Mechanism of Cyclocryotherapy

Mechanism of Action

Cyclocryotherapy presumably destroys the ability of ciliary processes to produce aqueous humor by the biphasic mechanism of intracellular ice crystal formation and ischemic necrosis (13). Initially, freezing of extracellular fluid concentrates the remaining solutes, which leads to cellular dehydration and is the probable mechanism of cell death associated with a slow freeze. When the rate of cooling is rapid, intracellular ice crystals develop. Although these crystals are not always lethal to the cell, a slow thaw leads to the formation of larger crystals, which are highly destructive to the cell by an uncertain mechanism. Maximum cell death is achieved with a rapid freeze and a slow thaw. A second and later mechanism of cryoinduced cell death is a superimposed hemorrhagic infarction, which results from obliteration of the microcirculation within the frozen tissue. Ischemic necrosis is the histologic hallmark of cryoinjured tissue.

Animal studies have revealed significant differences between the temperature of the cryoprobe and the temperature within the treated tissues (14,15). In living eyes, a temperature of 60°C to 80°C over the sclerolimbal area was shown to produce a temperature of approximately 10° C at the tips of the ciliary processes after a lag of 20 to 30 seconds (15). The latter temperature is near the minimum thermogradient at which cryoinjury normally occurs (15). Ciliary body blood flow in rabbits is reduced 50% to 60% when treated with 80° C cryoapplications for 60 seconds (16). Histologic studies of eyes treated with cyclocryotherapy show destruction of vascular, stromal, and epithelial elements of the ciliary processes with replacement by fibrous tissue (4,15,17,18). Ciliary epithelium has been observed to regenerate in monkeys, but not in human eyes (18).

In addition to lowering the IOP, cyclocryotherapy may provide relief of pain by the destruction of corneal nerves. Wallerian degeneration of corneal nerve fibers was observed in rabbits following cyclocryotherapy, although regeneration began within 9 to 16 days (19).

EARLY CYCLODESTRUCTIVE PROCEDURES

PENETRATING CYCLODIATHERMY

Weve (1) introduced the concept of cyclodestructive surgery in 1933, using nonpenetrating diathermy to produce selective destruction of ciliary processes. Vogt (2,3) modified the technique by using a diathermy probe, which penetrated the sclera, and this became the standard cyclodestructive procedure. The technique involved penetration of the sclera 2.5 to 5 mm from the corneolimbal junction with a 1.0- to 1.5-mm electrode and the application of a diathermy current of 40 to 45 mA for 10 to 20 seconds (3). This could be done with or without preparation of a conjunctival flap. One or two rows of diathermy lesions were generally placed several millimeters apart for approximately 180 degrees. The mechanism of permanent IOP reduction was probably cell death within the ciliary body (4). In addition, it may be that the more posteriorly placed lesions created a draining fistula in the region of the pars plana.

Early reports of experience with cyclodiathermy were encouraging (5,6). However, subsequent study revealed a low success rate and a significant incidence of hypotony. In a review of 100 cases, 5% had lasting, useful reduction in IOP, whereas about the same number developed phthisis (7). Results undoubtedly vary with the technique, and experience with a newer one-pole diathermy unit was said to be encouraging (8).

 

β-Irradiation Therapy

In 1948, Haik and co-workers (9) reported the experimental application of radium over the ciliary body in rabbit eyes and in one clinical case. Although this was shown to produce a reduction in the vascular supply of the ciliary body, it also caused damage to the lens, and the technique was never adopted for clinical use.

Cycloelectrolysis

Berens and co-workers (10) in 1949 described a technique that employed the use of low-frequency galvanic current to create a chemical reaction within the ciliary body. This led to the formation of sodium hydroxide, which is caustic to the tissue of the ciliary body. Although this was shown in rabbit studies to produce destruction of ciliary processes (11), the procedure did not seem to have significant advantages over penetrating cyclodiathermy and never achieved widespread clinical popularity.

CYCLOCRYOTHERAPY

The use of a freezing source as the cyclodestructive element was suggested by Bietti (12) in 1950. Cyclocryotherapy was generally thought to be somewhat more predictable and less destructive than penetrating cyclodiathermy and gradually replaced the latter technique as the most commonly used cyclodestructive operation. It is still used by many surgeons, especially when laser technology is not available.

