How often are spectacles prescribed to “normal” preschool children?☆

Methods 

The Tennessee Lions Outreach Program uses the MTI photoscreener (Riviera Beach, FL) to evaluate children for amblyogenic factors. The process has been reported in detail elsewhere.4, 5, 6 Briefly, volunteers from local Lions Clubs photoscreen children in daycare centers, preschools, and mother's day out centers. The photographs are interpreted centrally (Vanderbilt Ophthalmic Imaging Center) using preestablished referral criteria, designed to have a low sensitivity, but high specificity (low false-positive rate).4, 6 Children are between the ages of 12 and 71 months (1 to 5 years). Children who are referred receive a list of ophthalmologists and optometrists in their area who are willing to perform an examination. The results of this examination are sent to the coordinating center. Results of each child's screening are incorporated into a specially designed database. For referred children, follow-up data, including visual acuity, cycloplegic refractive error data, and whether or not glasses were prescribed, are recorded.

We queried the database to identify referred children who did not have amblyogenic factors (see Table 1) found upon formal eye examination. These children, who were considered to have had false-positive screenings, had their examination data reviewed further. They were placed into two groups based upon their refractive error. Patients with essentially no refractive error (anisometropia ≤ 0.75D, hypermetropia ≤ +2.00D, myopia ≤ 0.75D, and astigmatism ≤ 0.75D) constituted the first category (Group A). A second group, consisting of children having refractive error too great to be in Group A but still less than factors determined to be amblyogenic (Table 1), were placed into a second category (Group B).

TABLE 1. %Criteria to fail eye examination

	1. Anisometropia (cylindrical or spherical) > 1.00 diopter (D)
	2. Any manifest strabismus
	3. Hyperopia > +3.50 in any meridian
	4. Myopia > −3.00 in any meridian
	5. Any media opacity > 1 mm
	6. Astigmatism: >1.5 D at 90 or 180
	>1.0 at oblique axis (more than 10 from 90 or 180)

Data were evaluated based on whether or not glasses were prescribed, the level of refractive error, and the training of the eye doctor performing the examination. In an attempt to separate examinations done by doctors who had more experience with children, we separated the results from doctors who had examined at least five children having false-positive examinations (“experienced doctors”) from those who saw fewer than five children with false-positive examinations. Our program currently has a Positive Predictive Value of 74%, so five false-positive examinations correspond to approximately 20 children being referred and examined. Statistical calculations were performed using Fisher's exact test, χ2, and paired t test, as appropriate. P < 0.05 was needed for statistical significance.

Results 

From the beginning of the program (June 1997) until April 30, 2003, 102,508 children were photoscreened. The dates of screening may seem remote but this provided 6 months for follow-up examinations to occur. Ninety-seven percent of the children completed the screening, and 4.7% were referred. Referred children were examined by local optometrists and ophthalmologists. During this period, the overall follow-up rate was 74.8%. Of the 3640 referred children who were examined, 890 (24.5%) had adequate follow-up examinations, but did not have any amblyogenic factors, nor any notation from the examining doctor about pathology. These children were considered to have had false-positive examinations.

Of the 890 false-positive examinations, 413 (46.4%) were performed by 186 optometrists; 205 (23.0%) were performed by 78 comprehensive ophthalmologists, and 272 (30.6%) were performed by 11 pediatric ophthalmologists (Table 2). A total of 275 doctors was involved. Four hundred ninety-five of these children (55.6%) were examined by doctors who performed at least five false-positive examinations (39 “experienced doctors,” typically 20 overall examinations). Of these doctors, 20 optometrists examined 147 children (29.7%); 12 comprehensive ophthalmologists examined 86 children (17.4%), and seven pediatric ophthalmologists examined 262 children (52.9%) (Table 2).

TABLE 2. %Summary data regarding false positive examinations

	Examination by	Number of Doctors	Number of Examinations	Fewer than 5 False-Positive Exams∗		5 or More False-Positive Exams
				Doctors	Exams	Doctors	Exams
	Optometrist	186	413(46.4%)	166	266(67.3%)	20	147(29.7%)
	Comprehensive Ophthalmologist	78	205(23.0%)	66	119(30.1%)	12	86(17.4%)
	Pediatric Ophthalmologist	11	272(30.6%)	4	10(2.5%)	7	262(52.9%)
	Total	275	890	236	395	39	495

∗ Most doctors saw only a few normal children.

