Testing the FOCOMETER--A new refractometer

Comparison between focometer and autorefractor in the measurement of refractive error among students in underserved community of sub-Saharan Africa

PurposeTo compare focometer and autorefractor in the measurement of refractive errors among students in an underserved community of sub-Saharan Africa.MethodsThe study was a descriptive comparative cross-sectional study conducted in October/November 2014 among secondary school students of Ijaiye-Orile, Oyo State, Nigeria. Students were selected using systematic random sampling method. Ocular examination and measurement of refractive error was carried out on each student using a focometer and an autorefractor.ResultsA total of 230 students were studied. Mean age of the students was 15.1±1.9 years with a range of 13-21 years. Refractive error was detected in 95 (41.3%) of the students using autorefractor and in 81 (35.2%) with focometer. Among those found to have refractive error using autorefractor, 75 (78.9%) students had a difference of ≤±0.75 DS between the autorefractor and focometer readings. The sensitivity and specificity of the focometer relative to the autorefractor was 73.7% and 91.9%, respectively.ConclusionThe focometer is comparable to the autorefractor in the measurement of refractive error because of its high sensitivity and specificity. The high positive and negative predictive values makes the focometer an effective tool for both screening and diagnosis of refractive error in rural areas among secondary schools students. Its use would make refractive service available and affordable to individuals living in the resource poor rural communities thereby reducing the burden of refractive error in such areas. The focometer should also be a useful tool in school eye health programs.

Self-adjustable glasses in the developing world

Uncorrected refractive errors are the single largest cause of visual impairment globally. Refractive errors are an avoidable cause of visual impairment that are easily correctable. Provision of spectacles is a cost-effective measure. Unfortunately, this simple solution becomes a public health challenge in low- and middle-income countries because of the paucity of human resources for refraction and optical services, lack of access to refraction services in rural areas, and the cost of spectacles. Low-cost approaches to provide affordable glasses in developing countries are critical. A number of approaches has been tried to surmount the challenge, including ready-made spectacles, the use of focometers and self-adjustable glasses, among other modalities. Recently, self-adjustable spectacles have been validated in studies in both children and adults in developed and developing countries. A high degree of agreement between self-adjustable spectacles and cycloplegic subjective refraction has been reported. Self-refraction has also been found to be less prone to accommodative inaccuracy compared with non-cycloplegic autorefraction. The benefits of self-adjusted spectacles include: the potential for correction of both distance and near vision, applicability for all ages, the empowerment of lay workers, the increased participation of clients, augmented awareness of the mechanism of refraction, reduced costs of optical and refraction units in low-resource settings, and a relative reduction in costs for refraction services. Concerns requiring attention include a need for the improved cosmetic appearance of the currently available self-adjustable spectacles, an increased range of correction (currently −6 to +6 diopters), compliance with international standards, quality and affordability, and the likely impact on health systems. Self-adjustable spectacles show poor agreement with conventional refraction methods for high myopia and are unable to correct astigmatism. A limitation of the fluid-filled adjustable spectacles (AdSpecs, Adaptive Eyecare Ltd, Oxford, UK) is that once the spectacles are self-adjusted and the power fixed, they become unalterable, just like conventional spectacles. Therefore, they will need to be changed as refractive power changes over time. Current costs of adjustable spectacles are high in developing countries and therefore not affordable to a large segment of the population. Self-adjustable spectacles have potential for “upscaling” if some of the concerns raised are addressed satisfactorily.

Self correction of refractive error among young people in rural China: results of cross sectional investigation

OBJECTIVE

To compare outcomes between adjustable spectacles and conventional methods for refraction in young people.

DESIGN

Cross sectional study.

SETTING

Rural southern China.

PARTICIPANTS

648 young people aged 12-18 (mean 14.9 (SD 0.98)), with uncorrected visual acuity ≤ 6/12 in either eye.

INTERVENTIONS

All participants underwent self refraction without cycloplegia (paralysis of near focusing ability with topical eye drops), automated refraction without cycloplegia, and subjective refraction by an ophthalmologist with cycloplegia.

MAIN OUTCOME MEASURES

Uncorrected and corrected vision, improvement of vision (lines on a chart), and refractive error.

