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• Reply to: "Diagnostic criteria of forme fruste keratoconus"
  Antonio Pizzuti
  Published on: 27 April 2016
• Diagnostic criteria of forme fruste keratoconus.
  Petra Liskova
  Published on: 27 April 2016

• Published on: 27 April 2016

  Reply to: "Diagnostic criteria of forme fruste keratoconus"

  • Antonio Pizzuti, Doctor
  • Other Contributors:
    • Francesco Brancati, Enza Maria Valente, Anna Sarkozy, Jànos Fehèr, Marco Castori, Pietro Del Duca, Rita Mingarelli, Antonio Pizzuti and Bruno Dallapiccola

  Dear Editor              

  We thank the authors for their comments on our Letter to the Editor describing a novel locus for autosomal dominant keratoconus on chromosome 3 [1]. We thoroughly agree with the author’s opinion that simple astigmatism should not be considered a diagnostic criteria for forme fruste KC. However, none of our 4 patients diagnosed with forme fruste KC had simple astigmatism. In these patients, t...

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  Dear Editor              

  We thank the authors for their comments on our Letter to the Editor describing a novel locus for autosomal dominant keratoconus on chromosome 3 [1]. We thoroughly agree with the author’s opinion that simple astigmatism should not be considered a diagnostic criteria for forme fruste KC. However, none of our 4 patients diagnosed with forme fruste KC had simple astigmatism. In these patients, the clinical diagnosis of KC was based on a 1,5 Dioptre (D) increment scale videokeratographic analysis. In particular, in patient III:9 (whose videokeratographic picture is shown in the middle panel of figure 2) astigmatism was irregular on the right eye and regular on the left. A superior-inferior difference was recorded in both eyes, while in the right the corneal apex was dislocated in the inferior temporal quadrant of the cornea. Thus, this patient fulfil the diagnostic criteria for forme fruste KC [2]. Figure 2 showed these findings, although some details could have been lost in the printed version. We confirmed these data in patient III:9 with a more sensitive quantitative evaluation of the same videokeratography using a colorcoded map with 0,45 D increments. This analysis showed that the highest keratometric values in dioptre were 42,70 D on the superior and 43,60 D on the inferior cornea of the right eye and 43,60 D in the superior and 45,0 D on the inferior cornea of the left eye. Taken together these data point out the role of videokeratography in the diagnosis of subtle corneal abnormalities such as forme fruste KC, in agreement with Levy and coworkers who recommend to achieve a detection rate of at least 0.5 D increment scale for forme fruste KC [3].                              

  Finally, the Hudson-Stahli’s line, described in two KC patients in table 2 was not considered as a sign of the disease but an occasional finding on slit-lamp examination.

  References

  (1) Liskova P. Diagnostic criteria of forme fruste keratoconus [electronic response to Brancati F et al. A locus for autosomal dominant keratoconus maps to human chromosome 3p14–q13] 

  (2). Brancati F, Valente EM, Sarkozy A, Feher J, Castori M, Del Duca P, Mingarelli R, Pizzuti A, Dallapiccola B. A locus for autosomal dominant keratoconus maps to human chromosome 3p14-q13. J Med Genet 2004;41:188- 192.

  (3). Rabinowitz YS. Videokeratographic indices to aid in screening for keratoconus. J Refract Surg 1995;11:371-379. 4. Levy D, Hutchings H, Rouland JF, Guell J, Burillon C, Arne JL, Colin J, Laroche L, Montard M, Delbosc B, Aptel I, Ginisty H, Grandjean H, Malecaze F. Videokeratographic anomalies in familial keratoconus. Ophthalmology 2004;111:867-874.

  The authors: Francesco Brancati1,2, Enza Maria Valente1, Anna Sarkozy1,2, Jànos Fehèr3, Marco Castori1,2, Pietro Del Duca4, Rita Mingarelli1, Antonio Pizzuti1,2 and Bruno Dallapiccola1,2

  1 CSS Hospital, IRCCS, San Giovanni Rotondo and CSS-Mendel Institute, Rome;

  2 Department of Experimental Medicine and Pathology, University “La Sapienza”, Rome; 

  3 Department of Ophthalmology, University "La Sapienza", Rome;

  4 U.O. Internal Medicine, POC, Montefiascone, Viterbo.

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  Conflict of Interest:
  None declared.

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• Published on: 27 April 2016

  Diagnostic criteria of forme fruste keratoconus.

  • Petra Liskova, Ophthalmologist
  • Other Contributors:
    • Neil D. Ebenezer, Stephen J. Tuft and Shomi S. Bhattacharya

  Dear Editor

  We would like to comment on the letter describing linkage analysis in autosomal dominant keratoconus presented by Brancati et al. in the March issue of JMG [1]. The pedigree includes 4 patients with forme fruste keratoconus and Figure 2 shows the videokeratography of patient III:9 to support this diagnosis. However, from the data presented this patient appears to have unilateral simple astigmatism, whi...

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  Dear Editor

  We would like to comment on the letter describing linkage analysis in autosomal dominant keratoconus presented by Brancati et al. in the March issue of JMG [1]. The pedigree includes 4 patients with forme fruste keratoconus and Figure 2 shows the videokeratography of patient III:9 to support this diagnosis. However, from the data presented this patient appears to have unilateral simple astigmatism, which does not fulfil the diagnostic criteria defined in the reference provided [2]. Futhermore, there is little evidence of inferior corneal steepening and the keratometry values are not unusually high [2,3] Corneal thickness measurements, which may be reduced in keratoconus, were not presented.

  The authors point out that large pedigrees with clinically evident keratoconus are rare and videokeratography has been used to identify asymptomatic family members who have early changes of keratoconus. These patients with forme fruste keratoconus allow pedigrees to be expanded [4,5]. Levy et al. (2004) identified specific parameters that may characterise forme fruste keratoconus [6]. However it has yet to be shown that these abnormalities inevitably progress to clinical keratoconus .We consider that the diagnostic criteria for forme fruste keratoconus should not be expanded to include patients with simple astigmatism until a link between the two conditions can be established. The exclusion of patient III:9 from the study would inevitably result in a reduction in the significance of the calculated LOD score.

  In addition, we would also like to point out that the clinical sign of a Hudson Stahli line used to describe the clinical features of the disease in affected patients (Table 2) is usually accepted to be a sign of a normal cornea. A circular Fleischer ring is the clinical sign that accompanies the central corneal steepening of keratoconus

  Although this letter raises the interesting possibility of a new locus for familial keratoconus the points that we have highlighted should be addressed to clarify the diagnosis of the early stages of the disease.

  References

  (1) Brancati F, Valente EM, Sarkozy A, et al. A locus for autosomal dominant keratoconus maps to human chromosome 3p14-q13. J Med Genet 2004;41(3):188-92.

  (2) Rabinowitz YS. Videokeratographic indices to aid in screening for keratoconus. J Refract Surg 1995;11(5):371-9.

  (3) Rabinowitz YS. The genetics of keratoconus. Ophthalmol Clin North Am 2003;16(4):607-20, vii.

  (4) Rabinowitz YS. Keratoconus. Surv Ophthalmol 1998;42(4):297-319.

  (5) Morrow GL, Stein RM, Racine JS, et al. Computerized videokeratography of keratoconus kindreds. Can J Ophthalmol 1997;32(4):233 -43.

  (6) Levy D, Hutchings H, Rouland JF, et al. Videokeratographic anomalies in familial keratoconus. Ophthalmology 2004;111(5):867-74.

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  Conflict of Interest:
  None declared.

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