Thursday, 18 December 2014

What’s so special about specialty lenses?

Advancements in specialty lens manufacturing have made it possible for more patients to wear contact lenses

December 16, 2014
By David I. Geffen, OD, FAAO

Increasingly, many practitioners in today’s practices are using specialty contact lenses. These contact lenses historically have been viewed as hard to fit, difficult to find, and much higher in cost. Let’s look at what’s so special about specialty contact lenses.

Extended-range lenses

What determines that a lens is a “specialty” lens? There are many categories of these lenses and way too many to list every brand and manufacturer. The most common specialty lenses are the lenses which fall out of the parameters of normally available lenses in a category. These would be lenses that are higher in spherical power than the company normally manufactures. Biofinity (CooperVision) is a typical lens in this category. Biofinity spheres are available from +6.00 D to -10.00 D—a very large range, which is good for the vast majority of patients. The Biofinity XR or extended range lens is now available from +15.00 D to -20.00 D.

Dr. Geffen: The value of a contact lens patient

Most doctors and manufacturers consider these extended-range contact lenses to be specialty lenses. These lenses allow us to serve the need of our patients who fall out of the normal parameter ranges. These are ordered and manufactured on an as-ordered basis at this time so you may need to wait up to a few weeks to receive these lenses. There are also a number of smaller specialty lens companies that manufacture lenses on an as-needed basis. These companies have thrived in providing eyecare practitioners with lenses with most any power or base curve or diameter a patient may need. They also can get these lenses to patients in a few days.

Toric and multifocal lenses

Toric lenses are the next category of specialty lenses. Like spherical lenses, the major manufactures have a limited power range typically from +6 to -9 with 3 or for cylinder powers. The typical cylinder limit for readily available toric lenses is -2.25 D. Smaller labs are able to fill in the gaps and make a toric lens for our patients with almost any axis or power we need. These lenses are available in a few days to our patients.

Multifocal lenses are also available in many custom designs from small contact lens manufacturers. Some ingenious designs have come out of these labs and we can serve many more patients than ever before.
Lenses for irregular corneas

Now let’s cover some of the truly special designs coming out of smaller labs. Lenses for irregular corneas are changing the way we think about providing excellent vision and comfort to our patients. These lenses have provided a way for doctors to care for those patients who cannot or will not wear rigid gas permeable (RGP) lenses. Bausch + Lomb brought us the Kerasoft soft contact lens for irregular corneas. Kerasoft is available in a wide range of custom parameters and base curves to correct the irregularities in the cornea caused by keratoconus, surgical imperfections, and disease.

Dr. Geffen: R&D needed for new gas perm car systems, materials

Another lens in this category is NovaKone from Alden Optical, one of several specialty contact lens labs that have made great innovations in soft lens designs. NovaKone comes in any custom base curve you would like and has different center thickness parameters to correct for irregularities. There are several other lenses of these types from great-minded individuals creating new and improved contact lenses for every need.

What makes them special

So why are these lenses special? They seem to be treated as devices only certain doctors are allowed to use. They have a reputation as being difficult and eating up too much chair time for many doctors. However, because specialty lens companies are utilizing very advanced manufacturing processes, the reproducibility and quality has never been better. You can have the confidence that the patient will not be calling your office complaining about the lens. These lenses do take a little more time and thought. Specialty contact lens company consultants are excellent partners in your practice—they want you to succeed and make it as easy as possible. The cost of the lenses is higher than standard lenses, and this is a concern for many doctors. Remember that these patients know that they are not the usual contact lens wearer and know that they have special needs. As such, they expect to spend more for both your expertise and the cost of the device. Optometrists are notorious for not charging enough for our expertise and time. We need to be compensated for the extra knowledge and study we do to learn about these special lenses and the time we spend without patients.

So what is so special about specialty contact lenses? I can answer that question only one way. These lenses are so special because we are truly changing the life of patients who has sought our expertise to improve their quality of life!

Saturday, 15 February 2014

Tips for handling digital eye strain

Digital eye strain is caused by the overuse of digital devices such as computers and smart phones. Because these electronic devices are designed to be used and held within close range of the eyes, after a while, the eyes become strained as they continue to refocus to process the images on the digital screen.

