Investigation of the Accuracy of a Low-Cost, Portable Autorefractor to Provide Well-Tolerated Eyeglass Prescriptions: A Randomized Crossover Trial.

PURPOSE: To compare patient preferences for eyeglasses prescribed using a low-cost, portable wavefront autorefractor versus standard subjective refraction (SR). DESIGN: Randomized, cross-over clinical trial. PARTICIPANTS: Patients aged 18 to 40 years presenting with refractive errors (REs) to a tertiary eye hospital in Southern India. METHODS: Participants underwent SR followed by autorefraction (AR) using the monocular version of the QuickSee device (PlenOptika Inc). An independent optician, masked to the refraction approach, prepared eyeglasses based on each refraction approach. Participants (masked to refraction source) were randomly assigned to use SR- or AR-based eyeglasses first, followed by the other pair, for 1 week each. At the end of each week, participants had their vision checked and were interviewed about their experience with the eyeglasses. MAIN OUTCOME MEASURES: Patients preferring eyeglasses were chosen using AR and SR. RESULTS: The 400 participants enrolled between March 26, 2018, and August 2, 2019, had a mean (standard deviation) age of 28.4 (6.6) years, and 68.8% were women. There was a strong correlation between spherical equivalents using SR and AR (r = 0.97, P < 0.001) with a mean difference of -0.07 diopters (D) (95% limits of agreement [LoA], -0.68 to 0.83). Of the 301 patients (75.2%) who completed both follow-up visits, 50.5% (n = 152) and 49.5% (n = 149) preferred glasses prescribed using SR and AR, respectively (95% CI, 45.7-56.3; P = 0.86). There were no differences in demographic or vision characteristics between participants with different preferences (P > 0.05 for all). CONCLUSIONS: We observed a strong agreement between the prescriptions from SR and AR, and eyeglasses prescribed using SR and AR were equally preferred by patients. Wider use of prescribing based on AR alone in resource-limited settings is supported by these findings.

Accuracy of Autorefraction in Children: A Report by the American Academy of Ophthalmology.

PURPOSE: The purpose of this assessment is to evaluate the accuracy of autorefraction compared with cycloplegic retinoscopy in children. METHODS: Literature searches were last conducted in October 2019 in the PubMed and the Cochrane Library databases for studies published in English. The combined searches yielded 118 citations, of which 53 were reviewed in full text. Of these, 31 articles were deemed appropriate for inclusion in this assessment and subsequently assigned a level of evidence rating by the panel methodologists. Four articles were rated level I, 11 were rated level II, and 16 were rated level III articles. The 16 level III articles were excluded from this review. RESULTS: Thirteen of the 15 studies comparing cycloplegic autorefraction with cycloplegic retinoscopy found a mean difference in spherical equivalent or sphere of less than 0.5 diopters (D); most were less than 0.25 D. Even lower mean differences were found when evaluating the cylindrical component of cycloplegic autorefraction versus cycloplegic retinoscopy. Despite low mean variability, there was significant individual measurement variability; the 95% limits of agreement were wide and included clinically relevant differences. Comparisons of noncycloplegic with cycloplegic autorefractions found that noncyloplegic refraction tends to over minus by 1 to 2 D. CONCLUSIONS: Cycloplegic autorefraction is appropriate to use in pediatric population-based studies. Cycloplegic retinoscopy can be valuable in individual clinical cases to confirm the accuracy of cycloplegic autorefraction, particularly when corrected visual acuity is worse than expected or the autorefraction results are not consistent with expected findings.

Retinoscopy as a Screening Tool for Keratoconus.

