Impact of environmentalpollution on the eye

Rohit Saxena,1 Sushma Srivastava,2 Deepa Trivedi,2 Eswaraiah

Anand,2 Sujata Joshi2 and Suresh Kumar Gupta2

1Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical

Sciences, New Delhi, India2Department of Pharmacology, All India Institute of Medical Sciences, New Delhi,

India

ABSTRACT.

Purpose: To study the effect of environmental toxins on the ocular surface in

persons travelling through highly polluted areas of the metropolis of Delhi.

Methods: A total of 500 apparently healthy volunteers recruited from the

metropolis of Delhi were examined to establish the frequency of ocular surface

disorders. All subjects underwent a slit-lamp examination, tear break-up time

(BUT) test, Rose Bengal test, Schirmer’s test and tear lysozyme level test.

Results: Subjects in the study group had significantly higher levels of ophthalmic

symptoms compared to the control group. In all, 105 (42%) and 125 (50%)

subjects in the study group compared to 50 (20%) and 65 (26%) in the control

group complained of redness and irritation (p < 0.05). There was no significant

difference in visual acuity (VA) between the two groups, with best corrected VA

being 6/9 or better in 92% of the study group and 96% of the control group. The

average (±standard deviation) Schirmer’s test result was 13.42±6.67mm in the

study group compared to 15.95±6.14mm in the control group. This difference

was statistically significant. The BUT was also significantly lower in the study

group (12.97±6.12 seconds) compared to the control group (19.23±5.70 seconds)

(p< 0.001). The Rose Bengal test and tear lysozyme activity did not show any

significant difference between the two groups.

Conclusion: According to our study, environmental conditions appear to have a

very significant effect on the ocular surface. There were very high levels of sub-

clinical ocular surface changes among persons travelling in highly polluted areas.

Key words: environmental toxins – ocular surface disorder – tear break-up time – lysozyme activity

Acta Ophthalmol. Scand. 2003: 81: 491–494Copyright # Acta Ophthalmol Scand 2003. ISSN 1395-3907

Introduction

Progressive industrialization and theincrease in the number of motorizedvehicles have resulted in high levels of airand water pollution. This environmentalpollution can have marked detrimentaleffects on human health. Although ill-effects on the skin and oropharyngeal

and respiratory systems are well docu-mented, the harmful effects of increasedair pollution on the eye have not beenwelldefined (Kjaergaard & Pedersen 1989;Paschides et al. 1998; Versura et al.1999). Due to the constant contact of thepreocular tear film, cornea and conjunc-tiva with the surrounding air, toxins have

direct access to these ocular structures andcan abnormally change them. A previousstudy (Frank&Skov 1991) suggested thatthe quality of environmental air can resultin premature break-up of the preoculartear film and corneal epithelial damage.This can lead to significant ocular irrita-tion and discomfort.

The aim of the current study was tostudy the impact of environmentalpollution and toxins on the eyes ofpeople who commuted daily on routeswith documented high levels of pollution.

Material and Methods

Study population

The study was conducted among healthy,adult volunteers working at the All IndiaInstitute of Medical Sciences hospital.The subjects were informed and enrolledafter written consent regarding the natureand purpose of the study had beenobtained. The subjects were divided intotwo groups.

The study group comprised peoplewho had commuted daily to the hos-pital using open vehicles (e.g. scooter,motorcycle and cycle) for more than10 years via areas identified as highlypolluted.

The control group comprised peoplewho had resided on the campus of theAll India Institute of Medical Sciencesfor more than 10 years and who werenot routinely involved in long distancetravel or significant exposure to vehicu-lar or industrial pollution.

ACTA OPHTHALMOLOGICA SCANDINAVICA 2003

491

All subjects enrolled in the study andcontrolgroupswerehealthy,non-smokingadults aged 35–65years who had beenemployed at the hospital for 10 or moreyears. All subjects were engaged in relatedactivities at the hospital and worked insimilar environments.Noneof the subjectshad any history of ocular surface disease,lid abnormalities or contact lens use andnonewerebeing treatedbyany systemicortopical drugs that might affect the ocularsurface.

All the subjects were employedin sedentary office jobs in the hospital.They were examined by a singleobserver, who was masked to theirhistory.

A detailed history was recorded foreach subject. It included information onthe subject’s age, sex, the distance theytravelled in kilometres per day, theircommuting time, mode of transport,period of travelling in years and thegeographic area travelled through whilecommuting.Ahistory of ocularmorbiditythat induced redness, irritation, foreignbody sensation, lacrimation, blurredvision, photophobia and eye strain wasalso taken. The duration of any of thesymptoms was recorded.

All the patients underwent a bestcorrected Snellen’s visual acuity (VA)assessment as well as lid, cornea andconjunctiva examination with slit-lamp.The tear film was examined using the slit-lamp for the presence of mucus, debris orparticulate matter. The height of the tearfilmwasmeasured inmmusing the gradu-ated slit-beam height.

All the subjects enrolled in the studyunderwent the following tests in the givenorder. There was a half-hour intervalbetween each of the tests conducted.

