Utilizing Prism in Primary Care Practice Sandra M. Fox, OD South Texas Veterans Health Care System Polytrauma Rehabilitation Center at San Antonio [email protected] Disclosure Statement: Nothing to disclose FUN WITH PRISMS! WHY DO WE LOVE PRISMS?

Since a prism can shift images, it is a very useful tool in optometry where we have a need to shift images so people no longer see double or can more easily be aware of objects in their peripheral vision. FRESNEL PRISM • Press on prism • A piece of plastic with diffraction rings that give it a prismatic effect. • Has a base and an apex and works just like a “real” prism. • Available in 1 – 10 diopters in 1 diopter increments, 12,15, 20, 25, 30, 35 and 40 diopters. • Costs ~ $25 • The greater the power, the more it blurs the vision. • It is usually applied to the back surface of the lens in the glasses. FRESNEL LENSES FRESNEL PRISM ADVANTAGES • Allows us to trial prism before ordering glasses with prism ground in (costly). • Can be used in very high powers when a conventional prism would be too thick. • Can continue to change the power as the 2/2 CN palsies improves with time. • The blurring effect is helpful when unable to neutralize the 100%. • Can be used for diplopia as well as with visual field loss. DISADVANTAGES

• Compromises acuity, especially with higher power prisms • Glare and chromatic aberration • Difficult to clean, fall off • Cosmesis. • Takes longer to cut the prism than it does to determine how much prism is required! DIPLOPIA – DOUBLE VISION

• 4 basic categories of diplopia that we encounter in practice are acquired strabismus, decompensated phoria, mechanical diplopia and monocular diplopia. • Can use prism in the first 3. • Most of the diplopia that we encounter in the outpatient population falls into the first 2 categories. PRIMS USE IN ADULT DIPLOPIA

• Gunton and Brown • Current Opinion in Ophthalmology 2012 • Review summarized the results of prismatic correction in adults based on the cause of diplopia • Main findings: - Satisfaction with prismatic correction is achieved in ~80% of all adult patients with diplopia - Careful selection of patients for prism correction, management of their expectations, and continued follow-up to monitor the symptoms are critical to success. NONSURGICAL TREATMENT OF DIPLOPIA

• Bartiss, M. Current Opinion in Ophthalmology. 2018 • Recognizes the importance of utilizing non-surgical approaches to treating diplopia • Successfully treating diplopia decreases the risk of injuries and maximizes independence and quality of life and these concerns are especially important as patients age. CRANIAL NERVE PALSIES

The cranial nerves most often affected are CNIII (oculomotor), CNIV (trochlear) and CNVI (abducens).

CRANIAL NERVE PALSIES

• Cranial nerve palsies are very common in patients with vascular disease, in particular diabetes (the trifecta – diabetes, hypertension, high cholesterol) and in brain injury. • Sudden onset diplopia. • Will often improve with time, usually within 3-6 months. • In the past, would just patch but that is particularly not appropriate for a patient in a rehab setting where the goal is to get back to walking and performing activities of daily living. MANAGING CRANIAL NERVE PALSIES • We can use a Fresnel prism to eliminate the diplopia by determining the amount of prism that is necessary to achieve single vision. • A Fresnel prism is placed on the lens in front of the deviating eye. MANAGING CRANIAL NERVE PALSIES

• If both a horizontal and vertical deviation (CN3 and 4), can use 2 prisms – highest power on the back of the lens, lower power in front or an oblique prism. • Monitor monthly and can change the power as needed. • The prism blurs the vision slightly, which is helpful if we cannot eliminate the diplopia completely. • If the palsy remains after 6 months, can consider surgery or have the prism ground in the glasses at that time. DETERMINING THE AMOUNT OF PRISM

• Measure the amount of deviation in the phoropter by having the patient look at a single letter and use rotary prisms until the image is single. • Verify outside the phoropter using a prism bar – often will require less prism in free space. • Use loose prism to ensure the patient sees single at all distances with the prism. • Demonstrate a fresnel prism. • May need to place the prism on the non-dominant eye if the blur is an issue. STEPS TO DETERMINING PRISM NEEDED Phoropter Prism Bar STEPS TO DETERMINING PRISM NEEDED

Loose Prism Fresnel ASSOCIATED PHORIA

• Fixation disparity is a small ocular misalignment of one eye or both eyes when the two eyes are fixating on an object during normal binocular vision. • The amount of prism which is required to reduce the fixation disparity to zero has been called “the associated phoria”. • Since you are measuring the misalignment binocularly, can prescribe the amount of prism exactly. NEAR PHORIA TESTS CASE #1

