December 4, 2023 | J.Y. Jones

Brain Plasticity in Children with Cataracts

 

 

Observations on Brain Plasticity and Imaging in Children
Undergoing Late Congenital Cataract Surgery

by J.Y. Jones MD

The dogma has always been that congenital cataract, while not an emergency, is certainly a situation that requires expedited surgical treatment. This is especially true of total, or completely opaque, cataract. Certain medical conditions predispose infants to have this condition at birth, such as congenital rubella (contracting German measles in the womb), chondrodysplasia, and certain metabolic syndromes. The occurrence of total bilateral cataracts is often associated with genetic mutation, usually the result of an autosomal dominant inheritance.

Whatever the cause of congenital cataract, the treatment of choice is most often very early surgery. “Early” usually means 2-4 weeks of age, when the infant is stable enough to tolerate general anesthesia. In prosperous and modern societies, this is done with little delay, but in underdeveloped countries there is often a tragic postponement of treatment.

Personal Experience

I performed surgery for congenital cataract in my private practice on quite a few occasions, though few people accumulate enough such procedures that they become expert at it. There has always been a debate whether congenital cataract should be removed by a pediatric ophthalmologist or an experienced cataract surgeon. Since the latter is what I was considered to be, I usually did my own congenital cataract cases, and almost without fail with decent results.

On a mission trip, one is likely to see pathology that is rare in the United States, so your choice is to try to help the patient or else leave it for the next mission surgeon. When it came to congenital cataract, I never hesitated to do the procedure if I had general anesthesia available, which was usually the case.

Why Timing Is Important

Why is it important to do the surgery early? The main reason is that, even given a normal retina, a deep bilateral amblyopia quickly sets in, a failure to develop vision due to lack of essential stimulation of the entire visual system, and, by  extension, the entire body. Late treatment is preferable to no treatment, but once the infant develops nystagmus (searching movements of the eyes), which without cataract removal can occur within weeks of birth, the visual potential drops to the range of 20/200. This is still useful vision, but the ability to read without special aids is greatly limited, even if delayed surgery achieves a perfect result otherwise. If the rest of the visual system is normal, it is not uncommon for congenital cataract patients treated in a timely fashion to achieve virtually normal vision.

News on Plasticity

A news release from MIT1 is encouraging for all who deal with these somewhat tragic situations, since it gives hope that some visual plasticity remains, despite increasing atrophy affecting the entire visual system and the body’s proprioception sense (i.e., positional awareness, normally deeply dependent on visual cues).

Recent work from MIT Professor Pawan Sinha has shown that the picture is more nuanced than that. In many studies of children in India who had surgery to remove congenital cataracts beyond the age of 7, he has found that older children can learn visual tasks such as recognizing faces, distinguishing objects from a background, and discerning motion.

In a new study, Sinha and his colleagues have now discovered anatomical changes that occur in the brains of these patients after their sight is restored. These changes, seen in the structure and organization of the brain’s white matter, appear to underlie some of the visual improvements that the researchers also observed in these patients.

The findings further support the idea that the window of brain plasticity, for at least some visual tasks, extends much further than previously thought.

It is well known that even adult victims of congenital cataract get some benefit from surgery, but the longer they’ve been without treatment, the lower their visual potential. I would have to believe that at some age, little plasticity exists, an avoidable situation in most parts of the developed world.

Surgical Challenges

However and whenever the surgery is done, it presents some unique challenges. There may be other abnormalities of the eye, many now detectable in modern settings. The pupil may dilate poorly in an infant, necessitating some form of pupil expander during surgery (an easy proposition these days). Most surgeons put in an intraocular lens implant at the time of surgery, and calculating the desired power poses some unique challenges, particularly in Third World situations where one may not even have the advantage of ultrasound. In cases of bilateral cataract, I always did both eyes at once to avoid a second anesthetic risk.

There is still some debate as to whether surgery should be done on a monocular congenital cataract (where one eye is affected). The inclination these days seems to favor surgery for this problem as well. The thinking seems to go that even an eye requiring surgery and rehabilitation could, at some point in life, be the only eye if something happened to the good eye. Parents of such an individual should be thoroughly briefed regarding the aftermath of monocular surgery, since extensive amblyopia therapy is necessary to get a good visual result. It’s hard enough when one must treat a normal (but usually misaligned, or strabismic) eye. If the unoperated normal eye is not severely curtailed visually by patching, it will continue to dominate and nullify much of the improvement wrought by good surgery. It’s a battle that any parent who chooses surgery for one eye in their child must face. They need to be committed to a fight for success, for as long as it takes.

The Great Physician

I have written before about the miracle performed by Jesus Christ in healing a grown man who had been blind since birth (John 9). I’ve known of this healing for most of my life, but the awesome significance of what actually occurred didn’t dawn on me until I began my studies in ophthalmology. Jesus didn’t only heal the man’s eyes, he also had to reconstruct the man’s whole brain and nervous system (see my post of November 27, 2023). All these would have been in full atrophy, so much that visual areas of his brain and nervous system would have been nonfunctional.

Had Jesus healed only his eyes, the man would not have had fully developed proprioception so that visual cues could aid him in ambulation. He would have been unable to walk using visual cues, yet in the Bible story he appeared to be not a cripple, but a normal man to those around him. Considering that whole situation, a regular cataract in an otherwise normal eye becomes no challenge at all! But most of my patients who regained sight after losing it to cataract had fully developed nervous systems from a lifetime of use.

Professor Pawan Sinha commented on the work at MIT that was funded by the National Eye Institute:

“The notion that plasticity is a time-limited resource and that past a certain window we can’t expect much improvement, that does seem to hold true for low-level visual function like acuity,” Sinha says. “But when we talk about a higher-order visual skill, like telling a face from a non-face, there we do see behavioral improvements over time, and we also find there to be a correlation between the improvement that we are seeing behaviorally and the changes that we see anatomically.”

We will never be able to accomplish such a complete and total healing of an entire man. But the news of more plasticity than we thought was possible in older children is most welcome, and hopefully will improve our understanding and our efforts in the ongoing battle against blindness.

  1. Following cataract surgery, some of the brain’s visual pathways seem more malleable than previously thought. Anne Trafton, MIT News Office, May 1, 2023. https://news.mit.edu/2023/scientists-discover-anatomical-changes-brains-newly-sighted-0501

J.Y. Jones MD has been an eye physician and surgeon for five decades. He is a decorated Vietnam veteran, speaks Spanish, and has volunteered in 28 overseas eye-surgery mission trips. He has received numerous awards for writing and photography, and is a frequent speaker at sportsmen’s events, where he particularly enjoys sharing his Christian testi­mony. J.   Y. and his wife Linda have been married since 1964.

Dr. Jones is an avid hunter who has taken all North American big game species using the same Remington .30-06 rifle, resulting in the book One Man, One Rifle, One Land (Safari Press, 2001); Dr. Jones helped Safari Press produce the Ask the Guides series, their most successful North American hunting books. He has written 14 books and some 300 short articles for various periodicals. For more articles by Dr Jones, visit his Author Profile page.

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Categories: Human Body, Uncategorized

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