Description, Causes and Risk Factors:
A cataract is defined as any opacity (or opacities) of the lens of the eye. Such opacities may be quite small and interfere little with vision, or they may involve the entire lens causing blindness. Cataracts occur because something interferes with the normal function of lens fibers causing them to degenerate. Causes include inflammatory diseases, hereditary factors, aging changes, toxicities, and metabolic diseases such as diabetes mellitus.
A cataract is said to be mature when all the cortical fibres become opaque. Depending on the pathophysiological processes that cause the cortical fibre opacification this phenomenon may be associated with a varying degree of nuclear sclerosis.
The mature cataract may represent one or both of two clinical entities. The cortical mature cataract has opaque, milky white, (potentially) liquefied cortex that, at surgery, obscures the red reflex and the nature of the underlying lens nucleus. The nuclear mature cataract contains an ultrafirm and visibly dark lens nucleus in which an epinucleus cannot be easily delineated and little to no cortex remains; it may consist virtually of `rock-hard' nuclear lens material and lens capsule. Given that a very dark cataract can obscure the red reflex and that a white cataract may harbor an ultradense nucleus, there may be crossover between the two entities.
Factors that increase your risk of cataracts include:
Drinking excessive amounts of alcohol.
Excessive exposure to sunlight.
Exposure to ionizing radiation, such as that used in X-rays and cancer radiation therapy.
Family history of cataracts.
High blood pressure.
Previous eye injury or inflammation.
Previous eye surgery.
Prolonged use of corticosteroid medications.
This study aimed to investigate the relationship between the hardness of mature cataracts and the transmitted nuclear colour, age and rate of progression of the cataract. Thirty-eight patients with mature cataracts were assessed prior to extracapsular cataract surgery. The nuclear colour that was transmitted through the opaque cortex was graded using reference photographs. Age and duration of visual symptoms were recorded and lens hardness was measured by a specially designed lens guillotine. Multivariate analysis of data indicates a relationship between hardness of a mature cataract and the transmitted nuclear colour and age (adjusted R2 = 0.59). There is also a tendency for hardening of the lens as the duration of visual symptoms increases. By considering these clinical markers, the cataract surgeon can estimate the hardness of the lens and therefore its suitability for phacoemulsification.
Vision reduced to just perception of light.
Iris shadow is not seen.
Lens appears pearly white.
Lens is completely opaque.
The eye professional can observe cloudy areas on the lenses with a direct physical examination, even before the cataracts begin to interfere with vision. Cameras can measure the cataract density. Various vision tests are also performed.
One of the most difficult and often puzzlingproblems which faces by the clinical ophthalmologist is that of estimating the prognosis ofvisual function which will be obtained followingthe extraction of a mature cataract. Under normalconditions with clear intraocular media, theophthalmoscopic examination of the fundus provides a source of considerable information concerning the structure, and often the function ofthe retina. In addition, the visual acuity of the eyein question can be easily and accurately measured,and any refractive error which might be presentcan be overcome by the usual means. In the presence of a mature cataract however, funduscopic examination becomes impossible due to the obstruction of the light pathway by the opacity ofthe media. And for the same reason errors ofrefraction cannot be corrected either by objectiveor subjective methods. It is well known that anaccurate evaluation of retinal function can be obtained by electroretinography (ERG), and as early as1940 several authors published reports of accuratemeasurement of visual acuity in the presence ofopaque media by projection of x-rays on to theretina in varying image sizes.More recently theelectro-pupillograph has been used to measurepupillary response to light both in clear and opaquemedia, with an eye toward correlating the amplitude of pupillary contraction with the visual function of the retina and optic pathways.Howevernone of these methods are practical tools in thearmamentarium of the clinician. And thoughelectroretinography is a tried and proven methodof estimating retinal cellular function, the othertwo examinations are of doubtful application. Forthe measurement of visual acuity is hardly worththe risks entailed by exposure of the eye toradiation, and the study of pupillary light responseand its correlation with visual function is toofraught with pitfalls to be very reliable, as weshall explain later, even if the electro-pupillograph were accessible to the average ophthalmologist, which it obviously is not. For this reason wefelt it would be worthwhile to review some of theclassic tests for retinal function as well as some ofthe more obscure ones, limiting our choice of teststo these which were simple, not too time consuming for the physician, and which would require the least effort on the part of the patient.The object of our study was to attempt to determine which, if any of the simple and uncomplicated tests of retinal visual function would be ofmost help to the ophthalmologist in his assessmentof the probable vision which could be expectedafter cataract extraction.
Mature cataracts pose certain challenges to the surgeon and add surgical outcome risks to patients. Because phacoemulsification may be anything but routine in these cases, ophthalmologists have historically considered alternative surgical methods when faced with mature cataracts of either type. Nevertheless, observant presurgical evaluation, careful surgical planning, and skillful and diligent surgical technique can combine (with good fortune) to afford the patient the opportunity for rapid visual and physical recovery by means of small incision cataract surgery. Patients contemplating surgery for a mature cataract should be counseled regarding the likelihood for increased surgical time, a slower recovery of vision postoperatively, and an increased risk for intraoperative complications. Likewise, the surgeon must be properly prepared for the increased demands necessary for successful small incision surgery in these cases.
Continuous circular capsulorrhexis is now widely used in cataract surgery. In the case of mature cataract, however, this technique may be difficult due to the poor visibility of the anterior capsule. This problem can be overcome performing capsulorrhexis under air. A small amount of a high molecular weight viscoelastic agent is injected near the incision, so as to avoid air escaping from the anterior chamber. Visibility is good and the handling of the anterior capsule is easy and safe.
NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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