Higher Levels Of Myopia Research Articles

LASIK Versus PRK Based on Increased Risk of Corneal Haze: Assessing Current Decision-Making Capabilities of Six Artificial Intelligence Models in Refractive Surgery.

To investigate the current decision-making capabilities of 6 different artificial intelligence (AI) models by assessing their refractive surgery recommendations (laser in-situ keratomileusis [LASIK] or photorefractive keratectomy [PRK]) for a theoretical patient with a history of keloid formation. Claude-2 (Anthropic, 2023), GPT-4 (OpenAI, 2023), GPT-3.5 (OpenAI, 2022), Gemini 1.0 (Google DeepMind, 2023), Microsoft Copilot (Microsoft AI, 2023), and Google-PaLM (Google AI, 2022) underwent three systematic queries to determine the most appropriate surgical plan (LASIK or PRK) for a theoretical patient with an increasing manifest refraction of -3.50, -5.00, and -7.00 diopters (D) in both eyes, an uncomplicated ocular examination, and history of keloid formation. They were then tasked with providing published scientific references to support their responses. The AI models' recommendations were compared to those of a group of 6 experienced ophthalmologists, serving as a benchmark. The group of ophthalmologists unanimously recommended LASIK (6/6 ophthalmologists), in contrast to the unanimous initial recommendation for PRK from the AI models (6/6 models). Of the 42 references provided by the AI models, 55% were fictitious and 45% were authentic. Only 1 of the 6 models altered its initial recommendation to LASIK when presented with the same patient with a history of keloid formation but with increasing severity of myopia (-3.50 to 5.00 to 7.00 D). It is evident that current AI models lack the critical-thinking abilities required to accurately analyze and assess apparent risk factors in clinical scenarios, such as the risk of corneal haze after PRK at higher levels of myopia, particularly in cases with a history of keloid formation. [J Refract Surg. 2024;40(8):e533-e538.].

Analysis of Treatment Discontinuation in Orthokeratology: Studying Efficacy, Safety, and Patient Adherence Over Six Months.

This study aimed to evaluate the efficacy, safety, and participant compliance of orthokeratology treatment for the correction of myopic refractive errors over a six-month prospective study and to define the potential reasons for early treatment discontinuation. A total of 32 participants with low-to-moderate myopia were fitted with the spherical model of corneal refractive therapy (CRT) orthokeratology lenses (Paragon Vision Sciences) and followed over six months, with specific attention to alterations in refractive error, corneal topography, and epithelial thickness. Concurrently, participant feedback and reasons for any treatment discontinuation were documented. Significant changes in refractive error and in corneal topography were observed, with approximately 50% of the refractive error being corrected on the first night of use and 100% by the first two weeks ( P <0.001). Central epithelial thickness experienced substantial thinning, reducing to 15.65±4.49 μm (67.38%) ( P <0.001) after 6 months of lens use. Six participants withdrew from this study for varied reasons, including unmet visual expectations and difficulty adhering to the lens-wearing regimen. Notably, the dropout group exhibited higher baseline low-order aberrations and less prolate corneas than those who persisted with the treatment ( P <0.05). Orthokeratology with CRT is efficacious and safe for the correction of low-to-moderate myopia in adults, but a portion of patients discontinue the treatment in the first 6 months of contact lens wear. Special care should be taken when recommending orthokeratology in patients with higher levels of myopia and corneas with less prolate shape, providing more realistic expectations and even changing to dual axis or more sophisticated designs.

Myopia: An ounce of prevention is worth a pound of cure.

