INTRODUCTION:

The most common reason for blindness in older individuals worldwide, particularly in developing nations, is cataract¹. An estimated 20 million people worldwide are blinded as a result of aging-related cataracts. When cataracts interfere with daily life, surgery to replace the hazy lens with an artificial lens has emerged as the gold standard for treating the condition². However, the operation is not always an accessible medical option, particularly in low- and middle-income nations. Additionally, cataract surgery can have a negative impact on patients' quality of life and lay a heavy burden on healthcare systems by increasing the likelihood of vision-related concerns including posterior capsule opacification, particularly in newborns and young children^3-5.

Uncorrected refractive error was the main global cause of moderate to severe visual impairment, followed by cataract, and cataract was the leading global cause of blindness overall. From 1990 through 2010, this frequency-based ranking remained constant. However, when the causes of blindness were examined regionally, significant disparities became clear. Cataract-related blindness rates in 2010 ranged from 15% or less in high socioeconomic areas to >40% or more in south and southeast Asia and Oceania^6,7. Similar to blindness, wealthier socioeconomic regions had the lowest percentage of moderate to severe vision impairment brought on by cataract (13.0–13.8%), whereas south and southeast Asia had the highest incidence (both >20%).

Oxidative damage to the eye lens is believed to be a key factor in the beginning and development of cataracts, even if the nosogenesis of cataract is unclear⁸. Different kinds of cataract formation have been linked to a number of highly reactive oxygen species (ROS), including hydrogen peroxide (H₂O₂), superoxide anion (O₂), nitric oxide (NO), and hydroxyl radicals (OH^-). Therefore, a lot of work has gone into finding potent antioxidative pharmacological drugs⁹.

On the level of public health, doctors and ophthalmologists view cataract-related blindness as a challenging problem. Surgery is the only way to treat it, which places a heavy financial strain on society. Therefore, strategies have been developed to lessen the impact of this problem by identifying and maybe altering elements that will result in the prevention of the disease, or at the at least, delay it (up to 10 years). This was observed to result in a 45% or more reduction in the frequency of procedures¹⁰. Therefore, when it comes to cataract, attempts have been made to concentrate on preventive medicine.

Various types of cataracts:

1. Pediatric cataract:

One of the most significant surgically curable causes of infant blindness is pediatric cataract. Treatment of pediatric cataract has a significant social impact since it can prevent "lost years of blindness." There are many known morphological types, but zonular has the best visual prognosis.

The morphology of the cataract is significant for a number of reasons, including the age at which it first appears, heredity, and causation, as well as its potential significance for visual prognosis. Lamellar cataracts and posterior lenticonus fare better than other morphological forms, although thick central cataracts perform very poorly. Trisomy 21, acute metabolic cataracts, and congenital rubella all cause total cataracts that almost completely cover the lens, but they can also occur in familial or sporadic cases.

The outer zones of the lens liquefy while the nucleus of congenital Morgagnian cataracts is unaffected. The nucleus can now descend by gravity in any direction, depending on where the head is located. The final step of the lens' re-absorption is represented by membrane cataracts, which either leave a disc of lens material or merged anterior and posterior capsules. It is frequent in PFV, trauma, congenital rubella, and PFV. The most typical kind of congenital cataract is the zonular cataract. It affects one or more lens zones or layers. These cataracts are typically inherited as an autosomal dominant trait or idiopathic.

They often consist of a layer of tiny white dots in one or more layers of the lens and are bilateral but slightly asymmetrical. Although occasionally involving the foetal nucleus and having clear I, cortex outside of them, the embryonic nucleus is spared. There is frequently significant intra- and inter-ocular variation. Morphologically, a cataract is frequently incomplete and may have what are referred to as "riders" on the edges. The visual prognosis is better than in many other morphological kinds, particularly in partial cataract.

A specific variety of zonular cataract known as a sutural cataract is marked by opacities that surround or involve the sutures. The variations, which are frequently familial, range from an increased suture density to a variety of whitish or cerulean dots grouped around one or both sutures. If they don't reach the nuclear stage, they are visibly unimportant. The anomalies of lens vesicle detachment are anterior polar and anterior pyramidal cataracts. Compared to anterior polar cataracts, anterior pyramidal cataracts are more likely to progress and be visually prominent. They could separate, creating an anterior chamber foreign body. The condition known as anterior lenticonus can be spontaneous or connected to other diseases. Alport's syndrome is characterised by bilateral anterior lenticonus. It can be a symptom of a problem with the basement membrane. About 10% of young children with it have a congenital condition, although its prevalence might rise to 30% over time.

