Refractive Error Research Articles

Assessing the predictability of five intraocular lens calculation methods in eyes with prior myopic keratorefractive lenticule extraction.

To evaluate and compare the predictability of five methods of intraocular lens (IOL) calculation in eyes with prior keratorefractive lenticule extraction (KLEx) for the treatment of myopia. A retrospective case study included 100 eyes of 52 patients who underwent myopia and myopia with astigmatism treatment with small incision lenticule extraction (SMILE). Preoperative and 3-month postoperative measurements of optical biometry and corneal tomography were obtained. The spherical equivalent of the refractive change induced by surgery was converted to the corneal plane (SMILE-dif). A physically well-defined method was developed in which the same IOL model was implanted before and after SMILE. IOL power was calculated using ray-tracing (RT-Sirius), and several IOL power calculation formulas (Kane, EVO 2.0, Barrett Universal II Formula, Hoffer QST) before surgery. After surgery, IOL power was calculated with RT-Sirius, Kane using Mean Pupil Power at 5.5mm by ray tracing, EVO 2.0 Post Myopic LASIK/PRK, Barrett True K and Hoffer QST Post Myopic LASIK/PRK after surgery. The difference between the refractive error induced by the IOL before and after SMILE in the corneal plane (IOL-dif) was compared with SMILE-dif. The predicted error (PE) was calculated as the difference between SMILE-dif and IOL-dif. The PE obtained was 0.26 ± 0.55 diopters (D), 0.10 ± 0.45 D, 0.40 ± 0.37 D, -0.03 ± 0.36 D, 0.02 ± 0.51 D, with RT-Sirius, Kane, EVO 2.0, Barrett True K, and Hoffer QST respectively. PE was not statistically significantly different between Barrett True K and Hoffer QST, with differences being more homogeneous with Barrett, (variance σ2 = 0,13). The absolute EP obtained with Barrett True K achieved 84% of cases within ± 0.5 D, followed by Kane (72%), Hoffer QST (65%), EVO (61%) and RT-Sirius (59%). Barrett True K formula was the most accurate method for IOL calculation in eyes that had undergone SMILE for the correction of myopia. What is known The literature regarding IOL power calculation after SMILE is sparse, and the methods used to estimate corneal power following LASIK/PRK may not be applicable to SMILE procedures. The most common approach to investigating the predictability of IOL calculation formulas involves a theoretical model encompassing the virtual implantation of an IOL. What is new The Hoffer QST formula, Kane formula using Mean Pupil Power at 5.5mm, EVO 2.0, and Sirius' Ray Tracing software had not been previously evaluated using this approach. The Barrett True K formula was the most accurate method for IOL calculation in eyes that had undergone SMILE for myopia correction, outperforming Ray Tracing.

Refractive errors, amblyopia risk factors and vision screening in children aged 7–10 years in Aotearoa New Zealand

ABSTRACT Clinical relevance Vision screening is important for detecting undiagnosed vision conditions that are common in school-aged children. However, current vision screening protocols are poor at detecting vision conditions that are most common in the Aotearoa New Zealand paediatric population. Background Uncorrected refractive error and amblyopia are the most common causes of visual impairment in children. The most appropriate vision screening method depends on the refractive error profile of the population. This study aimed to: estimate the prevalence of refractive errors and amblyopia risk factors among children living in Aotearoa New Zealand; describe previous participation in preschool vision screening and determine the diagnostic accuracy of potential screening methods. Methods Children aged 7–10 years received comprehensive eye examinations, including cycloplegic refraction, in their school. Eye examination results were assessed for refractive error and amblyopia risk factors. The sensitivity and specificity of individual vision tests for detecting any vision conditions was calculated to assess the most effective tests for vision screening. Results Eye examinations were completed for 237 children and cycloplegic refraction data was available for 220 of these children. Significant refractive error (need for glasses) was detected in 23.6% of children (7.7% myopia, 7.7% hyperopia, 15.0% astigmatism). Amblyopia risk factors were detected in 9.1% of children. Preschool vision screening had been completed by 78.5% of children. Distance visual acuity screening alone had a sensitivity of 39% for detecting vision conditions, with addition of the Spot Vision Screener improving sensitivity to 65%. Conclusion Astigmatism is the most frequent refractive error among children aged 7–10 years living in Aotearoa New Zealand. Distance visual acuity screening alone is ineffective in detecting refractive error in children in Aotearoa New Zealand. Further research investigating refractive errors across the paediatric population in Aotearoa New Zealand is required to determine the optimal timing and appropriate protocols for school-aged vision screening.

