International Ophthalmology

, Volume 39, Issue 4, pp 911–916 | Cite as

Novel grid and sectoral analyses in monitoring corneal scars

  • Ka Wai Kam
  • Anita Li
  • Rachel Pui Wai Kwok
  • Michael W. Belin
  • Alvin L. YoungEmail author
Original Paper



We aim to design two sampling methods, the grid and sectoral methods, to provide more precise detection of focal corneal scar changes with time following pterygium excision with the Pentacam imaging system.


This is a retrospective study of our previous prospective observational case series. Thirty patients underwent primary pterygium excision with adjuvant topical mitomycin-C application were followed up and imaged with Pentacam system at postoperative weeks 1, 4, 12 and month 18. Grid and sectoral methods were used to sample density changes (in grayscale units, GSU) over the scarred areas as well as the clear pole of the same cornea.


Using the grid method, the average corneal densities were 39.4, 37.1, 36.7 and 34.7 GSU at postoperative 1, 4, 12 weeks and 18 months, respectively. On the other hand, using the sectoral method, the average corneal densities were 35.3, 33.3, 32.5 and 31.9 GSU at postoperative 1, 4, 12 weeks and 18 months, respectively. Paired t tests achieved statistical significance when comparing all follow-up time points to first postoperative visit. A statistically significant effect of time on the average density was shown on ANOVA (p < 0.001) using both analyses over the scarred areas, but not over the clear pole of the same cornea (p > 0.05).


Our novel approach to monitor corneal density changes using the grid or sectoral sampling methods seemingly enhances the power in monitoring density changes in corneal scars when compared to conventional total-diameter average densitometry.


Cornea Scar Pterygium Densitometry Scheimpflug image 


Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.


  1. 1.
    Liu T, Liu Y, Xie L et al (2013) Progress in the pathogenesis of pterygium. Curr Eye Res 38:1191–1197CrossRefGoogle Scholar
  2. 2.
    Kaufman SC, Jacobs DS, Lee WB et al (2013) Options and adjuvants in surgery for pterygium: a report by the American Academy of Ophthalmology. Ophthalmology 120:201–208CrossRefGoogle Scholar
  3. 3.
    Young AL, Ho M, Jhanji V et al (2013) Ten-year results of a randomized controlled trial comparing 0.02% mitomycin C and limbal conjunctival autograft in pterygium surgery. Ophthalmology 120:2390–2395CrossRefGoogle Scholar
  4. 4.
    Tsim NC, Young AL, Jhanji V et al (2015) Combined conjunctival rotational autograft with 0.02% mitomycin C in primary pterygium surgery: a long-term follow-up study. Br J Ophthalmol 99:1396–1400CrossRefGoogle Scholar
  5. 5.
    Young AL (2013) The use of conjunctival rotational autograft in the management of pterygium. Asia Pac J Ophthalmol (Phila) 2:209–210CrossRefGoogle Scholar
  6. 6.
    Kheirkhah A, Safi H, Molaei S et al (2012) Effects of pterygium surgery on front and back corneal astigmatism. Can J Ophthalmol 47:423–428CrossRefGoogle Scholar
  7. 7.
    Kheirkhah A, Safi H, Nazari R et al (2012) Effects of pterygium surgery on front and back corneal surfaces and anterior segment parameters. Int Ophthalmol 32:251–257CrossRefGoogle Scholar
  8. 8.
    Kam KW, Kwok RP, Belin MW et al (2016) Long term density changes in corneal layers following primary pterygium excision with topical mitomycin-C. Cornea 35:1093–1096CrossRefGoogle Scholar
  9. 9.
    Kam KW, Belin MW, Young AL (2015) Monitoring corneal densities following primary pterygium excision with adjuvant topical mitomycin-C application—an observational study of corneal scar changes. Cornea 34:530–534CrossRefGoogle Scholar
  10. 10.
    Pahuja N, Shetty R, Subbiah P et al (2016) Corneal densitometry: repeatability in eyes with keratoconus and postcollagen cross-linking. Cornea 35:833–837CrossRefGoogle Scholar

Copyright information

© Springer Nature B.V. 2018

Authors and Affiliations

  • Ka Wai Kam
    • 1
  • Anita Li
    • 2
  • Rachel Pui Wai Kwok
    • 1
  • Michael W. Belin
    • 3
  • Alvin L. Young
    • 1
    • 2
    Email author
  1. 1.Department of Ophthalmology and Visual Sciences, Prince of Wales HospitalThe Chinese University of Hong KongShatinHong Kong
  2. 2.Department of Ophthalmology and Visual SciencesThe Chinese University of Hong KongShatinHong Kong
  3. 3.Department of Ophthalmology and Visual ScienceUniversity of ArizonaTucsonUSA

Personalised recommendations