Myopia severity has a profound impact on visual impairment in later life. A patient's final level of myopia may be lowered by myopia control, but also by delaying onset. Here, we evaluate the influence of the age of onset on the final recorded level of myopia. Data were extracted from: (1) Three prospective cohort studies of myopia progression in East Asia and the United States where the final recorded level of myopia is presented as a function of the established age of onset. (2) Four retrospective studies of myopia progression in Finland, India, the Netherlands and China and two cross-sectional studies in Argentina and the UK where the age of onset was based on self-report of age at first spectacle prescription. (3) A cohort study of Finnish subjects originally recruited for a clinical trial and followed into adulthood. Subjects were divided into five groups according to age at recruitment that was used as a surrogate for the age of onset. Final recorded level of myopia was plotted as a function of age of onset for all studies. Among the three East Asian studies, the slopes are between 0.68 and 0.97 D/year, meaning that each later year of onset is associated with between 0.68 and 0.97 less myopia at the final recorded refraction. For six of the seven non-East Asian studies, the slopes are substantially flatter, with slopes between 0.23 and 0.50 D/year. By contrast, the slope for the Finnish study was 0.87 D/year. Increasing age of final recorded refraction tended to be associated with higher levels of myopia. Among East Asians, delaying the onset of myopia by 1 year has the potential to lower the final myopia level by 0.75 D or more-equivalent to 2-3 years of myopia control with existing modalities. The benefit is lower, but meaningful, among non-East Asians.

Myopiekontrolle: aktuelle Strategien

Purpose. The prevalence of myopia is increasing worldwide and its long-term effects can have major impacts on eye health. Paediatric onset of myopia leads to a higher risk for developing high levels of myopia in adulthood. Slowing down or stopping myopia progression is an important task for the future. Material and Methods. Based on a literature review, the latest developments in the field of myopia control for children were summarized. The current study situation for orthokeratology, soft contact lenses, atropine therapy and spectacle lenses for the management of myopia is discussed in detail. Results. Results on the safety and effectiveness of orthokeratology and modified soft contact lenses are exceedingly consistent. Soft multifocal contact lenses, as well as newer spectacle lenses, recently received regulatory approval for myopia control. Studies on the administration of atropine recommend a dosage of 0.01 - 0.05 %. All methods slow down myopia progression and decrease axial length growth of the eye. Side effects, adverse events or discontinuation of treatment only occur in the rarest of cases. Orthokeratology and atropine continue to deliver the best results. Conclusion. From today’s perspective, carrying out myopia control can be recommended with great certainty. The choice of method depends on the individual requirements of each patient, with all methods offering success in reducing myopia progression. In the future, even more advanced contact lens geometries, more precise atropine dosages or improved optics of spectacle lenses will further increase the success of the treatment. Keywords. Progressive myopia, myopia control, children, contact lenses, atropine, spectacle lenses

Ocular biometric parameters of children with refractive errors in the age group of 6–15 years

Background: Refractive errors are one of the leading causes of visual impairment in children. Studies on the association between refractive errors and ocular biometrics have shown inconclusive results; hence, this study aims to examine this relationship. Objectives: The objective of this study is to investigate the association between ocular biometrics such as axial length (AL), anterior chamber depth (ACD), lens thickness, vitreous chamber depth (VCD), and corneal curvature (CC) with different refractive errors in children aged 6–15 years. Materials and Methods: This was a cross-sectional study and studied 130 eyes of children. Children with congenital and acquired anterior or posterior segment diseases were excluded. All underwent detailed ocular examination, visual acuity measurement, and cyclopegic refraction. Children were divided into emmetropia, myopia, and hypermetropia. Ocular biometrics measured using A-scan and automated keratometer. Results: AL, ACD, and VCD significantly increased in the higher levels of myopia (P ≤ 0.0001), (P = 0.04), and (P ≤ 0.0001), respectively, whereas hypermetropes had the lowest. Spherical equivalence was significantly correlated with AL in myopes (ρ= −0.624; P

Biological effects of mitomycin C on late corneal haze stromal fibrosis following PRK