Subjective quasi-vector-based refraction with a conventional phoropter.

To introduce a novel methodology for subjective refraction based on power vectors with a conventional phoropter. A conventional phoropter was used to measure power vector components of refraction (M, J0 and J45) directly by using the sphere power (for M measurement) and the cylinder power combined with the Jackson cross-cylinders (for J0 and J45 measurements). Conventional subjective refraction was also performed, and this result was mathematically transformed into power vector notation for comparison purposes. Visual acuities with the conventional prescription and the quasi-vector-based prescription were compared. Refractive error from 40 healthy participants was measured by conventional and quasi-vector-based subjective refraction. No differences were found between methods for any of the power vector components of refraction (p > 0.21 in all cases). The visual acuity achieved with the prescriptions yielded similar values (p = 0.85). Subjective refraction can be measured directly in power vector notation using a conventional phoropter without any additional adaptation and computation.

In vivo volumetric analysis of retinal vascular hemodynamics in mice with spatio-temporal optical coherence tomography.

Microcirculation and neurovascular coupling are important parameters to study in neurological and neuro-ophthalmic conditions. As the retina shares many similarities with the cerebral cortex and is optically accessible, a special focus is directed to assessing the chorioretinal structure, microvasculature, and hemodynamics of mice, a vital animal model for vision and neuroscience research. We aim to introduce an optical imaging tool enabling in vivo volumetric mouse retinal monitoring of vascular hemodynamics with high temporal resolution. We translated the spatio-temporal optical coherence tomography (STOC-T) technique into the field of small animal imaging by designing a new optical system that could compensate for the mouse eye refractive error. We also developed post-processing algorithms, notably for the assessment of (i) localized hemodynamics from the analysis of pulse wave-induced Doppler artifact modulation and (ii) retinal tissue displacement from phase-sensitive measurements. We acquired high-quality, in vivo volumetric mouse retina images at a rate of 113Hz over a lateral field of view of . We presented high-resolution en face images of the retinal and choroidal structure and microvasculature from various layers, after digital aberration correction. We were able to measure the pulse wave velocity in capillaries of the outer plexiform layer with a mean speed of 0.35mm/s and identified venous and arterial pulsation frequency and phase delay. We quantified the modulation amplitudes of tissue displacement near major vessels (with peaks of 150nm), potentially carrying information about the biomechanical properties of the retinal layers involved. Last, we identified the delays between retinal displacements due to the passing of venous and arterial pulse waves. The developed STOC-T system provides insights into the hemodynamics of the mouse retina and choroid that could be beneficial in the study of neurovascular coupling and vasculature and flow speed anomalies in neurological and neuro-ophthalmic conditions.

Multiphoton scaling of femtosecond laser-induced refractive index change (LIRIC) in hydrogels and rabbit cornea

To find optimal conditions for performing laser induced refractive index change (LIRIC) in living eyes with both safety and efficacy, we investigated multiphoton excitation scaling of this procedure in hydrogel and excised corneal tissue. Three distinct wavelength modalities were examined: high-repetition-rate (HRR) and low-repetition-rate (LRR) 405 nm systems, as well as 800 nm and 1035 nm systems, whose LIRIC-inducing properties are described for the first time. Of all the systems, LRR 405 nm-LIRIC was able to produce the highest phase shifts at the lowest average laser powers. Relative merits and drawbacks to each modality are discussed as they relate to future efforts towards LIRIC-based refractive error correction in humans.

