Research ArticleCharacterization of Visual Symptomatology Associated withRefractive, Accommodative, and Binocular Anomalies

Pilar Cacho-Martnez, Mario Cant-Cerdn,Stela Carbonell-Bonete, and ngel Garca-Muoz

Departamento de Optica, Farmacologa y Anatoma, Universidad de Alicante, 03080 Alicante, Spain

Correspondence should be addressed to Pilar Cacho-Martnez; cacho@ua.es

Received 25 May 2015; Revised 20 July 2015; Accepted 26 July 2015

Academic Editor: Edward Manche

Copyright 2015 Pilar Cacho-Martnez et al. This is an open access article distributed under the Creative Commons AttributionLicense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properlycited.

Purpose. To characterize the symptomatology of refractive, accommodative, and nonstrabismic binocular dysfunctions and to assessthe association between dysfunctions and symptoms.Methods. 175 randomised university students were examined. Subjects weregiven a subjective visual examination with accommodative and binocular tests, evaluating their symptomatology. Accommodativeand binocular dysfunctions (AD, BD) were diagnosed according to the number of existing clinical signs: suspect AD or BD (onefundamental clinical sign), high suspect (one fundamental + 1 complementary clinical sign), and definite (one fundamental + 2 ormore complementary clinical signs). A logistic regression was conducted in order to determine whether there was an associationbetween dysfunctions and symptoms. Results. 78 subjects (44.6%) reported any kind of symptoms which were grouped into 18categories, with visual fatigue being themost frequent (20%of the overall complaints). Logistic regression adjusted by the presenceof an uncorrected refractive error showed no association between any grade of AD and symptoms. Subjects with BD had morelikelihood of having symptoms than without dysfunction group (OR = 3.35), being greater when only definite BD were considered(OR = 8.79). Conclusions. An uncorrected refractive error is a confusion factor when considering AD symptomatology. For BD, themore the number of clinical signs used the greater the likelihood suffering symptoms.

1. Introduction

In order to maintain a clear single image when readingor doing near work, both accommodative and convergencesystemsmust be adequate. If thesemechanisms fail, leading toaccommodative and/or vergence dysfunctions, subjects maycomplain of symptoms [1]. Several authors have reportedthat visual discomfort symptoms are prevalent among thosesubjects who have prolonged near work such as using acomputer or reading [27] and complaintsmay include visualfatigue, headache, blurred vision, diplopia, loss of concentra-tion when reading or doing near work, light sensitivity, orperceptual distortions involving letter movement and fading.

Scientific literature has revealed that accommodativeand/or vergence anomalies are commonly found in clinicalpractice [1, 819] and may show different symptoms betweenpatients [20, 21]. In this sense, several studies have focusedon the measurement of visual discomfort symptoms in

college students [2, 6, 2224]. Several authors have relatedthese dysfunctions to problems with reading or academicperformance [25, 26]. Others [1, 27] have reported thatthese visual symptoms may have a negative effect on schoolperformance or reading comprehension, even leading toavoidance of near work. It has also been shown [28] thatchildren with more visual symptoms have lower academicachievement than those with fewer visual symptoms. Andcurrent clinical trials about convergence insufficiency haveshown the improvement of academic behaviors [29] andthe decrease in performance-related symptoms [30] aftersuccessful treatment.

In any case, although in the scientific literature we can seethat the authors consider the presence of symptoms essentialto diagnose accommodative and/or binocular anomalies [26,3142], it has been shown in a scoping review [43] consideringarticles since the last 30 years that there is no consensus asto which symptoms should be considered in the diagnosis

Hindawi Publishing CorporationJournal of OphthalmologyVolume 2015, Article ID 895803, 13 pageshttp://dx.doi.org/10.1155/2015/895803

2 Journal of Ophthalmology

of each of these anomalies. In this sense, few symptomsare specific to each entity and many of them overlap whenconsidering an accommodative or binocular dysfunction, sothat this information may influence clinical management asit is difficult to associate a particular dysfunction with aparticular symptom. But also many of symptoms related toaccommodative and binocular disorders may not be differentfrom those related to other conditions as visual stress (orMeares-Irlen syndrome) [5, 44] or from those related touncorrected refractive anomalies [45].

