ASSOCIATION OF MYOPIA WITH RNFL MEASUREMENTS AS DETERMINED BY OCT Dr Nutan Darda,Dr Ravi Chandil, Dr B K Jain Sadguru Netra Chikitsalaya
INTRODUCTION Optical Coherence Tomography (OCT) is non invasive, non contact technique of measuring thickness of Retinal Nerve Fibre Layer (RNFL). Myopia has been reported as a risk factorfor glaucoma and myopic fundus changes may complicate glaucoma diagnosis and management.
PURPOSE To assess whether increasing axial myopia is correlated with thinner RNFL measurements.
MATERIALS AND METHODS INCLUSION CRITERIA • Myopic patient > 18 years of age, without other ocular pathology. • Corrected intra ocular pressure less than 21mm Hg. EXCLUSION CRITERIA • Family History of glaucoma History of intraocular surgery. PARTICIPANTS 30 eyes of 30 consecutive myopic patients were included in the study.
MATERIALS AND METHODS • Appearance of Optic Disc was documented by slit lamp biomicroscopy. • An OCT examination of the peripapillary RNFL was done by taking fast RNFL scans using OPTOVUE RTVue 100 –OCT by a single operator.
MATERIAL AND METHODS STATISTICAL ANALYSIS T-Test and analysis of variance were used to determine significant association between RNFL thickness with • sex • peripapillary atrophy(ppa) • optic disc tilt P value of less than 0.05 was considered to be statistically significant. Linear regression analysis was applied to find the correlation between RNFL thickness with age spherical correction i.e. Myopia.
RESULTS AGE - mean age 34.0 years( 19 TO 54 yrs) MEAN SPHERICAL CORRECTION -5.4D (-2 to-14) SEX
RESULTS . Male variables Mean RNFL p value SEX Female male 96.41 0.247 sex female 100.66 PPA ppa 93.875 0.083 ppa no ppa 100.81 TILT tilt tilt 95.83 0.386 99.75 no tilt
RESULTS • A significant association was found between mean spherical correction and RNFL thickness. • RNFL thickness decreased with higher mean spherical correction. overall RNFL ( r=-0.5610, p=0.001) superior RNFL ( r=-0.4117, p=0.02 ) • inferior RNFL ( r=-0.4517, p=0.01) • RNFL thickness was decreased at superior and inferior poles in myopic subjects. • Nasal and temporal RNFL thickness showed no significant association with myopia.
DISCUSSION • kang SH et al found that myopia affects RNFL thickness distribution. High myopes are likely to exhibits different RNFL distribution pattern. It should be considered in diagnosing Glaucoma. • Christoperkai-Shun Leung et al also found that RNFL measurements vary with refractive error of the eye. The Evaluation of RNFL thickness in evaluation of Glaucoma should always be interpreted. • Kang SH et al Invest Ophthalmol Vis Sci. 2010 Aug;51(8):4075-83. Epub 2010 Mar 17 • Christoperkai- Shun Leung et al Investigative Ophthalmology and Visual Science. 2006;47:5171-5176
CONCLUSION • Thus we can say that there is a negative correlation between Myopia and RNFL thickness. • The current SD OCT normative data may require corrective factors to account for higher refractive error. • This could prevent myopic individuals from being misdiagnosed as glaucoma suspects on basis of SD OCT RNFL scans.
FINANCIAL DISCLOSURE The authors had nil financial interests.