Refractive Error Research Articles

Refractive Errors of School Children from Economically Disadvantaged Areas in Northwest México.

Background: Refractive errors, including myopia, hyperopia, and astigmatism, are the leading causes of visual impairment in school-aged children and can significantly impact their academic performance and quality of life. This study aimed to assess the prevalence of refractive errors among school children from economically disadvantaged areas in Northwest México, using a consistent methodology to facilitate comparison with global data. Methods: We adopted the Refractive Error Study in Children (RESC) protocol by the World Health Organization to examine the prevalence of myopia, hyperopia, and astigmatism. The study comprised a systematic sampling of children aged 6 to 18 years from diverse schools in Northwest México. Trained optometrists conducted visual acuity testing and autorefraction, while ophthalmologists performed cycloplegic refraction to ensure accuracy. Results: The study found a myopia (SE ≤-1.50 D at least one eye) prevalence of 14.55% (95% CI: 13.27-15.91), with a higher incidence in females (6.92%) compared to males (6.00%) in at least one eye. Hyperopia (SE ≥ +1.00 D at least one eye) was less common, at 3.23% (95% CI: 2.61-3.95), with a slightly higher occurrence in males in at least one eye. Astigmatism (Cylinder ≥ 0.75 D at least one eye) was present in 18.63% (95% CI: 17.21-20.12) of the students in at least one eye, with no significant difference between genders. These findings are consistent with other studies in regions such as Puerto Rico and Iran, indicating widespread refractive error issues among schoolchildren. Conclusions: The high prevalence of refractive errors, particularly myopia and astigmatism, highlights the critical need for regular vision screenings in schools and the implementation of public health interventions to provide corrective eyewear. Our study confirms the importance of utilizing standardized methodologies like the RESC protocol to compare refractive error prevalence across different geographical and socio-economic contexts, thereby informing global public health strategies.

Comparison of early visual outcomes after SMILE using VISUMAX 800 and VISUMAX 500 for myopia: a retrospective matched case–control study

VISUMAX 800 was introduced to improve the patient experience and clinical outcomes of small incision lenticule extraction (SMILE). This was a retrospective, matched, and case–control study (1:2) controlled for preoperative central corneal thickness and refractive error that compared early refractive and visual outcomes after SMILE using VISUMAX 800 and VISUMAX 500 to treat myopia. We included 50 eyes that underwent the VISUMAX 800 SMILE and 100 eyes that underwent the VISUMAX 500 SMILE. SMILE using VISUMAX 800 was performed using the CentraLign aid for vertex centration. Cyclotorsion was controlled by an OcuLign assistant in the VISUMAX 800 group after corneal marking. Corneal higher-order aberrations (HOAs) were evaluated using a Pentacam 1 month after surgery. No differences were observed in the pre- and post-operative refractive and visual outcomes at 1 day, 1 month, and 6 months after surgery. VISUMAX 800 induced less total HOAs than VISUMAX 500 (P = 0.036). No statistically significant differences were observed in the amounts of induced spherical aberrations or vertical and horizontal comas. No differences were observed in the 1 month and 6 months refractive and visual outcomes between two SMILE procedures, except for VISUMAX 800, which resulted in lower postoperative total HOAs than VISUMAX 500.

The Impact of Ocular Exercises on Headache Symptoms and Sleep Quality Among University Students with Refractive Errors

Background and Objective: Refractive errors are prevalent ocular conditions within the general populations. It has been identified as one of a possible source of headaches and a detriment to sleep quality. The occurrence of refractive errors is particularly high among individuals who are at a higher level of education compared to the general population. Hence the objective of this study is to assess the impact of ocular exercises on headache characteristics and sleep quality and to investigate the correlation between refractive errors, quality of sleep and headache among university students with refractive errors. Methods: 39 university students with refractive errors were recruited after screening. Based on the type of refractive corrections, they were assigned to 2 experimental and 1 control group. 4 weeks of ocular exercises were performed to investigate the effect of ocular exercises on headache symptoms and sleep quality. The data collected were then analyzed using Paired-sample T-test, One-way ANOVA and Pearson’s correlation in IBM SPSS software statistics version 20. Results: In experimental group 1 (with glasses), there was a significant improvement of headache characteristics (p=0.005) and sleep quality (p=0.010) compared to experimental group 2 (with contact lens) and group 3 (without wearing any glasses or contact lens). Fair to moderate correlation between refractive errors, headache (p<0.0001) (p=0.002), and sleep quality (p=0.018) were analyzed using Pearson analysis. Conclusion: There is a significant impact of ocular exercises on headache symptoms and sleep quality among university students in experiment group. A fair to moderate association between refractive errors, headache and sleep quality. Keywords: Ocular exercises, Refractive errors, Headache, Sleep quality, University students

