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IntroductIon

The Nepal national survey (1981) estimated a blindness prevalence of 0.84% of which 72% was due

to cataract.1 This led a wide range of international and national non-governmental organizations to establish a National Eye Care Program, primarily focused on reduction of cataract blindness. Since 1983, the Lumbini Rana Ambika Shah Eye Hospital, now known as the LEI (LEI) has provided most of the cataract surgical services in the Lumbini Zone.

A 1995 study of the Lumbini and Bheri Zones found a severe visual impairment (< 6/60) prevalence of 3.9% in people older than 45 years and cataract

Ophthalmic Epidemiology, 17(5), 276–281, 2010Copyright © 2010 Informa Healthcare USA, Inc.ISSN: 0928-6586 print/ 1744-5086 onlineDOI: 10.3109/09286586.2010.508355

ORIGINAL ARTICLE

cataract Surgical outcome and Predictors of outcome in Lumbini Zone and chitwan

district of nepal

Ram Prasad Kandel,1 Yuddha Dhoj Sapkota,2 Anil Sherchan,3 Manoj Kumar Sharma,3 Jaafar Aghajanian,4 and Ken L Bassett4

1Seva Nepal, Kathmandu Nepal2Nepal Netra Jyoti Sangh, Kathmandu Nepal

3Lumbini Eye Institute, Bhairahawa Nepal4British Columbia Centre for Epidemiologic & International Ophthalmology, Vancouver Canada

AbStrAct

Purpose: To evaluate visual acuity outcome from cataract surgery based on a population-based survey among people aged 50 years and older in Lumbini Zone and Chitwan District of Nepal.Methods: A randomly selected, population-based cross sectional epidemiological study of blind-ness, visual impairment and cataract surgical outcome was conducted. All subjects underwent a comprehensive ocular examination by an ophthalmic assistant, while people with visual impair-ment (visual acuity less than 6/18) after refraction and all cataract surgical cases underwent dilated fundus examination by an ophthalmologist.Results: 5,916 people were enumerated and 5,141 (86.9%) examined. Among the 359 people who had cataract surgery, 485 eyes were included in the study. First eye surgery was before 2000 in 84 (23%), between 2000 and 2003 in 130 (36%), and after 2003 in 145 (41%). A presenting visual acuity ≥ 6/18 was achieved in 298 (61.4%) eyes (10 [17.8%] and 288 [67.1%] of aphakic and pseudophakic eyes, respectively) and best corrected vision ≥ 6/18 in 411 (84.7%) in all eyes. A presenting visual acuity less than 6/60 was found in 27 (6.3%) pseudophakic eyes. There was no significant differ-ence in visual outcome based on age, sex, literacy, or institution. Uncorrected refractive error was the main cause (72.9%) of visual impairment in pseudophakic eyes.Conclusions: Visual acuity outcome after cataract surgery requires further improvement to meet World Health Organization standards, particularly improvement in preoperative biometry and refractive services. The same quality cataract surgery was provided in and equitably distributed throughout Lumbini Zone and Chitwan District independent of age, sex, literacy or location.

KEYWordS: cataract surgery; Nepal; population-based survey; predictors of outcome; visual acuity outcome

Received 23 February 2010; Revised 31 May 2010; Accepted 12 June 2010

Correspondence: Dr. Ken Bassett, Director, UBC Centre for Epidemiologic and International Ophthalmology, St. Paul’s Hospital, 1081 Burrard Street, Vancouver, BC. Canada V6Z 1Y6. E-mail: bassett@chspr.ubc.ca

23 February 2010

31 May 2010

12 June 2010

© 2010 Informa Healthcare USA, Inc.

2010

Ophthalmic Epidemiology

0928-65861744-5086

10.3109/09286586.2010.508355

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surgical coverage (< 6/60) of 42% in the Lumbini Zone.2 The study also reported that 30% of cataract surgical patients had severe visual impairment (pre-senting visual acuity [VA] < 6/60).3 In 2006, LEI staff sought updated evidence regarding the quality of cataract surgery in the Zone and its population-based program impact.

