Table 7 - uploaded by Raúl Peralta-Rodríguez
Content may be subject to copyright.
Source publication
Background
The purpose of this study was to determine the prevalence of refractive errors in Mexican patients with keratoconus (KCN) and to describe their clinical characteristics.
Methods
In this retrospective study, we reviewed the records of Mexican patients with KCN for the year 2012. Criteria for classifying refractive errors included the fol...
Context in source publication
Citations
... years old, which is very close to another study done in Egypt by Elbedewy et al. [23] in which the mean age of onset was 29.40±9.79 years old, Cruz-Becerril et al. [32] with an onset at 28.14±10.30 years of age, in European countries as the mean age of the KC patients at time of diagnosis was 23-28 years [4,33,34] and Ljubic study in which the mean age of onset was 26.81±1.25 years [35] . ...
... The most common refractive error in KC is compound myopic astigmatism, with the incidence rate in different studies reported from 69.7% to 85.7%. Types of astigmatism (with-the-rule, against-the-rule, oblique) are different depending on stages of KC [20,21]. Frequency of high astigmatism (> 2 D) is significantly higher in population with KC and subclinical KC (14.1%) than in the normal population (6.86%) [22][23][24]. ...
... The most prevalent type of astigmatism was against-the-rule (50.7%) and oblique astigmatism (22.6%). Cruz-Becerril et al. reported higher prevalence of compound myopic astigmatism and with-therule astigmatism as dominant [21]. Using schematic eye models Tan et al. stated that cone location is the most important factor in vision distortion. ...
Aim of the study: To evaluate selected visual system parameters in keratoconus patients and establish criteria which will enable better screening for keratoconus. Material and methods: 146 eyes of 73 patients diagnosed with keratoconus were included in the study. Each patient underwent optometric and ophthalmological examination with corneal tomography. Results: We found a statistically significant inter-eye difference between the better and worse eye in median values of uncorrected (0.24 vs. 0.62 LogMAR) and best corrected (0.03 vs. 0.24 LogMAR) distance visual acuity. Our study also showed statistically significant differences in median values of keratometry between the better and worse eye (K1 43.1 vs. 45.4 D, K2 45.2 vs. 49.0 D), mean values of thinnest central cornea (TCC) (488 vs. 458 µm) and median grade 1.5 and 2.5 for the better and worse eye, respectively. The most prevalent refractive error was compound myopic astigmatism, followed by hyperopic compound or mixed astigmatism. Conclusions: Keratoconus should be suspected in patients with inter-eye differences in manifest refraction, especially when astigmatism exists. Any inter-eye asymmetry in keratometry or pachymetry values should be an indication for full keratoconus screening.
... 1,2 The onset of the condition is common in the first or second decade of life, progressing until the third or fourth decade before regaining stability. 3,4 The extent of the progression depends on the interplay between the environmental context, genetic factors, time of onset as well as diagnostic and intervention methods used. 5,6 The prevalence of KC has been reported in multiple countries, including the United States (500 cases per 100,000 people), Japan (9 per 100,000 people), India (2300 per 100,000 people), Israel (2340 per 100,000 people), Macedonia (7 per 100,000 people), Iran (2400 per 100,000 people), the Netherlands (13,300 per 100 000 people), China (27 per 100,000 people) and Egypt (170 per 100 000). ...
... The similar visual acuity outcomes between corneal and scleral lenses highlight the ability of both lens designs to mask high amounts of irregular astigmatism in correcting the refractive errors. 3 The majority of patients in our study had high myopia and astigmatism (presented as spherical equivalent) progressing to the level of blindness (Figure 2A). After lens correction, the magnitude of the refractive errors significantly (p=0.001) ...
Introduction
Visual acuity (VA) and refractive error (RE) remain important parameters in the management of keratoconic (KC) patients. Despite rapid amelioration in capacity of diagnostic equipment, these remain inaccessible to the majority of practitioners in low-income countries. Notwithstanding limitations, practitioners are expected to utilize existing resources to satisfactorily manage their increasing numbers of keratoconic patients.
Purpose
To determine the changes in visual acuity and refractive errors with diagnostic and management options available in low-income contexts.
Methods
A descriptive, retrospective chart analysis of medical records dating back 5 years was employed in this study. Records of patients prescribed with corneal rigid gas permeable (RGP) and scleral lenses were analyzed. Data on age, gender, stage of keratoconus, pre-, and post-visual acuities and refractive errors, mode of correction and lens parameters were evaluated.