Clinical Outcomes in Scleral Fixation Secondary Intraocular Lens with Yamane versus Suture Techniques: A Systematic Review and Meta-Analysis.

Background: The purpose of the study is to compare the visual outcomes and complications of sutured scleral fixation (SSF), a traditional and conservative surgical approach, and the newer and faster Yamane technique for secondary intraocular lens placement. Methods: A literature search was performed on PubMed, Embase, and Scopus on studies published between 1 July 2017 to 29 September 2023. Outcomes analyzed included the final best corrected visual acuity (BCVA) between 3 and 12 months to assess the effectiveness of the procedure, post-operative month (POM) 1 BCVA to assess the speed of visual recovery, endothelial cell count (ECC), absolute refractive error, surgical duration, and complication rates. Additional subgroup analyses were performed based on surgeon experience with the technique. Single-surgeon studies had an average of 26 procedures performed, whereas multiple-surgeon studies averaged only 9 procedures performed; these were then used to delineate surgeon experience. A sample-size weighted mean difference (MD) meta-analysis was performed across all variables using RevMan 5.4.1; p < 0.05 was considered statistically significant. Results: Thirteen studies with 737 eyes were included: 406 eyes were included in the SSF group, and 331 eyes were included in the Yamane group. There was no significant difference in the final BCVA between groups in both the single-surgeon versus multiple-surgeon studies (MD = -0.01, 95% CI: [-0.06, 0.04], p = 0.73). In the single-surgeon studies, the BCVA at POM1 was significantly improved in the Yamane group compared to SSF (MD = -0.10, 95% CI: [-0.16, -0.04], p = 0.002). In the multiple-surgeon studies, there was no significant difference in BCVA at POM1 (MD = -0.06, 95% CI: [-0.16, 0.04], p = 0.23). The Yamane group had a shorter surgical duration than SSF in both single-surgeon and multiple-surgeon studies (MD = -24.68, 95% CI: [-35.90, -13.46], p < 0.0001). The ECC, refractive error, and complication rates did not significantly differ amongst all groups. Conclusions: The Yamane technique demonstrated similar long-term visual outcomes and complication rates to the traditional SSF. Visual recovery was significantly faster in the Yamane group in the single-surgeon studies. The operative times were shorter across all Yamane groups. Based on these findings, it is advisable to consider the Yamane technique as a viable, and perhaps preferable, option for patients requiring secondary IOL placement, alongside traditional SSF methods.

Design method for lens desensitization adapted to refractive index error

The design of optical systems not only considers the imaging performance but also the manufacturing difficulty and feasibility of the system. In practice, errors in the manufacturing process of glass materials and deviations in glass material parameters introduced in complex environments can both lead to degradation in the imaging quality of optical systems. Optical systems that are sensitive to glass material errors face increased manufacturing difficulty and reduced stability. This paper, based on geometrical optics theory, establishes an evaluation function for refractive index error sensitivity and analyzes its relationship with optical parameters and glass materials. It proposes a design method to reduce the refractive index sensitivity of optical systems. Through simulation verification and analysis using examples, the validity of the desensitization design method is confirmed.

Web-based telemonitoring of visual function and self-reported postoperative outcomes in cataract care: international multicenter randomized controlled trial.

