Introduction
Myopia or nearsightedness is caused by inaccurate light rays to be perceived on the retina [1–3]. It is a frequent refractive error case where distant things look blurred, but close items are seen [4]. In myopia, the focal point of the refractive media system is located in front of the macula lutea. It has been classified into three degrees of disease, including high, moderate, and low myopia [5].
Myopia has become a significant global public health issue, especially in East Asia [6]. By 2050, the estimated myopia prevalence will be about 49.8% of the worldwide population, especially at productive ages between 20 and 45 years [7, 8]. Myopia is caused by two main factors: morphological abnormalities in the cornea or lens and elongation of the axial line of the eye [9–11]. However, environmental effects and daily behaviors such as reading habits, prolonged use of gadgets, and some activities that require high access to visual contacts, such as a microscopist, can also be a risk of causing myopia [12, 13].
Several studies have been conducted to prevent myopia progression. Increasing outdoor activities, using concave lenses, and performing LASIK surgery was the most established treatment method [14, 15]. Besides, new therapeutic options such as spectacles lenses and orthokeratology significantly affected myopia improvement [16]. However, this therapy method must be adjusted based on the patient’s age, the degree of myopia, and the final goal of correction to consider the patients’ benefit and prognosis [2, 17].
This literature review compares two non-operative treatment options in myopia cases, especially spectacles lens glasses and orthokeratology therapy. In this paper, the advantages and disadvantages of each treatment will be presented to provide information for patients in selecting the appropriate type of myopia management.
The literature search in this review was carried out using Pubmed and Google Scholar databases with three main keywords: myopia, spectacles lens, and orthokeratology. The articles were selected based on language, type of publication, suitability of methods, subject characteristics, exposure, and outcome. All references that match the inclusion criteria are processed using the Mendeley® citation manager, whereas 53 articles are obtained as references.
Myopia
Myopia is a disorder induced by the elongation of the eyeball and increased curvature of the cornea, which results in parallel light rays entering the eye failing to concentrate in front of the retina, rendering distant objects incorrect [18, 19]. Several risk factors for myopia have been discovered, including genetic factors, less time outside, longer near work, a shorter reading distance, and a positive family history of myopia. Myopia is most frequently shown by a reduction in the visual distance [8].
Myopia can be detected by examination of visual acuity with the Snellen chart and fundoscopic examination [20]. Myopia is related to the development of major pathological disorders such as macular degeneration, retinal detachment, glaucoma, and cataracts; therefore, efforts to control myopia progression have recently intensified [21]. Several methods have been made, such as increasing outdoor activities, topical atropine, concave lenses, perifocal lens glasses, orthokeratology therapy, and Laser-assisted in situ keratomileuses (LASIK) surgery [22, 23].
Patients with early-onset and severe myopia have a worse long-term visual acuity prognosis [24]. Moreover, patients with longer axial lengths have a faster rate of myopia progression and a higher risk of developing myopic retinal degeneration, choroidal thickness, and other related diseases [20, 25–27].
Spectacles lens
The lens and the cornea are the primary refractive components of the human eye. We optimize the visual system with a new refractive component by wearing an ophthalmic lens to rectify a refractive problem. Lensometers are used to determine the unique properties of every type of spectacles lens. Numerous methods and techniques are available to improve the capability and function of ophthalmic equipment, including the focimeter, lateral shear interferometer, point diffraction interferometer, Newton interferometer, Twyman-Green interferometer, Talbot interferometry, Moiré deflectometry, Hartmann test, Ronchi test, and Fringe reflection test [28].
In the past, most spectacles’ lenses were constructed of glass. Today, most spectacles are constructed from various sophisticated polymers, and most sight lenses are composed of polycarbonate. These new lenses are lighter, scratch-resistant, and less likely to break than glass. They can also be coated with a filter to protect the eyes from ultraviolet exposure [29]. Blue-light-filtering spectacles lenses can significantly filter out a portion of high-energy short-wavelength light without impairing visual performance or sleep quality. These lenses may be used to protect the retina from specific blue-light hazards [30].
The ophthalmic lens design is concerned with correcting aberrations in spectacles lenses caused by the eye rotating away from the optical center of the lens. A study by Hanna et al. (2019) showed that lens decentration occurs in spectacles lens users, resulting in induced prismatic effect and subsequent vision impairments such as asthenopia or diplopia in the future [31]. Oblique astigmatism and mean oblique error are the most prominent aberrations (power error). The goal of distant vision spectacles lens design is to provide point views of far area features on the far point sphere. Today’s best-form lens series is built to be tangential error-free when fitted at an average vertex distance. When lenses with a low T-error-form are fitted at a larger vertex distance than usual, they function similarly to point-focal lenses [32].
