Wednesday, 23 August 2017

Risking their eye health

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NationHome > News > Nation
Sunday, 8 February 2015

Risking their eye health
BY HARIATI AZIZAN


Risky business: Contact lens sold by an unauthorised seller at one of the midnight bazaars around Kuala Lumpur.
PETALING JAYA: With Chinese New Year around the corner, savvy shoppers will look out for the best buys in the latest fashion essentials. But there is one item that may cost them more than they bargain for if purchased without care – cosmetic contact lenses.

Every month, at least one person in the country becomes blind from eye damage and infection caused by contact lens, says the Health Ministry’s Malaysian Optical Council (MOC).

“This is because many are buying contact lenses, especially cosmetic contact lenses, from uncertified sellers at pasar malam, uptown bazaars, beauty shops and even kiosks at the malls. These uncertified sellers cannot give them the right fitting and instructions on how to use their lenses.

“Contact lenses are not one-size-fits-all and not everyone can wear contact lenses. A poor fit or unsuitable type of lens can cause serious eye damage,” warned MOC secretary Nor Azizah Ismail. The correct and safe way is to go for an eye examination and get a prescription before buying any contact lenses. Under the Optical Act 1991, only optometrists and opticians certified by the MOC are licensed to prescribe and dispense contact lenses.

Cosmetic contact lenses, which include coloured lenses, novelty or special effect lenses and circle or “big eyes” lenses (also known as anime lenses), come both with prescription power to correct vision and without power (plano).

A check around town revealed that cosmetic contact lenses with prescription power are being sold at many night market stalls, beauty shops and mall kiosks.

Non-powered cosmetic contact lenses are not covered by the Optical Act 1991, but the Health Ministry is in the process of adding them under the Act, which will allow only certified optometrists and opticians to prescribe and dispense them.

Under the Optical Act, unlicensed contact lens vendors could be fined not less than RM1,000 for the first offence and RM2,000, as well as jail for six months for subsequent offences.

“Consumers who get an eye infection or go blind will have to live with the consequences for the rest of their lives.

“So, it is important they understand that cosmetic contact lenses, like contact lenses used to correct vision, can pose serious risks to eye health if they are not used properly.

“You should never wear any contact lenses without an eye examination and constant supervision by a certified eye care professional,” said Nor Azizah.

She said that stricter measures to regulate sale would be enforced with the gazetting of cosmetic contact lenses as a medical device under the Medical Devices Act 2012 (Act 737).

“When that is gazetted later this year, all cosmetic contact lenses will have to go through a process of standard assessment and registration before being sold in the Malaysian market.”

The Star
NationHome > News > Nation
Sunday, 8 February 2015
Bad hygiene habits the cause of eye infection

PETALING JAYA: Lack of awareness of the dangers and bad hygiene habits are the main reasons why contact lens users get eye infections, say experts.

“We hear all kinds of horror stories from patients, like cleaning their lenses with saliva, wearing lenses longer than they are supposed to and swapping lenses with friends to try a different colour or pattern,” said the Health Ministry’s Malaysian Optical Council (MOC) secretary Nor Azizah Ismail.

She said that in 2013, the number of patients seeking treatment for corneal ulcer and infections due to contact lens-related complication in government hospitals jumped to almost double the number in 2010.

Although most cases were mild, some were so bad that they needed eye transplant or caused blindness.

She said the worry was that the number of sufferers could be the tip of the iceberg, as the number of cases treated in the private sector was not known.

“I saw between 100 and 200 cases over the last few years, but I think there is a potential for an explosion of cases when you hear of some of the horrifying things users, especially the teens, say they are doing when wearing their contact lenses,” said Dr Michael Law, consultant ophthalmologist and eye surgeon at the International Specialist Eye Centre.

Hygiene is important because the most common contact lens, the soft contact lens, is made of a hydrogel material which is prone to collect dirt or protein deposits, making it an attractive home for bacteria and fungi.