To compare web-based, self-administered follow-up after cataract surgery to conventional face-to-face follow-up. Eye clinics in the Netherlands, Austria, and Germany. Randomized controlled trial with an embedded method comparison study (ClinicalTrials.gov: NCT04809402). Routine patients with cataract were randomized into 2 groups: The telemonitoring group undertook web-based vision self-assessments and questionnaires from home, while the usual care group received conventional care. All participants had a 4- to 6-week postoperative clinic visit for safety and validation purposes. Outcomes included, the web test's accuracy for assessing postoperative visual acuity (VA) and refractive error, adverse event rates, and patient-reported outcome measurements (PROMs). 94 participants (188 eyes) were enrolled. Web-based uncorrected distance VA testing demonstrated a negligible mean difference (-0.03 ± 0.14 logMAR) when compared with conventional Early Treatment Diabetic Retinopathy Study chart testing, with 95% limits of agreement ranging from -0.30 to 0.24 logMAR. The web-based refraction assessment overestimated the postoperative refractive error (mean difference in spherical equivalent 0.15 ± 0.67 diopters), resulting in a poorer corrected distance VA compared with subjective refraction (mean 0.1 vs -0.1 logMAR). Rates of adverse events and unscheduled consultations were minimal across both groups. Preoperative and postoperative PROM questionnaires had a 100% response rate. Visual functioning (Catquest-9SF and National Eye Institute Visual Function Questionnaire-25) improved postoperatively (mean improvement -0.80 and 16.70, respectively) and did not significantly differ between the 2 groups. The patients with cataract in this study effectively provided postoperative outcome data using a web interface. Both conventional and web-based follow-ups yielded similar PROMs and adverse event rates. Future developments should reduce the variability in the web-based VA test and yield representative refraction outcomes.

Impact of spectacle wear on the quality of life of learners with hearing impairment in Ghana

Background: Visual impairment significantly affects learners with hearing impairment.Aim: To assess the impact of spectacle wear on the quality of life (QoL) of learners with hearing impairment in Ghana.Setting: Six schools for the deaf in Ghana.Methods: A prospective case-control study design was used to assess the QoL among learners with uncorrected refractive error (URE) using the quality-of-life impact of refractive correction (QIRC) questionnaire before and after the provision of spectacles.Results: A total of 138 learners were enrolled in this study, with 69 learners in both the intervention and control groups, respectively. The mean QIRC score improved significantly for the intervention group: QIRC score before = 43.89 ± 8.96 vs. after = 48.82 ± 6.71 (P 0.05 and Cohen’s d = 0.62) but not the control group: QIRC score before = 50.79 ± 11.66 and 51.77 ± 10.67 (P = 0.607). Among the learners provided with spectacles, those who did not comply with spectacle wear had significant differences (P 0.05) in mean QIRC scores before and after the intervention. Only visual acuity (VA) and the magnitude of prescription with QIRC scores after intervention had a significant relationship (P 0.05).Conclusion: Uncorrected refractive error affected the QoL of learners with hearing impairment, and spectacle correction significantly improved their QoL.Contribution: The use of spectacle lenses, VA and magnitude of prescription affected the QoL scores; however, sex and age did not influence the QoL scores.

Clinical Outcomes of Transepithelial Photorefractive Keratectomy Performed with Smart Pulse Technology for the Correction of Moderate to High Myopia.

Purpose: To evaluate the safety and efficacy of the transepithelial photorefractive keratectomy (TransPRK) performed using smart pulse technology (SPT) in myopic eyes with refractive error ranging from -5.25 D to -9.75 D. Methods: This retrospective study evaluated the outcomes of SPT-assisted TransPRK in 150 eyes performed using a 1050 Hz AMARIS excimer laser. Results: At 6 months postoperative, 98% of eyes achieved uncorrected distance visual acuity (UDVA) of 20/25 or better, and postoperative UDVA within one line of preoperative corrected distance visual acuity (CDVA). No eyes lost any line of CDVA. Residual spherical equivalent refraction and cylinder within ±0.50 D of intended correction were achieved in 72% and 67% of eyes, respectively. Ninety-seven percent of eyes reported no halos and glare. Conclusions: TransPRK using a 1050 Hz excimer laser with SPT showed excellent predictability, safety, and efficacy for moderate to high myopia correction.

