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00061198-201408000-0000700061198_2014_23_368_costa_megalopapilla_6article< 60_0_6_5 >Journal of Glaucoma© 2014 by Lippincott Williams & Wilkins.Volume 23(6)August 2014p 368–371Optic Disc and Retinal Nerve Fiber Layer Thickness Descriptive Analysis in Megalopapilla[Original Studies]Costa, Alinne Maria Camargos MD; Cronemberger, Sebastião MD, PhDDepartment of Ophthalmology, Federal University of Minas Gerais, Belo Horizonte, BrazilDisclosure: The authors declare no conflict of interest.Reprints: Alinne Maria Camargos Costa, MD, Department of Ophthalmology, Federal University of Minas Gerais, Pernambuco St. 881/801, Belo Horizonte, MG 30130-151, Brazil (e-mail: ).Received December 1, 2011Accepted October 9, 2012AbstractPurpose: To evaluate the optic disc and retinal nerve fiber layer (RNFL) thickness in megalopapilla cases by confocal scanning laser ophthalmoscopy and Stratus optical coherence tomography (OCT). To assess the importance of these measurements in diagnosing megalopapilla.Methods: This study included 59 eyes (30 patients) diagnosed as megalopapilla. All subjects underwent a complete ophthalmic examination that included intraocular pressure and central corneal thickness measurements and standard automated perimetry using the Swedish Interactive Threshold Algorithm and the 24-2 program (Humphrey Field Analyzer; Carl Zeiss Meditec Inc., Dublin, CA). Confocal scanning laser ophthalmoscopy examinations were performed with the Heidelberg retina tomograph (HRTII; Heidelberg Engineering, Germany). Thickness of the RNFL around the optic disc was measured with Stratus OCT, version 4.0.1 (Stratus OCT; Carl Zeiss Meditec). A descriptive analysis was made using SPSS (version 12.0; SPSS Inc., Chicago, IL) statistical software.Results: The mean global optic disc area for all eyes with megalopapilla was 3.28±0.53 mm2 and was not statistically different among races (P≥0.159) or sex (P≥0.108). The average RNFL thickness was 102.5±12.68 μm. Pattern standard deviation was 3.8±2.4 and mean deviation was −1.22±2.65. Central corneal thickness mean value was 543±35.9 μm. Intraocular pressure (average from 3 measurements) ranged from 10.0 to 20.6 mm Hg (14.4±2.7).Conclusions: In megalopapilla, the optic disc is abnormally large. The RNFL thickness is normal. These findings are essential for distinguishing megalopapilla from the optic glaucomatous neuropathy.Megalopapilla or megalodisc is a congenitally anomalous enlarged optic disc with a surface >2.5 mm2.1 It is not associated with any other morphologic anomalies.2 The incidence is unknown. A high prevalence of megalopapilla has been observed in natives of the Marshall Islands.3 This anomaly may have one or both of the following phenotypic features. The first one is a normal configuration with an abnormally large optic disc, usually bilateral and congenital (Fig. 1). There is a large cup/disc ratio and pallor of the disc surface associated with pallor of the neuroretinal rim. This pallor of the neuroretinal rim is due to the presence of axons spread over a large surface. The optic disc cup is usually round or horizontally oval shaped without vessel nasalization at the point of origin (Fig. 2). In the less common second form, the cup is displaced toward the top of the disc, obliterating the adjacent neuroretinal rim.4,5 This congenital abnormality resembles glaucomatous neuropathy and is, in fact, an important differential diagnosis. Indeed, it is a pseudoglaucomatous disc as suggested by Sampaolesi and Sampaolesi.6,7 Megalopapilla does not require treatment.FIGURE 1. Retinography image of megalopapilla.FIGURE 2. Heidelberg retina tomograph image of the right (A) and left (B) megalopapilla. Note the large discs with an area of 4.524 and 5.027 mm2, respectively. The cups are round without notching of the neural retinal rim.Confocal scanning laser ophthalmoscopy and optical coherence tomography (OCT) have provided objective and reproducible measurements that, when used with other clinical information, can assist the clinician in differentiating between normal and glaucomatous eyes.The purpose of this study is to evaluate the optic disc and retinal nerve fiber layer (RNFL) thickness by confocal scanning laser ophthalmoscopy and OCT in megalopapilla cases as well as to assess the importance of the analysis of these structures.METHODSThis is an observational study of 59 eyes of 30 nonconsecutive subjects attending the glaucoma clinic recruited within the staff members of the Faculdade de Medicina, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil between April 2010 and October 2010. The study protocol followed the statements of the Declaration of Helsinki and was approved by local Institutional Review Board and Ethics Committee (ETIC #0642.0.203.000-09). A written informed consent was obtained for all participants before their inclusion in the study.Inclusion criteria were