“Acanthamoeba, a parasitic microbe, is in our water and can’t be killed by cholorine. If you leave your case wet with tap water, it can breed on your case or contact lens. When you put the lens on, the amoeba will find a new home in your eyes,” he said.

Though rare, acanthamoeba infection is an extremely painful, sight-threatening condition.

“Young people are the most at risk because they tend to be quite relaxed when it comes to hygiene standards in the use and care of contact lenses,” said Nor Azizah, noting that a majority of patients treated for lens wear complications were under the age of 30.

According to the industry, there were about 1.1 to 1.2 million contact lens users in Malaysia last year, but the hot trend of wearing cosmetic contact lenses that shows no sign of cooling off means the actual number could be growing.

Dr Kenneth Fong, an eye surgeon from the Eye Centre at Sunway Medical Centre, agreed that the number of those vulnerable to the risk could be higher.

“Many of the young patients I’ve seen say they are influenced by trends. If they see their friends doing it, they want to follow. But their budget may be smaller, so they focus on cheaper products from unreliable sources,” he said.

He advised them to get a proper eye check and prescription before buying contact lenses, especially those following the “big eyes” lens trend.

Such lenses, which cover the whites of the eye to make the irises appear bigger, can cause a serious infection if they are poorly fitted, he said.

“If your lenses are too tight, your eyes will not get enough oxygen. If they are too loose, they will fall off and your eyes might get scratched or cut in the process, opening you up to infection.”

The Star
NationHome > News > Nation
Sunday, 8 February 2015
Optometrists: Youngsters not seeing the dangers of cosmetic lenses

PETALING JAYA: “For sale: 90-day contact lenses, still new, used only once.”

It’s true what they say – these days, you can buy almost anything online. According to one anime enthusiast, Rosie, it is common for Cosplay fans here to put up their contact lenses for sale on social media after using them once.

“Our characters’ look includes the colour or shape of the eyes, so coloured contact lenses are an essential part of our costume kit.

“Many buy second-hand contact lens because it is cheaper when they want to change characters.

“There are even those who offer to exchange contact lenses with others online,” said the 20-something graphic artist.

Online sales of cosmetic contact lens is a growing trend among many young people, said the Association of Malaysian Optometrists (AMO).

“Search with keywords like ‘cheap contact lenses’ and you will find many individuals and online shops pushing the cosmetic products,” said AMO assistant honorary secretary Muhammad Syukri Mohamad Rafiuddin.

There are also many offers online for those interested in becoming cosmetic contact lens agents or stockists.

The explosion of online vendors, combined with the lack of knowledge about the dangers of improper use of contact lenses among the young, could have grim consequences, warned AMO president Murphy Chan.


Chan: ‘Sure, it is fashion but it is in contact with your cornea, and your cornea is unprotected tissue that can be damaged permanently.’
A study by the Hong Kong Polytechnic University in 2013 found that coloured contact lens samples purchased from the Internet failed safety and health tests, he said.

“The study found that the colour pigment on six out of 10 coloured lenses bought online came out easily when they were rubbed.

“And AMO believes the unauthorised contact lenses sold in Malaysia come from the same source,” Chan said.

Chan advised cosmetic lens users to buy from optometrists and opticians who were certified to dispense them.

“Look out for the Malaysian Optical Council’s pink and green certificate to ensure the quality and reliability of the contact lenses.”

He stressed the importance of going for an eye-check and getting a prescription before buying cosmetic contact lenses “even if you have a 20/20 vision”.

The Malaysian Optical Council secretary Nor Azizah Ismail said policing online sale of cosmetic contact lenses would be easier and stricter if they were gazetted as a medical device under the Medical Devices Act 2012 (Act 737).

“We will work with MCMC (Malaysian Communications and Multimedia Commission) and other enforcement authorities to monitor and regulate unauthorised cosmetic contact lenses and unlicensed vendors.”

After the gazette, Nor Azizah said, those who wanted to become manufacturers, distributors or importers of cosmetic contact lenses would need to be licensed by the Health Ministry.