The LEI conducted an epidemiologic survey of Lumbini Zone to estimate (a) the prevalence of blind-ness, (b) the cataract surgical coverage and (c) the visual outcome of cataract surgery among people 50 years and older. A companion paper reports on the first two objectives.4

MEthodS

The study was conducted in six Districts of Lumbini Zone (Gulmi, Palpa, Argakhanchi, Rupendehi, Kapilvastu, Nawal Parasi) and Chitawan District in Narayani Zone. These seven Districts cover two con-trasting terrains; one consists of hills and mountains in the north stretching to the high Himalayas, and the other plane areas extending to northern India. More than 90% of Nepali patients treated at LEI and affiliated hospitals are from these 7 Districts.

The study methods are provided in detail else-where.4 In brief, the total population of the Lumbini Zone constituted the sampling frame.5 The actual geographic boundaries of the selected segments were defined and a total of 2,267 clusters were created from the all wards of the Zone and Chitwan District. We combined small villages (population < 500 persons of all ages) and divided larger villages (population > 2000 persons of all ages) to create sampling clusters with nearly 175 (108 to 216) people 50 years (total population between 850 and 1,700) in each cluster. We used simple random sampling without replace-ment (based on the 2001 population census estimate of 12.75% population aged 50 years and older and a total survey population of 39,216 people) to select 32 clusters for the study.

The sample size was calculated based on estimating a severe visual impairment prevalence (presenting VA <6/60) as 8% within error bound 15% with 95% con-fidence interval. With expected non-response of 15%, and cluster design effect 2.0, the total sample required was estimated as 4,619.

An ophthalmic assistant tested VA at 4 meters using a retro-illuminated logMAR chart with tumbling-E optotypes (Precision Vision, Villa Park, Illinois). Refraction (Retinoscope and subjective) was per-formed for anyone having presenting VA < 6/18 in either eye. People wearing glasses were tested with them and their vision considered as presenting vision.

Basic eye examination using direct ophthalmoscope and slit lamp was performed by a single ophthal-mologist from LEI who attended all study sites. Lens status—aphakia or psuedophakia—was noted for all cataract operated eyes along with whether the extrac-tion method was intracapsular (ICCE) or extracap-sular (ECCE) and whether an intra-ocular lens was implanted (ECCE-IOL). Subjects were asked the date (month and year) and where surgery took place for each operated eye.

All eyes were dilated if the VA did not improve to 6/18 with refraction, except eyes where visual impairment was obviously due to corneal opacity or cataract (defined as a lens opacity precluding view of the fundus). Intra-ocular pressure was measured using a Perkins hand-held tonometer if glaucoma was suspected based on optic disc changes (primar-ily cup-to-disc ratios > 0.5 and unhealthy optic disc rim). Eyes with VA < 6/18 were assigned a principal cause of impairment/ blindness by the examining ophthalmologist from a predefined list.

Four visual categories were defined for analysis and reporting: (1) normal or near normal vision, 6/18 or better in both eyes; (2) visual impairment, unilat-eral or bilateral visual impairment, < 6/18 to 6/60 in the worse eye; (3) severe visual impairment: < 6/60 in the better eye; (4) bilateral blindness: < 3/60 in both eyes.

The proportion of aphakic and pseudophakic eyes with good visual outcome (≥ 6/18) was determined for both presenting and best corrected vision. Multiple logistic regression was used to determine the associa-tion between age, sex, literacy, institution for surgery and visual outcome. In bilaterally operated eyes only one eye was included in the model to maintain independence among eyes. Regression analyses were based on the first-operated eye, rather then the second-operated eye (or the better eye) to avoid the possibil-ity that first eye outcome influenced patient behavior regarding the type, timing or place of surgery for the second eye.

Odds ratios were calculated for predictors of visual outcome, with 95% confidence intervals (CI). We con-sidered a P value < 0.05 as significant. Missing values were assumed similar in distribution to the available data and were ignored during analysis.