RESULTS

Among the participants, 59% (384) were girls, 44% (288) wore spectacles, and 61% (393/648) had 2.00 dioptres or more of myopia in the right eye. All completed self refraction. The proportion with visual acuity ≥ 6/7.5 in the better eye was 5.2% (95% confidence interval 3.6% to 6.9%) for uncorrected vision, 30.2% (25.7% to 34.8%) for currently worn spectacles, 96.9% (95.5% to 98.3%) for self refraction, 98.4% (97.4% to 99.5%) for automated refraction, and 99.1% (98.3% to 99.9%) for subjective refraction (P = 0.033 for self refraction v automated refraction, P = 0.001 for self refraction v subjective refraction). Improvements over uncorrected vision in the better eye with self refraction and subjective refraction were within one line on the eye chart in 98% of participants. In logistic regression models, failure to achieve maximum recorded visual acuity of 6/7.5 in right eyes with self refraction was associated with greater absolute value of myopia/hyperopia (P<0.001), greater astigmatism (P = 0.001), and not having previously worn spectacles (P = 0.002), but not age or sex. Significant inaccuracies in power (≥ 1.00 dioptre) were less common in right eyes with self refraction than with automated refraction (5% v 11%, P<0.001).

CONCLUSIONS

Though visual acuity was slightly worse with self refraction than automated or subjective refraction, acuity was excellent in nearly all these young people with inadequately corrected refractive error at baseline. Inaccurate power was less common with self refraction than automated refraction. Self refraction could decrease the requirement for scarce trained personnel, expensive devices, and cycloplegia in children's vision programmes in rural China.

Simple Spectacles for Adult Refugees on the Thailand–Burma Border

PURPOSE

This article describes the development of, and outputs from, a program in which trained refugee health workers provided spherical lenses to adult refugees along the Thailand-Burma border.

METHODS

Between 1998 and 2001, the International Rescue Committee trained 48 refugee health workers in basic refraction courses. Once trained, these health workers conduct weekly eye clinics in several refugee camps and one migrant community covering a total population of 142,000. We supplied spherical lenses in 11 powers from +1.00 to +4.00 in 0.50-D steps and from -1.00 to -2.50 in 0.50-D steps. We collected output data from these clinics for the year 2001.

RESULTS

In 2001, these clinics provided a total of 7219 eyeglasses. Approximately 84% of all lenses given were for presbyopia, approximately 10% for myopia, and approximately 6% for hyperopia. Our spectacle provision rates per 100,000 persons were 4284 for presbyopia, 482 for myopia, and 317 for hyperopia. Our target provision rates, which would allow the average wearer to get a new pair every 3 to 4 years, was met for presbyopia, but not met for myopia or hyperopia. Few corrections for high errors were needed and only 92 people were found to need powers higher than we provided. In 2001, the cost per eyeglass recipient was approximately $7.00.

CONCLUSIONS

Training refugee health workers has allowed for sustainable, low-cost spectacle provision to a large population over an extensive geographic area in a challenging environment.

Quantification of Refractive Error: Comparison of Autorefractor and Focometer

PURPOSE

The advantages of a focometer (FOCOMETER) over other methods of refraction for use in developing countries are that it is lightweight, compact, relatively inexpensive, fairly quick, and easy to use with minimal training. This clinical trial compared the repeatability, validity, and ease of use of the focometer with an autorefractor.

METHODS

The refractive status of the right eye of 80 participants was determined with an autorefractor (Canon RK3). Three measurements were also taken with the focometer.

RESULTS

The spherical equivalent (M) of the focometer was 0.25 D more positive than the autorefractor (p < 0.001) and 84% of measurements were within 0.75 D of the autorefractor. The autorefractor detected astigmatism in 91% (73) of the eyes, whereas the focometer identified only 32% (26). The design of the clock target restricts cylinder axis accuracy to the nearest 15 degrees . There was evidence of a learning effect for the focometer: the second and third measurements were more repeatable in the untrained group. There were no differences between the mean (1.03 +/- 2.28) and third focometer (-1.05 +/- 2.32) measurements (p = 0.34). However, using the third focometer measurement, 94% of participants had visual acuities of at least 6/12(-2).

CONCLUSIONS

This study highlighted the focometer's restricted power range, inaccuracy of astigmatism and axis determination, and dependence on subject understanding and compliance. Therefore, in most clinical settings, the focometer would not be adequate for quantifying refractive error, but the focometer spherical equivalent was within acceptable limits of the autorefractor, and the visual acuity with lenses determined by the focometer indicates its potential usefulness in public health settings, especially where only spherical ready-made spectacles are dispensed. There may be more cost-effective ways to determine refractive error in these circumstances. A potentially important enhancement in focometer methodology that improves its ease of use was identified: use only the third measurement for each eye.