The posterior lens capsule thins and bows in the back due to posterior lenticonus, which can be unilateral, bilateral, or asymmetrical. The patient may either lack a cataract or have a high degree of astigmatism, which is frequently irregular. If cataracts are present, they could be localised or progressive. Unlike anterior lenticonus, it rarely has any systemic illness associated with it. It may be autosomal dominant, sporadic, or X linked.¹¹

There are various cataract types and causes in children.

· A child's cataracts may be acquired or congenital (existing at birth) (develop as an infant, child, or adolescent).

· One or both of the eyes may develop cataracts. One cataract may be worse than the other when there are two.

· Cataracts can range in size from microscopic spots to dense clouds and can occur in various locations on the lens.

· Cataracts can be brought on by genetics, metabolic conditions including diabetes, and ocular trauma.¹²

2. Age related cataract:

Age-related cataract, also known as senile cataract, is a cataract that develops in adults over 50 without being caused by recognised mechanical, chemical, or radiation stress. In the aged, it worsens and occurs more frequently¹³.It is classified as:

a. Nuclear cataract:

As the lens ages, additional layers of fibres are added, the lens nucleus is compressed and hardened (a condition known as nuclear sclerosis cataract), and the lens also turns yellower as a result. Nuclear sclerosis develops gradually over many years. In other situations, it has only a minor impact on vision or results in a myopic shift, also known as second sight because reading glasses may no longer be required. Further advancement can lead to loss of eyesight, usually more at a distance than up close, as well as loss of color differentiation.

b. Cortical cataract:

The most recent lens fibres make up the cortex of the lens. With age, no fibres are lost, and new fibres are introduced to the lens' exterior, hidden beneath the lens' outer coating or capsule. When the visual axis or the entire cortex is affected, the lens turns white and is referred to as mature. Discrete opacities (cortical spokes) can form within the lens cortex with age but usually do not cause any visual symptoms.

c. Posterior sub capsular cataract:

Granular opacities known as cataracts mostly affect the central posterior cortex, right behind the posterior capsule. They can occur in younger individuals, are frequently accompanied by glare complaints, such as when driving at night, and tend to impair near vision more so than far vision.¹⁴

The lens will become thicker and heavier as it ages, which are the most noticeable changes. With age, a diffusion barrier forms between the lens nucleus and the nutrients and endogenous antioxidants that are given by the lens cortex and epithelium due to the lens nucleus' ongoing expansion. Existing cells are not biodegraded as a result of the absence of protein turnover, and lens proteins, especially the older ones found in the nucleus, are susceptible to PTMs like deamidation, glycation, phosphorylation, loss of bound water, cross-linking, and protein aggregation. Additionally, if the coloration is sufficiently dense, it might lead to an age-related nuclar cataract. This coloration of the lens is caused by the accumulation of chromophores and fluorophores.¹⁵

3. Diabetic cataract:

The prevalence of diabetes mellitus (DM), a chronic systemic disease, has risen over time. All ocular structures may be impacted by DM, with cataract being the most frequent ocular complication. The most common reason for blindness in the world is cataract. The incidence of cataract formation is higher in the diabetic population due to a number of causes.

a. Pathway for polyol:

A hyperosmotic effect caused by the increased intracellular sorbitol buildup causes hydropic lens fibres to degenerate and produce cataract. Compared to non-diabetic patients, diabetes patients produce sorbitol more quickly than the enzyme sorbitol dehydrogenase can break it down into fructose. Because sorbitol is polar, diffusion-based intracellular clearance of the substance is also avoided. When sorbitol builds up and fluid is infused, the consequence is a hyperosmotic reaction. The production of lens opacities is caused by the liquefaction of lens fibres caused by the intracellular accumulation of polyols.

b. Oxidative and osmotic stress:

Another contributing factor in the rapid development of cataracts, particularly in young individuals with type 1 DM, is osmotic stress brought on by the considerable swelling of the cortical lens fibres. The major location of protein synthesis, the endoplasmic reticulum (ER), is stressed by osmotic stress brought on by the buildup of sorbitol, which creates free radicals. An unfolded protein response that results in reactive oxygen species and damages lens fibres under oxidative stress is another factor that can lead to stress in the ER. Additionally, elevated glucose levels in the aqueous humour can cause lens proteins to glycate, which creates advanced glycation end products. Hydroxyl radicals (OH-) are also generated after entering the lens as a result of Fenton reactions brought on by high levels of hydrogen peroxide (H₂O₂) in diabetics' aqueous humor. Free radical nitric oxide (NO•), which may promote peroxynitrite generation and contribute to cell damage due to its oxidising capabilities, is another component that is raised in the lens and aqueous humour of diabetes patients. However, because of their reduced antioxidant capacity, diabetic lenses are more vulnerable to oxidative stress. The most prevalent antioxidant enzyme in the lens that converts superoxide radicals (O₂-) into H₂O₂ and oxygen is called superoxide dismutase (SOD).¹⁶

Diagnosis of cataract:

An eye exam that may include the following investigations can determine the degree of visual deterioration that represents the asperity of the cataract.

