A brunescent cataract is an advanced nuclear cataract in which the nucleus has changed from yellow to deep brown, and, in the most extreme cases, to almost black.
The name cataracta nigra is used for this last stage.
These lenses are hard, and they are the ones that surgeons approach with the most caution.
Why the nucleus darkens
Throughout life, the nucleus of the lens becomes denser and more compact, as new fibers are laid down around the old ones.
Proteins in the nucleus aggregate and are modified by oxidation, glycation, and ultraviolet exposure, and they become cross-linked and pigmented.
The progression is from clear, to yellow, to amber, to brown, and finally to black.
Patients who have lived in tropical, high-altitude and high-UV environments, those who smoke, and those with diabetes and long-standing steroid use develop brunescence earlier.
In places where cataract surgery is delayed for economic or access reasons, brunescent cataracts are seen much more often than in places with early surgery.
What the patient experiences
- Vision loss that can be marked, with reduced contrast and color perception, and a perception that everything has a brown tinge
- Improved near vision for a time in some patients, due to the myopic shift (“second sight”), which gradually lessens as the nucleus darkens
- Glare, particularly in the dark
- In extreme cases, only light perception
On examination, the red reflex is dull or absent, the fundus is hard to see, and the lens may be seen as a dark brown mass behind the pupil.
Pseudophakic comparison of the two eyes may reveal a marked difference.
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From Choroida — the team behind this siteWhy surgery is more difficult
- The nucleus is hard and needs more ultrasound energy to emulsify, which increases heat and turbulence and puts the corneal endothelium at risk (see corneal endothelial decompensation)
- Hard nuclei are heavy, and fragments can damage the posterior capsule or fall into the vitreous
- Zonular stress is greater, particularly in patients with pseudoexfoliation or trauma
- Poor red reflex makes capsulorhexis harder, and trypan blue staining of the anterior capsule is often necessary
- The risk of posterior capsule rupture and vitreous loss is higher (see vitreous loss in cataract surgery)
- Wound burns and corneal edema are more frequent postoperatively
How surgeons plan for it
- Preoperative specular microscopy to assess endothelial reserve
- Use of dispersive and cohesive viscoelastic together (the soft shell technique) to protect the endothelium
- Phaco chop or divide-and-conquer techniques that reduce the energy used
- Careful hydrodissection and nuclear rotation
- Staining the capsule
- Considering manual small incision cataract surgery or extracapsular extraction when the nucleus is very dense and the endothelium is poor, particularly where phaco resources are limited
Postoperative course
Corneal edema is common in the first days and usually clears.
Dense nuclear fragments left behind or an IOP spike should be checked for.
Patients should be told about the possibility of prolonged edema, and about the longer recovery time compared with softer cataracts.
Talking to the patient before surgery
Patients with dense cataracts need honest information. Explain that the operation is more demanding, that the cornea may take longer to clear, that the risk of complications is higher than for a soft cataract, and that the final vision depends on the retina and optic nerve, which cannot be examined directly. Reassure them that, with good planning, most do very well, and that delaying further will only make the lens harder.
Assessing the back of the eye
Dense lenses hide the fundus, so a B-scan ultrasound is essential to exclude a detachment, a tumor, or a staphyloma. Check the pupil for a relative afferent defect, since an unexpected defect suggests optic nerve or retinal disease. Light projection and color perception are simple clinical tests that give some information about retinal function.
Early surgery as prevention
Public eye care programs have shown that earlier surgery reduces the number of brunescent lenses and their complications. In clinical practice, a patient who has had a gradual decline of vision and refuses surgery should be informed that the cataract will not shrink, and that waiting may make the operation less safe.
Prognosis
Visual results can be excellent when the retina and optic nerve are healthy, but the risk of complications is higher.
The best strategy is early surgery, before the nucleus becomes so hard.
Document what you see
Two smartphone imaging tools built for everyday clinic use — one for the slit lamp, one for the fundus.
From Choroida — the team behind this siteReferences
- Kelman CD. Phaco-emulsification and aspiration: a new technique of cataract removal. Am J Ophthalmol. 1967;64:23-35.
- Ruit S, Tabin G, Chang D, et al. A prospective randomized clinical trial of phacoemulsification vs manual sutureless small-incision extracapsular cataract surgery in Nepal. Am J Ophthalmol. 2007;143:32-38.
- Chylack LT Jr, Leske MC, McCarthy D, et al. Lens opacities classification system II (LOCS II). Arch Ophthalmol. 1989;107:991-997.
- Gogate P, Optom JJ, Deshpande S, Naidoo K. Meta-analysis to compare the safety and efficacy of manual small incision cataract surgery and phacoemulsification. Middle East Afr J Ophthalmol. 2015;22:362-369.
