Ophthalmology Volume 120, Number 2, February 2013

We concluded that TSI may be regarded as functional biomarker for TAO. We regret that the paper by Dragan et al was not consideredin our manuscript. In line with these authors, we believe that serial serum TSI measurements are a useful tool in assessing clinicalinflammatory activity of TAO and help management decision making in TAO. To further gain insight in the clinical relevance of TSI inthis complex autoimmune disease, a prospective trial in a large series of TAO patients has been undertaken at our institution and the resultswill be published in due course.

KATHARINA A. PONTO, MD,1 GEORGE J. KAHALY, MD2

1Department of Ophthalmology and 2Department of Medicine I, University Medical Center Mainz, Germany

References

1. Dragan LR, Seiff SR, Lee DC. Longitudinal correlation of thyroid-stimulating immunoglobulin with clinical activity of disease inthyroid-associated orbitopathy. Ophthal Plast Reconstr Surg 2006;22:13–9.

2. Lytton SD, Ponto KA, Kanitz M, et al. A novel thyroid stimulating immunoglobulin bioassay is a functional indicator of activity andseverity of Graves’ orbitopathy. J Clin Endocrinol Metab 2010;95:2123–31.

3. Ponto KA, Kanitz M, Olivo PD, et al. Clinical relevance of thyroid-stimulating immunoglobulins in Graves’ ophthalmopathy.Ophthalmology 2011;118:2279–85.

4. Lytton SD, Li Y, Olivo PD, et al. Novel chimeric thyroid-stimulating hormone-receptor bioassay for thyroid-stimulating immuno-globulins. Clin Exp Immunol 2010;162:438–46.

5. Lytton SD, Kahaly GJ. Bioassays for TSH-receptor autoantibodies: an update. Autoimmun Rev 2010;10:116–22.

Financial Disclosure:G. J. Kahaly consults for and has received grants by DIAGNOSTIC HYBRIDS, Inc. Athens, Ohio.

Multiple Sclerosis Eye-Brain Dynamic Correlation

Dear Editor:Our report on retinal nerve fiber layer and brain grey substance as early prognostic factors for disability in multiple sclerosis (MS) in theBritish Journal of Ophthalmology1 was published simultaneously with the report of Walters et al2 on the impact of retinal ganglion cell(RGC) loss and visual disability in MS patients. Walters et al2 enrolled 122 MS patients (239 eyes) and 31 controls (61 eyes) in their study.Among the MS patients, 87 had a history of acute optic neuritis. The study protocol was based on visual acuity testing, optical coherencetomography (OCT), and validated questionnaires on visual function and quality of life. They reported that retinal nerve fiber layer thicknessat the macular level and the thickness of the RGC plus the inner plexiform layer were lower in the MS group, and correlated with visualacuity and visual acuity-related quality of life. The authors suggest that these OCT parameters may be considered structural biomarkers ofneurologic disability in MS patients.

We share a common goal with Walters et al2 in trying to identify associations between visual and neurological function and OCT retinal imagesthat reflect the functional impact of microstructural alterations in vivo. We agree that these fundamental approaches may help ophthalmologistsand neurologists to manage MS patients better. However, we have some methodologic concerns about the recently published study.2 First, theclinical subtypes of MS are not well described, despite the existence of significant differences between MS clinical subtypes in terms of theneuronal and axonal components of the macula.3 In addition, Walters et al2 used a segmentation algorithm from the macular cube scanningprotocol to conclude that RGC layer plus inner plexiform layer neuronal loss strongly correlated with visual function and quality of life. Thiscorrelation was based on the retinal RGC layer plus inner plexiform layer neuronal loss observed in MS eyes with and without a history of acuteoptic neuritis. Surprisingly, Walters et al2 did not find the thinning of the outermost retinal layers that indicates that patients with inner and outerlayer pathology have more rapid disability progression and perhaps a more aggressive form of MS.4 The absence of thinning of the outermostretinal layers may be owing to inclusion of different clinical MS subtypes to those studied by Saida et al,4 resulting in different basicdemographics, corticosteroid treatment and therapy history, and a lack of electrophysiologic testing.