Verbal informed consent was obtained from par-ticipants. The examination protocol was cleared by the World Health Organization (WHO) Secretariat Committee on Research Involving Human Subjects. The project was approved by the Ethical Review Committees of Nepal Netra Jyoti Sangh (National Society for Prevention of Blindness) and the LEI. Patient confidentiality was maintained as per protocol. People with minor eye conditions were treated at the

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examination site, while those needing more compli-cated procedures, including cataract surgery, were offered free transportation and an operation at the base hospital.

rESuLtS

A total of 359 cataract operated people (487 eyes) were identified in the survey (Table 1). This includes 127 (35.6%) people operated in both and 230 (64.4%) operated only in one eye (data missing for 2 people). Among them, 34 (8.1%) had aphakia, 8 (2.2%) pseu-dophakia in one eye and aphakia in the other, 106 (29.5%) bilateral and 209 (58.2%) unilateral pseu-dophakia. None of the people with bilateral aphakia, but 47.2% of the people with bilateral pseudophakia had presenting VA equal to or better than 6/18 in both eyes (Table 1).

Among all operated eyes, 61.4% had presenting VA 6/18 or better and 84.7% after best correction (Table 2). Of pseudophakic eyes, 288 (67.1%) had presenting VA of 6/18 or better (increasing to 89.0% after correction of refractive error) while 27 (6.3%) had severe visual impairment (presenting VA <6/60). For aphakic eyes, 10 (17.8%) had presenting VA 6/18 or better (increasing to 51.8% after correction), while 28 (50%) had severe visual impairment (presenting VA < 6/60).

There was no significant association between presenting VA of 6/18 or better in the first operated eye

and age, sex, literacy or institution of surgery (Table 3). The area of patient residence (data not shown) was also not associated with VA outcome (odds ratio: 0.9 [95% CI 0.52–1.53]). A presenting VA 6/18 or better was sig-nificantly associated with undergoing surgery after the year 2000 (odds ratio: 2.41 [95%CI 1.26–4.61] and 2.19 [95%CI 1.01–4.71] compared with 2000–2003 and 2003–2006, respectively).

Patient selection resulted in VA less than 6/18 in 8 (4%) pseudophakic eyes with retinal disorders and 3 (2%) with amblyopia (Table 4). Refractive error, including uncorrected aphakia caused a total of 54.2% of visual impairment (<6/18) and severe visual impair-ment (< 6/60) in operated eyes (Table 4). Refractive error was the major cause of visual impairment in both pseudophakic (72.9%) and aphakic (71.4%) eyes, and the most common cause of severe visual impairment and blindness (<6/60) in aphakic eyes (24%). Surgical sequelae resulted in visual impairment in 16 (8%) psue-dophakic eyes due to posterior capsular opacification (Table 4).

dIScuSSIon

Visual acuity after cataract surgery has improved in Lumbini Zone and Chitwan District in the past 10 years. In this study, presenting VA of 6/18 or better was achieved in 61.4% (67.4% in pseudophakic) and 84.7% after refractive error correction. Ten years ago in

TABLE 1 Lens status of cataract operated people by presenting visual acuity.*

Presenting Visual AcuityAphakiaUni or

BilateralPseudophakia/

AphakiaBilateral

PseudophakiaUnilateral

Pseudophakia All≥ 6/18 0 (0) 1 (12.5) 50 (47.2) 34 (16.3) 85 (23.7)< 6/18 ≥ 6/60 8 (23.5) 0 (0) 37 (34.9) 49 (23.4) 94 (26.2)< 6/60(worst eye) 14 (41) 6 (75.0) 17 (16.0) 122 (58.4) 160 (44.6)< 6/60 ≥ 3/60(best eye) 2 (6) 0 (0) 0 (0) 1 (0.5) 3 (0.8)< 3/60 10 (29.4) 1 (12.5) 2 (1.9) 3 (1.4) 17 (4.7)ALL 34 (9.4) 8 (2.2) 106 (29.5) 209 (58.2) 359 (100)* Data are given as number (%) of people. Data missing for two people

TABLE 2 Presenting and best corrected visual acuity outcome, aphakic and pseudophakic eyes* Best Corrected Visual Acuity

Presenting visual acuity

≥ 6/18 < 6/18 to ≥ 6/60 < 6/60 to ≥ 3/60 < 3/60 All≥ 6/18 9 (100)

275 (100) 9 (16.0)

275 (64.1)< 6/18 to≥ 6/60 11 (76.9)

103 (84.1)3 (23.1)

17 (15.9) 14 (25.0)

120 (28.0)<6/60to≥ 3/60 2 (40.0)

1 (14.3)3 (60.0)4 (57.1)

0 (0.0)2 (28.6)

5 (8.9)7 (1.6)

< 3/60 7 (25.0)3 (11.1)

9 (32.1)2 (7.4)

0 (0.0)0 (0.0)

12 (42.9)22 (81.5)

28 (50.0)27 (6.3)

All 29 (51.8)382 (89.0)

15 (26.8)23 (5.4)

0 (0)2 (0.5)

12 (21.4)22 (5.1)

56 (100)429 (100)

*Data are given as number (%) of eyes. Data for aphakic eyes given above pseudophakic eyes.

