The optometry student’s brain is a funny thing. Sometimes, I only need to hear something once, and it is ingrained in me forever. More often than not, however, I find myself sheepishly looking over my shoulder during the middle of lecture as I punch the same things into Google over and over again. The professor mentions the word “aneseikonia,” and I find myself wondering if that was the thing about pupil sizes, or image sizes, while also wondering how in the world anyone could have let me into optometry school. Never fear: we all have our silly hang-ups! I’m taking a stand, here and now, to clear mine up once and for all.
All of those A’s: Aniseikonia, anisometropia, anisocoria, aniridia
Aniseikonia: difference in perceived image size between the eyes
Anisocoria: difference in pupil size
Anisometropia: significant difference between the refractive errors of the two eyes
Aniridia: absence of an iris
P’s of the ocular surface: Pterygium, Pinguecula, Phylctenule, Pannus
For these ones, I feel like I know about all of them, but sometimes I forget which one is which. So I’ve included some quick descriptions and memory cues to tip you off before I get into more detail!
The short version: wedge of tissue extending from the conjunctiva onto the cornea.
Memory aid: “ptero” = wing (think: PTEROdactyls) à wing shaped lesion.
More information: A pterygium is a triangularly-shaped wedge of fibrovascular tissue that extends from the bulbar conjunctiva onto the cornea. The apex (i.e., point) of the triangular wedge points towards the cornea. A pterygium is often preceded by a pinguecula, and is thus linked to similar risk factors: namely, exposure to UV light, wind, and dust. The patient will usually not report any symptoms, although sometimes cosmetic reasons bring the patient into the office. Other times, the patient may report blurry vision or irritation. Objectively, the wing-shaped fibrovascular tissue should be easily seen with the naked eye. Sometimes, an iron deposit can be seen at the leading edge of the pterygium (i.e., Stocker’s line). Over time, the pterygium may become more irritated or may become inflamed. In the event of progression over the pupillary axis, the pterygium may induce irregular astigmatism and corneal distortion. These effects, along with the ocular irritation, may warrant surgical intervention.
The short version: a yellowish thickening on top of the conjunctiva.
Memory aid: sounds kind of like something to do with penguins. Penguins live in the snow. Snow is white. Pingueculas happen on top of the white of the eye. Convoluted and borrowed from a classmate, but it works!
More information: A pinguecula is found on the conjunctiva, usually adjacent to the interpalpebral limbus. The lesion occurs as a result of collagen deposition on the conjunctiva. This causes a yellow thickening in the area affected. Usually the cause is UV light or dry eye. Most often, there are no symptoms associated with a pinguecula. Like a pterygium, a pinguecula can become inflamed. In the case of inflammation, a foreign body sensation and redness may be reported.
Phlyctenule (aka phylctenulosis, phlyctenular keratoconjunctivitis):
The short version: a small white nodule located on the conjunctiva or cornea.
Memory aid: Kind of sounds like Flick-tenule, and kind of looks like you could flick it off the eye.
More information: A phlyctenule is found on the conjunctiva, limbus, or cornea. Inflammation of the affected tissue forms a small, circumscribed lesion. This inflammation is caused by a non-specific allergic hypersensitivity response to an antigen. There are many possible antigens, with the most common being Staphylococcus and tuberculosis. The appearance of the lesion will vary slightly depending on its location. If on the conjunctiva, it will usually be near the limbus. It will look small, raised, nodular, and pinkish-white in color. It may be surrounded by dilated blood vessels. In the case of a corneal lesion, it will start out on the limbus as a white nodule surrounded by radiating blood vessels. As the white nodule migrates onto the cornea, it leaves a triangular trail of vascularized pannus in its wake.
The symptoms reported by the patient will vary slightly depending on the location of the phlyctenule. If the lesion is on the conjunctiva, the patient may report a foreign body sensation, irritation, redness, itching, discharge, tearing, and/or a history of phlyctenules (or similar symptoms). If the lesion is on the cornea, the patient may experience any of those symptoms, as well as pain, light sensitivity, ciliary spasm, and blurry vision.
The short version: vascular/fibrotic network on the cornea.
Memory aid: This is really a stretch, but pannus kind of/maybe/sort of rhymes with “venous,” so it helps me remember that it has to do with vascularization.
More information: Pannus occurs on the cornea, often secondary to a corneal phlyctenule. Pannus refers to a superficial vascular invasion, in the form of a fibrous tissue bed. This process usually occurs in response to a chronic inflammatory response. Causes include: rosacea, Staphylococcal hypersensitivity, phlyctenule, Chlamydia, superior limbic keratoconjunctivitis, contact lens over-wear or poor fit, vernal keratoconjunctivits, allergic keratoconjunctivitis, Herpes simplex, chemical burns, and trauma.
