Results of photorefractometric screening for amblyogenic defects in children aged 20 months

Pre-Cycloplegic Exam Benefit of Photoscreening and Accommodation-Relaxing Skiascopy

Background

Seeking a quick way to estimate refractions for challenging pediatric patients, we studied two non-contact methods with particular attention to accuracy and level of stress in uncovering cycloplegic hyperopia.

Methods

Newly referred and follow-up pediatric eye patients had timed school bus accommodation-relaxing skiascopy (SBARS) and Plusoptix A12 (Px) photoscreener testing before cyclopentolate 1% confirmatory examinations. The ABCD ellipsoid univariate method based on relative blur and vector components was used to compare dry sphero-cylinder refraction estimates with cycloplegic. Receiver operating characteristic (ROC) curves were used to determine screening value.

Results

Three compared refractions were attempted in 191 racially diverse children of whom 100 were age 0.2-3.9 years and 91 were 4 to 14 years. Plusoptix failed to yield a result in 21 and an additional 21 were interpreted as an excess sphere. Median spherical equivalent did not differ between Px and SBARS for 149 with Px readings but in hyperopic patients, Plusoptix uncovered 27% less hyperopia. The ellipsoid for SBARS of 0.8 was better than 2.4 for Plusoptix (Mann-Whitney p<0.001). Plusoptix was fastest (3-15 seconds) followed by SBARS (15-30 seconds) compared to 30-45 minutes for cycloplegic exam.

Conclusion

Non-contact quick refractive methods enhanced confirmatory cycloplegic pediatric exam in high-risk pediatric patients.

Multifaceted Amblyopia Screening with blinq, 2WIN, and PDI Check

BACKGROUND

Novel devices target different facets of amblyopia risk factors (ARFs). Through birefringence, the Rebion blinq assesses binocular foveation. The Adaptica 2WIN is a multiradial infrared photorefractor that also estimates ocular alignment. PDI Check is a forced-choice, dynamic near-vision game for the autostereoscopic Nintendo 3DS.

METHODS

New and returning patients to a pediatric ophthalmology clinic had concomitant confirmatory exams after all three vision screens had been validated with ROC curves, Bland-Altman plots, and Alaska Blind Child Discovery ellipsoid grades. Exam outcomes were classified by ARF visual acuity, strabismus, binocularity, and refractive errors following the 2021 AAPOS guidelines and Bosque-Hunter rubric for the blinq.

RESULTS

A total of 202 ethnically diverse students aged 10±4 (4-19) years, 33% treatment-naïve, had a high (58%) prevalence of ARFs. Linear logMAR visual acuity, intereye differences, stereo and three-cone color correlated well between PDI Check and exams. Mean score on the 2WIN matched sphero-cylinder exam with ellipsoid scoring was 2.1±1.5. For AAPOS 2021 refractive plus strabismus, sensitivity/specificity for PDI Check was 68%/59%, 2WIN 72%/95%, and blinq 87%/32%. For the amblyopia or strabismus rubric, PDI Check was 79%/68%, 2WIN 56%/65%, and blinq 94%/37%.

CONCLUSION

Each device had advantages and disadvantages in screening this cohort of older, high-prevalence students, many of whom had already been treated. Validation methods should cover more than just refraction, as the new 2021 AAPOS guidelines do.

Part-time vs. full-time occlusion for amblyopia: evidence for part-time patching

Amblyopia is characterized by a decreased uncorrectable visual acuity in a structurally normal eye. Occlusion therapy has been used for years to improve acuity, and, traditionally, practitioners have utilized full-time patching. This article will explore more recent research looking at using part-time patching in the treatment of amblyopia.

Original papers: Prevalence of amblyogenic diseases in a preschool population sample of Valladolid, Spain

OBJECTIVES

Amblyopia is the leading cause of monocular vision loss in people under 40 years, and especially in children. The purpose of the present investigation is to determine the prevalence of amblyopia and ocular pathology, specially the most common causes of amblyopia, in a population of 3-to 6-year-old children.