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the Lumbini Zone, presenting VA was 6/18 or better in only 15% of eyes (no data on VA after refractive error correction).2 In this 2006 survey, presenting VA < 6/60 in operated eyes (11.3% overall and 6.7% in pseudophakic eyes) is also much lower than the 1995 Lumbini survey (30.4%).2 The most likely explanation is that only14% of eyes examined in 1995 had had pseudophakic surgery, compared with approximately 90% of eyes in 2006.

Similar improvement in surgical technique and visual outcome were found in a survey of the adjacent Gandaki Zone in Nepal in 20026 (plus unpublished data from YD Sapkota, accessed 2009) with 63.4% of eyes having a presenting VA of 6/18 or better and 12.6% with severe visual impairment (6/60) (66.5% of the Gandaki study had pseudophakia). However,

although improved, visual outcome in pseudophakic eyes in both Nepal sites fall short of the WHO recom-mendation of 80% with presenting vision 6/18 or better and less than 5% with vision less than 6/60.

A 2005 study of Satkhira District, Bangladesh reported a similar number of pseudophakic eyes see-ing 6/18 or better after refractive error correction (87% versus 89% in the Lumbini survey) but a much higher percentage of uncorrected pseudophakic eyes (82% versus 63.4% in the Lumbini survey) achieved this threshold.7 The Bangladesh study also had fewer eyes not able to see 6/60 after correction (5.1% versus 6.7% in the Lumbini survey).

Surveys in neighboring countries estimated poorer VA outcome following cataract surgery. In Orakzai

TABLE 3 Presenting and best corrected visual acuity in operated on eyes

Aphakia Pseudophakia

All eyes Eyes % PVA≥ 6/18 %BCVA≥ 6/18 Eyes % PVA≥ 6/18 % BCVA≥ 6/18Sex Male 26 30.8 61.5 188 67.0 88.8 214Female 30 6.7 43.3 241 67.2 89.2 271Literacy Literate 6 16.7 50.0 38 60.5 84.2 44Illiterate 50 18.0 52.0 391 67.8 89.5 441Institution NGO/Hospital 34 17.6 52.9 338 68.6 89.6 372Private. Hospital 22 18.2 50.0 91 61.5 86.8 113Age 50–59 yrs 4 25.0 75.0 70 70.0 94.3 7460–69 yrs 14 21.4 35.7 164 70.1 91.5 178+ 70 yrs 38 15.8 55.3 195 63.6 85.1 233All eyes 56 17.9 51.8 429 67.1 89.0 485Note: Multiple logistic regression found no significant association between presenting visual acuity ≥ 6/18 in first operated eye and sex, literacy, institution, or age.Sex: odds ratio 0.86 (95% CI: 0.61–1.22).Literacy: odds ratio 1.57 (95% CI: 0.72–3.38).Institution: odds ratio 0.88 (95% CI: 0.49–1.58).Age (compared to 50–59): for 60-69 odds ratio 1.14 (95% CI: 0.59–2.21); for 70+ odds ratio 0.79 (95% CI: 0.40–1.55).BCVA = best corrected visual acuity; PVA = presenting visual acuity.

