Anisometropia and Associated Phoria

Man... its hard keeping up with all these updates. I think I'll just post the most interesting ones from now on.

Today was a followup exam with no clear instructions from the previous intern. Based on the file, it seemed like her IOPs were slightly high, but not abnormal. Her IOPs are being monitored, so I thought today is probably just an IOP check, to make sure they're normal.

But when the patient arrived, it seemed she was unhappy about her glasses, and said that she wanted to get her Rx rechecked and sorted out. She claimed to have had 0.5 BU OD slab-off lenses, and were very happy with them. However, when they updated her Rx with an add, they told her they can only make slab-offs starting at a minimum of 2pd.

I believe she was given the 2pd, and she said it was too strong and refunded the lenses.

So she's back today to get her Rx fixed.

Looking at her Rx, it was clear she was anisometropic. She complained of asthenopia and "pulling" at near while trying to read her recipes.

The best thing about partial/follow up exams is being able to tackle problems using problem specific testing strategies.

So I started off with VAs to see if she can see at near. Then CT/von grafe phoria/maddox to see if phorias are within limit.

Her lateral phorias were normal, but I ended up finding a 3BU OD on maddox rod at near which is what I expected for someone with anisometropia.

I go seek out my supervisor to tell him what I've found. He came and investigated her history again... apparently "pulling" meant there is a convergence problem! I was confused because her CT and von grafe values were normal... On further questioning from my supervisor, she tells us that she had never been able to cross her eyes :O... I guess I should've tested PFV and NFV as well.

So we break out the mallet box (yes, seriously) and test her ASSOCIATED PHORIA at near.

Recall: Px uses polarized glasses to look at the O X O target surrounded by texts to obtain fusion lock - but above and below the O X O target are nonius lines each seen by only one eye. In her case, she needed a 4BO to line up the nonius lines.

So, a patient who I thought is coming for an IOP checkup actually needed 3 BU OD. And on further testing also needed 4 BO.

We ended up prescribing 3 BU OD and 4 BO on top of her current Rx.

How on earth did she ever survive with just a 0.5 BU OD slab-off?

Day 6: Female, 5. (BV)

Amblyopia can be of two types

• Amblyopia of Arrest - VA have no potential to improve (if interaction VA = interaction-free VA)
  
• Amblyopia of Extinction - VAs can improve (if interaction VA <>

1. When a patient comes in, it is important to determine which one of the two they have because this will help us to decide whether we should treat or not. For those with Arrest, their VAs can no longer be improved by patching, unlike Extinction.

2. For those with Extinction, start treating by prescribing glasses/patching. Check patient progress regularly to see if VAs are improving. Patching should be done for 4 hours in a row and not split into 2 2h blocks. For patching to work, kids MUST engage in visually stimulating tasks - eating, playing, drawing, colouring, etc. while good eye is patched.

3. Checking for central/peripheral and deep/shallow suppression using Worth 4 dot

• Distance W4D checks for central suppression because the angular subtense of the lights on the retina is smaller, and is more central
• Near W4D checks for peripheral suppression because the angular subtense of the lights on the retina is larger, therefore more into the periphery
• W4D in photopic conditions unsuppress light suppressions
• W4D in scotopic conditions may unsuppress deep suppressions, because it is easier to see lights in the dark than in the light

ie. px sees 3 red dots in the dark at near
-> record as "deep/peripheral suppression OS"

Do anti-suppression therapy on someone with light suppressions. You don't want to break someone with deep suppression -> fusional problems and diplopia will result.

4. HTS is more affordable, gets better patient compliance, allows constant monitoring, and allows the practitioner to modify the program at any time.

5. Congenital eso vs. Accommodative eso

• congenital esos exist since birth, mothers usually realize that their kid has a turned eye very early on
• accommodative esos onset at about 18 months
• Always cycloplege, and fill the whole Rx.
  

Day 5: 1- Male, 74, 2- Female 62 (PC)

First px was relatively easy, pretty normal.

Completed in 2.5 hours


Second px can't speak English but had a translator.

1. Keep it simple, "can you see?" patient answers "yes" or "no"

2. Be careful not to show your thumb when you're doing VFs... px will answer "3"

3. We talk too much, and that eats into exam time

Day 4: 1 - Male, 57. 2 - Female, 40 (PC)

Things I learned today:

First px was relatively normal, nothing too unusual. Another hyperopic presbyope. Never filled in his previous script.

Things I learned:

1. With a solid record of healthy history, you can simply ask them if there was any change in medications or medical problems.

2. Think about the reason behind doing a test.

3. With a px's first pair of glasses, and with a heavy script, it may be prudent to drop off a quarter dioptor to make it easier for the px to adjust to wearing glasses.

====

Second px was a 40 year old female with no past record at the school. What could possibly go wrong?
"I see double sometimes and I have prisms in my glasses". Oh crap. I forgot how to determine base directions in lensometry, but other tests I've done suggests that the prisms were BO and BD

She was a poor and slow responder, her tear film made subjective very difficult. NFV at 6m: x/3/-2, Maddox rod of 2BD OD, Von Grafe 10 esophoria. Accommodation was starting to decrease. She also had psoriasis, but thankfully no uveitis. In the end we prescribed 6BO and 2BD OD according to Sheard criterion on top of her refraction. I didn't think a +1.00 add would negatively affect her esophoria so I just gave it to her.

Things I learned today:

1. Don't pinhole until after subjective

2. Do broad H closer so you don't have to move your arms as far

3. THINK ABOUT PROBLEM SPECIFIC TESTING

For someone with double vision, we should have been checking

• Von Grafe phorias
  
• PFV/NFV @ 6m, 0.4m
• +/- VVs
  
• W4D
• Comitancy

but we ran out of time.

