Corneal Warpage Research Articles

Impact of removing soft contact lenses 1day versus 1month before surgery on the outcomes of microkeratome laser in situ keratomileusis.

To compare the outcomes, safety, efficacy, and predictability of microkeratome laser in situ keratomileusis (LASIK) 24h and one month or more after removing soft contact lenses. ULTRALASIK Eye Center, Dubai, United Arab Emirates. The patients were divided based on the time of discontinuation of the soft contact lenses before LASIK (Group 1 at 24h and Group 2 at one month or longer), and the two groups were well matched. Schirmer's testing, tear break-up time, corrected distance visual acuity, uncorrected distance visual acuity, manifest refraction spherical equivalent, and infection rate were evaluated preoperatively and at one week, one month, and six months after treatment. Group 1 (G1) comprised 1025 eyes, and group 2 (G2) had 1052 eyes. The groups were comparable preoperatively. The overall-mentioned outcomes were comparable between groups with uncorrected distance visual acuity of - 0.084 ± 0.12 logMAR in G1 and - 0.078 ± 0.17 logMAR in the G2 at 6months (P = 0.322). Tear break-up time as well as Schirmer's testing results was also comparable with no evidence of increased risk of dry eyes or non-inflammatory complications in any of the groups on follow-up visits at 1week (P = 0.421), 1month (P = 0.101), and 6months (P = 0.399) postoperatively. Finally, no infectious complications were recorded in either of the groups. With the absence of corneal warpage, no statistical or clinical difference in microkeratome LASIK outcomes and safety was spotted between the groups despite the difference in SCL discontinuation time before the procedure.

Corneal warpage caused by cosmetic contact lenses: a case description.

Corneal warpage caused by cosmetic contact lenses: a case description.

Tonometry by Ocular Response Analyzer in Keratoconic and Warpage Eyes in Comparison with Normal Eyes.

Purpose:To compare intraocular pressure (IOP) values measured by ocular response analyzer (ORA) in contact lens-induced corneal warpage, normal, and keratoconic eyes.Methods:In a prospective, observational case–control study, 94 eyes of 47 warpage-suspected cases and 46 eyes of 23 keratoconic patients were enrolled. Warpage-suspected cases were followed until a definite diagnosis was made (warpage, nonwarpage normal, or keratoconus). ORA tonometry and corneal biomechanics testing were performed for all cases in each visit. We had 2–3 measured corneal-compensated IOP (IOPcc) and Goldmann-correlated IOP (IOPg) for each patient (based on group) with at least 2-week interval.Results:After following up of warpage-suspected patients, finally 44 eyes of 22 patients had confirmed soft contact lens-related corneal warpage. Forty-six eyes of 23 people were finally diagnosed as nonwarpage normal eyes. Forty-six eyes of 23 known keratoconus patients were also included for comparison. The demographic and refractive data were not different between the warpage and nonwarpage normal groups but were different in the keratoconus group. Both IOPcc and IOPg were statistically different with the highest value in the warpage group followed by normal and keratoconus groups; the same trend was observed in central corneal thickness (CCT). The mean of IOPg was 14.94 ± 2.65, 13.7 ± 2.33, and 10.86 ± 3 and IOPcc was 15.73 ± 2.4, 15.28 ± 2.43, and 14.08 ± 2.55 in the warpage, normal, and keratoconus groups, respectively. IOPg and IOPcc in the warpage group (based on baseline diagnosis) did not regress to become closer to IOP of normal eyes after discontinuation of contact lens in their follow-up visits (P value for IOPg and IOPcc trends in the warpage group was 0.07 and 0.09 controlling for CCT, respectively). Both IOPcc and IOPg were significantly lower in keratoconic eyes in comparison with normal eyes. After correction for the confounding effect of CCT, a lower IOPcc in keratoconus versus warpage remained significant (P = 0.02).Conclusion:Both IOPcc and IOPg were statistically different with the highest value in the warpage group followed by normal and keratoconus groups, just like their CCT. After correction for the confounding effect of CCT, there was no statistically significant difference between the three groups in their measured IOPcc and IOPg except for IOPcc in keratoconus versus warpage (P = 0.02).

Yield of Display Modules of Corneal Tomography for Early Diagnosis of Corneal Ectasia.

