Cataract

Cataract Clinical Outcomes

Cataracts occur because the lens of the eye loses its transparency and becomes opaque. In Singapore, the percentage of elderly patients affected by cataracts is about 78.6%.¹ The number of people affected by cataracts also increases as they get older (It affects 63.6% of people between 60 and 64 years, and 94.6% of people 75 years and older.)

The common symptoms of cataracts include blurry vision, glare (lights may appear too bright, or halo may appear around lights), and poor night vision. Usually patients with cataracts do not experience itching, tearing or headaches. As eyeglasses and drugs do not decrease opacity of the lens, the only way to treat cataracts is to surgically remove them. Fortunately, modern cataract surgery is a very effective way in restoring vision in those afflicted with visual impairment due to cataract.^2,3

Due to the high incidence of cataracts in Singapore, cataract surgery has become one of the most commonly performed ophthalmic operations. Data from Medisave claims showed that the number of cataract surgeries performed increased from 5,679 operations in 1986 to 12,177 in 1995⁴. There was also a steady increase in the rate of cataract surgery from 2772 operations per 100,000 persons/year in 1991 to 4650 per 100,000 persons/year in 1996.⁵

Various Kinds of Cataract Surgery

With progress in technology and surgical techniques, ophthalmologists now have safe and effective methods to restore vision, even at early stages. The three main types of cataract removal techniques typically employed are:

• Intracapsular Cataract Extraction

  Intracapsular cataract extraction (ICCE) involves the removal of the entire lens and its capsule using a cryopencil. This is an older technique and while not in use in many countries, is still being applied in developing countries for subluxated cataracts.^{6, 7}.
  

• Extracapsular Cataract Extraction (ECCE)

  Extracapsular Cataract Extraction (ECCE) was the technique of choice for cataract surgery in Singapore, until the advancement of Phacoemulsification (PE) in the last several years⁸.
  
  In ECCE, a 12mm incision is made in the eye to extract the lens. The lens capsule is left in place to hold an intraocular lens. About seven sutures are then used to seal the eye after surgery and are carefully tightened so as not to produce astigmatism. Presently, ECCE is the alternative for patients unsuitable for Phacoemulsification (PE).
  

• Phacoemulsification (PE)

  Phacoemulsification is currently the most advanced technique for cataract removal and the method of choice in Singapore and other developed countries like the United Kingdom and the United States of America.
  
  An ultrasound probe is used to breakdown the opaque lens without harming the capsule. These fragments are then aspirated out and a foldable intraocular lens (IOL) is then placed in through the 3mm incision. Once within the eye, the lens unfolds to take position inside the capsule.
  
  The advantage of this method is that no sutures are needed because of the self-sealing incision used. Hence visual rehabilitation occurs within a shorter period of time due to the reduced post-operative inflammation⁹ and decreased surgically induced astigmatism. The procedure is safe enough to be done under topical anaesthesia (anaesthetic eyedrops). Visual rehabilitation is extremely fast and patients do not need to suspend their everyday activities. 

Cataract Outcomes in the National University Hospital^

In 2008, NUH has performed about 1940 cataract surgeries. The success rate or "Best Corrected Visual Acuity (BCVA)¹⁰ of 6/12 or better" is 99.6% for PE technique. This is better than international success rates. In a UK study, the BVCA of 6/12 or better was reported to be 94.7%.¹¹

The NUH safety rates for PE were also measured to be 98.03% benchmarked against a safety rate of 97.4% in the UK study.¹¹

NUH is also conducting ongoing studies to monitor its cataract outcomes. This enables a continual monitoring system so that appropriate techniques and practices can be implemented for best clinical results for patients.

^These outcomes are based on an audit of operations carried out by Consultants and Senior Consultants from Jan-Dec 2008. NUH follows up on all of their patients after their operations to monitor their outcomes.

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Information is correct as at November 2009

Footnotes

1. Ho T, Law NM, Goh LG, Yoong T. Eye diseases in the elderly in Singapore. Singapore Med J 1997;38:149-55
2. Au Eong KG, Yap EY, Lee HM, Yong VSH. Questions frequently asked about cataract and its surgery. The Singapore Family Physician 1996;22:108-12.
3. Goh KY. Advances in ophthalmology. Singapore Med J 1999;40:563-4.
4. Lee SY, Tan D. Changing trends in cataract surgery in Singapore. Singapore Med J 1999;40:256-9.
5. Wong TY. Cataract extraction rates among Chinese, Malays, and Indians in Singapore: a population-based analysis. Arch Ophthalmol 2001;119:727-32.
6. Lee SB, Au Eong KG, Yong VSH. Management of subluxated lenses with planned intracapsular cataract extraction and anterior chamber intraocular lens implantation. Singapore Med J 1999;40:352-5.
7. Au Eong KG, Lee SB. Test your eye-Q (no. 5): long standing loss of vision. The Singapore Family Physician 1998;24:32.
8. Au Eong KG, Heng WJ, Leo SW. Understanding Age-related Cataract and Modern Cataract Surgery. The Singapore Family Physician Jul- Sept 2002 Vol 28 (3): 16
9. Chee SP, Ti SE, Sivakumar M, Tan DTH. Postoperative inflammation: extracapsular cataract extraction versus phacoemulsification. J Cataract Refract Surg 1999;25:1280
10. Definitions:
• Cataract is defined as lens opacity observed by an ophthalmologist and a visual acuity of 6/9 or worse in the same eye
• Blindness defined as best corrected visual acuity of 6/60 or worse in the better eye
• Visual impairment defined as best corrected visual acuity of worse than 6/12 but better than 6/60 in the better eye
• Success rates is defined as percentage of operated eyes without comorbidity (without other diseases or conditions) that achieved a Best Corrected Visual Acuity (BCVA) of 6/12 or better within the third month after the operation
11. Jaycock P, Johnston RL, Taylor H, Adams M, Tole DM, Galloway P, Canning C, Sparrow JM and UK EPR user group. The cataract National dataset electronic multicentre audit of 55 567 operations: updating benchmark standards of care in the United Kingdom. Eye 2009, 23:38-49

This material does not cover all information and is not intended as a substitute for professional care. Please consult your physician on any matters regarding your health.