OVERVIEW OF CYCLODESTRUCTIVE PROCEDURES

Cyclodestructive operations differ according to (a) the destructive energy source and (b) the route by which the energy reaches the ciliary processes. In the 1930s and 1940s, several energy sources were evaluated, including diathermy, β-irradiation, and electrolysis, although only cyclodiathermy achieved clinical acceptance. Cryotherapy was introduced in the 1950s and became the most commonly used cyclodestructive procedure. However, subsequent experience with laser cyclophotocoagulation showed clear advantages over other techniques, and it has become the preferred cyclodestructive operation. Other cyclodestructive techniques include therapeutic ultrasound and microwave cyclodestruction. Each of these energy sources may be delivered by the transscleral route, in which the destructive element passes through conjunctiva, sclera, and ciliary muscle before reaching the ciliary processes. Transscleral cyclodestructive operations have the advantages of being nonincisional and relatively quick and easy. However, significant disadvantages include the inability to visualize the processes being treated and damage to adjacent tissue, leading to unpredictable results and frequent complications. With the advent of laser energy as the cyclodestructive element, alternative delivery routes are possible, including transpupillary and intraocular.

Cyclodestructive Surgery

All of the operations discussed in the preceding chapters lower the intraocular pressure (IOP) by improving the rate of aqueous outflow. This is clearly preferred from a physiologic standpoint, in that the aqueous humor can continue to be produced in an unaltered state and fulfill its various functions, including nourishment of intraocular tissues. An alternative approach to reducing intraocular pressure, however, is to reduce the rate of aqueous production by partially eliminating the function of the ciliary processes. These techniques are rarely the first operation of choice, because the results are hard to predict and the complication rate is high due to damage to adjacent ocular structures and the influence of a pronounced inflammatory response. However, the cyclodestructive procedures constitute a valuable adjunct in our surgical armamentarium for cases in which other operations have repeatedly failed or when the surgeon wishes to avoid incisional surgery, such as in eyes with poor visual potential or with a high risk of intraocular complications with standard outflow procedures.

Glaucoma and heavy computer use

Possible association between heavy computer users and glaucomatous visual field abnormalities: a cross sectional study in Japanese workers

Source: Journal of Epidemiology and Community Health 2004;58:1021-1027
� 2004 BMJ Publishing Group Ltd
Masayuki Tatemichi1, Tadashi Nakano2, Katsutoshi Tanaka3, Takeshi Hayashi4, Takeshi Nawa4, Toshiaki Miyamoto5, Hisanori Hiro6 and Minoru Sugita1

1 Department of Environmental and Occupational Health, Toho University School of Medicine, Japan
2 Department of Ophthalmology, Jikei University School of Medicine, Japan
3 Department of Occupational Mental Health, Kitasato University Graduate School of Medical Sciences, Japan
4 Hitachi Health Centre, Japan
5 Adecco Health Support Centre, Kimitsu Works, Japan
6 Koukankai, Tsurumi Centre, Japan

Correspondence to:
Dr M Tatemichi
Department of Environmental and Occupational Health, Toho University School of Medicine, 5-21-16 Omori-nishi, Otaku, Tokyo 143-8540, Japan; tatemich@med.toho-u.ac.jp

Study objective: To study the association between computer use and visual field abnormalities (VFA) and to assess whether heavy computer users have an increased risk of glaucoma.

Design: Cross sectional multicentre study.

Subjects and observation procedures: A total of 10,202 randomly selected Japanese workers (mean (SD) age 43.2 (9.8) years) were screened for VFA using the frequency doubling technology perimetry (FDT-VFA), in addition to undergoing a general medical check up, and then ophthalmologically examined. Information about their computer use and refractive errors was obtained from a questionnaire and interview, respectively.

Main results: As a result of FDT test, 522 and 8602 subjects were positive and negative for FDT-VFA, respectively. A significant (p = 0.004) interaction was found between computer use and refractive errors regarding the risk of FDT-VFA. In stratified analysis, heavy computer users with refractive errors showed a significant positive association with FDT-VFA (odds ratio (OR) = 1.74, 95% confidence interval (CI) 1.28 to 2.37), while those without refractive errors did not. Comparison of 165 subjects with an ophthalmological diagnosis of glaucoma and 2918 controls showed that the OR for glaucoma of heavy computer users with refractive errors was 1.82 (95% CI 1.06 to 3.12). Of 165 subjects with glaucoma, 141 had refractive errors, especially myopia (96.4%, 136 of 141).

Conclusions: Although there are limitations to this study, such as its cross sectional design, heavy computer users with refractive errors seem to have an increased risk of FDT-VFA. Glaucoma might be involved in an underlying disease and myopia in a risk factor for FDT-VFA.

Abbreviations: VFA, visual field abnormality; FDT, frequency doubling technology; IT, information technology; BMI, body mass index; VDT, visual display terminal; OAG, open angle glaucoma; SAP, standard automated perimetry

Source:http://jech.bmj.com/cgi/content/abstract/58/12/1021

Examining the patient at risk from primary open angle glaucoma

Guideline
18.01 When examining a patient who falls within the at-risk groups for primary open-angle glaucoma, the optometrist has a duty to carry out the appropriate tests necessary to determine the likelihood of the condition being present.