The thesis deals with comparison of topographic corneal indexes and their importance for the diagnosis of corneal ectatic disease. The corneas with different stages of keratoconus, forme fruste keratoconus, pellucid marginal degeneration, corneal warpage syndrome, and physiological cornea with varying values of regular astigmatism were included in the tested group. The study was conducted in 2015-2018 at the European Eye Clinic Lexum Brno. The study group contained 208 eyes, 111 eyes with keratoconus, 31 eyes with forme fruste keratoconus, 23 eyes with pellucid marginal degeneration, 10 eyes with corneal warpage syndrome and 33 physiological eyes. 19 corneal parameters and indexes were monitored for these ectatic diseases, which were compared with healthy corneas with regular astigmatism. Asingle-factor ANOVA test, aStudent t-test were used for statistical analysis. Pearson'scoefficients were used to assess the correlation. In all the observed tomographic parameters astatistically significant difference was found between the physiological and ectatic group of corneas. The parameters with the highest statistical difference were BEThLo, ISV, IHD, D, Rmin. Statistically significant indices were also found between the forme fruste keratoconus and physiological corneas. The best parameters for detecting the subclinical keratoconus were the back elevation at the thinniest point of the cornea (BEThLo), the difference between the thinniest and the central point of cornea (CP-TL), the maximum pachymetic progression index and the Db and D indexes (p 0.6) according to Pearson'scorrelation coefficient. Statistically significant differences in the KK and PMD groups were found in the index of relative pachymetry, central pachymetry, CKI and Dp. Key words: Pentacam, corneal ectasia, keratoconus, pellucid marginal degeneration, corneal warpage syndrome, forme fruste keratoconus.

False corneal ectasia in patients referred for corneal crosslinking, topography-guided photorefractive keratectomy, and intrastromal corneal rings

To determine the misdiagnosis of ectasia in patients referred for corneal crosslinking and possible topography-guided photorefractive keratectomy (PRK) or intrastromal corneal rings. Bochner Eye Institute, Toronto, Ontario, Canada. Retrospective data review. Chart review of consecutive cases referred for corneal crosslinking to determine the number of cases of misdiagnosis of ectasia. Examination findings were reviewed consisting of best-corrected spectacle distance acuity, slit lamp examination, and computerized tomography. The study analyzed 1000 consecutive records of patients referred with a presumed diagnosis of keratoconus, pellucid marginal degeneration, and ectasia after laser vision correction that were examined between January 1, 2010 and November 1, 2016. There were 26 eyes without ectasia detected in 20 patients. The etiology of these misdiagnoses was epithelial basement membrane dystrophy (9 eyes), superficial punctate keratitis (7 eyes), amblyopia secondary to high astigmatism (3 eyes), amiodarone keratopathy (2 eyes), corneal warpage from rigid gas permeable lenses (2 eyes), corneal scars (1 eye), and measurement or alignment error with topography (2 eyes). Analysis of data detected a misdiagnosis of ectasia in 20 patients (26 eyes), a finding of 2.0% (20 of 1000) of referred cases that did not satisfy the diagnostic criteria of corneal ectasia. These conditions are considered a contraindication to corneal crosslinking and there is usually no benefit to topography-guided PRK or intrastromal corneal rings. It is important that clinicians recognize the clinical findings of these conditions and differentiate from true keratoconus, pellucid marginal degeneration, or ectasia after laser vision correction.

Influence of soft contact lens material on corneal warpage: prevalence and time to resolution

ObjectiveCorneal warpage represents a reversible distortion of the corneal surface induced by soft contact lens (SCL) wear. The aim of the study is to assess the influence of SCL materials, age, wearing duration, cylindrical refraction, and spherical equivalence on the prevalence and time to resolution of corneal warpage. MethodsThis is an interventional prospective study in which SCL wearers volunteered to remove their SCLs and underwent, on each visit, a corrected distance visual acuity and anterior and posterior segment evaluation, along with keratometry measurement and corneal topography. Visits were scheduled 30 minutes after SCL removal, on day 4, day 7, and then weekly after SCL removal until warpage resolution. ResultsA total of 17 volunteers (34 eyes) were included, with 9 (18 eyes) in the hydrogel SCL group and 8 (16 eyes) in the silicone hydrogel SCL group. The difference in warpage prevalence between the hydrogel group (28%, 5 eyes) and silicone hydrogel group (31%, 5 eyes) was not statistically significant (p > 0.90). Duration necessary for warpage resolution ranged from 7 to 21 days with no statistically significant difference between the 2 groups (p = 0.12). ConclusionsBoth types of SCL had similar corneal warpage prevalence and time to resolution, with slightly longer mean time to resolution with silicone hydrogel. All eyes had resolution of warpage by 3 weeks. It seems more cautious to wait longer than the usual 1-week interval before performing refractive surgery, especially in patients wearing SCL for long periods and regardless of the type of material.