Schirmer’s test

Standardized strips of filter paper (Snostrips; Smith and Nephew Pharmaceuti-cals Ltd, Romford, UK) were hooked onthe rim of the lower eyelid at the junctionof the middle and lateral one-third of thelower eyelid margin, with the head of thestrip in the lower conjunctival fornix(Schirmer 1903). The strips did not touchthe cornea. No topical anaesthesia wasused and the patients remained relaxedwith open eyelids for 5min. After 5minthe strips were removed and the length ofthe wetted part was measured from thefold of the strip. Wetting of the stripgreater than 10mm was considered asthe normal value.

Break-up time

A dose of 10 ml of 1% fluoresceinsolution without any preservative oranaesthetics was applied in each eye(Norn 1969; Lemp 1973). The intervalbetween the last complete blink and theappearance of the first black spot in thefluorescein stained tear film withouttouching the eyelid was measured.Break-up time (BUT) was estimatedthree times in each eye and the meanvalue was calculated. Values over15 seconds were considered as normal.Values between 10 and 15 seconds weretaken to be indicative of a definiteabnormality.

Rose Bengal score

The Rose Bengal score (RBs) wascalculated by application of 10ml of 1%Rose Bengal solution without preserva-tives or anaesthetics in each eye (Norn1983). The patients were examined aftera waiting period of 2min, allowing theexcess stain to wash out. The degree ofstaining was estimated using the methoddescribed by Van Bijsterveld (1969).

Lysozyme activity

Lysozyme activity in tears was measuredusing the method described by Mackie &Seal (1976). Normal values are reportedas 70units/ml at 20 years of age to40units/ml at 85 years of age. The cut-offpoint used in the study was 50units/ml.Any value below this level was taken toimply a deficiency of lysozyme activity.

Statistical analysis

Each of the tests between the twogroups was compared using Chi-squareand Fisher’s exact tests. Data were alsoanalysed to study the possible effects ofmode of transport and number of milestravelled daily.

Results

Atotal of 500 subjectswere enrolled in thestudy, with 250 patients in each group.The study group consisted of 160 malesand 90 females with a mean age of47.7� 14.9 years. The control groupincluded 145 males and 105 females witha mean age of 50.2� 12.2 years. The ageand sex distribution was comparablebetween the two groups (p¼NS).

Subjects in the study group had asignificantly higher degree of ophthal-mic symptoms compared to the controlgroup (Table 1). Direct questioningestablished occasional ocular redness,irritation and lacrimation to be presentin nearly half of the study group, with105 (42%) and 125 (50%) of subjectscomplaining of redness and irritation,respectively, compared to 50 (20%) and65 (26%) of subjects in the controlgroup (p< 0.05). However, none ofthese symptoms were severe enough toresult in the subjects seeking any treat-ment for them. There was no significantdifference in VA between the twogroups. Best corrected VA was 6/9 orbetter in 92% of the study group and96% of the control group.

The average Schirmer’s test resultwas 13.42� 6.67mm in the studygroup compared to 15.95� 6.14mm inthe control group. This difference wasstatistically significant (Table 2). Lessthan 10mm wetting of the strip wasconsidered an abnormal value. In all,28 (11.2%) subjects in the study groupand 10 (4%) in the control group hadan abnormal Schirmer’s test result(p< 0.001). The BUT was also signifi-cantly lower in the study group(12.97þ 6.12 seconds) compared to thecontrol group (19.23� 5.70 seconds;p< 0.01). The Rose Bengal test andtear lysozyme activity did not show

Table 1. Ocular subjective complaints in the control and study groups.

Parameters Control group Study group p-value

n (%) n (%)

Redness 50 (20) 105 (42) <0.05

Irritation 65 (26) 125 (50) <0.05

Lacrimation 45 (18) 95 (38) <0.05

Blurred vision 10 (4) 40 (16) NS

Photophobia 5 (2) 10 (4) NS

Eye strain 35 (14) 60 (24) NS

Burning 0 (0) 70 (28) <0.001

Dryness 0 (0) 20 (8) <0.01

n¼ number of persons; NS¼non-significant.

ACTA OPHTHALMOLOGICA SCANDINAVICA 2003

492

any significant difference between thetwo groups (Table 2).

In the study group, 160 subjects trav-elled by a two-wheeler, either a bicycleor a scooter, while the rest travelled inclosed automobiles. In the controlgroup, all subjects walked to workdaily. In the study group, there was nosignificant difference in the Schirmer’sor BUT results between subjects travel-ling in closed vehicles and those usingopen vehicles (p> 0.05).

Discussion

Recently, there has been an upsurge ofinterest in the detrimental effects of

pollution and environmental toxins(Norn 1992). Studies by Frank & Skov(1991) and Carsten & Boge (1993) haveevaluated the ocular side-effects arisingfrom poorly ventilated buildings.

