Background info
Eyes are created from transparent, semitransparent, and opaque components to form their orbit-like structure. Healthy eyes should have a transparent passage of light rays so they could fall on a light-sensitive structure called the retina. The more clear the field in front of the retina, the better interpretation of the light and subsequently the more sharp vision. There are four structures in front of the retina that should be completely transparent to provide a full perception of the light. These structures are the cornea (the outermost layer), the aqueous humor, the lens, and the vitreous humor.
A natural eye lens is a transparent crystalline biconvex structure. The eye lens is suspended by multiple ligaments behind the iris of the eye. The sole function of the lens is to refract light falling on the eye from different distances and assist in collecting the light rays to fall at a single point on the retina. The core of the human lens is made of protein mainly collagen and crystallin. The protein filament forming the lens isn’t arranged haphazardly, yet they are arranged in a parallel and oval manner to provide the most transparency.
So, what is a cataract?
A cataract is defined as the development of any opacity within a transparent human lens, which will eventually limit the amount of precepted light and reduce eyesight. A cataract is one of the leading causes of blindness, especially for old people. The causes and risk factors of cataracts are various. However, the exact mechanism by which lens opacification is formed is yet debatable. Different theories are established to explain the pathophysiology (mechanism) of cataracts in the last 40 years. The most accepted theory explaining senile cataract (most common type) stated that lens opacification is a direct outcome of oxidative stress and the inability of the body to detoxify free radicals.
Cataract Surgeries Types
Cataract has different classifications. However, based on the cause of cataracts, it is classified into four main types.
1. Senile cataract is known as an age-related cataract, and it is the most frequent form of cataract representing the majority. Lens opacification can develop as you age due to natural changes in your eye’s lens. All elderly people are vulnerable to getting cataracts yet only genetically-susceptible patients develop a cataract. The etiology of senile cataracts is complicated, multifactorial, and not entirely understood. It is believed that multiple processes contribute to the gradual decrease of lens transparency. The life-long interactions between the human body and the surrounding environment and dietary habits also contribute significantly to the occurrence of senile cataracts.
Senile cataract has two subtypes: cortical and nuclear cataract.
● A nuclear cataract is a clouding and mudding of the lens center that causes blur, haziness, and other visual abnormalities. At the beginning of the course of the disease, patients could experience a slight improvement in their nearsightedness. However, by the time the lens becomes more thickly yellow or even brown and severely obscuring your eyesight.
● A cortical cataract is initially manifested as white, wedge-shaped opacities or streaks on the lens cortex ( outermost periphery of the lens). The streaks eventually extend to the center of the lens and interfere with light passing through it. Cortical cataracts affect night vision first as they limit peripheral vision. Both types of senile cataracts are insidiously progressive as patients may not feel that they are experiencing a reduction in their visual acuity.
2. A traumatic cataract
A traumatic cataract is the type of cataract that resulted from severe trauma to the eyeball.
A severe trauma could probably cause an eruption of the anterior or posterior capsule of the lens. Traumatic cataracts mostly appear just after trauma, yet they may take a few months to occur. Unfortunately, traumatic cataract is irreversible as other types of cataracts and require surgical intervention to restore vision.
3. A congenital cataract
A congenital cataract is a less common type of cataract. A pediatric cataract is usually caused by an intrauterine infection such as rubella. However genetic syndromes and congenital disorders can be associated with cataracts.
Congenital cataracts don’t essentially affect the vision but if it does, the baby’s lens should be replaced surgically. If a pediatric cataract is neglected and hasn’t been treated as soon as it significantly affects the eyesight, the patient develops an irreversible condition called amblyopia (lazy eye) in which the brain suppresses its perception of the image from the diseased eye.
4. A secondary cataract
It is a type of cataract that is caused by other well-known diseases or exposure. The most common cause of secondary cataracts is diabetes mellitus. It is found that cataract is a common finding in more than 50% of patients who had diabetes for a long period exceeding 10 years.
Steroid intake for a long period is believed to increase the risk of secondary cataracts. Not only do systemic steroid in oral pills or intravenous solution increases the probability of cataract development.
Cataracts could also develop secondary to longstanding hypertension. Secondary cataracts could even occur after cataract surgery as the posterior capsule in which the new lens is placed could be opacified.
Symptoms of cataract
Cataract patients usually describe their eyesight as seeing through clouded lenses and gazing through a frosty or fogged-up window. Cataracts can cause clouded vision, making it difficult to read, drive a car (particularly at night), or see the expression on a friend’s face. better lighting in the morning and eyeglasses can help you deal with cataracts at first, but they will eventually reduce your vision considerably and interfere with your activities.
Cataract advancement typically increases the dioptric ( refraction ) power of the lens, resulting in mild-to-moderate short-sightedness. As a result of so-called myopia (short-sightedness), presbyopic individuals who were unable to focus on near objects report improved near vision and decreased need for reading glasses. However, this is a transient phenomenon, and when the optical quality of the lens deteriorates, the visual acuity becomes very poor. Transient myopia associated with cataracts is not common in cortical and posterior subcapsular cataracts.
