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Fulltext Spot diagram profile of uncorrected and corrected myopic model eye

Shah Farez Othman, Nizam Tamchek, Farah Diana Muhammad, Shah Farez Othman, Shah Farez Othman, Mohd Hafidz Ithnin

Journal of Optometry, Eye and Health Research, 2020;2(1):34-47.
MyJurnal

Current trend shows that the eye modelling is based on the emmetropic eye taken its ocular optical components value from the population-based studies. However, no studies have been done to study the effect of aberration of myopic refractive error by modelling the eye using the parameters from ocular biometrics and ray tracing method. The objective of the present study was to determine the spot diagram (SPD) profile of myopic refractive error using eye modelling and ray tracing technique. Three eye models had been successfully modeled in Zemax software, namely, emmetropic Liou and Brennan, myopic Liou and Brennan, corrected myopic Liou and Brennan. The optical performance of the eye models were tested using the SPD profile. The ray distribution from the analysis of SPD of myopic Liou and Brennan eye was larger compared to the emmetropic model. In comparison with the emmetropic Liou and Brennan model, for the blue wavelength, the RMS spot radius for the corrected version was increased. However, the RMS values were decreased for green and red wavelengths. For the corrected myopic version of Liou and Brennan, in comparison with its emmetropic model, the Airy disc diameter increased with the increment of wavelengths. It was found that the Airy disc diameter accuracy were higher for the blue, green and red wavelengths. Although the accuracy values were in a positive sign, for Airy disc diameter, the smaller value indicates a diffraction-limited condition.

Matched MeSH terms: Emmetropia
Viewing distance with minimum heterophoria

Chen AH, Aziz A

Clin Exp Optom, 2002 12 17;82(5):182-186.
PMID: 12482277

BACKGROUND: The purposes of this study are to determine the viewing distance with minimum heterophoria and its relationship with refractive error and the resting position of accommodation. METHODS: The heterophoria and the accommodation responses of 36 optometry students (25 emmetropes and 11 myopes) were tested. Heterophoria was measured with the Free-Space Heterophoria Card at five different viewing distances (25 cm, 33 cm, 50 cm, 100 cm and 300 cm). The dioptric viewing distance with minimum heterophoria for each individual was estimated from the graph, where heterophoria in prism dioptres was plotted against viewing distance in centimetres. The Canon R-1 autore-fractor was used to determine the accommodation response at six different viewing distances (25 cm, 33 cm, 50 cm, 100 cm, 300 cm and 600 cm). The resting position of accommodation for each individual was estimated from the graph where the accommodative stimulus in dioptres was plotted against the accommodative response in dioptres. RESULTS: The dioptric viewing distance with minimum heterophoria ranges from 0.003 D to 0.65 D in emmetropes and ranges from 0.03 D to 2.36 D in myopes. There is no difference in the dioptric viewing distance with minimum heterophoria between myopes and emmetropes. Our results show a possible but not significant correlation between the dioptric viewing distance with minimum heterophoria and the resting position of accommodation. CONCLUSIONS: The viewing distance with minimum heterophoria is not affected by refractive error (stable early-onset myopia) and is poorly correlated with the resting position of accommodation.

Matched MeSH terms: Emmetropia
Fulltext Influence of refractive condition on retinal vasculature complexity in younger subjects

Azemin MZ, Daud NM, Ab Hamid F, Zahari I, Sapuan AH

ScientificWorldJournal, 2014;2014:783525.
PMID: 25371914 DOI: 10.1155/2014/783525

The aim of this study was to compare the retinal vasculature complexity between emmetropia, and myopia in younger subjects.

Matched MeSH terms: Emmetropia/physiology*
Fulltext Is emmetropia the natural endpoint for human refractive development? An analysis of population-based data from the refractive error study in children (RESC)

Morgan IG, Rose KA, Ellwein LB, Refractive Error Study in Children Survey Group

Acta Ophthalmol, 2010 Dec;88(8):877-84.
PMID: 19958289 DOI: 10.1111/j.1755-3768.2009.01800.x

