Light Protection Performance of Textile Phototherapy

Textile Research Journal Article

Textile Research Journal Vol 0(0): 1–12 DOI: 10.1177/0040517509349785 © The Author(s), 2009. Reprints and permissions:Figures 1, 7, 10 appear in color online: http://trj.sagepub.com http://www.sagepub.co.uk/journalsPermissions.nav

Light Protection Performance of Textile Phototherapy Eye-patch Protectors for Jaundiced Infants

Yong-mei Deng, Kit-lun Yick1 and Yi-lin KwokInstitute of Textiles and Clothing, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong

Siu-chun WongDepartment of Paediatrics and Adolescent Medicine, The Hong Kong Queen Mary Hospital, Hong Kong

Long WuInstitute of Textiles and Clothing, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong

Neonatal jaundice is the most common condition found innewborns. About 50–60% of full-term infants and 80% ofpre-term infants will have jaundice during the first week oftheir life because their livers are too immature to remove awaste product called bilirubin from the blood [1-3]. Typi-cally, a naked infant is exposed to a fluorescent light for

several days. As the light is absorbed by the infant’s skin,the bilirubin in the infant’s body is changed into another

Abstract In this paper we report on an experi-mental investigation into the performance of tex-tile eye-patch protectors for jaundiced infantsnursed in neonatal units which are routinely usedto protect their eyes from strong light during pho-totherapy. With the view of practical application,the main factors affecting the light protection per-formance of an eye-patch protector, including thelight transmission level of the fabric, the irradiancelevel, location of the light unit, the head directionsof the infant, and the design components of eye-patch protectors, were examined in a simulatedclinical environment of phototherapy light treat-ment. It was found that textile eye-patch protectorsare able to shield the strong phototherapy lighteffectively. However, the light protection perform-ance of the eye-patch protector is greatly affectedby its fabrication and the level of the eye-patch dis-placement. Results from the current work con-firmed that fabric constructional parameters andstructure both had a significant impact on photo-therapy light protection. Fabric that was black incolor could give effective protection from differentlight sources. Results also revealed that the selec-tion of light units, the positions and the head direc-tions of the infant, and the infant’s distance fromthe light unit are major factors affecting the irradi-ance level and the efficacy of the treatment.Uniquely, non-linear regression models have beenapplied and demonstrated to predict the safety per-formance of eye-patch protectors.

Key words eye-patch protector, phototherapytreatment, light protection performance

1 Corresponding author. Tel: +852 2766 6551; Fax: +852 27731432; Email: [email protected]

Textile Research Journal OnlineFirst, published on October 15, 2009 as doi:10.1177/0040517509349785

2 Textile Research Journal 0(0)TRJTRJ

form of bilirubin that can be easily excreted in stools orurine. The literature indicates that the wavelength and theirradiance of light are two essential parameters of photo-therapy light affecting the required dosage for jaundicetreatment [4]. Dicken et al. [4] also revealed that the mostefficacious wavelength range for photo-degradation ofbilirubin is between 450 and 460 nm (i.e. blue light). How-ever, a study of animals revealed that intense blue fluores-cent light can damage a newborn piglet’s retinas which aredeveloped in a way similar to human infants [5]. Therefore,eye shields such as eye-patch protectors (EPs) are rou-tinely used in neonatal units routinely to protect theinfants’ eyes from strong light during phototherapy.

The application of EPs to phototherapy treatment has ahistory of over 40 years. Various EPs have been developedand applied to phototherapy [6–8]. Since the essentialfunction of an EP is photo-protection, the protection givenby an EP must be evaluated. Much research has focused onevaluating light transmittance through EPs [9–11]. Robin-son [6] and Porat et al. [7] emphasized that the evaluationof EPs should be conducted in a clinical light simulatingenvironment. A spectroradiometer was used to measurethe spectral distribution of irradiance which is an effectiveindex for the dose of phototherapy in clinical practice.Porat et al. [7] and Davies [8] also used a luxmeter (orlightmeter) to measure illuminance and evaluate the inten-sity of incident light and wavelengths. As there are medicalethics restrictions on testing on the living human body,most of the research studies focused on the light transmis-sion characteristics of the EP’s materials [6–11]. Since theexperiments did not mimic the clinical light conditions ofphototherapy treatment, the performance of eye protec-tion offered by EPs is still unknown. Some researchers alsonoticed that the transmission characteristic of materials isonly one of the important factors for photo-protection ofEPs. However, measurements taking other influencing fac-tors into account, such as fitting and displacement, are stillvery scarce.