4. Having 3 people in the room with the patient can be very stressing for the patient. I can feel that she was on the verge of breaking down after I was doing FFC fields.

5. Don't show the 6/4.5 line until they can read the 6/6 line. Otherwise they'll begin to feel discouraged.

6. Get a multiple pinhole - its been needed more than once now. Pxs have a difficult time finding that 1 small hole.

7. Change up the choices, use more than just 1 or 2, add 3 or 4, 5 or 6, 7 or 8. Some people may preferentially pick '2'.

8. You CAN have prisms in PALs, but its not done by decentering.

Day 3: Male, 58. Victoria School (PC)

58 year old male presents with reduced VAs distance and near. LEE was 13-14 years ago. He was a light hyperope then so he probably didn't need glasses 13-14 years ago, as he could just use his accommodation to see infinity. Now however, with the onset of presbyopia, his accommodation is gone and can no longer help him in focusing the image on his retina. His solution? Drug-store readers: a +1.00 pair for distance, a +2.00 pair for intermediate, and a +3.00 pair for reading.

In the end, we counseled him on PALs that can replace the 3 different pairs of reading glasses with just one pair. I hope he will invest in one.

length of exam: 2.5 hours

Things I learned today:

1. Measure optic disk size by placing the slit of light over the disk and then shrinking the slit until its vertical dimensions are the same as the disk. Then read the gauge above the filter settings, units are in mm.



2. Optic disk typing. It helps to categorize what shape each disk is, as some are harder to measure than others.



3. Parks 3 step tends to over-diagnose superior obliques. Longstanding deviations develop comitancy due to other muscles compensating for the paretic muscle (deviations will appear the same on left and right gaze) Think about replacing P3S with computerized Hess plots.

4. 4 ways to treat any BV problem:

• Do nothing
• Orthoptics
• Prisms
  
• Refer for surgery

5. S.T.A.R system glaucoma risk calculators weighing factors are horribly off

6. What is the pathophysiology behind hydrocephalus and sunset eyes?

7. Reminder: Pencil trick, if px talks too much, drop pencil and "as I was saying....". Don't let px hijack your exams. Px hijacks so far: 2

8. Keep a binder full of documents that you will either refer to constantly, or frequently show pxs.

9. BV pyramid (look into this some more)

• Stereopsis
• Sensory fusion
• Fusional reserves
• Accommodation
• EOM function
• VA

10. When ordering MRI imaging, ALWAYS request contrast on imaging. Techs inject a dye prior to running MRI to make things more visible.

11. Reminder: VA charts with numbers at the end ie.

F Z B D 4 = 20/40 = 6/12
O F L C 3 = 20 / 30 = 6/9

12. Smith's technique on ant. chamber depth

• slit and eyepieces at 60 degrees
• rotate slit to horizontal position
• illuminate the cornea, see the reflection of the light on the cornea and on the lens
  
• widen/shorten the slit length until the cornea bar touches the lens bar
• read gauge, apply conversion factor

13. If optometrists don't manage BV cases, then who will?

14. Pencil pushups do not work

15. Distributers for lenses for biomicroscopy often talk about magnification and field, but what does it really matter when a) the only field you see is the slit width and b) magnification can be toggled on the slit lamp? Get a lens you're comfortable holding in your hands that allows you room to move around and view periphery as well.

16. The only way you can see periphery in high mag is by doing biomicroscopy in various gazes, BIO will not give you such magnification.

17. When trying to neutralize a difficult cyl on ret, try pushing the collar all the way up. This will turn the cyl reflex into a "with" instead of "against", making it easier to neutralize the axis and power.

Day 2: Male, 72. (OH)

Spent the morning learning how to do pachs and run Goldmann and Humphrey VF machines, retinal fundus cam, and taking BPs. My CCT is ~570! Good to know in case I need LASIK in the future. 11 hours in clinic. Learned a lot today in terms of equipment, but still don't know how to interpret fields.

length of exam: ~3 hours

Hx:
- risk for glaucoma
- Raynaud's
- IOPs 15 OD, 16 OS
- large disk, loss in neural rim tissue
- BCVA OD: 6/6 OS: 6/12
- history of bv problems: left hyperdeviation -> exocyclodeviation, double vision at near hence prescribed glasses with near add in OD only. Blur in OS makes him suppress and avoid double vision.


1. Predilation workup

• VA
• Angles - get slit down as thin as possible, then move in from the side until you JUST see the shadow, then grade.
  
• Pressures - repeat for repeatability
  
• Pupils
  

2. Humphrey VFs:

• 30-2 central standard
• 10 minutes per eye
• very limited in accommodation for px with posture problems
• head posture and direction of gaze affects thresholds

3. HRT

• views nerve fiber layer thinning around the disc

4. Retinal fundus camera

• move in or out until crosshairs turn yellow
• zoom in via zoom in button
• align focus bars
• make sure eyes are wide and open
• take pic
  

5. Referral letter

• SOAP format

Day 1: Female, 67. (PC)

FIRST PATIENT EVER... AND ON MY BIRTHDAY

length of exam: ~4 hours

1. case history took too long, but revealed retinal trauma OD
2. refraction revealed BCVA OD: 6/12, OS: 6/6
3. OD lens capsule contained an epicapsular star
4. OU lens contained lens vacuoles, OD contained spoke cataract
5. OD contained peripheral retinal scars from childhood trauma
6. OU floaters
7. OD glaucomatous disk with cupping of 0.85
8. Angles ~1:1/4
9. Always trial frame the px after refraction