Is the Change in Prevalence of High Myopia Compared to That of Myopia Really Disproportionate?

It has been noted that, at higher prevalences, the rate of change in the prevalence of high myopia seems to be disproportionately greater compared with the rate of change in the prevalence of myopia. A simple, evidence-based explanation for this relationship is offered. Using a convenience sample of 41 datasets with prevalence estimates for at least two refractive error thresholds (e.g., -0.50 and -6.00 D) the common slope of the logit vs. refractive threshold was applied to model expected rates of high myopia across the myopia prevalence range and the corresponding ratio of change in high myopia to myopia prevalence. The logit of high myopia is related linearly to the logit of myopia. The ratio of increase in high myopia prevalence to that for myopia prevalence increases with underlying prevalence. For example, an increase in myopia prevalence from 19% to 20% is modelled to be accompanied by a 0.1% increase in the prevalence of high myopia from 1.55% to 1.65%-a ratio of 0.1. Conversely, an increase in myopia prevalence from 79% to 80% is predicted to result in a 1% increase in the prevalence of high myopia from 20.6% to 21.6%-a ratio of 1.0. The increase in the prevalence of high myopia compared with that of myopia as the latter increases is merely a function of the underlying nature of refractive error probability distributions and requires no further investigation as to its origin. This study shows how the prevalence of myopia and high myopia are inter-related. A widespread effort to slow myopia progression will affect the prevalence of high myopia but not myopia in general. In contrast, efforts to delay myopia onset will affect both.

Regional/ethnic differences in ocular axial elongation and refractive error progression in myopic and non-myopic children.

To determine the regional and ethnic differences in ocular axial elongation and refractive error progression in myopic and non-myopic children. A retrospective analysis of 15 longitudinal clinical and population-based studies was conducted in the UK, Sweden, Australia (classified as European), China, and Vietnam (classified as East Asian) between 2005 and 2021. A total of 14,593 data points from 6208 participants aged 6-16 years with spherical equivalent from +6 to -6 D were analysed. Progression was annualised from longitudinal axial length and cycloplegic spherical equivalent (SE) refraction. Generalised estimating equation models including main effects and interactions were used for model building. Age and region-specific estimates for myopes and non-myopes and confidence intervals are reported. Factors affecting axial elongation and SE progression in children included being myopic, followed by age, region/ethnicity and sex. The magnitude of regional/ethnic differences was dependent on myopia and age. Axial elongation and SE progression were lower in European compared with East Asian children, but differences were reduced with increasing age and differences in axial elongation were larger in myopes than non-myopes. Age-specific regional/ethnic differences indicated that axial elongation for a 6-year-old East Asian myopic child was greater than a European child by 0.15 mm/year (0.58 vs. 0.43 mm/year) and by 0.09 mm/year (0.35 vs. 0.26 mm/year) for a 10-year-old myope. SE progression was lower in a 6-year-old European myope by 0.48 D/year and at 10 years of age by 0.34 D/year compared with an East Asian myope. There are regional/ethnic differences in age-specific refractive and axial growth patterns in both myopic and non-myopic eyes, with more marked differences in younger East Asian children who demonstrated a higher axial growth and greater negative SE shift than their non-Asian peers. Regional/ethnic differences in progression reflect environmental and ethnic variations. Age and region/ethnicity-specific estimates could contribute as a reference for future comparisons.

