Myopia In Asian Countries Health And Social Care Essay

Vision consequences from entryway of visible radiation into the oculus and the reading of this stimulation by the encephalon. For a normal oculus, visible radiation is focused to a topographic point on the retina. This message would so be sent to the encephalon to be interpreted as a message. Ocular sharp-sightedness is defined as the lucidity or acuteness of vision, which is the ability of the oculus to see and separate mulct inside informations. [ 1 ] .

The cornea is the most powerful refracting surface of the optical system of the oculus, accounting for two-thirds of the oculus ‘s focusing power. Production of a crisp image at the retinal receptors requires corneal transparence and appropriate refractile power. The refractile power of the cornea depends on its curvature and the difference in refractile indexes between it and air [ 9 ] . Refractive mistakes occur when the curve of the cornea is irregularly shaped ( excessively steep or excessively level ) . When the cornea is of normal form and curvature, it bends, or refracts, visible radiation on the retina with preciseness. However, when the curve of the cornea is irregularly shaped, the cornea bends light amiss on the retina.A [ 15 ]

When the cornea is curved excessively much, or if the oculus is excessively long, far-off objects will look blurry because they are focused in forepart of the retina. This is called nearsightedness, or nearsightedness. Hyperopia, or presbyopia, is the antonym of nearsightedness. Distant objects are clear, and close-up objects appear blurry. With hypermetropia, images focus on a point beyond the retina. Hyperopia consequences from an oculus that is excessively short. Astigmatism is a status in which the uneven curvature of the cornea fuzzs and distorts both distant and close objects. A normal cornea is round, with even curves from side to side and exceed to bottom. With astigmia, the cornea is curved more in one way than in another. This causes light beams to hold more than one focal point and concentrate on two separate countries of the retina, falsifying the ocular image. [ 15 ]

Measurement of corneal curvature/power can be performed with a assortment of instruments, most normally aA keratometer, A IOLMaster, orA corneal topographyA device. Corneal curvature is normally used forA IOLA computations and cornealA refractile surgery. It is besides helpful for contact lens fitting and observing irregular astigmia. [ 5 ]

The primary purpose of this survey is to look into the relationship between corneal curvature and grade of refractile mistake among emmetropic and myopic immature population in Malaysia and to find the standard value of corneal curvature of immature population.

1.2 Research inquiry

Question 1:

Does corneal curvature vary significantly with different province of refractile mistake?

Question 2:

What are the scope of readings of corneal curvature of emmetropic and myopic immature topics?

Question 3:

Is there any different between horizontal and perpendicular curvature of the cornea?

1.3 Aims of the survey

1.3.1 General aim

The general aim of this survey is to look into the relationship between corneal curvature and refractile position among emmetropic and myopic immature patients in IIUM Kuantan Campus.

1.3.2 Specific aims

To find whether corneal curvature varies significantly with refractile mistake.

To compare the readings of corneal curvature between emmetropic and myopic immature topics.

To place the normal scope of corneal curvature for emmetropic and myopic immature topics.

To place whether there is any different between horizontal and perpendicular curvature of the cornea.

To look into the function of corneal curvature in refractile province among Malayan population.

Hypothesis of the survey

There is no important relationship between corneal curvature and refractile position.

Chapter 2

LITERATURE REVIEW

2.1 Prevalence of nearsightedness in Asiatic states

National Eye Survey done in Malaysia [ 2,3 ] found the prevalence of ocular damage was 2.7 % . The prevalence was higher in rural countries ( 2.9 % ) as compared to urban countries ( 2.5 % ) . The prevalence of ocular damage in rural population in Selangor has been reported to change from 5.6 % to 18.9 % in which they found that among the patients go toing the Eye Clinic at University Malaya Medical Centre, the most common cause of ocular damage in kids was refractile mistakes, whereas in aged patient ocular damage is due to cataract, glaucoma and diabetic retinopathy. [ 4 ]

Myopia is a common cause for ocular damage among immature population in Asia. Estimates of the proportion of nearsightedness in the immature population in Asia ranged from 30 % to 65 % ( Saw et al. 1996 ; Chow et al. 1990 ) , and the prevalence was found to be greater among Chinese people ( Wensor et al. 1999 ; Sperduto et Al. 1983 ) . In Malaysia, the prevalence of nearsightedness found among Malay, Chinese and Indian schoolchildren was 47 % , 20 % and 19.4 % severally ( Garner et al.1990 ; Chung et Al. 1995 ; Saadah et Al. 2002 ) . With the increasing rates of nearsightedness, orthokeratology and refractile surgery such as LASIK, has become rather popular in Asia. When set abouting such processs to rectify nearsightedness, corneal curvature is an of import consideration in order to forestall the cornea from going excessively level after the intervention. [ 6 ]

