Cataract Surgery

Cataract surgery has made extraordinary and exciting advances over the past 20 years. Last year, approximately 2.7 million Americans underwent cataract surgery. Greater than 95% of those patients now enjoy improved vision. State-of-the-art cataract surgery is now a safe, effective, and comfortable procedure performed almost exclusively on an outpatient basis.

Most cataract surgeries are now performed using microscopic size incisions, advanced ultrasonic equipment to fragment cataracts into tiny fragments, and foldable intraocular lenses (IOLs) to maintain small incision size. Cataract surgery today is the result of extraordinary technological and surgical advancements that allows millions of people to once again enjoy crisp and clear vision. A true marvel of modern medicine, cataract surgery may restore vision to levels you may have never thought possible.

When a cataract is removed, it is replaced with an artificial intraocular lens (IOL). There are a variety of IOLs that can be used in cataract surgery, and they each have their own set of advantages and disadvantages. No single IOL works best for everyone, and only your ophthalmologist can determine the most appropriate IOL for your needs. The FDA approval process for IOLs is among the most rigorous in the world. You can rest assured than any IOLs used in the U.S. have undergone very extensive testing for safety and efficacy. These same IOLs are also used for a refractive surgery procedure known as refractive lens exchange. In refractive lens exchange, the IOL is used solely in an attempt to reduce or eliminate the need for glasses or contact lenses. This article outlines some of the choices of IOLs that are available for use in cataract surgery and refractive lens exchange.

Fixed Focus Monofocal IOLs are used in the majority of cataract procedures. These lenses have the advantage of excellent quality distance vision under a variety of lighting conditions. Since these lenses have a fixed focal point which is generally set for distance vision, reading glasses are typically required for good near vision. For patients willing to use reading glasses for near tasks, these IOLs are an excellent choice. Several million lenses of this variety have been used for decades with an excellent safety record. Recent refinements in the optical quality of these lenses have allowed an even higher quality of vision than previously achievable.

Accommodating Monofocal IOLs are used in situations where both good distance and good near vision are desired without the use of spectacles. These IOLs have a single focal point, however, the focal point can shift position in space so that objects at distance are clear when the eye focuses on them, but when the eye looks at a near object the IOL will shift its focal point to bring the near object into focus. Accommodating Monofocal IOLs achieve this by physically moving inside the eye in response to the focusing action of the muscles of the eye. The only FDA approved IOL of this type is called the Crystalens™. Patients implanted with the Crystalens IOL generally enjoy near vision without glasses that is much better than those implanted with Fixed Focus Monofocal IOLs(2). In fact, results of the FDA trial for the Crystalens demonstrated that 98% of patients could see well enough to pass the driver's test and read a newspaper without glasses. Vision at the intermediate (computer screen) distance is superb with the Crystalens, making this an excellent IOL for those who spend a great deal of time on a computer.Cataract surgery today is typically performed using a microincisional procedure. To the patient, this means minimal discomfort during or after surgery, a more speedy recovery of vision, and reduced risk of induced astigmatism. This means less dependence on glasses afterwards.

Below, we've detailed the major steps of cataract surgery using a microincision procedure, phacoemulsification (ultrasonic cataract removal), and a foldable lens implant. This type of procedure is considered state-of-the-art for cataract surgery today. The procedure demonstrates basic principles only, however, and eye surgeons use many variations of the general theme, even from one case to another, depending on the type of cataract being removed. After discharge from the surgery center, patients will usually be asked to return for a follow-up visit later that day or the next day, however, this will be based on individual circumstances. Also depending on the type of incision and surgeon preference, some patients will be asked to wear a shield over the eye, particularly while sleeping. The eye should not be rubbed, or pressure placed directly on the eye through the eyelid, during the first few weeks following surgery. Eye drop medications will be required, usually consisting of antibiotic and anti-inflammatory medicines. These will often be tapered off during the first month after surgery.

The best vision may not be obtained until several weeks following surgery, but individual results vary considerably, depending on many variables. The great majority of patients may resume normal activities on the day of or day after surgery. Activities such as reading, watching television, and light work will not hurt the operated eye. Most surgeons arbitrarily recommend waiting 4 to 6 weeks before new glasses are obtained. This allows the eye to achieve considerable stability from a refractive standpoint and, therefore, the glasses prescription should be accurate and relatively stable.