Double vision is a common complaint of patients with the initial stages of cataracts. Diplopia (double vision) of cataracts is usually monocular and caused by the perception of two images from one eye (the diseased one). The double vision of cataracts is believed to be caused by lens opacity separating the one point on the retina on which the collected light beam into two points. This condition could also be presented as halos around light. light sensitivity in patients with cataracts is found to be less common than the previously mentioned symptoms.
Complications of cataract
Cataract has a progressive course affecting the eyesight over time, yet it has no systemic affection. Therefore, cataract complications are limited to the ability of the eye to perceive light, as neglected cases of cataract is predisposed to a condition called amblyopia which is a medical condition in which the brain center responsible for image perception gradually stop perceiving image from the diseased eye and depend on the healthy eye. Complications of cataracts are predominantly resulting from its surgery such as retinal detachment, corneal injury, ocular hypertension, posterior capsular opacification …etc.
Risk factors of cataract
Cataract has different risk factors that increase the susceptibility to developing cataract. Most risk factors of cataracts are avoidable or controllable. However, senile cataract, as a result of aging, is more common in elderlies. Diabetic patients particularly those with unmanaged diabetes are at higher risk of getting cataracts.
Patients taking topical or systemic steroids for a long period are found to have a higher incidence of cataracts. Although the correlation between smoking and cataract isn’t fully understood, Cataract is prevalent among smokers. Overexposure to radiation or even direct sunlight is believed to induce lens opacities.
How is a cataract diagnosed?
Fortunately, cataract is so easily diagnosed. The primary examination of the eye is the inspection of the anterior compartment by a device called a slit lamp. A slit lamp is almost available in all ophthalmology clinics. An ophthalmologist will also assess the degree of cataracts and determine whether the patient will need surgery or not. Advanced lens opacification of cataracts could be seen by the naked eye without a slit lamp. The visual acuity test isn’t a specific test for cataracts, yet it assesses the sharpness of the vision. The more affected visual acuity, the more improvement the patient will have after surgery.
Treatment options for cataract
There are many cataract surgeries, but almost all of them involve removing the hazy lens and replacing it with an artificial one. Many patients may get concerned about having surgery on such a sensitive area. However, it is a quite safe operation in which you will be given a local anesthetic to numb your eye. During the operation, patients are awake but feel no pain. Moreover, cataract surgeries have a very high success rate estimated to be more than 94%.
Cataract surgery normally takes 15 to 20 minutes according to the ophthalmologist’s competence, experience, and how complicated the operation went. Cataract surgery isn’t considered a major surgery as patients don’t even have to stay in the hospital overnight. If you have cataracts in both eyes, your doctor will do surgery on the second eye when the first fully recovers. More than 95% of patients who underwent cataract surgery have experienced a significant improvement in their vision.
Phacoemulsification which is abbreviated as “phaco” is the most common cataract surgery nowadays. On the side of the cornea, the transparent, dome-shaped layer that covers the front of the eye, a tiny incision is created. A small probe is inserted into the eye by an ophthalmologist after applying topical anesthesia. This apparatus delivers ultrasonic waves that soften and break up the lens, allowing it to be suctioned out. The majority of cataract surgery is performed with phacoemulsification due it its high success rate and low invasiveness. Most phacoemulsifications don’t require suturing because its incision is so minimal.
Extracapsular Cataract Extraction (ECCE) is another type of cataract surgery in which the core of and the anterior capsule of the natural lenses of the eye are removed but the posterior capsule that holds the lens in place is left in place. This method involves a small incision, yet bigger than the incision of phacoemulsification. Therefore extracapsular cataract surgery is less common than phacoemulsification, especially in developed countries.
The surgeon creates a little incision in the outer border of the cornea or the sclera (white of the eye) towards the outer borders of the cornea during this surgery. The size of this is determined by whether the nucleus’s lens is to be removed in one piece or dissolved into smaller pieces and sucked away. After entering the eye through this incision, the surgeon delicately opens the anterior capsule of the lens and removes the nucleus of the lens. The doctor may need to suture the site of the incision if it wasn’t small enough to heal by itself.
Intracapsular cataract extraction (ICCE) is the least common cataract surgery performed nowadays. ICCE simply involves extraction of both lens nucleus and posterior capsule. Since the development of modern extracapsular techniques in the late 70s, the intracapsular cataract extraction method of lens removal has not been the procedure of choice in developed countries, owing to lower rates of postoperative complications such as retinal detachment, neovascular glaucoma, and cystoid macular edema. After intracapsular surgery, the incidence of neovascular glaucoma has been reported to be as high as 9%.
Types of lenses
After removal of the opacified lens, a new artificial lens called an intraocular lens (IOL) will be placed whether in the natural site of the lens or just behind the cornea (in front of the iris). The concept of the Intraocular lens is to provide the ideal refraction power to collect light rays at one point on the retina. IOLs are manufactured with different focusing powers to fit every eye perfectly.
