Special (Additional) Tests for Patients with Cataract
CONTRAST SENSITIVITY TESTING
A patient is very symptomatic of these deficiencies but the commonly performed tests like the vision testing do not reveal the true extent of the defect. Measurement of contrast sensitivity enables one to understand these subtle defects in the visual function. This test even helps your doctor decide which eye is fit for the surgery.
The glare testing permits one to assess the deterioration in vision that occurs with a glare. Cataracts can produce significant scattering of light. Hence people with early cataracts may have good vision under ideal conditions of testing but the vision may deteriorate rapidly under conditions of glare. This testing enables one to decide on the need or otherwise for cataract surgery.
This is a very important test that enables one to calculate the desired power of the intraocular lens during cataract surgery. This artificial lens implanted in the same location as the natural lens permits one to have good vision without needing to use the thick glasses or contact lenses after cataract surgery. The test involves the use of ultrasound to measure the length of the eyeball and this information along with Keratometry (the measurement of the curvature of the cornea) is used to calculate the IOL power by a complicated formula.
Retinometer enables one to have an idea about the possible visual recovery following cataract surgery. In this testing, the examiner projects a grating into the back of the eye through the gaps in the cataract that enables the patient to identify the orientation of the grating. Depending upon the finest grating identified, the potential for recovery of vision is estimated. One should realize that this is only an approximate estimate and very often the true recovery of vision is greater than the estimate.
BLOOD INVESTIGATIONS / BLOOD PRESSURE MONITORING
The medical history and investigations determine the patient’s physical suitability for surgery at any given time. General investigations before surgery are those for any other operation. Particular care is taken to examine the respiratory system as any post-op coughing might provoke a uveal prolapse.
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