Nishanth, M (2012) Corneal Characteristics in Myopic Patients. Masters thesis, Aravind Eye Hospital and Post Graduate Institute of Ophthalmology, Madurai.
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Abstract
INTRODUCTION: Myopia is a significant public health problem, affecting 33% of individuals over the age of 12 years in the United States and a much higher percentage in parts of Asia such as Taiwan and Singapore and the prevalence may be increasing over time. Single vision spectacle lenses and contact lenses are commonly prescribed for myopia and more recently refractive surgery has become a popular option. While these treatments correct the myopic refractive error, they do not slow the accompanying eye growth or retard the physiological changes associated with excessive axial elongation. The World Health Organization has set a goal to eliminate preventable blindness in the world by the year 2020, with refractive error, including myopia, as one of its top five priorities. The high prevalence of myopia and its prominence as a public health problem emphasize the importance of gaining increased understanding of the mechanisms of eye growth and of finding effective treatments that slow progression and axial elongation. AIM AND OBJECTIVE: To evaluate corneal and refractive characteristics of Indian myopic patients seeking refractive surgery at a tertiary care eye centre. MATERIALS AND METHODS: Study Design: A retrospective study of 910 eyes in 455 patients who were screened by Orbscan topography (Bausch and Lomb) before undergoing myopic refractive surgery (LASIK / ZYOPTIX) from April 2011 to October 2011 in Aravind Eye Hospital, Madurai. Inclusion crIteria: • Age group between 21-40 years both male and female. • Myopia with at least-0.25 sphere and astigmatism of-0.25 cylinder. • Refractive power has been constant for at least 1 year. • Cylindrical power not more than 5 D. Exclusion Criteria: • Keratoconus / subclinical/ Forme Fruste. • Ocular surface disease including severe dry eye. • Other Ethnic groups. METHODOLOGY: • A detailed history is taken, including history of contact lens wear. • Undilated subjective refraction and auto refractometry is done. • A complete pre-operative work up is done in all patients including slit lamp- bio microscopy. • Schirmer’s 1 test in Contact Lens wearers and symptomatic patients to rule out dry eye. • The Orbscan Topography (Bausch & Lomb) was used to evaluate the corneal diameter, corneal curvature, corneal thickness, angle kappa and AC depth. • An Indirect Ophthalmoscopic examination was done with a dilated pupil for periphery examination of the posterior segment. • A dilated subjective refraction is done. • If all parameters are normal, the patients is advised LASIK. CONCLUSION: Characteristics of cornea in a sample of an Indian population showed. • The percentage of females was marginally more than males with the percentage of 53% to 47% respectively. • The results showed that 61.3% of the people were in the age group from 21-25 years. • 35% of people had mild (<3D), 53% of the people had moderate (3- 6D) and 12% of the people had severe (>6D) refractive error. • The mean manifest refraction (spherical equivalent) was 3.90D±2.28 diopters (ranging from -0.25 to -14.00D). • K- Maximum had a Mean (SD) of 44.52 D ±1.34 D ranging from 41.0 D to 48.1 D. • K- Minimum had a Mean (SD) of 43.62 D ±1.29 D ranging from 40.2 D to 47.5 D. • Mean (SD) of the corneal diameter is 11.75± 0.4mm ranging from 10.6mm to 13mm. • Mean (SD) of AC depth is 3.04± 0.27mm ranging from 2.27mm to a Maximum of 3.74mm. • The Mean (SD) of the thickness of the corneal is 557.43±29.72μm and the range is a Minimum of 496μm to a Maximum of 665μm. • The thinnest areas of the cornea were found to be predominantly temporal with 21%, followed by Infero-temporal and Supero-temporal with 18%. • There was no statistically significant difference between the findings of the right and left eye. A larger population based study may help us to further understand the corneal characteristics of Indian population. This has important implication in surgical planning and this will enable the surgeon to screen patients more appropriate both for LASIK and for Phakic IOL’s.
| Item Type: | Thesis (Masters) |
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| Uncontrolled Keywords: | Corneal Characteristics, Myopic Patients. |
| Subjects: | MEDICAL > Ophthalmology |
| Depositing User: | Subramani R |
| Date Deposited: | 18 Jun 2020 12:35 |
| Last Modified: | 18 Jun 2020 12:35 |
| URI: | http://repository-tnmgrmu.ac.in/id/eprint/12497 |
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