Tip of the Month
Publishing date: September 2013
The Science behind the Tip
In patients with ocular hypertension, moderate to severe retinal nerve fibre layer (RNFL) atrophy at baseline has been associated with a 7-8 times greater risk of subsequent visual field loss (1). RNFL damage can be found clinically in 60% of ocular hypertensive patients up to six years before changes are seen using perimetry.
In recent years, the RNFL has been evaluated using scanning laser polarimetry (GDx VCC) and optical coherence tomography. Both forms of technology are equally effective in detecting thinning of this layer (2). There is a good correlation between instruments, but thickness measurements taken with one instrument are not comparable with those taken with another (3). The best method of monitoring is obtained with the same operator and device (4).
Contributor: John Salmon, Oxford
1. Quigley HA, Enger C, Katz J et al. Risk factors for the development of glaucomatous visual field loss in ocular hypertension. Arch Ophthalmol 1994; 112: 644-649.
2. Pablo LE, Ferreras A, Schlottmann PG. Reginal nerve fibre layer evaluation in ocular hypertensive eyes using optic coherence tomography and scanning laser polarimetry in the diagnosis of early glaucomatous defects. Br J Ophthalmol 2011; 95: 51-55.
3. Kim HG, Heo H, Park SW. Comparison of scanning laser polarimetry and ocular coherence tomography in preperimetric glaucoma. Optom Vis Sci 2011; 88: 124-29.
4. Pierro L, Gagliardi M, Inliano L et al. Retinal nerve fibre layer thickness reproducibility using seven different OCT instruments. Invest Ophthalmol Vis Sci 2012; 31: 5912-5920.
Tip Reviewer: Roger Hitchings
Tip Editors: John Salmon and John Thygesen