TABLE 4 Principal cause of impaired vision/blindness in operated eyes*

Presenting Visual Acuity< 6/18 to 6/60

Visual Impairment< 6/60 to 3/60

Severe Visual Impairment < 3/60 BlindnessCause of Low Vision Aphakia Pseudo-phakia Aphakia Pseudo-phakia Aphakia Pseudo-phakia TotalRefractive Error 10 (71.4) 89 (72.9) 1 (20.0) 1 (14.3) 7 (25.0) 1(3.7) 109 (54.2)Corneal Opacity 0 11 (9.0) 0 4 (57.1) 4 (14.3) 1 (3.7) 20 (10.0)PCO 1 (7.1) 15 (12) 0 0 0 0 16 (8.0)Retinal disorder 1 (7.1) 3 (2.4) 2 (40.0) 2 (28.6) 5 (17.9) 3 (11.1) 16 (8.0)Globe disorder 1 (7.1) 2 (1.6) 0 0 3 (10.7) 2 (7.4) 8 (4.0)Amblyopia 0 0 1 (20.0) 0 0 3 (11.1) 4 (2.0)Other/ undetermined 1 (7.1) 2 (1.6) 1 (20.0) 0 9 (32.1) 15 (55.6) 28 (13.9)Total 14 (100) 122 (100) 5 (100) 7 (100) 28 (100) 25 (100) 201 (100)* Data are given as number (%). Data missing for 2 people.

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Agency in Pakistan, among pseudophakic eyes, only 12.4% achieved presenting vision of 6/18 or better and 13.4% had vision less than 6/60.8 In South India (1999) only 25.2% of people had bilateral presenting VA 6/18 or better, compared with 50% in this survey.9 However, South India reported that only 63% of eyes were psuedophakic compared with 90% in this survey. The Lumbini survey visual outcomes were slightly worse than presenting vision among pseudophakic eyes in Tirunelveli District of Southern India (5.1% less than 6/60).10 The Pakistan National Blindness and Visual Impairment Survey in 2007 found 55% of pseudophakic patients had presenting VA greater than or equal to 6/18 compared to over 60% in both recent Nepali surveys, and 8.7% in the Pakistani study had a presenting VA less than 6/60 compared to 6.7% in the recent Lumbini study.11

Visual acuity outcome was similar for all ages, men and women, literate and illiterate and in all areas. This reflects LEI’s strong outreach program dedicated to providing equitable high quality care throughout the Zone. LEI supports cataract surgery in the more remote hill districts through an eye hospital in Tansen, the only hospital in the hill districts of Nepal, and a network of regular screening visits and surgical eye camps conducted by the resident ophthalmologist in Tansen.

The numerically higher VA outcome for LEI patients (68.6% presenting vision 6/18 or better) compared with private hospitals (61.5%) contrasts with findings from the study of Tirunelveli district in southern India.10 In the Indian setting, the presenting visual outcome from the institution analogous to LEI (Aravind Eye Care System) was 78.3% (6/18 or bet-ter) while the private facilities was 83.9%. The authors of the Tirunelveli study, similar to another study in India assumed that surgical quality was similar but that case-mix favored the private clinics which likely served younger, healthier patients with less ocular and systemic co-morbidity.10

In terms of causes of poor visual outcome in cataract operated eyes, incorrect patient selection was evident for retinal disorders, the third leading causes of visual impairment and blindness. However, 8 of the 16 eyes were associated with aphakia, which seldom occurs with new intra-ocular lens techniques. Amblyopia was noted in 3 pseudophakic eyes, but neither these nor other disorders suggested any opportunities to improve pre-operative patient selection.

Uncorrected refractive error accounts for 72.9% of the visual impairment (less than 6/18 and greater than or equal to 6/60) in pseudophakic eyes. Of the 89 eyes in this category, only 4 people were reported as wearing glasses at presentation. This study did not investigate issues related to glasses, such as

whether they were prescribed and lost or rejected. The study also did not analyze which component of refractive error was causing visual impairment such as deviation from emmetropia or uncorrected high astigmatism.

The uncorrected refractive error finding in pseu-dophakic eyes raised significant concern about the accuracy of biometry at LEI, which accounts for approximately 80% of surgery in the Zone. A quality assurance process was established that included new equipment and improved technical training. The uncor-rected refractive error finding also resulted in a change in policy that added biometry to eye camps (previously without biometry) where approximately 1,500 cataract operations occur each year. Further analysis comparing refractive error prevalence in camp versus hospital was not possible through this survey because these details were not recorded.

In terms of surgical sequelae, posterior capsule opacification occurred in 60 (12.5%) eyes, and was associated with visual impairment in 16 eyes (15 pseudophakic). Posterior capsular opacification was not considered the cause of severe visual impairment or blindness in any eye. The rate of severe opacification seems low in this sample, recognizing that 214 (60%) out of the 359 people were at least 3 years post cataract operation. However, no long term Nepali or Indian data on posterior capsule opacification were available to compare with the Lumbini study findings. Future studies are planned to determine whether opacification is associated with a technique, intra-ocular lens type, or duration since surgery.

