May 2005
Volume 46, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2005
Validation of a Predictive Model for the Conversion From Ocular Hypertension to Glaucoma
Author Affiliations & Notes
  • F.A. Medeiros
    Hamilton Glaucoma Center, Department of Ophthalmology, University of California San Diego, La Jolla, CA
  • P.A. Sample
    Hamilton Glaucoma Center, Department of Ophthalmology, University of California San Diego, La Jolla, CA
  • L.M. Zangwill
    Hamilton Glaucoma Center, Department of Ophthalmology, University of California San Diego, La Jolla, CA
  • C.F. Gomi
    Hamilton Glaucoma Center, Department of Ophthalmology, University of California San Diego, La Jolla, CA
  • C. Bowd
    Hamilton Glaucoma Center, Department of Ophthalmology, University of California San Diego, La Jolla, CA
  • J.G. Crowston
    Hamilton Glaucoma Center, Department of Ophthalmology, University of California San Diego, La Jolla, CA
  • R.N. Weinreb
    Hamilton Glaucoma Center, Department of Ophthalmology, University of California San Diego, La Jolla, CA
  • Footnotes
    Commercial Relationships  F.A. Medeiros, None; P.A. Sample, None; L.M. Zangwill, None; C.F. Gomi, None; C. Bowd, None; J.G. Crowston, None; R.N. Weinreb, None.
  • Footnotes
    Support  NIH EY08208; NIH EY11008
Investigative Ophthalmology & Visual Science May 2005, Vol.46, 2471. doi:
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      F.A. Medeiros, P.A. Sample, L.M. Zangwill, C.F. Gomi, C. Bowd, J.G. Crowston, R.N. Weinreb; Validation of a Predictive Model for the Conversion From Ocular Hypertension to Glaucoma . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2471.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Abstract: : Purpose: To assess the external validity of a predictive model for the risk of conversion from ocular hypertension to glaucoma. Methods: Predictive models were derived from the Ocular Hypertension Treatment Study (OHTS) results. The performance of these models was assessed in an independent population from a longitudinal study (Diagnostic Innovations in Glaucoma Study – DIGS). Ocular hypertensive patients included in DIGS had elevated intraocular pressure (IOP) in both eyes (>22 mmHg), normal visual fields and normal optic discs. Glaucoma conversion was defined as development of reproducible visual field loss or progression of optic disc damage. Data on baseline risk factors for development of glaucoma, including age, IOP, central corneal thickness (CCT), vertical cup disc ratio (VCD), pattern standard deviation (PSD) and presence of diabetes mellitus were assessed for each patient. A predictive model was derived from the DIGS population and compared to the models derived from the OHTS results. For each risk factor, regression coefficients (hazard ratios) from the DIGS– and OHTS–derived models were compared using a z–test. The ability of the risk models to discriminate patients who developed glaucoma during follow–up from those who did not was evaluated by calculating the c statistic (ROC curve area). Model calibration was evaluated by comparing predicted and observed glaucoma events. Results: 37 (24%) of 153 patients developed glaucoma during follow–up. Mean follow–up time was 8 years (range: 1 to 17 years). 20 (54%) patients developed progression of optic disc, 15 (40%) developed abnormal visual fields and 2 (5%) developed both. Hazard ratios for DIGS– and OHTS–derived predictive models were similar for CCT (1.64 vs. 1.82 [per 40µm thinner]), IOP (1.10 vs. 1.11 [per 1 mmHg higher]), age (1.35 vs. 1.25 [per decade]), VCD (1.29 vs. 1.32 [per 0.1 higher]) and PSD (1.07 vs 1.25 [per 0.2 dB higher]). Hazard ratios were significantly different for the presence of diabetes (1.17 vs. 0.35). Similar results were obtained when risk models were developed without PSD and VCD. ROC curve areas for the discriminatory abilities of the OHTS risk models when applied to the DIGS population ranged from 0.68 to 0.71 and were similar to those of DIGS–derived models. Calibrations of models without VCD and PSD were better than those of models incorporating these variables. Conclusions: Risk models derived from the OHTS results performed reasonably well to predict risk of conversion from ocular hypertension to glaucoma in an independent population.

Keywords: clinical (human) or epidemiologic studies: risk factor assessment • clinical (human) or epidemiologic studies: biostatistics/epidemiology methodology 
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