This review details the current understanding of the mechanism of action and corneal effects of mitomycin C (MMC) for prophylactic prevention of stromal fibrosis after photorefractive keratectomy (PRK), and includes discussion of available information on dosage and exposure time recommended for MMC during PRK. MMC is an alkylating agent, with DNA-crosslinking activity, that inhibits DNA replication and cellular proliferation. It acts as a pro-drug and requires reduction in the tissue to be converted to an active agent capable of DNA alkylation. Although MMC augments the early keratocyte apoptosis wave in the anterior corneal stroma, its most important effect responsible for inhibition of fibrosis in surface ablation procedures such as PRK is via the inhibition of mitosis of myofibroblast precursor cells during the first few weeks after PRK. MMC use is especially useful when treating eyes with higher levels of myopia (≥approximately 6 D), which have shown higher risk of developing fibrosis (also clinically termed late haze). Studies have supported the use of MMC at a concentration of 0.02%, rather than lower doses (such as 0.01% or 0.002%), for optimal reduction of fibrosis after PRK. Exposure times for 0.02% MMC longer than 40 s may be beneficial for moderate to high myopia (≥6D), but shorter exposures times appear to be equally effective for lower levels of myopia. Although MMC treatment may also be beneficial in preventing fibrosis after PRK treatments for hyperopia and astigmatism, more studies are needed. Thus, despite the clinical use of MMC after PRK for nearly twenty years—with limited evidence of harmful effects in the cornea—many decades of experience will be needed to exclude late long-term effects that could be noted after MMC treatment.

We can't afford to turn a blind eye to myopia.

Myopia is becoming increasingly prevalent throughout the world. It is an overlooked but leading cause of blindness, particularly among the working aged population. Myopia is often considered benign because it is easily corrected with glasses, contact lenses, or refractive surgery. Traditionally myopia has been classified into physiological and pathological subtypes based on the degree of myopia present. Higher levels of myopia are associated with increased risk of pathological complications but it is important to note that there is no safe level of myopia. Even low levels of myopia increase the risk of retinal detachment and other ocular comorbidities which will be discussed in detail later. The most serious complication, myopic maculopathy, is the only leading cause of blindness without an established treatment and therefore leads to inevitable loss of vision in some myopes, even at a young age. To highlight the current myopia epidemic and the sight threatening complications associated with it. This is a comissioned review article. Data was gathered by performing a literature review, searching the PubMed database for recent articles regarding myopia. Myopia is a potentially blinding disease. By identifying at risk individuals and intervening before they become myopic, eye care practitioners can prevent or delay spectacle use, reduce the risk of the myriad of myopic complications and thereby improve the patient's quality of life and positively impact its socio-economic effects.

Assessment of Clinical Trials for Devices Intended to Control Myopia Progression in Children

The increased prevalence of myopia in the United States and other regions of the world, and the sight-threatening problems associated with higher levels of myopia have led to great interest in research designed to reduce these rates. As most of the progression of myopia occurs in childhood, these investigations have been directed toward slowing the progression of myopia in children. Treatments described to potentially slow the progression of myopia have included pharmacological interventions, multifocal spectacles, and multifocal correction created by contact lenses. Although some contact lens clinical trials have demonstrated promising results in slowing the progression of myopia, many of these studies have significant limitations, including only short follow-up times, limited randomization, and incomplete masking. Such limitations have underscored the need to develop a more robust clinical study design, so that future studies can demonstrate whether contact lenses, as well as other medical devices, can be used in a safe and effective manner to control myopia progression. We review previous key studies and discuss study design and regulatory issues relevant to future clinical trials.

Meta-analysis and review: effectiveness, safety, and central port design of the intraocular collamer lens.