PATIENTS AND METHODS

From a total of 8167 children, a geographically defined population of 3-to 6-year-old children, 2000 were randomly selected, and 1179 (58.9%) examined. Ophthalmologic examination included: Personal and familial history, visual acuity, extraocular motility, cover test at near distance, cycloplegic refraction with autorefractometer and fundus eye examination. Amblyopia was considered when corrected visual acuity was < 0.5 with Marquez optotypes and difference in visual acuity of 0.2 or more between eyes. Pathology considered as amblyogenic were strabismus, visual acuity asymmetry and anisometropia.

RESULTS

The family history showed amblyopia in 249 (21.1%), strabismus in 227 (19.2%), and refractive errors in 808 (65.5%). Cover test was positive in 78 children (6.7%). A visual acuity difference of 0.2 or more between eyes was present in 88 (7.5%) children, and anisometropia over 1.5 diopters (in spherical equivalent) was present in 17 (1.4%) subjects. One hundred and twenty-two (10.35%) children did not achieve a normal visual acuity: visual acuity in the better eye was less than 0.5 in 55 children under 5 years and less than 0.6 in 67 children over 5 years. The prevalence of amblyopia was 7.5%.

CONCLUSIONS

The data support the importance of early detection and treatment of amblyopia and the need for visual screening at an early age.

Noncycloplegic Photorefractive Screening in Pre-School Children with the “PowerRefractor” in a Pediatric Practice

PURPOSE

To provide a framework for typical refractive development, as measured without cycloplegia with a commercial infrared photorefractor. To evaluate the usefulness of the screening for refractive errors, we retrospectively analyzed the data of a large number of unselected children of different ages in a pediatric practice in Tuebingen, Germany.

METHODS

During the standard regular preventive examinations that are performed in 80% to 90% of the young children in Germany by a pediatrician (the German "U1 to U9" system), 736 children were also measured with the first generation PowerRefractor (made by MCS, Reutlingen, Germany, but no longer available in this version). Of those, 172 were also measured with +3 D spectacles to find out whether this helps detect hyperopia. Children with more than +2 D of hyperopia or astigmatism, more than 1.5 D of anisometropia, or more than 1 D of myopia in the second year of life were referred to an eye care specialist. The actions taken by the eye care specialist were used to evaluate the merits of the screening.

RESULTS

The average noncycloplegic spherical refractive errors in the right eyes declined linearly from +0.93 to +0.62 D over the first 6 years (p < 0.001)-between 1.5 and 0.5 D less hyperopic than in published studies with cycloplegic retinoscopy. As expected, +3 D spectacle lenses moved the refractions into the myopic direction, but this shift was not smaller in hyperopic children. The average negative cylinder magnitudes declined from -0.89 to 0.48 D (linear regression: p < 0.001). The J0 components displayed high correlations in both eyes (p < 0.001) but the J45 components did not. The average absolute anisometropias (difference of spheres) declined from 0.37 to 0.23 (linear regression: p < 0.001). Of the 736 children, 85 (11.5%) were referred to an eye care specialist. Of these, 52 received spectacles (61.2%), 14 (16.4%) were identified as "at risk" and remained under observation, and 18 (21.2%) were considered "false-positive."

CONCLUSIONS

Non cycloplegic photorefraction provides considerably less hyperopic readings than retinoscopy under cycloplegia. Additional refractions performed through binocular +3-D lenses did not facilitate detection of hyperopia. With the referral criteria above, 11% of the children were referred to an eye care specialist, but with a 20% false-positive rate. The screening had some power to identify children at risk but the number of false-negatives remained uncertain.

