Intereye asymmetry in bilateral keratoconus, keratoconus suspect and normal eyes and its relationship with disease severity.

BACKGROUND/AIM: To describe the intereye asymmetry in patients with keratoconus (KC), keratoconus suspect (KCS) and normal participants, and to evaluate the relationship between asymmetry and disease severity. METHODS: In this prospective observational comparative study, 446 patients with bilateral KC, 68 patients with bilateral KCS and 306 normal participants underwent topographic, keratometric and pachymetric evaluations by Pentacam as well as refractive and visual acuity examinations. The intereye asymmetry in each parameter was calculated and compared between the groups. RESULTS: All parameters were significantly different between the worse and better eyes in the KC group (p<0.05), but not in the KCS and normal groups. No significant differences were observed in the measurements of the worse and better eyes of the normal group (p>0.05). There was a statistically significant greater intereye asymmetry in all parameters in the KC group compared with the KCS and normal groups (p<0.05). The intraclass correlations were poor in patients with KC, moderate to good in patients suspected with KC and strong in normal participants. There were statistically significant relationships between the intereye asymmetry in all parameters and KC severity in the worse eye in which intereye asymmetry significantly increased with an increase in disease severity, based on Keratoconus Severity Score classification (p<0.05). According to receiver operating characteristic analysis, the intereye asymmetry would effectively discriminate KC and KCS from normal eyes. CONCLUSION: KC is an asymmetric disease, and the degree of asymmetry is associated with disease severity. The analysis of intereye asymmetry should be performed along with unilateral evaluation in the screening of KC.

Effect of Allergic Diseases on Keratoconus Severity.

PURPOSE: To investigate the association between keratoconus (KC) and allergic diseases. METHODS: In a prospective age- and sex-matched case--control study clinical data of 885 KC patients and 1526 controls were evaluated regarding the presence of various allergic diseases. Severity of KC and ophthalmic parameters of KC patients were compared between KC patients with and without allergic diseases. RESULTS: The prevalence of allergic diseases was significantly higher in KC patients. KC patients with vernal keratoconjunctivitis (VKC) or allergic conjunctivitis (AC) had significantly thinner and steeper corneas in comparison with non-allergic KC patients. Only VKC and AC were significantly associated with KC severity. CONCLUSIONS: Patients with VKC or AC were at increased risk of KC. They had more severe KC and should be closely followed up and intensively treated.

Is keratoconus more severe in pediatric population?

PURPOSE: To compare the ophthalmic parameters and the severity of keratoconus (KC) in pediatrics and adults at the time of initial diagnosis in an Iranian population. METHODS: KC was diagnosed via slit-lamp examination and Pentacam imaging. In a retrospective observational study, consecutive patients were divided into two groups of pediatrics (<18 years old) and adults (>18 years old). Topographic, keratometric, and tomographic parameters, and severity of KC at the time of diagnosis were compared in both groups. Severity of KC was classified according to Amsler-Krumeich classification. RESULTS: One hundred fifty-eight eyes of 158 pediatric patients and 343 eyes of 343 adults with KC were studied. The mean ages of the pediatric and adult patients were 15 ± 1.9 and 22 ± 1.9 years, respectively (p < 0.001). The results revealed that pediatric patients had significantly higher values of anterior and posterior mean, flat and steep keratometry, astigmatism, and maximum elevation and significantly lower central and thinnest corneal thickness (p < 0.05). No significant difference was found regarding sphere, cylinder, manifest refraction spherical equivalent, and uncorrected and best-spectacle corrected visual acuity between the groups (p > 0.05). Pediatric patients had a significantly more severe KC than adult patients according to Amsler-Krumeich classification (p = 0.001). CONCLUSION: Our findings suggest that KC is more severe in pediatrics, hence the fact that they should be closely monitored and intensively treated.

Association between Family History and Keratoconus Severity.

PURPOSE: The high prevalence of positive family history of keratoconus (KC) in KC patients is well-known. However, the results regarding the association between family history of KC and disease severity are controversial. The aim of this study was to evaluate the possible association between family history and severity of KC. METHOD: Clinical data of 1496 KC patients were evaluated. All participants were asked if they had had a family member with KC. Topographic and keratometric measurements of KC patients, including central corneal thickness (CCT), thinnest corneal thickness (TCT), mean, flat, and steep keratometry values (K) by the use of Pentacam, best-spectacle corrected visual acuity (BCVA), spherical equivalent (SE), and astigmatism were recorded and compared according to patients with and without a family history of KC, first- or second-degree family members, and the number of family members with KC. Severity of KC was classified according to the Amsler-Krumeich classification. RESULTS: Family history of KC was present in 292 (19.5%) patients. Of those 292 patients who had a family history of KC, 159 (54.5%) had one family member with KC and 133 (45.5%) had two or more family members with KC. There was not a significant difference between corneal pachymetry and K values of the patients with and without a family history of KC (p > 0.05). However, those with a positive family history of KC had more severe disease, according to the Amsler-Krumeich classification (p < 0.05). KC patients who had more family members with KC had significantly lower TCT and significantly higher steep K and astigmatism (p < 0.05), and had more severe disease, according to the Amsler-Krumeich classification (p < 0.05). CONCLUSION: We suggest that patients with more family members with KC should be subject to screening to identify early disease.

