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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 14  |  Issue : 1  |  Page : 48-54

Ophthalmic anthropometry versus spectacle frame measurements: Is spectacle fit in children compromised?


Department of Optometry, College of Allied Health Sciences, Sri Ramachandra Institute of Higher Education and Research, Chennai, Tamil Nadu, India

Date of Submission03-Jan-2022
Date of Decision05-Feb-2022
Date of Acceptance08-Feb-2022
Date of Web Publication01-Mar-2022

Correspondence Address:
Samuel Livingstone Kumaran
Department of Optometry, Sri Ramachandra Institute of Higher Education and Research, Chennai - 600 116, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ajprhc.ajprhc_2_22

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  Abstract 


Purpose: Refractive errors among children are on the rise and more children are wearing spectacle correction. Selecting an appropriate frame that conforms to the child's developing facial features is vital for comfortable spectacle wear. This study aimed to analyze the relationship between the facial and frame measurements in spectacle-wearing children in southern India. Materials and Methods: This observational study included spectacle-wearing children aged 5–17 years. Participants were enrolled from the Paediatric Outpatient Department of a tertiary care hospital and across various schools in southern India. The facial and frame measurements such as pupillary distance, crest height (CH), bridge projection, apical radius, distance between rims at 10 mm and 15 mm, frontal angle (FA), splay angle, front to bend, head width, temple width (TW), angle of side and downward angle of drop were measured using Rees Fairbanks facial gauge, head and TW caliper and Association of British dispensing opticians frame rule. Results: Hundred and four children participated in the study. Statistically significant differences (P < 0.01, Wilcoxon signed-rank test) were observed between all facial and frame measurements such as CH, splay and FAs. Bland–Altman plots indicated large mean differences and wide limits of agreement between facial and frame measurements. Conclusion: Our study shows a large discrepancy between children's facial measurements and corresponding spectacle frame measurements. Many children were wearing reduced version of adult frames. This study highlights the need for dispensing age-appropriate spectacle frames for children. This may have implications for improved spectacle uptake and compliance.

Keywords: Children, frame measurement, ophthalmic anthropometry, plastic frame, spectacle fit


How to cite this article:
Kumaran SL, Periakaruppan SP. Ophthalmic anthropometry versus spectacle frame measurements: Is spectacle fit in children compromised?. Asian J Pharm Res Health Care 2022;14:48-54

How to cite this URL:
Kumaran SL, Periakaruppan SP. Ophthalmic anthropometry versus spectacle frame measurements: Is spectacle fit in children compromised?. Asian J Pharm Res Health Care [serial online] 2022 [cited 2022 May 25];14:48-54. Available from: http://www.ajprhc.com/text.asp?2022/14/1/48/338791




  Introduction Top


Anthropometry is a branch of science that studies human body measurements.[1] “Anthropos” in Greek means “man” and “mentron” means “measure.”[2] Ophthalmic anthropometry concerns facial and ocular measurements. Ocular anthropometric measurements play an important role in designing and constructing spectacle frames.[1],[3],[4] For a frame to fit well, the frame parts such as the nasal bridge and temples should align with the anatomical structure of the individual's face.[5],[6],[7],[8] This means that the facial and frame measurements must correspond. An improper frame fit may cause visual consequences (e.g., blurred vision), asthenopia due to the prismatic effects of decentration and poor compliance to spectacle wear.[3],[6],[8] In addition, ill-fit frames may be uncomfortable (e.g., tight near ears), inconvenient (e.g., sliding down the nose) and may cause abrasion of the skin.[4],[8],[9],[10]

The anatomical structures of the face vary among individuals of various ethnic backgrounds, gender, and age groups.[11],[12],[13],[14] Normative data of facial measurements in each population become imperative as the facial structures change gradually in developing children. This means, one array of frame size and dimension would not fit all. For instance, children have flatter nasal bridges and smaller head circumference compared to adults and thus require frames with greater splay and FAs and smaller temple and head width (HW).[9],[15] Manufacturers, optical retailers, and practitioners have shown only slight attention to differences in facial measurements between adults and children.[16] It can be seen in clinical practice that many children wear scaled-down sizes (small versions) of adult frames that do not align with their facial features.[9],[17]

This is critical because: (1) Children wearing spectacle as a means of refractive correction treatment are increasing in number,[18],[19] (2) Proper frame selection and fit is necessary to avoid irritation, malformation of developing ears and nose,[9] (3) Children's skin is soft (sensitive) and can tolerate only a considerable amount of pressure caused by the frame,[9],[10],[20] (4) Children may not be able to explain the concerns related to their spectacle fit like spectacle sag (drooping of spectacle down the nose) because of the flat nasal bridge, eye-lashes smearing against the back surface of an ophthalmic lens,[9],[10],[16] and (5) Many children use the regular bridge or fixed pad plastic frames which cannot be adjusted to their facial features, especially nasal bridge, unlike pad-on arm frames.[4],[8],[20]

In light of these considerations, we aimed to study the relationship between facial and frame measurements in a sample of spectacle-wearing children in southern India.