Amblyopia characterization, treatment, and prophylaxis

Amblyopia has a 1.6-3.6% prevalence, higher in the medically underserved. It is more complex than simply visual acuity loss and the better eye has sub-clinical deficits. Functional limitations appear more extensive and loss of vision in the better eye of amblyopes more prevalent than previously thought. Amblyopia screening and treatment are efficacious, but cost-effectiveness concerns remain. Refractive correction alone may successfully treat anisometropic amblyopia and it, minimal occlusion, and/or catecholamine treatment can provide initial vision improvement that may improve compliance with subsequent long-duration treatment. Atropine penalization appears as effective as occlusion for moderate amblyopia, with limited-day penalization as effective as full-time. Cytidin-5'-diphosphocholine may hold promise as a medical treatment. Interpretation of much of the amblyopia literature is made difficult by: inaccurate visual acuity measurement at initial visit, lack of adequate refractive correction prior to and during treatment, and lack of long-term follow-up results. Successful treatment can be achieved in at most 63-83% of patients. Treatment outcome is a function of initial visual acuity and type of amblyopia, and a reciprocal product of treatment efficacy, duration, and compliance. Age at treatment onset is not predictive of outcome in many studies but detection under versus over 2-3 years of age may be. Multiple screenings prior to that age, and prompt treatment, reduce prevalence. Would a single early cycloplegic photoscreening be as, or more, successful at detection or prediction than the multiple screenings, and more cost-effective? Penalization and occlusion have minimal incidence of reverse amblyopia and/or side-effects, no significant influence on emmetropization, and no consistent effect on sign or size of post-treatment changes in strabismic deviation. There may be a physiologic basis for better age-indifferent outcome than tapped by current treatment methodologies. Infant refractive correction substantially reduces accommodative esotropia and amblyopia incidence without interference with emmetropization. Compensatory prism, alone or post-operatively, and/or minus lens treatment, and/or wide-field fusional amplitude training, may reduce risk of early onset esotropia. Multivariate screening using continuous-scale measurements may be more effective than traditional single-test dichotomous pass/fail measures. Pigmentation may be one parameter because Caucasians are at higher risk for esotropia than non-whites.

Comparison between two hand-held autorefractors: the Sure-Sight and the Retinomax

PURPOSE

To compare the results of manifest refraction obtained with two different hand-held autorefractors (Sure-Sight, Welch Allyn Co. and Retinomax 1, Nikon Inc.) and with the Topcon RMA 6000 on-table autorefractor in order to estimate any potential bias between these refractometers and to compare the diagnostic performances of these two hand-held autorefractors as screening devices.

METHODS

Ninety-eight children were refracted under manifest conditions with the three above-mentioned refractometers and under cycloplegic conditions with the Topcon on-table autorefractor, or by means of retinoscopy. The agreement between the manifest measurements obtained with the three different autorefractors was studied using the method of Bland and Altman. The validity of several thresholds of manifest refractive anomalies as measured with the Sure-Sight and with the Retinomax was estimated by receiver operating characteristic (ROC) curves using cycloplegic measures as reference. results There is a spherical positive bias of 1 D between the Sure-Sight and the Retinomax and better agreement between the Topcon and the Retinomax. The surface area indexes of the ROC curves and the diagnostic performances in term of sensitivity and specificity are better with the Retinomax in cases of hyperopia, astigmatism and anisometropia. For myopia, the Sure-Sight has better performance.

CONCLUSIONS

The results suggest that either device may be sufficient for assessing refractive errors in children in a screening setting. However, because of a bias between both refractometers in measuring the sphere, distinctive referral criteria must be chosen for the detection of hyperopia and myopia. The diagnostic performance is slightly in favor of the Retinomax.

Non-cycloplegic screening for refractive errors in children with the hand-held autorefractor Retinomax: final results and comparison with non-cycloplegic photoscreening

AIMS

To establish the results of refractive screening of preschool children with the hand-held autorefractor Retinomax under non-cycloplegic conditions, and to compare these results with those of photoscreening.

METHODS

Among 1218 children undergoing non-cycloplegic refractive screening, 302 (25%) were also refracted under cycloplegia using the same refractor and were used as controls. Our criteria for a positive screening test were based on the spherical or cylinder values and were: myopia over 3D, astigmatism > or = 2D, spherical or cylindrical anisometropia > or = 1.5D, and hyperopia > or = 1.5D. Absolute myopia over 3D, absolute astigmatism > or = 2D, absolute anisometropia > or = 1.5D and absolute hyperopia > 3.5D were considered as true positives. The sensitivity, specificity, and positive and negative predictive values (PPV and NPV) were calculated within the group of controls for each refractive anomaly. On the basis of Bayes' theorem, these figures were then corrected to yield the true screening results that would be expected in a population without verification and selection bias. To determine the usefulness of this screening technique, the likelihood ratios for positive test results (+LR) were also calculated. The results of this screening in terms of sensitivity, specificity and predictive values were then compared with those of photoscreening.

