Tuesday, December 18, 2007

6.5 Vision rehab setup

(from ablezone.com)
Traditionally, low vision care is a major component of tertiary eyecare. Patients, in general, have already exhausted most if not all medical and surgical options and their vision may still be deteriorating. These patients are usually found in eye hospitals and large retina practices. For them, stabilization of ocular conditions coupled with maximal/optimal vision correction remains a life-long process.

The definition of low vision is, however, rapidly changing. It no longer denotes legal blindness or worse, rather it now includes patients with BCVA of 20/80 or less and whose vision cannot be further restored. For example, patients with cataracts plus AMD or diabetic retinopathy, or patients with post-RK ghosting and/or polypolia. Thus low vision cases are now often seen in a primary care office.

A common misconception is that since the patients cannot achieve 20/20 vision, the accuracy of refraction is no longer crucial. In fact, having lost some vision, the patients are extremely sensitive to changes, however small. Any loss is potentially devastating and gain a cause for celebration. Part of this maybe psychological; however, the change can often be attributed to the development of another sensitized areas (outside of the macula/fovea) for vision. It is the doctor's responsibility to identify these areas and maximize the patients’ vision accordingly.

The ultimate goal of low vision care is really the improvement of the patient’s quality of life. For some patents, it is also crucial to integrate vision rehab with occupational therapy, so that they can be productive again.

Low vision care is an extension of refraction including contact lens application. The main principle is magnification without compromising the available field of view. In other words, if the magnification is such that it allows the patient to read, but only one word or even only one character at a time, then it will be very difficult to scan the whole line of text, let alone reading at a reasonable speed.

The availability of low vision devices has also increased from optical magnifiers and telescopes to computerized readers, self-focusing telescopes, satellite-guided navigators, all the way to macular relocation, implanted telescopes, and ocular and cerebral electro-implants. The increasingly bionic approach can benefit patients with profound loss of vision, whether it can serve or is accepted by low vision patients remains to be seen.

Here, we will describe a typical set up of a low vision care office:

Patient flow: Wherever applicable, Braille signs must be posted. For example, in the elevators, Braille floor number signs must be posted next to the push-buttons. Also, Braille directions to the clinic should be affixed onto the walls at waist level along the way to the clinic. The clinic also must be wheel-chair accessible. The patient then enters the front desk and waiting area and proceeds to register.

Pre-test room: An Ophthlamic Technician should then take history, both visual and medical. Especially important is previous history of eye treatments and/or surgeries. Previous records are important, in fact, crucial for further evaluation. Record patients’ current low vision devices and their effectiveness. And what the patients’ expectations for the visit.

Visual acuities, both aided and unaided and most important pin-hole acuity must then be taken. This is done with standard Snellen charts or equivalent. Patients should NOT be dilated at this point. Dilate only if the patient needs a retinal exam. Also, no applanation/indentation tonometry (this may distort the cornea), save this for later. Patients with POAG and silicone oil must have tonometry before conclusion of each visit.

Do auto-refraction/keratometry (note the shape of the mires) if practical. A hand-held auto-refractor may be needed for children.

Visual analysis/eye exam room: A skilled refractionist then evaluates the patients. For this room, in addition to the standard Snellen charts, a low-vision chart designed for 1m testing distance is required. For children, a childrens’ chart for 1-3m will suffice. For infants, use a separate preferential looking chart.

Accurate refraction is key to successful management of low vision cases. The following equipment is required:

Phoropter with chair and stand together with a slit-lamp
Complete set of trial lenses (including prisms) and a trial frame
Retinoscope with halogen lamp
Direct opthalmoscope with halogen lamp
Binocular indirect ophthalmoscope
Volk lenses (at least one +78D lens)
Complete set of LV trials (for example, that from Eschenbach)

Record best correctable vision and reasons for sub-optimal vision. Propose low vision aids and/or further tests.

Low vision aids: for example, telescopes, microscopes
Special optical aids: for example, prism for eccentric viewing or avoiding diplopia
Specialty contact lenses that include lenses for aphakia, aniridia, keratoconus, complications after corneal transplants or refractive surgery, contact-lens telescope
Electronic devices: for example, desk or head-mounted CCTVs

Special testing room: This room should be equipped with a special visual field testing instrument, ideally a scanning laser ophthalmoscope. In severe visual loss, SLO provides information on areas of preferential viewing and the angle of deviation from the macula, so that the amount and axis of prism correction can be determined.

A high percentage of patients suffer from glare sensitivity. A glare testing device is also needed in order to quantify the need for shields.

Education room: An ophthalmic assistant teaches the patients how to use the low vision aids. Most patients will require instructions or the devices often go unused.

Occupational therapy room: For those with severe loss of vision, an Occupational Therapist teaches assistive living with the goal of achieving independence. This room is equipment with a kitchen with utensils designed for LV patients.

A computer area for learning skills for navigating the Internet and improving office productivity.

For the immediate future, assistive technologies should be developed for the use of ATMs, PDAs, and cell phones. These are, not surprisingly, what the low-visoin patients have the most difficulty with at present time. Some never even have the opportunity to access these devices.

1 comment:

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Taking Care of Your Vision