Managing myopia in presbyopic adults

By age 21, around 90% of myopes having stopped progressing¹ and only 20% of adults progress by more than 1D across their 20s.² Hence, it is safe to assume the risk of myopia progression in your patient in their 40s or 50s is quite small. Even with a stable refraction, though, presbyopic myopes have their own management challenges.

It is well established that with longer axial lengths the risk of pathological myopic and health complications escalates dramatically, so ocular health monitoring is important. Additionally, there are special considerations when prescribing for high myopes, and binocular vision disorders can impact presbyopic prescribing choices. We'll explore all of this and more here.

Whilst children and teens are at the highest risk of dangerous axial length progression, adult myopia progression is not impossible. The most common associated risk factor with pre-presbyopic adult progression is excessive near work,² however this hasn't been studied in great detail. Our best efforts didn't turn up any scientific papers on myopia progression in presbyopic adults, except that due to ocular or systemic disease.

• Nuclear cataract can cause myopic shifts. In one study of adults with no other ocular or systemic health issues and a mean age of 67 years (range 50-83 years), a group with nuclear cataract progressed -0.37±0.60D over a mean of 44 months whilst a control group progressed +0.02±0.21D. Over 50% progressed by more than -0.40D.³
• Diabetes can cause myopic shifts. In adults at least 20 years of age, followed up after 10 years, those with younger age of onset (type 1) had more myopia than those with older-onset (type 2) of a similar age.⁴ Acute changes in blood glucose levels can shift refraction to either myopia or hyperopia;⁵ although upon intensive treatment, hyperopic shifts are common. One study found a hyperopic shift of up to 1.60D on commencement of glycaemic control in newly diagnosed diabetics, with a mean of a +0.50±3.20D shift.⁶  Once diabetes is managed, daily fluctuations in blood glucose levels do not appear to influence refraction.⁷

It was previously considered that undercorrection may be an option for myopia management. Despite evidence over the last two decades that undercorrection does not work, and may in fact worsen myopia progression,⁸ our adult myopes of today could have experienced this in their past. Undercorrection has the potential to exacerbate the insufficient accommodation behaviour found in myopes,⁹ which may lead to earlier or higher adds being required than expected for their age. There is no evidence that a higher add in the context of presbyopia is damaging, as long as it allows for an appropriate working distance that the person needs for leisure and work. Anecdotally, I have found my myopic patients often need near adds at a younger age than their emmetropic peers.

Myopes, especially those with low myopia, may tend towards self-treating presbyopia by simply removing their glasses. There is no evidence that this is harmful in older adults and in those lucky enough to have the right prescription, it is a simple solution. However for situations that demand multiple clear focal points, such as driving, looking at a phone while watching TV, or shopping, patients may quickly encounter barriers to removing their glasses. In this case, it can be a challenge explaining that progressive addition lenses (PALs) provide convenience despite the low myope still being able to remove the glasses to read.

Consider the ideal focal distance that the presbyopic myope (and maybe each of their eyes!) can view without their glasses, to help explain the need for PALs.

• -1.00DS unaided can see clearly to 1m: A computer screen on a large desk, full newspaper, dashboard on a car (but can't drive without the correction!)
• -2.00DS unaided can see clearly to 50cm: A book or smartphone held in their hands, a laptop pulled closer
• -3.00DS unaided can see clearly to 33cm: Still suitable for reading or smartphone use at a closer distance, unlikely to be comfortable for a laptop
• -4.00/-5.00DS unaided can see clearly to 25cm and 20cm respectively: May still be acceptable for viewing a smartphone, but unsustainable for most screen-based work environments.