“This also means that they need to be, or employ, qualified optometrists and opticians with the proper certification from MOC if they want to become stockists, agents or producers of cosmetic contact lenses.”

The Star
NationHome > News > Nation
Sunday, 8 February 2015
You only have one pair of eyes

BY HARIATI AZIZAN


Eyeful of trouble: Unauthorised cosmetic contact lenses are priced around RM15 at night markets. In beauty shops, they cost around RM25
IT is such a normal part of life that nobody blinks an eye when things do not feel right, until things go horribly wrong.

Since it was first invented in 1888 to correct vision, contact lenses have come such a long way that now even those with perfect vision are using them daily for cosmetic reasons.

The familiarity, however, has made many careless when it comes to safety and hygiene in the use and care for their contact lenses.

“There were patients who came in with chipped contact lenses. They said they continued wearing them because they didn’t feel any pain or had any problems with their vision. When we checked, we found that their eyes were already infected,” says the Health Ministry’s Malaysian Optical Council (MOC) secretary Nor Azizah Ismail, adding that many of those who come for treatment for contact lens complications are experienced users.

Combined with the number of young and new users who lack the right information on the dangers and awareness of the “Dos and Don’ts” of contact lens use and care, the risk of devastating eye infection is high in the country.

The most common infection related to contact lens use is keratitis, an infection of the cornea or the clear round part covering the eye’s iris and pupil.

Keratitis is caused by bacteria, fungus and microbes. In severe cases, it can cause corneal scarring that impairs vision, leading to a ­corneal transplant and blindness. But with proper handling, storage and cleaning of lenses, the risk of keratitis infection can be reduced.

Many bad habits, however, are already entrenched in users’ daily regime, laments Nor Azizah.

Tuesday, 22 August 2017

Myopia (Nearsightedness)

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By Gretchyn Bailey; reviewed by Gary Heiting, OD

Nearsightedness, or myopia, is the most common refractive error of the eye, and it has become more prevalent in recent years.

In fact, a recent study by the National Eye Institute (NEI) shows the prevalence of myopia grew from 25 percent of the U.S. population (ages 12 to 54) in 1971-1972 to a whopping 41.6 percent in 1999-2004.

Though the exact cause for this increase in nearsightedness among Americans is unknown, many eye doctors feel it has something to do with eye fatigue from computer use and other extended near vision tasks, coupled with a genetic predisposition for myopia.

Myopia Symptoms And Signs

If you are nearsighted, you typically will have difficulty reading road signs and seeing distant objects clearly, but will be able to see well for close-up tasks such as reading and computer use.

Other signs and symptoms of myopia include squinting, eye strain and headaches. Feeling fatigued when driving or playing sports also can be a symptom of uncorrected nearsightedness.

If you experience these signs or symptoms while wearing your glasses or contact lenses, schedule a comprehensive eye examination with your optometrist or ophthalmologist to see if you need a stronger prescription.

What Causes Myopia?

Myopia occurs when the eyeball is too long, relative to the focusing power of the cornea and lens of the eye. This causes light rays to focus at a point in front of the retina, rather than directly on its surface.

Nearsightedness also can be caused by the cornea and/or lens being too curved for the length of the eyeball. In some cases, myopia is due to a combination of these factors.

Myopia typically begins in childhood and you may have a higher risk if your parents are nearsighted. In most cases, nearsightedness stabilizes in early adulthood but sometimes it continues to progress with age.

Myopia Treatment

Nearsightedness can be corrected with glasses, contact lenses or refractive surgery. Depending on the degree of your myopia, you may need to wear your glasses or contact lenses all the time or only when you need very clear distance vision, like when driving, seeing a chalkboard or watching a movie.

Good choices for eyeglass lenses for nearsightedness include high-index lenses (for thinner, lighter glasses) and anti-reflective coating. Also, consider photochromic lenses to protect your eyes from UV and high-energy blue light and to reduce your need for a separate pair of prescription sunglasses outdoors.