Juvenile Myopia: The Silent Vision Understanding, Preventing, and Managing Childhood Myopia

Juvenile myopia, a significant visual impairment characterized by blurred distance vision, is increasingly prevalent among Indian children. This review explores the multifactorial etiology of myopia, including genetic predisposition, environmental influences, and lifestyle factors such as prolonged near work and limited outdoor activities. The pathophysiology involves abnormal eye elongation driven by genetic and environmental factors, leading to refractive errors. Clinical manifestations include blurry distance vision, squinting, eye strain, and headaches, impacting academic performance and quality of life. Emphasis on early detection, parental awareness, and adherence to treatment protocols is crucial in controlling myopia progression and preventing long-term complications such as retinal detachment, myopic maculopathy, and glaucoma. This review underscores the need for comprehensive public health strategies to address the growing burden of juvenile myopia in India. Juvenile myopia is rapidly becoming a significant public health concern in India, with increasing prevalence driven by lifestyle changes, urbanization, and academic pressures. This systematic review aims to examine the prevalence, risk factors, and interventions for childhood myopia, with a focus on understanding the silent nature of this condition, identifying early prevention strategies, and outlining management techniques to curb its progression.

Current Treatment of Pathological Myopia and Sclera-Targeted Therapies

Myopia is a refractive error that arises from the interaction of genetic and environmental factors. In recent years, there has been a significant increase in the prevalence of myopia. As the prevalence of myopia increases, so does the frequency of complications leading to vision loss associated with pathological myopia. Therefore, various methods and treatments are being explored to halt and prevent the progression of myopia in children. In myopia control, spending time outdoors, the use of low-dose atropine, and new generation lens technologies are being investigated. Spending more time outdoors appears to be the most reliable strategy. While some new lens designs seem to be quite effective in preventing progression, recent studies have shown that the expected success from atropine has not been achieved. Further research is needed on the long-term effects of combining different methods.

Refractive errors among schoolchildren in the Middle East: A systematic review and meta-analysis

Refractive errors among schoolchildren in the Middle East: A systematic review and meta-analysis

Femtosecond laser assisted cataract surgery in a cataract patient with low vaulted ICL following LASIK: a case report

BackgroundApart from the conventional utilization of ICL implantation for the correction of refractive errors, its recent applications extend to correcting refractive errors post laser refractive surgery. Notably, the development of cataracts stands out as a prevalent postoperative complication, often associated with low vault. Previous cases have demonstrated successful management of cataracts with ICL through the combination of FLACS and ICL removal coupled with IOL implantation, resulting in favorable postoperative visual outcomes. Herein, we present a case of cataract with low vault ICL following LASIK and its subsequent management.Case presentationA 46-year-old male presented with vision loss in the right eye for 9 months, and he had undergone LASIK 22 years prior and had ICL implantation in both eyes 2 years ago to correct refractive error. One day after ICL implantation, both eyes exhibited the UDVA of 1.2 and 1.0, well-positioned ICLs, and approximate vault of 150 μm and 200 μm. Six months ago, the patient became aware of blurred vision in the right eye for a duration of 3 months. Examination revealed cloudy lens cortex in the right eye. During the current review, the UDVA of the right eye was 0.6, where nasal wedge-shaped clouding was evident and worsened, while the left eye lens remained transparent. AS-OCT demonstrated the vault of 54 μm in the right eye and 83 μm in the left eye. Considering the patient’s history of LASIK and the presence of right eye cataract, a monovision approach was adopted. The patient underwent FLACS combined with ICL extraction and monofocal IOL lens implantation in the right eye. At 10 days postoperatively, the patient exhibited the UDVA of 1.0.ConclusionsOur report confirms the feasibility of FLACS in managing cataracts in patients with low vault ICL following LASIK. This procedure does not pose significantly greater challenges than in typical cataract cases, although meticulous care remains essential throughout every step of the surgery, particularly during laser scanning and positioning. With adequate preoperative preparation and precise calculation of the IOL power, surgical outcomes can meet expectations fully.

Prevalence of visual abnormalities detected through paediatric vision screening in Queensland, Australia.