The purpose of this review is to summarize relevant data from publications appearing in the peer-reviewed scientific literature over the past decade since US Food and Drug Administration approval of the implantable collamer lens (ICL), and, in particular, to review studies relating to sizing methodology, safety, and effectiveness, as well as more recent studies reporting clinical outcomes of the V4c Visian ICL with KS Aquaport, VICMO. A literature search was conducted using two databases, PubMed.gov and Science.gov, to identify all articles published after 2005 related to the Visian ICL (STAAR Surgical, Inc.). Articles were examined for their relevance to sizing methodology, clinical safety, and effectiveness, and the references cited in each article were also searched for additional relevant publications. The literature review revealed that all currently reported methods of determining the best-fit size of the ICL achieve similarly satisfactory results in terms of vault, the safe distance between the crystalline lens and the ICL. Specifically, meta-analysis demonstrated that sulcus-to-sulcus and white-to-white measurement-based sizing methods do not result in clinically meaningful nor statistically significant differences in vault (two-sample two-sided t-test using pooled mean and standard deviations; t (2,594)=1.33; P=0.18). The reported rates of complications related to vault are very low, except in two case series where additional risk factors such as higher levels of myopia and older age impacted the incidence of cataract. On the basis of preclinical studies and initial clinical reports, with up to 5 years of follow-up, the new VICMO central port design holds promise for further reduction of complications. Given its safety record and the significant improvement in vision and quality of life that the ICL makes possible, the benefits of ICL implantation outweigh the risks.

Comparison of Keratometric Changes After Myopic Ablation: Ray Tracing Versus Simulated Keratometry

To compare the changes in corneal power (ΔK) induced by myopic ablations estimated by Placido-disk and total corneal power (TCP) ray tracing methods to the refractive change (ΔSE). Manifest refraction, simulated keratometry from a Placido-disk based system, and TCP from a dual-Scheimpflug analyzer were obtained from 35 patients (58 eyes) before and 3 months after a myopic ablation. The change in the manifest refraction that occurred after surgery was then vertex distance corrected and compared to the changes observed in corneal power with the various systems analyzed. The Placido-based simulated keratometry overestimated the corneal power after the procedure by 0.50 ± 0.53 diopters (D) when compared to refractive change in the corneal plane induced by the laser surgery (ΔSE-ΔK). The ray tracing method showed the opposite trend, with the TCP simulated keratometry showing an underestimation of the corneal power of -0.25 ± 0.48 D. The Placido system showed a direct correlation between the overestimation of the corneal power and the level of myopia, whereas the ray tracing method showed an underestimation, which was more pronounced in higher levels of myopia. Ray tracing methods underestimate corneal power as opposed to the overestimation in corneal power after refractive surgery, directly related to the level of myopia, observed in Placido-based systems. They have the potential to overcome the errors in calculations based on anterior curvature alone. However, ray tracing methods need to be validated and optimized before it can be used routinely in IOL calculation.

Corneal Higher Order Aberrations After LASIK for High Myopia With a Fast Repetition Rate Excimer Laser, Optimized Ablation Profile, and Femtosecond Laser–assisted Flap

To evaluate corneal higher order aberrations (HOAs) after LASIK for the correction of high myopia using a new generation of excimer laser (500-Hz repetition rate) and optimized ablation profiles. Retrospective consecutive study including 29 eyes from 17 patients (age range: 24 to 61 years) with high levels of myopia (spherical equivalent refraction ≥8.50 diopters). All cases underwent LASIK using the sixth-generation Amaris (SCHWIND eye-tech-solutions) excimer laser and flap creation with the IntraLase (Abbott Medical Optics) femtosecond laser. Postoperative changes in corneal HOAs and corneal asphericity were analyzed during 6-month follow-up. Significant improvement in uncorrected distance visual acuity and spherical equivalent was observed (P<.01). Corrected distance visual acuity did not change after surgery (P=.37). Significant increases in corneal root-mean-square (RMS) HOA, RMS spherical aberration (SA), and RMS coma were observed 6 months after surgery (P<.01). Corneal asphericity for the 4.5-mm (Q45) and 8-mm (Q8) corneal diameter also increased significantly during the postoperative period (P<.01). Significant correlations were found between postoperative RMS HOA and RMS SA and RMS coma (r(2)=0.375, P=0.000 and r(2)=0.596, P=.000, respectively). Linear regression analysis showed a significant relationship between postoperative Q45 and preoperative pachymetry and treatment optical zone (R(2)=0.24, P<.05). A correlation was also found between postoperative Q8 and preoperative sphere and treatment ablation zone (R(2)=0.459, P<.006). A significant induction of corneal HOAs still exists with the latest generation Schwind excimer laser. Linear regression analysis will help predict postoperative asphericity obtained when using LASIK for the correction of high myopia.

