Christmas tree cataract. A cute catastrophe!

A 60-year-old female presented to the eye clinic of our hospital for a routine eye examination. Her best-corrected visual acuity was 20/20 in both eyes. Slit-lamp examination after pupillary dilatation revealed an array of polychromatic, iridescent, needle-shaped opacities in the otherwise clear lens of her left eye, giving the appearance of multi-colored, vivid lights decorating the branches, as on a twinkling Christmas tree [Figure 1]. The colors of the needle-shaped opacities changed according to the angle of the incident light [Figure 2 and Video 1]. There was no anomaly in the posterior segment, and the fellow eye examination was unremarkable. Intraocular pressure (IOP) was 12 mm of Hg in the right eye and 10 mm of Hg in the left eye with non-contact tonometry. No ptosis or restriction of ocular movement was present. The patient denied experiencing any muscular stiffness or weakness. There were no systemic abnormalities in the patient. The neurological assessment of the patient was normal, and she was advised to undergo follow-up in view of her excellent visual acuity.

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Figure 1:

A post-dilatation slit-lamp view of the left eye at ×6 magnification reveals a sparkling pattern of cataract.

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Figure 2:

A post-dilatation slit-lamp view of the left eye at ×16 magnifications reveals an array of needle-shaped, iridescent, multi-colored lenticular opacities in the deep cortex, suggestive of Christmas tree cataract.

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Christmas tree cataracts present as unilateral or asymmetrical bilateral cataracts that, although visually insignificant, can progress to impair vision. Usually asymptomatic, they are detected during a regular ocular examination. They are usually idiopathic but highly prevalent in people suffering from myotonic dystrophy (DM).^[1] DM is an autosomal dominant disease that has two forms: type 1 and type 2. DM1 is commonly known as Steinert’s DM, which primarily affects individuals of European descent. It has a prevalence ranging from 1 in 8000 to 1 in 10,000, making it the most common muscle disease in adults. DM1 is caused by the expansion of cytosine-thymineguanine (CTG) trinucleotide on the dystrophia myotonica protein kinase (DMPK) gene on chromosome 19, causing reduced expression DMPK gene-associated protein in skeletal muscle, cardiac muscle, endocrine glands, extraocular muscles, ciliary body, and retina, leading to abnormal DNA repair throughout life. Mild clinical manifestations typically occur when a patient has 50 or more CTG repeats and severe manifestations with counts >100 in the DMPK gene.

DM2 is less common than DM1 and is caused by abnormal expansion of the tetranucleotide, cytosine-cytosine-thymineguanosine (CCTG) repeat, of the CCHC-type zinc finger nucleic acid-binding protein gene on chromosome 3. It has a later age of onset with a milder clinical presentation compared to DM1; however, in view of identical ophthalmological manifestations, a similar clinical approach should be taken.

DM itself is characterized by a delay in muscle relaxation, along with cardiac dysrhythmia, gastrointestinal symptoms, and a higher risk of cancer, primary hypogonadism, insulin resistance, hypertriglyceridemia, abnormal liver function tests, and premature balding. Other associated possible ocular findings include Fuchs’ endothelial corneal dystrophy (FECD), ptosis, reticular maculopathies, and uveal melanoma [Table 1]. Lower-than-average IOPs are frequently observed in this condition. Ophthalmologists in clinical care have the distinctive role to detect such a striking pattern of cataracts and promptly raise the potential presence of concomitant DM before manifestation of its systemic symptoms. Besides identifying the typical Christmas tree pattern cataracts, it is prudent in such cases to identify other associated key features mentioned in Table 1. Workup should include a thorough slit-lamp examination looking for corneal guttata, iris nevi, or melanomas, testing of pupil for light and accommodation response, and tests for extraocular muscle movements. A dilated fundus examination should be undertaken to rule out reticular or other pattern maculopathies as well as subtle choroidal nevi that may suggest uveal melanoma. Specular microscopy should be performed to detect FECD and retinal imaging (optical coherence tomography and fundus photography) for possible retinal pathologies. Patients who are suspected of having DM should be further tested for a creatine kinase blood test and be referred for an electromyogram and genetic testing. Since this type of cataract could be the first sign of DM, along with the existence of a fairly large gap (approximately 10 years) between the diagnosis of the cataract and the onset of clinically significant systemic symptoms,^[1,2] prompt referral for neuromuscular assessment after detecting such a pattern of cataract may facilitate early diagnosis and treatment of this complicated disease. Besides, for the visually significant cataract among these subjects, the hydrophobic acrylic monofocal intraocular lenses (IOLs) are a better choice compared to the multifocal IOLs, as the latter may decenter due to the risk of capsular contraction and phimosis.^[3,4] Assessment of corneal health by monitoring endothelial cell counts with specular microscopy is crucial during pre-operative evaluation of cataract extraction. Furthermore, due to the cardiac risk, ropivacaine hydrochloride is the safest anesthetic drug of choice for local anesthesia.^[5]

The neurological examination of the subject patient was normal, and she was advised to undergo follow-up.