PURPOSE: To investigate the validity and reliability of retinoscopy in screening for keratoconus using the rotating Pentacam Scheimpflug camera as the gold standard comparison. METHODS: Patients between the ages of 10 and 30 years who were referred to the outpatient clinic with keratoconus, keratoconus suspect, reduced vision, eye discomfort or frequent change of glasses, or for refraction or refractive surgery, were screened by two independent and masked retinoscopists for the presence of scissoring reflex. Patients then underwent vision testing, slit lamp examination, and Pentacam imaging. A diagnosis of keratoconus by Pentacam was made if the final D index in the Belin and Ambrósio Display was ≥2.69. The results of retinoscopy and Pentacam examinations were compared to assess the validity and reliability of the test. RESULTS: A total of 123 patients (67 male patients and 45 female patients) with a mean age of 21 years ±5.6 (range 10-30 years) comprising 245 eyes were included. There were 87 eyes with keratoconus, and using the Amsler-Krumeich classification, 67.8%, 26.4%, 2.3%, and 3.4% of the eyes had stage I, II, III, and IV, respectively. Sensitivity, specificity, positive predictive value, and negative predictive value of retinoscopy were 97.7%, 79.9%, 70.8%, and 98.4%, respectively. The area under the curve was 0.88 (95% confidence interval, 0.83-0.92). There was excellent agreement between the 2 retinoscopists (Cohen's kappa value 0.84). CONCLUSIONS: Retinoscopy appears to be a very sensitive and reliable test for detecting keratoconus including early disease. Such a test may be implemented in population-based screening programs for keratoconus.

Evaluation of the WinROP system for identifying retinopathy of prematurity in Czech preterm infants.

AIMS: Retinopathy of Prematurity (ROP) is a potentially serious condition that can afflict preterm infants. Timely and correct identification of individuals at risk of developing a serious form of ROP is therefore of paramount importance. WinROP is an online system for predicting ROP based on birth weight and weight increments. However, the results vary significantly for various populations. It has not been evaluated in the Czech population. This study evaluates the test characteristics (specificity, sensitivity, positive and negative predictive values) of the WinROP system in Czech preterm infants. METHODS: Data on 445 prematurely born infants included in the ROP screening program at the University Hospital Ostrava, Czech Republic, were retrospectively entered into the WinROP system and the outcomes of the WinROP and regular screening were compared. RESULTS: All 24 infants who developed high-risk (Type 1 or Type 2) ROP were correctly identified by the system. The sensitivity and negative predictive values for this group were 100%. However, the specificity and positive predictive values were substantially lower, resulting in a large number of false positives. Extending the analysis to low risk ROP, the system did not provide such reliable results. CONCLUSIONS: The system is a valuable tool for identifying infants who are not likely to develop high-risk ROP and this could help to substantially reduce the number of preterm infants in need of regular ROP screening. It is not suitable for predicting the development of less serious forms of ROP which is however in accordance with the declared aims of the WinROP system.

OPD-Scan III: a repeatability and inter-device agreement study of a multifunctional device in emmetropia, ametropia, and keratoconus.

The purpose of this study was to test the measurements of a multifunctional device, the NIDEK OPD-Scan III in terms of repeatability and agreement with retinoscopy and Pentacam in cases with emmetropia, ametropia, and KCN (grade 1-3). We enrolled 170 eyes (40 in each group of emmetropia and ametropia, and 90 in the 3 KCN subgroups). Acquisitions were done twice by a single technician to check the intra class correlation, repeatability index, and precision. To assess agreement, we compared OPD-Scan III with retinoscopy and Pentacam results by two blinded technicians. All device functions had acceptable precision in groups with emmetropia, ametropia, and KCN1, except spherical error in ammetropics (0.97 D). In KCN2, repeatability was acceptable with the refractive function, topography, and ocular aberrations but was more than 1.0 D for corneal aberrations. In KCN3, repeatability was low for the refractive function and corneal spherical aberration. Refractive data were not convertible to those obtained by retinoscopy in any group. OPD-Scan III keratometry data were interchangeable with Pentacam counterparts in emmetropes, ammetropes, and KCN1. In KCN2, the OPD-Scan III-Pentacam agreement for Kmax was 0.71 D, and there was 1.25 D difference in Kmin. No OPD-Scan III-Pentacam agreement was observed in KCN3. OPD- Scan III is a multifunctional device with acceptable repeatability in emmetropic, ammetropic, and KCN cases. Its measurements of corneal curvature and ocular aberrations are better than other functions. In cases with high degrees of refractive error and corneal irregularities, device repeatability and agreement with Pentacam is decreased.

Clinical Competency of 1-Year Trained Vision Technicians in Andhra Pradesh, India.