Vision screening programs can provide epidemiological information regarding visual impairment in children. This study aims to report the characteristics of visual abnormalities diagnosed through the Primary School Nurse Health Readiness Program (PSNHRP) in Queensland, Australia. A retrospective review of vision screening records from the PSNHRP between January 2017 and December 2020 was undertaken. Children aged between 4 and 7 who underwent vision screening were included for review. Children with a visual acuity of worse than 6/9-1 using the Parr 4 m letter-matching chart or those who failed the SPOT Vision Screener were referred to an optometrist or ophthalmologist for review. 164 890 children underwent vision screening. 12148 children failed visual screening (7.4%) and were referred for an eye assessment. 6011 (69.4%) of the 8659 children who attended ophthalmic review had a confirmed visual abnormality. Of 164 890 screened children, 1187 (0.72%) were confirmed to have anisometropia, 3843 (2.33%) had refractive error, 194 (0.12%) had strabismus, 755 (0.46%) had anisometropic amblyopia, 136 (0.08%) had strabismic amblyopia, and 1356 (0.82%) had an unspecific abnormality. There was no statistically significant difference in the age at screening between any visual abnormality (p = 0.94). Anisometropia, refractive error, and strabismus were significantly more common in females than males (p = 0.03, p < 0.01, and p = 0.03 respectively), whereas anisometropic amblyopia was more common in males (p < 0.01). We report the prevalence of visual abnormalities detected through the PSNHRP vision screening program. Identification of medical or socioeconomic risk factors that are likely to be associated with visual abnormalities can help to optimise vision screening programs.

Modeling Refractive Error Populations by Weibull Distribution for Minimum Visual Correction Diopter Range in XR Systems

Modeling Refractive Error Populations by Weibull Distribution for Minimum Visual Correction Diopter Range in XR Systems

Association of Refractive Errors with Axial Length and Anterior Chamber Depth in Different Age Groups

Purpose: To determine association of refractive errors with axial length and anterior chamber depth in different age groups. Study Design: Cross-sectional study. Place and Duration of Study: Ophthalmology Department of Dow University Hospital (Ojha campus),Dow International Medical College, Dow University of Health Sciences, Karachi, Pakistan from October 2020 to December 2020. Methods: Eighty-three individuals of different age groups ranging from 11-80 years were included in the study.Ocular measurements including refractive error, axial length, and anterior chamber depth were determined in all participants. The association of refractive error with anterior chamber depth and axial length was tested by using two independent sample t test, Mann-Whitney U test and ANOVA. Results: Among 83 individuals, males were 42.2% (n=35) and females were 57.8% (n=48). Most common type of refractive error was astigmatism which was found in 48.2% (n=40) participants. The overall average depth of anterior chamber (mm) and average axial length (mm) were 3.11±0.39 and 23.27±0.87 respectively. Mean differences in anterior chamber depth were statistically significant among different age groups . Statistically significant differences in mean axial length were found among different refractive errors . Conclusion: These results show a significant relation of different refractive errors with axial length and anterior chamber depth and it can be helpfulin explaining the risk factors of different ocular diseases as well asit can also be helpful in clinical and diagnostic purposes in ophthalmology.

Volume measurement of the vitrectomised eye and its applications in practice.

To estimate the vitreous cavity replacement volume after pars plana vitrectomy and analyze its correlation with axial length and refractive error. Observational cross-sectional study on 103 eyes undergoing vitrectomy. Fluid-air exchange was performed using a soft-tip cannula connected to a PVC tubing, the distal end of which opened into a 10-cc syringe without the plunger. The collected fluid was measured (and correction factors applied) to estimate the vitreous cavity volume. The mean axial length of 103 eyes was 23.43 ± 1.54 mm. The mean vitreous cavity volume was 4.46 ± 0.83 mL (2.8-8.1 mL). There was a strong positive correlation between axial length and vitreous volume, which was stronger for pseudophakic and aphakic groups than for phakic groups. Accurate assessment of vitreous cavity volume can enable precise quantification of tamponade, intravitreal drugs, and intravitreal chemotherapeutic agents. This will allow better surgical outcomes, decreased toxicity, and increased cost-effectiveness due to lesser wastage. To estimate the vitreous cavity replacement volume after pars plana vitrectomy and analyze its correlation with axial length and refractive error.