Corneal Warpage After Discontinued Soft Contact Lens Wear

Corneal Warpage After Discontinued Soft Contact Lens Wear

Differentiating Keratoconus and Corneal Warpage by Analyzing Focal Change Patterns in Corneal Topography, Pachymetry, and Epithelial Thickness Maps.

PurposeTo differentiate between keratoconus and contact lens-related corneal warpage by combining focal change patterns in anterior corneal topography, pachymetry, and epithelial thickness maps.MethodsPachymetry and epithelial thickness maps of normal, keratoconus, and warpage, and forme fruste keratoconus (FFK) eyes were obtained from a Fourier-domain optical coherence tomography (OCT). Epithelial pattern standard deviation (PSD) was calculated and combined with two novel indices, the Warpage Index and the Anterior Ectasia Index, to differentiate between normal, keratoconus, and warpage eyes. The values of the three parameters were compared between groups.ResultsThe study included 22 normal, 31 keratoconic, 11 warpage, and 8 FFK eyes. The epithelial PSD was normal (< 0.041) for 100% normal eyes and abnormal (> 0.041) for 100% of keratoconic eyes, 81.8% of warpage eyes, and 87.5% of FFK eyes. The Anterior Ectasia Index of normal eyes (1.66 ± 0.74) was significantly lower than that for the keratoconus eyes (17.5 ± 7.17), the warpage eyes (2.98 ± 1.69), and the FFK eyes (6.95 ± 5.86). The Warpage Index was positive in all warpage eyes and negative for all keratoconic and FFK eyes except three wearing rigid gas-permeable contact lens.ConclusionsThe epithelial PSD can distinguish normal from keratoconus or warpage, but does not distinguish between these two conditions. The Anterior Ectasia Index is abnormal in keratoconus but not warpage. The Warpage Index is positive for warpage and negative for keratoconus, except in cases where keratoconus and warpage coexist. Together, the three parameters are strong tripartite discriminators of normal, keratoconus, and warpage.

Corneal Biomechanical Findings in Contact Lens Induced Corneal Warpage.

Purpose. To evaluate the difference in biomechanical properties between contact lens induced corneal warpage and normal and keratoconic eyes. Method. Prospective observational case control study, where 94 eyes of 47 warpage suspicious and 46 eyes of 23 keratoconic patients were included. Warpage suspected cases were followed until a definite diagnosis was made (warpage, normal, or keratoconus). Results. 44 eyes of 22 patients had contact lens related corneal warpage. 46 eyes of 23 people were diagnosed as nonwarpage normal eyes. 46 eyes of 23 known keratoconus patients were included for comparison. The mean age of the participants was 23.8 ± 3.8 years, and 66.2% of the subjects were female. The demographic and refractive data were not different between warpage and normal groups but were different in the keratoconus group. The biomechanical properties (corneal hysteresis or CH and corneal resistance factor or CRF) were different with the highest value in the warpage group followed by normal and keratoconus groups. CRF was 10.08 ± 1.75, 9.23 ± 1.22, and 7.38 ± 2.14 and CH was 10.21 ± 1.57, 9.59 ± 1.21, and 8.69 ± 2.34 in the warpage, normal, and keratoconus groups, respectively. Conclusion. Corneal biomechanics may be different in people who develop contact lens induced warpage.

Novos conceitos em modelamento corneano

The cornea has a great influence in the visual process. However, it is liable to distortion, such as flattening. When this flattening is caused by the use of contact lenses, we call “corneal warpage”. In this case, some symptoms may occur as blurred vision with glasses, conjunctival hyperemia, foreign body sensation, etc… Used to think that the cornea was more rigid and, in time, realized that the cornea has viscoelastic properties. We can say that the cornea has a body [...]

