Narrow Angles: Instruction sheet for Patients with REFERENCES

Sandra Lora Cremers, MD, FACS

NARROW ANGLES

The angle of the eye is located between the cornea (the clear window of the eye) and the iris (the colored part of the eye) where fluid (aqueous) inside of the eye drains out to the trabecular meshwork or “sink.” Some people are born with narrow angles (or drains); others develop narrow angle as the eye’s lens grows in circumference by adding rings like a tree. This increase in lens circumference can encroaches on an already limited anterior segment space in some patients. If left untreated, further narrowing of the angle can causes increases in eye pressure and increase the risk of Acute Angle Closure (AAC) or Closed Angle Glaucoma which can cause sudden pain and permanent vision loss. Narrow angle can also cause glaucoma in a slow process. Some cases of narrow angle do not need to be treated immediately but should be still be followed every 4-6 months. Be sure to check all medication inserts to look for precautions in patients with narrow angles. If you take medications that increase the risk of AAC or if you have any family history of glaucoma, talk to your eyeMD about being treated soon. For more information and references see https://drcremers.com.

[If you would like to know more about risk: Objective measures from the Pentacam have helped quantify risk: ACV=anterior chamber volume; ACD=anterior chamber depth; ACA=anterior chamber angle; Standard Gonioscopy is more subjective.

Normal (approx)	Narrow Angle	High risk AAC Sensitivity	High risk AAC Specificity
ACV >171mm³	≤113 mm³ =88% sensitivity, specificity significant narrow angles (Shaffer grade ≤1)	≤100 µl 93.3%	≤100 µl 100%.
ACD >3.15mm	<2.5 mm	≤2.1 86.7%	≤2.1 100%
ACA >34°	<34°	≤26° 73.3%	≤26° 88.2%

50% Risk of Angle Closure in next 6-12mo if: ACV≤100mm³, ACD≤2.1mm, ACA <26°(ref 5)

There are 3 options to main options to treat Narrow Angles:

1. Observation: if the narrow angle is minimal or is not causing any symptoms (occasional headache, brow ache, blurry vision), the angle can we watched periodically with gonioscopy (a contact lens with 4 mirrors). There, however, is a risk of sudden loss of vision and angle closure. Most eye surgeons recommend laser iridotomy or lens removal soon to avoid this uncertain risk. Either way, be sure to return for repeat gonioscopy and tell your eye surgeon of headaches, brow aches, or vision changes, especially in the evening or after dilation (after dilation starts to wear off.)

2. Laser Peripheral Iridotomy (LPI): a laser is used to make a microscopic hole in the iris to help open the angle. LPI helps prevent angle closure. It can also delay the need for lens removal if there is no significant cataract. The biggest risk of LPI is that the hole closes over time and needs to be reopened (<5%). The risk of transient intraocular pressure rise, persistent inflammation, hyphema, further cataract formation, endothelial cell loss, and scar formation is very low (<5%). LPIs should be done on both eyes but are usually not an emergency. It usually takes a few minutes per eye. Topical anesthetic drops numb the eye to help with discomfort. Steroid drops are given four times a day for 2-5 days after the procedure to help decrease inflammation. Rarely, the laser iridotomy is not enough and a different type of treatment is needed (iridoplasty, iridectomy or lens removal) if plateau iris is present (rare).

3. Lens removal: This offers the advantage of improving the patient’s uncorrected vision and preventing further maturation of the lens (developing a hard cataract). Lens removal or cataract surgery decreases the risk of angle closure essentially to zero. The lens never grows back. This procedure has its own risks which can be further discussed with your eye surgeon. Lens removal is the best way to remove the risk of angle closure in most patients if needed.