Cranial Nerve Palsy CASE #1

• 58 yo male hemorrhagic CVA 2 months prior, inpatient at Polytrauma Rehabilitation Center, aphasia, still in post traumatic amnesia. Seen bedside. • Currently using +1.50 OTC reading glasses • Distance vision fine, horizontal diplopia since CVA, dizziness. • Unaided DVA OD: 20/30 OS: 20/40-1 PHNI OU: 20/30-2 • Unaided NVA OD: 20/160 OS: 20/100 OU: 20/80 CASE #1 • Cover Test: Distance and near: Right hypertropia, XP • Fixation: slow with multiple fixations • EOMs: jerky, end gaze (-)diplopia • Nystagmus in downgaze • Damp Autorefraction: • OD: +0.25+0.75X158 • OS: +0.25+0.75X 115 • Cover Test with prism Bar: 14^BU OS • Subjective with loose prism: 16^ BU OS CASE #1 • Plan: - Rx given for SVD to purchase glasses in the community - Will apply 15^BU OS when he gets his glasses • 1-week later Bedside -Applied 15^ Fresnel BU OS -VA OU: 20/20-1 (-)diplopia -NVA cc: OD: 20/32 OS: 20/32 OU: double -Prism bar with reading glasses: single with 14^ BU OS -Plan: Applied 15^ BU POP OS to reading glasses CASE #1

• 3 days later – examination in exam room • DVA cc: OD: 20/20-1 OD OS: 20/20-2 OU: diplopia w/o prism • NVA cc: OD: 20/40 OS: 20/25 OU: 20/25 (-)diplopia w/o prism (struggles with crowding) • Maddox Rod at distance w/o prism: Vertical: right hyper Horizontal: eso • Maddox Rod at distance w prism: Vertical: tr right hypo Horizontal: ortho CASE #1

• Maddox Rod at near w/o prism: Vertical: right hyper Horizontal: exo • Maddox Rod at near w prism: Vertical: right hypo Horizontal: exo • Single line text acuity with prism: 20/25, miscalls a few words initially closing OS but could read the same OU • Von Graeffe Phoria: Distance Vertical: 11BD OD sees single Distance Horizontal: 2BO OS sees single CASE #1 • Distance prism assessment: Loose Prism: 12^BD OD Fresnel: 13^BU OS • Near Prism assessment: with +2.50 OTC readers Prism bar in downgaze: 8^BD OD Loose prism: sees single with 8^BD OD Fresnel: prefers 9^BU OS for reading • Plan: Applied 10^ BU Fresnel to back side of OS and 3^ BU to front in SVD Applied 9^ BU Fresnel to back side of OS in SVN CASE #1

• 2 weeks later: 3^ Fresnel fell off the front of the lens, says the images are “slightly off”. Dizziness has improved • Distance acuities remain the same, slightly double at distance with 10^ Fresnel • Single line text acuity with prism: reads 1M (8pt) but miscalls words, tended to spell words out first. Does best with 12pt 2/2 crowding • Repeated the prism eval process and final determination was to go back to the 15^ BU OS and keep the near he same. CASE #1 • Saw him every 2 weeks • No change in distance or near visual acuity • Repeated the process - Cover test and maddox rod distance and near with and without prism - Von Graeffe, prism bar, loose prism, fresnel - Reading acuity - Changed power of Fresnel based upon the above testing results • Switched prism to OD when beginning to show signs of suppression CASE #1

• After 6 weeks of no change in the magnitude of the deviation, rx given for Bifocals with 10^ split vertical prism and 8^ SVN with split vertical prism. • He is walking more now so advised to remove the bifocals while walking. • Followed him monthly and when the magnitude remained stable for 6 months, surgical consult was placed. • Continue with SVN prism glasses for extended reading, SVD with prism for walking and bifocals when seated CASE #1

• Prism Evaluation Distance: • Post strabismus follow-up: Prism Bar: 4^BD OD • Manifest Refraction: Loose Prism: 3^BD OD OD: +0.75+0.25X172 20/20-1 “Better” without any prism OS: +0.25+0.50X097 20/20 • Prism Evaluation Near: OU: 20/20-2 Sli vert overlap Prism Bar: 1-4^ BD OD “no difference, Add: +2.50 OD: 20/26 OS: 20/20 6^BI OD “better” OU: 20/16 Loose Prism: “No difference” with 2^BD OD and with 6^ BI OD CASE #1

