Utility of the Actiwatch Spectrum Plus for detecting the outdoor environment and physical activity in children

PURPOSE

To describe the performance of the Actiwatch Spectrum Plus (Philips, Respironics) for determining real world indoor and outdoor environments and physical activity in children.

METHODS

Children wore the device while performing 10 different activities, ranging from sedentary to vigorous physical-activity, and under different indoor and outdoor conditions. Repeated measures ANOVA was implemented via mixed effects modeling to determine illuminance (lux) and physical activity (counts per 15 s, CP15) across conditions. Receiver operator characteristics (ROC) analysis assessed the accuracy to detect indoor versus outdoor settings.

RESULTS

Illuminance was found to be statistically different across indoor (793 ± 348 lux) and outdoor (4,413 ± 518 lux) conditions (P<.0001), with excellent diagnostic accuracy to detect indoor versus outdoor settings (Area under the ROC Curve, AUC 0.94); 1088 lux was identified as the optimal threshold for outdoor illuminance (sensitivity: 93.0%; specificity: 85.0%). Using published activity ranges, we found that when children were sitting, 94% of the physical-activity readings were classified as sedentary or light. When children were walking, 88% of readings were classified as light, and when children were running, 77% of readings were classified as moderate or vigorous.

CONCLUSION

The Actiwatch Spectrum Plus performed well during real world activities in children, showing excellent diagnostic accuracy at 1088 lux as a threshold to detect indoor versus outdoor environments and in categorizing physical activity.

Baseline characteristics in the Israel refraction, environment, and devices (iREAD) study

The purpose of this study is to present baseline data from a longitudinal study assessing behavioral factors in three groups of boys in Israel with varying myopia prevalence. Ultra-Orthodox (N = 57), religious (N = 67), and secular (N = 44) Jewish boys (age 8.6 ± 1.4 years) underwent cycloplegic autorefraction and axial-length measurement. Time-outdoors and physical-activity were assessed objectively using an Actiwatch. Ocular history, educational factors, and near-work were assessed with a questionnaire. Group effects were tested and mixed effects logistic and linear regression were used to evaluate behaviors and their relationship to myopia. The prevalence of myopia (≤ - 0.50D) varied by group (ultra-Orthodox: 46%, religious: 25%, secular: 20%, P < 0.021). Refraction was more myopic in the ultra-Orthodox group (P = 0.001). Ultra-Orthodox boys learned to read at a younger age (P < 0.001), spent more hours in school (P < 0.001), spent less time using electronic devices (P < 0.001), and on weekdays, spent less time outdoors (P = 0.02). Increased hours in school (OR 1.70) and near-work (OR 1.22), increased the odds of myopia. Being ultra-Orthodox (P < 0.05) and increased near-work (P = 0.007) were associated with a more negative refraction. Several factors were associated with the prevalence and degree of myopia in young boys in Israel, including being ultra-Orthodox, learning to read at a younger age, and spending more hours in school.

Objective quantification of viewing behaviours during printed and electronic tasks in emmetropic and myopic ultra-Orthodox Jewish men

PURPOSE

Ultra-Orthodox Jewish men are known to have a high prevalence of myopia, which may be due to intense near-work from an early age. This study objectively assessed near-viewing behaviours in ultra-Orthodox and non-ultra-Orthodox men in Israel for different tasks.

METHODS

Ultra-Orthodox (n = 30) and non-ultra-Orthodox (n = 38) men aged 18-33 years participated. Autorefraction, visual acuity, height and Harmon distance were measured. An objective range-finding sensor was mounted on their spectacles while they performed four 10-min tasks in a randomised order: (1) reading printed material, (2) writing printed material, (3) passive electronic and (4) active electronic tasks. Near-viewing distance and the number of viewing breaks were calculated for each task. Statistical analyses included Student t-tests and the Mann-Whitney test between groups and repeated measures ANOVA or Friedman between tasks.