Myopia ‐ Its etiology and prevalence

AbstractPurpose Myopia (short‐ sightedness) is a significant health problem that is fast rising in prevalence in many parts of world including Europe and USA and at a much higher percentage for population in parts of Asia. Also high myopia is associated with the risk of developing other sight threatening eye conditions.Methods An analysis of the published prevalence rates for myopia with the risks and morbidity associated with high levels of myopia. Also factors that are considered to play a role in the development and progression of the condition will be discussed with emphasis on published data for the role of these factors.Results Whilst the role of individual factors is yet to be elucidated both environmental and genetic factors have been considered to play a role. An increased prevalence of myopia in urban versus rural populations, association with outdoor/indoor work, supports and provides evidence for the role of environment. In this regard, many of the previous efforts have focussed on accommodative effort and blur at the central retina during near visual tasks. More recent evidence suggests that the peripheral retina also plays a role in emmetropisation and development of refractive errors.Conclusion This presentation will discuss the rates and differences in the prevalence of myopia across various populations. In addition, current hypotheses considering the aetiology of development and progression of myopia will be discussed. Commercial interest

Laser-Assisted In Situ Keratomileusis in High Levels of Myopia With the Amaris Excimer Laser Using Optimized Aspherical Profiles

To evaluate the clinical outcomes of laser-assisted in situ keratomileusis (LASIK) surgery for the correction of high myopia using a new generation of excimer laser (500-Hz repetition rate) and optimized aspherical profiles. Retrospective interventional case series. Retrospective study including 51 eyes of 32 patients (age range 23-61 years) with high levels of myopia or myopic astigmatism (spherical equivalent ≥8.5 diopters [D]). All cases underwent uneventful LASIK surgery using the sixth-generation excimer laser Amaris from Schwind and a femtosecond platform for flap creation. Postoperative changes in visual acuity and refraction were recorded and analyzed during a 6-month follow-up. A significant improvement of about 15 logMAR lines was observed in uncorrected distance visual acuity (UCDVA) at 3 months after surgery (P < .01), with no significant changes afterwards (P = .61). This improvement was consistent with a significant reduction of manifest refraction (P < .01). Best corrected distance visual acuity (BCDVA) remained unchanged or improved in 98% of eyes at 3 months postoperatively, with only 1 eye losing 1 logMAR line of BCDVA. A similar distribution of BCDVA data was observed at 6 months postoperatively. A total of 84.3% of eyes had a postoperative spherical equivalent within ±0.50 D of emmetropia. A limited but significant induction of primary spherical aberration and coma was also found (P < .01). LASIK enhancement was required during the follow-up in only 4 eyes (7.8%). LASIK for high myopia using optimized aspherical profiles and the Amaris excimer laser is a safe, effective, and predictable procedure.

Differences in Visual Performance of Acrysof ReSTOR IOL in High and Low Myopic Eyes

To determine the differences in refractive and visual results obtained in eyes with high and low myopia after multifocal intraocular lens (IOL) implantation. Monocular visual acuity for distance and near, with and without distance correction, and photopic and mesopic contrast sensitivity were measured at 6 months after surgery in 152 myopic eyes implanted with the AcrySof ReSTOR Natural (SN60D3) IOL. Two groups were created: high and low myopia (76 eyes in each). Monocular best distance-corrected visual acuity was 0.02+/-0.06 logMAR for low myopes and 0.05+/-0.09 logMAR for high myopes. Monocular best distance-corrected near visual acuity was 0.04+/-0.05 and 0.07+/-0.08 logMAR for low and high myopes, respectively. Contrast sensitivity for high myopic eyes under photopic conditions was lower, primarily at high spatial frequencies, in relation to low hyperopic. Differences between both groups were statistically significant for 6 and 18 cycles per degree (cpd) spatial frequencies (p<0.006). At mesopic level, high myopic eyes showed lower values compared to low myopic eyes for all spatial frequencies. However, these differences were only statistically significant for 3, 6, and 12 cpd (p<0.003). The AcrySof ReSTOR IOL provided good visual acuity and contrast sensitivity for both distance and near, with and without distance correction; however, better results were found in low myopic eyes compared to those obtained in eyes with high levels of myopia.