Surgical complications, although at times suspected, were not noted as a cause of poor visual outcome. Instead, they were categorized more generally as “globe disorder” or “other” because specific surgical compli-cations were not evident through history or clinical examination.

LEI faces significant challenges to its cataract surgi-cal program both to improve outcome to contempo-rary pseudophakic standards and to meet increasing demand for its services. During the past 10 years the population age 50 and older in the Lumbini Zone and Chitwan District increased from 390,000 to 435,000 with a corresponding increase in life expectancy from 54 to 63 years. From 1995 to 2006, the number of cataract operations in Lumbini Zone increased from approximately 4,000 (3,300 LEI + 700 private and conducted elsewhere) to 6,700 (5,700 LEI); a cataract surgical rate of 2,666 per million. However, this will need to increase substantially to deal with both the backlog of prevalent as well as the growing number of incident cases. In addition, LEI will need to anticipate increased demand for second eye surgery and surgery on less visually impaired eyes.

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concLuSIonS

Visual outcome after cataract surgery requires improvement to meet World Health Organization rec-ommendations, particularly improvement in preopera-tive biometry and refractive services. Visual outcome is very similar by age, sex, literacy, institution, and geographic location.

AcKnoWLEdGMEntS

The authors wish to thank Ram Chandra Shrestha and Tulasi Parajuli for their fieldwork throughout the study and Praveen Nirmalan and R.P. Pokhrel who served on a Technical Advisory Committee. In addi-tion, the authors are grateful to Royes Joseph and the Aravind Eye Care System who conducted statistical analysis and the LEI that provided staff and logistical support.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

rEFErEncES

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2. Pokharel GP, Regmi G, Shrestha SK, Negrel AD, Ellwein LB. Prevalence of blindness and cataract surgery in Nepal. Br J Ophthalmol. 1998;82:600–605.

3. Pokharel GP, Selvaraj S, Ellwein LB. Visual functioning and quality of life outcomes among cataract operated and unoperated blind populations in Nepal. Br J Ophthalmol. 1998;82:606–610.

4. Sherchan A, Kandel RP, Manoj, Sapkota YD, Aghajanian J. Bassett KL. Blindness and eye diseases in Lumbini Zone and Chitwan District of Nepal: Findings from a ran-domized, population-based survey. Br J of Ophthalmol. 2010;94:161–166.

5. Central Bureau of statistics of Nepal. Statistical Year Book of Nepal, 2001.

6. Sapkota YD, Pokharel GP, Nirmalan PK, Dulal S, Maharjan IM, and Prakash K. Prevalence of blindness and cataract surgery in Gandaki Zone, Nepal. Br J Ophthalmol. 2005;90;411–416.

7. Wadud Z, Kuper H, Polack S, Lindfield R, Akm MR, Choudhury KA, Lindfield T, Limburg H, Foster A. Rapid assessment of avoidable blindness and needs assessment of cataract surgical service in Satkhira District, Bangladesh. Br J Ophthalmol. 2006;90:1225–1229.

8. Anjum KM, Qureshi MB, Khan MA, Jan N, Ali N, Ahmad K, Khan MD. Cataract blindness and visual outcome of cataract surgery in a tribal area in Pakistan. Br J Ophthalmol. 2006;90:135–138.

9. Thulasiraj RD, Reddy A, Selvaraj S et al. The Sivaganga Eye Survey: II Outcome of Cataract surgery. Ophthalmic Epidemiol. 2002;9:5:313–324.

10. Nirmalan PK, Thulasiraj RD, Rahamatulla R, et al. A popula-tion based eye survey of older adults in Tirunnelveli district of south India: blindness, cataract surgery and visual out-comes. Br J Ophthalmol. 2002;86:505–512.

11. Bourn RA, Dineen B, Jadoon MZ, Lee PS, Khan A, Johnson GJ, Foster A, Khan D. Prevalence of blindness and visual impair-ment in Pakistan: The Pakistan national blindness and visual impairment survey. Br J Ophthalmol. 2007;91:420–426.

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