PURPOSE: To determine the natural end-point for refractive development during childhood.
METHODS: Cycloplegic (1% cyclopentolate) autorefraction was performed on 38, 811 children aged 5 and 15 in population-based samples at eight sites in the Refractive Error Study in Children (RESC). Refractions (right eye) were categorized as myopic (≤-0.5 D), emmetropic (>-0.5 to ≤+0.5 D), mildly hyperopic (>+0.5 to ≤+2.0 D and hyperopic (>+2.0 D).
RESULTS: At five sites (Jhapa - rural Nepal, New Delhi - urban India, Mahabubnagar - rural India, Durban - semi-urban South Africa and La Florida - urban Chile), there was <20% myopia by age 15. Mild hyperopia was the most prevalent category at all ages, except for Mahabubnagar where emmetropia became the marginally most prevalent category at ages 14 and 15. At the other sites (Gombak - semi-urban Malaysia, Shunyi - semi-rural China and Guangzhou - urban China), there was substantial (>35%) myopia by age 15. At these sites, mild hyperopia was the most prevalent category during early childhood, and myopia became the predominant category later. In Gombak district and Guangzhou, emmetropia was a minor category at all ages, with myopia increasing as mild hyperopia decreased. In Shunyi district, emmetropia was the most prevalent category over the ages 11-14.
CONCLUSION: Emmetropia was not the predominant outcome for refractive development in children. Instead, populations were predominantly mildly hyperopic or substantial amounts of myopia appeared in them. This suggests that mild hyperopia is the natural state of refractive development in children and that emmetropia during childhood carries the risk of subsequent progression to myopia.

Matched MeSH terms: Emmetropia/physiology*
The influence of age, refractive error, visual demand and lighting conditions on accommodative ability in Malay children and adults

Chen AH, Ahmad A, Kearney S, Strang N

Graefes Arch Clin Exp Ophthalmol, 2019 Sep;257(9):1997-2004.
PMID: 31273509 DOI: 10.1007/s00417-019-04405-z

PURPOSE: Near work, accommodative inaccuracy and ambient lighting conditions have all been implicated in the development of myopia. However, differences in accommodative responses with age and refractive error under different visual conditions remain unclear. This study explores differences in accommodative ability and refractive error with exposure to differing ambient illumination and visual demands in Malay schoolchildren and adults.
METHODS: Sixty young adults (21-25 years) and 60 schoolchildren (8-12 years) were recruited. Accommodative lag and accommodative fluctuations at far (6 m) and near (25 cm) were measured using the Grand Seiko WAM-5500 open-field autorefractor. The effects of mesopic room illumination on accommodation were also investigated.
RESULTS: Repeated-measures ANOVA indicated that accommodative lag at far and near differed significantly between schoolchildren and young adults [F(1.219, 35.354) = 11.857, p 0.05). Accommodative lag and fluctuations were greater under mesopic room conditions for all ages [all p

Matched MeSH terms: Emmetropia/physiology*
Fulltext Refractive error status of orang asli and Malay-Jawa children in Kuala Langat, Selangor

Fairuz Mohd Nordin, Khairun Najah binti Hasrin, Mohd Zaki Awg Isa, Amalina Othman, Zurin Firdawani Yacob

Journal of Optometry, Eye and Health Research, 2020;2(1):28-33.
MyJurnal

This study aims to determine the refractive error status of Orang Asli children and Malay-Jawa children in Kuala Langat, Selangor. Visual acuity was measured using LEA chart, followed by dry static retinoscopy which the testing eye fogged with 2.00D, and the contralateral eye fogged with 6.00D to determine the refractive errors. The inclusion criteria encompassed all children in the selected village. The exclusion criteria included children who were already on ophthalmology follow-up for known ocular conditions and refused visual acuity assessment or eye examination. In total, 103 ‘Orang Asli’ and 107 normal population children aged 3 to 13 years received refractive assessments. Approximately 18% of reported cases were myopia, 43% were hyperopia, while 39% were emmetropia. Results showed that the ‘Orang Asli’ population was more hyperopic than the Malay-Jawa (U = 4893.500, P > 0.05, r = 0.14). However, both groups were found more hyperopic compared to myopic conditions. In conclusion, both Orang Asli and Malay-Jawa in Kuala Langat, Selangor are more hyperopic and less myopic. This study suggests that refractive error screening is important for preventing visual impairment among children in rural areas.

Matched MeSH terms: Emmetropia
Refractive and biometric status of children born premature without retinopathy of prematurity

Kaur S, Norlaila Mat Daud, Chung KM, Azrin E. Ariffin, Boo N, Ong LC

Sains Malaysiana, 2010;39.