RESULTS

For all tasks combined, a significantly shorter viewing distance was observed for the ultra-Orthodox group (36.2 ± 7.0 cm) than for the non-ultra-Orthodox group (39.6 ± 6.7 cm, p < 0.05). Viewing distances for the passive reading and electronic tasks were shorter for the ultra-Orthodox group (36.9 ± 7.7 cm vs. 41.3 ± 8.1 cm, p < 0.03 and 39.0 ± 10.1 vs. 43.9 ± 9.3, p < 0.05, respectively). Viewing distances were significantly different between all four tasks, with writing having the closest distance. No correlation was found between working distance and spherical equivalent or Harmon distance. However, a significant correlation was found in the ultra-Orthodox group between working distance and height for each task (p < 0.04, R < 0.42 for all). There was no difference in the number of viewing breaks between the groups.

CONCLUSION

When reading a book and viewing an iPad, ultra-Orthodox men demonstrated a closer objective working distance than non-ultra-Orthodox men. This shorter viewing distance may contribute to the high prevalence and degree of myopia in this population.

Revisiting the oil droplet sign in keratoconus: Utility for early keratoconus diagnosis and screening

PURPOSE

An annular dark shadow (ADS) reflex has been observed while performing direct ophthalmoscopy on subjects with keratoconus. This study describes a method that may serve as a diagnostic technique for early keratoconus and may be used as a quantitative measure of severity.

METHODS

Healthy keratoconic subjects and keratoconus suspects underwent corneal tomography and a full ocular examination. Keratoconus severity was graded based on Belin ABCD criteria. An iPhone camera was connected to a direct ophthalmoscope to take a picture of the eye. The height of the ASD was measured using the AutoCAD software. Differences between subject groups were evaluated by chi-squared and Mann-Whitney tests. Spearman correlation compared ocular parameters and the height of the ADS. A multiple stepwise linear regression was used to predict the height of the ADS based on clinical parameters.

RESULTS

Fifty-eight subjects participated in this study: 37 healthy controls (37 eyes) and 21 keratoconics or keratoconus suspects (37 eyes). The ADS was present in all keratoconic and keratoconus-suspect eyes but in none of the controls. The height of the ADS was significantly correlated with keratoconus severity. Front corneal surface root mean square of higher order aberrations, sphere and anterior radius of curvature from the front apex curve are significant predictors of the height of the ADS.

CONCLUSIONS AND RELEVANCE

The ADS may be a useful method to diagnose keratoconus and keratoconus-suspect cases and serve as a grading and follow-up method for tracking disease severity.

The prevalence of refractive errors in college students in Israel

PURPOSE

To determine the prevalence of refractive errors in Jewish and Arab college students in Israel and associations with ethnicity and sex.

METHODS

In this retrospective cross-sectional study, first-year college students underwent non-cycloplegic autorefraction and answered a questionnaire to assess age, sex, and self-identified ethnicity. Spherical equivalent refractive error (SER) was calculated, and the prevalence of hyperopia (>+0.50 Diopter, D), emmetropia (>-0.50 to +0.50 D), myopia (≤-0.50D, low ≤-0.50 to >-3.0D, moderate <-3.0 to >-6.0D, high ≤-6.0D), and astigmatism (>0.50D) were determined. Groups were compared using Chi-square or Fisher test. Univariate and multivariate analyses were conducted to identify factors associated with refractive errors.

RESULTS

Participants (n = 807) had a mean age of 22.1 ± 2.6 years (range: 17-30 years) and SER of -1.7 ± 2.2D (range: -13.3 to +5.7D). The prevalence and 95% confidence internal of myopia was 66.3% (63.0-69.6). Jewish students had a higher prevalence than Arab students for myopia (69.2% vs 60.3%), moderate (18.5% vs 12.2%) and high myopia (5.9% vs 1.9%) and astigmatism (51.4% vs 43.9%, p<0.05 for all), but not low myopia or hyperopia. Females had a higher prevalence of myopia than males (68.1% vs 58.7%, p<0.03). Jewish ethnicity was associated with myopia (OR=1.48, p = 0.01) and moderate myopia (OR=1.72, p = 0.01), and studying optometry was associated with moderate myopia (OR=1.63, p = 0.02). Sex and age were not associated with myopia.