• No distance glasses needed since he is happy with unaided visual acuity • Rx for SVN given without any prism • Recommended reading stand for reading since has diplopia and nystagmus in downgaze. • Would like to try vision therapy for high XO at near • Scheduled with BROS for vision therapy CASE #1

• Started telerehab with BROS – vision therapy to improve convergence at near as well as binocularity • He works so more convenient • He used the computerized Home Therapy System and the brock string • Goal is to be able to drive CASE #2

• 73 yo male referred to our clinic because of a complete right 2/2 CVA • Health/ocular history positive for Diabetes (A1C 8.1), hypertension, high cholesterol, recent CVA and prior Bell’s Palsy • Good visual acuity at distance and near • All other findings were normal • No neglect • Applied 15^ Base right sector prism to the back of the right lens in his glasses and referred him to BROS for training CASE #2

• Returned 3 months later. Unable to complete training 2/2 health issues. Experiencing dizziness so stopped using the prism until that resolved. Ready to start again. • Re-applied the prism and consult placed to BROS • Soon after, developed CN 3 palsy OD! • Prism evaluation results: he was able to see single with 15^ BD and 35^BI Fresnel prisms OD • Returned I one month reporting that the diplopia was worse with the glasses on than with them off CASE #2

• Distance von Graeffe: • He reports he can fuse at distance Initially diplopic with intermittent and near. fusion • No consistent prism acceptance Reports single vision with 17^BI OD with prism bar and loose prism. and 9^ BU OS • Prefers no prism vs. prism since he • Near von Graeffe: can fuse - Initially diplopic with intermittent • Returned 3 months later with fusion complete resolution of the palsy - Reports single vision with 20^BI OD • Unwilling to try sector prism again and 7^ BU OS because he is convinced it “caused” the double vision • . DECOMPENSATED PHORIA

oMore common at near. oMany people do well until they require a bifocal – the additional plus power will relax the eyes even more so now it can be a problem. oVertical deviations can also occur as we get older and no longer can compensate for vertical phorias. CASE #3

• 30 yo male was seen in the general eye clinic in 2018 complaining of decreased vision OS, intermittent diplopia distance and near and photophobia • Distance and near acuity were good • Intermittent XT at near • No Rx given • No additional testing concerning the diplopia • Referred to BROS for a tint eval • Tints ordered with no RX CASE #3

One year later, referred to us by the PNS clinic because he stated that he has issues with eye pressure and used his wife’s glaucoma drops which relieved his eye pain. CASE #3

• He is complaining of slight decrease in vision since last year, pain behind OS with migraines and that he wears reading glasses. No mention of diplopia. • Unaided distance and near visual acuity 20/20 OD, OS, OU with no refractive error found. • Cover test: XP at distance and near • Maddox Rod: • Vertical: OD Hyper • Horizontal: XO CASE #3

• Von Graefe Distance: Vertical: 3^ BU OS Horizontal: ortho • Von Graefe Near: Vertical 6^ BU OS Horizontal: 6XO • Patient noticed improvement with 3^ BU OS at distance and near CASE #3

• Intraocular pressure (Tonopen) OD: 13mmHg OS: 16mmHg DFE: Disc: C/D 0.40 OD, OS healthy rims

• Plan: 1. Rxd Plano with 3^ split vertical 2. Scheduled tint evaluation with BROS CASE #3

• 3-month follow-up • Only experiences diplopia with headaches • Wears clear and tinted prims glasses at all times • Performed Von Graeffe: same findings • Follow-up in one year CASE #4

• 71 yo male with history of right Bell’s Palsy X2, left CNVI palsy (microvascular) and subdural hematoma s/p left sided craniotomy after a fall. Also has glaucoma followed in the glaucoma clinic on latanaprost. Complaining of photophobia and diplopia • Referred to us to manage the diplopia. CASE #4

He presented to us stating that he no longer experiences diplopia in primary gaze – only when he looks to the left which is a challenge while driving. He has to turn his head. He currently uses Rx reading glasses only. CASE #4 • Unaided distance visual acuity: OD: 20/25-1 OS: 20/25-2 OU: 20/20-2 (-) Diplopia • Unaided near visual acuity: OD: 20/50 OS: 20/32 OU: 20/40 (-) Diplopia • EOMs: Diplopia in left gaze. OS Abduction deficit • Slight head tilt to right CASE #4

