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Retina: F. Nienke Boonstra, C. Erik van Nouhuys, José Schuil, Ilse J. de Wijs, Kim P. van der Donk, Kostas Nikopoulos, Arijit Mukhopadhyay, Hans Scheffer, Mauk A. D. Tilanus, Frans P. M. Cremers, and Lies H. Hoefsloot Clinical and Molecular Evaluation of Probands and Family Members with Familial Exudative Vitreoretinopathy Invest. Ophthalmol. Vis. Sci. 2009; 50: 4379-4385 [Abstract] [Full text] [PDF]

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Clinical Evaluation of Familial Exudative Vitreoretinopathy

David F Gilmour, Louise M. Downey   (3 November 2009)

Author Response: Clinical Evaluation of Familial Exudative Vitreoretinopathy

Nienke Boonstra   (3 November 2009)

Clinical Evaluation of Familial Exudative Vitreoretinopathy 3 November 2009
David F Gilmour, Clinical Research Fellow Section of Ophthalmology and Neuroscience, University of Leeds, UK, Louise M. Downey Send letter to journal: Re: Clinical Evaluation of Familial Exudative Vitreoretinopathy D.F.Gilmour{at}leeds.ac.uk David F Gilmour, et al.	Familial exudative vitreoretinopathy (FEVR) is a rare and complex disease and we welcome the new case series published recently by Boonstra et al.1 The authors state they have demonstrated significant differences in the posterior pole anatomy of eyes with FEVR when compared with a control group. They found smaller optic discs and larger disc-to-macula distances in FEVR patients with an avascular zone. In the study DM/DD ratio (disc-to-macula distance divided by disc diameter) is measured in the two groups, a method previously published to assess optic nerve hypoplasia.2 It is suggested that subtle anatomical changes identified by fundus photography of the posterior pole and using the DM/DD ratio may be an additional sign of FEVR. The authors measure DM/DD ratios and disc diameters (horizontal and vertical) in a series of FEVR eyes with a peripheral avascular retina and compare with a control group of 40 eyes with mild diabetic retinopathy. The authors found higher DM/DD ratios and lower optic disc measurements in the FEVR group and suggest that both these findings are statistically significant. However, we have a number of reservations about the validity of these findings. In the first instance we would question the use of a small group of patients with a different retinal vascular disease as a suitable control group in this study. Furthermore, with regards to optic disc size, the mean vertical disc diameter in the FEVR group was 1.60mm, compared to 1.74mm in the control group. In a series of over 6,500 non-glaucomatous eyes from the Blue Mountains eye study the median vertical disc diameter was 1.50mm, so both groups in this study therefore have above-average optic disc size.3 Was data on refractive error collected in both groups and included in the analysis? Differences in refractive error are associated with differences in optic disc size and in a study by Barr et al. it was shown that DM/DD ratio can vary according to refractive error.4,5 In addition there is a documented association with myopia and FEVR,6,7 which if present in this study could have given a falsely high DM/DD ratio in the FEVR group.5 In summary we do not feel that this study provides adequate validation of DM/DD ratio as a tool for assessing FEVR patients. In addition we would like to re-emphasise that in very mild cases a combination of genetic screening and peripheral fundus examination with or without fluorescein angiography remain the best aids for the diagnosis of FEVR. David F. Gilmour and Louise M. Downey Section of Ophthalmology and Neuroscience, University of Leeds, UK References 1. Boonstra FN, van Nouhuys CE, Schuil J, et al. Clinical and molecular evaluation of probands and family members with familial exudative vitreoretinapathy. Invest Ophthalmol Vis Sci. 2009;50:4379-4385. 2. Wakakura M, Alvarez E. A simple clinical method of assessing patients with optic nerve hypoplasia. The disc-macula distance to disc diameter ratio (DM/DD). Acta Ophthalmologica. 1987;65:612-617. 3. Crowston JG, Hopley CR, Healey PR, Lee A, Mitchell P. The effect of optic disc diameter on vertical cup to disc ratio percentiles in a population based cohort: the Blue Mountains Eye Study. Br J Ophthalmol. 2004;88:766-770. 4. Wang Y, Xu L, Zhang L, Yang H, Ma Y, Jonas JB. Optic disc size in a population based study in northern China: the Beijing Eye Study. Br J Ophthalmol. 2006;90:353-356. 5. Barr DB, Weir CR, Purdie AT. An appraisal of the disc-macula distance to disc diameter ratio in the assessment of optic disc size. Ophthalmic Physiol Opt. 1999;19:365-375. 6. Yang CI, Chen SN, Yang ML. Excessive myopia and anisometropia associated with familial exudative vitreoretinopathy. Chang Gung Med J. 2002;25:388-392. 7. Shukla D, Singh J, Sudheer G, et al. Familial exudative vitreoretinopathy (FEVR). Clinical profile and management. Indian J Ophthalmol. 2003;51:323-328.