Corneal endothelial density and morphology in long-term soft contact lens users in Japan: a retrospective cross-sectional study of 17,732 eyes

Purpose There is a lack of long-term and large-scale studies on the adverse effects of soft contact lenses (SCLs) on the corneal endothelia of Asian populations. Here, we aimed to examine the effects of long-term SCL use on corneal endothelial density and morphology. Materials and Methods This retrospective study involved consecutive patients at the Miyata Eye Hospital (Miyazaki, Japan), who had used SCLs for more than 1 year. Patients with ophthalmological disorders without refractive errors were excluded. The period of SCL use, SCL type, corneal endothelial cell density (ECD), appearance rate of hexagonal cells (HEX), and coefficient of variation of cells (CV) were analyzed. Results In total, 17,732 eyes of 8866 patients were included in the analysis (age, 26.0 ± 8.8 years). The mean period of SCL use was 6.3 ± 5.4 years. Multivariate regression analysis revealed that ECD and HEX were significantly negatively correlated with the period of SCL use, age, and sex (p < 0.001 for all). The CV was significantly positively correlated with the period of use (p < 0.001), sex (p = 0.002), and age (p < 0.001). Conclusions Corneal ECD, HEX, and CV were significantly associated with the period of SCL use in long-term users. It is essential to regularly check the corneal endothelium in patients with a history of long-term SCL use.

Intraoperative Aberrometry versus Preoperative Biometry for Intraocular Lens Power Calculations: A Report by the American Academy of Ophthalmology

To evaluate the published literature to compare intraoperative aberrometry (IA) with preoperative biometry-based formulas with respect to intraocular lens (IOL) power calculation accuracy for various clinical scenarios. Literature searches in the PubMed database conducted in August 2022, July 2023, and February 2024 identified 157, 18, and 6 citations, respectively. These were reviewed in abstract form, and 61 articles were selected for full-text review. Of these, 29 met the criteria for inclusion in this assessment. The panel methodologists assigned a level of evidence rating to each of the articles; 4 were rated level I, 19 were rated level II, and 6 were rated level III. Intraoperative aberrometry performed better than traditional vergence formulas, including the Haigis, HofferQ, Holladay, and SRK/T, and similarly to the Barrett Universal II and Hill-RBF with respect to minimization of spherical equivalent (SE) refractive error. For toric IOLs, IA outperformed formulas that only considered anterior corneal astigmatism and was similar to formulas like the Barrett Toric Calculator (BTC), which empirically account for the contribution from the posterior cornea. In eyes with a history of corneal refractive surgery, IA performed similarly to the Barrett True-K and slightly better than other tested methods, including the Haigis-L, Shammas, and Wang-Koch-Maloney formulas. Intraoperative aberrometry corresponds well with modern vergence formulas, including the Barrett Universal II, Hill-RBF, BTC, and Barrett True-K. It has greater accuracy than traditional vergence-based IOL power calculation formulas in eyes with and without a history of corneal refractive surgery. Proprietary or commercial disclosure may be found after the references.

Anatomical compensation of retinal nerve fiber layer improves the detection of glaucoma between ethnicities.