Experimental Work

Fabric SamplesKeybus et al.’s work [12] revealed that almost all structuralindices of textile materials, especially fabric color, weight,and structure, have a direct impact on the transmittance ofvisible radiation and the light protection of fabric. In thiswork, the effects of fabric structural indices on fabric lighttransmittance during phototherapy treatment were exam-ined. As suggested by the medical staff of neonatal inten-sive care unit and special care baby unit of a local hospital,cotton and/or cotton blended single jersey fabrics were firstchosen for light protection performance examination dueto their excellent comfort and softness for newborn infants.Blue light in the wavelength range of 400–500 nm andwhite light in the wavelength range of 350–800 nm, both ofwhich are usually used in phototherapy treatment wereused. The light transmittance of three single jersey fabricsamples of various thicknesses and weights under the con-dition of no fabric extension were measured by a Cary UV/Visible spectrophotometer using the ASTM 183-2004method. Since fabric extension has a major effect on lighttransmission [13] and knitted fabrics have an inherentcapacity to extend, while woven fabrics do not, test resultsin light transmittance were compared against a simplewoven fabric. Samples are made from 100% cotton or cot-ton/spandex blended, some of their structures and contentsare similar to the EP fabrics used. Specifications of the fab-ric samples are presented in Table 1. In this experiment,the light transmittance of different color fabrics was alsoexamined. Six fabric samples of the same structure of Fab-ric D in white, yellow, green, blue, red, and black colorswere used.

Table 1 Specifications of the fabric samples.

Fabric No.

Content Color Construction Weight (g/m2)

Thickness under pressure of 200 Pa

(mm)

Yarn count Fabric sett (per cm)

Warp (tex)

Weft (tex)

Ends or wale

Picks or course

A 100% cotton White Single jersey 100.8 0.54 14.5 15.9 17.8

B 95/5 cotton/Spandex

White Single jersey 207.6 0.81 14.5 18.2 27.2

C 95/5 cotton/Spandex

White Single jersey 258.0 1.19 18.0 15.9 24.4

D 96/4 cotton/Spandex

White Woven (1/2 twill)

240.8 0.50 36.9 36.9 44.4 15.7

Light Protection Performance of Textile Phototherapy Eye-patch Protectors Y.-mei Deng et al. 3 TRJ

Data Acquisition Instrumentation for Light Protection Performance Evaluation in a Simulated Clinical EnvironmentTo evaluate the level of light exposure and protection ofEP in phototherapy treatment, a data acquisition instru-mentation for indices of light, including spectral irradianceand illuminance, was developed. The instrument consistsof an infant’s head model, a spectroradiometer with asmall size diffuser installed at manikin’s eye location and asupport stand, see Figure 1. A gear with a 15° interval wasdesigned at the bottom of the head model to adjust theangle of the head model so as to simulate the head direc-tions of the infants. An International Light® ILT 900 wide-band rapid portable spectroradiometer with a fiberoptic/mini waterproof cosine diffuser having a diameter of 14mm was used for investigating the spectral distribution oflight irradiance. The diffuser of the spectroradiometer was

attached to the eye position in the head model to examinethe level of light exposure to the infants’ eyes.