subjects with an optic nerve head (ONH) disc with a surface ≥2.5 mm2, good images on Heidelberg retina tomograph (HRT) as defined by interscan SD of ≤30 μm and willingness to participate in the study. The exclusion criteria were refractive errors exceeding 5.0 D sphere and/or 3.0 cylinder, any media opacity precluding imaging techniques or clinical examination of the disc, and inability to undergo the tests.Patients with megalopapilla underwent a complete ophthalmic examination including biomicroscopy, intraocular pressure (average of 3 measurements) dilated stereoscopic fundus examination, central corneal thickness measurement and standard automated perimetry using the Swedish Interactive Threshold Algorithm and the 24-2 program (Humphrey Field Analyzer; Carl Zeiss Meditec Inc., Dublin, CA). Visual fields were reliable (fixation losses and false-positive and false-negative responses <33%). The stereometric optic disc parameters were evaluated with the HRTII by one the authors (A.M.C.C.), and only discs with a surface ≥2.5 mm2 were studied. All scans had an interscan SD of <30 μm. Scans with poor image quality were excluded. Stratus OCT imaging was performed with dilated pupils also by one the authors (A.M.M.C.). We used the fast RNFL protocol that generates an average of 3 peripapillary circular scans (256 A-scans per 360-degree circular path) with a diameter of 3.46 mm centered on the optic disc. For each subject, RNFL thickness was assessed in 4 retinal regions: temporal, superior, nasal, and inferior. Average RNFL thickness was also assessed. Images presenting RNFL segmentation algorithm failure were excluded. We also excluded images that were obtained during eye movement, that were unfocused, that were poorly centered, or that had signal strength of <6.RESULTSBilateral megalopapilla was found in 59 eyes (30 patients). One patient had unilateral megalopapilla and normal disc size in the fellow eye. The characteristics of the 30 subjects are shown in Table 1. Table 2 shows the stereometric optic disc parameters studied by HRTII with the statistical analysis. Table 3 shows the RNFL thickness studied by Stratus OCT in the temporal, superior, nasal, and inferior regions.TABLE 1 Characteristics of Patients With Megalopapilla (n=30)TABLE 2 Measurements of the Stereometric Parameters of Megalopapilla Studied by the HRTIITABLE 3 Retinal Nerve Fiber Layer Thickness of Megalopapilla Studied by Stratus OCTPattern standard deviation (PSD) was 3.8±2.4 and mean deviation was −1.22±2.65. Central corneal thickness mean value was 543±35.9 μm. Intraocular pressure (average of 3 measurements) ranged from 10 to 20.6 mm Hg (14.4±2.7).DISCUSSIONMegalopapilla is an entity that has been ignored in literature and is not even named in most well-known ophthalmological textbooks.5 Sampaolesi and Sampaolesi studied 33 patients with megalopapilla using the HRT (software 2.12). They compared the stereometric parameters of megalopapilla with those of a normal control group and of a glaucoma group.6 In the megalopapilla group, they found a mean optic disc area of 3.07 mm2, rim area of 1.50 mm2, and cup area of 1.57 mm2. In the glaucoma group, the optic disc area was 2.05 mm2, rim area 0.20 mm2, and cup area 1.80 mm2. The normal group had disc area of 2.05 mm2, rim area of 1.74 mm2, and cup area of 0.32 mm2. These authors did not measure the RNFL thickness.6 They reported that the characteristics megalopapilla shared with glaucoma were: increased cup area, cup volume, and cup shape measurement. However, the following parameters were completely different from glaucoma: optic disc area, rim volume, and rim area.6In the present study, we evaluated 59 megalopapilla cases using HRTII and Stratus OCT. We found a large optic disc area (3.28±0.53 mm2) along with a proportionally wider rim area (1.63±0.37 mm2) and a cup area (1.65±0.50 mm2). These findings are similar to those reported by Sampaolesi and Sampaolesi.6 The small differences are likely due to the use of different software.Visual fields and pachymetric analysis did not show abnormal findings. The Blue Mountain study has shown that cup-disc ratio is strongly associated with disc diameter and optic disc with larger vertical diameters have considerably greater cup-disc ratios.8 Studies from several populations have suggested that groups with larger optic discs tend to have a higher prevalence of glaucoma.9 One such population is African Americans, who tend to have a larger optic disc size than whites along with a higher incidence of glaucoma. Observations such as these have prompted the hypothesis that individuals with larger optic discs may have an increased predisposition to glaucoma. Other studies, however, do not suggest such a relationship, thereby providing evidence against a link between optic disc size and glaucoma susceptibility.9The Stratus OCT has emerged as a sensitive and specific tool for RNFL thickness measurement to discriminate