Low vision optometry is not about handing patients magnifier after magnifier until they can see. Rather, it is a series of crucial assessments and decisions based on these assessments to offer patients functional solutions to their visual problems.
The following six-step approach allows me to meet each patients needs:
1. Ask the patient what his or her lifestyle goal is. Does the patient want to read, drive, perform a specific occupation, etc.?
2. Determine what specific tasks the patient needs help with to achieve that lifestyle goal. Such tasks might include driving, reading, writing and cooking.
3. Assess the healthy ocular tissue that remains. Many patients fixate centrally through damaged tissue. These patients usually complain of a large spot or hole in their vision. For these patients, locate healthy tissue close to the macula, and train the patient to view with this area, known as the eccentric fixation locus.
Then, determine the direction of eccentric fixation and the size and sensitivity of the best retinal locus (BRL). This is usually different than the preferred retinal locus (PRL) when a PRL exists. The PRL is an eccentric fixation point to which the patient gravitates naturally. The BRL offers acuity that may be equal to or slightly below that of the PRL, but this area generally is much larger and more functional.
4. Decide which tasks are achievable based on the assessment of the patients ocular tissue.
5. Choose the appropriate low-vision device or series of devices. There are no hard-and-fast rules here. I always seek to design some form of optical system that provides patients with the greatest amount of latitude and function.
6. Initiate a program of rehabilitative therapy using the device(s). For example, if you prescribe a telescope, teach the patient how to focus the telescope properly and how to determine where to focus it. Also, instruct the patient whether to use the telescope in conjunction with a pair of glasses or to take the glasses off.
The following are my most memorable cases in which this six-step approach was successful.
Telescopes Make the Grade
A 36-year-old male presented with a goal of completing his high school education and going on to college. The problem? As a child, he sustained several retinal detachments in his left eye that left him completely blind in that eye. Also, his right eye had a large central scar secondary to toxoplasmosis, which occurred at age 7 and left him with only light perception. He could see shadows and, occasionally, a complete figure.
Because of these visual problems, the patient used braille readers and auditory cues. He hated this form of education, he said, and subsequently acted out toward his teach-er and family. He dropped out of school at age 16.
Examination revealed an unaided central visual acuity of 10/600 in his right eye using the Designs for Vision Feinbloom chart. So, how did this patient have a visual acuity? He actually had some level of residual vision that was missed and was represented as only light perception. His refraction was +1.50 -0.75 x 180 O.D. With the refraction and a 15-degree superior eccentric fixation, he was able to improve his vision to 10/120 O.D.
While this may appear to be a very dramatic improvement with such a small prescription change, realize that this represents a change in this patients fixation as well. I see this every day. Patients present speaking of prior examinations that demonstrated light perception or finger counting at 3 feet. Frequently, when I stand 10 feet in front of these patients with the 10/700 Designs for Vision #7, they say they cannot see it when they look directly at it. But, when I move it off center, I often find that their vision improves to 10/100 in some eccentric viewing postures. Thus, dramatic improvements are seen without any lenses at all.
I fit this patient with a 5.5x Beecher Mirage telescope (Beecher Research), a high-powered yet lightweight, head-borne binocular system that offers an expanded field of view. I chose this device for two reasons: First, the patient required a device that would provide adequate magnification and field of view. My goal was to get this patient to 10/20. With an acuity of 10/120, I needed approximately 6x magnification. But, Beecher Mirage telescopes are not available in 6x, so I used 5.5x, which worked nicely. Second, because the device is head borne, the patients hands were free to write and take notessomething crucial to his education. The patient was able to see 10/20 at distance.
From there, I fit him with a 2.2x full-diameter telescope (FTDS) with a +10.00D telemicroscopic reading cap. I choose 2.2x because this device provides a relatively large field of view at the required level of magnification when compared to those of reading telescopes or expanded-field reading telescopes. It permitted the patient to read 1.0M continuous textthe size used in most of the publications that he would be utilizing. As a result, his near point acuity jumped to 1.0M type at a focal distance of four inches. His prior near acuity was between 6.0M and 8.0M single letter.
Patient Betty Langfried acclimates to her Full Diameter Telescope (FDTS). An FDTS typically provides patients with the appropriate field of view and is easy for the patient to use.
Patient Carol Buttazzonni tries out her Beecher Mirage binocular telescopic system to see if it provides her with better distance vision.
A 38-year-old male presented with a desire to return to driving and work. He suffered a stroke, which left him with a bilateral right hemianopia. He also exhibited some sparing of the macula in the right eye. As a result, his horizontal visual field was just below 105 degrees35 degrees shy of Flor-idas drivers license requirement.
His vision problems also caused him to lose his accounting job, which required him to drive to meet with clients. I sensed that he also lost some self-esteem.
I evaluated the patient and fit him with a Visual Field Awareness System, or VFAS (Rekindle/Gottlieb Vision Group). This sectorial prism system is mounted on spectacles on the side of the vision loss, providing improved optics over traditional press-on prisms.
Patients use the Rekindle system much as we would the rear-view mirror in a car. We dont look through the rear-view mirror all the time; rather, we glance into it to obtain information about what is behind us. The patient glances into the Rekindle prisms to obtain information about what is on his side in his blind field.
I chose this device because traditional Fresnel prisms didnt yield adequate resolution, and I have had past success with the Rekindle system. This gave him a refraction of plano -1.25 x 010 for 20/20 O.D. and -1.25 -1.00 x 180 for 20/30 O.S.