Advice


18.02 Glaucoma can be difficult to detect in the early stages and practitioners are reminded that they should keep up to date with current thinking surrounding the pathophysiology, clinical signs and diagnostic techniques in order that they may offer patients the appropriate examinations to detect glaucoma.
18.03 It is for the practitioner to satisfy him/herself that procedures are included or excluded according to the patient’s clinical need but in addition to the guideline on the eye examination, good practice for these patients should normally include:

• (a) Assessment of the optic nerve head.
• (b) Tonometry. Where pressures are high or borderline, arrangements should be made for the test to be repeated, noting the time of day of each test;

the examination may also include:

• (c) Central visual field assessment using perimetry with threshold control. Where necessary practitioners should consider repeating visual fields assessment to obtain a meaningful result.

18.04 Non-contact applanation tonometry is acceptable for screening but good practice would suggest that equivocal results be followed up with contact applanation tonometry.
18.05 If a patient, having been given the reason for tonometry, refuses consent to the procedure, the optometrist should record this in the patient record, together with the patient’s reason for refusing the procedure. The optometrist should use his/her professional judgement to decide how best to manage the patient.
18.06 The majority of patients who can be considered to be at risk of primary open angle glaucoma will be identifiable in the course of the initial overall eye examination. They are principally patients with: high IOP, optic disc features suggestive of glaucoma, evidence of high myopia, or symptoms of loss of peripheral vision. In addition, patients with a family history of glaucoma in first degree relatives, or in certain ethnic groups (e.g. African-Caribbean people) can always be considered as being at more than average glaucoma risk, even in the absence of the above. Research has shown that patients age 40 and over are at greater risk of glaucoma. There is an increasing risk with every decade of life thereafter.
18.07 The signs of asymptomatic primary angle closure glaucoma are almost identical to those of primary open angle glaucoma with the sole exception being an anterior chamber angle capable of closure. Assessment of the anterior eye and angle (e.g. by slit lamp van Herick technique) is advisable for all patients suspected of having glaucoma. Optometrists should be aware that the prevalence of angle closure glaucoma is greater than that of open angle glaucoma in people of South or East Asian descent.

Co-managed care
18.08 The above advice applies to routine practice. Where co-managed care schemes are in operation, specific locally agreed protocols are likely to be operated which should take precedence.

Information
18.09 Assessment of the optic nerve head would include assessing the size of the disc, cup/disc ratio, presence of any asymmetry between the two eyes, colour and width of the neuro-retinal rims especially superiorly and inferiorly, and unusual features such as notching, disc haemorrhage etc. Cup/disc ratios can be assessed according to grading scales.

18.10 Practitioners are reminded that around 40% of patients with glaucoma have IOP below 21mmHg 1, and so just because patients have an IOP that would be considered within the ‘normal’ range does not mean that they do not have glaucoma. It is also important to note that some patients have pressures above 21mmHg and do not have glaucoma. These patients are nevertheless at greater risk of developing glaucoma and should be monitored as such.

18.11 Central visual field assessment may provide useful diagnostic information and may compliment the examination of the optic nerve head. This may prove particularly important in the diagnosis of ‘normal pressure glaucoma’. Whilst visual field examination may sometimes produce anomalous results in the absence of pathology, the usefulness of baseline measures and ongoing comparisons should not be underestimated.

18.12 Practitioners should be aware of the possibility that patients may present with other forms of glaucoma e.g. acute or sub-acute narrow angle glaucoma or secondary glaucoma due perhaps to pseudoexfoliation syndrome or pigment dispersion syndrome.

Overview on canaloplasty for primary open-angle glaucoma

Canaloplasty is a non-penetrating surgical technique for glaucoma which aims to restore the natural drainage of fluid from the eye.

Canaloplasty may be performed under local or general anaesthetic. A superficial hinged flap of sclera is made and a deeper flap excised, exposing Schlemm’s canal. A microcatheter with an illuminated tip is introduced into the canal and advanced around its entire circumference. As the catheter tip advances, viscoelastic fluid is injected into the canal to dilate it. After catheterisation of the entire canal length is complete, a suture is tied to the tip of the microcatheter, which is withdrawn, pulling the suture into the canal. The
suture is cut from the microcatheter and tied in a loop encircling the inner wall of the canal. The suture is tightened, so distending the trabecular meshwork with the aim of widening the canal.

The superficial flap is sutured. A special ultrasound imaging system is used to help identify the canal and to visualise the instruments in the canal before, during and after the surgery.

Efficacy

In a case series of 94 patients, successful circumferential catheterisation of Schlemm’s canal was achieved in 88% (83/94) of patients, and a suture was successfully placed in the canal in 79% (74/94) of patients. Mean intraocular
pressure was reduced from 24.7 mmHg at baseline to 15.3 mmHg at 12-month follow-up (p < 0.05). (The normal upper limit for intraocular pressure is 21 mmHg.) The mean number of drugs to lower the intraocular pressure was reduced from 1.9 at baseline to 0.6 at 12-month follow-up.