PURPOSE: To assess clinical competency of 1-year trained vision technicians (VTs) in detecting and referring causes of visual impairment in India. METHODS: Eye examination results and management plans for 328 patients examined by 24 VTs in 24 vision centers of LV Prasad Eye Institute in Andhra Pradesh were compared with those of a standard optometrist who examined the same patients. Eye examinations included retinoscopy and subjective refraction, slit lamp examination, applanation tonometry and undilated direct ophthalmoscopy. Data were analyzed for level of concordance in retinoscopy, spectacle prescription, disease detection and referral. RESULTS: VTs demonstrated moderate to good levels of agreement in refraction, disease detection and referral. Sensitivity and specificity for ocular pathology identification were 77.4% (95% confidence interval, CI, 69.4-84.2%) and 86.6% (95% CI 81.1-91.1%), respectively. The highest sensitivity was demonstrated in detecting significant cataract (91.5%) and refractive error (83.0%). VT spectacle prescriptions were accurate 76% of the time for mean spherical equivalent and 65% of the time for astigmatism. VT sensitivity in detecting posterior segment abnormalities was low (18.5%) resulting in failure to detect retinal conditions such as diabetic retinopathy and maculopathy. Despite lack of recognition of the specific pathology, referral decisions were correct in 78.4% of cases. CONCLUSION: VTs in India competently detect and manage or refer the two most common causes of visual impairment; uncorrected refractive error and cataract. Over two-thirds of patients received accurate and appropriate services from VTs, suggesting that they are a useful and competent cadre for rural and remote eye care.

Photorefraction estimates of refractive power varies with the ethnic origin of human eyes.

Eccentric infrared photorefraction is an attractive tool for measuring refractive errors of young children and uncooperative subjects, for it allows quick and non-invasive acquisition of data from both eyes simultaneously over a reasonably large dioptric range. Accuracy of refraction in this technique depends on calibration of luminance slope formed across the pupil into diopters (defocus calibration factor). Commercial photorefractors, like the PowerRef 3™ used in this study, employ an universal defocus calibration factor from one population (Caucasian) to convert raw data of all populations. This study reports significantly larger defocus calibration factors of PowerRef 3™ in 132 East Asian, African and Indian eyes, relative to the machine's default calibration (p < 0.001). The calibration slope of 50 Indian eyes was over-estimated by 64 ± 11% (mean ± 95%CI), vis-à-vis, retinoscopy (p < 0.001). The error reduced to ~6-7% upon rescaling the data using a calibration factor specific for Indian eyes or to that individual (p > 0.9, relative to no over-estimation). Our results therefore strongly suggest the use of an ethnicity- or individual-specific defocus calibration factor for accurate estimation of refraction using photorefraction. Inaccurate refraction estimates due to calibration errors will otherwise severely undermine the advantages of this technique.

Comparison of photorefraction, autorefractometry and retinoscopy in children.

Photorefractive devices have been evaluated for their effectiveness in detecting anisometropia, hyperopia, myopia, and astigmatism. We investigated the reliability of Plusoptix S08, the newest photoscreener, and Topcon autorefractometer by comparing them with cycloplegic retinoscopy. Plusoptix S08, cycloplegic retinoscopy, and cycloplegic autorefractometer measurements for 235 eyes of 118 children (59 female, 59 male) with a mean age of 4.9 ± 2.6 and median age of 5 years (range 1-12) were conducted. The Plusoptix S08 produced the following mean (± SD) results--spherical 0.27 ± 1.64, cylindrical power -0.81 ± 0.71, axis 89.73 ± 61.18, and spherical equivalent -0.05 ± 1.61. The cycloplegic retinoscopy produced the following mean (± SD) results--spherical 0.12 ± 1.35, cylindrical power -0.89 ± 0.71, axis 92.18 ± 68.39, and spherical equivalent -0.15 ± 1.31. The cycloplegic autorefractometer produced the following mean (± SD) results--spherical 0.16 ± 1.44, cylindrical power -0.88 ± 0.72, axis 90.86 ± 68.21, and spherical equivalent -0.12 ± 1.41. This study has shown that cycloplegic autorefractometer and retinoscopy results are similar and Plusoptix S08 is a very safe, easy-to-use and reliable screening method of refraction, especially for ophthalmologists unskilled in retinoscopy. Plusoptix S08 is a useful tool for estimating refraction in patients for whom conventional autorefraction is not an option.