A simulated clinical environment was set up in the hos-pital to mimic a clinical phototherapy environment withvarious assemblies of light source (i.e. light units, loca-tions, directions and distances). A Medela® fluorescentphototherapy unit and an Ohmeda® halogen spotlight unitwere used as light sources in this experiment, see Figure 2.The light units were located at the top of a standard AirShields Isolette® Incubator. The diffuser of the spectrora-diometer used for the detection of light irradiance waslocated in six different locations to simulate the positionsof the infants, see Figure 3. In view of the head directionsof the infants, the light irradiance at seven different anglesfrom 0° to 180° was measured, see Figure 4. All experi-ments were conducted with the indoor artificial lightingmaintained over 24 hours in the neonatal unit. The meas-uring range of the spectroradiometer was regulated as the

Figure 1 Instrumentation for lightprotection performance evaluation.

Figure 2 Light units at simulated clinical environment: (a) fluorescent light; (b) halogen spotlight.


visible light wavelength of 350–800 nm because visible lightmay cause retinal damage and a variable degree of visualloss to infants [4].

EP SamplesTwo EPs currently used in the neonatal unit of a local hos-pital in Hong Kong were selected for the experiment: thePosey® eye-patch protector (EP1) and the Biliband® eye-patch protector (EP2). A newly developed EP (EP3) wasalso evaluated in this study [14, 15]. Each EP included twopanels: one eye-patch panel used to protect infant’s eyesfrom strong light and one fastening panel used to fix theeye-patch panel to an optimum position on the infant’shead, which varied in style, material composition and func-tion to the other samples. The schematic diagrams of thesamples are presented in Figure 5 and their fabrication ofeye-patch panel is presented in Table 2. It is noteworthythat the eye-patch panel is a composite of a three-layerstructure with an inner layer single jersey fabric, a middlelayer of foam or woven material, and an outer layer of knit-ted fabric.

Prediction of Safety Performance using Non-linear Regression MethodTo predict the safety performance of EP in relation to its dis-placement, non-linear regression models using the Gauss–Newton algorithm are used to calculate the light protectionperformance of EP [16]. As the diffuser of the spectroradi-ometer was shielded by the three EPs, the light illuminancevalues with distance and direction variations were firstlystandardized using Equations (1), (2) and (3) below andBartlett’s test was applied for significance of variables:

Figure 3 Locations of diffuser for detection of light irradi-ance (unit: millimeters).

Figure 4 Directions of diffuser for detection of light irra-diance (unit: degrees).

Table 2 Fabrication of the eye-patch panels of EP samples.

Sample code

Composite Structure with three layers of material for each sample

Construction Content/structure Color Weight of EP panel at three-layer composite

structure (g/m2)

Thickness of EP panel under pressure

of 200 Pa (mm)

EP1 (Posey®)

Inner-layer Cotton (single jersey) White

365.5 3.75Middle-layer Polyurethane/polyester blended (foam) Gray

Outer-layer Nylon (tricot) White

EP2 (Biliband®)

Inner-layer Cotton (single jersey) Blue

542.9 2.36Middle-layer Polyurethane/polyester (foam) White

Outer-layer Cotton (single jersey) Black

EP3 (new design)

Inner-layer Cotton/Modal® blended (single jersey) White

401.4 1.30Middle-layer Cotton (woven) Black

Outer-layer Cotton (single jersey) Pink


(1)

where zi is calculated as the standardized data of independ-ent variable; xi is the corresponding independent variable;

and s are the mean and standard deviation of the inde-pendent variable which are calculated as follows:

(2)

(3)

where n is the number of samples. The data was then cal-culated using Table Curve 3D by non-linear regression.The fitting procedure is based on the Gauss EliminationAlgorithm.

zixi x–

s------------=

Figure 5 Schematic diagrams of the EP samples.

x

x 1n--- xi∑=

s 1n--- xi x–( )