• Cover Test: Primary Gaze • Maddox Rod: Primary Gaze Distance: Ortho Vertical: ortho Near: XP Horiz: ortho • Cover Test Left Gaze: • Maddox Rod: Left Gaze Distance: OD hyperT Vertical: OD HyperT Near: XP Horiz: XP CASE #4

• Von Graefe Distance: Vertical: 2^BU OS Horizontal: ortho • Von Graefe Near: Vertical: ortho Horizontal: 2XO • Dynamic visual acuity: affected in left gaze only CASE #3 • Prism evaluation in left gaze Prism Bar: 10^BU OS neutralized vertical phoria but still horizontal diplopia Loose prism: 10^ BU OS neutralized vertical phoria but still horizontal diplopia Loose prism: saw single with 10^ BU OS and 1^ BO OS • Plan: Rxd Manifest Refraction with +2.25 add RTC – after receives glasses for Fresnel trial CASE #4

• Second visit 5 months later– received PALs, happy with vision. Still diplopia in left gaze. • Visual acuities are good at distance and near • All other testing results are similar EXCEPT: • Prism evaluation in left gaze Prism bar: no vertical component, single with 1^BO OS Loose prism: no vertical component, single with 1^ BO OS • Wife states that he has always had ahead tilt, even in is baby pictures. CASE #4

• Applied 1^ Fresnel prism to temporal aspect of OS lens • Rx for sunglasses given • Follow-up in one month • Returned in 1 month – (-)diplopia in left gaze, blurry when looks through prism, difficulty with glare • Acuities are good at distance and near. • EOMS: (-) diplopia in left gaze with prism, (+) diplopia in left gaze without prism • Plan Consult placed to Chadwick for clear glasses with 1^ BO sector prism lateral aspect of OS lens. If does well, will consider getting similar in tints or consider fitovers CASE #4 • Loves the new ground in prism • Doesn’t like to drive without the prism but has problems with glare and photophobia • Tint evaluation was performed – did well with NoIR 11 • Consult placed to Chadwick for same lenses/frame in NoIR 11 tint VISUAL FIELD LOSS VISUAL FIELD LOSS

• Homonymous hemianopia is the most common. • Can also have neglect, either by itself or in combination with hemianopia. • Several types of prism placement can be utilized to help the patient navigate more safely. • The type of prism selected is dependent upon whether neglect is present and the cognitive abilities of the patient. INTERVENTIONS FOR VISUAL FIELD DEFECTS IN PEOPLE WITH STROKE

• Pollock A, Hazelton C, Rowe F, Jonuscheit S, Kernohan A, Angilley J, Henderson C, Langhorne P, Campbell P • Cochran Review. 2019 • Searched for randomized trials in adults after stroke where the intervention was specifically targeted at improving the visual field defect or improving the ability of the participant to cope with the visual field loss.

• REVIEW

• Primary outcome: functional ability in activities of daily living • Secondary outcomes: functional ability in extended activities of daily living, reading ability, visual field measures, balance, falls, depression and anxiety, discharge destination or residence after stroke, quality of life and social isolation, visual scanning, adverse events and death. REVIEW

• Only found 20 studies that met the inclusion criteria • Only ten compared the effect of the intervention with a placebo, control or no treatment group and of those only eight had data that could be included in meta-analysis • Only two had data relating to the primary outcomes and only one had adverse outcomes INTERVENTIONS

• Restitutive: visual field training, contrast sensitivity training, fusional binocular training • Compensatory: (fast, simultaneous) eye movement training, training in visual search strategies, training eye movements for reading, use of eye blinks or color cues, training in activities of daily living INTERVENTIONS

• Substitutive: prisms, eye patches, adapted lighting, magnification, environmental modification • Assessment and screening : standardized visual assessment, screening and referral for visual assessment and intervention • Research question: Do interventions for visual field defects improve functional ability following stroke? SUBSTITUTIVE INTERVENTIONS

• Four studies were included • “There was low or very low-quality evidence that prisms may have an effect on ability to scan (look) for objects but may cause a range of minor adverse events (particularly headache) and may have no effect on other outcomes. (Only one study!) • Concluded that no further studies need to be performed addressing the use of prism MY TAKE • The review did not include studies that utilize multiple interventions, such as compensatory (scanning) and substitutive (prisms) so not a true rehab approach • There was minimal to no training in the use of the prisms – wore them 2 hours a day for 6 weeks. • The review did not differentiate between types of prism placement (Peli vs. sector) • The final statement? “Limitations with the evidence mean that we could not draw any conclusions about the benefits of assessment interventions.”

