Outcome of cataract surgery in Nigeria: visual acuity, autorefraction, and optimal intraocular lens powers--results from the Nigeria national survey.

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 15027 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 20449 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.