The College of Optometrists

Palfi's checklist - direct ophthalmoscopy: glaucoma.

1)check anterior angle with a beam at 90degrees to head

Nazal shaddow test: 2mm shaddow gr 4; 3mm shadow gr 3; 4mm shaddow gr2; 5mm shaddow gr 1.

2)Macula stop. Bright. 10Ds. Px straight eye, check pupil for opacities, go closer slightly – check lens, px moves eyes in all directions.

3)Macula stop. Bright. Reduce power until get to optic disk. Careful focus for sharp details. Get close as poss: explain to px what you are doing and why. Balance ophthalmoscope with longest finger touching px temples.

4)Measure disk vertical/horizontal using Macula stop. (will vary with px Rx etc – but often 2.1 stops = aevrage size.)

5)Detail the cup Cd, and position using macula stop. Verify the ISNT rule with Macula stop (roll the light round the rim edge and check the cup is pretty central and there is no rim thinning. An average disk cup is <0.5 horizontal and <0.42 vertically. Cups get slowly bigger with age with normal retinal axon death (4000 – 12000 PA). But there are many normal variations. Cd is simply a shorthand for rim width.

6)So examine carefully the disk rim – all round- looking for focal notching, focal pallor, vessels flying over, bending under, small hemorrhages, excavations under the rim (pot cup).

7)Draw what you see, large picture better – unless artistically inclined. Pencil is okay.

8)Look at cup floor, normal is creamy color, visible lamina cribrosa is abnormal. Nazal part is often deepest. Check for flying vessels.

9)Change to medium stop, check outer disk rim margin for atrophy. (peripapilary atrophy). Note pigment often denotes non-active changes. PPA due to misalignment of retina, RP layer, choroid to disk edge. 75% px with progressive disk changes will have PPA and crescent shaped atrophy arround disk is 2x likely in POAG, BUT 4x likely in Normal tension G.

10)Stay with medium size stop and insert green filter. Sweep round the disk looking at the retinal nerve fiber layer, Sweep further and further from disk – go slowly: really look. RNFL is reflective for green and normal RNFL should seem bright, well focussed (keep longest finger touching px temple to keep steady), with long thin 'grains' streaming towards the disk. Easiest to see above and also below the disk (where RNFL is thickest). A focal disk problem will make the RNFL thin and show darker Ret Pig underneath, also will show retinal vessels better(as not covered by RNFL). Normal is brighter band streaming towards upper disk and another towards lower disk. Wedges, are darker lines within this RNFL, always associated with a disk defect. Diffuse RNFL defects (more common), thinner RNFL, vessels more visible, darker due to underlying RP absorbing the green light.

11) Look at disk again with the red free to check you have it understood okay.

Notes.

1) A 0.7 cup on a large disk may be normal – but 0.2 on a small cup may be abnormal. Cd's are very difficult to determine accurately with the direct, and refer to the disk rim (don't forget all your observations with the direct are only based on color differences). So it is the disk rim that must be searched for focal defects, such as notching (very significant), thinning (especially nazal – so that vessels are no longer intouch with nazal rim edge) Early rim thinning is often vert/inferior and so the cup ovals breaking the healthy cup's isnt rule. If ISNT rule is broken – be suspicious: how did disk get to this?

2)Cup asymmetry between the eyes is usually less than 0.2 – but bigger differences are some times due to disk size asymmetry – and be normal.

3)The axons of the RNFL are heaped thicker above/ below the disk - so seem brightest and grainiest there.(The axons are very red/free reflective) This is important - as in diffuse damage (due to thinning of the nerve fiber layer) there is less difference between superior/inferior RFL and nazal/centrocaecal RFL (where there are less nerve fibers to reflect).

4)The RFL is the layer of axons from the retinal ganglia that eventually go down the optic nerve to synapse at the LGB. It is known that these axons die back in relationship to disk hemorrhages and increased cupping and relate well to field plot defects.

5)When the axons die they reflect the green light much less and the darker RP layer shows through. RFL defects thus look like darker arching areas (if focal) or more typically - diffuse defects - which is less of the grainy striations, less reflective areas and more prominent retinal vessels. This is typically above or below the disk. It can look like the RFL in the nazal area (which has less axons anyway - thus showing the superior/inferior axon loss). If I am not sure – I compare with other eye.