· Refraction test: This test determines whether wearing glasses can improve vision.

· Visual acuity test: A visual awareness eye test is the same as the yearly eye exams that an ophthalmologist performs on everyone. The ability to read letters of gradually smaller sizes is tested individually for each eye using a viewing device or an eye chart. The doctor can determine how much the cataract has impacted vision using this technique. Visual aptitude is a gauge of how well someone can see.

· Testing of contrast sensitivity: Tests for visual acuity and contrast sensitivity are similar, but contrast sensitivity testing more clearly demonstrates how cataracts reduce image contrast due to light glare and scattering. This test is based on the ability to distinguish between different shades of grey because a cataract may impair this ability.

· Testing for color vision: Aids in identifying acquired color vision defects that may be present in cataract patients.

· Testing for glare: Different lighting conditions, such as at night and in blazing sunshine, can alter vision. By having a patient read the chart twice, once with and once without bright lights, these marks can be determined under various types of lighting.

· Potential acuity testing: A test that provides a rough idea of what the vision will be like after cataract surgery and is interpreted as the eye's vision power in the absence of a cataract.

· Spectacular photographic microscopy: A specialized microscope is used to take a picture of the endothelial layer of the cornea. This is typically done in advance of cataract surgery to assess the endothelium's condition, which could have an impact on the procedure's outcome.

· Retinal examination: Eye drops are used to dilate the pupils prior to the retinal examination so that the retina can be seen more clearly. To detect cataracts, macular degeneration, glaucoma, and other issues with the optic nerves and retina that may be the source of vision loss, an ophthalmoscope or slit-lamp is used.

· Slit-lamp examination: Conducted using a specialized microscope called a slit-lamp that shines a powerful, thin beam of light into the eye to provide an enhanced three-dimensional view of the interior of the eye. The structures at the front of the eye, such as the iris, cornea, and lens, as well as the region between the cornea and iris, can all be examined in section by manual detection in order to look for any abnormalities.

· Tonometry: Using a specialized instrument, a test can be performed to determine the intraocular pressure (IOP), or pressure inside the eye. Injected eye drops are an option.¹⁷

Management of cataract:

When a cataract affects visual function, it is necessary to replace the clouded crystalline lens with an IOL that has the right refractive power in order to restore the transparency of the optical pathway. Due to our ability to measure the optical parameters of the eye, sophisticated technologies to remove the cataract, and ongoing advancements in IOL design, current surgical techniques achieve these goals with accuracy, reproducibility, and safety. The majority of the surrounding clear lens capsule is preserved during extracapsular cataract surgery in order to support the IOL indefinitely. To suspend and support the lens, zonules (microscopic ligaments) affix and insert circumferentially onto the lens capsular equator. The large, firm lens nucleus and the softer surrounding cortex are removed following creation of a central opening in the anterior capsule. The IOL is then positioned anterior to the remaining clear posterior capsule within the vacated capsular bag.

· Various surgical techniques:

1. Phacoemulsification:

In order to break up the rigid lens nucleus, phacoemulsification uses ultrasonic energy to vibrate a titanium needle at high frequencies. The resulting emulsate is aspirated from the eye at the same time. Phacoemulsification was first developed by Charles Kelman in the late 1960s. The advantage of using phacoemulsification over only manual techniques is the ability to remove the large nucleus through a 3.0mm-long incision. Then, through this small incision (which is typically not necessary to be stitched) foldable IOLs are implanted. Surgery can now be performed through 2.2 mm mini-incisions or 1.8 mm micro-incisions thanks to advancements in equipment and needles. However, using micro-incisions necessitates the use of unique IOLs. Smaller incisions have many benefits, including the ability to use topical anaesthesia rather than local injection anaesthesia, especially if the incision is made in the peripheral cornea, better intraocular environment control, increased safety should the patient move, quick restoration of the incision's structural integrity, reduced post-operative physical restraints, and a reduced risk of corneal shape changes. Phacoemulsification has been the industry standard in developed nations for more than 20 years due to its ability to reduce astigmatism and speed up physical and visual rehabilitation. Cost and other factors influence the prevalent use of manual techniques in developing nations. Phacoemulsification and other surgical technology advancements have increased the safety and reproducibility of small incision cataract surgery, though they do not replace a surgeon's unique surgical skill. The nuclei of the most advanced cataracts, which have larger and harder nuclei, are a case in point. The development of surgical microscopes has been crucial, as with any microsurgery. Additionally, improvements are made in viscoelastics, transparent viscous gels the surgeon uses to shield the intraocular structures from trauma during surgery. The risk of corneal decompensation (corneal oedema brought on by the corneal endothelium's inability to keep the cornea relatively dehydrated) has decreased as a result of improved viscoelastics. The advantages of using femtosecond laser technology to automate some surgical procedures are being assessed. The majority of IOLs are made of silicone or acrylic plastic, which allows the lens to be folded. The initial goal of IOL research was to create the safest design. To further improve the optical properties, more developments were made. Modern IOLs prevent secondary posterior capsule opacification, reduce unwanted optical spherical aberration, and block UV light. IOLs are available in a variety of refractive powers, just like other corrective lenses. Toric lenses and multifocal lenses are two new IOL designs that address astigmatism and presbyopia to lessen the need for glasses. Surgery to remove cataracts has become one of the most popular refractive procedures thanks to modern technology and IOLs. Other tools, such as iris retractors, pupil expansion rings, capsule retractors, and capsular tension rings, help difficult eyes with smaller pupils or abnormal zonules undergo successful surgery. Finally, the success rate with mature white cataracts has increased thanks to dyes that stain and make the anterior capsule more visible.

Fig. No. 1 Phacoemulsification¹⁸

Fig.No. 2 MSICS as well as modified MSICS ¹⁹

2. Msics as well as modified msics:

In the developed world, phacoemulsification is the gold standard for cataract removal. However, using it in societies that are less developed economically raises a number of problems. Compared to manual methods, it requires a significant initial investment in the phacoemulsification equipment and much higher ongoing costs for medical supplies. In developing nations, the expense and level of expertise required for equipment maintenance is also a concern. Additionally, phacoemulsification requires more time and effort to learn than manual cataract surgery, and developing nations may not have the necessary teaching resources or facilities. Last but not least, the manual technique is preferable for treating hard and mature cataracts, which are more prevalent in underprivileged populations.

As a result, alternative surgical methods for cataract surgeries in developing nations have been developed. A sutureless M-SICS technique is the most widely used. Sutureless large incision manual cataract extraction (SLIMCE) is one of the MSICS technique modifications that is becoming more and more popular, particularly in China. All of these adjustments make use of a longer, sutureless scleral tunnel incision to reduce astigmatism and quicken the physical and visual recovery, as well as a larger incision to increase the safety of cataract removal. Compared to phacoemulsification, MSICS produces excellent results at a lower cost and faster surgical time. Aside from being quick and inexpensive, MSICS is also simpler to learn for novice surgeons and, in their hands, is safer for advanced mature cataracts. Additionally, MSICS rarely results in dropped nuclei, a serious side effect of cataract surgery that involves the nucleus dislocating onto the retina. If this complication is not properly managed by a vitreoretinal specialist, a rare subspecialty in many developing nations, it has a poor prognosis. Phacoemulsification and MSICS are both risk-free and offer superior visual results.²⁰

CONFLICT OF INTEREST:

The authors have no conflicts of interest regarding this investigation.

ACKNOWLEDGMENT:

We are thankful to PDEA’s Seth Govind Raghunath College of Pharmacy, Saswad, Pune, Maharashtra, India for providing laboratory facility for this research work.

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Received on 09.05.2023 Modified on 18.07.2023

Asian J. Pharm. Res. 2024; 14(1):77-82.

DOI: 10.52711/2231-5691.2024.00012

Vaishnavi Pradeep More¹*, Pradnya Nilesh Jagtap², Sumit Kailas Musale³,

Ankita Mahadeo Kadam⁴, Shweta Shivaling Bobade⁵, Komal Dattatray Pol⁶

Vaishnavi Pradeep More1*, Pradnya Nilesh Jagtap2, Sumit Kailas Musale3,

Ankita Mahadeo Kadam4, Shweta Shivaling Bobade5, Komal Dattatray Pol6

Vaishnavi Pradeep More¹*, Pradnya Nilesh Jagtap², Sumit Kailas Musale³,

Ankita Mahadeo Kadam⁴, Shweta Shivaling Bobade⁵, Komal Dattatray Pol⁶