Author Response: Clinical Evaluation of Familial Exudative Vitreoretinopathy 3 November 2009
Nienke Boonstra Send letter to journal: Re: Author Response: Clinical Evaluation of Familial Exudative Vitreoretinopathy n.boonstra{at}bartimeus.nl Nienke Boonstra	We thank Drs. Gilmour and Downey for their interesting comment regarding our article "Clinical and Molecular Evaluation of Probands and Family Members with Familial Exudative Vitreoretinopathy"1 and would like to offer the following response. Our article is a descriptive study; the differences found relate only to the specific groups described in the study. We describe several features in FEVR that may be useful in clinical practice after further evaluation. The higher DM/DD ratio (disc-to-macula distance divided by disc diameter) is one of these features.2 This finding can be useful for clinical evaluation, however we do not present this as a tool for assessing FEVR patients in our article. We agree with Drs. Gilmour and Downey's statement that a combination of genetic screening and peripheral fundus examination with or without fluorescein angiography remain the best aids for the diagnosis of FEVR. Although we do not claim general applicability of the DM:DD ratio this may be an interesting subject for further study. There is a high frequency of myopia in FEVR which would need to be taken into account to refine applicability of the DM/DD ratio. Myopia can be a confounder in posterior pole measurements in FEVR. In our study the number of patients with myopia was similar in both FEVR and control group. Barr3 presented ametropia classes and correlations with DM:DD ratio. In myopia there is a trend for increasing DM:DD ratio with increasing myopia, although there was no inter-class correlation between ametropia and the DM:DD ratio and differences were not significant. Yang et al.4 reported on the relation between excessive myopia and FEVR. They selected patients in Pendergast stages 1, 2 and 3. All patients had excessive myopia higher than -6 Diopters. They conclude that excessive myopia is more likely to occur in eyes of FEVR patients. Our patients and family members presented with an retinal avascular zone particularly in the periphery (Pendergast stage 1).The avascularity of the peripheral retina in FEVR is typical and can be distinguished from peripheral changes in myopia.5,6 In our study patients with excessive myopia often had additional problems such as cataract or falciform folds and therefore the DM:DD ratio could not be calculated in these patients. We decided to describe the differences found without making premature conclusions on the clinical implication of these findings. Further investigations with larger groups of FEVR patients and controls are required before these results can be implemented in the daily ophthalmological practice. Nienke F. Boonstra1 C. Erik van Nouhuys2 José Schuil1 Ilse J. de Wijs3 Kim P. van der Donk3 Kostas Nikopoulos3 Arijit Mukhopadhyay3 Hans Scheffer3 Mauk A. D. Tilanus4 Frans P. M. Cremers3 Lies H. Hoefsloot3 1Ophthalmology, Bartimeus - Zeist, Zeist, The Netherlands 2Canisius Wilhelmina Hospital - Ophthalmology, Nijmegen, The Netherlands 3Human Genetics, 4Ophthalmology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands References 1. Boonstra FN, van Nouhuys CE, Schuil J, et al. Clinical and molecular evaluation of probands and family members with familial exudative vitreoretinopathy. Invest Ophthalmol Vis Sci. 2009;50:4379-4385. 2. Wakura M, Alvarez E. Wakakura M, Alvarez E. A simple clinical method of assessing patients with optic-nerve hypoplasia the disk-macula distance to disk diameter ratio (DM/DD). Acta Ophthalmol. 1987;65:612-617. 3. Barr DB, Weir CR, Purdie AT. An appraisal of the disc –macula distance to disc diameter ratio in the assessment of optic disc size. Ophthalmic Physiol Opt. 1999;19:365-375. 4. Yang CI, Chen SN, Yang ML. Excessive myopia and anisometropia associated with familial exudative vitreoretinopathy. Chang Gung Med J. 2002;25:388-392. 5. Shukla D, Singh J, Sudheer G, et al. Familial exudative vitreoretinopathy (FEVR): Clinical profile and management. Indian J Ophthalmol. 2003;51:323-328. 6. Van Nouhuys CE. Dominant Exudative Vitreoretinopathy and other Vascular Developmental Disorders of the Peripheral Retina. Den Haag, The Netherlands: Dr. W. Junk Publishers; 1982.