Results
A total of 124 medical records were analyzed. Males comprised 58.9% and females 41.1% of the total sample, with a mean age 20.86 ± 9.50 years. The mean unaided VA in logMAR notation was 1.0±0.19, while corrected VA was 0.18±0.17. There was a significant improvement (p=0.001) in VA with corneal RGP contact lenses (mean 0.19±0.17) as compared to unaided VA (mean 1.29±0.20). Scleral lens VA also improved from a median of 1.06 to −0.01 logMAR; p=0.001. The mean RE before RGP contact lens fitting was −9.43±2.37 diopters (D) which improved to −0.41±0.78D. RE reduced significantly (p=0.001) after fitting with both corneal RGP lenses (from a mean of −9.80±4.46D to −0.45±0.80D) and scleral lenses (from a median of −8.00D to −0.02D).
Conclusion
Significantly improved visual acuity and refractive error status were achieved with all KC patients. Despite the diagnostic equipment and contact lenses design limitations, practitioners in low-income contexts can fit the relatively more affordable corneal RGP lenses to positively impact the daily living experiences of their KC patients.
... A more recent study by Cruz-Becerril et al. assessed the prevalence of refractive errors in Mexican patients diagnosed with KC. They found that, out of 785 eyes with keratoconus, compound myopic astigmatism was the most frequent refractive error in eyes, being present in 87.5% of keratoconic corneas [22]. ...
... Nevertheless, Cruz-Becerril et al. found that in all grades of KC, 3 refractive errors were most frequent: with-the-rule compound myopic astigmatism, oblique compound myopic astigmatism, and against-the-rule compound myopic astigmatism. Additionally, myopia was present in the advanced and severe stages, but no other refractive errors were observed at either stage [22]. ...
... KC usually starts to develop at the age of puberty. In this study, the mean age of patients with KC at time of diagnosis was 29.40 ± 9.79 years old, which is very close to Ljubic study in which the mean age of onset was 26.81 ± 1.25 years [15], the studies by Pobelle-Frasson et al. [23] with 33.4 years in males and 37.1 years in females, and Cruz-Becerril et al. [22] with an onset at 28.14 ± 10.30 years of age. This was much younger than Hashimi et al. [16] who reported a mean age of 47.6 years at the time of diagnosis. ...
PurposeTo study the prevalence of keratoconus (KC) and the topographical characteristics of the affected corneas in patients with refractive errors who were seeking refractive surgery in the Egyptian delta. MethodsA retrospective study covering four and half years (Jan 2012–June 2016) where the topographical data of 8124 participants were obtained from the records of a refractive center in the Nile delta region, Egypt. The diagnosis of KC was based on the Holladay criteria in one or both eyes, using the Pentacam scans, whereas grading of KC was based on the Amsler-Krumeich classification. ResultsThe prevalence of KC was 1.12% (91/8124 participants) with 95% confidence interval 0.91–1.3. Of all the affected cases, 5 cases (5.5%) had unilateral, and the other 86 cases (94.5%) had bilateral KC. The affected and unaffected subjects did not show any significant difference regarding gender. Sixty-eight (38.4%) eyes had stage 1 KC, 53 eyes (29.9%) had stage 2, 27 eyes (15.3%) had stage 3, and 29 eyes (16.4%) had stage 4 KC. It was most prevalent (1.2%) among cases with astigmatism (P < 0.001). Conclusion
Keratoconus was found in 1.12% of patients seeking refractive surgery, with no gender preference. Most cases had bilateral affection. Astigmatism was the most common refractive error to be associated with keratoconus.
... There is lack of agreement among different studies regarding the definition of myopia and hyperopia. While most of the authors have considered MRSE as the defining criterion [1, 11, 12, 17, 21, 24 -26, 29, 37], others have included the spherical errors only [2,13,38]. Such a method of presentation may potentially result in the under-representation of myopic/hyperopic refractive errors in a population as only the patients with no astigmatism (< 0.5 D) will be categorized as myopia/hyperopia. ...
Background
Refractive errors are a form of optical defect affecting more than 2.3 billion people worldwide. As refractive errors are a major contributor of mild to moderate vision impairment, assessment of their relative proportion would be helpful in the strategic planning of health programs.
Purpose
To determine the pattern of the relative proportion of types of refractive errors among the adult candidates seeking laser assisted refractive correction in a private clinic setting in Saudi Arabia.