Season of Birth, Daylight Hours at Birth, and High Myopia

Mandel et al recently reported that season of birth and daylight hours (photoperiod) at birth were associated with moderate and high levels of myopia in Israeli conscripts. We sought to investigate whether these associations were evident in subjects from the United Kingdom (UK). Retrospective cross-sectional study. The study population comprised 74,459 subjects aged 18 to 100 years attending UK optometry practices for an eye examination. Data comprising non-cycloplegic spectacle prescription, sex, date of birth, and date of eye examination were collected from UK optometry practices. The average refractive error in fellow eyes was used to classify the degree of myopia in diopters (D) for each subject as follows: absent (>-0.75 D), low (-0.75 to -2.99 D), moderate (-3.00 to -5.99 D), or high (<-6.00 D). The average monthly hours of daylight for London, UK, were classified into 1 of 4 "photoperiod categories," following Mandel et al. The odds ratio (OR) for each level of severity of myopia was calculated using multivariate logistic regression with age, sex, and either season of birth or photoperiod category as risk factors. The OR for season of birth and photoperiod category as potential risk factors for myopia. Season of birth was significantly associated with the presence of high myopia: Subjects born in summer or autumn were more likely to be highly myopic compared with those born in winter (summer OR=1.17; 95% confidence interval [CI], 1.05-1.30; P=0.006; autumn OR=1.16; 95% CI, 1.04-1.30; P=0.007). However, season of birth was not a significant risk factor for low or moderate myopia. Photoperiod category was weakly associated with low myopia (OR=0.94; 95% CI, 0.89-0.99; P=0.019), but with a direction of effect opposite to that observed by Mandel et al. As in Israel, a disproportionate number of UK high myopes were born in summer or autumn rather than in winter. However, unlike the situation in Israel, this association does not seem to be related to daylight hours during the postnatal period, implicating alternative physiologic influences that vary with season, such as birth weight.

Refinement of the MYP3 locus on human chromosome 12 in a German family with Mendelian autosomal dominant high-grade myopia by SNP array mapping

Myopia, or short-sightedness, is the most common form of vision disorder worldwide. Higher levels of myopia, usually defined as an axial eye length of >26 mm or a refractive error of < -5.00 diopters are often designated as 'pathologic' myopia, because of the predisposition to develop further eye disorders such as retinal detachment, macular degeneration, cataract, or glaucoma. Many distinct forms of autosomal dominant non-syndromic high-grade myopia are described in humans. While the underlying chromosomal locations and critical disease intervals have been identified and located to physical map positions, the gene defects and causative mutations responsible for autosomal dominant myopia remain elusive to date. Examination of a German six-generation kindred by 10K whole genome chips led to the identification of a 19-cM map segment as being the most likely familial myopia candidate region spanning from chromosomal band 12q14.3 to 12q21.31 (MYP3). In our family, a maximum multi-point LOD score of 3.9 was obtained between rs1373877 and rs717996. The recombination breakpoints in this family and the interval of the originally reported German/Italian family defining the MYP3 locus on chromosome 12 (OMIM 603221, two-point LOD score 3.85 for markers D12S1706 and D12S327 at 12q21-23) allowed us to significantly refine a minimum consensus region. This new composite region is located between microsatellite marker D12S1684 at 75.8 K and SNP_A-1509586 (alias rs717996) at position 82,636,288 bp, and narrows the original 30.1 cM of the MYP3 interval to 6.8 cM. The refined MYP3 interval allowed us to restrict the list of database-indexed genes to 25, several of which are promising MYP3 candidates based on similarities with genes and proteins involved in vision physiology and eye disease. While autosomal dominant high-grade myopia is recognized to be genetically heterogeneous, our results suggest genetic homogeneity of the MYP3-based condition in families that share the same ethnic and geographical background. The future identification of this MYP3 gene may provide insights into the pathophysiology of myopia and eye development.