According to organizations like The Vision Council, more than 70% people don’t know or don’t believe they are at risk for digital eye strain; however, anyone who is in front of a digital screen is vulnerable. Red eyes, twitching eyes, dry eyes, blurred vision, headaches, neck pain, decreased productivity and increased work errors, fatigue from staring at a digital screen, and straining to see small fonts and images are some of the signs and symptoms that occur when experiencing digital eye strain.

“In our fast-paced society, most people use a computer throughout the day while they’re at work, and they also go online to communicate with friends, read books, and even pay bills.”

“It’s just the way we operate in the 21st century. Nevertheless, people can stay digitally connected and also maintain the health of their eyes.”

Optometrists suggests following tips for avoiding digital eye strain:

1. Follow the “20-20-20 rule.” Be mindful of the amount of time that is spent looking at a computer screen without taking a break. Every 20 minutes, take a 20-second break and look at something that is 20 feet away. Looking far away relaxes the focusing muscle inside the eye and reduces eye fatigue.

2. Reduce glare. People often see reflections from objects around their computer on their computer screen. Install an anti-glare screen on the computer monitor to reduce glare on the screen. Cover windows with drapes and blinds, and use a computer hood to block some of the overhead and peripheral light. Get anti-reflective (AR) coating on eyeglass lenses.

3. Work in proper lighting. When looking at a digital screen, the surrounding light should be half as bright as what is typically found in most offices. Try to position the computer screen so windows are on the side (instead of in front or behind) the computer screen. If the interior lighting is a concern, consider reducing the number of fluorescent tubes that are installed above the computer. Also consider turning off the overhead fluorescent lights in the office and use lamps that provide halogen or incandescent lighting, or switch to lower intensity bulbs.

4. Blink often. People tend to blink less often when they look at a computer screen—approximately one third less often as they normally blink—and a lot of the blinking that takes place when looking at a digital screen are only partial lid closures. Blinking less often can cause the eyes to become dry. To reduce the chances of experiencing dry eyes when looking at a digital screen, try this exercise: Every 20 minutes, blink 10 times by closing the eyes very slowly, as if falling asleep. This will moisten the eyes, and it will also help the eyes refocus.

5. Revise the workspace. When working on a computer, people often look back and forth between the computer screen and a printed page, which can cause eye strain. To alleviate the stress and strain on the eyes, put the printed pages on a copy stand that is next to the computer monitor. Make sure the paper on the copy stand is well-lit by using a desk lamp. Poor posture can also lead to problems with clearly seeing a digital screen. Consider purchasing ergonomic furniture where the computer screen is positioned 20 to 24 inches from the eyes. The center of the digital screen should be 10 to 15 degrees below the eyes.

6. Get a regular comprehensive eye exam. Computer users should have eye exams once a year. Before the exam, be sure to measure the distance between the eyes and the digital screen. Share that measurement with the eye care provider, and remember to let the doctor know how often computers and smart phones are used. 

Friday, 14 February 2014

Bielschowsky's head tilt (3 step) test

When a healthy individual tilts their head, the superior oblique and superior rectus muscles of the eye closest to the shoulder keep the eye level. The inferior oblique and inferior rectus muscles keep the other eye level. In patients with superior oblique palsy, the superior rectus muscle’s action is not counteracted by the superior oblique muscles. This leads to vertical deviation of the affected eye when the head is tilted towards the effected eye. However, there is no deviation when the head is tilted towards the unaffected eye because the superior oblique muscle is not stimulated in the effected eye, but rather it is stimulated in the unaffected eye. When there is a discrepancy in ocular deviation based on which way the head is tilted, the patient is diagnosed with unilateral palsy of the superior oblique muscle due to damage in the Trochlear Nerve.

People with superior oblique palsy on one side experience double vision, which is improved or even abolished by tilting the head towards the shoulder on the unaffected side. Tilting the head towards the shoulder on the affected side will make the double vision worse by causing increased separation of the two images seen by the patient.