If you're nearsighted, the first number ("sphere") on your eyeglasses prescription or contact lens prescription will be preceded by a minus sign (–). The higher the number, the more nearsighted you are.

Refractive surgery can reduce or even eliminate your need for glasses or contacts. The most common procedures are performed with an excimer laser.

In PRK the laser removes a layer of corneal tissue, which flattens the cornea and allows light rays to focus more accurately on the retina.

In LASIK — the most common refractive procedure — a thin flap is created on the surface of the cornea, a laser removes some corneal tissue, and then the flap is returned to its original position.
Then there's orthokeratology, a non-surgical procedure where you wear special rigid gas permeable (RGP or GP) contact lenses at night that reshape your cornea while you sleep. When you remove the lenses in the morning, your cornea temporarily retains the new shape, so you can see clearly during the day without glasses or contact lenses.

Orthokeratology and a related GP contact lens procedure called corneal refractive therapy (CRT) have been proven effective at temporarily correcting mild to moderate amounts of myopia. Both procedures are good alternatives to surgery for individuals who are too young for LASIK or are not good candidates for refractive surgery for other reasons.

Implantable lenses known as phakic IOLs are another surgical option for correcting nearsightedness, particularly for individuals with high amounts of myopia or thinner-than-normal corneas that could increase their risk of complications from LASIK or other laser vision correction procedures.

Phakic IOLs work like contact lenses, except they are surgically placed within the eye and typically are permanent, which means no maintenance is needed. Unlike IOLs used in cataract surgery, phakic IOLs do not replace the eye's natural lens, which is left intact.

Controlling Myopia

With more and more people getting nearsighted these days, there is a lot of interest in finding ways to control the progression of myopia in childhood.

A number of different techniques have been tried — including fitting children with bifocals, progressive lenses and gas permeable contact lenses — with mixed results.

Recently, researchers in New Zealand have reported encouraging outcomes from specially designed "dual focus" soft contact lenses for myopia control in nearsighted children. The experimental lenses have significantly less power in the periphery of the lens compared to the center, and it is thought that this "peripheral defocus" may reduce the tendency for greater lengthening of the eye that leads to progressive myopia.

In a study published in 2011, the researchers found that in 70 percent of nearsighted children (ages 11 to 14) who wore the experimental lenses in one eye and a standard soft contact lens in the other, myopia progression was reduced by 30 percent or more in the eye wearing the dual focus contact lens.

Though dual focus contact lenses for myopia control are not yet available in the United States, research is ongoing to evaluate the effectiveness of the lenses on a larger population of children.

Degenerative Myopia

In most cases, nearsightedness is simply a minor inconvenience and poses little or no risk to the health of the eye. But sometimes myopia can be so progressive and severe it is considered a degenerative condition.

Degenerative myopia (also called malignant or pathological myopia) is a relatively rare condition that is believed to be hereditary and usually begins in early childhood. About 2 percent of Americans are afflicted, and degenerative myopia is a leading cause of legal blindness.

In malignant myopia, the elongation of the eyeball can occur rapidly, leading to a quick and severe progression of myopia and loss of vision. People with the condition have a significantly increased risk of retinal detachment and other degenerative changes in the back of the eye, including bleeding in the eye from abnormal blood vessel growth (neovascularization).

Degenerative myopia also may increase the risk of cataracts.

Surgical treatment for complications of degenerative myopia includes a combination drug and laser procedure called photodynamic therapy that also is used for the treatment of macular degeneration.

Also, a recent pilot study found that an oral medicine called 7-methylxanthine (7-mx) was effective in slowing the elongation of the eye in nearsighted children ages 8 to 13. Studies of this type might eventually lead to an effective medical treatment for degenerative myopia.