2∑=


Results and Discussion

Effects of Fabric on Light Protection Performance of EP

The light transmittance results obtained from the fourstudied fabrics at the wavelength range of 350–800 nm arepresented in Figure 6. Amongst the three single jersey fab-rics (A, B and C), Fabric C was the heaviest and thickestfabric sample and resulted in the lowest values of lighttransmittance and the best light protection during photo-therapy treatment. Fabric weight and thickness had a sig-nificant impact on the value of light transmittance in boththe wavelength ranges of 400–500 nm (blue light) and 350–800 nm (white light). This could also be attributed to thevariations in yarn fineness and density of the fabric sam-ples [17, 18]. To some extent, the woven structure of FabricD may be more desirable for EP development than singlejersey structures since it also gave low values of light trans-mittance, even though its thickness is only half that of Fab-ric C. While one woven fabric was investigated in thecurrent study, other processing variables differed amongfabric types and were not controlled; further examinationon woven samples for phototherapy light transmittance isrecommended for EP development. For example, in the lit-erature it has been reported that satin weave offered betterultraviolet protection than twill and plain weaves since it

can achieve higher warp/weft density than with twill andplain weaves, so the macropores are smaller and ultravioletradiation has less free space to pass through than in twill orplain weaves [17].

Results of the six fabrics of the same structure but dif-ferent colors are presented in Figure 7. It can be seen thatthe different colors of the fabrics had a major effect onlight transmittance at the wavelength range of 350–800 nm.The results revealed that white fabric had the highest val-ues of light transmittance, while fabrics in yellow, green,blue, and red had low values of light transmittance in thewavelength range of 400–500 nm, but high values of lighttransmittance in the wavelength range of 550–800 nm.Black fabric, however, had the lowest values of light trans-mittance (with the mean value of 0.008%) and offer thebest light protection from both blue and white lights duringphototherapy treatment.

It is noteworthy that the light transmission characteris-tic of materials would also be affected by several fabricparameters such as yarn structure, fabric texture, fabricextensibility, finishing treatment, etc. [13, 17, 18]. The lighttransmittance of knitted fabrics may also increase readilywhen fabrics were stretched at use and the light protectionperformance of the textile EPs would show more complexrules. Thus, the conclusion drawn from this experimentmay be only suitable for single jersey and/or simple wovenfabrics without tension applied such as the fabric samplesused in this study. Owing to the above-mentioned draw-

Figure 6 Light transmittance offabrics in different structures andweights.


backs, the dimensions of the final EPs, the size or head cir-cumference of the infant and the finishing treatment of theprotecting fabric are not considered when examining thelight protection performance of the EPs.

Influence of Light Conditions and Settings of Phototherapy Treatment When considering the end-use of the textile EP, the influ-ence of light conditions and settings of phototherapy treat-ment are examined. As suggested by the medical staff,three light settings for the fluorescent light unit and halo-gen light unit frequently used in hospital were adopted inthis work. Owing to the invasive medical treatment and/orphysiological needs, infants move from time to time. It is apersistent problem that the EPs are displaced very quickly.Therefore, the light environment of various typical loca-tions which mimic the sleeping positions and head direc-tions of the infants during phototherapy treatment was alsomeasured.

Even though the optimum light quality for the mostefficient use of phototherapy is still under active investiga-tion and discussion, the yellow bilirubin absorption spec-trum in plasma and buffer/human serum albumin has beenwell established. The most effective light sources fordegrading bilirubin in the skin are those that emit light in arelatively narrow wavelength range of 400–500 nm andcenter around a peak of 460±10 nm, which closely matchesthe bilirubin absorption spectrum [19, 20]. In this respect,the spectral distributions of light irradiance with varioussettings of light conditions were measured, and the total

irradiance (in wavelength ranges of 350–800 nm and 400–500 nm) and the total illuminance (of various settings oflight conditions typically used in hospital) were calculatedand are summarized in Table 3.

Types of light unitFigure 8 presents the effects of the fluorescent light withfour blue tubes (4B), with two white and two blue tubes(2W2B) and the halogen light (H) with the diffuser locatedat point E of the mattress, which is the typical head loca-tion of infants. Results indicated that light irradiance fromthe fluorescent light unit with 4B was higher than that with2W2B in the wavelength range of 390–530 nm, but lowerthan that with 2W2B in other wavelength ranges. The peakof spectral irradiance of halogen light was at 640 nmapproximately and reduced slowly from the peak. Resultsdemonstrated that fluorescent light with 4B is the mosteffective light source for jaundice treatment amongst thethree light units studied. In this experiment, halogen lightis less effective for bilirubin reduction since only about15% of halogen light irradiance was in the wavelengthrange of 400–500 nm. The strong light illuminance of halo-gen light (65,270 lux), far exceeding the safety illuminancemagnitude and 10 times higher than that of the fluorescentlight settings, may also result in a higher degree of poten-tial retina damage to infants.