On the other side, perifocal lenses are a relatively new technology that may be used to correct the refraction of light or slow myopia’s growth. Lens designs aimed at lowering hyperopia even induce relative myopia in the retina’s periphery, resulting in clear vision in the fovea [33]. Perifocal lenses facilitate refraction of the eye’s center and periphery along the horizontal meridian. This lens provides greater positive power in the periphery lens than in the central lens, resulting in a significantly clearer visual distance. Additionally, this lens has an aperture that is clear in the center with a length of approximately 10 mm on both sides center along the horizontal meridian with the same distance to the lower section enabling clear vision at sight to lower. After 4-5 years of therapy, patients with a mean of –0.38 0.04 D and as high as –1.16 0.20 D might exhibit repair strength refraction after wearing the perifocal lens for 12–18 months [34, 35].
Some work analyzes the efficacy of highly aspherical lenslets (HAL) and slightly aspherical lenslets (SAL). Both lenses feature a spherical front surface surrounded by 11 concentric rings produced by continuous aspherical lenslets (diameter of 1.1 mm). The lens region that is not covered by lenslets corrects for distance. At any eccentricity, the geometry of the aspherical lens is expected to produce the myopic defocused volume (VoMD) in front of the retina, which acts as a myopia control signal. Additionally, based on optical modeling, HAL caused a bigger VoMD in front of the retina than SAL; hence, we hypothesize that a larger VoMD will be more successful in reversing myopia development [36].
Spectacles lens with a specific design (perifocal lens) demonstrates the potential benefit of constant and gradual improvement of refraction. However, the use of this therapy shows a longer correction time. Therefore, this therapeutic option tends to be more recommended as an optical tool to slow the development and progression of myopia patients [37].
Orthokeratology therapy
Orthokeratology is a non-invasive technique specially designed as a compatible contact lens to temporarily reshape the cornea to improve vision. Orthokeratology-induced peripheral myopic defocus is the primary mechanism responsible for halting myopia progression in patients undergoing orthokeratology therapy. Wearing orthokeratology lenses overnight also flattens the central zone of the cornea and increases the relative corneal refractive power (RCRP). The pattern of RCRP causes myopic peripheral defocus of the retina, which is known to be one of the mechanisms of action of orthokeratology lenses in which the causes, as mentioned earlier, a further slowing of the axial length of the eye [38, 39].
Orthokeratology lenses are made of plastic, have a strong texture, and better strength than soft lenses, which tend to tear easily [40]. Unfortunately, if the user stops using orthokeratology lenses, the cornea could be returned to its original shape within a few days [41]. Orthokeratology has developed into a clinically proven and effective procedure for correcting refractive problems [42]. It utilizes hard materials to ensure the best oxygen transmission rate and is worn at night to reduce and control myopia [43]. Orthokeratology involves flattening the cornea to decrease the eye’s total refractive power. The corneal structural alterations are caused by a thickening of the mid-periphery and a thinning of the central cornea [44].
Myopia development’s most commonly understood explanation focuses on refractive alterations outside the macula [45]. Myopia prevalence has increased between 10% and 25% in young adolescents and 60–80% in industrialized communities in West and East Asia. Over the last several decades, there have been indications that gas-permeable contact lenses can help children’s myopia development [46].
Orthokeratology provides patients with a unique factor and eliminates the daily wearing of contact lenses or glasses [47]. Visual acuity is quite good, with the majority achieving 20/20 and over 90% achieving 20/30. The most significant complaints found with OK are halos secondary to the spherical aberration [48].
Orthokeratology is a pain-free, child-safe, and reversible procedure [49]. It supports visual acuity by designing simply inserted and precisely fitted lenses into the eyes; this also proved a safe and efficient procedure that can cure nearsightedness, farsightedness, astigmatism, and presbyopia.[50]. It is an excellent option rather than LASIK for individuals who do not prefer to take the risk or are not physically prepared for surgery. The risk is significantly reduced by following a strict lens washing and disinfection regimen and wearing the lenses as advised [51, 52].
Three classical patterns may be observed to evaluate the lens outcome when a difference map is formed between the initial corneal topography and the newly created corneal topography behind the orthokeratology lens [16]. Orthokeratology requires a tool that measures corneal topography. Using the sagittal corneal height and the corneal shape can better predict the amount of ametropia that can be corrected and, therefore, what initial lens is ordered. Finally, it may be used to track the effect of the lens on the eye and refine the lens fit. A center flat region is intended, encircled by a ring of relative steepening. Orthokeratology treatment also needs frequent lens care since it can cause irritation, inflammation, and infection [40, 43, 53].
Conclusion
Spectacles lenses and orthokeratology have some benefits and limitations in preventing myopia progression. Therapy selection must continue to be individualized for each patient to enhance recovery outcomes.
Acknowledgment
The authors would like to thank Medical Youth Research Club (MYRC) for their support in writing this article.
Funding
None declared.
Conflict of interest
The authors declare that there is no conflict of interest.