Under these premises, the aim of this study was to char-acterize the symptomatology of refractive, accommodative,and nonstrabismic binocular dysfunctions in a randomisedsample of university students. A further aim was to assess theassociation between the various dysfunctions diagnosed andthe symptoms reported by the patients.

2. Materials and Methods

This study is part of a larger research which intended toanalyse the visual health of university students by means ofanalyzing the prevalence of accommodative and binoculardysfunctions of the university population of University ofAlicante and to characterize their symptoms. This paper isrelated to the characterization of symptoms.

We conducted a prospective study of a population sam-ple of university students from the University of Alicante,selected by means of simple random sampling of all studentsin all years of the degree courses taught at the Universityof Alicante. Simple random sampling was performed of the26,326 students attending the University of Alicante at thetime when the study was conducted. The randomization wasdone by the Computing Service of the University. Samplesize was calculated by assuming an overall prevalence ofaccommodative andnonstrabismic binocular dysfunctions of25% [11, 12, 18] with a confidence level of 95%, requiring a5% for the proportions estimation and a dropout rate of 20%,yielding a sample of 357 undergraduate and postgraduatestudents. As a requirement for obtaining data, students had tobe aged between 18 and 35 years old. Establishing the upperage limit of 35 years was to avoid including prepresbyopicsubjects in the study [46] who could bias the diagnosis of anaccommodative and nonstrabismic binocular disorder.

Participants were initially contacted via an email inform-ing them that they had been randomly selected from theuniversity student population to participate in this research.Due to the low response rate yielded by this approach, itwas decided to contact them by telephone to inform themof the study. Despite multiple attempts to contact studentsvia email and telephone, there were 177 students who finallyparticipated in the study, representing a response rate of49.6%. There were a variety of reasons for nonresponse:131 students did not respond either to emails or telephonecalls, 6 lived elsewhere, 21 did not want to participate, and20 students agreed to participate but did not attend theirappointment.

This study was conducted in accordance with the Decla-ration of Helsinki, and the Ethics Committee of Universityof Alicante approved the study. All subjects gave their

written informed consent once the nature of the study hadbeen explained. All of the 177 students were given a visualexamination, which besides a visual health examinationand a refractive examination also included specific tests todetermine the subjects accommodative and binocular status.

Visual examination consisted of the following proce-dures.

(i) Sociodemographic Data. Besides personal details, wealso collected academic data such as number of hoursof study per day and academic performance, this latterbeing calculated as the number of credits obtaineddivided by the number of credits studied in the lastacademic year.

(ii) Clinical History.Data were collected on the symptomsreported by the subjects. To this end, we did notuse a questionnaire but we used the categories ofsymptoms described by Garca-Munoz et al. [43] ina recent scoping review, in which they indicated thedifferent types of symptoms which may be associ-ated with accommodative and binocular dysfunction.We showed the list of 34 symptoms categories andpatients were asked if they were suffering any type ofthese symptoms related to their vision. Several symp-toms were fully explained to ensure understanding,for example, the symptom of visual fatigue (whichrefers specifically to symptoms described by patientssuch as tired eyes, eyestrain, or eye fatigue). Subjectswere considered to present a visual symptomatologywhen they reported one or more symptoms. For thepurpose of this analysis, a symptom was consideredpresent when it was either the patients main concernor if it occurred frequently, so that feeling the symp-tom once was not enough to render a positive answer.

(iii) Refractive Examination. This was performed bymeans of static retinoscopy and a subjective exam-ination. The subjective examination was performedby means of monocular fogging method with cross-cylinder followed by binocular balancing to a stan-dard endpoint ofmaximumplus for best visual acuity.Once the maximum plus value for best visual acuityhad been obtained, this result of the subjective exami-nationwas used as the baseline for all accommodativeand binocular tests.