Furthermore, 88% (50/57) and 96% (46/48) of patients with successful suture placement had intraocular pressures of 21 mmHg or lower after 3 months and 6 months, respectively (with or without drugs to lower intraocular pressure).Four patients had poor intraocular pressure control after canaloplasty and required subsequent trabeculectomy.


The Specialist Advisers considered key efficacy outcomes to include control of intraocular pressure, preservation of the visual field and ocular comfort.


Safety
The case series of 94 patients reported ocular-related complications including hyphema (the presence of blood in the anterior chamber) (3%), elevated intraocular pressure (3%), detachment of Descemet’s membrane (1%), hypotony (abnormally low intraocular pressure) (1%), choroidal effusion (1%) and exposed closure suture (1%) (absolute figures not reported).

In the same case series, the loss of two or more lines of best corrected visual acuity was reported in 25% (18/71) of patients at 1-month follow-up, 7% (5/68) of patients at 3-month follow-up and 9% (4/47) of patients at 12-month follow-up. The authors noted that the decline in visual acuity in these patients was related to disease processes not associated with the canaloplasty procedure.

The Specialist Advisers considered theoretical adverse events to include anterior chamber perforation, tearing of Descemet’s membrane resulting in corneal opacification or retinal damage, intraocular inflammation caused by the suture, cataract formation, sustained increases in intraocular pressure, hypotony, and bleb formation or suture exposure with endophthalmitis.

Common Eye Problems：Beware macular degeneration and cataracts.

Nancy Shute
Premium Health News Service


Few 40-year-olds' to-do lists include "Be proactive about not going blind," so you might have to play catch-up. Age 40 really is the time to start protecting your eyes against serious diseases such as glaucoma and macular degeneration, neither of which has symptoms in the early stages. (That's in contrast to the loss of close-focus vision that forces 45-year-olds into bifocals but doesn't threaten blindness.) "Patients may go to the drugstore and get these over-the-counter reading glasses and think, 'Hey, I've fixed my eyes,' " says Andrew Iwach, an ophthalmologist who is executive director of the Glaucoma Center of San Francisco. "Yet they may be unaware that they can be silently losing vision."

The best defense: a comprehensive eye exam that screens for glaucoma, macular degeneration, diabetic retinopathy, and cataracts. (And no, passing your driver's license retest doesn't count.)

Cataracts are the most common age-related eye disease, with more than 17 percent of Americans age 40 and over affected. The main cause, aside from plain old aging, is exposure to ultraviolet B radiation in sunlight. Wearing sunglasses and brimmed hats while outside can reduce exposure and delay the need for surgery to remove a clouded lens. The good news is that cataract surgery has been refined so that the supersmall incisions are self-sealing; new artificial lenses can be folded or rolled and slipped into place.

Glaucoma and macular degeneration are more insidious conditions; by the time you know you're a victim, vision has often been lost forever. In glaucoma, the optic nerve becomes damaged, and vision loss usually starts at the side. Most people with glaucoma have increased pressure inside the eyeball, and although it's unclear how that pressure affects the optic nerve, medications that lower the pressure are effective at slowing damage.

With age-related macular degeneration, the macula, a spot in the center of the retina that provides clear central vision, is damaged by abnormal blood vessel growth or slow loss of light-sensitive cells. High doses of supplements, including vitamins C and E and beta carotene and the mineral zinc, have been found to slow the progression of AMD in several trials. But because some studies have linked high doses of beta carotene and vitamin E to cardiovascular risks, ophthalmologists advise against taking supplements as a preventive measure unless they're doctor-prescribed. It's impossible to get that quantity of antioxidants and zinc in food alone, but some studies have found that people who eat a lot of dark-green leafy vegetables have a lower risk of AMD. Smoking increases the risk of macular degeneration, so there's one more reason to quit.

People with diabetes have added reason to worry: Diabetic retinopathy affects some 40 percent of people with the disease, with 8 percent of all diabetics facing significant vision loss. Keeping your blood sugar levels under control reduces the risk of harm.

source: http://www.baltimoresun.com/health/seniors/sns-health-eye-problems,0,2573617.story

Xibrom(™) (bromfenac ophthalmic solution)

Xibrom(™) (bromfenac ophthalmic solution)

Xibrom is a topical non-steroidal anti-inflammatory compound for the treatment of ocular inflammation and pain following cataract surgery. Xibrom, under a different trade name but identical formulation, was launched in Japan in 2000 by Senju Pharmaceuticals Co. Ltd. ISTA acquired U.S. marketing rights for Xibrom in 2002 and launched the product in the U.S. in 2005. According to IMS data, Xibrom is the 2009 dollar market share leader in the U.S. ophthalmic nonsteroidal anti-inflammatory market, with net sales of $33.8 million for the six-month period ended June 30, 2009.