Effect of target distance on accommodative amplitude measured using the minus lens technique.

BACKGROUND: The aim was to investigate the effect on the measured amplitude of accommodation and repeatability of using the minus lens technique with the target at distance or near. METHODS: Forty-three students (average age: 21.17 ± 1.50 years, 35 female) had their amplitude of accommodation measured with minus lenses on top of their distance correction in a trial frame with the target at far (6.0 m) or near (0.4 m). The minus lens power was gradually added with steps of 0.25 D. Measurements were taken on two occasions at each distance, which were separated by a time interval of at least 24 hours. RESULTS: The measured amplitude at six metres was significantly lower than that with the target at 40 cm, by 1.56 ± 1.17 D (p < 0.001) and this varied between individuals (r = 0.716, intraclass correlation coefficient = 0.439). With either target distance, repeated measurement was highly correlated (r > 0.9) but the agreement was better at 6.0 m (±0.74 D) than at 40 cm (± 0.92 D). CONCLUSION: The measurements of the amplitude of accommodation with the minus lens technique using targets at far or near are not comparable and the difference between the target distances may provide clinically relevant information.

Accommodative response/stimulus by dynamic retinoscopy: near add guidelines.

PURPOSE: Monocular estimation method (MEM) dynamic retinoscopy and low neutral (LN) dynamic retinoscopy are common procedures for evaluating the need for near-point plus adds for improved near-point performance in non-presbyopes. A combination of MEM and LN has been suggested to be a method of plotting accommodative response/accommodative stimulus functions and evaluating guidelines for prescribing from MEM. METHODS: Using a combined MEM-LN procedure, MEM was performed on 80 young adults at 40 cm, with distance correction and with plus adds in 0.25 D steps up to and including +2.00 D. Modified Thorington dissociated phorias were also performed with each of the plus adds. Subjects picked a preferred add, which subjectively made print easiest and most comfortable to read. RESULTS: The mean preferred add was +0.58 D over the distance prescription. The add derived from subtracting 0.25 D from the lag of accommodation with distance correction averaged 0.10 D more plus than the preferred add. The add at which dynamic retinoscopy showed a "with" motion of 0.25 D averaged 0.54 more plus than the preferred add. The add at which dynamic retinoscopy showed a "with" motion of 0.50 D averaged 0.16 more plus than the preferred add. CONCLUSIONS: Adds derived from subtracting 0.25 D from the lag with distance correction and from finding the add that yields 0.50 D of "with" motion compared favorably with the preferred adds on average, but the standard deviations of the differences were high. Those guidelines could be reasonable starting points for the prescription of near-point plus adds for non-presbyopes, but follow-up testing to confirm or adjust add power would be advisable in the clinical setting.

Dynamic distance direct ophthalmoscopy, a novel technique to assess accommodation in children.

AIM: To describe and compare dynamic distance direct ophthalmoscopy (DDDO) with dynamic retinoscopy (DR) in assessment of accommodation in children. MATERIALS AND METHODS: This prospective observational study had four components. Component 1: to understand the characteristic digital images of DDDO. Component 2: to compare DDDO with DR for detection of accommodative defects in children (1-16 years). Component 3: to compare DDDO with DR for the detection of completeness of pharmacologically induced cycloplegia in children (5-16 years) and Component 4: to assess which one of the two techniques was more sensitive to detect onset of cycloplegia after instillation of 1% cyclopentolate eye drops. RESULTS: Component 1: image analysis of DDDO on two subjects (7 years and 35 years) demonstrated superior pupillary crescent that progressively disappeared with increasing accommodation. Concurrently an inferior crescent appeared that became bigger in size with increasing accommodation. Component 2: the prevalence of defects in accommodation was 3.3% (33/1000 children). Three had unilateral accommodation failure. Sensitivity of DDDO was 94%, specificity 100%, positive predictive value 100%, negative predictive value 99%, and clinical agreement (kappa) 0.97. Component 3: in the detection of completeness of pharmacologically induced cycloplegia (n=30), the sensitivity of DDDO was 94%, specificity 96%, positive predictive value 97%, negative predictive value 93% and kappa 0.9. DR had two false positives. DDDO had one false negative. Component 4: DDDO detected onset of pharmacologically induced cycloplegia 5 min earlier than DR (n=5). CONCLUSION: DDDO is a novel, simple, clinical and reliable method to assess accommodation in young children. This test can assess the accommodative response of both eyes simultaneously.