6)Disks categorised as normal, difficult to categorize and glaucoma.

7)Difficult disks can be categorized better by looking at the RNFL for defects – which would appear associated to rim defects. A glaucomatous disk won't show field defects early on.

8)Classically, glaucoma is where you have two of three things,

high pressure,

field defects,

disk changes.

9)Nowadays, glaucoma is regarded when there is only one of these three things present.

10)Cup increases (now you know why I draw it every time) even with normal pressure is known as Normal tension glaucoma. (often have large disks, and can be younger)

11)Unchanging disks in high pressure: Ocular Hypertension and carry a 10% risk of progression.

12)Early loss is often vertical/ inferior parts of the disk – causing vertical ovaling of the cup, or a disk pit. Generally, departures from the isnt rule ring my bells and cause a shift to study RFL in greater detail.

13)Difficult disks can be categorized better by looking at the RFL for defects – which would appear associated to rim defects. A glaucomatous disk won't show field defects early on.

14)People at risk include those with diabetes (damages tiny vessels at disk – so increase risk), hypertension, migraines and other blood pressure instabilities such as low pressure at night, heart disease, those on steroids long term, high IOP( mean 15.5, 95% normals under 20.5) high myopes(>2.00ds), age increases risk(3.5 <75yo to 45y olds) as does race(Afro 2x the caucasian risks) and genetics(parent 2.8; siblings 3.7. Note Chinese have 6* risk of acute glaucoma). My last three glaucoma suspects all had 'normal' pressures and big disks, large disks are thought to be associated with lower pressure tolerance than small disks.

15)What does it all mean? I draw my findings; use macula stop to concentrate for focal defects ( I never-ever use my wide stop for anything); use my red free to see better detail and also study the retinal fiber layer (vital in uncertain cases). Don't take IOP as everything – it goes up and down normally – even by as much as 15 or more(glaucoma may be more to do with the interaction of IOP and blood pressure which may fall when asleep).

'Diastolic Perfusion Pressure' is diastolic BP minus IOP. If ever less that 30mmhg then 6x risk of Glaucoma than if over 50mmhg.

16)Don't take a perfect field as everything – there can be glaucoma long before it shows. Remember all the risk factors and see if they apply. Anything missing? Yes I still practice and practice – to some extent glaucoma is a disease of exclusion. In my PQE's I wondered if normal disks could hide glaucoma – yes they can! Glaucoma causes a changing disk – so if unsure monitor early.

I find my wide stop quite useful when doing motility. It gives good reflexes.

Wow palfi, you must certainly spend a fair bit of time looking at the disc to fit all that in!! I would certainly agree that careful disc examination is the key to accurate glaucoma screening.

Personally, I wouldn't advocate the use of the direct ophthalmoscope as the primary instrument to evaluate the optic disc, but, each to their own. For me volk lens examintion with either a 90D, 78D or 60D (whatever you prefer, a super 66 is particuarly good)is the preferred method for disc evaluation (and general routine fundoscopy).

Dilation of the pupils significantly improves disc evaluation. I've sometimes been surprised at how "different" a disc can appear following dilation.

Whatever method is employed the difficult part is of course correctly identifying whether disc cupping is physiological or pathological. In my mind dilated volk examination combined with visual field testing (where appropriate) is by far the best way to make this important decision.

Have to agree with you Hamy on use of indirect (78D best?). Even dilated, I now find direct assessment of the disk quite difficult. Can't beat the helping hand of stereo.

palfi:

I agree that I prefer to look at the disc with the 78D, but what a brillant review of what to look for. Even after having been in practice for a long time it igood to get back to the basics. I have printed out a copy of your post and stuck it up on the wall as a reminder. Thanks again

As i understand visible lamina cribrosa are not always abnormal (for eg small very round and defined lam crib) but lamina cribrosa which are not round (more oval with increase glaucoma, to slit like) or of different sizes should be treated with caution. I find that it is essential to do slit lamp of ant,seg and I do direct disc exam (occasionaly red-free exam helps define cupping and pallor easier)and then second look with volk if not happy. Fields is brilliant if you have a good fields screener, but of less value if you dont,

thanks for all your feed backs, I am obliged - palfo