RESULTS

The basic results of screening with the hand-held autorefractor were as follows: -EHyperopia: sensitivity 46%, specificity 97%, PPV 55%, NPV 96%, +LR 15; -EAstigmatism: sensitivity 37%, specificity 99%, PPV 69%, NPV 96%, +LR 37; -EAnisometropia: sensitivity 66%, specificity 93%, PPV 19%, NPV 99%, +LR 9; -EMyopia: sensitivity 87%, specificity 99%, PPV 33%, NPV 100%, +LR 87. The comparison with photoscreening revealed a similar performance when screening for hyperopia, but the hand-held autorefractor yielded much better figures when screening for astigmatism. In the case of myopia and anisometropia, the lack of consistent information concerning photoscreening invalidates any comparison.

CONCLUSION

The hand-held autorefractor Retinomax appears to have potential as a screening device. Our experience with the non-cycloplegic screening of preschool children for refractive anomalies indicates definite usefulness and reasonable accuracy of the Retinomax for detecting myopia, astigmatism and hyperopia. The weak point of this screening technique is the diagnosis of anisometropia, with only moderate utility and poor accuracy.

Evaluating photoscreeners II: MTI and fortune videorefractor

BACKGROUND

Amblyopia is a public health problem, usually amenable to treatment if detected early. Photoscreeners are camera-based instruments which can detect risk factors for amblyopia such as squint, refractive errors and media opacities.

OBJECTIVE

To evaluate two commercially available photoscreeners, namely the MTI photoscreener (Medical Technology, Iowa City, IA, USA) and the Fortune Optical VRB-100 (Fortune Optical, Padova, Italy) videophotorefractor, in a selected childhood population, having a high prevalence of amblyopia, before undertaking a full-scale trial in the general population.

SUBJECTS AND METHODS

The study design was a double-masked study. One-hundred and five children aged between 12 and 44 months with either normal vision or known visual disorders were photoscreened without cycloplegia using the Fortune and the MTI photoscreeners. Each child had a full ophthalmic examination either on the day of screening or in the preceding 6 months. Risk factors were: any manifest strabismus (squint), hypermetropia >3.5 D, anisometropia > or =1 D sphere, myopia > or =2 D sphere, astigmatism > or =2 D, media opacity or fundus abnormality affecting vision. The prevalence of risk factors for amblyopia was 60%. Photoscreen images were reviewed by two independent masked observers for indicators of amblyopiogenic risk factors and compared to the full ophthalmological examination to determine sensitivity and specificity for each instrument.

RESULTS

Sensitivities and specificities for the detection of risk factors for amblyopia were as follows. Fortune photoscreener: reader 1, sensitivity 60%, specificity 75%; reader 2, sensitivity 68% specificity 86%. MTI photoscreener: reader 1, sensitivity 56%, specificity 79%; reader 2, sensitivity 61%, sensitivity 86%. The results for reader 1 and 2 showed no significant differences for either instrument.

CONCLUSION

Both instruments performed unsatisfactorily in a study population aged 1-4 years with a high prevalence of amblyopiogenic risk factors. Accordingly, we do not believe that either instrument can be recommended to screen for eye disorders in children between the ages of 1 and 4 years because the low prevalence of amblyopia in this population demands very high sensitivity and specificity in order to avoid inappropriate over- or under-referral.

A new objective digital computerized vision screening system

PURPOSE

Fewer than 40% of children in the crucial younger-than-4 age group are evaluated for visual problems by pediatricians. This is due to impracticality from either a clinical or practice efficiency standpoint. Current photoscreening methods require trained readers and suffer from significant subjectivity and interobserver variability. We report a cross-sectional, double-masked study using new digital imaging with objective, automated, computerized image analysis.

