Module 6: Cataracts: Leading Cause of Blindness Worldwide

When the lens of an eye becomes clouded and opaque, light passage to the retina is obscured and the eye has developed a cataract. It has been estimated that 20 million people are blind because of cataracts that can be cured with surgical intervention, making cataracts the leading cause of blindness throughout the world.(1) 

“The largest proportion of blindness is necessarily related to ageing. Although cataract is not a major cause of blindness in developed countries, globally it is still the leading cause, accounting for almost half of all cases, despite improved delivery of cataract surgical services in many parts of the world. Cataract is even more significant as a cause of low vision; it is the leading cause of low vision in all subregions.”(2)

Surgical Treatment

Cataracts can usually be successfully removed, thus restoring visual acuity to the patient. Cataract surgery involves removing the cataract lens and replacing it with a plastic intraocular lens (IOL). There are several different methods of cataract removal.  Phacoemulsification and SICS yield the highest quality results.

  1. Phacoemulsification: ultrasound is used to emulsify the eye’s internal lens, which is then aspirated from the eye. This requires a much smaller incision than extracapsular or intracapsular cataract extraction.
  2. Small Incision Cataract Surgery (SICS): the cataract nucleus is manually removed through a small incision in the sclera, and the remaining cortex is removed by aspiration.
  3. Extracapsular Cataract Extraction (ECCE): manual removal of the lens through an incision in the cornea or sclera.
  4. Intracapsular Cataract Extraction (ICCE): manual removal of the lens and the surrounding capsule through an incision in the cornea or sclera.

Phacoemulsification and SICS both yield high-quality results,(3) and have led to increased efficiency and volume of cataract surgeries across the world. (4)(5) Technological advancements in intraocular lenses have also contributed to increased cataract surgical rates worldwide:

 “Over the past twenty years, the major advance in the treatment of cataract has been the worldwide availability of low-cost, good-quality intraocular lenses (IOLs) since the early 1990s. Their routine use has resulted in an increase in both the quality of visual outcome for patients (as shown by population-based rapid assessment of cataract surgical services) and the willingness of surgeons to perform cataract surgery at an earlier time, before blindness has developed… There is evidence that, since the introduction of IOLs, there has been an increase in cataract surgical rates around the world, and particularly in low-income countries.”(6)

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Footnotes

(1) Balent, L.C., Narendrum, K., Patel, S., Kar, S., and Patterson, D.A. “High Volume Sutreless Intraocular Lens Surgery in a Rural Eye Camp in India.” Ophthalmic Surgery & Lasers. 32.6 (2001): 446-455. Accessed on 12 January 2009.

(2) Resnikof, S., Pascolini, D., Etya’ale, D., Kocur, I., Pararajasegaram, R., Pakharel, G.P., and Mariotti, S.P. “Policy and Practice: Global Data on Visual Impairment in the Year 2002.” Bulletin of the World Health Organization. 82.11 (2004): 844-851. Accessed on 13 January 2009.

(3) Ruit, S., Tabin, G., Chang, D., Bajracharya, L., Kline, D.C., Richheimer, W., Shrestha, M., and Paudyal, G. “A Prospective Randomized Clinical Trial of Phacoemulsification vs. Manual Sutureless Small-Incision Extracapsular Cataract Surgery in Nepal.” American Journal of Ophthalmology. 143.1 (2007): 32-38. Accessed on 13 January 2009.

(4) Foster, A., Gilbert, C., and Johnson, G. “Changing patterns in global blindness: 1988-2008.” Community Eye Health. 21.67 (2008): 37-39. Accessed on 13 January 2009.

(5) Ruit et al., 2007.

(6) Foster et al., 2008.