11The Second Ear and the Hard Cases

TWhy the first ear sets a hard benchmark

Unilateral implantation in adults produces a pooled health-utility gain of roughly +0.26 on the 0-to-1.0 death-to-perfect-health scale (recovering part of the ~-0.46 decrement of profound deafness), yielding a weighted-average cost of about $12,847 per QALY, among the most cost-effective surgical interventions known. Because the QALY denominator is calculated as life expectancy multiplied by utility gain, the first implant captures the steep early part of the utility curve, leaving any second device to compete against an already-restored baseline. Reported unilateral cost-utility ratios span roughly $9,000 to $31,177 per QALY depending on baseline deafness and study design, comfortably inside conventional willingness-to-pay thresholds of $20,000-$50,000 per QALY.[1996][1999][2009]

TThe incremental case for the second ear

Summerfield's scenario analysis framed bilateral implantation as an incremental question: the second device buys measurable gains in sound localisation and speech-in-noise, but its marginal utility is small because one working implant already delivers adequate everyday communication. Estimated incremental cost-effectiveness for the second ear runs from roughly $50,000 to over $150,000 per QALY, several-fold worse than the first ear and frequently above accepted thresholds. The ICER divides the net cost of the second device by its net QALY gain; because the numerator (a full second device, surgery, and maintenance) is large while the denominator (marginal binaural benefit) is small, the ratio rises sharply even when the clinical benefit is real.[2002][2006][2006]

CWhen the threshold rejects bilateral implantation

In the NICE TA166 appraisal, simultaneous bilateral implantation in children fell outside routine cost-effectiveness, with incremental ratios exceeding the GBP 20,000-30,000 per QALY threshold and evidence judged insufficient to justify funding a second device for every recipient. TA166 reserved bilateral implantation for defined groups (notably children, and adults who are blind or otherwise reliant on spatial hearing), reflecting that the binaural benefit is most valuable, and most economically defensible, where localisation matters most. Bilateral implantation in congenitally deaf children improves minimum-audible-angle localisation and listening in complex acoustic environments, yet these functional gains have not consistently met the GBP 20,000-30,000 per QALY bar on their own.[2009][2006][2006]

CSingle-sided deafness and the elderly recipient

Implantation for single-sided deafness shows favourable cost-utility of roughly $20,000-$40,000 per QALY, because restoring a silent ear delivers a substantial first-ear-like jump in spatial awareness and binaural cues rather than a marginal increment. In recipients aged 65 and above, cochlear implantation stays cost-effective at about $25,000-$50,000 per QALY, and older age at implantation does not substantially raise the cost per unit of health benefit despite shorter remaining life expectancy. Predictive modelling in elderly candidates supports good audiological and quality-of-life outcomes, so the shorter QALY horizon is offset by large per-year utility gains, making the elderly recipient an economically sound rather than a marginal case.[2005][2022][2009]