CONCLUSION

Myopia prevalence in Israeli college students is high, showing associations with Jewish, but not Arab, ethnicity, suggesting that ethnic factors may play a role in the refractive differences between Arabs and Jews.

Agreement and inter-session repeatability of manual and automatic interpupillary distance measurements

BACKGROUND

Interpupillary distance (IPD) is important in developmental anatomy, genetics, design of optical instrumentation, ocular diagnostics, and optical prescribing. IPD frequently is measured on different days, and by either automatic pupillometers (physiological measurement) or manual ruler (anatomical measurement). Therefore, there is importance in the agreement and inter-session repeatability of manual and automatic IPD measurements.

METHODS

Monocular distance from the bridge of the nose and binocular distance and near binocular IPD were randomly measured, using a millimeter ruler and the Essilor Pupillon pupillometer. Gender effects were assessed using Wilcoxon and Mann-Whitney tests, respectively. Agreement was assessed using Spearman correlation and Bland-Altman (B&A) plots. Thirty additional participants were tested within 1-2 weeks to determine the inter-session repeatability.

RESULTS

The agreement study included 199 participants (mean age: 24.1 ± 5.0 range: 19-53, 58 male, 141 female) and the repeatability sub- study included 30 (mean age: 27.9 ± 4.5, range: 23-39, 6 male, 24 female). Males and females significantly differed in age (<2 year mean difference (md)) and IPD (monocular md: < 1 mm, binocular md: < 2 mm). Manual vs. automatic measurements were significantly different for all conditions (md: <1 mm for all) except for distance left eye male PD. There was no significant difference between the session for both methods.

CONCLUSIONS

Binocular and monocular manual and automatic measurements were significantly different statistically, but not clinically. Distance binocular IPD was approximately 3 mm wider than near IPD. Male binocular IPD was approximately 2 mm wider than the female IPD. Both methods had good inter-session repeatability.

Objective Behavioral Measures in Children before, during, and after the COVID-19 Lockdown in Israel

Studies using questionnaires report that COVID-19 restrictions resulted in children spending significantly less time outdoors. This study used objective measures to assess the impact of pandemic-related restrictions on children’s behavior. A total of 19 healthy 8–12-year-old boys were observed before and during social restriction periods. Of these, 11 boys were reassessed after restrictions were lifted. For each session, Actiwatches were dispensed for measures of time outdoors, activity, and sleep. Changes overall and by school status were assessed using signed-rank test and Wilcoxon rank sum tests. During restrictions, children spent significantly less time outdoors (p = 0.001), were less active (p = 0.001), and spent less time engaged in moderate-to-vigorous physical activity (p = 0.004). Sleep duration was not significantly different between sessions (p > 0.99), but bedtime and wake time shifted to a later time during restrictions (p < 0.05 for both). Time outdoors and activity returned close to pre-pandemic levels after restrictions were lifted (p > 0.05 for both). Children’s behaviors significantly changed during the COVID-19 pandemic. The reduction in outdoor light exposure is of importance due to the role of light in the etiology of myopia and vitamin D production. The reduction in physical activity may have negative health effects in terms of obesity and depression, although further research is required to ascertain the long-term effects.

Environmental and Behavioral Factors with Refractive Error in Israeli Boys

SIGNIFICANCE

Evidence supporting the contributions of near work in myopia is equivocal. Findings from this pilot study suggest that a high prevalence of myopia in ultra-Orthodox boys may be attributed to intense near work at school and learning to read in preschool at an early age.