(iv) Accommodative and Binocular Tests. The followingtests were performed. Phoria measurement was donewith cover test. Unilateral and alternate cover testmeasurements [4749] were done for distant andnear vision while the subject was instructed to fixateon a single letter of 20/30 visual acuity. Using aprism bar, the deviation value was midway betweenthe low and high neutral findings using an alternatecover test. Measurement of gradient AC/A ratio [50]was done using the cover test and 1.00D lenses.We calculated AC/A ratio [50]. Monocular estimatemethod (MEM) dynamic retinoscopy [51] at 40 cmwas donewith the result of the subjective exam placedin a trial frame and using trial lenses. Monocular

Journal of Ophthalmology 3

accommodative amplitudewasmeasured byDonderspush-up method [52] using a single 20/30 Snellenline target in free space. The target was slowly movedtowards the patient until reported blurring, and thedistance from this point to the spectacle plane wasthen recorded in diopters. Monocular and binocu-lar accommodative facility were measured followingthe procedure of Zellers et al. [53] at 40 cm andusing 2.00D flipper lenses and the 20/30 letterline on Vectogram 9 (Bernell) which includes asuppression control for the binocular measurement.Monocular accommodative facility was measured inthe same manner but without polarized glasses andwith the nonviewing eye occluded. Both monocularand binocular accommodative facility were measuredduring one minute and the cycles per minute (cpm)were recorded, evaluating if the patient had difficultyin focusing with plus or minus lenses. Near pointof convergence was measured in free space usingan accommodative target of 20/30 visual acuity at40 cm [54] and moving the target away from thesubject at a speed of approximately 1 to 2 cm persecond [55] until the break and recovery findings.Distance was calculated from the midsagittal planeof the patients head to the nearest half centimeter.Positive and negative relative accommodations weremeasured with plus and minus, respectively, behindthe phoropter, and using an accommodative targetof 20/30 visual acuity at 40 cm [50] until sustainedblur was detected. Positive and negative fusionalvergences were determined at far and near visionwith phoropters Risley prism (with a smooth gradualincrease in prism power) using an accommodativetarget of 20/30 visual acuity and performed accordingto the subjects type of heterophoria (for exophoriathe positive fusional vergence was measured first andthe negative fusional vergence was first performed foresophoria) [56, 57]. Vergence facility was measuredin free space using an accommodative target of 20/30visual acuity at 40 cm, with the prism combinationof 3 base-in/12 base-out [58, 59] and evaluatingif the patient had difficulty in fusing with the base-inor base-out prism. Determination of fusion was doneby means of the 4-dot Worth test [50] and stereopsiswas measured using graded circles of Randot SO-002test [60] in free space.

Once all these tests had been performed, the results wereanalysed in order to determine the existence of refractive,accommodative, and/or binocular dysfunctions. In order toavoid bias, diagnosis of each dysfunction was completedby two authors different to the person who performed thevisual examination, so that the persons who determined thediagnoses were masked to the symptoms.

The inclusion criteria for the study were applied tothese initial data and consisted of having a visual acuity of20/20 with the best correction, the absence strabismus oramblyopia, and any ocular or systemic disease that mightaffect the results. Two students presented an amblyopia and

strabismus so that the final number of subjects included in thestudy was 175, of whom 59 were male (33.7%) and 116 female(66.3%), with a mean age of 22.90 3.96 years.

Patientswere diagnosedwith refractive dysfunctionwhena difference was detected between their habitual refractionand their subjective examination results obtained in thisstudy. The clinical criteria applied to establish this differencewere the following:

(i) A less negative subjective examination result than thehabitual refraction; in other words, the patient wasovercorrected for myopia (equal to or greater than0.50D).

(ii) Changes in the sphere or cylinder equal to or greaterthan 0.50D, with which visual acuity was increasedby at least one line with the new refraction.

Thus, subjects were classified into two refractive categories asfollows:

(i) In subjects with an uncorrected refractive error, thepatient used a prescription different to that indicatedby the subjective examination, or the patient did notuse a prescription but needed it.

(ii) In subjects without an uncorrected refractive error,the patients habitual refraction was satisfactory.