  Materials and Methods Top


The study was approved by the Institutional Ethics Committee (REF: CSP/NOV/81/362) and adhered to the tenets of the Declaration of Helsinki.

Participants

A total of 104 children between the age group of 5 and 17 years who were spectacle users (using plastic frames) were eligible to take part in the study. Fifteen participants were enrolled from the Paediatric Outpatient Department of a tertiary care hospital and eighty-nine participants were enrolled from various schools in southern India. The sample was recruited based on nonprobabilistic purposive sampling. Children who used pad on arms frames, temple style apart from drop end, children with facial asymmetry, children with special needs or disability, noncooperative children and those with any anterior eye infection (e.g., conjunctivitis) at the time of measurement were excluded from the study.

Procedure

All potential participants and their parents were given a written information sheet in both regional language and English. Signed consent from the parent and assent from the participant was obtained. Participation was voluntary. The age and gender of the participants were noted. Participants were seated comfortably in a well-lit room with their spectacle removed for the study. A single examiner measured their facial measurements using Rees Fairbanks facial gauge, head and temple width (TW) caliper followed by frame measurements using the Association of British dispensing opticians frame rule. The facial and frame measurements: Pupillary distance, crest height (CH), bridge projection, apical radius (AR), distance between rims (DBR) at 10 mm and 15 mm, frontal angle (FA), splay angle (SA), front to bend (FTB), HW, (TW), angle of side, and downward angle of drop (DOAD) were noted. The respective facial and frame measurements are depicted in [Figure 1] and [Figure 2].
Figure 1: Facial measurements representation. Frontal view (a and b), Profile view (c) and Aerial view (d) AR: Apical radius, AS: Angle of side, BR: Bridge projection, CH: Crest height, DBR: Distance between rims, DOAD: Downward angle of drop, FA: Frontal angle, FTB: Front to bend, HW: Head width, IPD: Inter pupillary distance, LS: Line of side, TW: Temple width, SA: Splay angle, SP: Spectacle plane

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Figure 2: Frame measurements representation. Frontal view (a), Profile view (b) and Aerial view (c) AR: Apical radius, AS: Angle of side, BR: Bridge projection, CH: Crest height, DBC: Distance between centers, DBR: Distance between rims, DOAD: Downward angle of drop, FA: Frontal angle, FTB: Front to bend, GC: Geometric center, HCL: Horizontal center line, HW: Head width, LS: Line of side, TW: Temple width, SA: Splay angle

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Statistical analysis

The collected data were analyzed with a Statistical Package for the Social Sciences (SPSS) 23.0 version (IBM Corporation, New York, USA). Shapiro Wilk's test revealed that the data were not normally distributed. Median, interquartile range (IQR), and Z-value were estimated for facial and frame measurements. Nonparametric Wilcoxon signed-rank test was used to test the null hypothesis, that there are no differences between facial and corresponding frame measurements. The P < 0.01 was considered statistically significant. Bland–Altman graphs were plotted to assess the agreement between the facial and frame measurements.


  Results Top


Hundred and four children (52 males and 52 females) participated in the study. Their mean age (standard deviation) was 11 (3) years and the range was 5–17 years. Their refractive error profile was classified as myopia (n [%] = 65 [62.5)), hyperopia (n [%] = 5 [4.8]), and astigmatism (n [%] = 34 [32.7)). The median, IQR, and Z-value of facial and frame measurements are provided in [Table 1]. Statistically significant differences (P < 0.01) were observed between all facial and corresponding frame measurements using Wilcoxon signed-rank test [Table 1].
Table 1: Pairwise comparison of facial and frame measurements

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Bland–Altman plots were used to estimate the agreement between the facial and frame measurements. These plots show the mean difference between the facial and frame measurements with 95% limits of agreement. The values are presented in [Table 2]. The large mean differences and wide limits of agreement indicate poor agreement between the facial and frame measurements. Large variations were noted in measurements such as HW, splay, and FAs.
Table 2: Mean difference and limits of agreement between facial and frame measurements

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Spectacle fit was assessed objectively and categorized into small fit (frame measurement less than facial measurement), large fit (frame measurement greater than facial measurement), and optimal fit (frame measurement equal to facial measurement) represented in [Table 3]. Larger fit was noted for measurements concerning the bridge area of the spectacle such as, CH (n [%] = 86 [82.7)) and bridge projection (n [%] = 104 [100)) and smaller fit was noted for measurements such FAs (n [%] = 99 [95.2)) and SA s (n [%] = 92 [88.5)). These findings indicate that the measurements concerning the frame bridge was not suitable for the children's nasal area (which is crucial in a plastic frame). Similarly, TW which directly relates to the frontal frame width was found to be larger (n [%] = 59 [56.7)). This infers, more than half of the study sample were using larger frame eye size. DOAD frame measurement was lesser than its facial counterpart suggesting less spectacle grip behind the ears.
Table 3: Objective spectacle fit assessment

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  Discussion Top


To the best of our knowledge, this is the first study that evaluated the spectacle fit objectively in a pediatric population using ocular anthropometric and frame measurements. Statistically significant differences and poor agreement were noted between all thirteen facial and corresponding frame measurements in our study sample. Major difference was observed in HW, splay, and FAs. The results of our study suggest children were using frames which did not correspond to their facial measurements. These frames were merely small versions of adult frames (frame size reduced proportionately without accounting for differences in facial features).