PURPOSE

This study aimed to assess factors that may influence myopia in three groups of Jewish boys with different educational demands.

METHODS

Healthy ultra-Orthodox, religious, and secular Jewish boys (n = 36) aged 8 to 12 years participated. Refractive status, education, time spent reading and writing, and electronic device use were assessed using a questionnaire, and time outdoors and physical activity were assessed objectively using an Actiwatch. Data were analyzed with χ2 and Kruskal-Wallis tests with Bonferroni post hoc comparisons.

RESULTS

Ultra-Orthodox (n = 14) and religious (n = 13) children had greater myopia prevalence compared with secular children (n = 9; P = .01), despite no differences in parental myopia. Actigraph data showed that there were no differences in activity (P = .52) or time spent outdoors (P = .48) between groups. Ultra-Orthodox children learned to read at a younger age and spent more hours at school (P < .001 for both). All groups engaged in a similar amount of near work while not in school (P = .52). However, ultra-Orthodox boys had less electronic device use than did religious (P = .007) and secular children (P < .001).

CONCLUSIONS

This pilot study demonstrates that ultra-Orthodox, religious, and secular children have distinct educational demands but similar time outdoors, physical activity, and near work while not in school. The findings suggest that near work at school and/or learning to read in preschool at an early age may contribute to previously reported differences in refractive error between groups. However, conclusions should be confirmed in a larger sample size.

Contrast sensitivity and higher-order aberrations in Keratoconus subjects

This study analyzes the relationship between contrast-sensitivity and higher-order aberrations (HOA) in mild and subclinical-keratoconus in subjects with good visual-acuity (VA). Keratoconus group (including subclinical-keratoconus) and controls underwent autokeratometry, corneal-tomography, autorefraction and HOA measurement. Contrast-sensitivity was tested using a psychophysical two-alternative forced-choice Gabor patches in three blocks (6, 9, 12 cycles/deg). Controls were compared to the keratoconus group and to a keratoconus subgroup with VA of 0.00 LogMar group ("keratoconus-0.00VA"). Spearman correlation tested association between HOA and contrast-sensitivity. Twenty-two keratoconus subjects (38 eyes: 28 keratoconus, 10 subclinical-keratoconus, 20 keratoconus-0.00VA) and 35 controls were included. There was a significant difference between control and keratoconus, and between control and keratoconus-0.00VA, for keratometry, cylinder, thinnest and central corneal thickness (p < 0.001). Controls showed lower HOA and higher contrast-sensitivity for all spatial-frequencies (p < 0.001). Most HOA were negatively correlated with contrast-sensitivity for all spatial-frequencies for keratoconus group and for 9 and 12 cycles/deg for keratoconus-0.00VA. Keratoconus subjects with good VA showed reduction in contrast-sensitivity and increased HOAs compared to controls. HOA and contrast-sensitivity are inversely correlated in subjects with mild keratoconus despite good VA. This suggests that the main mechanism underlying the decreased vision quality in keratoconus is the increase of HOA.

The prevalence of corneal abnormalities in first-degree relatives of patients with keratoconus: a prospective case-control study

PURPOSE

Although there is a high prevalence of keratoconus in the Middle East including Israel, limited data is available describing first-degree relatives of patients with sporadic keratoconus (KC) using Scheimpflug imaging. The purpose of this study is to accurately phenotype first-degree relatives of patients with sporadic KC in Israel using corneal tomography, which may help determine the genetic aetiology of KC.

METHODS

First-degree relatives (N = 56) of 16 KC probands participated in this prospective case-control study. Healthy controls (N = 96) were from a previous study. Autorefraction, visual acuity, slit lamp biomicroscopy, retinoscopy, subjective refraction and Scheimpflug imaging (CSO Sirius Topographer) of keratoconus patients and their first-degree relatives were evaluated. The worse eye was used for KC and KC suspects. The main outcome measure was prevalence of abnormal corneal topography and tomography parameters, which was compared between first-degree relatives vs controls. p values < 0.05 were considered significant.