One hundred seventy-four of the 890 children without amblyogenic factors were prescribed glasses (prescribing rate of 19.6%). The spherical equivalent refractive error for the prescribed spectacles is shown in Table 3. Of the 174 children prescribed glasses, 8 had myopia that was at least 1D but less than the 3D of myopia considered to be an amblyogenic factor. Thirty-two children were prescribed spectacles for a refractive error of <1D spherical equivalent refractive error, while 106 with hypermetropic refractive error spherical equivalent between 1.00 and 3.00D received glasses. Twenty-eight children who had refractive error ranging from +3.00 to +3.50D were prescribed spectacles. None of these children had strabismus or any other reported pathology.

TABLE 3. %Spherical equivalent refractive error for children without amblyogenic factors who were prescribed glasses

	Type of Doctor	Spherical Equivalent Refractive Error						Total
		Myopia		Hyperopia
		≥1D	0-<1D	0-1D	>1-2D	>2-3D	>3-3.50D
	Optometrist	4	4	19	44	49	25	145
	Comprehensive Ophthalmologist	3	2	6	4	7	2	24
	Pediatric Ophthalmologist	1	0	1	0	2	1	5
	Total	8	6	26	48	58	28	174

Optometrists prescribed spectacles more often than did pediatric ophthalmologists or comprehensive ophthalmologists (Table 4). Only 5 of 272 children (1.8%) who did not have amblyogenic factors and who were seen by pediatric ophthalmologists were prescribed spectacles, compared to 24/205 (11.7%) children examined by general ophthalmologists and 145/413 (35.1%) children seen by optometrists (χ2 = 62.8; P < 0.001).

TABLE 4. %Frequency of prescribing glasses in the absence of refractive or other pathology

	Type of Doctor	Number of Examinations	Glasses Given	Percentage
	Optometrist	413	145	35.1%
	Comprehensive Ophthalmologist	205	24	11.7%
	Pediatric Ophthalmologist	272	5	1.8%
	Total	890	174	19.6%

In an attempt to determine if doctors who were more familiar examining children had different prescribing requirements, we evaluated the prescribing behavior of the “experienced” doctors. These 39 represented only 14.2% of the 275 doctors who saw children for this project. They performed 495 of the 890 (55.6%) examinations, but prescribed only 66 of the 174 spectacles (38%), for a prescribing rate of 13.3%. This was compared to 108 prescriptions in 395 (27.3%) examinations done by less-experienced doctors (P < 0.02 for difference in prescribing frequency). However, this difference occurred because the experienced doctor group had a higher proportion of pediatric ophthalmologists. When level of training was included as a variable, however, there was no difference between the “experienced” and less-experienced doctors with respect to prescribing behavior: 36.1 vs. 34.6% for optometrists (P = NS); 10.5 vs. 12.6% for comprehensive ophthalmologists (P = NS); 1.5 vs. 10% (1/10) for pediatric ophthalmologists (P = NS). “Experienced” pediatric ophthalmologists prescribed spectacles for only four children without amblyogenic factors. The refractive errors and visual acuity for the four patients, who were prescribed spectacles by pediatric ophthalmologists in the absence of amblyogenic factors, are given in Table 5.

TABLE 5. %Refractive error of four patients prescribed spectacles by experienced pediatric ophthalmologists

	1. +2.00 + 1.50 × 90 O.U.
	2. OD: +3.50 sph; OS: +3.00 sph
	3. OD: +2.00 sph (VA 20/30); OS: +3.00 sph (VA 20/60)
	4. OD: −3.00 + 1.00 × 90; OS: −3.00 + 1.50 × 90

To determine if level of training impacted the refractive error at which spectacles were prescribed, we divided children into two groups (Table 6): those who had no significant refractive error (hypermetropia ≤ +2.00D, myopia ≤ 0.75D, astigmatism ≤ 0.75, or anisometropia ≤ 0.75D, Group A) and those who may have had some rationale for spectacles (Group B). We did this for both the “experienced” and the less-experienced doctors.