Ablation centration in myopic laser in situ keratomileusis: comparing the Visx S3 ActiveTrak and the Visx S2

Purpose To compare ablation centration and outcome measurements in myopic laser in situ keratomileusis (LASIK) using the eye-tracking Visx S3 ActiveTrak and the nontracking Visx S2 excimer lasers. Setting University-based refractive surgery practice. Methods In a retrospective study, 71 consecutively treated myopic eyes that had LASIK with the Visx Star S3 ActiveTrak were compared to 71 control-matched eyes treated with the Visx Star S2 without pupil tracking. Primary outcome variables including ablation centration, uncorrected visual acuity, best spectacle-corrected visual acuity, manifest refraction, complications, and induced cylinder analyzed by vector analysis were evaluated 3 months postoperatively. Results The myopia ranged from –1.50 to –11.25 diopters (D) and the cylinder, from +0.25 to +2.75 D. Ninety-four of 142 eyes (66%) were available for analysis at 3 months; 50 eyes could be used to analyze ablation centration. At 3 months, the mean decentration of the ablation zone from the entrance pupil was 0.22 mm ± 0.20 (SD) in tracked eyes (n = 25) and 0.21 ± 0.26 mm in nontracked eyes (n = 25) ( P = .88). Three eyes (12%) in the tracked group were decentered 0.5 to 1.0 mm, and 1 eye (4%) in the nontracked group was decentered more than 1.0 mm. All other eyes were decentered less than 0.5 mm. There was an association in the tracked group between greater decentrations and higher levels of myopia ( r = 0.67), but this association did not exist in the nontracked group ( r = −0.03). Conclusion Comparable ablation centration as well as visual and refractive outcomes can be achieved with and without active eye tracking during myopic and astigmatic myopic LASIK.

Stability after laser in situ keratomileusis in moderately and extremely myopic eyes

Objective: To evaluate the stability, mechanism, and degree of regression following laser in situ keratomileusis (LASIK) in cases with moderate to extreme myopia after 2 years of follow-up. Setting: Single-center clinical trial. Methods: Fifty-two eyes of 38 patients were enrolled in the study. One year follow-up was available for 47 eyes of 35 patients and 2 year follow-up for 39 eyes of 27 patients. Eyes were divided into 2 groups based on the level of preoperative myopia: Group 1, moderate to high myopia ≥15.0 diopters (D) (range −7.0 to −15.0 D, n = 24); Group 2, extreme myopia >15.0 D (range −15.3 to −25.8 D, n = 15). Laser in situ keratomileusis was performed using the Chiron Automated Corneal Shaper® microkeratome and the Summit OmniMed excimer laser. Manifest spherical equivalent, mean central keratometry, and central corneal thickness (CCT) were measured preoperatively and 12 and 24 months postoperatively. Results: Group 1 exhibited a mild myopic shift (mean −0.07 ± 0.28 D; P > .2) and a mild increase in keratometry (mean 0.05 ± 0.46 D; P > .6), with an accompanying increase in CCT (mean 7.5 ± 12.2 μm; ( P = .006) at 24 months. Group 2 displayed a significant myopic shift (mean −0.7 ± 0.7 D; P = .001) and a significant increase in keratometry (mean 0.4 ± 0.5 D; P = .01), with a mild increase in CCT (mean 2.4 ± 9.7 μm; P = .35) at 24 months. Corneal ectasia was evident in 1 eye in the extreme myopia group. Conclusion: The refractive effect of myopic LASIK up to −15.0 D remained reasonably stable during the second postoperative year. Significant regression of the refractive effect occurred in eyes with higher levels of myopia (>15.0 D), with the risk of progressive ectasia. Extreme caution is recommended when myopic LASIK is performed in eyes with higher levels of myopia.