A Quantitative Method for the Analysis of Bilateral Corneal Asymmetry in Different Corneal Categories

Purpose It is generally accepted that the presence of bilateral corneal asymmetry correlates with certain corneal diseases and may be the evidence of corneal abnormalities. A method is shown for the quantification of bilateral corneal asymmetry in 5 different corneal categories, making use of corneal topography data. Methods Corneal topographies (Tomey TMS, Nagoya, Japan) from both eyes of 74 subjects were reviewed by a cornea researcher who classified them according to their characteristics into five groups (normal, astigmatic, contact-lens-induced corneal warpage, keratoconus suspects and bilateral keratoconus). Topography maps were chosen from the clinical records of the LSU Eye Center. The axial-diopters tables for each pair of corneas were extracted from their corresponding corneal topographies. The resulting data from the corneal topographies of each eye were interpolated at regular intervals using a polar-coordinate system. Subsequently, the differences between corresponding points of the axial-diopters tables of the fellow eyes were calculated. The cumulative percentage of the resulting values was calculated and its distribution was plotted for each pair of eyes. A linear regression was fitted to the data of each cumulative distribution plot. Finally, the slope of the linear regression of each pair of eyes was calculated and statistical analysis was performed in order to determine whether or not there is a statistically significant difference between the slopes of each group of corneal categories. Results A statistically significant difference ( P<0.05) was found between keratoconus and all the other groups. Furthermore, we found a statistically significant difference between the normal and the contact-lens-induced warpage group as well as between the normal and the keratoconus-suspects group ( P<0.05). There was no statistically significant difference ( P>0.05) neither between the normal and the astigmatism group, nor between the astigmatism and the contact-lens-induced corneal warpage group, nor between the astigmatism and the keratoconus-suspects group, nor between the keratoconus-suspects group and the contact-lens-induced corneal warpage one. Conclusions A method to quantify bilateral corneal asymmetry in different corneal entities was devised. The lowest degree of bilateral asymmetry was observed in the normal group, while the highest degree of bilateral asymmetry was obtained for the keratoconus group. The contact-lens-induced warpage group and the keratoconus-suspects group presented with intermediate bilateral asymmetry.

Corneal stability after discontinued soft contact lens wear

Purpose To determine the time needed to reach corneal stability after discontinued daily wear of soft contact lenses and to identify corneal topographic and pachymetric changes during this period. Methods We prospectively studied the eyes of 21 consecutive soft contact lens wearers evaluated for keratorefractive surgery. Each eye was examined once immediately after lens removal, 3 and 7 days later, and weekly thereafter. At each visit, manifest refraction, keratometry, corneal topography (EyeSys Corneal Analysis system, EyeSys Laboratories, Houston, TX) and pachymetry were performed. Incidence of associated corneal warpage and changes in corneal curvature and thickness during corneal stability time were determined. Results Of the 42 eyes examined, 26 corneas showed no significant change after the initial evaluation (stable group). The minimum stability time was 3 days in the remaining 16 eyes (unstable group), 7 of which had significant evidence of abnormal topography. Statistical analysis showed no significant differences between two groups regarding age, sex, duration of contact lens wear, and refractive and topographic measures. The mean central corneal thickness on the final visit was significantly different between two groups ( P < 0.05). Conclusion Contact lens induced corneal warpage may occur in a considerable proportion of soft contact lens wearers. A 2-week contact lens free period seems to be adequate for the cornea to stabilize; however, one cannot predict the minimum time needed for each individual patient. Repeating examinations to document corneal stability before refractive surgery may be a safer alternative.