Xibrom currently is labeled as an eye drop used twice-daily beginning 24 hours after cataract surgery. Xibrom has not been approved by the FDA as a once-daily treatment. ISTA's sNDA filing will request the Agency to approve a change to the drug's label to reflect Xibrom's efficacy as a once-daily treatment in this patient population.

ISTA Pharmaceuticals, Inc. (Nasdaq: ISTA), today announced positive preliminary Phase 3 results from the Company's Xibrom(™) (bromfenac ophthalmic solution) 0.09% QD (once-daily) confirmatory clinical study. Xibrom 0.09% QD achieved statistical significance in the study's primary endpoint, the absence of ocular inflammation 15 days following cataract surgery, and the secondary efficacy endpoint, the elimination of ocular pain one day post surgery. During the study, no serious ocular or systemic adverse events occurred, and the safety profile is consistent with ISTA's currently marketed Xibrom twice-daily formulation.

Canaloplasty :A new minimally invasive surgery for glaucoma

Glaucoma is the leading cause of blindness in the United States, according to the National Institutes of Health. An estimated 4 million Americans are affected by glaucoma. Glaucoma screenings are suggested for anyone over 40, every two to four years. A routine exam can help identify risk for glaucoma and early signs of the disease.  Risk factors for glaucoma include: a family history of the disease, African Americans or Hispanic ancestry, diabetes, certain rare eye diseases and having had an eye injury or having used any corticosteroid preparation for a prolonged period.

Glaucoma is often treated with eye drops that reduce the production of fluid in the eye, or help it drain more quickly. However, when the medicines don't work -- or when patients can't remember to take them once or more daily -- surgery is an option. The traditional surgery is trabeculectomy, in which a portion of the trabecular meshwork is removed, helping to reduce the bottleneck causing elevated eye pressure. Trabeculectomy is considered the gold standard for effectiveness, but can cause infection or other complications serious enough to result in blindness.


Canaloplasty is one of the newest alternatives and involves forcing open a drainage canal, similar to what cardiologists do to unblock clogged arteries. The procedure is sometimes called "angioplasty for the eye." In canaloplasty, an incision is made in the eye and a thin catheter is inserted into Schlemm's Canal, a tube in the trabecular meshwork. Instead of a balloon, a thick clear gel is injected to open the canal. In addition, a suture, or surgical tie, is placed inside the canal and pulled tight to stretch open the trabecular meshwork, says Richard Lewis, a Sacramento, Calif., eye surgeon who serves as a consultant to iScience Interventional Corp., a Menlo Park. Calif., company that sells the catheter.

The procedure takes about a half hour and can be done under local anesthetic, typically in a hospital or outpatient surgery center with a sedative. The cost -- typically $2,500 to $3,500 -- is covered by many insurers, while others decline payment because they say there isn't yet enough evidence for the procedure's effectiveness. Serious complications are rare, but can include swelling, overly low eye pressure and blood in the eye.

Surgeons agree that canaloplasty is a safer option than the traditional surgery, but some urge caution."The results that they've published thus far show great promise," says Douglas Rhee, a glaucoma specialist at the Massachusetts Eye & Ear Infirmary in Boston. "Additional studies need to be done," he adds, including trials that compare it directly to other procedures such as trabeculectomy.

Arthur Sit, assistant professor of ophthalmology at the Mayo Clinic in Rochester, Minn. is concerned that scar tissue left from canaloplasty could make a subsequent trabeculectomy less effective. Dr. Sit prefers trabectome, which he says involves a smaller incision that is less likely to impact later surgeries.

Trabectome :A New Glaucoma Treatment

Glaucoma is a disease that causes irreversible damage to the optic nerve from increasing pressure within the eye. This occurs because the eye produces a clear fluid that does not drain adequately and raises the eye pressure. The first sign of glaucoma is a loss of peripheral vision that is usually not noticed by the patient until it affects the central vision.  Vision loss to glaucoma can't be restored so treatment aims to reduce eye pressure to prevent further damage.

Traditionally, ophthalmologists first prescribe eye drops to reduce the eye pressure in glaucoma patients and if that doesn't work, they can perform a laser procedure called a trabeculoplasty to the existing internal drainage canal. If eye drops or the laser procedure are not effective in controlling pressure, the patient may need an operation called trabeculectomy.  This involves creating a small hole in the sclera (white of an eye) and removes a small area of trabecular meshwork (tissue that is diseased in glaucoma leading to eye pressure build up).  Another operation is to place a silicone tube in an eye to drain fluid.  Both these operations have long recovery periods and are associated with multiple complications.