RESULTS

KC (N = 2) or KC suspect (N = 8) was diagnosed in 18% (95% CI 8-28%) of the first-degree relatives. At least one abnormal corneal parameter was evident in 34% of first-degree relatives, while this was significantly lower for controls (14%, χ2(1,N = 152)  = 8.8, p = 0.01). Qualitative analysis showed KC first-degree relatives had significantly more abnormal anterior corneal topography patterns than controls (34% vs 17%, χ2(1,N = 152)  = 5.9, p = 0.02). For first-degree relatives, sex was not a factor influencing prevalence of corneal abnormalities (18% for both men and women, χ2(1,N = 56)  = 0.0, p = 1.0). A significant correlation was found for first-degree relatives between age and most corneal parameters, while this was not evident for the control group.

CONCLUSIONS AND RELEVANCE

Eye care practitioners should consider first-degree relatives of patients with KC at moderate risk for the disease and/or corneal abnormalities.

The epidemiology and treatment of conjunctivitis at Urgent Care Centres in Israel

Purpose: Conjunctivitis is the most common ocular condition diagnosed at emergency departments (ED) in the USA, although it is generally not an emergent condition. Treatment of conjunctivitis at Urgent Care Centres (UCC) could offer lower cost than ED. This study describes the demographics and outcomes of a cohort presenting with conjunctivitis to a nationwide UCC system.

Methods: This retrospective study included 17 branches of UCC. Electronic Medical Record data (November 2015–October 2016) of patients diagnosed with conjunctivitis or ocular disorder were retrieved. Data included gender, age, diagnosis, treatment, discharge status and temperature. Patients without conjunctivitis, presenting to UCC during this period served as the control. Results were compared to all ED patients in Israel (from a public report). Descriptive statistics, Chi-square and Z-proportion test were used.

Results: Altogether, 602,074 patients presented to UCC, of which 5,045 (0.84%, 95% CI 0.74–0.94%) were diagnosed with conjunctivitis. Conjunctivitis was more prevalent among young males (0–14, p<0.001) and older females. The conjunctivitis cohort at UCC was significantly younger than the ED cohort (p<0.01). UCC treated and released home 96.7% (95% CI 96.2–97.2%) of cases. This is significantly higher than the treatment rate for the entire UCC cohort (93.2%, CI 93.2–93.3%, p<0.05). Treatment in most cases (82.0%, 95% CI 80.9–83.0%) involved the prescription of ocular antibiotic.

Conclusion: Similar to previous studies at ED, conjunctivitis patients are primarily young males. Most patients were treated with antibiotics at UCC and released home. This suggests that UCC may be a good venue for treatment of conjunctivitis.

Corneal and conjunctival injury seen in urgent care centres in Israel

PURPOSE

Corneal and conjunctival injuries (CCI) comprise a large portion of the cases presenting to hospital-based emergency departments (ED) with ocular involvement. Urgent Care Centres (UCC) offer community based emergency care at lower cost than hospital-based emergency departments (ED) and with greater temporal convenience than primary care office settings. While CCI prevalence and treatment at hospital-based EDs has been well studied, this is the first report, to our knowledge, on CCI demographics and aetiology presenting to UCCs.

METHODS

This retrospective study was approved by the institutional ethics committee. The setting is a UCC system in Israel, modelled on USA urgent care facilities, consisting of 17 branches at the time of the study. Electronic medical record data (between November 1, 2015 and October 31, 2016) of patients diagnosed with corneal disorder, foreign body or eye disorder were retrieved and reviewed for inclusion/exclusion criteria. Data collected included gender, age, chief complaint, diagnosis, treatment and discharge status (sent home or referred to ED). International Classification of Diseases, Ninth Revision (ICD-9) codes were assigned to each record based on a review of all fields. UCC results were compared to all ED patients in Israel using data from a public report. Data were analysed by descriptive statistics and logistic regression analysis.