Mistaken Diagnosis of Keratoconus Because of Corneal Warpage Induced by Hydrogel Lens Wear

We report a case of corneal warpage secondary to hydrogel lens wear that was initially mistaken as a case of keratoconus. A 26-year-old Chinese female hydrogel lens wearer presented with an interest in refractive surgery. After topographies and pachymetries were performed, keratoconus was initially diagnosed for her right eye and suspect keratoconus diagnosed for her left eye. This conclusion was felt to be confirmed at a follow-up visit 1 week later, but keratoconus contact lens treatment was delayed because of the presence of superficial punctate keratitis. After 8 weeks without lens wear, corneal maps were performed again. The maps now showed regular with-the-rule astigmatism, and none of the previous evidence of keratoconus. Central pachymetries were also normal. Soft contact lens wear can induce corneal warpage mimicking keratoconus. Had the standard treatment for keratoconus been implemented before resolution of the warpage, it could have proven injurious to the patient, because the treatment itself could have provided an impetus for the protrusion to remain or perhaps even progress. Our case gives clinicians reason to pause when dealing with contact lens wearers presenting with corneal curvature irregularities such as keratoconus or ectasia, because of the possibility of lens-induced warpage.

Goodness-of-prediction of Zernike polynomial fitting to corneal surfaces

To determine the goodness-of-prediction of the fitting routine by measuring the difference between topographic corneal surfaces and their Zernike reconstructions as a function of polynomial order and optical zone size for various corneal conditions. Corneal research laboratory in a university eye center. Corneal topography maps (N = 253) were obtained from the Louisiana State University Eye Center. A variety of corneal conditions were used: normals; astigmatism; laser in situ keratomileusis, photorefractive keratoplasty (PRK), and radial keratotomy (RK) postoperative cases (myopic spherical corrections); keratoconus suspect; mild, moderate, and severe keratoconus; pellucid marginal degeneration; contact lens-induced corneal warpage; and penetrating keratoplasty. The root-mean-square (RMS) error of the goodness-of-prediction of the Zernike representation of corneal surface elevation was extracted for 4, 6, and 10 mm optical zones, whereas Zernike radial orders were varied from 3 to 14 in 1-order steps. The mean +/- SEM of the RMS error was plotted as a function of Zernike order and compared with criteria for normal surface fits. Fitting accuracy improved as more Zernike terms were included, but some conditions showed significant errors (when compared with normal surfaces), even with many added terms. For a 6 mm optical zone, the normal cornea group had the lowest RMS error and did not require terms above the 4th order to achieve <0.25 microm RMS error. Astigmatism met the 0.25 microm threshold at the 5th order, whereas keratoconus suspect required 7 orders. Laser in situ keratomileusis and PRK met the 0.25 microm threshold at the 8th order, whereas RK required 10 orders. Contact lens-induced corneal warpage and mild keratoconus needed 12 orders to meet the 0.25 microm threshold, whereas pellucid marginal degeneration, moderate and severe keratoconus, and keratoplasty categories were not well fitted even at 14 orders. A 4th-order Zernike polynomial appeared reliable for modeling the normal cornea, but using a 4th-order fitting routine with an abnormal corneal surface caused a loss of fine-detail shape information. As more Zernike terms were added, the accuracy of the fit improved, and the result approached the minimum error found with normal corneas. Unless sufficient higher-order Zernike terms are included when analyzing irregular surfaces, some diagnostic applications of Zernike coefficients may not be rigorous. This conclusion also suggests that wavefront shape analysis is similarly dependent on the number of orders used. Current surgical corrections based on normal-eye wavefronts may fail to capture all visually relevant aberrations in abnormal eyes, such as those having laser retreatments or experiencing corneal warpage from contact lens wear. A clinical goodness-of-fit or goodness-of-prediction index would indicate whether the number of terms in use has fully accounted for all of the visually significant aberrations present in the eye.

Predicting time to refractive stability after discontinuation of rigid contact lens wear before refractive surgery

Purpose: To determine whether discontinuing rigid contact lenses for 3 weeks is sufficient to achieve refractive stability and if not, to identify factors, including indicators of corneal warpage, that are associated with prolonged corneal instability. Setting: University-based refractive surgery practice. Methods: Charts of patients seen for refractive surgery consultation from January 1999 to March 2001 were reviewed. Patients with a history of rigid gas-permeable (RGP) contact lens use were identified and instructed to discontinue wearing lenses 3 weeks before the initial examination. Patients were examined at 3-week intervals until a stable refraction was achieved (within ±0.25 diopter [D] sphere and 0.25 D cylinder with less than 25 degrees of axis orientation). Visual acuity, subjective refraction, and corneal topography were obtained at each visit. Results: Of 55 eyes of 28 patients, 31 eyes achieved refractive stability by the second visit (early-stability group) and 24 eyes required more than 2 visits to achieve stability (late-stability group). No statistically significant between-group difference was observed in age, sex, refractive cylinder, topographic cylinder, difference between refractive and topographic cylinders, surface regularity index, surface asymmetry index, or spherical equivalent at the initial examination. The number of years of contact lens wear was significantly different between the groups ( P = .05). Conclusions: The time for contact lens-induced corneal changes to reach a steady state after cessation of lens wear is highly variable. Among the variables examined, including those indicating corneal warpage, the factor that correlated with the required time to refractive stability after discontinuation of RGP wear was the length of time of contact lens use. Patients who are long-term RGP wearers should be counseled that multiple visits will likely be required before a stable refraction is obtained.