Botulinum toxin for treatment of restrictive strabismus





SOURCE

Original Article
Botox y estrabismo restrictivo
Pilar S. Merino, Rebeca E. Vera, Laura G. Mariñas, Pilar S. Gómez de Liaño, Jose V. Escribano
Ocular Motility Section, Department of Ophthalmology, Hospital General Universitario Gregorio Marañón, Madrid, Spain
Received 27 June 2016, Accepted 01 September 2016
Abstract

Purpose


To study the types of acquired restrictive strabismus treated in a tertiary hospital and the outcome of treatment with botulinum toxin.

Methods


We performed a 10-year retrospective study of patients with restrictive strabismus aged ≥18 years who were treated with botulinum toxin. Treatment was considered successful if the final vertical deviation was ≤5 PD, horizontal deviation ≤10 PD, with no head turn or diplopia.

Results

We included 27 cases (mean age, 61.9 years). Horizontal strabismus was diagnosed in 11.1%, vertical in 51.9%, and mixed in 37%. Strabismus was secondary to cataract surgery in 6 cases, high myopia in 6, orbital fractures in 5, retinal surgery in 5, Graves ophthalmopathy in 4, and repair of conjunctival injury in 1 case. Diplopia was diagnosed in all patients, head turn in 33.3%. The initial deviation was 14 PD (range, 2–40), the mean number of injections per patient was 1.6 (range, 1–3), and the mean dose was 9.5 IU (range, 2.5–22.5). At the end of follow-up, diplopia was recorded in 59.3%, head turn in 18.5%, surgical treatment in 51.9%, and need for prism glasses in 14.8%. Outcome was successful in 37% of patients (4 high myopia, 3 orbital fractures, 2 post-surgical retinal detachment, and 1 post-cataract surgery). Mean follow-up was 3±1.8 years.

Conclusion

Vertical deviation was observed in half of the sample. The most frequent deviation was secondary to cataract surgery and high myopia. Treatment with botulinum toxin was successful in one-third of the patients at the end of follow-up.

Keywords
Acquired restrictive strabismus, Botulinum toxin, Graves ophthalmopathy, Myopic acquired strabismus, Strabismus secondary to cataract surgery
Introduction
Botulinum toxin was first reported as an alternative to strabismus surgery in 1980 by Scott.1 It can be used to treat acquired restrictive strabismus and proved to be successful or at least acceptable for treatment of thyroid strabismus.2

Most data in the literature are from isolated case reports or small samples describing the effect of treatment with botulinum toxin on acquired restrictive strabismus.3,4 The effect of botulinum toxin has been reported to be diminished in this type of strabismus,2 with a 2-month duration of effect and the need for repeat injections to achieve results similar to those achieved in comitant strabismus and oculomotor palsy.3 Most patients need surgery after administration of botulinum toxin.2 Results for thyroid strabismus have been good, with a 75% decrease in the initial deviation and a favorable outcome in 45.45% of cases.3,5 Botulinum toxin relaxes the inflammatory spasm that is characteristic of the acute phase of the condition, although its effect on the muscular fibrosis and contracture that appear during the clinical course is minimal.5Restrictive strabismus secondary to orbital disorders seems to respond well to botulinum toxin, especially in inflammatory conditions or myositis, although treatment has little effect in orbital fractures. The effect of botulinum toxin is independent of the initial deviation.6 Other types of restrictive strabismus secondary to retinal detachment surgery, cataract surgery, and strabismus surgery have been treated with botulinum toxin, with variable results.7–10


The benefit of botulinum toxin in restrictive strabismus is open to debate. Therapeutic response is associated with the type of deviation (vertical or horizontal), the extent of deviation, early treatment, age, and type of restrictive strabismus. The objectives of this study were to describe the types of acquired restrictive strabismus treated with botulinum toxin in a general tertiary hospital over a 10-year period and analyze the outcome of treatment.

Subject, material and methods


We performed a retrospective study of patients aged ≥18 years and diagnosed with acquired restrictive strabismus treated with botulinum toxin (Botox®, Allergan Inc., Irvine, CA, USA) between January 2002 and December 2012 in the Ocular Motility Section of our hospital. The study was performed in accordance with the Declaration of Helsinki and approved by the Ethics Committee of Hospital General Universitario Gregorio Marañón.

