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Clinical case A 16-year-old man presented at our institute with progressive reduction of vision acuity in both eyes. This patient presented to our corneal service with clinical and topographical features of bilateral superior keratoconus. The clinical features, topographical, Scheimpflug and photographs images findings of a asymmetric bilateral superior keratoconus are presented.

Summary Objective To assess safety and efficacy of corneal collagen crosslinking (CXL) for advanced bullous keratopathy (BK). Material and methods Eight eyes of eight patients subjected to Dresden CXL protocol. Inclusion criteria: BK history of at least one year, severe pain and no indication for keratoplasty due to poor visual prognosis. Variables: best corrected visual acuity (BCVA), pain (decimal visual scale), central corneal thickness (CCT) by tomography (Pentacam®, Oculus Inc, Germany), corneal bullae and complications. Results Seven women and one man of median age 77.00 (range 58–79) years. The median follow-up was 7 (range 5–7) months. BCVA remained unchanged through follow-up. A significant decrease in pain was observed at the end of the follow-up period (median 6, range 5–6 vs. median 0, range 0–4, P = 0.05). Corneal tomography could only be performed in three cases, due to poor vision or image quality. A reduction in mean CCT was observed in the first post procedural month (from 708.33 ± 140.48 to 627 ± 136.89 μm). In all eight cases, the absence of corneal bullae only persisted for two months after CXL. In six patients, corneal re-epithelialization after CXL was poor; in four of these eyes, the problem was resolved with topical treatment, but in the remaining two eyes, amniotic membrane transplant and mechanical debridement were required. Conclusions In this uncontrolled small case series, CXL treatment improved pain in patients with advanced BK. However, the high rate of poor re-epithelialization requiring surgical treatment observed in one third of cases makes this treatment controversial.

To compare the corneal densitometry changes after transepithelial pulsed (t-ACXL), epithelium-off continuous (c-ACXL) and epithelium-off pulsed (p-ACXL), accelerated corneal crosslinking for patients with progressive keratoconus.Prospective, interventional case series at a university hospital tertiary referral center. Forty eyes received t-ACXL, 40 eyes received c-ACXL, and 40 eyes received p-ACXL. Corneal tomography, densitometry and visual acuity were evaluated preoperatively and at 1, 3, 6, 12 and 24 months postoperatively.Total densitometry values of the total layer over the annular diameters 0-12 mm expressed in grayscale units (GSU) showed no significant change after t-ACXL and p-ACXL but increased significantly after c-ACXL at 1 month (16.76 ± 2.38, P value 0.01) and 3 months (16.12 ± 2.22, P value 0.04), returning to baseline levels at month 6 (14.97 ± 2.13, P value 0.99) and remained stable until final follow-up. At 1 month, the mean change in total densitometry value of the t-ACXL group (-0.53 ± 2.08) was significantly lower than the p-ACXL (0.70 ± 1.96 P value 0.04) and c-ACXL (1.97 ± 2.65 P value 0.01). There was no statistical difference in the mean change in total densitometry between the three groups from 6 to 24 months. In the c-ACXL group, a higher degree of CXL-induced corneal haze at 1 month was observed in patients with steeper preoperative keratometry readings and in individuals where a greater flattening effect was achieved at 24 months.Continuous epithelium-off accelerated cornea crosslinking appears to induce more corneal haze than pulsed epithelium-off and transepithelial pulsed cornea crosslinking in the early postoperative period. Differences resolve by six-months.

Purpose To investigate the capability of Zernike polynomials fitting to reconstruct corneal surfaces as measured by Pentacam HR tomographer, Medmont E300 Placido-disc and Eye Surface Profiler (ESP). Methods The study utilised a collection of clinical data of 527 participants. Pentacam HR raw elevation data of 660 eyes (430 healthy and 230 keratoconic) were fitted to Zernike polynomials of order 2 to 20. Same analyses were carried out on 158 eyes scanned by Medmont E300 Placido-disc and 236 eyes were scanned by ESP for comparison purposes. The Zernike polynomial ​fitting was carried out using a random 80% of each individual eye surface's data up to a corneal radius of 5 mm and the root means squared fitting error (RMS) was calculated for the unused 20% portion of the surface data. The process was carried out for the anterior and posterior surfaces of the corneal measurements of the Pentacam HR and the anterior surfaces only with the ESP and the Medmont E300 measurements. Results Statistical significances in reduction of RMS were noticed up to order 14 among healthy participants (p < 0.0001 for right eyes, p = 0.0051 for left eyes) and up to order 12 (p < 0.0001 for right eyes, p = 0.0002 for left eyes) in anterior surfaces measured by the Pentacam. Among keratoconic eyes, statical significance was noticed up to order 12 in both eyes (p < 0.0001 for right eyes, p = 0.0003 for left eyes). The Pentacam posterior corneal data, both right and left, healthy and keratotic eyes recorded significance (p < 0.0001) in reduction of RMS up to order 10 with same RMS values of 0.0003 mm with zero standard deviation. RMS of fitting Zernike polynomials to Medmont data up to order 20 showed a consistent reduction in RMS with the increase of the fitting order with no rise at high fitting orders. Minimum RMS = 0.0047 ± 0.0021 mm, 0.0046 ± 0.0019 mm for right and left eyes respectively were recorded at order 20 and were more than 15 times the minimum RMS of the Pentacam. RMS of fitting Zernike polynomials to ESP data also showed a consistent reduction in RMS with the increase of the fitting order with no sign of any rise at high fitting orders. Similar to the Medmont, minimum RMS of 0.0005 ± 0.0003 mm, 0.0006 ± 0.0003 mm was recorded at order 20 for right and left eyes respectively and was 2 times the minimum RMS of the Pentacam for right eyes and 1.7 times the minimum RMS of the Pentacam for left eyes. Conclusions Orders 12 and 10 Zernike polynomials almost perfectly matched the raw-elevation data collected from Pentacam for anterior and posterior surfaces, respectively for either healthy or keratoconic corneas. The Zernike fitting could not perfectly match the data collected from Medmont E300 and ESP., Corneal tomography, Pentacam, Zernike polynomials, Signal processing, Curve fitting.