Distribution of Anterior and Posterior Corneal Astigmatism in Eyes With Keratoconus.

PURPOSE: To investigate the magnitude, with-the-rule (WTR) or against-the-rule (ATR) orientation, and vector components (Jackson astigmatic vectors [J0 and J45] and blurring strength) of the anterior and posterior corneal astigmatism (ACA and PCA) in patients with keratoconus (KC) in a retrospective study, and to try to find suitable cutoff points for ACA and PCA in an attempt to discriminate KC from normal corneas. DESIGN: Retrospective age- and sex-matched case-control study. METHODS: Using the Pentacam images, the aforementioned parameters were compared between 1273 patients with KC and 1035 normal participants. RESULTS: The mean magnitude of the ACA and PCA was 4.49 ± 2.16 diopter (D) and 0.90 ± 0.43 D, respectively. The dominant astigmatism orientation of the ACA was ATR in KC patients and WTR in normal participants (P < .001), while for the PCA it was WTR in KC patients and ATR in normal participants (P < .001). There was a significant agreement between the axis orientations of ACA and PCA in KC patients (ĸ = 0.077, P < .001), but not in the normal group (P = .626). ACA and PCA magnitude, M, J0, J45, and blur significantly increased by increasing KC severity. There was a trend for increasing anterior ATR and posterior WTR, and decreasing oblique astigmatism on both corneal surfaces by increasing the KC severity according to the Amsler-Krumeich classification. A cutoff value of 1.8 D for ACA had 90.2% sensitivity and specificity, and that of 0.4 D for PCA had 89.5% sensitivity and 85.0% specificity for discriminating KC from normal corneas. CONCLUSION: Our findings can help clinicians in the diagnosis of KC and lens manufacturers in designing suitable contact or intraocular lenses.

Utility of orthokeratology contact lenses; efficacy of myopia correction and level of patient satisfaction in Iranian myopic/myope-astigmatic patients.

PURPOSE: To investigate the medical profiles of patients referred to Iran Lens Clinic with myopic/myope-astigmatic refractive errors. METHODS: Medical records of 182 patients (364 eyes) with myopic/myope-astigmatic refractive errors that underwent orthokeratology contact lens wear and fulfilled a 6-month period of follow-up were recruited. Efficacy and safety of these contact lenses in improving the visual acuity and correction of the refractive errors were investigated. Time needed to achieve final targeted visual acuity and association of various factors in this time course and level of acuity were investigated. Complications related to these lenses that were recorded in the medical profiles were studied. RESULTS: In manifest refraction, the amount of spherical equivalent and myopia decreased significantly after orthokeratology contact lens wear (P < 0.001). A significant negative association was found between amount of mean baseline spherical equivalent and final achieved mean uncorrected visual acuity (P < 0.001). None of the parameters of age, gender, and keratometric findings influenced the outcomes significantly (P > 0.1). CONCLUSION: Patients with myopic refractive error lower than -5.0 Diopters achieved higher final visual acuities rather than patients with higher amounts of myopic refractive errors.

Rigid contact lens fitting based on keratometry readings in keratoconus patients: predicting formula.

AIM: To find a simple mathematical correlation between the lens base curve (BC) and keratometry findings (krf). METHODS: This retrospective study included 400 keratoconic eyes (350 patients) previously fit with rigid contact lenses at an academic eye center over a five year period. The patients were classified into five groups based on the keratometry findings (krf<7, krf:7-8, krf>8, krf-krs (difference between two keratometry; flat and steep)= 0.3-0.6, krf-krs >0.6mm as groups 1 to 5, respectively. Multivariate linear regression and Munro's correlation coefficient were employed to defer the formulas. RESULTS: A linear correlation could be found in all groups except for patients in group 3. For group 1, BC=0.211×krf+ 5.904. For group 2, BC=0.456×krf+4.160. For group 4, BC= 0.321×krf+5.219. For group 5, BC=0.337×krf+ 5.090. CONCLUSION: The development of new formulas for RGP fitting enables ophthalmologists to work with confidence and prevents unnecessary and frequent lens trials. The customary lens fitting methods are needed to be replaced by new formulas, which help to save time and costs.