The inclusion criterion was acquired restrictive strabismus. For the purposes of the present study, restrictive strabismus was defined as any incomitant deviation secondary to Graves ophthalmopathy, high myopia, orbital conditions, and post-surgical complications (secondary to retinal detachment surgery, cataract surgery, and any other ocular surgery), with a positive forced duction test result and botulinum toxin as the initial treatment. Subsequent injections were not applied if an increasing deviation or patient objection were observed.

The exclusion criteria were congenital restrictive strabismus or fibrosis (e.g., Duane syndrome), infantile strabismus, previous surgery of extraocular muscles, and follow-up of fewer than 6 months.

The data collected from the patient's medical records were age, sex, type of deviation (vertical, horizontal, or mixed), etiology, diplopia, head turn, extent of deviation in primary position before treatment, time (months) from the onset of symptoms to the first injection, number of injections, total dose, and complications during administration. The other data recorded after administration of botulinum toxin were post-operative deviation in primary position, head turn, diplopia, need for prism glasses, surgical treatment, and follow-up from the first injection to the end of the study.

Vertical and horizontal deviations in primary position were measured using the simultaneous prism and cover test at far and near distance; the greatest deviation was used for the statistical data analysis. The forced duction test was performed in the operating room immediately before botulinum toxin was administered. The drug was always administered under topical anesthesia (lidocaine 2%) with cardiac and electromyographic monitoring in the operating room and an anesthesiologist present.

A successful outcome was considered to be a vertical deviation ≤5 PD, horizontal deviation ≤10 PD, absence of diplopia and head turn at the end of follow-up, with no need for additional treatment (prism glasses or surgery). A descriptive analysis was performed using IBM SPSS Statistics for Windows Version 22.0 (IBM Corp, Armonk, New York, USA).

Results

A total of 27 cases were included in the study. The mean age of the sample was 61.9±15.6 years (range, 29–83 years), and 52% were women (14/27). As for diagnosis, 51.9% had vertical restrictive deviation, 37% mixed vertical and horizontal deviation, and 11.1% horizontal deviation. Strabismus was secondary to cataract surgery with sub-Tenon anesthesia in 6 cases (22%), high myopia in 6 cases (22%), orbital fracture in 5 cases (18.5%), retinal detachment surgery in 5 cases (18.5%), Graves ophthalmopathy in 4 cases (15%), and conjunctival surgery in 1 case (4%).

Table 1 shows pre-treatment and post-treatment patient data. All patients had diplopia, and 33.3% had head turn at diagnosis. The initial deviation was 14 PD±9.9 (range, 2–40 PD). The mean number of injections per patient was 1.6±0.7 (range, 1–3), and the mean dose was 9.5±4.8IU (range, 2.5–22.5IU). One injection was applied in 55.5% of patients (15/27), 2 injections in 29.6% (8/27), and 3 in 14.8% (4/27). The mean time from onset of the symptoms until the first injection was 1.9±1.3 months (range, 1–6 months). The final deviation in primary position was 13.9±12.4 PD (range, 0–40 PD). At the end of follow-up, 59% of patients had diplopia, 18% had head-turn, 52% needed surgery after botulinum toxin, and 14% needed treatment with prisms. Outcome was successful in 10 patients (37%): 4 high myopia (40%), 3 orbital fractures (30%), 2 post-retinal detachment surgery (20%), and 1 secondary to cataract surgery with sub-Tenon anesthesia (10%). Table 2 shows successful outcome according to the type of restrictive strabismus. We have not recorded any complications during administration of botulinum toxin. The mean follow-up was 3 years±1.8.