glaucomatous from normal eyes.10 The normal reference values for RNFL thickness analysis using the Stratus OCT analyzer have been established in a cohort of healthy subjects and have been incorporated into the Stratus OCT RNFL analysis software packet.11 Discrimination between glaucomatous and normal eyes using the global average and inferior average thickness parameters was possible with the Stratus OCT.9–11To the best of our knowledge, this paper is the first to study the RNFL thickness in megalopapilla. Schuman et al12 found that RNFL measurements by OCT present a high correlation with findings of the visual field examination. Neither pathologic cupping of the optic disc nor thinning of the neural rim area was as strongly associated with visual field loss as was RNFL thickness in that study.12 Paunescu et al13 found an average RNFL thickness of 96±9 μm in a group of normal eyes. Nasal and temporal quadrants showed the thinnest RNFL (70±15 μm). Superior and inferior RNFL quadrants were thicker (126±15 μm).13 These values are very close to those we found in megalopapilla. Therefore, megalodisc presents normal RNFL average thickness as well as the superior, nasal, inferior, and temporal quadrant as analyzed by Stratus OCT normative RNFL database. This is an important finding, because many patients with megalopapilla could have incorrect glaucoma diagnosis along with unnecessary treatment.One limitation of this study is the fact that the circular scan has a fixed diameter of 3.46 mm from the ONH margin. RNFL thickness, in fact, has been shown to decrease at increasing distances from the ONH.14 If a fixed circular diameter scan is used, the distance between the scan and the ONH margin will obviously be reduced in the presence of a large ONH. This may lead to an overestimation of RNFL thickness in patients with large ONHs, because the measurements would be made closer to the optic disc edge.14,15 The diameter of the circular scan should be customized according to the optic disc area.In conclusion, eyes with megalopapilla present an abnormally large optic disc along with a proportionally wider rim area and a large cup-disc area. The RNFL thickness is normal. These findings are essential for distinguishing megalopapilla from the optic glaucomatous neuropathy.REFERENCES1. Brodsky CM.Congenital optic disk anomalies.Surv Ophthalmol.1994;39:89–112. [CrossRef] [Medline Link] [Context Link]2. Franceschetti A, Bock R.Megalopapilla. A new congenital anomaly.Am J Ophthalmol.1950;33:227–235. [CrossRef] [Medline Link] [Context Link]3. Maisel JM, Pearlstein CS, Adams WH, et al..Large optic discs in the Marshallese population.Am J Ophthalmol.1989;107:145–150. [Context Link]4. Randhawa S, Shah VA, Kardon RH.Megalopapilla, not glaucoma.Arch Ophthalmol.2007;125:1134–1135. [CrossRef] [Full Text] [Medline Link] [Context Link]5. Sampaolesi R, Sampaolesi JR.Large optic nerveheads: megalopapillas or megalodiscs.Int Ophthalmol.2001;23:251–257. [CrossRef] [Full Text] [Medline Link] [Context Link]6. Sampaolesi R, Sampaolesi JR.The pseudoglaucomas.Int Ophthalmol.2001;23:267–269. [CrossRef] [Full Text] [Medline Link] [Context Link]7. Sampaolesi R, Sampaolesi JR.Congenital anomalies of the optic nerve head—review.Int Ophthalmol.2001;23:263–265. [CrossRef] [Full Text] [Medline Link] [Context Link]8. Rao HBL, Sekhar GC, Babu GJ, et al..Clinical measurement and categorization of optic disc in glaucoma patients.Indian J Ophthalmol.2009;57:361–364. [Context Link]9. Seider MI, Lee RY, Wang D, et al..Optic disk size variability between African, Asian, white, Hispanic, and Filipino Americans using Heidelberg retinal tomograph.J Glaucoma.2009;18:595–600. [Context Link]10. Gyatsho J, Kaushik S, Gupta A, et al..Retinal nerve fiber layer thickness in normal, ocular hypertensive, and glaucomatous Indian eyes.J Glaucoma.2008;17:122–127. [Context Link]11. Marsh BC, Cantor LB, WuDunn D, et al..Optic nerve head (ONH) topographic analysis by Stratus OCT in normal subjects: correlation to disc size, age, and ethnicity.J Glaucoma.2010;19:310–318. [Context Link]12. Schuman JS, Hee MR, Puliafito CA, et al..Quantification of nerve fiber layer thickness in normal and glaucomatous eyes using optical coherence tomography.Arch Ophthalmol.1995;113:586–596. [Context Link]13. Paunescu LA, Schuman JS, Price LL, et al..Reproducibility of nerve fiber thickness, macular thickness, and optic nerve head measurements using Stratus OCT.Invest Ophthalmol Vis Sci.2004;45:1716–1724. [Context Link]14. Savini G, Zanini M, Carelli V, et al..Correlation between retinal nerve fibre layer thickness and optic nerve head size: an optical coherence tomography study.Br J Ophthalmol.2005;89:489–492. [Context Link]15. Skaf M, Bernardes AB, Cardillo JA, et al..Retinal nerve fibre layer thickness profile in normal eyes using third-generation optical coherence tomography.Eye.2006;20:431–443. 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