Many patients are surprised at how clear their vision is after cataract surgery. Some patients may have better vision than they ever did before cataract surgery. Furthermore, depending on the degree of refractive error (need for glasses) prior to surgery, many patients will be much less dependent on glasses for far vision than they were before surgery. Patients will often notice that colors are brighter and more brilliant. The results are often dramatic.

Cataract

When the lens of the eye is clouded with protein lumps, it forms a smoky screen called a cataract. A cataract tends to grow larger over time and cloud most of the eye's natural lens. Due to the cloudiness, the lens is not able to transmit clear pictures to the retina and vision is affected. Age-related cataracts are the most common type of cataracts that are observed. A nuclear cataract is formed in the center of the lens and is part of the natural aging process. A cortical cataract develops in the lens cortex and gradually extends towards the lens. This is noticed largely among patients suffering from diabetes. They are also likely to develop subcapsular cataract that forms at the back of the lens. Some babies are born with congenital cataracts. Secondary cataract develops as a result of diabetes or other diseases or medications. Cataract does not spread from one eye to the other and does not cause permanent blindness.

A person suffering from cataract will notice slightly blurred vision. Most of the symptoms of cataract depend on the type of cataract that has occurred. While a patient suffering from subcapsular cataract may not notice any symptoms, a nuclear cataract can give rise to a temporary improvement in vision followed by worsened condition. Symptoms associated with cataract are blurred vision, light sensitivity and poor night vision. The cloudiness over the lens depends on the amount of cataract and its location. If it is near the center of the lens, vision is badly affected. A patient suffering from cataract may not be able to notice colors brightly and may complain of double vision.

Cataract surgery is the only treatment for cataracts. It has a high success rate in restoring good vision to cataract patients. Ophthalmologists are of the opinion that long-term unprotected exposure to sunlight's UV rays may be a cause for formation of cataracts. Other risk factors include cigarette smoke and air pollution. Eating a diet high in antioxidants, vitamins C and E may play a role in keeping cataracts at bay.

Ultrasound

Ultrasonography is a medical imaging technique that is also called ultrasound scanning or sonography. High frequency sound waves and their echoes and used in this technique for obtaining images from inside the human body. The echoes of sound waves reflected from the human body are recorded and displayed as a real-time visual image. This technique is similar to the echo location used by bats, whales and dolphins. The sonar used by submarines also operates with the same technique. Ultrasound is useful method to examine many of the body's internal organs like heart, liver, gallbladder, spleen, pancreas, kidneys and bladder.

Ultrasound Scanning

1. Sound Waves: A transducer (a small handheld device) emits high-frequency sound waves.
   
2. Echoes: These sound waves bounce off tissues, organs, and other structures inside the body.
   
3. Image Formation: The transducer detects the echoes and sends this information to a computer, which creates images based on the patterns of the echoes.
   

Types of Ultra sound:

1. Abdominal Ultra sound: Evaluates organs in the abdomen, such as the liver, gallbladder, spleen, pancreas, and kidneys.
   
2. Pelvic Ultra sound: Assesses reproductive organs (uterus, ovaries) and bladder.
   
3. Obstetric Ultra sound: Monitors pregnancy and fetal development, to assess the risk of fetal abnormalities such as neural tube defects or Down's syndrome
   
4. Cardiac Ultrasound (Echocardiogram): Evaluates heart structure and function.
   
5. Doppler Ultra sound: Measures blood flow through vessels.
   
6. Musculoskeletal Ultra sound: Examines muscles, tendons, and joints.
   
7. Thyroid Ultra sound: Evaluates the thyroid gland.
   

Preparation:

• Fasting: May be required for certain abdominal ultrasounds.
  
• Full Bladder: Often necessary for pelvic ultrasounds.
  
• Loose Clothing: Wear comfortable, loose-fitting clothes for easy access to the area being examined.
  

Procedure:

1. Preparation: The patient may be asked to lie on a table and expose the area to be examined.
   
2. Application of Gel: A special gel is applied to the skin to help transmit sound waves.
   
3. Transducer Use: The healthcare provider moves the transducer over the area, capturing images.
   
4. Image Review: The images are reviewed in real-time, and the provider may take multiple images from different angles.
   

Benefits:

• Non-Invasive: No needles or incisions.
  
• Safe: Uses sound waves, not radiation.
  
• Real-Time Imaging: Allows dynamic assessment of moving structures.
  
• Widely Available: Accessible in most healthcare settings.
  

