At the completion of this article, the reader should be able to align their clinical protocols more closely to a best-practice approach to myopia intervention, including:
- Understand why axial length measurement is the gold standard for myopia management
- Understand the rationale and significance of accurate baseline measurements of refraction, keratometry, corneal topography and axial length in managing an adult with myopia
- Assess the treatment options for adults with myopia progression
What needs to be done when an adult presents with myopia? If the progression is due to axial elongation, many of the same treatments prescribed to children apply. As PHILIP CHENG explains, the higher vision demands of adults means objective, reliable metrics are key along with a proactive management plan.
B Optom (Melb) Therapeutics Endorsement
FIAOMC — Fellow of the International Academy of Orthokeratology & Myopia Control
Committee board member, Orthokeratology Society of Oceania
Eyecare Concepts – Myopia Clinic, Melbourne
Many of us come across these patients regularly in our practices: adults attending with complaints about their distance vision; patients of adult age being diagnosed with myopia for the first time; and those with myopia who continue show progression. It’s long been thought that children’s eyes stop growing and therefore should stop progressing by the time they turn 18. Is that true?
As our knowledge on myopia as an eye condition continues to expand with increasing research, it is becoming clearer that myopia may, in fact, continue to progress for patients well into the 20s. While genetics play a role in myopia development, the impact of the visual environment cannot be underestimated.
It’s well-established that in children, myopia onset and progression due to lifestyle changes during the COVID-19 pandemic increased. This has been confirmed by a recent review and meta-analysis of studies in relation to myopia progression during COVID vs pre-COVID.1 The myopic shifts observed is likely due to children spending less time outdoors, remote learning and increased screen time and near work.
A retrospective study on young adults with a mean age of 22.5 years found a statistically significant increase in myopia between pre-COVID and two years after the pandemic,2 indicating that myopia progression in adulthood can occur from changes in lifestyle as well.
Recently, findings from the Raine Study conducted on a cohort of adults in Western Australia found that more than one third of the subjects had myopia progression of 0.50D or more between 20 and 28 years of age.3 The study found that myopia onset also occurred in one of seven people who did not have myopia at age 20; women have a faster rate of myopia progression than men and higher risk of myopia onset as adults; and tertiary education, starting full-time work and digital device use are possible causes for myopic progression in adults in their 20s.
Further, the study is among the first to confirm that axial elongation occurs in adults with myopia progression by an average of 0.2 mm growth in the third decade of life – and as much as 1 mm in some subjects.
The implications of these findings are profound: myopia progression in adults cannot be assumed to be from accommodation or lenticular changes. When axial elongation is occurring in our adult patients, conversations need to be initiated to proactively managing the progression and reduce the ocular health risks – just as we would when a child presents with myopia.
Comprehensive adult myopia eye assessment
A myopia management assessment for any patient, child or adult, should start with a comprehensive vision and eye health examination. It’s important to measure refraction as accurately as possible, which might involve the use of cycloplegics. Although autorefractors are commonplace and handy as a starting point, care should be taken when using autorefraction results. It’s also easy to over-minus a patient’s refraction subjectively, which affects interpretation of progression.
Retinoscopy and binocular refraction can assist in determining an accurate refraction, aiming for the least-minus result for clear distance acuity. High myopia patients can be particularly challenging to refract, from the effects of vertex distance. Checking habitual acuity through existing spectacles and a quick over-refraction with flipper lenses can be a helpful guide to check that the new refraction makes sense.
The gold standard in myopia management
Refraction is the sum of all the optical components of the eye and its length. A myopic shift in refraction can be due to different factors, such as changes in corneal curvature, crystalline lens density, accommodation and axial length.
As interventions for myopia management are aimed at primarily slowing axial length changes, baseline axial length is arguably the most important measurement. Indeed, the ability to accurately measure axial length with optical biometry is the gold standard in myopia management. Axial length is an objective, repeatable and reliable metric to monitor axial elongation in myopia progression. Optical biometry is about eight to 10 times more sensitive at detecting and tracking progression than subjective refraction, and measurements unaffected by accommodation. Practitioners can use axial length changes to validate changes found in subjective refraction, where 0.1 mm increase in axial length approximately correlates to a 0.25D myopic shift.