Figure 7 Light transmittance offabrics in different colors.


Location of the DiffuserWhen the 4B fluorescent light unit was put over the centerof the incubator with a vertical distance of 350 mmbetween the unit and the diffuser, the spectral distributionof light irradiance was measured at points A, B, C, D, E,and F, illustrating the moving range of the infant’s head onthe mattress. As shown in Table 3, the values of total irra-diance obtained from different positions on the mattresswere different obviously. The further the distancebetween the diffuser and the light unit is, the smaller thevalues of total irradiance and illuminance. The highestvalues of light irradiance within the wavelength of 400–500 nm (56 W/m2) and illuminance (6365 lux) was obtainedat point F, as it has the shortest distance from the fluores-cent light unit amongst the six locations studied. Point Aresulted in the lowest values of light irradiance (8.6 W/m2

within 400–500 nm) and illuminance (1466 lux). It is obvi-ous that the position of the diffuser and its distance fromthe light unit are major factors affecting light irradianceand light illuminance.

Directions of Diffuser

The spectral distribution of light irradiance was also meas-ured in directions of 0°, 30°, 60°, 90°, 120°, 150°, and 180° tosimulate the infant’s head positions. As shown in Table 3, ofall of the directions of the diffuser, the highest values of lightirradiance and illuminance were obtained when the direc-tion of the diffuser was at 0° (40 W/m2 within 400–500 nmand 4925 lux), which is where the diffuser has the shortestvertical distance from the light source. When turning the

diffuser from 0° to 90°, the values of irradiance within thewavelength of 400–500 nm and illuminance were reducedsharply. When the angle moved continuously from 90° to180°, the low values of light irradiance and illuminance wereobtained. The measured values of light irradiance and illu-minance obtained from diffuser angles of 120° to 150° werehigher than those obtained from diffuser angles of 90° to180°. The results can be explained by the increased lightreflection of the white bedding sheet on the mattress.Thus, the direction between the diffuser and the light unitis another major factor in affecting the light irradiance andilluminance.

Effects of Design Components on Light Protection Performance of EPs In view of clinical application, the light protection per-formance of phototherapy EPs is not only affected by theconditions and settings of the light unit, but also influencedby the design and fabrication of the EP. Design compo-nents refer to the fabrication of the eye-patch panel whichis generally a composite structure to shield the infants’eyes, as well as the fitting of the EP to infant’s head whilethe light gap and its frequency of displacement should beminimized. In this study, the light protection performanceof the eye-patch panel of three EP samples was first exam-ined. The typical phototherapy setting of a 4B fluorescentlight unit and halogen light were used. The diffuser of thespectroradiometer was then shielded by EP1, EP2, andEP3, and the level of spectral irradiance and the light illu-minance were measured respectively. The results in Table 4show that the illuminance values obtained from the three

Figure 8 Spectral distribution oflight from various types of lightunit (4B, 2B2W, H).


EPs studied were reduced. The EPs can shield the infants’eyes from both fluorescent light unit and strong halogenlight unit effectively and safely, where the safety light levelin terms of illuminance magnitude was defined as lessthan 600 lux [8]. Amongst the three EP samples, EP3resulted in the lowest irradiance and illuminance valueswhich can provide the best light protection from photo-therapy light.

As the infant moves, the EP may become displaced veryquickly, allowing light to shine directly onto the infant’seyes. An ill-fitting EP results in light gaps and exposing theinfant’s eyes to the bright light. As far as fitting aspect isconcerned, the frequency and the level of light protectionin relation to the displaced positions of EPs were alsomeasured. The illuminance magnitude of EP3 with dis-tance and direction variation was mapped, see Figure 9.

