To investigate visual acuity, corneal pachymetry, and anterior-surface irregularity indices correlation with keratoconus severity in a very large pool of clinically-diagnosed untreated keratoconic eyes, and in keratoconic eyes subjected to crosslinking intervention.

Total of 737 keratoconic (KCN) cases were evaluated. Group A was formed from 362 untreated keratoconic eyes, and group B from 375 keratoconic eyes subjected to partial normalization via topography-guided excimer laser ablation and high-fluence collagen crosslinking. A control group C of 145 healthy eyes was employed for comparison. We investigated distance visual acuity, uncorrected (UDVA), best-spectacle corrected (CDVA), and Scheimpflug-derived keratometry, pachymetry (central corneal thickness, CCT and thinnest, TCT), and two anterior-surface irregularity indices, the index of surface variance (ISV) and the index of height decentration (IHD). The correlations between these parameters vs topographic keratoconus classification (TKC) were investigated.

Keratometry for group A was K1 (flat) 46.67 ± 3.80 D and K2 (steep) 50.76 ± 5.02 D; for group B K1 44.03 ± 3.64 D and K2 46.87 ± 4.61 D; for group C, K1 42.89 ± 1.45 D and K2 44.18 ± 1.88 D. Visual acuity for group A was UDVA 0.12 ± 0.18 and CDVA 0.59 ± 0.25 (decimal), for group B, 0.51 ± 0.28 and 0.77 ± 0.22, and for group C, 0.81 ± 0.31 and 0.87 ± 0.12.

Correlation between ISV and TKC (r²) was for group A 0.853, and for group-B 0.886. Correlation between IHD and TKC was for group A r² = 0.731, and for group B 0.701. The ROC analysis ‘area under the curve’ was for CDVA 0.550, TCT 0.596, ISV 0.876 and IHD 0.887.

Our study indicates that the traditionally employed metrics of visual acuity and corneal thickness may not be robust indicators nor provide accurate assessment on either keratoconus severity or postoperative evaluation. Two anterior surface irregularity indices, derived by Scheimpflug-imaging, ISV and IHD, may be more sensitive and specific tools.

Visual acuity, Scheimpflug-derived pachymetry and anterior-surface irregularity correlation to keratoconus severity in untreated cases (A), treated with crosslinking (B), and in a control group (C) reveals that visual acuity and pachymetry do not correlate well with keratoconus severity.

Kanellopoulos AJ, Moustou V, Asimellis G. Evaluation of Visual Acuity, Pachymetry and Anterior-Surface Irregularity in Keratoconus and Crosslinking Intervention Follow-up in 737 Cases. J Kerat Ect Cor Dis 2013;2(3):95-103.

To evaluate the agreement of pachymetry data provided by a new instrument to measure intraocular pressure (IOP) and the corneal biomechanical response with the values provided by Pentacam in healthy and keratoconic eyes.

Fifty-four right eyes from 54 healthy patients (32 females, 22 males) and 82 eyes from 43 keratoconus patients (20 females, 23 males) were included in the study. All patients were evaluated with Pentacam and CorvisST (Oculus, Wetzlar, Germany) in random order in the same session. CorvisCCT was compared to Pentacam pachymetry in at the corneal center (PentacamCCT) and at the thinnest point (PentacamMinCT).

Average pachymetry provided by CorvisST was 534 ± 34 microns in the healthy population and 476 ± 56 microns in the population with keratoconus. Pachymetric values obtained with Pentacam were highly correlated between them as well as with the Corvis value in both groups, but the correlation coefficients were higher in the healthy group.

Corvis pachymetry can be used interchangeably with Pentacam thinnest point pachymetry in healthy corneas. However, in keratoconic corneas, the difference between both parameters will be higher as the disease progresses and increases the difference between Pentacam pachymetry at cornea center and at the thinnest point.

González-Méijome JM, Lopes-Ferreira D, Rico-del-Viejo L, Neves P, Ferreira H, Salgado-Borges J. Corneal Pachymetry measured with Pentacam and CorvisST in Normal and Keratoconic Eyes. Int J Kerat Ect Cor Dis 2013;2(3):104-107.

To evaluate the sensitivity and specificity of the Pentacam topometric indices derived from the corneal surface curvature to distinguish between normal and keratoconic corneas.

The study consisted of 226 normal corneas from 113 patients and 88 keratoconic eyes from 44 patients. Eyes were defined as keratoconus based on comprehensive ocular examination, including Placido-disk-based corneal topography (Atlas Corneal Topography System; Humphrey, San Leandro, California) and rotating Scheimpflug corneal tomography (Pentacam HR; Oculus, Wetzlar, Germany). Corneal Topometric indices ISV, IVA, KI, CKI, IHA and IHD, along with the TKC (Topometric Keratoconus Classification) score were calculated from the Pentacam HR exam. Statistical analysis were accomplished using BioEstat 5.0 (Instituto Mamiraua, Amazonas, Brazil) and MedCalc 12.0 (MedCalc Software, Mariakerke, Belgium) using unpaired nonparametric Mann Whitney test (Wilcoxon ranked-sum). ROC curves were calculated for each topometric parameter to determine the best cut off values from the significantly different parameters. A logistic regression analysis was performed to provide a combined parameter for optimizing accuracy.

