REFERENCES
ROHIT RAMESH MODI
1. Alessio G, L’Abbate M, Furino C, Sborgia C, La Tegola MG. Confocal microscopy analysis of the corneal changes after photorefractive keratectomy plus crosslinking for keratoconus: 4-year follow-up. Am J Ophthalmol 2014;158(3):476–484. 2. Jordan C, Patel DV, Abeysekera N, McGhee CN. In vivo confocal miocroscopy analyses of corneal microstructural changes in a prospective study of collagen cross-linking in keratoconus. Ophthalmology 2014;121(2): 469–474. 3. Knappe S, Stachs O, Zhivov A, Hovakimyan M, Guthoff R. Results of confocal microscopy examinations after collagen cross-linking with riboflavin and UVA light in patients with progressive keratoconus. Ophthalmologica 2011;225(2): 95–104.
Half-fluence Versus Half-dose Photodynamic Therapy in Chronic Central Serous Chorioretinopathy EDITOR:
SHALINI BUTOLA UMESH CHANDRA BEHERA
Bhubaneswar, Odisha, India THE AUTHORS HAVE COMPLETED AND SUBMITTED THE ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported. The authors indicate no funding support.
REFERENCES
1. Nicolo M, Eandi CM, Alovisi C, et al. Half-fluence versus halfdose photodynamic therapy in chronic central serous chorioretinopathy. Am J Ophthalmol 2014;157(5):1033–1037. 2. Kitchen CMR. Nonparametric vs parametric tests of location in biomedical research. Am J Ophthalmol 2009;147(4): 571–572. 3. Wang M, Munch IC, Hasler PW, Pru¨nte C, Larsen M. Central serous chorioretinopathy. Acta Ophthalmol 2008;86(2): 126–145. 4. Ozmert E, Batioglu F. Fundus autofluorescence before and after photodynamic therapy for chronic central serous chorioretinopathy. Ophthalmologica 2009;223(4):263–268.
WE READ WITH GREAT INTEREST THE ARTICLE BY NICOLO
and associates,1 which addresses an important issue in the treatment of chronic central serous chorioretinopathy (CSC). They have used the mean as a measure of central tendency for logarithm of the minimal angle of resolution (logMAR) best-corrected visual acuity (BCVA). But the sample size is small and standard deviation is large. In our opinion, median and interquartile range are better for measurement of central tendency and spread, as they are robust against outliers. Paired and unpaired t test were used by the authors. When the sample size is small (31eyes received half-fluence photodynamic therapy [PDT] and 29 eyes received half-dose PDT), nonparametric tests are much more powerful than their parametric counterparts.2 Wilcoxon rank-sum test and MannWhitney U test would have been more appropriate statistical tests. The extraocular risk factors that are associated with CSC, such as type A personality, systemic glucocorticoid administration, untreated hypertension, pregnancy, and alcohol intake, were neither evaluated nor matched in the study groups.3 To prove the study hypothesis showing superiority of a particular procedure over the other, these confounding factors should have been considered to measure the efficacy, especially when the disease recurred in 9 eyes in the half-fluence group and 5 eyes in the halfdose group. The authors state that no atrophic changes of the retinal pigment epithelium (RPE) in the area of PDT application were seen upon analysis of fundus photographs and fluorescein angiograms. Fundus autofluorescence would have been a better tool for evaluation of RPE function.4 VOL. 159, NO. 1
REPLY WE APPRECIATE THE COMMENTS OF MODI AND ASSOCIATES
with respect to our recent paper.1 Statistical analysis was influenced by the reviewers’ suggestions. We were asked to convert decimal best-corrected visual acuity (BCVA) in logMAR values, just because we treated these values as parametric parameters and because standard deviation is not symmetrical and hence appropriate for decimal BCVA. This was a retrospective study. For this reason extraocular risk factors, as well as fundus autofluorescence images, were not available on our clinical records for all the patients. We thank Modi and associates for their prompt comments. ´ MASSIMO NICOLO CARLO ENRICO TRAVERSO DONATELLA MUSETTI FELICE CARDILLO PICCOLINO
Genova, Italy CHIARA M. EANDI
Genova and Torino, Italy CAMILLA ALOVISI FEDERICO M. GRIGNOLO
Torino, Italy CONFLICT OF INTEREST DISCLOSURES: SEE THE ORIGINAL article for any disclosures of the authors.