Table 1.
Pre-treatment and post-treatment data.
Case Type Pathology D/T Time until first injection (months)asta No. of injections/dose (IU) Pre-treatment deviation in PP Final deviation in PP Final D/T S/P Result 
HM Y/Y 2/15.0 10 30 N/Y Y/N Bad 
HM Y/Y 2/17.5 N/N N/N Good 
HM Y/N 1/2.5 18 N/N N/Y Good 
HM Y/Y 1/2.5 14 N/N N/N Good 
HM Y/N 2/10 25 16 Y/N Y/N Bad 
HM Y/N 3/15 12 N/N N/N Good 
GO Y/Y 2/10 18 33 Y/Y Y/N Bad 
GO Y/Y 1/10 Y/N N/N Bad 
GO Y/N 2/10 12 Y/N Y/N Bad 
10 GO Y/N 1/5 12 Y/N Y/N Bad 
11 Post RD surg Y/N 1/5 N/N N/Y Good 
12 Post RD surg Y/N 1/5 12 30 Y/N Y/N Bad 
13 Post RD surg Y/N 1/10 25 40 Y/N Y/N Bad 
14 Post RD surg Y/N 1/7.5 40 Y/N N/N Bad 
15 Post RD surg Y/N 3/16 N/N N/N Good 
16 Fx Y/Y 1.5 2/10 10 16 Y/Y Y/N Bad 
17 Fx Y/Y 1/10 N/N N/N Good 
18 Fx Y/N 1/10 10 N/N N/N Good 
19 Fx Y/N 1/5 N/N N/N Good 
20 Fx Y/Y 3/22.5 30 35 Y/Y Y/N Bad 
21 Post cat surg Y/N 1/3 30 Y/Y Y/N Bad 
22 Post cat surg Y/N 1/4 30 25 Y/N Y/N Bad 
23 Post cat surg Y/N 3/15 N/N N/Y Good 
24 Post cat surg Y/Y 1/10 30 18 Y/N Y/N Bad 
25 Post cat surg Y/N 1/7.5 14 Y/N N/Y Bad 
26 Post cat surg Y/N 2/10 16 18 Y/N Y/N Bad 
27 Post conj surg Y/N 2/10 12 16 Y/N Y/N Bad 
Type: strabismus type; V: vertical; H: horizontal; M: mixed; HM: high myopia; GO: Graves ophthalmopathy; Fr: orbital fracture; post RD surg: post-retinal detachment surgery; post cat surg: post-cataract surgery with sub-Tenon anesthesia; post conj surg: post-conjunctival surgery; D: diplopia; T: torticollis; Y: yes; N: no; PP: primary position; S: surgery after treatment with botulinum toxin; P: need for prism glasses after treatment with botulinum toxin; IU: international units.

Table 2.
Successful outcome according to type of restrictive strabismus.
Type of restrictive strabismus Total (no. of cases) Successful outcome (no. of cases) Percentage 
High myopia 66.66 
Orbital fractures 60 
Retinal detachment surgery 40 
Graves ophthalmopathy 
Cataract surgery 16.66 
Conjunctival surgery 
The small sample size in each etiologic group did not enable us to draw conclusions about the influence of the etiology on the outcome of treatment.
Discussion

Acquired restrictive strabismus can be secondary to a series of conditions including high myopia, Graves ophthalmopathy, orbital conditions (fracture, myositis, metastasis), and procedures to correct retinal detachment, glaucoma, cataract, and conjunctival disorders. The treatment options recommended to eliminate deviation were surgery on the extra-ocular muscles and botulinum toxin.1–3,6,11 However, botulinum toxin is not as effective in restrictive strabismus as in comitant strabismus and oculomotor nerve palsy. More injections and doses are necessary.3 In our study, a favorable outcome was obtained in 37% of cases, which is lower than in other types of strabismus such as acquired and congenital esotropia (60–80%), intermittent exotropia (69%), and oculo-motor nerve palsy (70%).12–15