RESULTS

Of the 602 074 charts screened, 4797 patients presented with CCI (0.8%). The average age was 32.6 ± 18.2 years and 71.3% were male. Among these, 26.4% were referred to the ED compared to 6.8% from the entire UCC cohort. ICD-9 code Foreign body (FB) of the eye was the most common cause of CCI (56.5%) followed by the following ICD-9 codes: trauma (18.1%), chemical in the eye (11.1%) and corneal disorder due to a contact lens (5.1%). Logistic regression analyses showed the following risk factors for ED referral: age (22-64), male gender, ICD-9 code FB, work-related injury and the presence of a clinical abrasion in the eye.

CONCLUSIONS

The aetiology of ocular injury at UCC is similar to previous studies of ED. Most CCI can be treated at UCC saving ED resources and underscores the importance of this mode of health care delivery in the overall health system.

Validation of refraction and anterior segment parameters by a new multi-diagnostic platform (VX120)

BACKGROUND

The VX120 (Visionix Luneau, France) is a novel multi-diagnostic platform that combines Hartmann-Shack based autorefraction, Placido-disk based corneal-topography and anterior segment measurements made with a stationary-Scheimpflug camera. We investigate the agreement between different parameters measured by the VX120 with accepted or gold-standard techniques to test if they are interchangeable, as well as to evaluate the repeatability and reproducibility.

METHODS

The right-eyes of healthy subjects were included in the study. Autorefraction of the VX120 was compared to subjective refraction. Agreement of anterior segment parameters was compared to the Sirius (CSO, Italy) including autokeratometry, central corneal thickness (CCT), iridiocorneal angle (IA). Inter and intra-test repeatability of the above parameters was assessed. Results were analyzed using Bland and Altman analyses.

RESULTS

A total of 164 eyes were evaluated. The mean difference between VX120 autorefraction and subjective refraction for sphere, spherical equivalent (SE), and cylinder was 0.01±0.43D, 0.14±0.47D, and -0.26±0.30D, respectively and high correlation was found to all parameter (r>0.75) except for J₄₅ (r=0.61). The mean difference between VX120 and the Sirius system for CCT, IA, and keratometry (k1 and k2) was -3.51±8.64μm, 7.6±4.2°, 0.003±0.06mm and 0.004±0.04mm, respectively and high correlation was found to all parameter (r>0.97) except for IA (r=0.67). Intrasession repeatability of VX120 refraction, CCT, IA and keratometry yielded low within-subject standard deviations. Inter-session repeatability showed no statistically significant difference for most of the parameters measured.

CONCLUSIONS

The VX120 provides consistent refraction and most anterior segment measurements in normal healthy eyes, with high levels of intra and inter-session repeatability.

A survey of the criteria for prescribing in cases of borderline refractive errors

PURPOSE

This research investigated the reported optometric prescribing criteria of Israeli optometrists.

METHODS

An online questionnaire based on previous studies was distributed via email and social networking sites to optometrists in Israel. The questionnaire surveyed the level of refractive error at which respondents would prescribe for different types of refractive error at various ages with and without symptoms.

RESULTS

124 responses were obtained, yielding a response rate of approximately 12-22%, 92% of whom had trained in Israel. For all refractive errors, the presence of symptoms strongly influenced prescribing criteria. For example, for 10-20 year old patients the degree of hyperopia for which 50% of practitioners would prescribe is +0.75 D in the presence of symptoms but twice this value (+1.50 D) in the absence of symptoms. As might be expected, optometrists prescribed at lower degrees of hyperopia for older compared with younger patients. There was a trend for more experienced practitioners to be less likely to prescribe for lower degrees of myopia and presbyopia. Practitioner gender, country of training, the type of practice environment, and financial incentives were not strongly related to prescribing criteria.