Now a new treatment option are available at the University of Kentucky, the only medical facility in the state to offer the procedure. Performed with a device called a Trabectome, the minimally invasive procedure takes about 30 minutes and is designed to decrease pressure within the eye and stabilize vision.


The Trabectome tool is introduced in the eye through a tiny 1.5 millimeter incision at the edge of the cornea. A small strip of trabecular meshwork is then ablated and removed.  This gently unblocks the eye and lowers the pressure.  The procedure requires very little sedation and patients generally recover within a week.

The benefits of Trabectome over the traditional glaucoma surgery include:

    * Low complication rate
    * Rapid recovery
    * Simpler than traditional surgeries
    * Easily combined with cataract surgery

Trabectome is simpler and safer than traditional glaucoma surgeries and provides excellent eye pressure reduction,but not all patients with glaucoma are suitable for Trabectome surgery.  For more information about Trabectome or other ophthalmologic procedures, or to schedule an appointment, call (859) 323-5867.

Glaucoma and glucosamine

Glucosamine is very interesting because, theoretically, it could worsen the glaucoma because it is found in high concentration in the eye drain in abnormal eyes with glaucoma. Yet, it might lower eye pressure for reasons that are not well known. No good proof, just yet! Remember, correlation does not mean one thing causes another, only that the two are linked somehow. Check out the research on circumen, from the tumeric root, and glaucoma. That product does show potential.

but the problem suggested with glucosamine is not glucosamine but chondroitin found in glaucomanous eyes in excess. These are related sustances but are utilized differently. Glucosamine does not mean you are loading up on chondroitin. The chondroitin molecules is split up and re-organized in the bloodstream. Glucosamine does not have this mode of action. So, glucosamine could be a positive glaucoma treatment, chondroitin maybe not.

Glaucoma screening and Medicare coverage

Glaucoma represents a family of diseases commonly associated with optic nerve damage and visual field changes (a narrowing of the eyes’ usual scope of vision). It is the second leading cause of irreversible blindness in the United States.1 Of the various forms of glaucoma (such as congenital, angle-closure, and secondary), open-angle glaucoma is the most common

Over 2.2 million Americans age 40 and over have open-angle glaucoma. Often progressing silently, it is estimated that up to one-half of Americans with glaucoma may not know they have the disease.

Glaucoma occurs when increased fluid pressure in the eye presses against the optic nerve, causing damage. The damage to optic nerve fibers can cause blind spots to develop. These blind spots usually go undetected until the optic nerve is significantly damaged. If the entire optic nerve is destroyed, blindness results.4 Since glaucoma progresses with little or no warning signs or symptoms, and vision loss from glaucoma is irreversible, it is very important that people at high risk for the disease receive an annual screening. Studies have shown that the early detection and treatment of glaucoma, before it causes major vision loss, is the best way to control the disease.

The glaucoma screening covered by Medicare includes:
• A dilated eye examination with an intraocular
pressure (IOP) measurement
AND
• A direct ophthalmoscopy examination or a slitlamp
biomicroscopic examination


Increased IOP is common with glaucoma. In the past, it was thought that an increased IOP measurement indicated glaucoma; however, an IOP measurement using non-contact tonometry (more commonly known as the “air puff test”) alone was commonly used to diagnose glaucoma. Health care professionals now know that glaucoma can be present with or without increased IOP, which makes the examination of the eye and optic nerve (along with the IOP measurement) a critical part of the glaucoma screening.

Risk Factors

Anyone can develop glaucoma. Some risk factors that may increase an individual’s chances of developing glaucoma include age, race, family history, and medical history. Medicare provides coverage of an annual glaucoma screening for beneficiaries in at least one of the following high risk groups:

• Individuals with diabetes mellitus
• Individuals with a family history of glaucoma
• African-Americans age 50 and over
• Hispanic-Americans age 65 and over

Because of the prevalence of glaucoma found in these groups, it is of special importance for these individuals to receive regular glaucoma screenings. According to the National Eye Institute (NEI), African-Americans between the ages of 45 – 64 are 15 times more likely to go blind from glaucoma than Caucasians from the same age group5 and the incidence of glaucoma increases with age. Adults with diabetes are nearly twice as likely to develop glaucoma as other adults, and the longer a person has had diabetes, the more likely he or she is to develop glaucoma.

Coverage information

Medicare coverage of glaucoma screening was implemented with the Benefits Improvement and Protection Act of 2000 (BIPA). This coverage took effect on January 1, 2002. Medicare provides coverage for an annual glaucoma screening (i.e., at least 11 months have passed following the month in which the last Medicare-covered glaucoma screening examination was performed) for eligible beneficiaries in at least one of the high risk groups .

Coverage of an annual glaucoma screening is provided as a Medicare Part B benefit. The coinsurance or copayment applies after the yearly Medicare Part B deductible has been met. Medicare will pay for glaucoma screening examinations when they are furnished by or performed under the direct supervision in the office setting of an optometrist or ophthalmologist, legally authorized to perform the services under State law. NOTE: Medicare does not provide coverage for routine eye refractions.

