Glaucoma billing loses money in three places. IOP testing is billed when it is already part of the exam, or not billed when serial tonometry qualifies. Imaging is bundled, repeated too often or left off the claim. Laser claims ignore the global period that follows them.
This guide walks through each of the three, shows the specific claims eye practices often miss, and explains the visit codes and modifiers that keep glaucoma claims paid.
Why Glaucoma Claims Are Easy to Miss
Glaucoma is a long-term condition. One patient may have three or four visits a year, imaging, visual fields and a laser or surgical procedure over time.
Every visit is a chance to skip a billable test or bill one that was bundled. Small errors repeat across hundreds of patients, so the revenue impact adds up quickly.
Diagnosis coding sits underneath every claim. Each test needs an H40 code with the right stage and laterality, explained in our guide to glaucoma ICD-10 codes.
Overlooked Glaucoma Claims at a Glance
Use this as a quick audit list. Each row is covered in detail below.
| Area | Common gap | How to catch it |
|---|---|---|
| IOP testing | Serial tonometry not billed | Flag diurnal curves |
| Screening | G0117 or G0118 skipped | Check high-risk status |
| Imaging | OCT and fundus photos paired | Pick one per eye, per day |
| Gonioscopy | Done but not charged | Add it to the charge slip |
| Laser | Global period ignored | Track 10-day globals |
| Second eye | Modifier 79 left off | Check open globals |
IOP Testing: Bundled or Billable?
IOP testing billing confuses many teams because pressure is measured at almost every glaucoma visit. Most of the time that reading is part of the exam, but some IOP services are separately billable and frequently go unbilled.
Not separately billable:
- A routine IOP reading taken during an eye exam or E/M visit.
- Repeat readings taken during the same exam to confirm a number.
- Pressure checks after a laser procedure, during its global period.
Separately billable:
- Serial tonometry (92100): multiple readings over an extended period on the same day, with an interpretation and report, such as a diurnal curve.
- Medicare glaucoma screening (G0117 or G0118) for high-risk patients, once every 12 months.
- Pressure-check visits outside a global period, which are billable visits; a technician-only check may qualify as 99211 when incident-to rules are met.
For serial tonometry billing, report 92100 once with one unit, whether one or both eyes are measured. The AAPC explains these serial tonometry rules, and some payers also limit how often it is paid.
Imaging and Visual Field Billing Errors
Imaging and field testing drive much of glaucoma revenue. These are the claims that most often go unpaid, get denied or never reach the claim at all.
OCT Billed Per Eye
Optic nerve OCT (92133) is billed once, with one unit, whether one or both eyes are scanned. Billing two units or adding RT and LT lines leads to denials or overpayments.
OCT and Fundus Photos on the Same Day
Posterior segment OCT and fundus photography (92250) usually cannot both be paid for the same eye on the same day. Choose the test that answers the clinical question. Our post on OCT and visual field billing lists the NCCI pairs that deny.
Visual Fields Left Out With OCT
Visual fields (92083) measure function, while OCT measures structure. Both can usually be billed on the same day when each is needed, yet some practices drop one, assuming it will deny.
Gonioscopy Left Off the Claim
Gonioscopy (92020) is a separate test, not part of the exam. It is often done at baseline and yearly, but never billed because no one records it as a charge.
Pachymetry Billed Every Year
Corneal thickness rarely changes, so many payers pay pachymetry (76514) only once for glaucoma management. Check your contractor’s rule before billing it again.
Two more problems cut across every test. Frequency must match severity, with fields often about yearly for stable disease and more often for advanced glaucoma. And each test needs a signed interpretation with findings and a plan, or it is not billable.
Laser and MIGS Claims Inside Global Periods
Laser and surgical glaucoma procedures carry global periods that decide which follow-up visits can be billed. Medicare’s global surgery booklet sets out the general rules.
Follow-Up Billed Inside the SLT Global
SLT (65855) has a 10-day global period. Routine pressure checks in those 10 days are included, and many payers limit how often SLT can be repeated on the same eye.
Second-Eye Laser Without Modifier 79
When the fellow eye is treated while the first eye is still in its global, the second procedure needs modifier 79 along with RT or LT. Without it, the claim looks like a duplicate.
Laser Iridotomy and Its Own Global
Iridotomy (66761) also carries a 10-day global. Each eye treated on a different day starts its own global period, which the follow-up schedule must reflect.
MIGS With Cataract Surgery
Drainage devices placed with cataract surgery are billed with 66991 (standard) or 66989 (complex), each with a 90-day global. Glaucoma care after MIGS is related to the surgery and usually included.
Glaucoma Visits During a Cataract Global
After cataract surgery without MIGS, a glaucoma visit is unrelated care and can be billed with modifier 24. Our guide to cataract co-management billing explains how postoperative care is split.
Sustained-release drug implants are billed with their own drug and procedure codes, and most payers require prior authorization before the procedure is scheduled.
Visit Codes, G2211 and Modifier 25
Glaucoma visits can be billed with eye codes (92012, 92014) or office E/M codes (99213, 99214). Choose the code set the documentation supports best, and apply it consistently.
Medicare’s G2211 add-on applies to ongoing care for a serious condition such as glaucoma, but only with office E/M codes. It cannot be billed with eye codes.
When an exam and SLT happen on the same day, the exam needs modifier 25 and must go beyond the usual pre-procedure check. The AAO explains common ophthalmology modifier rules.
When Glaucoma Billing Needs a Specialist Partner
Glaucoma billing and coding mixes testing frequency, global periods and payer authorizations that a small team rarely tracks consistently. Signs that outside help would pay off include:
- Denials on OCT, visual fields or serial tonometry.
- Gonioscopy or test interpretations missing from claims.
- Visits billed inside laser globals, or second-eye lasers denied.
- No report showing glaucoma testing by frequency and payer.
Practices searching for IOP billing services should confirm the vendor works in eye care, since the same phrase is widely used for behavioral health intensive outpatient programs.
Make Every Glaucoma Visit Count on the Claim
Most glaucoma revenue is lost quietly: a diurnal curve billed as a routine exam, a gonioscopy never charged, an OCT paired with fundus photos, or a laser follow-up billed inside its global.
Checking IOP testing, imaging and laser claims against these rules once a year usually finds the gaps. If you would like a second look, MBW RCM reviews glaucoma claims as part of its ophthalmology billing services.