CONCLUSIONS

The prescribing criteria found in this study are broadly comparable with those in previous studies and with published prescribing guidelines. Subtle indications suggest that optometrists may become more conservative in their prescribing criteria with experience.

Prevalence of Keratoconus among Young Arab students in Israel

Purpose

To determine the prevalence of keratoconus (KC) in an Arab population in Israel.

Materials and methods

Videokeratography was performed on volunteer students from the Academic Arab College of Education, in Haifa, Israel. All participants filled out a self-administered questionnaire to evaluate possible risk factors for KC. Univariate and multivariate analysis were performed.

Results

Data of 314 participants were analyzed and a prevalence of (N = 10), 3.18% (95% CI, 1.2 to 5.1%) was found. The only significant factor (both in univariate and multivariate analysis) that was associated with KC was parental consanguinity (OR 5.10, p = 0.02). Druzes and Bedouins had a higher prevalence than Muslims and Christians. However, the differences were not significant possibly due to the small size of the sample.

Conclusion

The result of this study was similar to other studies conducted in the Middle East, which indicate a higher prevalence of KC than in western countries. It is also recommended that people who have consanguinity in their family should be topographically tested to detect the early stages of KC.

How to cite this article

Shneor E, Millodot M, Gordon-Shaag A, Essa M, Anton M, Barbara R, Barbara A. Prevalence of Keratoconus among Young Arab Students in Israel. Int J Kerat Ect Cor Dis 2014;3(1):9-14.

Characteristics of 244 patients with keratoconus seen in an optometric contact lens practice

BACKGROUND

The purpose of this study was to describe the characteristics of keratoconic patients seen in a specialised contact lens practice from a general population with a high prevalence of the disease.

METHODS

Patients attending a contact lens practice for management of keratoconus were asked to complete a questionnaire. Data were collected on demographic characteristics, general health, family history, eye rubbing, allergy, asthma, eczema, education level, history of keratoplasty and smoking.

RESULTS

Two hundred and forty-four patients completed the questionnaire. There was a male bias (54.5 per cent). The majority of the patients (78.7 per cent) wore contact lenses, of whom 67.7 per cent wore hard, 13 per cent soft and 4.2 per cent scleral contact lenses. Some of the patients (21.3 per cent) had undergone corneal graft surgery. Eighteen per cent had an associated systemic disease, the most common of which was type 2 diabetes, although this disease was less prevalent, but not significantly, in the keratoconic sample than in the general population (p = 0.19). The prevalence of eye rubbing (65.6 per cent) was similar to other studies. Compared to the general population, asthma (13.2 per cent) was slightly, but not significantly, less prevalent (p = 0.17), eczema (6.6 per cent) was significantly less (p < 0.001) and allergy (34.4 per cent) was more prevalent (p < 0.001). A high proportion of patients reported a family history of the disease (27.9 per cent) and most were better educated than the general population.

CONCLUSION

The results of this survey concur with those of other studies with regard to most known characteristics of keratoconus; however, the proportion of asthma and eczema tended to be less than in other surveys and may be linked to the environmental influence of a hot and sunny country. The high prevalence of positive family history of the disease in this cohort suggests a genetic influence.

Bilateral chorioretinal coloboma discovered with ultra-wide field retinal imaging

Uveal coloboma results from incomplete closure of the optic cup fissure. While conducting an evaluation of a new ultra-wide field retinal imaging camera (Optomap), which provides a view of the fundus up to 200° at one time without mydriasis, we discovered a case of bilateral chorioretinal coloboma in a 21-year-old student. The lesion was located in the midperiphery of each eye less than 2 disc diameters (DD) below the optic disc in the inferonasal quadrants. The size of the coloboma in the right eye was 1.8 DD in height and 1.3 DD in width, while the left lesion was 2.4 DD in height and 2.6 DD in width. The subject was totally asymptomatic and without any complication such as retinal detachment or choroidal neovascularization, which often accompany this type of lesion. The visual field of each eye displayed an absolute scotoma corresponding to the size and location of the coloboma. No management was necessary but the subject was advised to report for visual examination at regular intervals because complications can occur at any age.