METHODS

Two-hundred six children aged 9 months to 16 years were prospectively studied in a University-based pediatric ophthalmology practice. Images were taken by volunteers with a modified digital camera which, when downloaded, were analyzed within 35 seconds by new image analysis software. The analysis was compared to a masked review of a complete pediatric ophthalmic exam.

RESULTS

Overall agreement between physician and the objective computerized analysis was 86.9%. Positive predictive value was 91%, sensitivity was 89%, and specificity was 83%.

CONCLUSIONS

This automated digital imaging screening system eliminates human bias and provides accurate and immediate results. The system requires no special expertise.

Screening for abnormal levels of hyperopia in children: a non-cycloplegic method with a hand held refractor

AIMS

High hyperopia constitutes the majority of refractive errors in large scale visual screening at preschool ages. The authors aimed to assess the validity of the Retinomax hand held refractor to detect high hyperopia in a refractive screening performed without cycloplegia and carried out on children aged 9-36 months. They considered +1.5 D of manifest hyperopia to be the threshold value and abnormal absolute hyperopia to be above +3.5 D.

METHODS

Of the 897 children screened without cycloplegia, 220 were refracted with cycloplegia. The validity of several thresholds of manifest hyperopia was estimated by receiver operating characteristic (ROC) curves using cycloplegic measures as a reference. The reproducibility of Retinomax measurements was assessed. Normal and quick mode measurements were compared using the Wilcoxon test.

RESULTS

The manifest threshold of +1.5 D offered the best combination of sensitivity (70.2%), specificity (94.6%), positive predictive value (78.6%), and negative predictive value (91.9%) to disclose abnormal absolute hyperopia. A good agreement was obtained between the various measurements using Retinomax on the same subject. In the results of this survey, there is no evidence that accommodation is minimised in the normal mode of measurement compared with the quick mode.

CONCLUSION

The Retinomax hand held infrared autorefractor is a suitable instrument to diagnose abnormal hyperopia (manifest hyperopia > +1.5 D) in noncycloplegic refractive screening at preschool ages. It is suggested as the quick mode of measurement as it is more feasible in children (success rate 98.5%).

Inheritance of astigmatism: evidence for a major autosomal dominant locus

Although astigmatism is a frequent refractive error, its mode of inheritance remains uncertain. Complex segregation analysis was performed, by the POINTER and COMDS programs, with data from a geographically well-defined sample of 125 nuclear families of individuals affected by astigmatism. POINTER could not distinguish between alternative genetic models, and only the hypothesis of no familial transmission could be rejected. After inclusion of the severity parameter, COMDS results defined a genetic model for corneal astigmatism and provided evidence for single-major-locus inheritance. These results suggest that genetic linkage studies could be implemented and that they should be limited to multiplex families with severely affected individuals.

Evaluation of photoscreener instruments in a childhood population. 1. Otago photoscreener and Dortmans videophotorefractor

OBJECTIVE

To evaluate two photoscreeners in a childhood population.

STUDY DESIGN

Double-masked study.

SUBJECTS AND METHOD

One hundred and thirteen children aged between 11 and 44 months with either normal vision or known visual disorders were photoscreened without cycloplegia by the Otago and Dortmans (prototype) photoscreeners. Each child had a full ophthalmological examination either on the day of screening or in the proceeding six months. Photoscreen images were reviewed by an independent observer for indicators of amblyopiogenic risk factors, and compared to the full ophthalmological examination to determine sensitivity and specificity for each instrument.

RESULTS

The Otago photoscreener returned a sensitivity of 70% and specificity of 82% for the detection of amblyopiogenic risk factors. The Dortmans photoscreener returned a sensitivity of 70% and specificity of 90%. Both photoscreeners were portable and easily operated.

CONCLUSION

Children can be screened successfully for amblyopiogenic risk factors with these photoscreening systems. Further evaluation is required to determine specificity in a normal population. This would also provide information on the potential usefulness of photoscreeners in a cost effective childhood vision screening program.