Most IOLs are made of acrylic, silicone, plastic, or other polymers as synthetic implants. These materials are inert, meaning they do not react with your eye nor cause inflammatory responses. IOLs are covered with a layer of special material that shields your eyes from potentially harmful ultraviolet (UV) rays. unlike natural eye lenses, IOLs usually cannot accommodate their focusing power according to how far is the seen object. There are four main types of IOLs in the market, and each of them will be discussed separately.
1. Monofocal lenses are the standard and most common type of IOL implants used for cataract removal patients. They can provide significant visual assistance, but it is designed to focus light beams on a single focal point that typically covers a specific distance. It may be customized to concentrate on close work, medium-range, or distance vision, depending on your visual requirements. most patients choose to have it adjusted for clear distance vision; this is ideal for driving, biking, and viewing people from a distance. Reading or handcrafting usually requires the use of glasses.
2. Toric lenses are aimed to fix myopia (nearsightedness) with astigmatism as well as hypermetropia (farsightedness) with astigmatism. Toric lenses are typically used to correct astigmatism in eyeglasses, contact lenses, and intraocular lenses. Such a lens functions as a hybrid of a spherical and a cylindrical lens. Although choosing a toric lens may help fix astigmatism, patients who have this kind of IOL implant will still need to wear reading glasses for any close activities such as handcrafting, reading, writing, and typing.
3. A multifocal IOL is a better tool to enhance the outcome of cataract surgery. multifocal IOL helps correct vision for close, intermediate, and distant vision. You may use reading glasses for very tiny text and in low-light settings, but you should be able to do most of your regular tasks without them. If you are extremely nearsighted or have significant astigmatism, the multifocal IOL may not be suitable for you. Furthermore, multifocal IOLs should also be avoided if you have or are at risk of developing another eye illness such as glaucoma, papilledema, macular degeneration, or diabetic retinopathy. Multifocal IOLs are found to be associated with some optical side effects such as seeing halos and glare, so you may not enjoy it if you seek a perfect flawless vision.
4. Extended depth of focus IOL is a premium IOL created and developed by Abbott medical optics inc. (Now Johnson-Johnson Vision). This lOL was called TECNIS symphony and was approved by the FDA in 2016. Many ophthalmologists favor this type over monofocal and multifocal IOL because it has a better side effects profile than both of them. These lenses act by focusing light over a spectrum of vision rather than just in one spot. They do not divide light like multifocal lens implants which reduce the chromatic aberrations as halos. By elongating or “extending out” the focal point of the lens, the extended depth of focus lens provides a range of vision. doubtlessly, extended depth of focus IOL is the future of intraocular lenses. as it provides wide-ranged and excellent quality of vision with minimal cons.
Recovery
Recovery from cataract surgeries usually goes smoothly without complications. The duration of the recovery varies according to the type of operation you have and how it went. However, you will find that your vision improves significantly after a few days. After roughly a week or two, you can resume your normal activities. for a few people, post-operative lens opacification occurs as they get posterior capsule opacification following cataract surgery (PCO).
Because the capsule in your eye that holds the artificial lens in place thickens, your eyesight may become foggy again. This issue can be solved using YAG laser capsulotomy. PCO has no specific time of onset as it may occur 1 year after cataract surgery or maybe 10 years later. Recovery is an as important phase as the operation, you should set follow-up appointments with your ophthalmologist. If you experienced any abnormal symptoms such as redness, unclear vision, or attack of pain after cataract surgery, make sure to inform your doctor.
YAG laser capsulotomy
Laser capsulotomy is a minimally invasive procedure used to treat posterior capsular opacification in the eye using neodymium-doped yttrium aluminium garnet (Nd: YAG). Laser capsulotomy is performed by ophthalmologists trained to use the YAG laser. laser capsulotomy is a safe procedure and takes approximately 3 to 5 minutes. Mostly it is done on an out-patient basis after checking if there is an eye issue that may interfere with capsulotomy. Nd: YAG can be performed painlessly and comfortably using a topical anesthetic (anesthetic eye drops). The patient is asked to sit in front of a slit lamp with a YAG laser, then his opthalmologist will use the laser to make an opening through the opacified capsule. then the doctor will prescribe anti-inflammatory medication to reduce discomfort and speed up healing. 
Costs of the operation
The actual cost of cataract surgery for people without health insurance varies according to different factors, including the kind of intraocular lens (IOL), the type of the operation, and the surgeon’s experience. The average out-of-pocket expense for cataract surgery is $3,000 to $5,000 per eye. Monofocal IOLs are a bit inexpensive lenses, although toric and multifocal IOLs are more costly. Whereas, for those who have health insurance, most health insurance companies cover up to 80% of the costs of the procedure. The costs of YAG laser capsulotomy fluctuate in a range of 300 dollars in the US according to the state in which the procedure is performed. the average cost of laser capsulotomy is 1100 US dollars.