References:

1. Rossi GC, Scudeller L, Delfino A, Raimondi M, Pezzotta S, Maccarone M, Antoniazzi E, Pasinetti GM, Bianchi, PE. Pentacam sensitivity and specificity in detecting occludable angles.
Eur J Ophthalmol. 2012 Sep-Oct;22(5):701-8. doi: 10.5301/ejo.5000108.
2. Jain R, Grewal D, Grewal SP. Quantitative analysis of anterior chamber following peripheral laser iridotomy using Pentacam in eyes with primary angle closure. European journal of ophthalmology. May 14 2012:0.
3. Grewal DS, Brar GS, Jain R, Grewal SP. Comparison of Scheimpflug imaging and spectral domain anterior segment optical coherence tomography for detection of narrow anterior chamber angles. Eye (Lond). May 2011;25(5):603-611.
4. Rossi GC, Scudeller L, Delfino A, Raimondi M, Pezzotta S, Maccarone M, Antoniazzi E, Pasinetti GM, Bianchi PE. Pentacam sensitivity and specificity in detecting occludable angles.
Eur J Ophthalmol. 2012 Sep-Oct;22(5):701-8. doi: 10.5301/ejo.5000108.
5. Pakravan M, Sharifipour F, Yazdani S, Koohestani N, Yaseri M. Scheimpflug imaging criteria for identifying eyes at high risk of acute angle closure. J Ophthalmic Vis Res. 2012 Apr;7(2):111-7.
6. Narrow- and Open-Angle Measurements with Anterior-Segment Optical Coherence Tomography and Pentacam(TM). Mou, Dapeng; Fu, Jing; Li, Shuning; Wang, Lan; Wang, Xiaozhen; et al. Ophthalmic Surgery, Lasers and Imaging. (Nov/Dec 2010): 622-8.

Per Reference 5:
A volume <100mm3 or less, depth 2.1mm or less and angles <26 degrees has a 50% change of an acute angle closure attack in the next 6-12 months.

Most eyeMDs prefer not to wait till the angle gets this narrow as chronic narrow angle closure can cause permanent optic nerve fiber damage and permanent visual field loss. It is not worth the risk to wait till the odds are 50%.

From one of the authors: Dr. S.P.S. Grewal

The lens density module with its 360 global assessment is very helpful for preoperative cataract surgery planning,² and the Scheimpflug images are vital to assess the status of the posterior capsule in challenging cases like traumatic cataracts.³
We also extensively use the Pentacam in our glaucoma clinic for patients with suspected narrow angles. It offers a quick and objective way to screen for narrow angles and identify patients at risk of angle occlusion. The rotating camera allows the Pentacam to provide a measurement of the anterior chamber volume (ACV). We found that a cutoff of 113 mm³, powers ACV with 88% sensitivity and specificity in detecting narrow angles (Shaffer grade ≤1). It can then be used to objectively quantitate the ACV changes and confirm the adequacy of prophylactic laser peripheral iridotomy in these eyes.^4,5

The versatility of the Pentacam makes it an integral part of our refractive, corneal, cataract and glaucoma practices.”

¹Grewal DS, Brar GS, Jain R, Sood V, Singla M, Grewal SP. Corneal collagen crosslinking using riboflavin and ultraviolet-A light for keratoconus: one-year analysis using Scheimpflug imaging. Journal of cataract and refractive surgery. Mar 2009;35(3):425-432.
²Grewal DS, Brar GS, Grewal SP. Correlation of nuclear cataract lens density using Scheimpflug images with Lens Opacities Classification System III and visual function. Ophthalmology. Aug 2009;116(8):1436-1443.
³Grewal DS, Jain R, Brar GS, Grewal SP. Posterior capsule rupture following closed globe injury: Scheimpflug imaging, pathogenesis, and management. European journal of ophthalmology. May-Jun 2008;18(3):453-455.
⁴ Jain R, Grewal D, Grewal SP. Quantitative analysis of anterior chamber following peripheral laser iridotomy using Pentacam in eyes with primary angle closure. European journal of ophthalmology. May 14 2012:0.
⁵ Grewal DS, Brar GS, Jain R, Grewal SP. Comparison of Scheimpflug imaging and spectral domain anterior segment optical coherence tomography for detection of narrow anterior chamber angles. Eye (Lond). May 2011;25(5):603-611.

Dr. S.P.S. Grewal
MD, Ophthalmology, Gold Medalist
GREWAL EYE INSTITUTE, India