CORRESPONDENCE
205
ROHIT RAMESH MODI
1. Alessio G, L’Abbate M, Furino C, Sborgia C, La Tegola MG. Confocal microscopy analysis of the corneal changes after photorefractive keratectomy plus crosslinking for keratoconus: 4-year follow-up. Am J Ophthalmol 2014;158(3):476–484. 2. Jordan C, Patel DV, Abeysekera N, McGhee CN. In vivo confocal miocroscopy analyses of corneal microstructural changes in a prospective study of collagen cross-linking in keratoconus. Ophthalmology 2014;121(2): 469–474. 3. Knappe S, Stachs O, Zhivov A, Hovakimyan M, Guthoff R. Results of confocal microscopy examinations after collagen cross-linking with riboflavin and UVA light in patients with progressive keratoconus. Ophthalmologica 2011;225(2): 95–104.
Half-fluence Versus Half-dose Photodynamic Therapy in Chronic Central Serous Chorioretinopathy EDITOR:
SHALINI BUTOLA UMESH CHANDRA BEHERA
Bhubaneswar, Odisha, India THE AUTHORS HAVE COMPLETED AND SUBMITTED THE ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported. The authors indicate no funding support.
REFERENCES
1. Nicolo M, Eandi CM, Alovisi C, et al. Half-fluence versus halfdose photodynamic therapy in chronic central serous chorioretinopathy. Am J Ophthalmol 2014;157(5):1033–1037. 2. Kitchen CMR. Nonparametric vs parametric tests of location in biomedical research. Am J Ophthalmol 2009;147(4): 571–572. 3. Wang M, Munch IC, Hasler PW, Pru¨nte C, Larsen M. Central serous chorioretinopathy. Acta Ophthalmol 2008;86(2): 126–145. 4. Ozmert E, Batioglu F. Fundus autofluorescence before and after photodynamic therapy for chronic central serous chorioretinopathy. Ophthalmologica 2009;223(4):263–268.
WE READ WITH GREAT INTEREST THE ARTICLE BY NICOLO
and associates,1 which addresses an important issue in the treatment of chronic central serous chorioretinopathy (CSC). They have used the mean as a measure of central tendency for logarithm of the minimal angle of resolution (logMAR) best-corrected visual acuity (BCVA). But the sample size is small and standard deviation is large. In our opinion, median and interquartile range are better for measurement of central tendency and spread, as they are robust against outliers. Paired and unpaired t test were used by the authors. When the sample size is small (31eyes received half-fluence photodynamic therapy [PDT] and 29 eyes received half-dose PDT), nonparametric tests are much more powerful than their parametric counterparts.2 Wilcoxon rank-sum test and MannWhitney U test would have been more appropriate statistical tests. The extraocular risk factors that are associated with CSC, such as type A personality, systemic glucocorticoid administration, untreated hypertension, pregnancy, and alcohol intake, were neither evaluated nor matched in the study groups.3 To prove the study hypothesis showing superiority of a particular procedure over the other, these confounding factors should have been considered to measure the efficacy, especially when the disease recurred in 9 eyes in the half-fluence group and 5 eyes in the halfdose group. The authors state that no atrophic changes of the retinal pigment epithelium (RPE) in the area of PDT application were seen upon analysis of fundus photographs and fluorescein angiograms. Fundus autofluorescence would have been a better tool for evaluation of RPE function.4 VOL. 159, NO. 1
REPLY WE APPRECIATE THE COMMENTS OF MODI AND ASSOCIATES
with respect to our recent paper.1 Statistical analysis was influenced by the reviewers’ suggestions. We were asked to convert decimal best-corrected visual acuity (BCVA) in logMAR values, just because we treated these values as parametric parameters and because standard deviation is not symmetrical and hence appropriate for decimal BCVA. This was a retrospective study. For this reason extraocular risk factors, as well as fundus autofluorescence images, were not available on our clinical records for all the patients. We thank Modi and associates for their prompt comments. ´ MASSIMO NICOLO CARLO ENRICO TRAVERSO DONATELLA MUSETTI FELICE CARDILLO PICCOLINO
Genova, Italy CHIARA M. EANDI
Genova and Torino, Italy CAMILLA ALOVISI FEDERICO M. GRIGNOLO
Torino, Italy CONFLICT OF INTEREST DISCLOSURES: SEE THE ORIGINAL article for any disclosures of the authors.
CORRESPONDENCE
205