Fourth Nerve Palsy

A fourth nerve palsy typically causes diplopia that is worse in downgaze; hence, patients almost always report diplopia (or the tendency to close 1 eye) while reading. In some cases, examination of the affected eye reveals limited downgaze in the adducted position, but, in most cases, ocular motility appears grossly normal. Accordingly, it is essential to perform cover-uncover or Maddox rod testing to demonstrate a hypertropia that worsens on contralateral downgaze. Ipsilateral head tilting usually increases the vertical strabismus, and, therefore, patients typically (subconsciously) tilt their head to the opposite side to avoid diplopia.

The Parks-Bielschowsky 3-step test is a time-honored algorithmic approach to identifying patterns of ocular motility that conform to dysfunction of specific vertically acting extraocular muscles. The 3 steps are

1.     Find the side of the hypertropia.
2.     Determine if the hypertropia is greater on left or right gaze.
3.     Determine if the hypertropia is greater on left or right head tilt.

Beyond these 3 steps, it is also useful to determine if the vertical separation is greater in upgaze or downgaze (a fourth step) and check for relative cyclotropia.
The 3-step test is most helpful in determining whether a vertical strabismus conforms to the pattern of a fourth nerve palsy; for example, a right fourth nerve palsy shows right hyperdeviation that worsens on left gaze, right head tilt, and downgaze, with relative excyclotropia of the right eye.

Occasionally, a skew deviation mimics a fourth nerve palsy on the 3-step test but can distinguish itself by nonconformity to these rules. Practically speaking, the specific muscle(s) involved and the etiology of a vertical strabismus not due to a fourth nerve palsy is often not resolved by the 3-step plus fourth step test, because acquired vertical strabismus is often the result of the dysfunction of more than one muscle. In particular, thyroid eye disease, myasthenia gravis, or dysfunction of multiple ocular motor cranial nerves produces a wide variety of nonspecific patterns of ocular motility. The reliability of the 3-step test in identifying patterns of vertical strabismus lessens somewhat over time because of the phenomenon known as “spread of comitance”.
Bilateral fourth nerve palsy should always be considered whenever a unilateral palsy is diagnosed, especially after head trauma. Bilateral fourth nerve palsy presents with:-
  • ·      crossed hypertropia (ie, the right eye is higher on left gaze, and the left eye is    higher on right gaze)
  • ·        Excyclotorsion of 10° or greater (each eye rotates outwardly; best measured with  double Maddox rod testing)
  • ·         a large (≥25 D) V pattern of strabismus
Brazis PW. Palsies of the trochlear nerve: diagnosis and localization—recent concepts. Mayo Clin Proc. 1993;68(5):501–509.

Fourth nerve palsies are often congenital. An anomalous superior oblique tendon, an anomalous site of its insertion, or a defect in the trochlea are now recognized as causes of some congenital fourth nerve palsies; similarly, some cases of presumed congenital fourth nerve palsy are secondary to a benign tumor (eg, schwannoma) of the fourth nerve. Patients are often asymptomatic until the fourth to sixth decades of life, when their vertical fusional amplitudes diminish and diplopia develops. Most patients maintain a chronic head tilt. The long-standing nature of the head tilt can often be confirmed by reviewing old photographs . Patients with a long-standing fourth nerve palsy have a relatively large vertical fusional range (>3 prism diopters).

In patients older than 50 years, isolated fourth nerve palsy is typically caused by micro-vascular ischemic disease, and function always improves and typically resolves within 3 months. The fourth nerve is particularly vulnerable to closed-head cranial trauma due to the unique dorsal midbrain crossing anatomy. In addition, the fourth nerve can be damaged by disease within the subarachnoid space or cavernous sinus.

Diagnostic evaluation for isolated, non traumatic fourth nerve palsy usually yields little information because most cases are congenital, ischemic, or idiopathic. In patients in the vasculopathic age group, a full medical evaluation looking for vascular risk factors, including diabetes, hyperlipidemia, and hypertension is appropriate. Older patients should be followed to ensure recovery. Lack of recovery after 3 months should prompt neuroimaging directed toward the base of the skull to search for a mass lesion. Other possible causes of an acquired vertical strabismus include orbital restrictive syndromes (eg, thyroid eye disease or previous trauma). Skew deviation, partial oculomotor nerve palsy, or myasthenia gravis should be considered in atypical cases.