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Estimation of Goldmann applanation tonometer intraocular pressure (IOP) from scleral Schiotz IOP values in eyes with type-1 keratoprostheses
  1. Sirisha Senthil1,
  2. Raghava Chary1,
  3. Mohammed Hasnat Ali2,
  4. Nikhil S Choudhari1,
  5. Chandra Sekhar Garudadri1
  1. 1Department of Glaucoma, VST Glaucoma Center, LV Prasad Eye Institute, Hyderabad, Telangana, India
  2. 2Biostatistics, LV Prasad Eye Institute, Hyderabad, Telangana, India
  1. Correspondence to Dr Sirisha Senthil, VST Glaucoma Center, LV Prasad Eye Institute, Hyderabad, Telangana, India; sirishasenthil{at}


Purpose To validate estimation of Goldmann applanation tonometer (GAT) intraocular pressure (IOP) from scleral Schiotz IOP measurements using a regression model in normal eyes and eyes with type-1 keratoprostheses.

Methods In this prospective cross-sectional study, cohort-1 had 253 normal anterior segment eyes, and cohort-2 had 100 eyes with type-1 keratoprostheses. Scleral Schiotz IOP measurements were used (in a non-linear model) to predict GAT IOP values for these eyes. Accuracy of predicted GAT IOP values was assessed using actual GAT IOP values for normal eyes, while for type-1 keratoprosthetic eyes, finger tension (FT) IOP assessments by an experienced glaucoma specialist were used. Primary outcome was agreement between FT IOP (assessed by an experienced glaucoma specialist) and predicted GAT IOP-derived clusters.

Results The actual values of GAT IOP measurements in normal eyes (n=253; mean age ±SD, 51.35±15.56 years) ranged between 6 mm Hg and 62 mm Hg (mean=22±10.05 mm Hg). Estimated and actual GAT IOP values for normal eyes were very similar (mean difference=0.05 mm Hg with limits of agreement: −5.39 to 5.5 by Bland-Altman plot). Of the 100 eyes with type-1 keratoprostheses, 68 were classified as having digitally normal IOP, 28 as borderline and 4 as high. The agreement between classification by FT assessment and model-predicted GAT IOP values was substantial (Kappa=0.81, 95% CI 0.69 to 0.93). The accuracy of the model in assessing IOP was found to be 91% (95% CI 0.84 to 0.96).

Conclusion Scleral Schiotz IOP values along with our predictive model can be an alternative objective method to FT IOP in assessing IOP in eyes with type-1 keratoprostheses.

  • cornea
  • glaucoma
  • intraocular pressure
  • ocular surface
  • prosthesis

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  • Contributors SS, contributed in conception, design, acquisition, analysis, interpretation of data, drafting the manuscript and critically revising it. MHA helped with data analysis and interpretation of data. NSC and CSG contributed in revising it critically for important intellectual content to get the article published.

  • Funding Hyderabad Eye Research Foundation (LEC-12-15-125).

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Ethics approval The study was conducted at the L V Prasad Eye Institute, Hyderabad (LEC-12-15-125). Informed consent was obtained from all participants, and the Ethics Committee of L V Prasad Eye Institute approved the study methodology.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data are available upon reasonable request. data will be available on request, available with

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