Congenital cataract is a condition in which the lens in the eyes of newborns becomes cloudy, significantly affecting their vision. The accumulation of proteins in the lens is the cause.
Dr Narpat Solanki, ophthalmologist at Dr Solanki Eye Hospital, Bengaluru, highlights the importance of early surgical intervention to preserve the child’s vision. Failure to address this issue within the first few months of birth can result in permanent blindness.
Challenging conventional beliefs is a recent study published in Proceedings of the National Academy of Sciences. This study demonstrates that individuals with congenital cataracts can regain their vision even when the surgery is performed during adolescence. It also reveals that the adolescent brain retains sufficient plasticity to change and adapt to partially compensate for abnormal visual development.
The study provides insights into the neural changes underlying the recovery of vision and highlights the potential for visual improvement even beyond the critical period.
Read more: Cataract: Signs, causes and treatment
Where there’s light, there’s vision
In congenital cataracts, the eye’s lens turns cloudy, affecting the reception of visual signals. When light falls on the eyes, the cornea (a transparent layer in the front of the eye) gathers the light, and the lens further converges the light rays. From there, the light goes to the macula [lutea] of the retina, where it transforms into electrical signals. Through the optic nerves, these electrical signals reach the brain’s occipital region, which helps in interpreting the visual signals.
But in the case of cataracts, the light scatters, causing hazy or blurred vision. In congenital cataracts, the macular cells are not stimulated to relay the visual stimulus to the brain, leading to blindness.
Prof Tapan K Gandhi, the lead author of the study from the Indian Institute of Technology, Delhi, says, “When a person has cataract from birth, parts of [his or her] vision pathways become defunct.”
Unveiling the brain’s potential
In this study, the researchers studied 7–17-year-old individuals with dense cataracts in both eyes. The participants were analysed through different stages of cataract surgery during their adolescence.
After the surgery, the researchers observed improvements in the structure of visual pathways connecting the occipital regions with the front-parietal-temporal regions on both sides of the brain. These pathways play a crucial role in visual information processing.
The visual function in congenital cataracts can be restored if the cataract is removed from the lens during the critical period. This is the time the visual system is sensitive to receiving and processing visual information. “This period is important because it is a time when the brain undergoes rapid changes and forms connections necessary for visual processing,” says Dr Gandhi.
If the visual system does not receive proper stimulation during this period, it can result in long-term deficits in visual acuity, depth perception, or other aspects of vision, explains Prof Gandhi. Earlier it was earlier thought that even after surgery in adolescents, the brain would be unable to use visual information from the eyes, he says.
Not too late
Additionally, the researchers found that the structural change in the brain influences visual abilities, such as:
- the ability to distinguish shapes and the details of objects (visual acuity) from a distance
- the ability to see the boundary of an object (contrast sensitivity)
- the ability to understand and interpret the face (face perception).
Prof Gandhi says that their study suggests that sufficient plasticity remains in adolescence to partially overcome abnormal visual impairment. This also helps to localise the sites of neural change underlying sight recovery.
The development process in our body is time-dependent, says Dr Solanki. “Early surgical intervention also proves successful to some extent. Later, after a certain period, if a person undergoes surgery, he or she may be able to see things, but partially, not completely, like a normal person,” he concludes.
Read more: Blindness: Types, causes and prevention
Read more: Everything you need to know to keep your eyes healthy