Walter et al suggested that, as a parallel finding to brain grey matter atrophy observed in magnetic resonance imaging studies, retinalneuronal degeneration is closely associated with visual disability in MS and highlighted the relevance of prospective studies for analyzingthe relationship between axonal damage and RGC loss in a spatial and temporal fashion. We agree that prospective dynamic studies willnot only help us to a better understanding of retinal damage, but will also increase the reliability of findings obtained from other types ofneuroimaging. In our study, we compared retinal structural changes identified by OCT with brain structural changes identified by magneticresonance imaging in MS patients with isolated clinical syndromes, and relapsing-recurrent and progressive forms. We found a significantcorrelation between the relative change in brain grey substance volume and retinal nerve fiber layer from baseline to 1 year follow-up(Pearson r � 0.458; P � 0.019).1

These results agree with the findings of Walters et al and Saida et al, and suggest that the macular is the retinal area that is damagedfirst in MS patients, and that this damage is manifested by decreased macular thickness before changes at the optic nerve level are seen,emphasizing the relevance of the association with brain grey substance changes.5 Further research is needed to detect both preclinical andclinical signs and symptoms to improve MS patient outcomes.

ANA LLORCA-CARDEÑOSA, MD, MARÍA JOSÉ MAGRANER-BENEDICTO, MD, MARTA J. LLORCA-CARDEÑOSA, BS (BIOLOGY),RAQUEL BAÑÓN-NAVARRO, MD, PHD, ANTONIO LLEÓ-PÉREZ, MD, PHD, MARÍA DOLORES PINAZO-DURÁN, MD, PHD

Department of Ophthalmology, Castellon General Hospital, Castellón de la Plana, Spain

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Correspondence

The authors of the original article declined to reply.

References

1. Llorca-Cardeñosa A, Magraner-Benedicto MJ, Llorca-Cardeñosa MJ, et al. Retinal nerve fiber layer and brain grey substance as earlyprognostic factors for disability in multiple sclerosis. Br J Ophthalmol 2012;96:1357.

2. Walters SD, Ishikawa H, Galetta KM, et al. Ganglion cell loss in relation to visual disability in multiple sclerosis. Ophthalmology2012;119:1250–7.

3. Pulicken M, Gordon-Lipkin E, Balcer LJ, et al. Optical coherence tomography and disease subtype in multiple sclerosis. Neurology2007;69:2085–92.

4. Saida S, Syc SB, Ibrahim MA, et al. Primary retinal pathology in multiple sclerosis as detected by optical coherence tomography Brain2011;134:518–33.

5. Charbel Issa P, Troeger E, Finger R, et al. Structure-function correlation of the human central retina. PLoS ONE 2010;5:e12864.

Risk Factors for Pterygium

I was somewhat disappointed to read the recent paper by Ang et al on risk factors for pterygium in Singapore.1 Although they report asubstantial body of work with a large number of subjects and a lot of detailed data collection and analysis, their assessment of exposureto solar radiation is inadequate for their analysis. For sun-related conditions such as pterygium, the proper assessment of individual ocularexposure to ultraviolet light or sunlight is essential to be able to investigate the influence of sun exposure and the contribution of other riskfactors. The simplistic use of indoor or outdoor occupation has been shown to be inadequate to categorize people’s ocular exposure.2,3

Unfortunately, the importance of the need for comparable precision in the assessment of sun exposure, as has been used for other outcomesin their study, has been overlooked.

HUGH R. TAYLOR, MD, FRANZCOUniversity of Melbourne, Carlton, Victoria, Australia

The authors of the original article declined to reply.

References

1. Ang M, Li X, Wong W, et al. Prevalence of and racial differences in pterygium. Ophthalmology 2012;119:1509–15.2. Rosenthal FS, Phoon C, Bakalian AE, Taylor HR. The ocular dose of ultraviolet radiation to outdoor workers. Invest Ophthalmol Vis

Sci 1988;29:649–56.3. Taylor HR, West SK, Rosenthal FS, et al. Corneal changes associated with chronic ultraviolet irradiation. Arch Ophthalmol

1989;107:1481–4.

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