Ocular health is an important part of an adult myopia eye assessment. Any level of myopia increases the lifetime risks of ocular diseases, such as glaucoma, myopic maculopathy, retinal tears, retinal detachment and cataract. Although high myopia carries the highest risks of ocular complications, even low and moderate myopia have considerable risks.4
Axial length also provides an indication an individual’s ocular health risks, as the risk of visual impairment is strongly related to eyes with longer axial length regardless of the refractive error. Eyes with axial length greater than 26 mm have a 25% lifetime risk of uncorrectable visual impairment, rising to a staggering 90% for eyes longer than 30 mm.5
Assessment and documentation of the optic discs and maculas, using retinal imaging and optical coherence tomography (OCT) may reveal subtle structural changes and help to assess changes over time. Patients with high myopia should have regular dilated fundus examination to check the health of their peripheral retina. Ultra widefield (UWF) imaging such as optomap, which can capture a 200-degree wide retinal image in a single shot, can be a very useful tool for screening and documenting peripheral retinal changes, such as asymptomatic atrophic holes and lattice degeneration, in patients with myopia and high myopia.
Adults with myopia seeking advice for myopia management are generally concerned about their eye health. Many present with already high myopia, worried about vision loss and hoping their myopia progression can be stopped. Providing great care means having the tools to look after these patients to the best of our ability, while giving them comfort and reassurance of their ocular health. Striving for the highest level of clinical care, our myopia clinic is equipped with a comprehensive suite of diagnostic technologies including the ZEISS IOLMaster and OCULUS Myopia Master optical biometers, OCT, visual fields, corneal topographers, Pentacam and Optos California UWF imaging.
Adult myopia progression treatment
While there are gaps in our knowledge in managing adult myopia progression, the same treatments that we prescribe for children could potentially apply, providing that progression is due to axial elongation which these interventions help modulate. These interventions include peripheral defocus spectacle lenses, dual-focus or multifocal contact lenses, orthokeratology (orthok), atropine and combination therapy. There are different considerations when prescribing these treatments to an adult compared to a child; it’s important to consider quality of vision as well as treatment effectiveness, due to the higher visual demands of an adult.
Spectacle lenses for adult myopia
There has been a rise in new spectacle lens designs marketed for myopia management in the recent times. Two of these, with robust data from randomised controlled trials involving children,6,7 are the HOYA MiyoSmart defocus incorporated multiple segments (DIMS) and Essilor Stellest highly aspherical lenslet (HAL) lenses.
In adults, we need to consider whether the optics of these defocus spectacle lenses may affect distance visual acuity, contrast sensitivity and glare sensitivity. A German study8 evaluating traffic safety of DIMS lenses on a group of 12 young adults (age 24-45) found that lenses did not show visual impairment that would be relevant to road safety and concluded the lenses to be safe for driving. (MiyoSmart and Stellest lenses are currently limited to polycarbonate material (1.59 index), limiting their use in high myopia prescriptions where lens thickness and cosmesis may be an important factor).
Contact lenses for adult myopia
Many adults with myopia already wear contact lenses and may prefer contact lenses over glasses. For those who are progressing, a switch from a single vision (SV) lens to a centre-distance multifocal design may be beneficial. The BLINK study9 demonstrated a dose-response where a higher add power (+2.50D) was more effective than a medium add power (+1.50D).
Care should be taken to advise patients of the difference in quality of vision if they are currently wearing SV lenses. The consideration in prescribing these lenses to adults is the impact on distance acuity with the higher add powers. The aim is to give highest tolerable add power; if +2.50D add is too difficult to wear, reducing the add to a more tolerable level (+2.00D or +1.50D) might be necessary. Distance acuity may also be improved by increasing the distance spherical power by -0.50D to offset the effect of the add power.
Orthokeratology for adult myopia
Orthok is an option for adults who wish to enjoy the freedom of not needing to wear glasses or contact lenses in the daytime. Suitable adult candidates for orthok are those with low- to-moderate myopia, regular sleeping patterns, good compliance to wearing their lenses and hygiene, and flexible with some slight variation in vision from day-to-day.
Some adults may consider orthok as an alternative to refractive surgery, or have intolerance to dryness from soft lenses, or have heard about orthok for myopia management. Managing patient expectations is vital for successfully fitting an adult with orthok; patients should be advised that they are likely to experience halos and starburst effects at night, and reduced contrast sensitivity in low light situations as the pupils enlarge. These visual effects are related to the higher-order aberrations induced in the corneal reshaping process and increases with the amount of myopia correction; they also occur in laser refractive surgery.
Orthok is a highly effective treatment in slowing axial elongation in children. Recent work in orthok research has suggested that customising lenses with smaller back optic zone diameters (BOZD) may enhance the therapeutic effect in retarding axial elongation compared to conventional designs.10 However, such an aggressive myopia control orthok design could be difficult for an adult to adapt to. Adult orthok lenses are generally designed with larger BOZD of 6 mm or greater to enlarge the central treatment zone and reduce the effects of night halos.
