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RAJIV GANDHI UNIVERSITY OF HEALTH SCIENCES BANGALORE PROFORMA FOR REGISTRATION OF SUBJECTS FOR DISSERTATION NAME OF THE CANDIDATE: SONIKA PORWAL DEPARTMENT OF OPHTHALMOLOGY ST JOHN’S MEDICAL COLLEGE SARJAPUR,KORAMANGALA BANGALORE-560034. NAME OF THE INSTITUTION: ST JOHN’S MEDICAL COLLEGE HOSPITAL. COURSE: M.S OPHTHALMOLOGY DATE OF ADMISSION TO COURSE: 1/06/2013 TITLE OF THE THESIS: Correlation of axial length of the eyeball and peripapillary retinal nerve fibre layer thickness measured by Cirrus HD Optical Coherence Tomography in myopes. INTRODUCTION Myopia is one of the most common eye problem in the world. Its association with primary open angle glaucoma is well recognized. The risk of developing glaucoma is 2-3 times higher in myopic individuals than in non-myopic individuals.1However, the clinical diagnosis of glaucoma in such patients is challenging because of the pre-existing myopic changes in the retina and the optic disc.2 Currently, glaucoma is diagnosed by changes in the appearance of the optic disc, retinal nerve fiber layer (RNFL) thickness and visual field changes.3In early glaucoma, structural changes precedes the functional damage. The RNFL thickness measurement is a sensitive predictor of early glaucomatous changes and the extent of RNFL damage correlates with the severity of functional deficit in the visual field.4 However, in myopic eyes, the globe is enlarged with increase in axial length. The axial length affects the RNFL thickness inversely.5 Because of this , glaucomatous changes cannot be easily interpreted in myopic patients, possibly leading to overdiagnosis or under diagnosis of glaucoma. 6.1NEED FOR THE STUDY The relationship between the RNFL thickness and axial length has been investigated by a few studies.However, whether the RNFL thickness varies with the refractive status of the eye remains unclear. It is therefore important to investigate and conclude whether there is any correlation between RNFL measurements and the axial length/refractive error in myopic patients. Considering that the risk of developing glaucoma increases with the severity of myopia, it is important to know the variations in RNFL thickness in patients with myopia to avoid overdiagnosis/under diagnosis of glaucoma. The purpose of this study is to determine the relationship between axial length and the RNFL thickness measured by Cirrus HD OCT in myopic patients. 6.2 REVIEW OF LITERATURE In a study conducted by M J Kim et al on fifty-seven healthy subjects with myopia, aged between 20 and 35 years and with no other known ocular abnormality it was found that the global average RNFL was significantly thinner in the high myopia group than in the low myopia group {107.4mm (SD 7.6) v/s 115.8 (8.5) mm, p=0.029}. For quadrant measures, the RNFL was thicker in the low myopia group than in the moderate and high myopia groups for the superior, nasal and inferior quadrants (all p values <0.020). However, the temporal quadrant was thinner in the low myopia group than in the moderate and high myopia groups (p=0.001).They concluded that although the high myopes had significantly thinner RNFLs in the non-temporal sectors compared with the low myopes, they showed a significantly thicker RNFL in the temporal quadrant.6 Similar studies conducted by Shin Hee Kang et al, Giacomo Savini et al showed that average RNFL thickness decreased with an increase in the axial length in myopia. They also showed that high myopes had thinner RNFLs than did low myopes and showed different topographic profiles, thus concluding that retinal nerve fibre layer thickness is related to refractive error/axial length.5,7 In contrast, study conducted by Hoh et al reported that the mean RNFL thickness did not vary with myopia or axial length.8 6.3 OBJECTIVES OF THE STUDY Primary- To evaluate the peripapillary retinal nerve fiber layer (RNFL) thickness by Cirrus HD optical coherence tomography (OCT) in myopes. Secondary- Correlation of axial length and peripapillary RNFL thickness in myopes. 7.0MATERIALS AND METHODS 7.1 SOURCE OF DATA –Patients with myopia attending ophthalmology OPD at St.Johns Medical College Hospital, Bangalore from October 2013 to April 2015 for refractive error evaluation. TYPE OF STUDY – Cross sectional study. PROPOSED SAMPLE SIZE- 45 To observe correlation co-efficient of 0.6 between axial length and RNFL thickness a sample size of 14 subjects should be observed. To perform this comparison within 3 different myopia categories sample size required would be 45. The power and level of significance considered as 80% and 5% respectively. INCLUSION CRITERIA All myopes presenting to the Department of Ophthalmology at SJMCH between the ages of 21 years to 50 years from October 2013 to April 2015 with the consent of the patients. EXCLUSION CRITERIA 1) Those with best corrected visual acuity <20/20. 2) Those with a history of severe ocular trauma, intraocular or refractive surgery, or any ocular or retinal diseases that could have affected the optic nerve head or RNFL like Diabetic Retinopathy, Hypertensive Retinopathy, Age related macular degeneration and others. 3) Diagnosed cases of glaucoma or those with intraocular pressure (IOP) >21 mm Hg in either eye; those showing evidence of a reproducible Visual field defects in either eye, as detected using the Humphrey Visual Field analyzer . 