -3.46 (-6.79, -

0.12)0.043 -6.3% (-11.8, -0.7) 0.028

MIDDLE +0.87 (-0.83, +1.00)

0.847 +1.1% (-2.2, +4.5)

0.781

POSTERIOR +1.077(+0.34,, +1.82)

0.006 +6.6% (+2.6, +10.5)

0.002

Results

Week 12

Week 1

Week 12- Week 1

Discussion / Strength

• First objective study looking at chronic corneal scar density evolution with time

• Densitometry offers a new perspective in assessment of corneal scar

• Since most of the corneal surface remained untouched during operation, any changes detected in the total anterior layer of the 10-12mm zone should reflect the change in average density of the scarred region.

Discussion/ Limitation

• Pentacam does not offer tracking feature• By obtaining the average density of the total 10-12 mm zone,

and by assuming that the density of the untouched areas of the cornea remains unchanged, any change in values obtained should reflect the change in the scarred area of interest

• Small sample size• Despite a small sample size of 31, we were able to

demonstrate significant changes at week 12.

• Non-randomized nature• This might introduce selection bias into our study

• Interference from artefacts• Although all images analysed were of good quality as

indicated by the inherent Quality Specification feature of the Pentacam, artefacts were sometimes noted graphically.

Conclusions

• Chronic corneal scars in anterior stroma became less dense at 12 weeks postoperatively

• Surprisingly there is a significant increase in density of the posterior layer at the same time

• These changes may be considered as baseline for future study in determining whether intervention plays a role in further reducing corneal densities