The study aimed to evaluate the impact of compensating retinal nerve fiber layer (RNFL) thickness for demographic and anatomical factors on glaucoma detection in Chinese and Indian adults. A population-based study included 1995 healthy participants (1076 Chinese and 919 Indians) to construct a multivariable linear regression compensation model. This model was applied to 357 Chinese glaucoma patients, 357 healthy Chinese, and 357 healthy Indians using Cirrus spectral-domain optical coherence tomography (OCT). The compensated RNFL thickness considered age, refractive error, optic disc parameters, and retinal vessel density. Results showed that although the average RNFL thickness was significantly higher in Chinese participants compared to Indians, the compensation model reduced this difference to nonsignificance. Moreover, the compensation model significantly improved the area under the receiver operating characteristic curve (0.90 vs. 0.78; p<0.001), sensitivity (75% vs. 51%), and specificity (67% vs. 32%) in distinguishing Chinese glaucoma patients from healthy Indian individuals. The compensation model significantly enhanced the diagnostic accuracy of RNFL thickness in distinguishing glaucoma in the Chinese ethnic group compared to the OCT instrument's default values. These results suggest that modifying RNFL measurements based on individual characteristics can yield substantial benefits for glaucoma detection across ethnicities.

Deep phenotyping of 11 individuals with pathogenic variants in RNU4-2 reveals a clinically recognizable syndrome

PurposeDespite ever-increasing knowledge of the genetic etiologies of neurodevelopmental disorders, approximately half remain undiagnosed after exome or genome sequencing. Here, we provide a deep clinical characterization of 11 previously unreported patients with a recently described neurodevelopmental disorder (NDD) due to pathogenic variants in RNU4-2. MethodsThe 11 patients were identified in a pool of 70 patients selected for targeted RNU4-2 sequencing on the basis of their clinical phenotypes from a cohort of 1032 individuals with a NDD and without a prior genetic diagnosis. ResultsThe 11 patients were aged between 13 months and 36 years. All patients showed moderate to severe developmental delay and/or intellectual disability. Height and weight were below 10th percentile and most showed microcephaly. In almost 50% of the patients, intrauterine growth retardation was detected. All patients showed a distinctive pattern of dysmorphic features, including hooded upper eyelid and epicanthus, full cheeks, tented philtrum, mouth constantly slightly open with an everted lower lip vermilion, high palate, and profuse drooling. Of 11 patients, 64% also presented with ophthalmological problems (mainly strabismus, nystagmus, and refraction errors) and 64% had musculoskeletal features (joint hypermobility, mild scoliosis, and easy fractures). ConclusionThis work provides an improved characterization of the phenotypic spectrum of RNU4-2 syndrome across different age groups and demonstrates that thorough clinical assessment of patients with an NDD can be enhanced significantly for this novel syndrome.

Efficacy and Safety of Pilocarpine Eye Drops Combinations for Treating Presbyopia in a Thai Population: A Randomized Crossover Trial

Objective: This study aimed to assess and compare the effectiveness and side effects of various concentrations of pilocarpine eye drops (1.5%, 1.25%, and 1%), with and without 0.1% brimonidine, in treating presbyopia, specifically in a Thai population. Materials and Methods: A prospective, randomized, double-blinded, and crossover trial was conducted at Siriraj Hospital from August 2022 to April 2023. The study included emmetropic individuals aged 40 to 60 with presbyopia (near visual acuity not exceeding J1+) and refractive errors within +/- 0.5D. The ten subjects were assigned randomly to 6 groups for the different concentrations and type of eyedrops using a computer-generated systematic randomization to receive 1.5%, 1.25%, and 1% pilocarpine with and without 0.1% brimonidine. And visual outcomes including visual acuity at distance and near were measured at 2, 4, and 6 hours post-application, with adverse effects monitored. Primary outcome was visual acuity at near after applied topical eye drops. Results: Among the 10 participants (30% male, median age 46.5 years old), 1.25% pilocarpine and combined 1.25% pilocarpine + 0.1% brimonidine significantly improved near visual acuity at all time points (statistically significant with Bonferroni correction). Adverse effects, such as dry eye and irritation, were more common with 1.5% pilocarpine + 0.1% brimonidine. Conclusion: In this preliminary study, 1.25% pilocarpine and 1.25% pilocarpine + 0.1% brimonidine showed promise in effectively treating presbyopia in the Thai study population, with acceptable side effect rates. Further research with larger sample sizes is needed to confirm these findings and provide more robust insights into presbyopia management in the Asian demographic.