Validity of noncycloplegic refraction in the assessment of refractive errors: the Tehran Eye Study.

PURPOSE: To determine the sensitivity and specificity of noncycloplegic autorefraction for determining refractive status compared to cycloplegic autorefraction. METHODS: The target population was noninstitutionalized citizens of all ages, residing in Tehran in 2002, selected through stratified cluster sampling. From 6497 eligible residents, 70.3% participated in the study, from August to November 2002. Here, we report data on 3501 people over the age of 5 years who had autorefraction with and without cycloplegia (two drops of cyclopentolate 1.0% 5 min apart, with autorefraction 25 min after the second drop). RESULTS: Overall, the sensitivity of noncycloplegic autorefraction for myopia was 99%, but the specificity was only 80.4%. In contrast, the sensitivity for hyperopia was only 47.9%, but the specificity was 99.4%. At all ages, noncycloplegic autorefraction overestimated myopia and underestimated hyperopia. Overestimation of myopia was highest in the 21-30 and 31-40 year groups. Underestimation of hyperopia was high up to the age of 50 (20-40%), but decreased with age, to about 8% after the age of 50, down to almost 0% after 70. The difference in mean spherical equivalent with and without cycloplegia fell from 0.71 dioptres (D) in the 5-10 age group to 0.14D in those over 70. CONCLUSION: Use of noncycloplegic autorefraction in epidemiological studies leads to considerable errors relative to cycloplegic measurements, except in those over 50-60. The difference between cycloplegic and noncycloplegic measurements varies with age and cycloplegic refractive category, and there is considerable individual variation, ruling out adjusting noncycloplegic measurements to obtain accurate cycloplegic refractions.

A function for quality evaluation of retinal vessel segmentations.

Retinal blood vessel assessment plays an important role in the diagnosis of ophthalmic pathologies. The use of digital images for this purpose enables the application of a computerized approach and has fostered the development of multiple methods for automated vascular tree segmentation. Metrics based on contingency tables for binary classification have been widely used for evaluating the performance of these algorithms. Metrics from this family are based on the measurement of a success or failure rate in the detected pixels, obtained by means of pixel-to-pixel comparison between the automated segmentation and a manually-labeled reference image. Therefore, vessel pixels are not considered as a part of a vascular structure with specific features. This paper contributes a function for the evaluation of global quality in retinal vessel segmentations. This function is based on the characterization of vascular structures as connected segments with measurable area and length. Thus, its design is meant to be sensitive to anatomical vascularity features. Comparison of results between the proposed function and other general quality evaluation functions shows that this proposal renders a high matching degree with human quality perception. Therefore, it can be used to enhance quality evaluation in retinal vessel segmentations, supplementing the existing functions. On the other hand, from a general point of view, the applied concept of measuring descriptive properties may be used to design specialized functions aimed at segmentation quality evaluation in other complex structures.

ROC analysis of the accuracy of Noncycloplegic retinoscopy, Retinomax Autorefractor, and SureSight Vision Screener for preschool vision screening.

