Approach
A patient with a cataract will describe blurred or cloudy vision. The diagnosis of cataract is made by either seeing the lens opacity during an examination of the lens with a slit lamp, or observing opacities of the lens through defects in the red reflex seen during direct ophthalmoscopy.
History
Enquire about risk factors associated with cataract formation, including:[3][9][10][11][12][18][19][20][21]
Age >60 years
Diabetes mellitus
Certain metabolic or hereditary conditions (e.g., Wilson's disease, galactosaemia, myotonic dystrophy, Marfan's syndrome)
Long-term use of ocular corticosteroids
A family history of congenital cataract or congenital influences (e.g., toxins, infections such as rubella)
Smoking
Long-term exposure to ultraviolet light
Previous eye trauma.
Cataracts classically present as a gradual decrease in vision over many years that the patient may be very slow to recognise until there is some visual impairment (e.g., problems reading subtitles or captions on the television). However, under certain circumstances, such as in a patient with diabetes mellitus, there may be a relatively sudden reduction in vision.[22] Patients may describe blurred vision and glare, especially when driving at night.
A patient with a progressing nuclear sclerotic cataract may report inadequate glasses prescription. This may be the result of thickening of the lens, causing an increase in refractive power, and making the patient appear to be increasingly myopic (near-sighted). The change in lens proteins occurring in nuclear cataracts often causes a yellowish hue to the cataract, and patients will note a decreased richness in colours, especially blues.
Examination
Initial assessment by the ophthalmologist includes the following:[35][36]
Visual acuity test: with the patient's best-corrected spectacle correction at standardised distance and illumination conditions for both near and far vision
Slit-lamp examination: to evaluate the lens following pupillary dilation. In cases of significant cataract, opacification of the lens will be seen. In children, and in adults unable to cooperate with slit-lamp examination, observation and comparison of the red reflex using direct ophthalmoscopy can help quantify the severity of the cataract
Glare testing: uses a brightness acuity tester to induce glare stress. Allows the examiner to measure the patient's visual acuity under the type of glare conditions that the patient might experience in the real world
Intra-ocular pressure.
No other tests are routinely performed to make the diagnosis of cataract other than a physical examination of the lens. Occasionally, with dense cataracts and no view of the posterior pole, an ultrasound is performed to assess the status of the vitreous and retina.
It is important to assess best visual potential before commencing with cataract surgery. This may involve pinhole acuity potential, potential acuity meter, or a macular optical coherence tomography imaging test to assess structural integrity of the fovea.
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