Elsevier

Ophthalmology

Volume 118, Issue 4, April 2011, Pages 719-724
Ophthalmology

Original article
Outcome of Cataract Surgery in Nigeria: Visual Acuity, Autorefraction, and Optimal Intraocular Lens Powers—Results from the Nigeria National Survey

https://doi.org/10.1016/j.ophtha.2010.08.025Get rights and content

Objective

To describe presenting and corrected visual acuities after cataract surgery in a nationally representative sample of adults. Another objective was to describe refractive errors in operated eyes and to determine the optimal range of intraocular lens (IOL) powers for this population.

Design

Cross-sectional, population-based survey.

Participants

Adults aged 40 years and more were selected using multistage stratified sampling and proportional to size procedures. A sample size of 15 027 was calculated, and clusters were selected from all states.

Methods

Individuals who had undergone cataract surgery were identified from interview and examination. All had their presenting visual acuity (VA) measured using a reduced logarithm of the minimum angle of resolution chart and underwent autorefraction. Corrected VAs were assessed using the autorefraction results in a trial set. An ophthalmologist conducted all examinations, including slit-lamp and dilated fundus examination. Causes of visual loss were determined for all eyes with a presenting VA <6/12 using the World Health Organization recommendations. Biometry data were derived from 20 449 phakic eyes using the SRK-T formula after excluding those with poor VA or corneal opacities.

Main Outcome Measures

Presenting and corrected visual acuities in pseudo/aphakic individuals and autorefraction findings; biometry profile of Nigerian adults.

Results

Data from 288 eyes of 217 participants were analyzed. Only 39.5% of eyes had undergone IOL implantation at surgery. Only 29.9% of eyes had a good outcome (i.e., ≥6/18) at presentation, increasing to 55.9% with correction. Use of an IOL was the only factor associated with a good outcome at presentation (odds ratio 9.0; 95% confidence interval, 4.3–18.9; P=0.001). Eyes undergoing cataract surgery had a higher prevalence and degree of astigmatism than phakic eyes. Biometry data reveal that posterior chamber IOL powers of 20, 21, and 22 diopters (D) (A constant 118.0) will give a postoperative refraction range of −2.0 D to emmetropia in 71.4% of eyes, which increases to 82.6% if 19 D is also included.

Conclusions

Postoperative astigmatism needs to be reduced through better surgical techniques and training, and use of biometry should be standard of care.

Financial Disclosure(s)

The author(s) have no proprietary or commercial interest in any materials discussed in this article

Section snippets

Materials and Methods

Details of the methods used in the survey have been published.14 A sample size of 15 027 persons aged ≥40 years was calculated on the basis of the target population of 23.6 million people aged ≥40 years (or 17.6% of 133 million total Nigerian population, according to a 2005 projected estimate), a blindness prevalence estimate of 5.0%, an absolute precision level of 0.5% with 95% statistical confidence, and further adjusting for a design effect of 1.75% and 15% for non-response. Multi-stage

Results

A total of 13 591 participants were examined of the 15 122 enumerated, giving a response rate of 89.9%. The response rate ranged from 88.2% to 91.1% in the 6 geopolitical zones. A total of 7031 participants (46.5%) were male, and 77.6% lived in rural areas.

A total of 583 eyes had undergone procedures for cataract, in 299 right eyes and 284 left eyes. A total of 148 right eyes were included in the analysis after excluding couching (129 eyes), trauma (21 eyes), and eyes with missing data on the

Discussion

The findings of this national survey are similar to the findings of many other population-based studies from developing countries (Table 4, available at http://aaojournal.org)23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33 where poor outcomes (using presenting VA) range from 12% in the Philippines to 64% in Cameroon. All studies with disaggregated data demonstrate that IOL surgery gives far better presenting visual acuities than non-IOL surgery: an unknown number of eyes without IOLs may have had

References (33)

  • T. Walia et al.

    Improving surgical outcomes

    Community Eye Health

    (2008)
  • A. Bejiga et al.

    Cataract surgical coverage and outcome in Goro District, Central Ethiopia

    Ethiop Med J

    (2008)
  • W. Mathenge et al.

    Rapid assessment of avoidable blindness in Western Rwanda: blindness in a postconflict setting

    PLoS Med

    (2007)
  • J.E. Oye et al.

    Prevalence and causes of blindness and visual impairment in Limbe urban area, South West Province, Cameroon

    Br J Ophthalmol

    (2007)
  • J.E. Oye et al.

    Prevalence and causes of blindness and visual impairment in Muyuka: a rural health district in South West Province, Cameroon

    Br J Ophthalmol

    (2006)
  • M.M. Rabiu

    Cataract blindness and barriers to uptake of cataract surgery in a rural community of northern Nigeria

    Br J Ophthalmol

    (2001)
  • Cited by (0)

    Manuscript no. 2010-479.

    Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

    This study was funded by CBM, Sightsavers International, and Velux Stiftung.

    *Group members listed online in Appendix 1 (available at http://aaojournal.org).

    The Nigeria National Blindness and Visual Impairment Study Group is available at http://aaojournal.org.

    View full text