PURPOSE: To evaluate, by receiver operating characteristic (ROC) analysis, the accuracy of three instruments of refractive error in detecting eye conditions among 3- to 5-year-old Head Start preschoolers and to evaluate differences in accuracy between instruments and screeners and by age of the child. METHODS: Children participating in the Vision In Preschoolers (VIP) Study (n = 4040), had screening tests administered by pediatric eye care providers (phase I) or by both nurse and lay screeners (phase II). Noncycloplegic retinoscopy (NCR), the Retinomax Autorefractor (Nikon, Tokyo, Japan), and the SureSight Vision Screener (SureSight, Alpharetta, GA) were used in phase I, and Retinomax and SureSight were used in phase II. Pediatric eye care providers performed a standardized eye examination to identify amblyopia, strabismus, significant refractive error, and reduced visual acuity. The accuracy of the screening tests was summarized by the area under the ROC curve (AUC) and compared between instruments and screeners and by age group. RESULTS: The three screening tests had a high AUC for all categories of screening personnel. The AUC for detecting any VIP-targeted condition was 0.83 for NCR, 0.83 (phase I) to 0.88 (phase II) for Retinomax, and 0.86 (phase I) to 0.87 (phase II) for SureSight. The AUC was 0.93 to 0.95 for detecting group 1 (most severe) conditions and did not differ between instruments or screeners or by age of the child. CONCLUSIONS: NCR, Retinomax, and SureSight had similar and high accuracy in detecting vision disorders in preschoolers across all types of screeners and age of child, consistent with previously reported results at specificity levels of 90% and 94%.

The impact of off the visual axis retinoscopy on objective central refractive measurement in adult clinical practice: a prospective, randomized clinical study.

PURPOSE: The objective of this study was to examine the effect of the off axis retinoscopy on objective central refractive measurement in adult clinical practice. METHODS: In all, 40 subjects underwent undilated retinoscopy in a randomly selected eye both on and off the visual axis by a single masked examiner. Off axis retinoscopy was defined as retinoscopy performed with the testing eye of the examiner aligned with the contralateral (non-test) eye of the subject resulting in an off axis deviation in the nasal horizontal visual field. Retinoscopy was performed in negative cylinder only and spherocylindrical measurements were converted to power vectors for analysis. Paired t-test was used to assess differences in M, J(0) and J(45) power vectors including differences between mean aided and unaided LogMar acuities. RESULTS: In all, 14 subjects were myopic (SE≤-0.5 D), 13 subjects were emmetropic (SE between -0.49 and 1.0 D) and 13 subjects were hyperopic (SE >1.0 D). Mean angle of deviation was 5.58° in the nasal horizontal visual field. J(0) showed a significant negative shift in those with myopia (P<0.001) and emmetropia (P=0.049) following off axis retinoscopy. No significant differences in M, J(0) and J(45) were found in the hyperopes. Mean aided LogMar acuities after on and off axis retinoscopy were both significantly better than mean unaided LogMar VA (P<0.001 in both cases). CONCLUSION: Small degrees of off axis retinoscopy encountered in everyday clinical practice can induce errors in objective central refractive measurement.

Modified bell retinoscopy: measuring accommodative lag in children.

PURPOSE: To describe a modified bell retinoscopy (MBR) method for quantifying accommodative lag in children and to assess its repeatability and comparability with other techniques. METHODS: In MBR, the target is advanced toward the patient until the retinoscopic reflex is neutralized. A "standardized 40-cm target estimate" of lag was derived for each child using data from three retinoscope distances. Within-visit repeatability was assessed in normal children 5 to 23 months of age, a heterogeneous group of clinic patients, and a group of children with Down syndrome. Clinic patients were tested on separate days for between-visit repeatability and, also, with Nott retinoscopy (NR) and the monocular estimate method (MEM) on day 2. RESULTS: MBR correlated with NR (r = 0.84) and MEM (r = 0.82). MBR and NR estimates were lower than MEM for high lags. Within-visit repeatability of the standardized 40-cm target estimate of MBR in normal children and clinic patients varied with the amount of lag (p < 0.0001). The repeatability index for 0.50 D lag was 0.49 D and for 1.00 D lag it was 0.80 D. Repeatability was similar in children with Down syndrome. In clinic patients, the between-visit repeatability index for 0.50 D lag was 0.60 D for the second estimate of each day, with lower repeatability for the first measure of each day. Repeatability did not vary with age or refractive error. The decrease in repeatability with high lag may be attributable to spatial measurement error. CONCLUSIONS: MBR estimates of accommodative lag correlate with traditional dynamic retinoscopy measures over a wide range of lags and show comparable repeatability. MBR may be a useful addition to the repertoire of clinical tools available for assessing accommodation in young children.

Accuracy of noncycloplegic refraction in primary school children in southern Thailand.