The reality is the demands of the modern world are frequently too complex to be contained at one viewing distance, and patients can require multifocal and/or multiple lens solutions to comfortably fulfil all of their tasks. In fact, recent research has shown that PALs improve quality of life for both low (-0.50D to -4.99D) and high myopes (over 5D) compared to single vision correction. The beneficial effect was larger for high myopes, who twice as likely to be “afraid to do things because of their vision” and “frustrated with their glasses” in single vision compared to if they were wearing PALs.¹⁰

When prescribing contact lenses for the older myope, consider the demands on the binocular vision system. When observing the world through glasses the myopic lenses cause a base-in prism effect at near, decreasing vergence demand. By looking away from the optical centre, the wearer can also effectively reduce the power provided by the lens, reducing accommodative demand as well.¹¹

When fitted for contact lenses this optical effect is removed, leading to an earlier requirement for a near addition. Read more about this in Specs to Contacts – What Happens to BV. A common reason for contact lens wear drop out in presbyopia is poor vision,¹² so appropriate fitting and discussion of expectations in multifocal contact lens wear is needed - as is the case for myopes and non-myopes alike.

We spend a lot of time discussing how to approach the topic of myopic pathology with parents and children, but it is the presbyopic age groups that are suffering the consequences of myopic macular degeneration (MMD).

The frequency of pathological complications from myopia increases with age. A Taiwanese study demonstrated that low vision  prevalence amongst high myopes rose from 0.83% in 65-year-olds to 8.3% in those over 80,¹³ and a study in Singapore showed an exponential relationship between age, high spherical myopia and the prevalence of myopic maculopathy.¹⁴ Posterior staphylomas, a consequence of pathologic myopia, can be observed in younger patients but generally develop later in life.¹⁵

A study of 810 highly myopic eyes in 432 patients with a mean age of 42±17 years, myopia ranging from 5 to 37D and mean axial length of 28.8mm (range 24.2 to 34.3mm) found that 58.6% of all eyes developed myopic maculopathy. This means that at least half of your highly myopic patients will go on to develop retinal issues as a consequence of their myopia.¹⁶

The prevalence of MMD across all levels of myopia has been reported as 2.7% in 50-59 year olds, 4.8% in 60-69 year olds and 12.1% in those over 70 years. The risk increases with higher myopia, however age alone is an independent risk factor. Those with both increased axial length and older age show the highest risk of MMD.¹⁷ Myopes over 70 years have more than three times the rate of MMD than those aged 40-49.¹⁸

Retinal detachments are increasing in frequency, likely as a consequence of an increasingly myopic population.¹⁹ Detachment is more common in those over 50 years and those with high myopia.^19,20 Discuss the warning signs of flashes and floaters with myopic patients, and the importance of immediate presentation to an eye care practitioner.

Moderate myopia increases the risk of glaucoma by 1.8x, and high myopia increases the risk of glaucoma by 2.5x.²¹ Age is also a separate risk factor, with patients more than 17x more likely to be diagnosed with glaucoma when aged over 80.²² Consider also the fact that the myopic stretching of the optic nerve head can complicate diagnosis and visual field.²³

Cataracts are also more common in those that are older, and also those whom are more myopic.²⁴ Whilst a thorough examination of the crystalline lens should form part of a normal comprehensive examination, myopic patients may present earlier with cataracts than their emmetropic counterparts.

Ensuring the best possible optical correction is important for all myopes, and presbyopia can present challenges in this respect. Ultimately the best approach is to consider your patient's visual needs and history, to prescribe them a comfortable vision correction to which they can readily adapt.

Regarding ocular health, the International Myopia Institute Clinical Management Guidelines recommends retinal health examination in all myopes, and annually in high myopes through dilated pupils as indicated. Additional imaging with fundus photos and/or OCT is recommended if retinal findings are noted, or to objectively document retinal features. An important part of managing adult myopes is to explain that even with stable myopia, there is an ongoing requirement for ocular health examinations for early detection of any complications.

• Case study: How Should We Manage A Presbyopic Progressing Myope?

• Adult Myopia Progression and How to Treat It

• Case study: Upper age for myopia management

• Case study: Does pregnancy influence myopia?