4) Those with history of neurological diseases that could have affected the optic nerve head or RNFL. 7.2 METHOD OF COLLECTION OF DATA Patients with myopia attending ophthalmology OPD at St.Johns Hospital Bangalore from October 2013 to April 2015. Informed consent will be taken. A detailed history including demographics, ocular disease, past medical and surgical history, drug history and personal history will be taken. Ophthalmological examination will include: - Visual acuity (best corrected): using modified Bailley and love chart. - Near vision with Times New Roman chart -Colour vision with Ishihara’s chart. -Fundus evaluation using direct ophthalmoscope and indirect ophthalmoscope. -Refraction. -Intraocular pressure measurement by Applanation tonometer. - A-scan ultrasound biometry (Alcon-ultrascan) software version- 3.00 for determining the axial length. -Visual fields analysis by Humphrey Visual Field analyzer for all patients with cup:disc ratio >0.5. A reliable visual field test will be taken as one with <30% fixation losses,<20% false-positive responses/falsenegative responses. - Retinal nerve fiber layer thickness measured by using Cirrus HD Spectral Domain Optical coherence tomographer (4000-1720) version -5.2.1.2 . It will be performed through a dilated pupil. External fixation will be used and Optic disc cube 200*200 will be obtained. Three of the best obtained scans will be selected. OCT will be repeated when the obtained scans are not appropriate due to poor focusing or inadequate centration. The patient will be excluded if repeat scans are also unsatisfactory. Finally, the selected OCT scans will be analyzed using the Average Retinal Nerve Fiber Layer Thickness program. Mean RNFL thickness will be recorded globally and separately for the superior, inferior, nasal and temporal quadrants. Pearsons correlation analysis will be used to evaluate the correlation between axial length and global RNFL thickness and also with the individual quadrants. 7.3. Does the study require any investigation or intervention to be conducted on patients, other humans or animals? The examination and investigations to be conducted on the patients are a part of investigations required for high myopes and those for low myopes would not be charged. 7.4 .Has the ethical clearance being obtained from your institution? Yes 8.0 REFERENCES 1. Mitchell P, Hourihan F, Sandbach J, et al. The relationship between glaucoma and myopia: the Blue Mountain Eye Study. Ophthalmology. 1999;106:2010–2015. 2. Melo GB, Libera RD, Barbosa AS, et al. Comparison of optic disk and retinal nerve fiber layer thickness in nonglaucomatous and glaucomatous patients with high myopia. Am J Ophthalmol 2006;142:858–60. 3. George A,F Jane Durcan, Christopher A, Gupta N , et al. Open angle glaucoma.Glaucoma.Vol.10. San Francisco :American Academy of Ophthalmology. Series;2013-2014. P.82,83. 4. Quigley HA, Katz J, Derick RJ, et al. An evaluation of optic disc and nerve fiber layer examinations in monitoring progression of early glaucoma damage. Ophthalmology. 1992;99:19 –28. 5. Shin Hee Kang, Seung Woo Hong ,Seong Kyu Im et al. Effect of Myopia on the Thickness of the Retinal Nerve Fiber Layer Measured by Cirrus HD Optical Coherence Tomography.Investigative Ophthalmology & Visual Science, August 2010, Vol. 51 6.M J Kim, E J Lee, T-W Kim et al. Peripapillary retinal nerve fibre layer thickness profile in subjects with myopia measured using the Stratus optical coherence tomography.Br J Ophthalmology 2010;94:115–120. doi:10.1136/bjo.2009.162206 7. GiacomoSavini, PieroBarboni, Vincenzo Parisi et al.Br J Ophthalmol 2012;96:57e61.doi:10.1136/bjo.2010.196782 8. Hoh ST, Lim MC, Seah SK et al. Peripapillary retinal nerve fiber layer thickness variations with myopia.Ophthalmology.2006;113:773-7. 9.0 SIGNATURE OF THE CANDIDATE: 10.0 REMARKS OF THE GUIDE- The importance of the study is already been emphasized in the need for the study. Measurement of RNFL thickness by OCT is used in the diagnosis of many retinal diseases. It is also used in the diagnostic evaluation of glaucoma. Change in the axial length of the eye due to myopia independently affects the RNFL thickness. Therefore it is important to know the correlation of the axial length/myopia with the peripapillary RNFL thickness to prevent overdiagnosis/underdiagnosis of glaucoma . 11.NAME AND DESIGNATION OF GUIDE Dr.ANDREW VASNAIK PROFFESSOR DEPARTMENT OF OPHTHALMOLOGY 11.2 SIGNATURE 11.3 CO-GUIDE Dr.NIBEDITA.ACHARYA ASST. PROFFESSOR DEPARTMENT OF OPTHALMOLOGY 11.4 SIGNATURE 11.7 HEAD OF THE DEPARTMENT DR REJI K THOMAS PROFESSOR AND HEAD DEPARTMENT OF OPHTHALMOLOGY 11.8 SIGNATURE 12.1 REMARKS OF CHAIRMAN AND PRINCIPAL 12.2 SIGNATURE PATIENT INFORMED CONSENT FORM I, ________________________ declare that I have been briefed and hereby in my freewill consent to be included as a subject in the following study – “Correlation of axial length of the eyeball and peripapillary retinal nerve fibre layer thickness measured by Cirrus HD Optical Coherence Tomography in myopes”. I have been informed to my satisfaction by Dr. Sonika.Porwal, the purpose and nature of the study. This has been explained to me in the language I understand best and I fully consent for the same. It has been explained to me that there shall be no change in the standard of care in the course of study and the expression of non-willingness will not change the standard of treatment. Signature of the doctor Signature of the patient Name of the doctor: Name of the patent: Date: PROFORMA FOR THE STUDY: Personal details NameAge/Sex Date Op/Ip n Past history Personal history Family history Drug history Ocular history On examination: 1)Visual acuity UnaidedBCVA 2) Near vision 3) Colour vision- 4) Anterior segment- 5) Fundus examination- direct ophthalmoscope MediaDiscBGR- , CDR- ,vessels- Macula- Indirect ophthalmoscope 5) Refractive correction – 6) IOP – 7) Axial length8) Optical coherence tomography-Peripapillary retinal nerve fiber layer thickness a) average thickness b) quadrants –superior inferior nasal temporal