Posterior Polar Cataract Workup

Updated: Feb 07, 2019
  • Author: Rachel A Scott; Chief Editor: Hampton Roy, Sr, MD  more...
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Workup

Laboratory Studies

Apart from a complete blood count (including hemoglobin and hematocrit), no laboratory examinations have been shown to be necessary prior to posterior polar cataract surgery.

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Imaging Studies

A chest radiograph may be obtained prior to surgery.

Anterior segment optical coherence tomography (AS-OCT) has been studied as a method to grade posterior polar cataracts and to identify eyes at high risk for poster capsule rupture. In a study by Chan et al involving 39 eyes, 18 of which were classified as grade 2 (< 50% clearance between the posterior opacity and the capsule) or grade 3 (absence of an intact posterior capsule), anterior segment OCT had a sensitivity of 87.5% and specificity of 62.1% in predicting intraoperative poster capsule rupture, showing that this imaging study could allow for better surgical planning and preoperative counseling. [22, 23] Pavan Kumar et al showed that preoperative AS-OCT had a sensitivity of 100% and specificity of 94.92% in detecting posterior capsule dehiscence, which further supports the use of AS-OCT to predict posterior capsule rupture during phacoemulsification in these patients. [24]

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Other Tests

A-scan ultrasonography should be performed.

Although routinely done prior to almost all preoperative workups, keratometry readings should be performed to aid in intraocular lens (IOL) calculations.

Electrocardiography should be performed to rule out any associated disorders, which have been mentioned but often do not contraindicate posterior polar cataract surgery.

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Diagnostic Procedures

The diagnosis of a posterior polar cataract is self-evident on slit-lamp examination and does not require special diagnostic procedures beyond a full ophthalmic examination. Slit-lamp examination and pupillary retroillumination allow a good evaluation of the visual significance of the opacity. The anterior vitreous should be examined carefully to ensure that it is free of opacity or capsular adherence.

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Histologic Findings

A posterior polar cataract has been shown to present as an opacity in the subcapsular portion of the lens that consists of malformed, disorganized, and degenerated lens fibers. As these fibers migrate posteriorly from their origin at the equator, increased degenerative changes have been shown as they reach the posterior pole. This results in a dense discoid opacity that is often surrounded by an area of vacuoles and abnormal lens fibers. Often, these abnormal lens fibrils are connected to the underlying posterior capsule.

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Staging

Posterior polar cataracts have not been staged, probably because of their rare occurrence.

At present, the Lens Opacities Classification System (LOCS) uses slit-lamp images to grade color and opalescence, as well as retroillumination images to grade cataracts and posterior subcapsular opacities. Cataract severity is graded on a decimal scale that reportedly shows good correlation between different observers. This system, however, does not specifically deal with posterior polar cataracts.

The literature is sparse on this aspect of posterior polar cataracts. The average practice encounters relatively few cases. Grading of posterior polar cataracts was reported by Forster and colleagues in 2006. [25] Out of 33 patients aged 1 week to 8 years with lens opacities, 3 patients were noted to have posterior polar cataracts. The grading was done subjectively and also objectively with the use of photographs. Grading used a scale of 0-10. Posterior polar cataracts graded a 6 indicated surgical removal.

A suggested concept would be to classify these opacities according to size and density. The size range would be 0.5-3 mm in increments of 0.5 mm. Density would be staged from 1+ to 4+ with increasing density as judged by the ability to visualize the posterior capsule.

Moreover, posterior polar cataracts can sometimes be associated with other lens opacities, which can be classified according to the LOCS.

Finally, the main hindrance in fully adopting a functional grading system for posterior polar cataracts appears to be the small sample sizes used. This is because the entity is rare. The author would be glad to receive case reports, which could be correlated into a meaningful classification algorithm.

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