Clinical characteristics and associated factors of diabetic retinopathy in Sudanese patients

Background: Diabetic retinopathy (DR) is a leading cause of vision loss and preventable blindness, particularly in middle- and high-income countries.Aim: This study aimed to assess the characteristics and associated factors of DR in Sudanese patients with type 2 diabetes mellitus (DM).Setting: A cross-sectional hospital-based study included 119 patients with type 2 DM was conducted at EL-Walidain Eye Hospital, Khartoum, Sudan, from February 2021 to May 2021.Methods: A non-mydriatic digital fundus camera was used for fundus photography, and Scottish Diabetic Retinopathy Grading Scheme was used for the final classification of DR.Results: Females comprised 53.8% of patients, mean age of 58.8 ± 8.5 years. Uncontrolled DM was found in 37.8% with a mean duration of 10.5 ± 4.8 years. Myopia was the most common refractive error found in 57.8% of the uncontrolled group, followed by emmetropia (17.8%). Whereas in the controlled group, 47.3% were hyperopic and 39.2% were myopic. Maculopathy grade M1 was found to be 37.8% in the uncontrolled group and 18.9% in the controlled group, with no significant difference (p = 0.361). Conversely, the difference in retinopathy between the two groups was statistically significant (p = 0.043).Conclusion: Decreased vision and increased retinopathy were associated with an increase in patients’ age. More widespread diabetes awareness and screening programmes to improve diabetes management and control in Sudan and other developing countries.Contribution: This study observed maculopathy grade M1 and myopia were more common in uncontrolled DM, and vision function was inversely correlated with age (p 0.05).

Second harmonic generation microscopy of electromechanical reshaping on corneal collagen

Refractive errors remain a global health concern, as a large proportion of the world's population is myopic. Current ablative approaches are costly, not without risks, and not all patients are candidates for these procedures. Electromechanical reshaping (EMR) has been explored as a viable cost-effective modality to directly shape tissues, including cartilage. In this study, stromal collagen structure and fibril orientation was examined before and after EMR with second-harmonic generation microscopy (SHG), a nonlinear multiphoton imaging method that has previously been used to study native corneal collagen with high spatial resolution. EMR, using a milled metal contact lens and potentiostat, was performed on the corneas of five extracted rabbit globes. SHG was performed using a confocal microscopy system and all images underwent collagen fibril orientation analysis. The collagen SHG signal in controls is uniform and is similarly seen in samples treated with pulsed potential, while continuous EMR specimens have reduced, nonhomogeneous signal. Collagen fibril orientation in native tissue demonstrates a broad distribution with suggestion of another peak evolving, while with EMR treated eyes a bimodal characteristic becomes readily evident. Pulsed EMR may be a means to correct refractive errors, as when comparing its SHG signal to negative control, preservation of collagen structures with little to no damage is observed. From collagen fiber orientation analysis, it can be inferred that simple DC application alters the structure of collagen. Future studies will involve histological assessment of these layers and multi-modal imaging analysis of dosimetry.

Assessing the relationship between anthropometric factors and refractive errors in school-age children: height, weight, or BMI?

Assessing the relationship between anthropometric factors and refractive errors in school-age children: height, weight, or BMI?

Ophthalmic quality of life in the adult Danish population: an epidemiological study

BackgroundOphthalmic quality of life (OQoL) has been investigated in selected parts of general populations and in patients with ocular disease, but OQoL in unselected general populations has not been studied...