Corneal ulcer, corneal infiltrate
I always mix these two up because “infiltrate” sounds way scarier to me than “ulcer,” and yet ulcers are the ones that require the most aggressive treatment. When we learned this for class, we made a chart together and that helped a lot. Beyond that, one of the most helpful things for me in differentiating these two is finding all of the terms that mean the same thing. Below is a chart that includes information about sterile infiltrates and ulcers caused by bacteria. Ulcers can be caused by other microorganisms as well.
|Other names||Infectious corneal ulcer, microbial keratitis||CLPU, corneal infiltrate, CIE, hypersensitivity keratitis, immune keratitis, marginal ulcer, sterile ulcer|
|Cause||Bacteria* (usually gram-negative, such as Pseudomonas)||Hypersensitivity/antigen-antibody reaction/hypoxia|
|Risk factors||Mostly contact-lens related (EW, bathing/swimming with CLs), poor tear film, Staph bleph , smoking||Seen with chronic or acute conjunctivitis**, CL wearers, etc|
|Depth of Corneal Infiltration||Stroma, with surrounding edema||Overlying epithelium usually intact (if not, the epi defect is smaller than the infiltrate)|
|Subjective/Objective||Blur, light sensitivity, pain, redness, lid and conj swelling, purulent discharge, hyperemia, NaFl staining, corneal edema , AC reaction, hypopyon||Pain, tearing, light sensitivity, FB sensation, conjunctival injection, staining with NaFl|
|Pain level||Usually severe||More mild/moderate|
|Lesion location||Often central (but can be peripheral)||Often peripheral (but can be more central)|
|Lesion size||Usually larger||Usually smaller|
|# of lesions||Usually just one||One or more|
|Tears||Debris present||No debris|
|Staining||Positive staining||Positive or negative|
|Conjunctiva||Diffuse injection||Sectoral injection|
|Lids||Edema||No lid involvement|
|Discharge||Mucopurulent||None or slight (depending on underlying etiology)|
*Microbial keratitis can be caused by fungi or Acanthamoeba as well. These ulcers may present with different underlying causes and look different than a bacterial ulcer.
**An important thing to note is that a “sterile” infiltrate can be caused due to hypersensitivity to bacterial exotoxins. So, while the actual corneal defect is not occurring as a result of bacterial infiltration, there can be bacterial involvement.
Follicles and papillae are elevations on the palpebral conjunctiva of the eyelids. As seen in the chart below, these bumps can be associated with many different conditions. Being able to deferentially diagnose between follicles and papillae can go a long way in narrowing down your differentials.
|Etiology||Lymphoid hyperplasia||Allergic response|
|Causes||Viral disease*, Chlamydia (trachoma, conjunctivitis), cat-scratch disease (Parinaud’s), toxic drug reactions||Allergies**, Chlamydia (trachoma, conjunctivitis), bacterial conjunctivitis|
|Composition||Plasma cells, lymphocytes||Blood vessel center surrounded by edema/inflammatory cells under the epithelium|
|Size||Generally smaller than papillae||Generally larger than follicles|
|Location||Often the lower lid (think “FALL-icles fall to lower lid”)||Often the upper lid|
|Blood vessels||Avascular, but vessels may wrap around them||Blood vessel tuft in center|
|Appearance||Yellowish or gray/white, with surrounding blood vessels||Red center|
*E.g., adenoviral conjunctivitis, pharyngoconjunctival fever (PCF), epidemic keratoconjunctivitis (EKC), herpes simplex infection, molluscum contagiosum, pediculosis/lice
**E.g., seasonal and perennial allergic conjunctivitis, allergic keratoconjunctivitis, atopic keratoconjunctivitis, giant papillary conjunctivitis (GPC), vernal keratoconjunctivitis (with cobblestone papillae), chronic contact lens reaction, chronic blepharitis
If you find follicles, a good next step is to palpate the pre-auricular lymph node. If it is palpable, look for signs of herpes simplex (such as dendrites, conjunctivitis, skin vesicles). If herpes simplex is not suspected based on your exam findings, suspect Chlamydia. If the pre-auricular lymph node is not palpable, suspect toxic conjunctivitis, molluscum contagiosum, or pediculosis.
If you find papillae, look for discharge. If the discharge is watery, this suggests an allergic etiology. If it is purulent, suspect a bacterial cause.
Now that I’ve aired my dirty laundry, what are some of your more common hang-ups? Post in the comments section below!