In vivo measurement of regional variation in anterior scleral resistance to Schiotz indentation

Hetal Patel, Bernard Gilmartin, Robert P. Cubbidge, Nicola S. Logan

Research output: Contribution to journalArticlepeer-review


Purpose: Recent studies indicate that ocular and scleral rigidity is pertinent to our understanding of glaucoma, age related macular degeneration and the development and pathogenesis of myopia. The principal method of measuring ocular rigidity is by extrapolation of data from corneal indentation tonometry (Ko) using Friedenwald’s transformation algorithms. Using scleral indentation (Schiotz tonometry) we assess whether regional variations in resistance to indentation occur in vivo across the human anterior globe directly, with reference to the deflection of Schiotz scale readings.
Methods: Data were collected from both eyes of 26 normal young adult subjects with a range of refractive error (mean spherical equivalent ± S.D. of -1.77 D ± 3.28 D, range -10.56 to +4.38 D). Schiotz tonometry (5.5 g & 7.5 g) was performed on the cornea and four scleral quadrants; supero-temporal (ST) and -nasal (SN), infero-temporal (IT) and -nasal (IN) approximately 8 mm posterior to the limbus.
Results: Values of Ko (mm3)-1 were consistent with those previously reported (mean 0.0101 ± 0.0082, range 0.0019–0.0304). In regards to the sclera, significant differences (p < 0.001) were found across quadrants with indentation readings for both loads between means for the cornea and ST; ST and SN; ST and IT, ST and IN. Mean (±S.D.) scale readings for 5.5 g were: cornea 5.93 ± 1.14, ST 8.05 ± 1.58, IT 7.03 ± 1.86, SN 6.25 ± 1.10, IN 6.02 ± 1.49; and 7.5 g: cornea 9.26 ± 1.27, ST 11.56 ± 1.65, IT 10.31 ± 1.74, SN 9.91 ± 1.20, IN 9.50 ± 1.56.
Conclusions: Significant regional variation was found in the resistance of the anterior sclera to indentation produced by the Schiotz tonometer.
Original languageEnglish
Pages (from-to)437-443
Number of pages7
JournalOphthalmic and Physiological Optics
Issue number5
Early online date19 Apr 2011
Publication statusPublished - Sept 2011


  • adolescent
  • adult
  • analysis of variance
  • cornea
  • female
  • humans
  • intraocular pressure
  • macular degeneration
  • male
  • myopia
  • reference values
  • sclera
  • ocular tonometry
  • young adult


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