For an adult proceeding with orthok with myopia management in mind, there should be lens design considerations for myopia control as well as providing satisfactory quality of vision for the patient’s lifestyle and visual tasks. Adults with near esophoria and accommodative lag may also benefit from the exophoric shift and improved binocular vision that OK lenses can provide, compared to single vision contact lenses.11
Low-dose atropine is less often used for adults, the mild cycloplegic effect of atropine is likely to be more pronounced for an adult with less active accommodation than a child, making the stronger, more effective doses (0.025-0.05%) more difficult to tolerate. For adults who may be interested in trying low-dose atropine, the commercially available Eikance 0.01% could be a starting point to assess tolerance.
Case study 1
A 22-year-old woman was referred for management of her adult myopia progression. The referral letter reported that “her prescription had steadily increased over the years and in the last 12 months, she has had more than -1.00D myopic shift in her left eye”. Her refraction was reported as R -6.00/-2.75×11 and L -6.75/-2.75×167, while her current glasses measured R -5.50/-2.75×6 L -5.50/-2.75×163. She alternates between her single-vision glasses and monthly-replacement soft contact lenses.
A cycloplegic examination was performed, finding a refraction of R -6.00/-2.75×6 and L -6.50/-2.75×160. Her axial length measured R 24.78 mm L 25.07 mm with the IOLMaster 500 optical biometer. She has steeper-than-average corneas, with keratometry readings of R 7.38 mm and L 7.34 mm along the flat meridian. Corneal topography is part of our initial assessment for myopia management, both to assess for patient suitability for orthokeratology and also as a screening for keratoconus. Given this patient’s moderate astigmatism and steep corneas, it was important to exclude the possibility of corneal ectasia causing her refractive changes. Her corneal topography showed regular, with-the-rule corneal astigmatism not suggestive of keratoconus. Her ocular health examination was unremarkable.
The patient was concerned about her myopia and was keen to explore options to slow her progression. We discussed management options including spectacle lenses, soft contact lenses and orthok. While orthok is a possibility, it could be a challenging fit and as a patient was already a happy soft lens wearer, we decided to start intervention with multifocal contact lenses. She was fitted with CooperVision Biofinity Multifocal toric lenses, centre-distance design with a +2.00D add. After three weeks, she had adapted well to her lenses and felt comfortable with her corrected vision of R 6/6 L 6/7.
After 12 months of treatment with multifocal contact lenses, her myopia had not progressed. She reported good compliance wearing her lenses daily, although she needed lubricating eye drops for end-of-day dry eye symptoms. Her subjective refraction was stable, and her axial length of R 24.81 mm L 25.05 mm confirmed no axial elongation in the past year. She was pleased with the result and was happy to continue myopia management wearing multifocal contact lenses.
Case study 2
A 21-year-old university medical student from regional NSW booked into our clinic for orthokeratology assessment. With concerns for her high myopia, she had been researching myopia management options for herself. She started wearing glasses from age eight and had year-by-year progression. She previously tried multifocal contact lenses but stopped due to dry eye. Her refraction measured R -5.50 and L -6.25/-0.25×45, axial length R 24.64 mm L 24.95 mm and keratometry readings R 7.54 mm L 7.50 mm and relatively spherical corneas on topography.
Following her detailed myopia assessment, we discussed her options for adult myopia management. While she understood that her myopia may not progress as quickly as it did when she was younger, she wanted to be proactive to prevent further deterioration of her vision. She was particularly interested in orthok for the benefit of myopia control as well as being free from wearing glasses or daytime contact lenses. It was important to advise her of vision expectations of orthokeratology for her high myopia: the likelihood of night halos from aberrations, the need for good sleeping patterns and lens hygiene. And, with her long travel distance from the clinic, she had to understand that multiple visits for her ongoing reviews would be required, particularly in the first few months of starting orthok treatment. With her informed consent, we proceeded to start her on orthok, using custom-designed EyeSpace Forge OK lenses.
She stayed overnight in Melbourne for her orthok lens fitting and day one review, then attended subsequent reviews at three weeks and at three months. She has been very happy with her treatment; she wears her lenses nightly for seven to eight hours, enjoys full correction of her myopia and unaided VA of 6/6 R&L. Her corneas are healthy, without any staining. She reported no issues with halos at night and her eyes feel more comfortable than she wore soft daytime lenses. Although it is too early to assess progression at this point, her axial length measured R 24.53 mm L 24.88 mm at three months and will be reviewed again four months later.
There is now sufficient evidence that myopia onset and progression can occur in adulthood. Just as myopia management in children is important and is gradually moving towards being a standard of care in optometry, we should not forget about the adults with myopia who may also progress. Establishing an accurate baseline with reliable refraction, keratometry, corneal topography and axial length will help with clinical decision making in managing an adult with myopia.
Management options should be guided by patient expectations, visual demands, lifestyle and personal preferences. Patient education of the lifelong risks of myopia and regular comprehensive ocular health examination are important aspects of managing adult patients whether they are still progressing or stable in their myopia.