Applications:

• Diagnosis: Identifying and evaluating various medical conditions.
  
• Monitoring: Tracking the progress of diseases or conditions.
  
• Guidance: Assisting in procedures such as biopsies or fluid drainage.
  

Common Uses:

• Pregnancy Monitoring: Checking fetal health and development.
  
• Organ Assessment: Evaluating the liver, kidneys, and other organs.
  
• Cardiac Evaluation: Assessing heart function and detecting abnormalities.
  
• Blood Flow Analysis: Checking for blood clots or poor circulation.
  
• Musculoskeletal Issues: Diagnosing tendonitis, bursitis, or tears.
  

Ultrasound examinations are versatile and essential tools in modern medical diagnostics, providing crucial information for the diagnosis and management of many health conditions.

Carotid Doppler ultrasound scanning is a diagnostic method used to assess blood flow through the carotid arteries, which are the primary vessels supplying the neck and head. This non-invasive modality is employed in the evaluation of various conditions, including:
1. Carotid artery stenosis (narrowing) - a common finding associated with increased risk of stroke. Doppler echocardiography image reveals any narrowing of the arteries or turbu￾lence in blood flow.
Echocardiography is a diagnostic tech￾nique used to evaluate structural and functional abnormalities of the heart including:
1. Heart wall: Detecting changes in thickness, texture or motion.
2. Heart chambers: Assessing size, shape, and function.
3. Heart valves: Evaluating valve leaflet movement, regurgitation and stenosis.
4. Large coronary arteries: Identifying narrowing or obstruction.
In addition to detecting cardiovascular lesions, echocardiography is also employed in the diagnosis of:
1. Congenital heart disease: Abnormalities present at birth.
2. Cardiomyopathy: Heart muscle disorders characterized by impaired function.
3. Aneurysms: Ballooning or dilation of the heart or blood vessel walls.
4. Pericarditis: Inflammation of the pericardial sac surrounding the heart.
5. Blood clots in the heart: Emboli that may have originated from other sources and traveled to the heart.

2. Transient ischemic attacks (TIAs), also known as "mini-strokes" or "warning strokes" - a temporary loss of blood flow to the brain.
3. Stroke - a neurovascular event characterized by permanent disruption of blood flow to the brain.
Doppler echocardiography is a valuable diagnostic tool that enables the measurement of blood flow velocity (speed) within the heart. This modality allows cardiologists to:
1. Assess structural abnormalities: Such as mitral valve prolapse, where the mitral valve leaflets protrude into the left ventricle.
2. Evaluate septal defects: Abnormal openings in the septum that separate the right and left sides of the heart.
By analyzing blood flow velocity, Doppler echocardiography can help diagnose and monitor various cardiovascular conditions, including those affecting the heart valves and septum.

Cataract Surgery: An ultrasound probe is inserted into the lens capsule through a small incision in the cornea. The incision is made using a diamond tipped instrument. The ultrasound probe softens the lens by emitting sound waves. It then sucks out the softened lens tissue. Only the front part of the lens capsule is removed.

Doppler ultrasound is a type of echocardiography that utilizes the principles of Doppler shift to measure the velocity of moving structures. This technique involves transmitting high-frequency ultrasonic waves from an emitter and detecting the frequency changes resulting from the interaction with moving targets, such as blood flowing through a blood vessel.
Doppler ultrasonography has become a widely accepted diagnostic modality for detecting various vascular conditions. Specifically, it is commonly employed to:
1. Identify arterial narrowing or stenosis in the neck, often resulting from atherosclerosis (the accumulation of fatty deposits on artery walls).
2. Detect blood clots (thrombi) within veins, as seen in deep vein thrombosis.
In addition to its vascular applications, Doppler ultrasound is also used for:
1. Fetal monitoring: To non-invasively assess fetal heart rate and detect any potential abnormalities.
2. Dialysis and cardiopulmonary bypass procedures: To monitor for air emboli (air bubbles) that may form during these interventions.
3. Blood pressure measurement: As a non-invasive means to estimate blood pressure, particularly in situations where direct measurement is not possible or practical.
The process begins with the emission of pulses of ultrasound at a specific frequency. As these pulses interact with moving objects, such as red blood cells in a vessel, the frequency of the reflected signals (echoes) shifts due to the Doppler effect. A sensor detects these frequency changes and converts them into meaningful data, providing valuable information about the velocity or flow characteristics of the target structure, for example, blood flow through an artery or vein.