Methods
The clinical charts of 687 patients (1374 eyes) with mean age 27.6 ± 7.5 years who desired laser vision correction and underwent a pre-LASIK work-up were reviewed retrospectively. Refractive errors were classified as myopia, hyperopia and astigmatism. Manifest refraction spherical equivalent (MRSE) was applied to define refractive errors.
Outcome Measures
Distribution percentage of different types of refractive errors; myopia, hyperopia and astigmatism.
Results
The mean spherical equivalent for 1374 eyes was -3.11 ± 2.88 D. Of the total 1374 eyes, 91.8% (n = 1262) eyes had myopia, 4.7% (n = 65) eyes had hyperopia and 3.4% (n = 47) had emmetropia with astigmatism. Distribution percentage of astigmatism (cylinder error of ≥ 0.50 D) was 78.5% (1078/1374 eyes); of which % 69.1% (994/1374) had low to moderate astigmatism and 9.4% (129/1374) had high astigmatism.
Conclusion and Relevance
Of the adult candidates seeking laser refractive correction in a private setting in Saudi Arabia, myopia represented greatest burden with more than 90% myopic eyes, compared to hyperopia in nearly 5% eyes. Astigmatism was present in more than 78% eyes.
... Files of patients with incomplete data including unavailability of topographic measures, those without a data of keratometry and or refraction, those with history of ocular injuries or previous corneal refractive surgeries were excluded. Data were collected by using a data collection sheets (computerized excel Microsoft 2010) including age, sex, refractive errors and severity of keratoconus by the highest axis of corneal power on keratometry classified into mild (<48 D), moderate (48-54 D) and severe (< 54 D) [31]. ...
Introduction: Keratoconus is an ectatic disease of the cornea characterized by central or paracentral thinning and steepening that causes a cone-like protrusion of the cornea resulting in reduction in patient's visual acuity usually with progressive myopia and astigmatism. This study was conducted to investigate the prevalence of refractive errors and grading among a sample of Syrian patients with Keratoconus.
Methods and Materials: It is a prospective cross-sectional study conducted at Damascus hospital in Syria between the period (September 2021 till the end of April 2022). The study included both newly diagnosed patients as well as patients doing checkups for their previously diagnosed KCN at the time of study. The topographical variables studied are as follows: Kmax, TL, Pachy apex, and maximum posterior and anterior elevation data measured with (BFTE) reference body within the 8-mm diameter zone. Uncorrected and best corrected distal visual acuities were determined by subjective refraction tests. A phoropter was used to subjectively define the patient's eyeglass prescription and refraction errors. All done without cycloplegic drugs
Results: The sample size analyzed was 93 patients corresponding to 173 eyes. Unilateral involvement was (7.5%) and bilateral KCN was (92.5%) with a male to female distribution (44.1%) to (55.9%) respectively. Mean age was 29.7 ±10.9 within the range of [ 9 - 72 years]. The mean values for topographical variables measured were as follows: K.max (52.7 ± 6.07 D [range; 43 - 74.5]), TL (473.3 ± 43.1 µm [range; 343 - 609]), Pachy (486.05 ± 41.17 µm [range; 369 - 612]), Maximum anterior elevation (14.53 ± 10.08 µm [range; 2 - 48]) and Maximum posterior elevation (31.05 ± 19.36 µm [range; 5 - 93]). Regarding refractive status, mean spherical refraction was: -1.87 ± 3.69 [range: 10.25 to −17.00 D], mean cylindrical refraction was: -2.85 ± 1.9 [range: 0.00 to −10.00] and mean SE refraction was: -3.30 ± 3.98 [range: 8.75 to −20.50 D]. The mean values of the measured UDVA (log Mar) for 149 eyes was 0.5 ± 0.4 [range: 0 to 1.30] and of BCVA (log Mar) with spectacles was 0.14 ± 0.19 [range: 0 to 1.00]. In terms of KCN grading moderate grade was the most common (43.1%) followed by mild grade (45.1%) as for severe grade it accounted for (11.0%) in total. Compound myopic astigmatism (57.2%) constituted the majority of cases followed by Simple myopic astigmatism (23.1%) and Mixed astigmatism (9.9%). Correlation between absolute value of SE and Kmax (r = 0.669, P-value = 0.000) and with TL (r = -0.393, P-value = 0.000)
Conclusion:
The clinical profile of keratoconus in Syrian patients is comparable to other studies worldwide with it being more frequent in females and having Compound myopic astigmatism being the most common refractive error related to eyes with keratoconus.