Preschool vision screening: rationale, methodology and outcome

Although population outcome studies support the utility of preschool screening for reducing the prevalence of amblyopia, fundamental questions remain about how best to do such screening. Infant photoscreening to detect refractive risk factors prior to onset of esotropia and amblyopia seems promising, but our current understanding of the natural history of these conditions is limited, thus limiting the prophylactic potential of early screening. Screening for strabismic, refractive and ocular disease conditions directly associated with amblyopia is more clearly proven, but the diversity of equipment, methods and subject populations studied make it difficult to draw precise summary conclusions at this point about the efficacy of photoscreening. Sensory-based testing of preschool-age children exhibits a similar combination of promise and limitations. The visual acuity tests most widely used for this purpose are prone to problems of testability and false negatives. Moreover, the utility of random-dot stereograms has been confused by misapplication, and new small-target binocularity tests, while attractive, are as yet inadequately field-proven. The evaluation standard for any screening modality is treatment outcome. However, variables in amblyopia classification and quantitative definition differences, timing of presentation, nonequivalent treatment comparisons, and compliance variability have been uncontrolled in virtually all extant studies of amblyopia treatment outcome, making it difficult or impossible to evaluate either the relative efficacy of different treatment regimens for amblyopia or the effects of age on treatment outcome within the preschool age range. The latter issue is a central one, since existence of such an age effect is the primary rationale for screening at younger rather than older preschool ages. The relatively low prevalence of amblyopia makes it difficult to achieve a high screening yield in terms of predictive value, but functionally increasing prevalence by selective screening of high risk populations causes further problems. Unless a "supertest" can be devised, with very high sensitivity and specificity, health policy decisions will be required to determine which of these two characteristics should be emphasized in screening programs. Performance of screening tests can be optimized, however, with adequate training, perhaps via instructional videotapes.

Visual deprivation at the critical period modulates photic evoked responses

Average visual evoked responses (AVER) were recorded from the striate cortex of normal (control) and monocular visually deprived Long-Evans hooded rats. One month of monocular visual deprivation (MD) at the critical period of development resulted in marked reduction of all the three AVER components (i.e., components P2, N2 and P3) as compared to the control recording (P < 0.001). In control animals, the AVER amplitudes of the two hemispheres were identical, while in MD rats, the P2 and N2 components of the AVER obtained from the hemisphere ipsilateral to the MD eye were markedly smaller than those of the AVER obtained from the contralateral hemisphere (P < 0.001). The latencies of the late components (N2 and P3) obtained from the hemisphere ipsilateral to the MD eyes were significantly delayed as compared to those from the contralateral hemisphere (P < 0.05 for N2, P < 0.01 for P3). The AVER following paired photic stimuli with various time intervals between the stimuli were used to study the neuronal recovery function of control animals compared to MD animals. The AVER to the second stimulus obtained from the MD rats exhibited greater attenuation in their amplitude responses than the AVER obtained from the control group, i.e., slower neuronal recovery. The neurophysiological changes observed in this study may relate to the neurocytological alteration occurring in the striate cortex following monocular visual deprivation at the critical period. In conclusion, AVER recorded from monocular visually deprived rats during the critical period is a simple and reliable electrophysiological animal model to study neuroplasticity during postnatal development.

Is community screening for amblyopia possible, or appropriate?

Photoscreeners are becoming increasingly available and are being widely used to screen for visual abnormalities in young children. However, consideration of accepted criteria for screening programs indicates there is still much further research that needs to be carried out before amblyopia screening could be recommended as a routine component of a community health surveillance program--an adequate description of the potential consequences of an individual developing amblyopia has yet to be provided and the natural history of the condition and factors that determine the effectiveness of treatment have yet to be fully described. While there is the promise of technology that satisfies specific test requirements, this still needs to be trialed in community settings and community trials are required before it will be possible to determine whether the costs that will be incurred in carrying out routine screening and in providing the resources for treatment are warranted. In conclusion, the development of new and possibly more effective technology for screening is only part of the answer to the amblyopia question. While superficially this technology makes screening for amblyopia a possibility, we do not know at this stage whether or not it is appropriate.