The immediate effects of exposure toairborne toxins include watering, burningand redness of the eyes. However, theocular effects of chronic, longtermexposure to a high degree of environmen-tal pollution are still unclear. The qualityof air in New Delhi is the worst in Indiaand among the worst of most metropol-itan cities of the world. The level ofsuspended particulate matter (SPM) inNew Delhi is five times higher than theannual average control limit of 60mg/m3

set by WHO (Table 3). However, despitethe high average pollution levels, certain

pockets of the city, which are purelyresidential and have more surroundingvegetation, maintain better air quality.The residential campus of the All IndiaInstitute of Medical Sciences has amodest amount of vegetation and lowvehicular traffic, with the result that theaverage quality of air on the campus isbetter than that in some of the morepolluted parts of the city. As the trans-port sector is the most important cause ofair pollution (Fig. 1), people who travellong distances, especially during peakhours, are maximally exposed to thistype of pollution.

Although none of the subjects in thisstudy had symptoms significant enoughto cause them to consult an ophthal-mologist, a very high percentage ofthem reported ocular problems ondirect questioning.

There was a significant degree ofocular surface disorder as seen by thesignificantly higher levels of abnormalSchirmer’s test and BUT results in thestudy group.

According to our study, climatic con-ditions appear to have a very significanteffect on the ocular surface. Very highlevels of subclinical ocular surfacechanges were found in persons travel-ling in highly polluted areas. These highlevels may represent a cause for con-cern if they are found to reflect theocular status of the general populationsof large metropolises like Delhi. As wellas longterm measures to decrease thelevel of air pollution in the environ-ment, short-term measures such asusing protective goggles while travel-ling in polluted areas can be taken todecrease ocular contact with airbornetoxins.

We recommend that larger scale stud-ies be carried out to document histo-pathological and ultra structuralchanges in the ocular surface.

ReferencesCarsten F & Boge I (1993): Break-up time

and lissamine green epithelial damage in

‘office eye syndrome’. Ophthalmologica 71:

62–64.

Frank C & Skov P (1991): Evaluation of two

different questionnaires used for diagnosing

ocular manifestations in sick building syn-

drome on basis of an objective index. Indoor

Air 1: 5–11.

Kjaergaard S & Pedersen OF (1989): Dust

exposure, eye redness, eye cytology and

mucus membrane irritation in the tobacco

Table 2. Various parameters affected in populations unexposed and exposed to environmental

pollution.

Control group

n¼ 500 eyes

Study group

n¼ 500 eyes

p-value

Tear film break-up time (seconds) 19.23� 5.70 12.97� 6.12 <0.001

Schirmer’s test (mm) 15.95� 6.14 13.42� 6.67 <0.001

Rose Bengal test 0.59� 0.31 0.61� 0.24 NS

Tear lysozyme activity (units/fl) 63� 5.33 59� 6.88 NS

n¼number of persons; NS¼ non-significant.

Table 3. Ambient air quality status in Delhi showing annual mean concentration range (mg/m3) of

SO2, NO2, suspended particulate matter (SPM) and respirable suspended particulate matter

(RSPM).

Annual mean concentration range (mg/m3)

Pollutants SO2 NO2 SPM RSPM

Delhi 10–40 40–90 210–360 180–200

Source: Central Pollution Control Board.

Fig. 1. Relative contributions of the domestic, industrial and transport sectors to air pollution in

Delhi.

ACTA OPHTHALMOLOGICA SCANDINAVICA 2003

493

industry. Int Arch Occup Environ Health 61:

519–529.

Lemp HA (1973): Break-up time of tear film.

In: Holly FJ & Lemp HA (eds). The Precor-

neal Tear Film and Dry Eye Syndrome.

International Ophthalmology Clinics. Boston:

Little Brown 97–102.

Mackie IA & Seal DV (1976): Quantitative tear

lysozyme assay in units of activity per micro-

litre. Br J Ophthalmol 60: 70–74.

NornMS (1969): Desiccation of precorneal film.

I. Corneal wetting time. Acta Ophthalmol

(Copenh) 47: 865–880.

Norn MS (1983): Rose Bengal. In: Norn MS

(ed). External Eye. Methods of Examina-

tion. Copenhagen: Scriptor 60–64.

Norn M (1992): Pollution keratoconjunc-

tivitis. Acta Ophthalmol Scand 70:

269–273.

Paschides CA, StefaniotouM& Papageorgiou J

(1998): Ocular surface and environmental

changes. Acta Ophthalmol Scand 76: 74–77.

Schirmer O (1903): Studien zur Physiologie

und Pathologie der Tranenabsonderung

und Tranenabfuhr. Graefes Arch Clin Exp

Ophthalmol 56: 197–291.

Van Bijsterveld (1969): Diagnostic tests in the

sicca syndrome. Arch Ophthalmol 82:

10–14.

Versura P, Profaxio V, CelliniM, Toregginae A&

Caramazza R (1999): Eye discomfort and air

pollution. Ophthalmologica 213: 103–109.

Received on March 11th, 2003.

Accepted on May 10th, 2003.

Correspondence:

Dr S. K. Gupta

Professor and Head

Department of Pharmacology

All India Institute of Medical Sciences

New Delhi 110029

India

Tel:þ 91 11 265 93 633

Fax:þ 91 11 265 88 663

Email: skgup@hotmail.com

ACTA OPHTHALMOLOGICA SCANDINAVICA 2003

494