TABLE 6. %Spectacle data for children without amblyogenic factors who were given spectacles

	Type of Doctor	All Doctors			“Experienced” Doctors
		Group A (no refractive error)	Group B (minimal refractive error)	Total	Group A (53%) (no refractive error)∗∗	Group B (47%) (minimal refractive error)∗∗∗	Total
	Optometrist	36	109	145	15/83(18%)	38/64(59%)	53/147
	Comprehensive Ophthalmologist	6	18	24	1/43(2%)	8/43(19%)	9/86
	Pediatric Ophthalmologist	1	4	5	0/137(0%)	4/125(3%)	4/262
	Total	43	131	174	16/263(6.1%)	50/232(21.6%)	66/495

*See Results.

∗∗ P < 0.01. ∗∗∗ P < 0.001.

Overall, 43 of the 174 (24.7%) children who received a glasses prescription were in Group A. The percentage of children in Group A compared to the total number seen was similar for optometrists, ophthalmologists, and pediatric ophthalmologists. However, a bias could have been present if children with low refractive error were more likely to present to doctors of a certain type. The large number of doctors and relatively small number of patients seen per doctor made a global analysis of this impossible. However, we were able to evaluate this more robustly for the smaller group of 39 “experienced” doctors who performed 495 of the examinations (Table 6).

Of the 495 children who were examined by the experienced doctors, 263 (53.1%) had refractive error in Group A, while 232 (46.9%) had refractive error in Group B. Of the 263 children with essentially no refractive error (Group A), 6.1% received spectacles. The percentage of children in Group A who were prescribed glasses was greater if they had been seen by optometrists (18.1%) than if they had been seen by comprehensive (2.3%) or pediatric ophthalmologists (0%) (χ2 = 13.3; P < 0.01).

Of the 232 children in Group B (refractive errors not amblyogenic), 21.6% received spectacles. The percentage was again greater for children seen by optometrists (59.4%) than comprehensive (18.6%) or pediatric (3.2%) ophthalmologists (χ2 = 28.4; P < 0.001).

There was marked variability among individual providers in the frequency with which glasses were prescribed when only “experienced doctors” were considered (Groups A and B combined, Figure 1). For optometrists, the percentage ranged from 0% (0/5) to 80% (4/5), including one doctor who prescribed for 8 of 13 normal children. For comprehensive ophthalmologists, the percentage ranged from 0 to 40%. None of the seven pediatric ophthalmologists who had five or more false-positive examinations had a prescribing rate exceeding 3%.

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FIG 1. Results from examination of children found not to have amblyogenic factors or other pathology. Each point represents the frequency with which a given doctor prescribed spectacles. Only doctors who performed at least five examinations on children without amblyogenic factors are included (n = 39).

In an attempt to determine the overall cost to society for “unnecessary” spectacles, we assumed that 5,000,000 children are born (or enter kindergarten) each year, that spectacles cost a minimum of $150, that the baseline rate of spectacle dispensing for children without amblyogenic factors is 1.8% (5/272 seen by pediatric ophthalmologists), but that 19.6% (174/890) preschool children receive glasses when they are seen but do not have amblyogenic factors. Thus, 18% of normal children will receive unnecessary spectacles, at a cost to society of $135,000,000/year, if they receive a “typical” examination. If most examinations are performed primarily by optometrists and comprehensive ophthalmologists, the unnecessary spectacle rate could be as high as 27.3% (169/618), and the annual cost as much as $200,000,000 (0.273 × 5,000,000 × $150).

Discussion 

All methods of vision screening, including comprehensive eye examinations, have a sensitivity and a specificity to detect pathology. Increasing the sensitivity of any test results in an increase in the false-positive rate and a corresponding increase in referrals. Decreasing the referral rate to reduce overreferrals causes a decreased sensitivity as fewer abnormal children are referred. Preschool vision screening typically seeks to detect amblyopia and strabismus and high refractive error.

Most eye doctors are able to report anecdotal experiences of visually normal children who are wearing glasses, although they have no significant refractive error. The prevalence of this phenomenon is unknown. In this study, we attempted to determine how often glasses are prescribed for normal children. We found that nearly 20% of normal children receive a prescription for glasses following a visit to an eye doctor, despite not having an amblyogenic factor or other pathology. We also found that spectacles are often prescribed for children having <1D of refractive error and that spectacle-prescribing behavior, while varying widely among individual doctors, did not change for doctors seeing a high volume of children. This study also showed that pediatric ophthalmologists were much less likely to prescribe spectacles in such situations.