Statistical significant differences were found between keratoconic and normal corneas for all topometric indices (Mann Whitney, p < 0.05). There were four false negative cases among the keratoconic cases on the TKC classification (4.54%) and 16 false positive cases among normal (7.08%), so that the sensitivity and specificity of the TKC were 95.54 and 92.92% respectively. The areas under the ROC curves (AUC) for the individual topometric indices varied from 0.843 (CKI) and 0.992 (ISV). The sensitivity and specificity of the most accurate ISV were 97.7 and 96.5% respectively. The calculated parameter from logistic regression had AUC of 0.996, with sensitivity of 97.7% and specificity of 98.7%.

Pentacam topometric indices were useful for distinguishing between normal and keratoconic corneas. The TKC classification should be expected to have false positives and negatives and should not be considered alone. TKC had more false positives and false negatives than some individual topometric parameters. A novel combined parameter based on logistic regression analysis may improve accuracy for the diagnosis of keratoconus. Further studies are necessary to evaluate if adding other curvature derived indices is beneficial for the regression analysis, as well as for testing the sensitivity of such parameters for the diagnosis of milder forms of ectasia and for testing correlations with severity of the disease.

Salomao MQ, Guerra FP, Ramos IC, Jordao LF, Canedo ALC, Valbon BF, Luz A, Correa R, Lopes B, Ambrósio Jr R. Accuracy of Topometric Indices for Distinguishing between Keratoconic and Normal Corneas. J Kerat Ect Cor Dis 2013;2(3):108-112.

Spadea L, Verboschi F, Valente S, Vingolo EM. Corneal Collagen Crosslinking for Keratectasia after Laser in situ Keratomileusis: A Review of the Literature. J Kerat Ect Cor Dis 2013;2(3):113-120.

Barbara A, Barbara R. Intacs Intracorneal Ring Segments Complications in Patients Suffering from Keratoconus. J Kerat Ect Cor Dis 2013;2(3):121-128.

To report a case of double descemet membrane forming a double anterior chamber following ‘Big bubble’ DALK converted to PKP.

A 52-year-old man with keratoconus underwent DALK operation converted to PKP due to macro perforation of the descemet membrane. On the postoperative evaluation a remnant of the host's descemet membrane formed a double anterior chamber. After a few months with no intervention, an attempt to deflect a thickened descemet membrane had failed, making entrance into the anterior chamber in order to excise the membrane inevitable. Two years following the second surgery a graft endothelial failure and cataract formation was documented, leading to a second corneal transplantation and lens implantation.

Double DM is an unusual condition following a DALK procedure which was converted into PKP. In the above case this complication resulted in multiple procedures and graft failure. We believe that early interventions such as gas injection or YAG laser could have resulted in a more favorable outcome.

Graffi S, Naftali M. Double Descemet Membrane Forming a Double Anterior Chamber. J Kerat Ect Cor Dis 2013;2(3):129-132.

Barbara A, Zadok D, Gutfreund S, Barbara R. Corneal Neovascularization and Lipid Keratopathy after Intacs SK in Keratoconus. J Kerat Ect Cor Dis 2013;2(3):133-138.

To demonstrate that UVA/riboflavin crosslinking (CXL) can cause corneal melting in some unpredictable cases.

We will present a case report of 25-year-old male patient referred for emergency keratoplasty which is due to corneal melting and perforation developed after uneventful CXL procedure for the treatment of keratoconus.

We performed uncomplicated penetrating keratoplasty of the left eye in our hospital.

CXL is gradually becoming the standard treatment procedure for progressive keratoconus and the only major safety concerns associated with CXL are ocular surface damage and endothelial cell damage. This case has shown, however, that even if CXL seems to have been successful, there is still a risk of adverse outcomes. Our report suggests that further research is necessary regarding the safety of corneal collagen crosslinking in corneas with keratoconus.

Demirci G, Ozdamar A. Case of Corneal Perforation as a Complication after Uneventful CXL without Infection. J Kerat Ect Cor Dis 2013;2(3):139-142.

Siqueira JA, Dias LC, Siqueira R, Valbon B, Santos R, Dawson D, Ambrósio Jr R. Longterm Improvement after the Athens Protocol for Advanced Keratoconus with Significant Ectasia Progression in the Fellow Eye. J Kerat Ect Cor Dis 2013;2(3):143-146.