Accommodation measurements in a prepresbyopic and presbyopic population

PURPOSE

To study the efficacy of several subjective and objective methods of accommodation measurement in normal prepresbyopic and presbyopic populations to identify appropriate methods for measuring the outcome of accommodative restorative procedures.

SETTING

University of Houston, College of Optometry, Houston, Texas, USA.

METHODS

Thirty-one normal subjects with a mean age of 43.7 years (range 31 to 53 years) participated. Accommodation was measured monocularly using 3 subjective approaches--the push-up test, minus lenses to blur, and a focometer--and 2 approaches measured with a Hartinger coincidence refractometer, in which accommodation was stimulated with minus lenses to blur and topical pilocarpine 6%.

RESULTS

The push-up method overestimated accommodative amplitude relative to objective measures in 28 subjects. Two subjective methods, minus lenses to blur and the focometer, produced comparable results, but with lower amplitudes in younger subjects and higher amplitudes in older subjects compared with objective methods. Comparable results were obtained when accommodation was stimulated in 1 of 2 ways and measured with the Hartinger. Pilocarpine elicited stronger accommodative responses than distance blur for subjects with low accommodative amplitudes. Pilocarpine 6% produced stronger responses in subjects with light irides than in those with dark irides.

CONCLUSIONS

Hartinger-measured accommodation provides more realistic measurement of accommodative amplitude than the subjective methods tested, especially in the presbyopic population. In presbyopic subjects, the subjective tests resulted in accommodative amplitudes up to 4.0 diopters greater than those measured with objective tests. Measurements of accommodative amplitude are best achieved with objective methods to stimulate and measure accommodation.

Evaluation of a satisfied bilateral scleral expansion band patient

PURPOSE

To measure accommodation subjectively and objectively in a satisfied bilateral scleral expansion band patient.

SETTING

University of Houston, College of Optometry, Houston, Texas, USA.

METHODS

One bilateral scleral expansion patient (age 50 years), 9 age-matched normal presbyopic control subjects (age range 48 to 52 years), and 1 normal control subject (age 27 years) participated. The scleral expansion patient had a complete eye examination, corneal topography, and wavefront measurements 19 months postoperatively. Accommodation was measured subjectively with the push-up technique, minus to blur, and dioptric range of clear vision. Accommodation was determined objectively by measuring the accommodative responses to negative lenses and pilocarpine 6% with a Hartinger coincidence refractometer and to real targets with a dynamic infrared optometer.

RESULTS

Distance and near acuity of 20/20 was achieved with +1.00 diopter (D) in the left eye, +0.50 D in the right eye, and a near add of +2.25 D. Corneal topography and ocular aberration measurements revealed no suggestion of optical multifocality. Subjective measurements resulted in accommodative amplitudes of 1.50 to 4.00 D, and objective measurements resulted in amplitudes of 0.25 to 1.33 D. The PowerRefractor showed an accommodative response of 0.50 D to stimuli of 1.00 to 4.00 D and strong pupillary constriction with accommodative effort compared with the control.

CONCLUSIONS

No increase in accommodative amplitude above normal age-matched controls was found. Patient satisfaction may have come from the high expectations this patient had for a positive surgery outcome.

Subjective and objective measurement of human accommodative amplitude

PURPOSE

To assess objective and subjective methods to measure accommodation in a young human population.

SETTING

Research laboratory, University of Houston, College of Optometry, Houston, Texas, USA.

METHODS

Accommodation was measured in the right eye of 15 young subjects (9 women and 6 men) whose ages ranged from 23 to 28 years and 1 36-year-old subject. The mean age of all subjects was 26 years. Accommodation was stimulated and measured with 4 techniques. Two subjective measures (focometer and minus-lens procedures) were used. Accommodation was also stimulated with minus-lens-induced blur and with pilocarpine 6% and measured objectively with a Hartinger coincidence refractometer.

RESULTS

Accommodative amplitudes measured with the 2 subjective methods agreed with each other but differed from the objectively measured amplitudes. Objectively measured accommodative amplitudes were similar in all subjects, with a mean of about 7.0 diopters. Accommodation stimulated with pilocarpine reached a maximum 33 minutes after administration. Individuals with light irides showed a stronger accommodative response to pilocarpine than subjects with dark irides.

CONCLUSIONS

Subjective measures of accommodation tend to overestimate true accommodative amplitude. Methods exist to measure accommodation objectively. These include stimulating accommodation with trial lenses or pilocarpine 6% and measuring the accommodative response with an objective optometer such as a Hartinger coincidence refractometer. Objective measures of accommodation should be used to determine whether accommodation can be restored in presbyopes.