In contrast to an adult's frame, a children's frame should have a smaller CH, bridge projection, and larger frontal and SAs.[9],[15],[16] However, our study noted that this was just the opposite in our sample; larger frame CH, bridge projection, and a smaller splay and FAs were evident. DBR and AR were also significantly smaller than corresponding facial measurements. A previous study has reported that around 67% of children were wearing frames with improper nasal bridge fitting.[8] Regular bridge plastic frames will accurately fit only if the bridge area of the frame corresponds to the width and shape of the developing nasal bridge.[21] For instance, nearly 83% of children in our study were wearing frames with larger CH among which 58% of children's frame had CH >2 mm when compared with their facial measurements. These larger CHs would naturally position the frame lower on the face thereby hindering the child from viewing through the optical centers of the ophthalmic lenses which causes the prismatic effect.[9],[15],[16] This finding substantiates the result of a previous qualitative study which reported children complaining of frames sliding down their nose.[10] Hence, this sort of frame fit in children with moderate-to-high refractive errors are likely to cause more visual disturbances. We also observed, 92% of children's frames had narrower SA and 99% of frames had smaller FA. These reduced angles are bound to pressurize the developing nasal structures and be detrimental to growth.[9],[22]

Ideally, the facial and frame TW s should be equal to conform to the small face of the child.[8],[9],[20] TW is one of the key factors while selecting appropriate frames for children.[10] However, 57% of children in our study were wearing frames with larger temple (frontal) width which indicates a larger frame eye size and a larger frame front. Similarly, the frame FTB was larger than the facial measurement, representing a longer frame temple (side) length. It should be noted that these two measurements are meant to be critical dimensions for frame measurements while selecting a frame.[1],[10]

The findings of our study emphasize that spectacle frame worn by the children failed to mimic their facial contours. Discrepancies between the facial and frame measurements observed in our study could be due to the lack of normative anthropometry data in many countries.[4],[23] The lack of such standards may be a reason why manufacturers design reduced versions of adult spectacle frames for children.[10],[22] The other reason could be a lack of awareness among eye care practitioners and opticians about the importance of taking facial measurements and relating them with the frame measurements during frame selection.[24] The possibility of dispensing customized frame designs (frames made according to individual facial parameters) is also not well known due to the research gap.[10] It was surprising that even few of the adjustable frame measurements in our study sample were ignored (e.g., DOAD).[9],[10] This could be due to negligence or lack of professional expertise.[6],[8]

Spectacle frame which does not fit the children may be uncomfortable to wear and hence pose a barrier for spectacle compliance.[8] Several studies on spectacle compliance have reported uncomfortable spectacles as reasons for noncompliance in children.[25],[26] It is thus important that eye care practitioners and dispensing opticians recognize the implications of improper spectacle fit on compliance. Considering our study outcomes, eye care practitioners can select a plastic frame by assessing the facial measurements such as CH, bridge projection, splay, and FA as these are nonadjustable in a regular bridge plastic frame. As standard Paediatric dispensing practice recommends a plastic frame which suits a child's low nasal bridge and suggests strong material which resists any deformity, it becomes vital for every practitioner to consider this.[10] Furthermore, pediatric dispensing should be given utmost importance in terms of measuring facial and frame measurements to enhance the standard of dispensing practice.

This study has some limitations. The study only assessed the spectacle fit in children wearing plastic frames with the regular bridge. Those using metal frames were excluded. Metal frames are not widely used and recommended for children due to the possibility of allergic reactions from metals such as Nickel.[8],[10],[27] However, some children may still use metal frames and they were not considered in the study. The sample size of our study is small and is not representative of the population. It should also be noted that the HW and DOAD could have been affected by wear and tear over time and mishandling. Hence. the age of the existing spectacle, rectification of misaligned spectacle sides, and the replacement schedule are valid to be investigated in upcoming studies. Although our study has reported objective assessment of spectacle fit, we did not evaluate the subjective perception of the fit (loose/tight) and any associated inconvenience from the child's perspective. Understanding the influence of socioeconomic status during frame selection becomes imperative. These aspects would be considered as a scope for future evaluation.


  Conclusion Top


Our study indicates a large discrepancy between children's facial and frame measurements. Awareness among eye care practitioners and dispensing opticians about the importance of anthropometric measurements and collection of normative anthropometry data to aid manufacturers design appropriate pediatric frames can help in bridging the gap. This may have implications for improved spectacle uptake and compliance.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

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    Tables

  [Table 1], [Table 2], [Table 3]



 

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