Differential diagnosis of 'white' cataracts

Pubblicato il

Wednesday, 25 March 2015

Argomento

Surgical Area

White' cataracts can be a serious challenge: a few tips for correct diagnosis and surgical management

When the opacities of the lens become very advanced, the lens itself can take on a white tint that completely blocks light from entering the eye. These white' cataracts can lead to severe visual loss in patients and prevent ophthalmologists from properly examining the posterior segment of the eye.
White' cataracts can be complex to manage for many reasons and there are different sub-types that should be correctly identified in order to better address any difficulties during cataract surgery.

Dense vs. soft
Core density can vary widely, with some white cataracts being soft, milky and intumescent in nature, while others can be hard and rock-like, with a high degree of nuclear sclerosis.
The differential diagnosis between a dense and a soft white cataract is important in order to define a phacoemulsification surgical programme.
Dense white cataracts tend to develop in older patients and on slit-lamp examination a yellow to brown tint is visible towards the central portion of the lens. The anterior capsule tends to appear relatively flat, with no evidence of fluid within the capsular bag.
Once the capsule is stained with the trypan blue dye, the capsulorhexis should be easy to perform, as per routine, with little risk of radial tearing. However, due to the densities of the core, a higher degree of phaco ultrasonic energy will most likely be required and the risk of endothelial corneal trauma or even phaco burn is higher. For these eyes, covering the endothelium with a dispersive viscoelastic during phacoemulsification and using modulations of ultrasonic power may be helpful in reducing the risks.

Fig. 1: Dense white cataracts. These cataracts show a significant degree of opalescence and central density of the nucleus with a poorly milky, liquid appearance. Note centrally the yellow and brown hues in the lens (A), with cortical changes (B) and (C). Sometimes the central nucleus is much more opaque than the peripheral zone of the lens.

Soft white cataracts tend to develop in younger patients and present a white, milky fluid in the capsular sac. These intumescent white cataracts involve more effort to achieve capsulorhexis as the intraocular pressure increases as the outer lens film liquefies. In a routine cataract, the material constituting the lens is solid and the pressure inside the capsular bag is lower than the pressure present in the anterior chamber, allowing capsulorhexis to be easily achieved. In the case of white intumescent cataracts, the liquefied outer film increases the intracapsular pressure and causes the capsular bag to tear uncontrollably once it is opened. With the trypan blue coloured capsule, this uncontrolled radial tearing in the direction of the zonules creates the blue-white-blue image of the Argentine flag, which is why this complication is often referred to as the 'Argentine flag' sign.
To avoid the 'Argentinian flag sign' and radial capsule tears, it is necessary to keep the pressure of the anterior capsule higher than the intralenticular pressure when performing the capsulorhexis. Perform a small paracentesis and stain the capsule with trypan blue. Then fill the anterior chamber with a cohesive viscoelastic until the IOP remains high (40 mm Hg or more). At this point the capsulorhexis is only performed through this small paracentesis using a cystotome or a small 25-gauge microscissors.
Once resis is initiated, gently agitate the nucleus to release any intumescent fluid that may be trapped between the posterior capsule and the lens nucleus. With this technique, a circular capsulorhexis can be completed in most intumescent white cataracts.
Another option would be to instantaneously make a circular opening, as it has no angles or weak points that could give rise to radial lesions, in the anterior capsule of the lens. This can be done by using the phaco probe to remove a disc from the anterior capsule of the lens, resulting in decompression of the capsular bag, and then filling the anterior chamber with viscoelastic and performing the capsulorhexis.
Alternatively, a femtosecond laser could be used to perform the capsulorhexis as it would instantly cut through the entire capsule opening, while the anterior chamber would be pressurised with the suction ring.

[caption id="attachment_1580" align="aligncenter" width="400"] Fig. 2: Soft, milky white cataracts. These cataracts are filled with fluid and pose additional surgical difficulties. A homogeneous, milky appearance of the entire lens (A) is more common in young patients (B), who often have bilateral cataracts. The lack of yellow or brown hues is indicative of less nuclear sclerosis (C). Keeping the anterior chamber pressurised and using micro-grips (D) is helpful in minimising complications while capsulorhexis is performed.[/caption]

Abnormal white cataracts
White cataracts are difficult surgical cases and often occur in association with other eye diseases that can further complicate surgery. A traumatic white cataract may be associated with loss or fragility of the zonule. A white cataract that develops as part of chronic ocular inflammation may be associated with an irregular contour and capsule contraction. Congenital abnormalities in the development of the lens are more likely to evolve into early-onset cataracts.

[caption id="attachment_1581" align="aligncenter" width="400"] Fig. 3: Abnormal white cataracts. The irregular contour of the anterior capsule (A) suggests capsule contraction, zonular fragility and subsequent difficulties. This traumatic cataract is prolapsed in the anterior chamber (B) once the pupil has been dilated. On thorough examination the patient (C) was found to have a large area of congenital zonular deficiency. Sometimes white cataracts may be associated with other comorbidities as in this case of aniridia (D).[/caption]

White cataracts are not all the same, but differ in the nuclear density of the lens and the presence of a milky fluid within the intumescent capsular sac. Most of the time, a thorough pre-operative examination can identify any difficulties that can be successfully addressed during cataract surgery.
These patients are generally among the most satisfied as, thanks to surgical treatment, they can literally go from near-blindness to clear vision.

For further information
Dr Uday Devgan MD
Chief of Ophthalmology at Olive View UCLA Medical Center
Associate Clinical Professor at the Jules Stein Eye Institute at the UCLA School of Medicine.
E-mail:devgan@gmail.com
Web: www.DevganEye.com

Dr. Carmelo Chines
Direttore responsabile