A hyperopic myope? Marfan syndrome and aphakia.

Have you heard of a hyperopic myope? PC shared an interesting case with the Myopia Profile Facebook community that involved an aphakic hyperopic patient, who in reality is a high myope with Marfan Syndrome and an incredibly long axial length.

Marfan syndrome is a connective tissue disorder that affects the cardiovascular, ocular and skeletal organ systems.¹ Patients with this condition usually have high myopia. Other ocular features¹ can include:

• Amaurosis (2%)
• Amblyopia (3%)
• Cataract (12%)
• Ectopia lentis (30%)
• Ectopia pupillae (3%)
• Glaucoma (5%)
• Lens in vitreous (2%)
• Optic nerve atrophy (1%)
• Retinal detachment (4%)
• Retinal rupture (1%)
• Strabismus (9%)

The average axial length of healthy person is 24.73mm.² The crystalline lens usually contributes approximately 15-20D to the optics of the eyeball.

With the crystalline lens removed, one would expect an aphakic patient to have a refractive error of approximately +15 to +20D. Hence, with a refractive error in the high +4's, this patient is much less hyperopic (or more myopic) than she should be. This is further supported by her 30.9mm axial length reading.

Managing progression in an adult myope with Marfan syndrome can be complicated, as the condition predisposes him/her to such progression. As the current evidence base does not include such patients, practitioners should be cautious when making recommendations on the efficacy of myopia control.

Whether myopia control strategies are implemented or not, with such high axial length, this patient is at a much higher risk of ocular disease. Hence, annual follow up is necessary to monitor ocular health, and the patient should be educated as such.

YCC shared data of a patient with high myopia and progressive axial elongation They offered an interesting approach in arresting axial length progression by prescribing anti-glaucoma drugs in order to slow myopia progression. Qi et al showed less myopic regression with 0.5% timolol on progressing post-LASIK patients.³ However, the biomechanics of myopic regression in post-LASIK patients are not directly comparable to that of normal myopic progression as the former can be influenced by corneal thickness, ablation depth, optical zone size and more.⁴ On the other hand, Goldschmidt et al showed that 0.25% timolol drop twice daily for a year had no myopia control effect (n=10).⁵.Therefore, further research about the efficacy of timolol in myopia control is needed.

In addition to timolol (and apart from atropine), other drugs under research for myopia control efficacy include 7-methylxanthine and pirenzepine. A pilot study by Trier et al showed that 7-methylxantine was effective in slowing myopia progression in Danish myopes.⁶ Pirenzepine has also been shown to be effective in slowing myopia, though not without adverse effects.^7-9

Hence, low-dose atropine remains to be most commonly used pharmacological agent in children for myopia control. It has minimal side effects and has a great safety profile. To learn more about atropine, read the The latest and greatest research on atropine and When to prescribe atropine for myopia control.

1. In complex presentations with a history of pathology and/or ocular surgery, there is more than meets the eye - remember that refractive error may only one part of the story. The clinical picture still needs to make sense. If an aphakic patient is only +4.00, they are not really as hyperopic as one may be led to believe.
2. Atropine remains to be the only proven pharmacological form of myopia control. Other drugs such as timolol, 7-methylxanthine and pirenzepine require more robust studies before they can be used with confidence.
3. In atypical cases of myopia such as this - due to the patient's age, pathological source of myopia and high level of myopia - myopia control strategies cannot be expected to work as demonstrated in scientific studies. Proceed with a focus on informed consent and educating the patient on the importance of ongoing ocular health monitoring.