Why Retina Groups Are Particularly Vulnerable to ROAS Misreporting

A multi-location retina group with three practices and a combined Google Ads spend of $18,000 per month receives a quarterly report showing platform ROAS of 7 to 1. The CFO is satisfied. The marketing director uses the figure to justify a budget increase. Nobody asks what fraction of the revenue attributed by Google’s model was generated by patients who arrived through referring-provider networks and searched the practice name only after the appointment was already effectively decided.

This is not a hypothetical. Retina practices get 70 to 90 percent of new patients from referrals. When a referred patient searches the practice name before calling to book, Google’s last-touch attribution records that brand search as a Google Ads conversion and assigns all of the associated revenue to paid search. The platform ROAS figure includes that revenue. The actual PPC contribution – the share of revenue from patients who would not have found the practice without the paid ad – is a fraction of what the ROAS figure implies. Google Ads ROAS in a referral-heavy specialty like retina will structurally overstate the platform’s contribution. This is not a measurement flaw in Google’s reporting. It is a feature of attribution design that every retina group should understand before treating platform ROAS as a budget-allocation input.

How ROAS and MER Measure Different Things

Platform ROAS, as reported in Google Ads, is a ratio: revenue attributed by Google’s attribution model divided by Google Ads spend in the same period. The attribution model – Data-Driven by default since 2026 – distributes conversion credit across touchpoints in the Google ecosystem based on observed conversion patterns. It does not have visibility into referral-network touchpoints, offline conversations, or any interaction outside Google. What it does see, and credit fully, is any Google-mediated touchpoint that preceded conversion, including brand searches from patients already in the appointment pipeline.

MER (Marketing Efficiency Ratio) is a different ratio: total practice revenue divided by total marketing spend across all channels. Total marketing spend includes Google Ads spend, agency fees, Meta spend if any, SEO vendor cost, and any other allocated marketing cost. Total practice revenue comes from the financial statements, not from any marketing platform. MER is attribution-agnostic by design – it asks a simpler question: for every dollar spent on all marketing combined, how many dollars of practice revenue exist? That simplicity forces a whole-business view that platform ROAS actively prevents.

The two metrics are not in conflict. Platform ROAS is useful for optimizing within Google Ads – it tells you which campaigns generate attributed conversion value efficiently within the platform. MER is useful for deciding how much to allocate to paid search at all and whether channel mix changes are improving total efficiency. Using ROAS to make portfolio decisions, which many retina practices do by default, is the wrong tool for the question being asked.

Benchmark Ranges for MER and ROAS in Eye Care

Ecommerce MER industry benchmarks run 3 to 1 through 5 to 1 as a healthy range, with anything below 2 to 1 triggering review. Healthcare MER benchmarks are less standardized. For multi-location eye care groups with mature accounts, 4 to 1 through 8 to 1 is a reasonable anchor range, with the higher end reflecting practices where SEO and referral channels carry significant revenue not attributed to paid advertising. Retina practices with strong referral networks and modest PPC budgets may show MER at or above the high end – a feature of the referral channel’s efficiency, not evidence that PPC is underperforming.

Google Ads ROAS for eye care accounts typically runs 1.5 to 3 times the MER figure because of attribution overcounting. A retina account showing platform ROAS of 8 to 1 alongside an MER of 4 to 1 is a normal spread. A spread larger than 3 to 1 warrants investigation: either the attribution model is overcounting at an unusual rate, or the practice is spending on channels outside Google that carry revenue without platform attribution. For the full benchmarks context, the Specialty Eye Care PPC Benchmarks Report covers the complete picture.

No retina-specific ROAS or MER benchmarks exist in public sources reviewed. Retina falls under the Ophthalmology category CVR of 18.29% (LocaliQ 2025) for consumer-facing campaigns, but the referral-revenue dynamic makes applying category ROAS benchmarks to a retina portfolio without adjustment misleading.

Red Flags That MER Is Being Ignored in Your Retina Group

Five patterns indicate a multi-location retina group is making budget decisions on the wrong metric.

First: the agency reports only platform ROAS, never MER. If every performance report shows Google Ads attributed revenue divided by Google Ads spend, and total practice revenue never appears alongside total marketing spend, the MER calculation has never been done.

Second: MER is described as “too complex to attribute” and therefore not reported. MER requires no attribution modeling. It requires two numbers from the financial statements. The complexity objection is an indication that the agency is not comfortable with a metric that puts their platform performance in a whole-business context.

Third: ROAS is reported without any explanation of the attribution model driving it. Data-Driven Attribution, Last Click, and linear models produce materially different ROAS figures for the same account. A ROAS number without an attribution label is not a defined metric.

Fourth: the CFO never receives a report connecting marketing spend to practice revenue. If the financial leadership of the retina group has no view into the relationship between total marketing investment and total revenue outcome, the marketing function is operating in a reporting silo that prevents strategic budget decisions.

Fifth: year-over-year MER trend is unavailable. Single-period MER is a snapshot. Trend is the signal. If the practice cannot compare MER this quarter against MER twelve months ago, the metric has never been institutionalized as a reporting standard.

How to Calculate and Report MER for a Multi-Location Retina Group

The calculation requires two inputs: total practice revenue for the period (from the P&L, not from any marketing platform) and total marketing spend for the same period (Google Ads spend plus agency fees plus any other paid media spend plus allocated SEO and tool costs). Divide revenue by spend. That ratio is MER for the period. It takes under 20 minutes per quarter once data sources are identified.

For multi-location groups, calculate MER at both the portfolio level and the individual-location level. Portfolio MER shows whole-group efficiency. Location-level MER reveals whether specific practices produce better or worse return on their allocated marketing spend – a direct input into location-level budget allocation decisions for PE-backed groups.

Report MER alongside platform ROAS in every CFO-facing report, with both figures labeled and the spread between them noted. When platform ROAS is 2.5 times MER or more, flag it with the referral-attribution explanation: referred patients who searched the brand name are being credited to Google Ads. That context prevents the figure from being misread as evidence of paid search performance alone.

Watch the MER-to-ROAS ratio over time. A growing spread indicates Google Ads attribution is capturing more referral-influenced conversions as a share of reported ROAS. A shrinking spread may indicate paid search generates a higher share of incremental conversions. The trend matters more than any single period. For the companion piece on the CPL side of this reporting gap, see Why Your CPL Dropped but Revenue Did Not and the Lead-Quality Blind Spot.

Our View on Metric Hierarchy for Retina Marketing Governance

Our view: the practices that govern marketing at MER level make better channel-allocation decisions than those governing at platform ROAS level. For retina, this principle is amplified by the referral channel’s dominance. A retina group that treats Google Ads ROAS as a portfolio metric will systematically over-invest in paid search relative to the actual incremental revenue it generates, because the ROAS figure includes referral-attributed conversions that would have happened regardless of the ad spend. MER forces an honest trade-off between paid search, SEO, and referral network investment – the three channels that collectively determine retina practice revenue. Platform ROAS measures only one of them, and measures it with attribution bias. For the complete benchmarking framework that contextualizes these metrics against specialty-specific ranges, see the Specialty Eye Care PPC Benchmarks Report.