Accommodative dysfunctions (AD) and binocular dysfunc-tions (BD) were diagnosed in accordance with the criteriadescribed in the literature [42, 50]. However, since thereis no enough scientific evidence to support the use ofany given diagnostic criterion to accurately define eachdysfunction [21], we decided to classify dysfunctions on thebasis of the number of clinical signs associated with eachdysfunction, classifying the signs that could be associatedwith each dysfunction as fundamental and complementary.The classification employed was as follows:

(i) Suspect AD or BD: one fundamental clinical sign.(ii) High suspect AD or BD: one fundamental clinical

sign + 1 complementary clinical sign.(iii) Definite AD or BD: one fundamental clinical sign + 2

or more complementary clinical signs.

Table 1 gives the fundamental and complementary clinicalsigns used in this study to diagnose each accommodativeand binocular dysfunction. For binocular conditions weused the classification made by Scheiman and Wick inwhich the calculated AC/A ratio is considered to diagnose aparticular binocular condition. Following this classificationhigh AC/A ratio conditions are convergence excess anddivergence excess, low AC/A ratio includes convergenceinsufficiency and divergence insufficiency, and normal AC/Aratio conditions refer to fusional vergence dysfunction (alsoknown as binocular instability [61]), basic esophoria, andbasic exophoria. With these considerations, patients weregrouped into different groups: patients with accommodativedysfunctions (AD), binocular dysfunctions (BD), and bothaccommodative and binocular anomalies (AD + BD).

4 Journal of Ophthalmology

Table 1: Clinical signs used in the study for diagnosing accommodative and binocular anomalies (AA: accommodative amplitude;MAF/BAF:monocular/binocular accommodative facility; MEM: monocular estimate method; PRA/NRA: positive/negative relative accommodation;PFV/NFV: positive/negative fusional vergence; NPC: near point of convergence; VF: vergence facility; : prism diopters; D: diopters; cpm:cycles per minute; BO: base-out; BI: base-in).

Dysfunction Fundamental sign Complementary signAccommodative dysfunctions

Accommodative insufficiency Reduced AA: 2.00D 0.75DPRA < 1.25D

Accommodative excess MAF < 6 cpm with +2.00D lenses

PRA 3.50DBAF < 6 cpm with +2.00D lenses

MEM < 0.25DNRA < 1.50D

Accommodative infacility MAF < 6 cpm with 2.00D lensesBAF < 3 cpm with 2.00D lenses

PRA < 1.25DNRA < 1.50D

Binocular dysfunctions

Convergence insufficiency Significant exophoria at near vision (6), greater thanfar vision

PFV at near 11/14/3NPC 6 cm

VF < 13,4 cpm with 12 base-out prismBAF < 3 cpm with +2.00D lenses

MEM < 0.25DNRA < 1.50D

Convergence excess Significant esophoria at near vision (1), greater thanfar vision

NFV at near 8/16/7VF < 13.4 cpm with 3 base-in prismBAF < 3 cpm with 2.00D lenses

MEM > 0.75DPRA < 1.25D

Divergence excess Significant exophoria at far vision (4), greater thannear vision (the difference must be >5)

PFV at far 4/10/5PFV at near 11/14/3

NPC 6 cmVF < 13,4 cpm with 12 base-out prism

BAF < 3 cpm with +2.00D lensesMEM < 0.25DNRA < 1.50D

Basic esophoriaSignificant esophoria at far and near vision of equalamount (deviations within 5 of one another areconsidered equal)

NFV at far /3/1 and at near 8/16/7

VF < 13.4 cpm with 3 base-in prismBAF < 3 cpm with 2.00D lenses

MEM > 0.75DPRA < 1.25D

Journal of Ophthalmology 5

Table 1: Continued.

Dysfunction Fundamental sign Complementary sign

Basic exophoriaSignificant exophoria at far and near vision of equalamount (deviations within 5 of one another areconsidered equal)

PFV at far 4/10/5 and at near 11/14/3

NPC 6 cmVF < 13,4 cpm with 12 base-out prism

BAF < 3 cpm with +2.00D lensesMEM < 0.25DNRA < 1.50D

Fusional vergence dysfunctionPFV and NFV reduced at far and near vision or VF