A surprising percentage of children (6.1%) received glasses for refractive error that would not be symptomatic in healthy preschool children (Group A) (Table 6).

There are four sets of guidelines available to assist the eye care practitioner in prescribing spectacles for preschool children. The American Academy of Ophthalmology's Preferred Practice Patterns for the comprehensive pediatric eye examination7 and the diagnosis and treatment of amblyopia8 lists guidelines for prescribing for refractive error in children up to age 4 years. For children aged 3 and under, they suggest prescribing spectacles for +4.50D or more of hypermetropia. The focal points module by Spencer is even more restrictive.9 Survey data from Miller and Harvey10 suggest that <25% of pediatric ophthalmologists prescribed spectacles for 4D of hypermetropia in children up to 4 years of age, while 25% prescribed for +3.00 to +3.50 in children aged 5 to 7 years. The recently released American Association for Pediatric Ophthalmology and Strabismus standards for detection of ocular pathology during preschool vision screening11 is the least stringent and suggests hypermetropia > +3.50 be detected by screening instruments. We applied the least stringent of these standards to our data to determine the impact of overreferral from preschool vision screening programs and found that up to 20% of children with refractive error less than this standard will receive spectacles. Optometrists and comprehensive ophthalmologists may be more likely to prescribe glasses, if they apply adult standards to children. We did not determine whether the presence of an optical dispensary in the doctor's office played a role in spectacle prescribing.

These data may overestimate the rate at which glasses are unnecessarily prescribed. Children referred from photoscreening are likely to have a higher refractive error than the general population, since the largest determinant in crescent size during photoscreening is refractive error. Our results showed that children with low refractive error were less likely to have glasses prescribed than were those with mild-to-moderate refractive error.

There may be other reasons for prescribing spectacles for children other than cycloplegic refractive error. The Preferred Pediatric Practice Pattern for the comprehensive pediatric eye examination suggests that, for children aged 4 years or older, glasses should be prescribed if “visual acuity can be improved or if the patient has asthenopia.”7 Asthenopia in otherwise healthy 2- to 4-year-old children is uncommon. There does not appear to be any reason children who saw optometrists or comprehensive ophthalmologists would have had a higher prevalence of asthenopia or decreased acuity than those who are seen by pediatric ophthalmologists.

It should be noted that all children in this study received cycloplegic refraction, as recommended by the American Academy of Ophthalmology Preferred Practice Pattern for the pediatric eye examination.7 Nearly all optometrists in our program now routinely perform cycloplegic refraction, in contrast to the recent report by Kemper et al,12 probably due to a large education commitment by this program for optometrists and ophthalmologists who see children.

Preschool vision screening is recommended by the American Academy of Pediatrics.13 Traditional vision screening is typical, but photoscreening is gaining acceptance.14 Recent legislation has shifted emphasis from recommending screening be done by pediatricians, family doctors, and lay personnel, who do not have a vested interest in the outcome of the screening, to having screening replaced with an examination by an eye doctor, who may serve to benefit from the result. The validity, sensitivity, and specificity of such an approach has never been studied. In addition, the cost effectiveness of such a mandate has never been proven. Nevertheless, legislation supporting mandatory preschool eye examinations has received widespread support, most recently from the Vision Council of America, which is the largest trade organization for optical manufacturers. Extrapolation of our results to the 5 million children who enter kindergarten each year demonstrates that such legislation would cost between $135 million and $200 million annually, simply for spectacles that are unnecessary as determined by the American Academy of Ophthalmology's Preferred Practice Pattern7, 8 and other guidelines regarding prescribing glasses for children.9, 10

Many preschool vision screening methods have been proposed. The prospective Vision in Preschoolers Study15 will be the largest such study to evaluate the efficacy of traditional vision screening techniques and new vision screening methodology. The outcome measures for such vision screening methods will include usability, sensitivity, specificity, and predictive value. Our results suggest that the costs related to unnecessary prescribing of spectacles should be considered when the financial impact of methods for detecting amblyopia is assessed.