Refractive Astigmatism Outcomes of Femtosecond Laser-Assisted Arcuate Keratotomies Combined with Femtosecond Laser-Assisted Cataract Surgery: Two-Year Results

Purpose To evaluate the effectiveness and stability of refractive astigmatism reduction after penetrating femtosecond laser-assisted arcuate keratotomy performed at the time of femtosecond laser-assisted cataract surgery. Methods Non-randomized retrospective data analysis of all patients that underwent femtosecond laser-assisted cataract surgery with femtosecond laser-assisted arcuate keratotomy over a 4-year period with a non-toric monofocal intraocular lens (2017–2021) at a tertiary care academic center. Postoperative visual acuity, manifest refraction, and predicted residual refractive error were also recorded at 1 month, 3–6 months, 12–18 months, and 2 years postoperatively. Preoperative keratometric astigmatism was compared to postoperative refractive astigmatism using vector calculations and the ASCRS double-angle plot tool. Results This study comprised 266 eyes (179 patients) that met inclusion criteria. The mean preoperative keratometric astigmatism magnitude was 0.99 ± 0.53 D. At 1 month, 3–6 months, 12–18 months, and 2 years postoperatively, the mean refractive cylinder was 0.49 ± 0.45 D, 0.49 ± 0.45 D, 0.55 ± 0.54 D, and 0.52 ± 0.46 D, respectively. Horizontal against-the-rule astigmatism showed a higher tendency toward undercorrection than vertical with-the-rule astigmatism, which had a slightly higher tendency toward overcorrection. With-the-rule astigmatism had smaller difference vectors between target-induced astigmatism and surgically induced astigmatism. Conclusions Femtosecond laser-assisted arcuate keratotomy performed at the time of femtosecond laser-assisted cataract surgery was an effective option for correcting low-to-moderate corneal astigmatism for up to 2 years.

Comparison of Safety and Efficacy of Four-Point Scleral Intraocular Lens Fixation and the Yamane Technique.

The purpose of our study was to compare the safety and efficacy of two scleral fixation intraocular lens (IOL) methods of four-point scleral fixation (Akreos AO60) and the Yamane technique (AcrySof MA60AC). This prospective, randomized study was conducted at the Military Institute of Medicine-National Research Institute in Warsaw between 2021 and 2023. We compared both groups for cause of aphakia, ocular history, refractive status, and complication. Our study included 50 eyes from 47 patients. Four-point fixation was performed in 25 eyes (group1), and the Yamane technique was used in 25 eyes (group2). Surgical time was 24.1min ± 8.9 in group1 and 25.1min ± 9.9 in group2 (p > 0.05). The postoperative BCVA (best-corrected visual acuity) for group1 and group2 at 1year's observation was 0.10 ± 0.15 and 0.09 ± 0.17 logMAR, respectively (p > 0.05). Postoperative total refractive error (RE) was - 0.06 ± 0.71 diopters (D) for four-point scleral fixation and 0.83 ± 0.70D for Yamane technique (p < 0.05). Endothelial cell density (ECD) loss was 0.9% in group1 and 3.5% in group2 (p > 0.05). Bleeding into the anterior chamber and vitreous body was more frequent in the group of patients operated on with the use of the Yamane technique (10 cases, 20%, p = 0.01). IOL displacement was found in one case (2%) in group2. Both analyzed techniques are well tolerated and ensure good refractive results (extremely predictable in four-point scleral fixation) and have a similar safety profile. Four-point scleral fixation of IOL would appear to be safe, effective and beneficial for young, active patients, especially after trauma or recurrent subluxation. ClinicalTrials.gov identifier NCT06389643.

Rapid survey for assessing effective cataract surgical coverage (eCSC) and effective refractive error coverage (eREC)-Novel indicators of universal eye health.