VISUAL FIELD LOSS WITHOUT NEGLECT

• There are several prism options for visual field loss without neglect: -Sector prism -Peli Prism • The first requires the patient to actively scan into the prism. • The Peli prism requires a level of cognition to understand how it works. SECTOR PRISM • Applied to half of the lens on the affected side, BO. • Can apply to temp and nasal side or temp only on affected side. • Does require that the patient scan into the prism. • This shifts the image so that they are aware something is there. • Very helpful for mobility. • Start with Fresnel and then can have them ground in. • 10^, 15^, 20^, 25^ SECTOR PRISMS FOR HEMIANOPIA TRAINING TO USE THE SECTOR PRISM

• THE PRISM WILL NOT BE SUCCESSFUL WITHOUT ADEQUATE TRAINING! • Training is done in our clinic by the BROS and or OT • Scanning training is augmented with the Dynavision/Bioness integrated therapy system (BITS) • Methods for Prism Placement for Hemianopic Visual Field Loss. Wilcox D. Chronister C. Savage M. Journal of Visual Impairment and Blindness. July-August 2016: 276-279 – Good article on training in the use of prisms. SCANNING TRAINING

Dynavision BITS CASE #5 • 53 yo male with severe TBI 2002 while active duty. Helicopter crash. Medically retired from military 2/2 vision loss. Referred to us by the Polytrauma Network Site clinic. • He had tried Peli Prism for visual field loss previously (several years prior) and was unsuccessful. • Drove for 12 years successfully, few minor accidents and he was found to not be at fault. • Saw an ophthalmologist a few years ago that said he should no longer drive .Had his license revoked. He lost his job because of it. Has been depressed since he lost his license. CASE #5 • Has been seen by BROS for a tint evaluation and for a Dynavision evaluation • He exhibited below passing scores especially inferior left but did demonstrate consistent scanning techniques CASE #5

• Distance visual acuity: • Refraction: OD: 20/25-2 OD: -0.25+0.75X005 20/20-2 OS: 20/20 OS: -0.25+0.50X093 20/20 OU: 20/20 OU: 20/20 • Near visual acuity: OD: 20/32 Add: +1.75 OD: 20/20- OS:20/20 OS: 20/20 • Confrontation Visual Fields: OU: 20/26 OD: Inf nasal constriction OS: Inf temporal constriction CASE #5 HUMPHREY CASE #5

• Rx given for Bifocals with MRx and +1.75 add. • RTC- when he gets new glasses to apply Fresnel sector prism • He has already spoken with the kinesiotherapist about a driving evaluation, but she prefers to wait until after he has shown success with the prism • Visual acuities at distance and near were 20/20 OD, OS and OU CASE #5

• Applied 15^ sector prism to back of lateral aspect of OS lens, following the field loss found upon tangent screen testing • Referred to BROS for Dynavision testing/therapy with the sector prism • RTC – 2 months CASE #5

• Returned in 2 months • Wearing sector prism at all times • Finds it very helpful but it is blurry when scans in to the fresnel • Would like to pursue ground in prism and drivers training with the kinesiotherapist • Consult placed to Chadwick for ground in sector prism CASE #5 CASE #5

• Loves the sector prism! • Wants to see if driving is an option but for emergency purposes • Finds the prism very helpful for mobility • Would like to have the same prism placed in his tints since now that he has become accustomed to it, misses it • Applied fresnel to his current tints and have submitted consult to Chadwick for ground in prism in his tints. CASE #5

• Unfortunately, he cannot receive a behind the wheel evaluation without a driver’s permit. • He will be receiving further evaluation with BROS on the Dynavision and the OT on the BITS while wearing the prism. • If he scores within normal ranges, we will submit this information to the Medical Board of the DPS to at least allow him to get a permit so he can get further evaluation with kinesiotherapist. PELI PRISM

• Uses the concept of physiological diplopia. • 40^ strip of prism placed BO in the superior and inferior portion of the lens on the affected side. • Shifts the image to the seeing side of the opposite eye so the patient sees a faint image. • Serves as an early warning system to alert the patient that something is there. • Since scanning is not required, theoretically could be used for neglect but really disconcerting so need to be able to understand the concept. PELI PRISM PELI CLIPS PELI FITOVERS STANDARD PELI OBLIQUE PELI NEGLECT • Since patients that have neglect are simply unaware that the world exists on the affected side, they will NOT scan towards the affected side in the early stages. • They will veer towards the remaining field when walking, only eat food on half the plate and read only half the page. • Teaching them to scan towards the affected side is the main focus of therapy. • Yoked prism can be a useful tool until they are able to scan. YOKED PRISM GOGGLES YOKED PRISMS