Resume L’objectif L’effet des cycloplegiques sur les mesures keratorefractometriques et tomographiques corneennes est peu connu. L’objectif de notre etude etait de tester et de comparer les effets des cycloplegiques (cyclopentolate et atropine) sur la forme corneenne et la puissance refractive de l’œil. Methodes Quarante-neuf participants ont ete inclus (84 yeux) dans cette etude prospective. Les patients ont ete randomises en deux groupes, atropine 1 % (32 yeux) et cyclopentolate 1 % (52 yeux). L’orbscan IIz a ete utilise pour evaluer la tomographie corneenne. Pour evaluer la forme corneenne, les valeurs de SimK, BFS, anterieure et posterieure, W-W, la puissance corneenne tangentielle et axiale ont ete mesurees pour les faces corneennes anterieures et posterieures, avant et pendant la cycloplegie. Le diametre de la pupille, la profondeur de la chambre anterieure, l’epaisseur de la cornee dans les zones circulaires de 3,5 et 7 mm, et dans la partie la plus mince de la cornee et aussi l’epaisseur corneenne au centre de fixation ont ete egalement examines. Le logiciel de statistique SPSS a ete utilise pour l’analyse statistique des donnees. Resultats La BFS anterieure et posterieure, la puissance corneenne tangentielle et axiale, le SimK, n’ont pas change lors de la cycloplegie dans les deux groupes traites par atropine et cyclopentolate. L’ACD etait plus profonde lors de l’utilisation de l’atropine que lors de l’utilisation du cyclopentolate. L’epaisseur corneenne est restee inchangee pendant la cycloplegie dans les deux groupes. Le diametre des pupilles etait plus large chez les iris clairs traites avec le cyclopentolate que dans le groupe traite avec l’atropine. Dans les deux groupes, les mesures du diametre corneen – blanc a blanc n’ont pas montre une difference statistique avant ( p = 0,473) et pendant la cycloplegie ( p = 0,287). Conclusion Les examens effectues sur notre echantillon montrent que l’utilisation de l’atropine 1 % et du cyclopentolate 1 % ne change pas la forme corneenne (mesuree par la tomographie corneenne).

To assess the repeatability and comparability of corneal power and central corneal thickness (CCT) measurements obtained using Orbscan II (BauschLomb), Pentacam (Oculus), and Galilei (Ziemer) tomographers.Prospective, comparative study.setting: Departments of Ophthalmology, University of Auckland and Auckland District Health Board, Auckland, New Zealand. study population: Thirty eyes of 30 healthy participants. observations. CCT and corneal power measured using Orbscan II, Pentacam, and Galilei tomography. main outcome measures: Degree of agreement in and repeatability of CCT and corneal power measures.Orbscan II measured significantly lower CCT compared with Pentacam (20 μm; P.0005) and Galilei (18 μm; P.0005). The Orbscan II had wide limits of agreement when compared with both the Galilei (-11 to 47 μm) and Pentacam (-88 to 47 μm). For each device, the intraclass correlation coefficient for CCT was higher than 0.9. The coefficient of variation ranged from 0.33% to 0.93%. There was no significant difference in mean steep keratometry or mean flat keratometry between instrument pairs. However, there was poor agreement in flat keratometry and steep keratometry obtained by Orbscan II compared with those obtained by the Galilei and Pentacam.The keratometry and pachymetry measurements obtained by Orbscan II, Pentcam, and Galilei tomographers were sufficiently disparate that the 3 devices could not be considered equivalent. All 3 devices demonstrated a high level of repeatability, although the Galilei exhibited the best repeatability.

To evaluate a novel Zernike algorithm to differentiate 3-dimensional (3-D) corneal thickness distribution of corneas with keratoconus (KC) from normal corneas.A retrospective development and evaluation of a diagnostic approach.Corneal tomography with Scheimpflug imaging was performed in normal (43 eyes) and KC (85 eyes) corneas. Axial and tangential cone location magnitude index (axial CLMI and tangential CLMI, respectively) of the anterior and posterior surface were calculated. The aberrations of the anterior corneal surface were analyzed with Zernike polynomials. Pachymetric Zernike analyses (PZA) were used to map the 3-D thickness distribution of the cornea. Logistic regression was performed to develop a diagnostic procedure for KC using CLMI, PZA, and aberrations. A receiver operating characteristic curve was constructed for each regression model. Corneal volume was also compared between normal and KC corneas. Only the central 5 mm zone was used for all analyses.Among the PZA coefficients, second- and third-order root mean squares of PZA coefficients were the best predictors of KC corneas (P.0001). Among the CLMI variables, axial CLMI of anterior and tangential CLMI of posterior surface were the best predictors of KC (P.0001). Among the Zernike corneal aberration coefficients, second- and third-order root mean squares of coefficients were the best predictors of KC (P.0001). Sensitivity and specificity of Zernike corneal aberrations, CLMI, and PZA logistic regression model were similar (P.05).The entire 3-D corneal thickness was mapped with Zernike. The PZA method was comparable to CLMI and anterior corneal wavefront aberrations in detecting KC.