Documentation

Medical record documentation must support that the beneficiary is a member of one of the high risk groups previously discussed. The documentation must also support that the appropriate screening (i.e., either a dilated eye examination with IOP measurement and a direct ophthalmoscopic examination OR a slit-lamp biomicroscopic examination) was performed.

OVERVIEW OF CYCLODESTRUCTIVE PROCEDURES

Cyclodestructive operations differ according to (a) the destructive energy source and (b) the route by which the energy reaches the ciliary processes. In the 1930s and 1940s, several energy sources were evaluated, including diathermy, β-irradiation, and electrolysis, although only cyclodiathermy achieved clinical acceptance. Cryotherapy was introduced in the 1950s and became the most commonly used cyclodestructive procedure. However, subsequent experience with laser cyclophotocoagulation showed clear advantages over other techniques, and it has become the preferred cyclodestructive operation. Other cyclodestructive techniques include therapeutic ultrasound and microwave cyclodestruction. Each of these energy sources may be delivered by the transscleral route, in which the destructive element passes through conjunctiva, sclera, and ciliary muscle before reaching the ciliary processes. Transscleral cyclodestructive operations have the advantages of being nonincisional and relatively quick and easy. However, significant disadvantages include the inability to visualize the processes being treated and damage to adjacent tissue, leading to unpredictable results and frequent complications. With the advent of laser energy as the cyclodestructive element, alternative delivery routes are possible, including transpupillary and intraocular.

Cyclodestructive Surgery

All of the operations discussed in the preceding chapters lower the intraocular pressure (IOP) by improving the rate of aqueous outflow. This is clearly preferred from a physiologic standpoint, in that the aqueous humor can continue to be produced in an unaltered state and fulfill its various functions, including nourishment of intraocular tissues. 

An alternative approach to reducing intraocular pressure, however, is to reduce the rate of aqueous production by partially eliminating the function of the ciliary processes. These techniques are rarely the first operation of choice, because the results are hard to predict and the complication rate is high due to damage to adjacent ocular structures and the influence of a pronounced inflammatory response. However, the cyclodestructive procedures constitute a valuable adjunct in our surgical armamentarium for cases in which other operations have repeatedly failed or when the surgeon wishes to avoid incisional surgery, such as in eyes with poor visual potential or with a high risk of intraocular complications with standard outflow procedures.

a combined glaucoma and cataract operation may be the procedure of choice

In an eye with a cataract, for which extraction is believed to be indicated, and coexisting glaucoma, the surgical approach is based primarily on the status of the glaucoma. In some cases, cataract extraction alone may be sufficient, whereas other eyes may require filtering surgery alone with cataract surgery at a later date. In other patients, a combined glaucoma and cataract operation may be the procedure of choice. The preferred technique for the glaucoma portion of a combined procedure is usually some form of guarded filtering surgery, and the combination of phacoemulsification with a guarded filtering procedure, possibly in conjunction with antimetabolite therapy, appears to have improved the long-term success rate of the combined procedure.

REFERENCES

1. Abbasoglu OE, Hosal B, Tekeli O, et al. Risk factors for vitreous loss in cataract surgery. Eur J Ophthalmol 2000; 10: 227.

2. Chiselita D, Vancea PP. [The effect of the pseudoexfoliative syndrome on the evolution and treatment of pseudoexfoliative glaucoma and senile cataract.] Oftalmologia 1996; 40:249.

3. Fine IH, Hoffman RS. Phacoemulsification in the presence of pseudoexfoliation: challenges and options. J Cataract Refract Surg 1997;23:160.

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Some Combined Techniques as Cataract and Glaucoma Surgery

Techniques have been described in which a trabeculotomy is performed through a radial incision at 12 o'clock adjacent to a partial-thickness corneoscleral incision before extending the incision full-thickness for the cataract surgery (28,144,145). Phacoemulsification has also been combined with holmium laser sclerostomy, using either an ab externo (146) or ab interno (147) approach, with the latter providing more IOP reduction (148). Combining phacoemulsification with endoscopic laser to perform either goniopuncture (149) or cyclophotocoagulation (150,151) through a cataract incision has also been proposed as an alternative to combined cataract and trabeculectomy surgery. Deep sclerectomy (152,153) and viscocanalostomy (154,155) combined with phacoemulsification have both been reported to achieve IOP reduction and visual acuity similar to phacoemulsification combined with trabeculectomy, but with fewer complications. A technique of combining trabecular aspiration with phacoemulsification was proposed as an alternative to combination of trabeculectomy and phacoemulsification in pseudoexfoliative glaucoma, but it did not appear to provide sufficient postoperative IOP lowering (156).