The patient said he liked to wear contact lenses most of the time, but neither his contact lenses nor spectacles provided him with the field he needed to pass the driving test.
His VFAS consisted of an 18.00D base-out (BO) prism O.D. I chose a frame that had interchangeable magnetic clips so that when he wore his contacts, he could put the glasses on to expand his field. (The 18.00PD lenses cannot be integrated into contacts.) The clip also provided him with sunglasses.
I made two additional clips; one clear and one tinted. Each clip incorporated his refraction so that he could still add his refraction to the VFAS when he didnt wear his contact lenses and be functional with the glasses.
The patient underwent three months of therapy that involved fixation, tracking and versions, and techniques in scanning. After the therapy, he passed the Goldmann field test with a horizontal field of 142 degrees.
At that point, he attended a special school for driver training for two weeks. He was recertified to obtain his drivers license, and he went back to his former job shortly thereafter. He has been driving for the past six years, accident free.
Better Vision For Bookkeeper
An 80-year-old female presented with the desire to resume her bookkeeping duties. She was a bookkeeper for a company for 25 years but was relegated to receptionist after a company evaluation revealed she was unable to perform her duties due to her sight. She said she felt that the company had given her this new position out of charity, and she did not like that.
The patient was pseudophakic O.U. and had aided acuities of +0.50 -0.75 x 075 for 10/100 with 10 degrees right eccentric fixation O.D. and plano -1.00 x 090 for 10/80 with 10 degrees of left eccentric fixation O.S. With a +2.50D add, she was able to read 3.2M print O.D. and 2.0M print O.S.
I fit her with a 1.7x FDTS for the left eye because she didnt require a large amount of magnification to function at her desk. The 1.7x FDTS provided an expanded field of view for use at the computer and at her desk.
I prefer using the least amount of magnification that will permit the patient to meet her functional goals yet provide the widest possible field of view and greatest comfort. As a result of the 1.7x FDTS, she was able to see 10/40 O.S. at distance. And, a +6.00D cap allowed her to read 1.0M type at near, while a +3.00D cap allowed her to read 1.25M type at 14 inches.
So, I had a 1.7x FDTS telemicroscopic system created for her, in conjunction with Designs for Vision. Our staff occupational therapists provided her with the appropriate fixation training, which encompassed fixation, versions and tracking with her specific device using the +6.00D cap at near point. The therapy lasted five weeks. Once she became comfortable with the use and function of her telemicroscope system, I asked the company to create a split cap of +3.00D/+6.00D to permit her to view the computer and read text while at her desk.
This treatment enabled her to return to her bookkeeping job. She was able to function for almost two years, but then she developed age-related macular degeneration (AMD) and suffered a retinal hemorrhage that caused a sudden decrease in her vision.
I then added the ZoomText Synapse Adaptive (Ai Squared), a computer magnification program, and a closed-circuit television (CCTV) to her regimen. These devices provided higher levels of magnification that allowed her to see the levels of material she needed to continue functioning at her job.
The CCTV reading machine provides great levels of magnification for patients who cannot obtain adequate amounts with spectacles or who have physical issues, such as tremors.
Unfortunately, her general health began to suffer. She retired in 2001 at age 85. Today, at age 89, she still uses the CCTV along with a 2.2x FDTS and +6.00D cap, much the same format as she had at work.
Scopes Bring Hope
A 70-year-old male presented with the desire to read and bowl. He had dry AMD in each eye and nuclear sclerosis of 0.5/4.0 in each eye. (The scale is 1 to 4 in which 4 equals a dense mature cataract that may only provide a small amount of light transmission, and 1 equals early brunescense. Therefore, this was only a slight appearance of an early yellowish-brown tint to the lenses.) His aided refraction and visual acuities were +2.25 -0.50 x 090 for 10/60 with a 10-degree left eccentric fixation O.D., and +1.75 -0.50 x 090 for 10/100-1 with a 10-degree left + and a 5-degree superior eccentric fixation O.S.
I addressed the reading difficulty with a 1.7x FDTS, which he already used to watch TV. The device provided him with sufficient magnification. I added a +6.00D reading cap, which allowed him to comfortably read 1.0M of continuous type.
For bowling, I fit him with a 5.5x Beecher telescope. This allowed him to look under the scope to view the spots on the alley and then look through the scope to view the pins at the end of the alley.
The patient was very happy with this treatment until last summer when he decided to tour Europe. He didnt want to wear the Beecher scope full-time, but he wanted the same level of acuity with a lighter-weight unit that could be worn as spectacles.
The VES manual focus Bioptic telescope (Ocutech) met his needs perfectly. I fit him with a 6.0x telescope, which he took with him to Europe. These spectacles also integrated Transitions filter 450 (yellow) bifocal lenses (Chadwick Optical). These lenses were then sent to Ocutech to be integrated into the fabrication of the system.
Patient Beth Fligman wears an Ocutech manual focus VES-K telescope mounted in the bioptic position. This device enables her to view objects in the distance.
The cases illustrated above are not only memorable, but testaments to the effectiveness of the six-step approach. If you are unable to carry out these crucial steps, refer your low vision patient to a nearby colleague who can, or consider taking low vision courses to update your professional skills.
Dr. Gannon is the director of the Low Vision Institute in Fort Lauderdale, Fla., where he has practiced for 27 years. He is a past chair of the Low Vision Committee of the Florida Optometric Associa-tion and a panel member of the Florida State Division of Blind Services. He is also a director of the American Foundation for Visual Rehabilitation and the Florida Council of Citizens with Low Vision.