Hydrogel contact lens-induced corneal warpage

Background: Although contact lens-induced corneal warpage is most frequently associated with PMMA lenses, approximately 27% of reported cases of corneal warpage have been attributed to hydrogel lens wear. The change in corneal contour may be the result of either mechanical deformation, chronic metabolic insult, or a combination of mechanical and metabolic challenges. Limited oxygen transmissibility through some hydrogel lenses may lead to chronic hypoxia and acidosis. These metabolic challenges can change corneal physiology sufficiently to cause clinically significant corneal warpage. Case reports: Three cases of hydrogel contact lens-induced corneal warpage are presented. In all three cases, cessation of lens wear led to restoration of the normal corneal contour and visual acuity. All patients were refit with more oxygen-permeable lenses, and have successfully resumed wearing contact lenses. Conclusion: Certain individuals who wear hydrogel contact lenses can experience corneal warpage. Clinical signs of corneal warpage include changes in refractive error, decreased visual acuity with spectacle correction, and changes in corneal topography. Serial topography is useful to monitor the cornea to resolution of the condition. Contact lenses with higher oxygen transmissibility will frequently alleviate the relative hypoxia that may be associated with corneal warpage.

Time to resolution of contact lens-induced corneal warpage prior to refractive surgery.

To evaluate the resolution of contact lens-induced corneal warpage before keratorefractive surgery. We prospectively studied the eyes of 165 consecutive contact lens-wearing patients evaluated for keratorefractive surgery. Significant contact lens-induced corneal warpage was detected by comeal topography in 20 eyes of 11 patients. Manifested refraction, keratometry, and cornea topography were subsequently recorded during weekly or biweekly reevaluations and were compared with previous measurements for stability. Effects of age, sex, type, and duration of contact-lens wear and the recovery time period to stabilization were analyzed. Overall, a 12% incidence of significant contact lens-induced corneal warpage was found. In patients demonstrating lens-associated warpage, the mean duration of prior contact lens wear was 21.2 years (range 10 to 30 years); lens use included daily wear soft (n=2), extended-wear soft (n=6), toric (n=4), and rigid gas-permeable contact lenses (n=8). Up to 3.0 diopter (D) refractive and 2.5D keratometric shifts accompanied by significant topography pattern differences were observed. The average recovery time for stabilization of refraction, keratometry (change within +/- 0.5D), and topography pattern was 7.8+/-6.7 weeks (range 1 to 20 weeks). Recovery rates differed between the lens types: soft extended-wear 11.6+/-8.5 weeks, soft toric lens 5.5+/-4.9 weeks, soft daily wear 2.5+/-2.1 weeks, and rigid gas-permeable 8.8+/-6.8 weeks. We observed a 12% incidence of significant contact lens-induced corneal warpage in patients undergoing evaluation for keratorefractive surgery. Warpage occurred with all types of contact lens wear but resolved at different rates. To optimize the quality and predictability of keratorefractive procedures, an appropriate waiting period is necessary for contact lens-induced corneal warpage to stabilize. We suggest that resolution of corneal warpage be documented by stable serial manifested refractions, keratometry, and corneal topographic patterns before scheduling patients for keratorefractive surgery.