Cataract surgery has also been combined with implantation of an Ahmed (157) or Baerveldt (158) drainage implant, and is reported to be an effective method of improved IOP control in certain cases in which combined trabeculectomy has failed or has a high risk of failure, for example, when previous surgery has produced significant conjunctival scarring, or in patients with secondary glaucoma. However, complications, such as aqueous misdirection (158), corneal edema (158), choroidal effusion (158), and capsular bag distention (159), have been reported.

Adjunctive Use of Antimetabolites

Another factor that may be associated with the improved long-term IOP control with combined procedures is the adjunctive use of antimetabolites to minimize excessive fibrosis. The first of these to be evaluated was 5-fluorouracil (5-FU), which is typically administered as several postoperative subconjunctival injections. Although preliminary experience with combined ECCE and trabeculectomy suggested some benefit (130), subsequent studies showed no significant difference with or without adjunctive 5-FU (131,132). Result of studies with combined phacoemulsification and trabeculectomy have shown little (133,134) or no (135) benefit to 5-FU.

Figure 44.2. Slit-lamp view of eye with functioning glaucoma-filtering bleb in which extracapsular cataract extraction and posterior chamber lens implantation were performed through a clear corneal incision to preserve the preexisting bleb. (From Ritch R, Shields MB, Krupin T, eds. The glaucomas, 2nd ed. St. Louis: CV Mosby, 1996:1751, with permission.)

Figure 44.3. Intraoperative view during guarded sclerectomy and phacoemulsification showing excision of fistula from posterior lip of scleral tunnel incision.

 

When intraoperative mitomycin-C (MMC) was used in conjunction with combined cataract extraction and trabeculectomy, earlier studies did not demonstrate significant benefits of using MMC (136,137), although IOP was well controlled at 6 to 12 months postoperatively (138,139). More recently, several randomized studies have found greater IOP control with the use of MMC in combined glaucoma and cataract surgery (140,141,142,143).

Guarded Fistula and Cataract Extraction

The protective scleral flap over a limbal fistula, which reduces the chances of an early postoperative flat anterior chamber, makes the guarded filtering operation particularly desirable for combined procedures. Several techniques were described for combining a trabeculectomy with intracapsular cataract surgery during the 1970s (103,104,105), but it was not until the popularity of extracapsular cataract extraction and PC IOL implantation (the “triple procedure”) in the 1980s (106,107,108,109) and phacoemulsification in the 1990s, that combined trabeculectomy and cataract extraction began to provide reasonably consistent long-term glaucoma control.
Phacoemulsification has become the preferred cataract technique for combined procedures during the 1990s and appears to be associated with further improvement in the long-term success rates. The procedure can be combined with a trabeculectomy by utilizing the fistula for the cataract incision (110). The incision may be 6 mm to insert a rigid IOL, or less than 3 mm for a foldable lens. The latter has been shown to have a significantly lower incidence of postoperative complications and better visual acuity in the early postoperative period (111). After creating a superior scleral tunnel and converting the tunnel to a scleral flap, a limbal fistula is created under it (single-site technique). If a scleral tunnel incision is used, the fistula can be excised from the posterior lip of the incision, leaving the anterior lip of the tunnel to cover the fistula (112) (Fig. 44.3).
One of the commonly used techniques is to perform a phacoemulsification through a separate temporal corneal incision as a first step, followed by a trabeculectomy at the superior limbus (two-site technique) (101,113,114). Prospective studies, comparing single-site versus two-site approaches, have shown that patients in the two-site group had 1 to 2 mm Hg more IOP reduction and required less postoperative medications (115,116,117), although the differences were not statistically significant.
An alternative approach with ECCE involves preparation of the partial-thickness scleral flap and limbal fistula in the usual manner, followed by extension of the corneoscleral incision from either side of the fistula. After a standard ECCE and implantation of the PC IOL, both scleral flap and corneoscleral or corneal incision are closed with multiple sutures. The conjunctival flap is closed in the manner described for glaucoma filtering procedures (see Chapter 40). A limbal based versus fornix-based conjunctival flap was found to have no difference on the outcome of trabeculectomy combined with either ECCE (118,119) or phacoemulsification and PC IOL (120,121,122,123,124). The use of topical apraclonidine 1% before, immediately after, and 12 hours after surgery was shown to provide better IOP control after combined ECCE and trabeculectomy (125), although using apraclonidine 1% once after phacoemulsification has not demonstrated significant IOP reduction (126). Oral acetazolamide (127) and topical dorzolamide (128) have been shown to be more effective in controlling postoperative IOP elevation than apraclonidine.
Several studies have compared phacoemulsification to ECCE in combination with a guarded filtering procedure, with the general results that the former is associated with fewer complications, improved long-term IOP control, and a better visual outcome (52,112,129).