2.2 The importance of corneal curvature

Corneal curvature is normally used forA IOLA computations and cornealA refractile surgery. It is besides helpful for contact lens fitting and observing irregular astigmia ( Friedman, 2009 ) . Measurements of cardinal and peripheral corneal curvature are utile for naming and supervising corneal conditions such as keratoconus and for supervising corneal form following optic surgery6-10 or refractile processs such as orthokeratology. [ 13 ]

Liu Z. , Pflugfelder SC, ( 2000 ) studied on the effects of long-run contact lens wear on corneal thickness, curvature, and surface regularity. They found that the corneal curvature, maximal keratometry ( Max K ) and minimal keratometry ( Min K ) readings, were significantly steeper in eyes have oning contact lenses than normal eyes ( PA & lt ; 0.01 for Max K and Min K measured by both instruments ) .

In foregrounding the importance of corneal curvature in IOL computations, Schena LB ( 2008 ) cited from Dr. Majmudar, in patients who have non undergone old surgery, the value at the centre of the cornea is approximately the same as the value at 3.2 millimetres ( based on keratometer measurings ) . However, patients who have undergone LASIK or PRK can hold altered corneas, and the value at the cardinal cornea, which is the end of measuring, may be really different from that at 3.2 millimetres. Consequently, if testers merely rely on the topography, they may be off, and for every 1 dioptre off in mensurating the corneal curvature, a approximately 1 dioptre misreckoning will ensue for the patient ‘s refractile result. [ 11 ]

Besides that, keratometry plays a critical function in the truth of IOL power computation by observing and mensurating astigmia by finding the steepest and flattest acmes of the corneal surface.A [ 16 ]

Keratometry plays a critical function in the truth of IOL power computation, observing and mensurating astigmia by finding the steepest and flattest acmes of the corneal surface.A Keratometry plays a critical function in the truth of IOL power computation, observing and mensurating astigmia by finding the steepest and flattest acmes of the corneal surface.A Keratometry plays a critical function in the truth of IOL power computation, observing and mensurating astigmia by finding the steepest and flattest acmes of the corneal surface.A Keratometry plays a critical function in the truth of IOL power computation, observing and mensurating astigmia by finding the steepest and flattest acmes of the corneal surface.A Dr. Majmudar explained that keratometers measure the curvature of the anterior surface about 3.2 millimeter from the centre of the cornea. “ In patients who have non undergone old surgery, the value at the centre of the cornea is approximately the same as the value at 3.2 millimetres, ” he said. “ However, patients who have undergone LASIK or PRK can hold altered corneas, and the value at the cardinal cornea, which is the end of measuring, may be really different from that at 3.2 millimetres. Consequently, if you merely trust on the topography, you may be off, and for every 1 dioptre you are away in mensurating the corneal curvature, a approximately 1 dioptre misreckoning will ensue for the patient ‘s refractile outcome. ” Dr. Majmudar explained that keratometers measure the curvature of the anterior surface about 3.2 millimeter from the centre of the cornea. “ In patients who have non undergone old surgery, the value at the centre of the cornea is approximately the same as the value at 3.2 millimetres, ” he said. “ However, patients who have undergone LASIK or PRK can hold altered corneas, and the value at the cardinal cornea, which is the end of measuring, may be really different from that at 3.2 millimetres. Consequently, if you merely trust on the topography, you may be off, and for every 1 dioptre you are away in mensurating the corneal curvature, a approximately 1 dioptre misreckoning will ensue for the patient ‘s refractile outcome. ” Dr. Majmudar explained that keratometers measure the curvature of the anterior surface about 3.2 millimeter from the centre of the cornea. “ In patients who have non undergone old surgery, the value at the centre of the cornea is approximately the same as the value at 3.2 millimetres, ” he said. “ However, patients who have undergone LASIK or PRK can hold altered corneas, and the value at the cardinal cornea, which is the end of measuring, may be really different from that at 3.2 millimetres. Consequently, if you merely trust on the topography, you may be off, and for every 1 dioptre you are away in mensurating the corneal curvature, a approximately 1 dioptre misreckoning will ensue for the patient ‘s refractile outcome. ” Dr. Majmudar explained that keratometers measure the curvature of the anterior surface about 3.2 millimeter from the centre of the cornea. “ In patients who have non undergone old surgery, the value at the centre of the cornea is approximately the same as the value at 3.2 millimetres, ” he said. “ However, patients who have undergone LASIK or PRK can hold altered corneas, and the value at the cardinal cornea, which is the end of measuring, may be really different from that at 3.2 millimetres. Consequently, if you merely trust on the topography, you may be off, and for every 1 dioptre you are away in mensurating the corneal curvature, a approximately 1 dioptre misreckoning will ensue for the patient ‘s refractile outcome. ” Dr. Majmudar explained that keratometers measure the curvature of the anterior surface about 3.2 millimeter from the centre of the cornea. “ In patients who have non undergone old surgery, the value at the centre of the cornea is approximately the same as the value at 3.2 millimetres, ” he said. “ However, patients who have undergone LASIK or PRK can hold altered corneas, and the value at the cardinal cornea, which is the end of measuring, may be really different from that at 3.2 millimetres. Consequently, if you merely trust on the topography, you may be off, and for every 1 dioptre you are away in mensurating the corneal curvature, a approximately 1 dioptre misreckoning will ensue for the patient ‘s refractile result. “ Top of Form

