advertisement

Editors Selection IGR 19-1

Refractive Errors: High Myopia and Glaucoma

Comment by Tsing-Hong Wang on:

74798 Intraocular Pressure and Glaucomatous Optic Neuropathy in High Myopia, Jonas JB; Nagaoka N; Fang YX et al., Investigative Ophthalmology and Visual Science, 2017; 58: 5897-5906

Find related abstracts

The authors conducted a hospital-based study in a third referral myopia clinic and demonstrated that higher prevalence of GON was correlated with higher IOP in eyes with an axial length of < 27.4 mm. However, in highly myopic eyes (axial length > 27.5 mm), the frequency of GON was not correlated with IOP.

Diagnosing glaucoma in a highly myopic eye is never an easy job. Many other reasons besides glaucoma can produce various visual filed defects in highly myopic eyes. OCT images also can't provide a clear distinction between a normal optic nerve and GON in the majority of highly myopic eyes. The authors made the diagnosis of GON by observing the ophthalmoscopic appearance of the optic nerve head. The neuroretinal rim had to have a clearly glaucoma-like appearance, either in the form of marked rim notches touching the disc border or in the form of an advanced loss of neuroretinal rim with an optic cup extending to the disc border for a large sector of the optic nerve head. This definition of GON may underestimate the prevalence of GON.

IOP was one of the main outcome parameters, but the study participants were enrolled into the study based on their myopia, while glaucoma was not a reason for attending the hospital. Therefore, some IOP related parameters such as IOP diurnal variation, blood pressure, and central corneal thickness were not assessed in the present retrospective study. The glaucomatous group as compared to the nonglaucomatous group had a significantly higher prevalence of IOP-lowering therapy, and this could also explain the lack of a difference in IOP between both groups.

If the observation of a missing association between IOP and GON in the highly myopic group in the present study population is valid, this may be due to the anatomic particularities of the high myopia optic nerve heads, such as thinning of the lamina cribrosa and a steeper translamina cribrosa pressure. It is possible that the influence on the glaucoma progression of these optic nerve features far outweigh that of IOP. Another reason could be that highly myopic glaucomatous eyes have a markedly lower IOP threshold to develop optic nerve damage, and a target IOP of much lower than the mid-teens might be necessary to prevent the development of GON in the highly myopic eyes.

• ← Previous
• Next →