Table 3 Light irradiance and illuminance measured at various settings of light conditions.

Settings of light conditions Irradiance (W/m2) Illuminance (lux)

Light units Variables at 350–800 nm at 400–500 nm

Fluorescent light unit with 4 blue tubes (4B) 146.7 40.4 4925

Fluorescent light unit with 2 blue and 2 white tubes (2B2W)

130.4 18.0 6453

Halogen light unit (H) 230.4 33.8 65,270

Fluorescent light (4B) with diffuser at six locations

A 110.9 18.6 1466

B 128.7 24.6 3044

C 142.5 37.0 4248

D 118.2 14.9 2264

E 146.7 40.4 4926

F 164.3 56.2 6365

Fluorescent light (4B) with diffuser at seven directions

0° 146.7 40.4 4926

30° 132.8 27.9 3508

60° 119.8 17.7 1235

90° 113.5 12.5 517

120° 117.2 15.8 889

150° 115.7 14.5 739

180° 113.2 12.4 459

Table 4 Light protection performance of EPs

Irradiance (W/m2) Illuminance (lux)

Illuminance Residual (%)

at 350–800 nm at 400–500nm

Ambient light at hospital 1.41 0.27 491 –

Fluorescent light (4B) without EP 46.7 40.4 4926 –

Shielded by EP1 0.51 0.32 59.3 1.2%

Shielded by EP2 0.35 0.10 27.0 0.6%

Shielded by EP3 0.18 0.06 12.7 0.3%

Halogen light (H) without EP 230.4 33.8 65,270 –

Shielded by EP1 4.01 0.41 1122 1.7%

Shielded by EP2 0.86 0.10 225 0.4%

Shielded by EP3 0.55 0.05 155 0.2%


Based on the 600-lux illuminance threshold, over which therisk of the retinopathy of prematurity increased signifi-cantly [8], a safety region was marked on the illuminancemagnitude map. EP3 resulted in the largest safety region(2000 mm2) as compared with EP1 (800 mm2) and EP2(400 mm2), referring to a more comprehensive EP designwhich reduces accidental light exposure and minimizes EPrepositioning. When the EP was displaced, the level of eyeprotection was determined by the covered area of eyes andthe light gaps since the light transmittance of the eye-patchpanel was consistent in all positions. Eyes were coveredcompletely when the EP was displaced within a safetyregion where only the light gaps could affect the level ofeye protection. The illuminance magnitude map thereforereveals that the light gaps were changed by the interactionof the EP and the face of the infant. When the edge of theEP approached the eyelid, the strong phototherapy lightcould still reach the eye through the light gaps and, thus,the illuminance value increased sharply and exceeded thesafety threshold. As shown in Figure 9, the light gaps inbottom directions affected eye protection significantlybecause light usually came in upper front directions whenthe infants were in a supine position.

A Safety Performance Prediction Model for Phototherapy Eye-Patch Protectors To predict the effects of EP displacement on light protec-tion performance of the textile EPs, non-linear regression

analysis was carried out. The values of light illuminance inrelation to the displacement distance and direction of the 3EPs studied were analyzed. The data of independent varia-bles was firstly standardized using Equations (1)–(3), allwith significance of ≤0.001. Non-linear regression was thenundertaken and the light illuminance can be derived as fol-lows:

IEP = a + b x + c y + d x2 + e y2 + f xy + g x3

+ h y3 + i xy2 + j x2y (4)

where I EP is calculated as the light illuminance (lux) as thediffuser of the spectroradiometer was shielded by EP; x isthe horizontal displacement of EP from optimum position(millimeters); y is the vertical displacement of EP fromoptimum position (millimeters); and a to j are the corre-sponding coefficient of variables derived from x and/or y.Using the Gauss Elimination Algorithm method, the mag-nitude of light illuminance could be predicted according tothe position of EPs. In all cases, the regression coefficientsobtained from each EP are higher than 0.900. The regres-sion models for EP1, EP2, and EP3 were formulated usinglight illuminance as the dependent variable and the dis-placement position and direction as the independent varia-bles with significance level of ≤0.000:

IEP1= –336.96 – 3.94x + 62.54y + 1.95x2 + 4.75y2

– 1.22xy – 0.03x3 + 0.06y3 – 0.02xy2 – 0.04x2y (5)

Figure 9 The relationship between light illuminance and displacement position of EP3.