OBJECTIVE: To evaluate the accuracy of noncycloplegic refraction compared with cycloplegic refraction in diagnosing refractive error in primary school children in southern Thailand. MATERIAL AND METHOD: This is a cross-sectional study. One hundred twenty children aged from 6-13 years who had visual acuity of 20/40 or worse in at least one eye were included. All the children underwent autorefraction using a Nikon model NRK-8000, retinoscopy and subjective refraction without cycloplegia followed by cycloplegic refraction. The spherical power (SP), cylindrical power (CP), cylindrical axis (CA), and spherical equivalence (SE) from each noncycloplegic technique were compared to cycloplegic refraction using the mean difFerence. The authors also showed the percentage agreement between the data obtainedfrom the three noncycloplegic techniques with those from cycloplegic refraction. RESULTS: The SE mean diFference of noncycloplegic autorefraction, retinoscopy and subjective refraction with cycloplegic refraction were -0.85, -0.19, and -0.26, respectively (p < 0.0001). The data for the SP was similar The cylindrical power mean diFferences were -0.18, -0.13, and -0.02, respectively. The percentage agreements of SE between noncycloplegic autorefraction, retinoscopy, and subjective refraction with cycloplegic refraction within +/- 0.5 diopter (D) were 31.25%, 80.84%, and 81.66%, respectively. For the cylindrical power, the percentages of patients who were within +/- 0.5 D were 87.50%, 94.58%, and 97.50%. The percentages of patients who were within 10 degrees of the cylindrical axis were 73.46%, 96.91%, and 97.53%. CONCLUSION: Noncycloplegic retinoscopy and subjective refraction are clinically accurate and can be applied for refractive error screening in primary school children. Noncycloplegic autorefraction has a tendency towards minus over-correction.

Retinal vessel oximetry-calibration, compensation for vessel diameter and fundus pigmentation, and reproducibility.

The purpose of this study was to measure the hemoglobin oxygenation in retinal vessels and to evaluate the sensitivity and reproducibility of the measurement. Using a fundus camera equipped with a special dual wavelength transmission filter and a color charge-coupled device camera, two monochromatic fundus images at 548 and 610 nm were recorded simultaneously. The optical densities of retinal vessels for both wavelengths and their ratio, which is known to be proportional to the oxygen saturation, were calculated. From 50-deg images, the used semiautomatic vessel recognition and tracking algorithm recognized and measured vessels of 100 microm or more in diameter. On average, arterial and venous oxygen saturations were measured at 98+/-10.1% and 65+/-11.7%, respectively. For measurements in the same vessel segments from the five images per subject, standard deviations of 2.52% and 3.25% oxygen saturation were found in arteries and veins, respectively. Respiration of 100% oxygen increased the mean arterial and venous oxygen saturation by 2% and 7% respectively. A simple system for noninvasive optical oximetry, consisting of a special filter in a fundus camera and software, was introduced. It is able to measure the oxygen saturation in retinal branch vessels with reproducibility and sensitivity suitable for clinical investigations.

Accommodative response in pre-presbyopes with visual impairment and its clinical implications.

PURPOSE: There are isolated reports that accommodative response is reduced in some populations with low vision. The purpose of this study was to measure accommodative response in a wider range of pre-presbyopes with visual impairment and to examine what factors may affect accommodation among the low vision population. METHODS: Accommodative responses for accommodative demands between 4 and 10 D were measured with dynamic retinoscopy in 21 subjects with low vision due to a variety of disorders and in 40 control subjects, aged 3 to 35 years. The control subjects were divided into age groups of 3 to 5, 6 to 10, 11 to 26, and 27 to 35 years, and the response of each subject with low vision was compared against the age-matched control group. The slope of the accommodative function and the mean error of the accommodative response were also calculated. RESULTS: Eighty-six percent of the subjects with low vision showed responses that were outside the 95% range of normal. The deficit increased with increasing accommodative demand. Reduced accommodation was not predicted by age, visual acuity, presence of nystagmus, refractive error or time of onset of the disorder. The results show that the accommodation errors are often greater than predicted by increased depth of focus due to poor visual acuity. CONCLUSIONS: It seems likely that accommodative response is based on many factors that may be present in an eye with low vision, which interact in a complex fashion.