As per the recent World Health Organization estimates, approximately 2.2 billion people have near and distance vision impairment (VI) globally, and out of this almost 50% is avoidable. The Rapid Assessment of Avoidable Visual Impairment survey was a cross-sectional study conducted in September 2021, using cluster random sampling in 42 clusters with a cluster size of 140, giving a total of 6000 participants. Two teams comprising of trained optometrists and social workers conducted the ocular examination which included unaided, pinhole, and aided visual acuity assessments followed by examination of the anterior segment and lens. Distance visual acuity was measured using simplified tumbling "E" charts of different sizes for VA of 6/12, 6/18, and 6/60. The lens assessment was done in an un-dilated pupil with torch light by the optometrist. Overall, 6520 individuals aged 6 years and above were enumerated, of whom 5440 (83.4%) were examined. The response rate for examination was better among females (93.1%) than males (73.9%), and it decreased from 93.8% in the age group 6-15 years to 77.1% in the 45+ age group. The prevalence of blindness and VI were 0.18% (95% CI: 0.06-0.29) and 4.19% (95%CI: 3.65-4.72), respectively. The major causes of VI in all age groups were uncorrected refractive error (65.4%), cataract (23.7%), cataract surgical complications (2.6%), corneal opacity (0.4%), and other posterior segment diseases (7.5%). The effective cataract surgical coverage (eCSC) was 61.8%, effective refractive error coverage (eREC) for distance vision was 59.8%, and eREC for near vision was 47.0%. The RAAVI methodology is suitable to measure effective coverage in the general population, both for baseline measurement and periodic monitoring. The 2030 targets for the surveyed district are 90% eCSC and 100% eREC. Such exercises need to be conducted in each district of the country to determine the baseline and target values of effective coverage.

Effective optical zone: Differences between small-incision lenticule extraction and femtosecond LASIK for myopia.

To compare the effective optical zones (EOZs) of small-incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (F-LASIK) by utilizing topographic methods on the tangential curvature difference map at postoperative 1 year and to identify parameters linked to the EOZ alterations following both surgeries. Myopic patients who underwent SMILE or F-LASIK were included in the study. Patients with refractive error greater than -9.0 D sphere or -0.50 D of astigmatism were excluded from the study. EOZs were measured at postoperative 1 year by using the tangential curvature difference map of the Scheimpflug tomography system. Correlations between the EOZ alterations and relevant parameters were assessed. In total, 59 eyes in the SMILE group and 65 eyes in the F-LASIK group were assessed. The decrease in EOZ compared with the programmed optical zone was significantly higher in the F-LASIK group ( P < 0.001). The increase in corneal asphericity was significantly relevant to the decrease in EOZin both groups according to the multiple regression analysis ( P < 0.001, B/95% CI: 0.62/0.34 and 0.90, standardized-Beta: 0.587 for the SMILE group; P < 0.001, B/95% CI: 0.74/0.41 and 1.07, standardized-Beta: 0.631 for the F-LASIK group). The EOZ decreased 1 year after both SMILE and F-LASIK. The SMILE group showed less EOZ reduction than F-LASIK patients relative to the programmed optical zone. The decrease in EOZ was correlated with the increase in corneal asphericity in both groups.

Outcomes of Corneal Compound Myopic Astigmatism with Presbyopia by Zeiss PRESBYOND® Laser Blended Vision LASIK Using Default CRS-Master® Target Refractions for Reduced Anisometropia.

Background/Objectives: Presbyopia, a common age-related refractive error, affects over a billion people globally and significantly impacts daily life. Methods: This retrospective study analyzed 288 eyes of 144 patients undergoing LBV PRESBYOND® treatment for myopic presbyopia with astigmatism, aiming to evaluate precision, efficacy, safety, and stability over six months. Results: Key findings include high efficacy, with 99% of distance-eyes achieving uncorrected distance visual acuity (UDVA) of 20/25 or better, and 85% of near-eyes achieving UDVA of 20/32 or better. The results show excellent refractive outcomes, with 99% of long-sighted eyes and 97% of near-sighted eyes having a postoperative spherical equivalent within ±1.00 D. Safety was demonstrated by no loss of two or more Snellen lines after treatment, with 94% of patients maintaining corrected distance visual acuity (CDVA) before and after surgery. Conclusions: Overall, LBV PRESBYOND® proved effective, safe, and well tolerated for myopic presbyopia correction, offering satisfactory visual outcomes and potential spectacle independence for various distances. This study underscores the importance of individualized treatment based on patient age, highlighting the positive impact of binocular summation on visual function. This study contributes to the growing body of evidence supporting LBV PRESBYOND® as a viable option for addressing presbyopic myopia, offering insights into its efficacy and safety profile. Further research could explore postoperative stereopsis and long-term outcomes to enhance understanding and refine treatment protocols.

Visual impairment and associated factors in adults from three suburban communities in Nampula, Mozambique.

