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Editors Selection IGR 9-4

Examination methods: Parapapillary autofluorescence

Comment by Felipe Medeiros on:

13774 Correlation between retinal nerve fiber layer thickness and central corneal thickness in patients with ocular hypertension: an optical coherence tomography study, Kaushik S; Gyatsho J; Jain R et al., American Journal of Ophthalmology, 2006; 141: 884-890

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Several studies have shown that a considerable subset of patients currently classified as having ocular hypertension (OHT) may simply have thicker than average corneas that result in an overestimation (by Goldmann applanation tonometry) of what is likely a normal, true intraocular pressure (IOP). As a consequence, OHT patients with thicker corneas would be at a lower risk for glaucoma development. In contrast, the development of more sensitive methods for detection of structural and functional damage in glaucoma has provided evidence that some patients previously classified as having OHT have, in fact, initial damage not detected by conventional methods. This evidence collectively suggests that patients currently diagnosed as having OHT may include some in whom intraocular pressure has been overestimated as well as some with early glaucomatous damage. It is conceivable that OHT patients at higher risk for glaucoma development would be the ones more likely to show evidence of early glaucomatous structural and functional loss when evaluated with more sensitive tests. Kaushik et al. (301) recently provided more evidence to support this. These authors obtained CCT measurements and performed Stratus OCT retinal nerve fiber layer (RNFL) and optic nerve head (ONH) scans in a group of 51 patients with OHT and 35 normal subjects. They found that OHT patients with thin corneas (less than 555 µm) had significantly thinner RNFL thickness measurements than normal subjects, whereas OHT subjects with thick corneas had RNFL thickness measurements similar to those of the control group. As the authors state in their discussion, this could imply that OHT subjects with thinner corneas may either have early structural damage that has not yet manifested as characteristic optic nerve damage or visual field loss or they may represent a subset of patients who have an increased susceptibility to glaucomatous damage in the presence of high IOP and thin RNFL.

OHT subjects with thinner corneas may either have early structural damage that has not yet manifested as characteristic optic nerve damage or visual field loss or they may represent a subset of patients who have an increased susceptibility to glaucomatous damage in the presence of high IOP and thin RNFL

Their results agree with those of previous studies showing that OHT patients with thin corneas have early evidence of structural and/or functional damage when tested with short-wavelength automated perimetry (SWAP), frequency doubling technology perimetry (FDT) or scanning laser polarimetry.^1-3 It is likely that the incorporation of results from these instruments into predictive models for the development of glaucoma will improve our ability to identify those OHT subjects at higher risk for developing the disease.

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