Bariah et Al. ( 2009 ) suggested that every demographic has a different norm and scope of corneal curvature values and its relationship to the grade of nearsightedness among normal population.

2.3 Corneal curvature in hyperope, emmetrope and myope

In research by Bariah et Al. ( 2009 ) , consequences from keratometer measuring indicated that the mean of corneal curvature for the all myopic immature topics was 7.74 A± 0.52 millimeter, with 7.87 A± 0.28 millimeter for Chinese topics and 7.60 A± 0.66 millimeter for Malays.

In survey by Mainstone JC et Al ( 2010 ) , the correlativity between corneal radius of curvature and spherical equivalent refractile mistake was non statistically important ( r2 = 0.038, p =0.2609 ) . A antecedently study by Carney LG et Al. showed that there is a inclination for the cornea to flatten less quickly in the fringe with increasing nearsightedness. This suggests that there are corneal form alterations that occur in nearsighted eyes, possibly as a consequence of unnatural optic growing, that are non seen in hypermetropic eyes because a different mechanism of refractile mistake development operates in this latter group. However, a research by Bariah et Al ( 2009 ) with average refractile mistake in spherical equivalent was -3.50 A± 2.10 DS, they found that there is hapless correlativities between myopic refractile mistake and corneal curvature ( r = 0.246, P & gt ; 0.05 ) .

On the other manus, a recent survey by Iyamu E et Al. ( 2010 ) on a Nigerian population found that there was a important positive correlativity between corneal curvature and spherical tantamount refraction. ANOVA showed that the difference in average corneal curvature across the refractile position groups was statistically important ( F = 27.9, df = 2, 67, P & lt ; 0.0001 ) . Post hoc trial with Fisher ‘s LSD showed that myopes had steeper corneas than the other two groups ( steeper by 0.27 millimeters than that of hyperopes, and 0.28 millimeter than that of emmetropes ) . The additive arrested development theoretical account is represented by: CRC = 7.853 + 0.069SER. From the equation it can be predicted that for every 1.00D addition in nearsightedness, the cornea is steepened by about 0.07 millimeters.

2.4 Measuring corneal curvature utilizing PentacamA®

The Pentacam has become a popular clinical device for measuring the anterior section of the oculus since its launch in 2004. It contains a Scheimpflug camera that rotates through 360 grades and captures 25 or 50 Scheimpflug slit images within two seconds. Each image shows a cross-section of the cornea and the anterior section. The images contain 500 informations points and up to 25,000 points ( 50 slits A? 500 informations points ) are measured to assorted parametric quantities and to build a 3-dimensional cornea. The Pentacam is capable of mensurating topographic corneal thickness, anterior and posterior corneal topography, anterior chamber deepness and angle and corneal aberrances. It besides provides parametric quantities such as corneal volume and keratometric power difference, which offer new and proficient analyses of the cornea, severally. [ 13 ]

For historical grounds, most Placido topographers and keratometers use the refractile index of 1.3375 for the refractile power of the cornea. This refractile index is really wrong even for the untreated oculus ( n~1,332 ) and assumes a changeless ratio between the front tooth and posterior curvature of the cornea. As many IOL power computation expressions use the wrong ‘K-reading ‘ straight an empirical rectification is needed in the terminal to set the correct IOL power in these expressions even in normal instances. [ 12 ]

In a survey by Chen D. et Al, the Pentacam system was shown to be extremely dependable in the Sim K measurings, at both the front tooth and posterior corneal surfaces ( Cronbach ‘s alpha trial, I± a‰? 0.990 ; intraclass correlativity coefficient, ICC a‰? 0.972 ) .

The Orbscan is another normally used corneal topographer. It is based on a intercrossed system integrating both the Placido phonograph record and scanning slit rules. Similar to the Pentacam, the Orbscan is non-invasive, simple to utilize and quick, nevertheless, old surveies found the Orbscan to hold questionable public presentation in topographic pachymetry and in the rating of anterior21 and posterior corneal curvatures. [ 14 ]

Chapter 3

MATERIALS AND METHODS

Study country

Location of survey is at Clinic of Optometry International Islamic University Malaysia, Kuantan.