Scientific evidence on the burden of visual impairment, its causes, and associated factors are essential to monitor progress in eye health, identify priorities and develop strategies and policies that meet the needs of the population, towards the eradication of preventable blindness. The aim of this study was to determine the prevalence of visual impairment, its causes and associated factors in adults living in suburban communities in Nampula. This is a cross-sectional study conducted from November 2019 to February 2020. Eye examinations were performed on adults aged ≥18 years covered by the Lúrio University program, 'one student, one family'. The odds ratio (OR) and adjusted odds ratio (aOR) were calculated to study the association between the dependent variable (presenting visual impairment) and independent variables (gender, age, school level, residence, family income and systemic diseases), with a 95% confidence interval. Distance and near presenting visual impairment had a prevalence of 16.3% and 21.1%, respectively, and were statistically associated with the age groups between 45-65 (OR:4.9) and >65 years (OR: 29.1), illiterate (OR:13.8), primary (OR:4.8) and secondary (aOR:37.5) school level, farmer (OR:32.8) and retired (OR:14.3) occupation, and presence of systemic diseases (OR :3.3). The main causes of presenting visual impairment were uncorrected refractive error and cataract. The prevalence of presenting visual impairment is relatively high, given the enormous effort undertaken within the framework of VISION 2020: The Right to Sight global initiative. There is a need to develop intervention plans targeted at the highest risk groups, with a view to achieving the 'one student, one family' program goals with respect to eye health.

Underwater Camera Calibration Based on Double Refraction

Underwater camera calibration plays a pivotal role in underwater positioning and underwater mapping reconstruction, making it crucial for achieving precise spatial measurements in underwater environments. To elevate measurement accuracy, we have refined the calibration methodology for underwater cameras. Firstly, we conducted an in-depth investigation into the intricate challenges posed by double refraction errors arising from light passing through water–glass–air interfaces. To address this issue, we established a double refraction model based on the actual underwater light paths, laying the groundwork for our calibration efforts. Furthermore, to tackle the problem of determining multiple camera parameters, we proposed a parameter optimization method based on genetic algorithms, capable of navigating the complex parameter space. Finally, compared with other algorithms, our method enables more precise determination of underwater camera parameters.

Prevalence of visual impairment and estimation of refractive errors among school children in Kakamega, Kenya.

To investigate the prevalence of visual impairment (VI) and provide an estimation of uncorrected refractive errors in school-aged children, conducted by optometry students as a community service. The study was cross-sectional. Totally 3343 participants were included in the study. The initial examination involved assessing the uncorrected distance visual acuity (UDVA) and visual acuity (VA) while using a +2.00 D lens. The inclusion criteria for a subsequent comprehensive cycloplegic eye examination, performed by an optometrist, were as follows: a UDVA<0.6 decimal (0.20 logMAR) and/or a VA with +2.00 D ≥0.8 decimal (0.96 logMAR). The sample had a mean age of 10.92±2.13y (range 4 to 17y), and 51.3% of the children were female (n=1715). The majority of the children (89.7%) fell within the age range of 8 to 14y. Among the ethnic groups, the highest representation was from the Luhya group (60.6%) followed by Luo (20.4%). Mean logMAR UDVA choosing the best eye for each student was 0.29±0.17 (range 1.70 to 0.22). Out of the total, 246 participants (7.4%) had a full eye examination. The estimated prevalence of myopia (defined as spherical equivalent ≤-0.5 D) was found to be 1.45% of the total sample. While around 0.18% of the total sample had hyperopia value exceeding +1.75 D. Refractive astigmatism (cil<-0.75 D) was found in 0.21% (7/3343) of the children. The VI prevalence was 1.26% of the total sample. Among our cases of VI, 76.2% could be attributed to uncorrected refractive error. Amblyopia was detected in 0.66% (22/3343) of the screened children. There was no statistically significant correlation observed between age or gender and refractive values. The primary cause of VI is determined to be uncorrected refractive errors, with myopia being the most prevalent refractive error observed. These findings underscore the significance of early identification and correction of refractive errors in school-aged children as a means to alleviate the impact of VI.