Validation of keratometric measurements obtained with a new integrated aberrometry-topography system

Purpose

A clinical evaluation of the L80 videokeratographer (Visionix Luneau, Chartres, France) was performed to assess its validity and repeatability compared with a traditional Bausch and Lomb (B & L) keratometer.

Methods

87 right eyes of 87 subjects, (mean age 23.72 ± 3.62 years old, 70 women and 17 men), participated in this study. Corneal curvature was measured using the L80 instrument by one practitioner and the manual B & L keratometer by a different practitioner. Intratest and intertest repeatability were assessed.

Results

Corneal curvature was found to be statistically different between the two instruments (p < 0.001), with the L80 providing a slightly steeper bias of 0.05 mm and 0.07 mm for the horizontal and vertical meridians, respectively than the B & L keratometer. 78.2% and 86.2% of the L80 results were within ±0.1 mm (±0.06 D) and 95.4% and 97.7% within ±0.2 mm (±0.11 D) of the readings obtained with the B & L keratometer along the horizontal and the vertical meridians, respectively. The agreement between the L80 and B & L keratometers axes was 31.0% within ±5°, 54.0% within ±10°, 60.9% within ±15°, 71.3% within ±20° and 87.4% within ±40°. Intratest repeatability was the same for both instruments. Intertest repeatability was better for the L80 videokeratographer compared to the B & L keratometer and showed no significant difference between the two sessions.

Conclusion

The L80 videokeratographer is a reliable objective instrument comparable to other autokeratometers which, in addition, combines many other useful clinical features. It provides steeper radii of curvature measurements than the B & L keratometer. An offset incorporated into the instrument could mitigate the difference between the two instruments and make them interchangeable.

The Epidemiology and Etiology of Keratoconus

Keratoconus is a noninflammatory disorder characterized by ectasia of the central or inferior portion of the cornea. This review presents the scant epidemiological information known to date and the factors believed to cause the development of the disease. They are the genetic factors for which evidence come from family studies, twin studies and genetic loci. There appears to be multiple genes causing a keratoconus phenotype with variable penetration. However, the genetic predisposition might not be enough; environmental factors, such as eye rubbing, atopy and UV exposure, may have a role in generating the disease.

How to cite this article

Gordon-Shaag A, Millodot M, Shneor E. The Epidemiology and Etiology of Keratoconus. Int J Keratoco Ectatic Corneal Dis 2012;1(1):7-15.

Eye dominance effects in conjunction search

We previously found a dominant eye perceptional advantage in feature search (Vision Research, 2006). We now ask if this advantage extends to difficult conjunction search, which requires focused attention and depends on different cortical hierarchy levels. We determined eye dominance by the Hole-in-the-Card test. Using red-green glasses, subjects viewed a briefly presented, backward-masked, array of red/green dotted squares and filled circles. On half of the trials a filled square target replaced one dotted square. There was significantly better performance when the target was seen by the dominant eye, suggesting its visual processing priority in slow, as in rapid search, perhaps including augmented attention to dominant eye representations. Binocular conjunction targets were found faster than monocular targets, though binocularity--as utrocular information--was insufficient to support reasonable detection levels.

Eye dominance effects in feature search

We studied the role of eye dominance in non-rivalry conditions, testing dichoptic visual search and comparing performance with target presented to the dominant or non-dominant eye. Using red-green glasses, subjects viewed an array of green and red lines of uniform orientation, with a differently oriented target line present on half the trials. Performance was significantly better when the dominant eye saw the target, especially when the opposite eye saw the distractors. This effect was reduced when only nearest-neighbor surrounding distractors were homogeneous. We conclude that the dominant eye has priority in visual processing, perhaps including inhibition of non-dominant eye representations.