A cross-sectional study was undertaken to determine the refractive and biometric status of premature children without Retinopathy of Prematurity (ROP) and full term children. Fifty eight children between the ages of 3 and 7 years (32 children born premature without ROP and another 26 children born full term and normal) were examined. Refractive error, corneal curvature, axial length, anterior chamber depth and crystalline lens thickness were determined. The results revealed that children between the age of 3 and 7 years were emmetropic, irrespective of whether they were born premature without ROP or full term. However, children born premature without ROP had significantly steeper corneas (t = 3.14, p = 0.0349), shorter axial lengths (t = 3.18, p = 0.0313) and thicker crystalline lens (t = 3.31, p = 0.0256) compared to children born full term within the same age group. This study suggests that compensation in ocular parameters can occur to maintain emmetropia, mainly by adjustment of axial length and corneal curvature.

Matched MeSH terms: Emmetropia
Fulltext Accommodation response to Chinese and Latin characters in Chinese-illiterate young adults

Radhakrishnan H, Hartwig A, Charman WN, Llorente L

Clin Exp Optom, 2015 Nov;98(6):527-34.
PMID: 26450168 DOI: 10.1111/cxo.12296

BACKGROUND: Differences in accommodation when reading Chinese, as compared to Latin, characters have been suggested to have a role in the higher prevalence of myopia in some Asian countries. Yeo and colleagues (Optom Vis Sci 2013; 90: 156-163) found that, in Chinese-literate children, accommodation was marginally more accurate (by less than 0.05 D), when reading Chinese text. This was attributed to the additional cognitive demand associated with interpreting the more complex Chinese symbols. The present study compared responses to single Chinese and Latin characters, while controlling for cognitive demand.
METHODS: The monocular accommodative response was measured in Chinese-illiterate adults (10 emmetropes, mean spherical equivalent: -0.07 ± 0.42 D, age: 29.9 ± 4.2 years; 11 myopes, mean spherical equivalent: -4.28 ± 2.84 D, age: 31.7 ± 4.6 years) with an open-field autorefractor. Four Chinese and three Latin characters (approximately 1.15 degrees subtense) were individually presented on a display screen one metre away from the subject, while their vergence was varied over the range zero to 5.00 D using spectacle trial lenses. The slope and the accommodative error index (AEI) were calculated from the accommodative stimulus/response curves (ASRC).
RESULTS: No statistically significant differences were found between refractive groups or among characters within the same refractive group in ARSC slopes (Latin: 0.87 ± 0.14 for myopes versus 0.81 ± 0.12 for emmetropes; Chinese: 0.84 ± 0.12 for myopes versus 0.85 ± 0.12 for emmetropes). No significant differences were found between characters in accommodative error index either (Latin, 0.78 ± 0.42 D for myopes versus 1.15 ± 0.72 D for emmetropes; Chinese, 0.74 ± 0.37 D for myopes versus 1.17 ± 0.83 D for emmetropes). However, accommodative error indices and accommodative errors were significantly higher for emmetropes.
CONCLUSION: Under controlled cognitive demand, Chinese and Latin characters elicited similar responses in both individual refractive groups. This study fails to support the hypothesis that development of myopia in some Asian populations is associated with larger lags of accommodation when reading or viewing Chinese characters.
Study site: Manchester, United Kingdom

Matched MeSH terms: Emmetropia/physiology*
Fulltext Distribution of Refractive Errors among Healthy Infants and Young Children between the Age of 6 to 36 Months in Kuala Lumpur, Malaysia-A Pilot Study

Yahya AN, Sharanjeet-Kaur S, Akhir SM

Int J Environ Res Public Health, 2019 11 27;16(23).
PMID: 31783494 DOI: 10.3390/ijerph16234730

Uncorrected refractive error, especially myopia, in young children can cause permanent visual impairment in later life. However, data on the normative development of refractive error in this age group is limited, especially in Malaysia. The aim of this study was to determine the distribution of refractive error in a sample of infants and young children between the ages of 6 to 36 months in a prospective, cross-sectional study. Cycloplegic retinoscopy was conducted on both eyes of 151 children of mean age 18.09 ± 7.95 months. Mean spherical equivalent refractive error for the right and left eyes was +0.85 ± 0.97D and +0.86 ± 0.98D, respectively. The highest prevalence of refractive error was astigmatism (26%), followed by hyperopia (12.7%), myopia (1.3%) and anisometropia (0.7%). There was a reduction of hyperopic refractive error with increasing age. Myopia was seen to emerge at age 24 months. In conclusion, the prevalence of astigmatism and hyperopia in infants and young children was high, but that of myopia and anisometropia was low. There was a significant reduction in hyperopic refractive error towards emmetropia with increasing age. It is recommended that vision screening be conducted early to correct significant refractive error that may cause disruption to clear vision.

Matched MeSH terms: Emmetropia