Is it really fast progressing myopia, or something else?

In our digital age, our near work demands have become increasingly intense. Prolonged near work can trigger myopia as well as pseudomyopia.¹ This post in the Myopia Profile Facebook group discusses a 14-year-old girl whose fast progressive high myopia is not as it seems. How does one appropriately detect and manage a complex case like this, and how can corneal curvature and axial length measurements help?

In a patient who turns out to be non-myopic, we would call this pseudomyopia;¹ technically it's not 'psuedo' in this case when we have some definite manifest myopia. This over-correction of myopia, while it differs in refractive endpoint to pseudomyopia, is likely due to the same origin of accommodative spasm. Here were the clues to the diagnosis:

1. The change in refractive error: The change in subjective refractive error over six months amounts to around 2.75D and 3.25D of myopia progression in the right and left eye respectively. This rate of progression far exceeds what is expected for her age in a single vision correction (-0.63D per year).²
2. Axial length: at less than 23mm, it is highly unlikely that she is a high myope.
3. Corneal curvature: a relatively average flat K of around 43D.

When put together, the axial length and corneal curvature especially do not indicate high myopia in either eye. To have such high myopia with low axial length, the corneal curvature would have to be very steep. The apparent fast progression is also highly unusual. These clues suggest that the progressive myopia may not be what it seems and cycloplegic refraction is necessary.

Accommodative spasm is a binocular vision dysfunction resulting in a variable and over-minussed refraction. The terminology 'spasm of near reflex (SNR)' describes clinical signs of fluctuations in visual acuity, vacillating retinoscopy reflex, accommodative lead in dynamic retinoscopy, and symptoms of blurred vision and asthenopia. Causes can be organic (such as head trauma), psychogenic or potentially environmental, related to excessive near work, and it may occur with or without over-convergence (esophoria/tropia).³ Treatment for accommodative spasm involves relaxing and/or inhibiting the excessive accommodative tone.

Option 1: In-office optical fogging. There are two publications mentioning an 'optical fogging technique' which provided some instantaneous relief and even resolution in some cases of SNR. Refraction post-fogging was also found comparable to cycloplegia.³ This technique involved sustained reading with a high add for 30 minutes; then slowly reducing the plus at distance to achieve maximum plus refraction; then testing the limits of accommodation activation (clearing minus) and deactivation (clearing plus) at near. This was supported by at-home training with plus/minus lens flippers used monocularly and binocularly in one case series⁴ and in another larger study, was used on repeated visits to resolve what the authors termed 'mild' cases of SNR. Less responsive cases were prescribed atropine 1% one a week for a month before next follow up.

Option 2: Cycloplegic eye drops with supportive optical correction. A published case series of four patients aged 11-13 years used 1% atropine twice weekly for accommodative spasm. Bifocal spectacle lenses were prescribed with up to +3.00 Add. Treatment was tapered every month over 3 months and followed up for 6 months with no evidence of recurrence.⁵ Other authors have also presented case studies or series where cycloplegic agents were used.^6,7

Prescribing the cycloplegic refraction result is not suitable as the patient will suffer reduced acuity and functional impairment. The refraction is ideally a balance between what provides functional vision and the minimum minus power required to achieve that, ideally reducing the minus power with time. Contact lenses can provide a simple and cost-effective method to slowly reduce this patient's prescription over time.

A near add will be necessary if using a cycloplegic agent, so if wearing contact lenses, additional bifocal or progressive spectacles will be required. A patient undergoing cycloplegic treatment may also need photochromatic spectacles.

If you're a primary eye care practitioner without access to cycloplegic agents for refraction, how can you manage this case? Firstly, read more on the 'when' and 'how' of cycloplegia, and how to manage without it, in How To Achieve Accurate Refractions For Children. Secondly, complex cases such as this may need co-management with paediatric ophthalmology - you will know best as relevant to your scope of practice.

Firstly, the extremely fast progression which appears to be in the order of 3D in six months, or around 6D in one year, is highly unusual and should trigger suspicion.

Secondly, when faced with a presumed high myope, the main ocular component which usually (but not always) contributes to high myopia is a long axial length, where 5-6D of myopia is typically correlated with around 26mm of axial length.⁸

If this is not the case, then a steeper-than-average cornea would be suspected. Measuring corneal curvature in progressive myopia is important to rule out steepening due to keratoconus, as typically corneal curvature⁹ and astigmatism^10,11 is relatively stable in progressing myopia. Read more about this in Measuring the Whole Eye in Myopia.

1. Myopia shouldn't progress by a few dioptres in six months. Consider accommodative spasm where very fast progression appears to have occurred, and employ a cycloplegic refraction.
2. Make sure the ocular components add up - high myopia typically presents with a longer axial length, and corneal curvature is usually stable in progressive myopia. If either of these conditions are not met, further investigations are necessary.