The effect of botulinum toxin depends on etiology. In our sample, a favorable result was not achieved in any of cases of thyroid strabismus (2 vertical, 1 horizontal, and 1 combined horizontal and vertical) at the end of follow-up. In every case, botulinum toxin was administered very early (1 and 2 months from the onset of symptoms). In 3 cases, 10IU were administered, and in 1 a total of 5IU. Lyons et al. 5 obtained good results in 15.78% of cases with botulinum toxin, and the deviation decreased by 75%, although 68.42% of patients needed strabismus surgery after the injections. The benefit obtained with botulinum toxin could be associated with the relaxation of the inflammatory spasm that is characteristic of the acute phase of the illness. Botulinum toxin is less effective in muscle fibrosis and contracture.5 Wu et al.3 reported resolution in 15 of 33 cases (45.45%) and decreased deviation in 12 (36.36%). Administration must be early, with a mean dose of 8IU and subsequent injections. Another benefit of botulinum toxin is the decrease in intra-ocular pressure in primary position and in supraversion 2–4 months after injection in the inferior rectus.16,17

At the end of follow-up, outcome was successful in 4 of 6 cases (66.66%) of strabismus associated with high myopia. Treatment was applied early in each case (within <6 months after the onset of symptoms), and the total dose was 2.5–17.5IU. Few publications in the literature analyze treatment with botulinum toxin for acquired restrictive strabismus secondary to high myopia. The best results are achieved in young patients with poor binocular vision and severe amblyopia because of the neurosensory adaptation following therapy with botulinum toxin. Botulinum toxin has also proven effective in post-surgical over-correction and under-correction.11,18–20

Botulinum toxin is not effective for restrictive strabismus secondary to ocular surgery for several reasons, including extensive fibrosis and displacement of the superior and inferior oblique muscles after surgery to correct glaucoma and retinal disorders. The frequency of successful outcome varies widely (15–85%).8,21 The sub-Tenon anesthesia used in cataract surgery is responsible for diplopia and restrictive strabismus secondary to muscle contracture, fibrosis, and palsy. Botulinum toxin is effective in only 25% of cases of muscle palsy, before development of muscular fibrosis, which is frequent and has an early onset in older patients.7 In our study, outcome was successful in 40% (2/5) of cases secondary to retinal surgery, in which botulinum toxin was injected early (1–4 months after onset of symptoms). Six cases were secondary to sub-Tenon anesthesia for cataract surgery, although outcome was successful after early injection (1 and 2 months from the onset of symptoms) in only 1 case (16.66%).

Restrictive strabismus can be secondary to orbital conditions such as fractures, myositis, neoplasm, and metastasis.4 In our sample, outcome was successful in 3 of 5 cases (60%) of orbital fractures after early treatment with botulinum toxin (within <3 months), with total doses of 5–22.5IU and 1–3 injections. Lee et al.6 reported good results in 69% of patients with orbital conditions, 67% of patients with myositis, and 33% of patients with fractures. The benefit was independent of the angle of deviation.

Our study is limited by its retrospective nature and the small number of patients in each group. In addition, it was not possible to analyze the effect of etiology on outcome. Nevertheless, the follow-up period was long enough to draw conclusions about the stability of botulinum toxin for treatment of acquired restrictive strabismus.
In conclusion, half of the patients in this sample had vertical deviation. The most frequent etiology was sub-Tenon anesthesia for cataract surgery and high myopia. Botulinum toxin was effective in only one-third of the patients at the end of follow-up, and outcome was similar for high myopia, orbital fractures and retinal detachment surgery.

The results were worse in cataract surgery, and botulinum toxin was not effective in Graves opthalmopathy and conjunctival surgery. Half of the patients needed extra-ocular muscle surgery after treatment with botulinum toxin. Botulinum toxin can be considered a complementary or alternative approach to surgery in some complex cases of acquired restrictive strabismus.

Conflicts of interest
The authors have no conflicts of interest to declare.

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This study was presented as an oral communication at the 24th Spanish Strabismus and Pediatric Ophthalmology Meeting in Cordoba, Spain, April 2016.

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