Deformidade corneana em usuário de lente de contato portador de ceratocone: relato de caso

Introdução: Alterações topográficas podem ocorrer secundariamente ao uso de uso de lentes de contato duras ou gelatinosas. O termo "corneal warpage" é utilizado para denominar as deformidades corneanas causadas pelas lentes. O quadro topográfico da fase inicial do ceratocone pode ser muito parecido com o de um paciente com este quadro. Objetivo: Mostrar um paciente portador de ceratocone, usuário de lentes de contato rígida gás-permeável (RGP) que desenvolveu quadro de "corneal warpage", diagnosticado e acompanhado por topografias e exames clínicos seriados. Relato de caso: O paciente é um engenheiro de 40 anos com diagnóstico de ceratocone bilateral há 12 anos, usando lentes RGP desde então. No primeiro exame em 5/95, a refração de OD foi impossível de se determinar e a ceratometria era maior que 60,00 D. Foi feita topografia, que se mostrou compatível com ceratocone, tendo sido adaptada uma lente Soper, com visão de 20/70. Após um ano, uma topografia de controle mostrou aumento da curvatura central e aplanamento da periferia inferior. O uso da lente foi suspenso e após 6 meses houve regressão das mudanças, tendo sido adaptadas novas lentes com melhor padrão e visão de 20/40. Discussão: O caso apresentado evidencia a ocorrência de deformidade corneana em um portador de ceratocone usuário de lente RGP. O autor discute a fisiopatologia e o diagnóstico clínico e topográfico do "corneal warpage", lembrando que a exemplo de pacientes normais, os pacientes com ceratocone podem apresentar estas alterações, que devem ser diferenciadas da própria evolução da doença.

Evaluation of mild, moderate, and advanced keratoconus using ultrasound pachometry and the EyeSys videokeratoscope.

The absolute accuracy of videokeratoscope (VKS) mapping of keratoconus is still in question, with contact lens-induced corneal warpage and chalazion having been shown to resemble this condition closely. Corneal thinning is investigated as a further aid to the diagnosis and description of keratoconus. The diagnosis of keratoconus in 41 individuals was verified by measuring the corneal thickness difference (I-S difference) between two disparate corneal locations, one inferior to (I) and one superior to (S) the corneal apex, using a Humphrey model 870 Ultrasound pachometer. Corresponding measures of I-S radii were made using radius values obtained from the EyeSys VKS. A comparison between I-S pachometry and I-S radius demonstrated a marginally increased sensitivity for the latter measurement. Using 95% confidence levels from normative pachometric data, classification of severity of keratoconus is proposed as follows: (1) keratoconus suspect/early keratoconus: I-S pachometry 75 to 100 microns; (2) moderate keratoconus: 100 to 125 microns; and (3) advanced keratoconus: > 125 microns. I-S pachometry can be used as a descriptor of keratoconus.

Corneal warpage (pseudokeratoconus) and soft toric contact lenses: a case report

Corneal warpage or pseudokeratoconus is a change in corneal contour, resulting in either an increase or decrease in astigmatism accompanied by either a generalized flattening or steepening of the cornea.1 Corneal warpage is usually a reversible process often attributable to wearing of rigid contact lenses.2,3 Corneal topography maps in cases of corneal warpage will show lack of radial symmetry, accompanied by peripheral steepening.3 This case report presents evidence that corneal warpage also may be caused by the wearing of soft toric contact lenses. Steepening of the cornea, detectable via corneal topography, may not be sufficient to distinguish corneal warpage or pseudokeratoconus from keratoconus. However, typical presenting signs of keratoconus—Vogt’s striae and Fleischer’s ring—will be absent in corneal warpage or pseudokeratoconus. Topographic maps of the cornea fall into two general types of displays related to curvature. ROC-D displays (radius of curvature tangent to a corneal surface point), sometimes called the “tangential” display, is a scaled curvature. The second type of display, AD-D or “sagittal,” is measured from an axial distance point normal to the corneal curve at that meridian. Although both scales are measured in dioptric values, they are quantitatively different yet qualitatively similar. The AD-D or sagittal scale is a less detailed, “smoothed” representation that is a running average of the ROC-D (tangential) scale. The sagittal scale is useful for fitting contact lenses. A keratoconus patient will show a large, diffuse area of steepening on an AD-D or sagittal map, due to the “averaging” effect. On the ROC-D or tangential map, the keratoconic cone will be smaller and the steepest part will be more central, corresponding to the actual location of the cone.4 However, corneal steepening in pseudokeratoconus extends to the limbus on a tangential map.