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Editors Selection IGR 23-2

Imaging: Baseline predictions

David Greenfield

Comment by David Greenfield on:

15242 Baseline optical coherence tomography predicts the development of glaucomatous change in glaucoma suspects, Lalezary M; Medeiros FA; Weinreb RN et al., American Journal of Ophthalmology, 2006; 142: 576-582


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Several studies from the Hamilton Glaucoma Center have demonstrated that computerized imaging of the optic nerve and peripapillary retinal nerve fiber layer provide unique and clinically relevant information regarding glaucoma risk assessment and prediction of subsequent progression. Using scanning laser polarimetry (SLP, GDx-VCC, Carl Zeiss Meditec, Dublin, CA), Mohammadi and colleagues1 demonstrated that thinner baseline retinal nerve fiber layer (RNFL) measurements were independently predictive of subsequent visual field loss among a population of glaucoma suspects. The Confocal Scanning Laser Ophthalmoscopy (CSLO) Ancillary Study2 provided the first evidenced-based documentation that an imaging technology is valid using established glaucoma endpoints. This excellent study found that even when the optic disc is not classified as glaucomatous and the standard visual field is normal, certain optic disc features obtained using CSLO are associated with development of POAG. The study by Lalezary et al. (1128) adds to this list and suggests that optical coherence tomography (OCT2, Carl Zeiss Meditec, Dublin, CA) generated RNFL measurements, independently and when combined with other known predictive factors, can assist the clinician in assessing the likelihood of developing POAG. Lalezary et al. carefully studied 114 glaucoma suspects with disc photography, standard perimetry, and OCT imaging over a mean 4.2 years of follow-up. They found that thinner baseline RNFL thickness as measured using OCT2, thinner central corneal thickness values, increased intraocular pressure, and greater visual field pattern standard deviation values were predictive of glaucomatous change (optic disc or visual field). After adjusting for confounding factors, a ten micron thinner baseline RNFL thickness was independently predictive of progression.

A ten micron thinner baseline RNFL thickness was independently predictive of progression
Studies such as this one usher a new era in the evaluation and management of glaucoma. For the clinician, the single most important question is how to assess the risk of glaucoma in an individual patient. While single measures are useful for assessing risk, consideration of all clinical information will provide the most robust strategy for identifying patients in whom treatment is beneficial. Undoubtedly, models of global risk assessment will evolve that incorporate computerized assessments of the optic disc and RNFL in conjunction with established clinical parameters. This excellent study has certainly answered some questions and raised others that warrant further study.

References

  1. Mohammadi K, Bowd C, Weinreb RN, Medeiros FA, Sample PA, Zangwill LM. Retinal nerve fiber layer thickness measurements with scanning laser polarimetry predict glaucomatous visual field loss. Am J Ophthalmol 2004; 138: 592-601.
  2. Zangwill LM, Weinreb RN, Beiser JA, et al. Baseline topographic optic disc measurements are associated with the development of primary open-angle glaucoma: The Confocal Scanning Laser Ophthalmoscopy Ancillary Study to the Ocular Hypertension Treatment Study. Arch Ophthalmol 2005; 123: 1188-1197.


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