Ancillary term used in ultrasound imaging to describe an anechoic region or structure that does not produce any reflective echoes (sonographic signals) when exposed to ultrasound waves. This is typically seen in structures containing clear fluid, such as:
1. Cysts: Fluid-filled cavities that do not reflect ultrasound signals.
In these cases, the lack of echogenicity allows for better visualization and differentiation from surrounding tissues.
"Echogenic" - A descriptive term used in ultrasound imaging to identify structures that produce reflective echoes or signals when exposed to ultrasound waves. In other words, an echogenic structure is one that generates a strong sonographic signal, allowing it to be visualized and characterized on the ultrasound image.

The frequency of ultrasound waves used in medical imaging varies depending on the type of examination and the depth of the tissue being imaged. Here are some general guidelines:

Common Frequencies:

1. General Diagnostic Ultrasound:
   • Frequencies typically range from 2 MHz to 15 MHz.
     
   
   
2. Abdominal Ultrasound:
   • Lower frequencies around 2 MHz to 5 MHz.
     
   • Lower frequencies provide deeper penetration but lower resolution.
     
   
   
3. Pelvic Ultrasound:
   • Frequencies typically in the range of 3 MHz to 7.5 MHz.
     
   
   
4. Obstetric Ultrasound:
   • Frequencies around 2 MHz to 5 MHz for deeper penetration to view the fetus.
     
   
   
5. Cardiac Ultrasound (Echocardiogram):
   • Frequencies typically range from 2.5 MHz to 5 MHz.
     
   
   
6. Vascular Ultrasound:
   • Frequencies around 5 MHz to 10 MHz.
     
   
   
7. Musculoskeletal Ultrasound:
   • Higher frequencies around 7.5 MHz to 15 MHz.
     
   • Higher frequencies provide better resolution for superficial structures.
     
   
   
8. Small Parts (Thyroid, Breast, Scrotal):
   • Frequencies in the range of 7.5 MHz to 15 MHz.
     
   
   

• Penetration vs. Resolution: Lower frequencies penetrate deeper into the body but produce images with lower resolution. Higher frequencies provide higher resolution images but do not penetrate as deeply.
  
• Tissue Characteristics: Different tissues reflect sound waves differently, so the frequency is chosen based on the specific characteristics and location of the tissue being examined.
  

Specific Frequency Ranges:

1. 2-3.5 MHz: Deep structures like the liver, kidneys, and heart.
   
2. 3.5-5 MHz: General abdominal and obstetric imaging.
   
3. 5-7.5 MHz: Breast, thyroid, and vascular imaging.
   
4. 7.5-10 MHz: Musculoskeletal and superficial structures.
   
5. 10-15 MHz: Very superficial structures and detailed imaging of small parts.
   

Normally the term ultrasound refers to frequencies above 20 kHz (the maximum frequency a human can hear), medical ultrasound utilizes frequencies in the range of several MHz to achieve the necessary balance between resolution and penetration for effective imaging of different tissues and organs.

As you can see from the table above, specific band of frequencies are chosen for optimal imaging.

• Resolution: Higher frequencies provide better resolution, allowing for more detailed images of tissues and structures.
  
• Penetration: The choice of frequency is a trade-off between penetration and resolution. Lower frequencies penetrate deeper but have lower resolution, while higher frequencies provide detailed images of superficial structures.
  

Movement of the internal tissues and organs are captured in ultrasound. Ultrasonography enables the physicians to diagnose a variety of disease conditions and also assess the damage caused to the systems. The ultrasound machine transmits high frequency sound pulses into the human body by using probes. These sound waves that travel into the body hit a boundary between the tissues inside the body and reflect the sound waves to the probe. Some waves travel even further and they reach another boundary and then get reflected back. The waves that are reflected are picked up by the probe and relayed back into the ultrasound machine.

The ultrasound machine in turn calculates the distance from the probe to the tissue or organ by using the speed of sound tissue and the time of each echo's return. The machine displays these distances and intensities of the echoes on the screen. Through the echoes that are produced the sonologist can identify how far away an object is, how large it is, its shape and consistency (fluid, solid or mixed). Two dimensional images are formed and reflected on the screen. Different types of ultrasound are used for different disease conditions. Ultrasound is used in a variety of clinical settings including obstetrics and gynecology, cardiology and cancer detection.