3.2 Study design

The survey is an experimental case-control survey. The parametric quantities for the collected informations will be performed on both eyes. Data will be collected from each topic on a individual visit.

3.3 Subject of the survey

3.3.1 Sampling of the survey

Sampling of the survey is convenient trying. Subjects who fulfilled the inclusion standards for the survey are invited to take part in the survey.

Sample size

The sample size will be based on the survey by Bariah et Al ( 2009 ) “ Corneal Thickness and Curvature of One Sample of Young Myopic Population in Malaysia ” where the topics consisted of 84 myopic university. Should mention the latest paper with groups comparison “ Ocular Dimensions of Young Malays in Malaysia ” ( Bariah Mohd-Ali, and Muhammad Afzam Shah Abdul-Rahim, and Zainora Mohammed, and Norhani Mohidin, ( 2011 ) Ocular dimensions of immature Malayans in Malaysia. Jurnal Sains Kesihatan Malaysia, 9 ( 1 ) . pp. 35-39. ISSN 1675-8161.

On the sample size computation, refer to relevant old paper and enter the respective values ( mean, standard divergence etc. ) in this web site:

hypertext transfer protocol: //www.stat.ubc.ca/~rollin/stats/ssize/n2.html

Sample of the survey

Sample of the survey comprised of groups of emmetropic and myopic immature topics.

Subject ‘s inclusion standards

Age between 20 to 26 old ages old.

VA at distance 6/6 or better.

VA at near N5 at 33 centimeter or better.

Refractive power between +0.50 DS to -0.50 DS and a‰? – 2.00 Darmstadtium

Non-contact lens wearer. Soft contact lens wearer less than 5 old ages are permitted provided lenses were non worn on the twenty-four hours of proving

Good optic wellness tested with slit lamp and fundus scrutiny.

Good general wellness taken from self-report.

Subject ‘s exclusion standards

Rigid contact lens wearer

History of corneal abnormalcy, refractile surgery or orthokeratology intervention.

3.4 Study tools and process

Within survey sites, clinical scrutinies are by and large performed at one location ( IIUM Optometry clinic ) . Before clinical eyes scrutiny is performed on the participant, they will be asked for a complete personal and household general wellness and oculus wellness history. Later, participants underwent an extended and standardised scrutiny process, which included ocular sharp-sightedness ( VA ) testing, refraction and a elaborate optic slit lamp and fundus scrutiny

The ocular Acuity ( VA ) will be measured utilizing a Snellen chart at 6m. Measurement of refractile position will be conducted utilizing subjective refraction with cross cylinder. Subjects were categorized into emmetropia, hypermetropia and nearsightedness utilizing the spherical tantamount refraction. Classification was done based on: Emmetropia a‰¤A± 0.50DS and Myopia a‰? 2.00DS. Following, measuring of corneal curvature will be taken utilizing Pentacam ( Oculus, Inc. , Germany ) . Average corneal curvature ( AVK ) was obtained by the norm of the horizontal and perpendicular corneal curvature. Finally, the external oculus and anterior section ( eyelid, conjunctiva, cornea, flag, and student ) will be examined with slit lamp, and followed by scrutiny of media and fundus utilizing indirect opthmoscopy and fundus camera.

3.5 Data analysis

The natural informations are keyed in and organized utilizing statistical package SPSS ( Statistical Package for Social Science ) version 17.0. The information will be analyzed utilizing the same package. Statistical analyses being employed are:

Normality trial on each information set utilizing Histogram.

important degree: 0.05 for 95 % CI

Descriptive analysis ( average, standard divergence, average and frequence ) .

One-way analysis of discrepancy ( ANOVA ) will be used to compare the average corneal radius of curvature across the refractile position groups

The relationships among parametric quantities will be tested utilizing Pearson ‘s correlativity and additive arrested development analysis.

3.6 Ethical consideration

Ethical blessing will be acquired from the ethical commission of Kulliyyah of Medicine, International Islamic University Malaysia ( IIUM ) . Engagement in this survey is on a voluntary footing and participants will be asked to subscribe the consent signifier if they agree to take part in this survey.

A written consent will be acquired prior to informations aggregation ( Appendix B ) . In this consent signifier, campaigners will be informed that they will move as ‘subject ‘ in this survey. Participants will be given account on the processs involved in this survey before informations aggregation is performed.The process is considered safe because it is non-invasive. Furthermore, the participants ‘ informations is confidential to public. Any inquiry from the topic will be answered consequently. Participants may besides retreat from this survey at any clip.