• In yoked prisms, both lenses have prism with the base toward the affected side. • This shifts everything several degrees towards the non- affected side so scanning is not required. • The BROS/OT works with the prism goggles during occupational and physical therapy to see if the patient functions better with them. • Our rotatable goggles are 8^ and 10^. • If they do function better, we will order glasses with ~5- 7^. • Once they begin to scan, we will switch to a sector prism. CASE #6

Neglect: yoked prisms USE OF YOKED PRISMS IN PATIENTS WITH ABI: A RETROSPECTIVE ANALYSIS

• Bansal S., Han E., Cuiffreda K. 2014 • Reviewed 60 patient records of patients with homonymous hemianopsia, homomymous quadranopsia, abnormal egocentric localization and visual neglect • Two-thirds of the sample population responded favorably to the yoked prism • The most favorable patient responses were increased awareness of their blind visual field and improved gait, mobility and balance. CASE #6

• 69 yo male s/p CVA 2 months prior. Hospitalized for 2 months. Did get PT and OT but no speech therapy. Complaining of blurry vision in his left eye. Significant aphasia. • Distance visual acuity (forced choice Lea symbols)cc OD: 5/20 (~20/80) OS: 5/10 (~20/40) Refraction: OD: -2.00DS 5/12.5 (~20/60) OS: -0.50+0.75X163 5/10 (20/40) OU: 5/8 (20/32) ADD: +2.50 2.4M OD, 1.9M OS, 1.2M OU CASE #6

• Tangent Screen: OD:Complete Left Hemianopia OS:Complete Left hemianopia • Plan: 1. Alert PCP for referral for speech/language therapy 2. Suspect neglect as well as hemianopia 3. Rxd SV Near for SLP 4. RTC – 3 months to consider prism CASE #6

• 3 months later: had a fall 2 weeks prior broke ribs. Did see SLP for 2 weeks but is now getting home health with OT and PT only. He now recognizes he is having difficulty seeing things on his left side and describes Charles Bonnet phenomena • Distance Visual Acuity: cc Snellen Chart OD: 20/30-1 OS: 20/30+1 OU: 20/30-1 CASE #6

• Text acuity: 20/32 continuous text • Tangent: No change • Plan: 1. Applied 10^ BO Fresnel to lateral aspect of OS lens 2. Alert BROS to train on use of prism CASE #6

• 2 months later: • No complaints with prism • Performed refraction and found mild Rx change – correctable to 20/20 OD, OS, OU • Placed order for ground in sector prism • Continue training with BROS CASE #6

• Returned one year later: • Has broken his sector prism glasses • Did not continue with training with BROS • Still bumping into things on his left side • Correctable to 20/20-1 OD, OS, OU • Had to be prompted to look to the left CASE #6

Plan: 1. He does not appear to be scanning into the prism 2. Schedule with BROS to see if he can use the prism

BROS: After meeting with the patient, determined that he is not able to remember to scan into the prism. Agrees that yoked prism may be more beneficial.

Consult placed for bifocal with 5^ Base left yoked prism CASE #6

• Recently saw patient • Severe dementia • Unable to measure visual acuities – could not respond even to Lea symbols • Completely unaware of surroundings • Wonderful wife – she states that he is still functioning well with his current yoked prisms. VISUAL FIELD CONSTRICTION RP/GLAUCOMA

• Can use the same concept as the sector prism but the prism is applied BO to the temporal aspect of both lenses. • Can also apply a sector prism BD in the inferior portion of the lens. • As in the sector prism, if the patient does well, the lenses can be ground in CHANNEL LENSES RP PATIENT GLASSES OTHER USES

Altitudinal defects AION Midline Shift

• Bilateral base down sector prism • Common after TBI to the inferior portion of the • Can have vertical or horizontal lenses can help with mobility shift • Base down yoked prism may be • Use small amounts (4^) of helpful for reading yoked prism with the base towards the affected side. PHYSICAL/POSTURAL LIMITATIONS

• Bedridden patients can use prism glasses to make it easier to watch TV. • Patients with a severe head droop can also benefit with prism to shift images down so that they can see them. QUESTIONS?

Sandra M. Fox, OD [email protected] 210-617-5300 X 18250 THANK YOU!!