IEP2= –289.84 – 7.81x – 21.19y + 0.87x2 + 6.58y2

+ 0.77xy – 0.01x3 + 0.30y3 + 0.07xy2 – 0.03x2y (6)

IEP3= –677.6 + 6.20x + 58.45y + 1.19x2 + 4.04y2

+ 1.38xy – 0.02x3 – 0.003y3 + 0.05xy2 + 0.02x2y (7)

Figure 10 shows the 3D surface fitting models of EP1 andEP2, where the level of light illuminance is correlated withtheir X and Y displacement positions, respectively. The fig-ures clearly show that moving the EPs would undoubtedlyincrease the light exposure at phototherapy treatment. Thedistribution of light illuminance varied with the distancesand directions of EP displacement. The plots indicate thatthe vertical and/or diagonal displacements of EP had amore radical effect on illuminance magnitudes than thehorizontal displacements of EP. In EP2, an upward verticaldisplacement of 5 mm resulted in light exposure immedi-ately, exceeding the 600 lux illuminance safety threshold.With further increase of the vertical displacement to 15–20mm, the illuminance magnitude reached a 4000 lux level.This indicates that the strong fluorescent light leakedthrough the light gaps and reached the infants’ eyes directlyas without EP shielding. Comparatively, EP2 resulted in thepoorest light protection performance amongst the three EPsstudied when it was displaced. The results revealed that theincrease of illuminance magnitude was mainly caused bythe design of the EP, the concave shape of the nose, andthe interaction of the materials and design.

Conclusion

In assessing the light protection performance of photother-apy EPs, the fabric structure and color were identified asthe important variables affecting light transmittance. Eventhough cotton single jersey fabrics offer excellent comfortto infants, the differences in light transmittance amongstthe fabrics examined were significant. This may be associ-ated with the constructional parameters of the fabrics suchas weight, thickness, yarn fineness, density, etc. While thesimple woven fabric with lowest light transmittance wasalso the thinnest, woven structures may be more desirablefor phototherapy light blocking as compared with singlejersey structure. Results from the current work also con-firmed that fabric color had a significant impact on thevalue of light transmittance. Black fabric offered the bestlight protection from both white and blue lights duringphototherapy treatment for degrading bilirubin in newborninfants. Textile phototherapy EPs are able to shield fluores-cent and halogen lights and protect the infant’s eyes safely.Nevertheless, differences in light illuminance as a result ofEP displacement also illustrated the importance of under-standing the relationship between EP design and protec-tion. For example, EP3 offers the largest safety regionwhich reduces accidental light exposure and light gapsagainst EP displacement. Light condition variables such asthe selection of light unit, location and direction of the dif-fuser had great effects on the level of light irradiance andilluminance. Such differences may have implications thatlight conditions must be taken into consideration whenevaluating the efficacy of the treatment. The non-linearregression models have demonstrated the influence of dis-tance and direction variation on the safety performance of

Figure 10 Prediction of light illuminance of (a) EP1 and (b) EP2 by 3D fitting model.


EPs. As a consequence, commercial EPs which use materi-als of light transmittance cannot present its actual protec-tion performance in a clinical phototherapy conditionaccurately. The safety performance of EP should also beevaluated in a simulated clinical condition, including bothoptimum and displaced positions to ensure that the EP ismaximally effective to protect the infants’ eyes during pho-totherapy treatment.

AcknowledgementThe research is supported by a grant from the ResearchGrant Council of the Hong Kong Special AdministrativeRegion, China (No.: POLYU 5299/04E)

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Light Protection Performance of Textile Phototherapy