The answer and how to proceed

A 25-year-old patient in overall good health asked at the conclusion of his exam, “What is my risk of developing glaucoma if I am nearsighted?” It’s a good question, considering hyperopia, or farsighted refractive error, may be a risk factor for primary angle-closure glaucoma due to small eyes that have relative crowded anterior segment structures.¹

THE ANSWER

Independent of the risk factors of IOP, confirmed family ocular history, African American ancestry, thin pachymetry readings, older age, vascular dysregulation, systemic factors and hyperopia, the Blue Mountains Eye Study, comprised of a cross-section population of over 3,600 patients (ages 49 to 97), shows that myopic patients had a two- to three-times increased risk of developing glaucoma compared to non-myopic patients.²

The Early Manifest Glaucoma Trial, a randomized, prospective study of close to 33,000 patients (ages 57 to 79) reveals that glaucoma prevalence was proportional to increasing myopia status and, interestingly, that this association was strongest at lower IOP levels, indicating a risk factor for normal tension glaucoma.³

The Beijing Eye Study, comprised of 4,439 patients age 40 and older, similarly confirms that moderate/high myopia (>-6.00 D to -8.00 D) was significantly associated with glaucoma.⁴

More recently, a cross-sectional analysis and a systematic review and meta-analysis of observational studies, comprised of 13 studies involving close to 50,000 individuals, shows a strong association between myopia and open-angle glaucoma.⁵

Finally, the World Glaucoma Association says that, “Existing evidence suggests that individuals who have myopia have an increased risk of developing open-angle glaucoma, with the risk being greater for people who have high myopia.”⁶

THE DIAGNOSTIC DILEMMA

Despite the clear connection between myopia and glaucoma, actually diagnosing glaucoma or detecting disease progression among myopic patients is much less clear: Myopic nerves, with their associated variable nerve sizes, optic nerve rotation/tilted insertion, glaucomatous-like preferential neuroretinal rim thinning and abnormal OCT RNFL vertical thinning (especially if outside the reference database), causes us to ponder deeply: “Is this patient myopic with a glaucomatous-looking nerve or is this a patient who has glaucoma and is myopic?”^7-9

When faced with this common and challenging diagnostic dilemma, we should consider these practice principles and approaches (italics added for emphasis):

• “When the patient in front of us is a glaucoma suspect, particularly when myopic changes are objectified, we should take into account that one examination could not be sufficient to certify the diagnosis.”¹⁰
• “Ultimately, the evaluation of glaucoma in myopia requires a multimodal approach to allow correlation between structural and functional assessments.”⁹
• “Longitudinal observation may be necessary to distinguish among the multiple effects of myopia on the optic nerve and the natural history of glaucoma, which may vary substantially amongst those who are affected.”¹¹
• “Whether to treat for glaucoma relies on the suspicion level of the clinician, who must consider other risk factors for vision loss. Ultimately, it is the progression of glaucoma-like findings that determines whether a myopic patient has glaucoma.”¹²
• “Diagnosis of glaucoma among myopic eyes can be challenging. Confirmed evidence of glaucomatous progression from a well-defined baseline is important for a correct diagnosis in many myopic individuals.”⁶

TAKE A FARSIGHTED APPROACH

When it comes to caring for our myopic patients who present for a routine exam, let’s avoid the nearsighted approach of just prescribing glasses or contact lenses. Instead, let’s take a farsighted approach by looking for individual risk factors for glaucoma among our myopic patients at each exam. Doing so may help us diagnose glaucoma earlier and/or detect disease progression sooner. OM

REFERENCES

1. Shen L, Melles RB, Metlapally R, et al. The Association of Refractive Error with Glaucoma in a Multiethnic Population. Ophthalmology. 2016;123(1):92-101. doi: 10.1016/j.ophtha.2015.07.002.
2. Mitchell P, Hourihan F, Sandbach J, Wang JJ. The relationship between glaucoma and myopia: the Blue Mountains Eye Study. Ophthalmology. 1999 Oct;106(10):2010-5. doi: 10.1016/s0161-6420(99)90416-5.
3. Grødum K, Heijl A, Bengtsson B. Refractive error and glaucoma. Acta Ophthalmol Scand. 2001;79(6):560-6.
4. Xu L, Wang Y, Wang S, Wang Y, Jonas JB. High myopia and glaucoma susceptibility the Beijing Eye Study. Ophthalmology. 2007;114(2):216-20. doi: 10.1016/j.ophtha.2006.06.050.
5. Marcus MW, de Vries MM, Junoy Montolio FG, Jansonius NM. Myopia as a risk factor for open-angle glaucoma: a systematic review and meta-analysis. Ophthalmology. 2011 Oct;118(10):1989-1994.e2. doi: 10.1016/j.ophtha.2011.03.012.
6. Weinreb R.N., Garway-Heath D.F., Leung C., Medeiros F.A., Liebmann J. Diagnosis of Primary Open Angle Glaucoma – Consensus Series 10. Kugler Publications. The Netherlands, Amsterdam. 2016.
7. Na KI, Lee WJ, Kim YK, Park KH, Jeoung JW. Evaluation of Retinal Nerve Fiber Layer Thinning in Myopic Glaucoma: Impact of Optic Disc Morphology. Invest Ophthalmol Vis Sci. 2017;58(14):6265-6272. doi: 10.1167/iovs.17-22534.
8. Rauscher FM, Sekhon N, Feuer WJ, Budenz DL. Myopia affects retinal nerve fiber layer measurements as determined by optical coherence tomography. J Glaucoma. 2009;18(7):501-5. doi: 10.1097/IJG.0b013e318193c2be.
9. Tan NYQ, Sng CCA, Jonas JB, Wong TY, Jansonius NM, Ang M. Glaucoma in myopia: diagnostic dilemmas. Br J Ophthalmol. 2019;103(10):1347-1355. doi: 10.1136/bjophthalmol-2018-313530.
10. Dascalescu D, Corbu C, Coviltir V, et al. The ganglion cell complex as an useful tool in glaucoma assessment. Rom J Ophthalmol. 2018;62(4):300-303.
11. Chang RT, Singh K. Myopia and glaucoma: diagnostic and therapeutic challenges. Curr Opin Ophthalmol. 2013;24(2):96-101. doi: 10.1097/ICU.0b013e32835cef31.
12. Hsu CH, Chen RI, Lin SC. Myopia and glaucoma: sorting out the difference. Curr Opin Ophthalmol. 2015;26(2):90-5. doi: 10.1097/ICU.0000000000000124.

DR. LIFFERTH practices at Center for Sight. He is a member of the Optometric Glaucoma Society and a Glaucoma Diplomate of the American Academy of Optometry. For additional glaucoma cases, you can also follow Dr. Lifferth on his Instagram account: glaucomaqd. Disclosures: None. Email him at glaucomaqd@yahoo.com.