Amblyopia

Over the past thirty years, much has been learned about the physiological basis for amblyopia. For many years amblyopia was considered to be a retinal disorder; it has now been well established through animal studies that amblyopia represents functional and morphological effects of visual deprivation on the visual cortex and the lateral geniculate nucleus. With this knowledge has come the recognition of a "sensitive period" of development of the visual system, during which time visual deprivation causes amblyopia. The best approach to managing amblyopia is to detect amblyogenic factors before the age of two years and prevent it through eliminating the causes of visual deprivation. When amblyopia exists, it can be cured if adequately treated in children less than 6-7 years of age. Even in older patients, visual improvement can be achieved with therapy. Current research is aimed at developing substances and delivery modes that will allow the sensitive period of visual development to be manipulated, increasing the period during which it can develop and enhancing preventative and therapeutic measures. In this review selected literature contributing to current understanding of causes, prevention and treatment of amblyopia is discussed. Although many new treatment modalities have been tried, occlusion still seems to be the most successful therapy.

Community photoscreening of six to nine month old infants for amblyopiogenic risk factors

Photorefraction (PR) is gaining acceptance as potentially the most effective objective screening technique for amblyopia risk factors in the preverbal child. This study determined the validity and feasibility of using the Auckland eccentric photorefractor in the detection of amblyopiogenic factors in six to nine month old infants in an established community-based vision screening program. Photographs were analysed and compared to results of clinical examination including cycloplegic refraction. Amblyopia risk factors were present in 7.2% of the infants clinically examined. Analysis only of readable photographs in children who were also clinically examined, gave sensitivities ranging from 71% to 79%, and specificities ranging from 81% to 86%. Inclusion in the analysis of photo-failures lowered sensitivity figures to 56% to 61%, and specificity to 63% to 70%. Photofailures were predominantly due to poor operator technique. Calculation of kappa scores indicated fair observer reliability. In conclusion, PR could provide a feasible and sufficiently reliable screening technique in the infant, but requires adequate training and auditing of screening personnel performance for optimum effectiveness.

Heritability of myopic refractive errors in identical and fraternal twins

The existence of a visual feedback control of eye growth in humans is controversial, as the contributions of genetic and environmental factors are still unknown. To evaluate the heritability of refractive defects, we measured ocular refraction in 19 monozygote and 20 dizygote twin pairs (mean age 5 years). Monozygosity was ascertained by a common chorion, similarity of somatic traits, and identical dermatogliphes and was confirmed in myopes by blood marker diagnosis. Ocular refractive defects and axial length were evaluated by cycloplegic autorefractometry and biometry. By comparing identical and fraternal twins heritability of refractive defects was estimated to be 0.08-0.14; this low value indicates that the observed variability in refractive errors is nongenetic in origin. Three monozygote pairs were anisomyopic; differences between eyes in identical twins were related to the increased axial length of myopic eyes. In one eye, myopia was attributed to visual deprivation induced by a congenital cataract, while in five eyes it was correlated directly to the degree of astigmatic defects. The discordant axial length observed in monozygote twins is nongenetic. In agreement with previous findings reported in the literature, it is proposed that visual impoverishment of retinal images may play an early regulatory role in postnatal eye growth.

Personality, psychophysical stress and myopia progression. A prospective study on 57 university students

Personality profile, psychophysical stress and cycloplegic refraction were evaluated at the baseline (T0) and after 12 months (T1) in 57 university students comprising 39 myopes and 18 emmetropes/hyperopes (controls) whose age, sex distribution and academic results were comparable. At T0, a tendency toward a higher degree of anxiety, somatization and inadequacy was found in myopes in comparison with controls; however, only the anxiety state was different (Wilcoxon signed-rank test P < 0.001). Personality profiles, psychophysical stress and blood levels of cortisol, ACTH, GH, prolactin were similar in myopes and controls. The myopes were classified at T1 as either well-corrected (if their lenses corresponded to refractometer values of +/- 0.50 D and were worn full-time) or undercorrected (if their lenses were > or = 0.75 D with respect to refractometric values and/or were worn part-time). When the spherical cycloplegic values at T0 and T1 were compared, a myopic shift was revealed only in the undercorrected myopes (P < 0.001 in both eyes). These findings suggest that personality profile and psychophysical stress do not play a primary pathogenetic role in myopia. Undercorrection seems to accelerate the progression of myopia.